Hi Jon,
v2 Re-based and tagged for your merging pleasure!
This set converts the VFS overview documentation to RST format.
Patch set introduces no new warnings/errors to the html docs build
$ make htmldocs 2> ../docs-pre-vfs.stderr
Apply patch set ...
$ make cleandocs
$ make htmldocs 2> ../docs-post-vfs.stderr
$ diff ../docs-pre-vfs.stderr ../docs-post-vfs.stderr
Patch 1-4 - Whitespace fixes.
Patch 5 - Adds the document title adornments (above and below)
Patch 6 - Adds a SPDX license identifier
Patch 7 - Fixes some custom indentation at the top of the file that will
cause Sphinx to warn when we switch to .rst
Patch 8 - Converts custom list format to use RST formatted lists, this
is in preparation for switching to .rst
Patch 9 - Adds '.. code-block:: c' and fixes indentation of code
blocks. We rename the file to .rst in this patch (introducing
some new warnings).
Patch 10 - Adds back ticks to all the list items. This is in
preparation for fixing the indentation in the next patch.
This was found to help when reading both plain text and HTML.
Patch 11 - Cleans up the lists, indentation and missing periods. This
was kept separate to assist review. This patch is benign,
the less meticulous reviewer could safely skip over this one
quickly (this was the intention of separating these changes).
Patch 12 - Fixes a few minor grammar mistakes I notice while reading the
file, I'm taking bonus points for actually reading every word
of the file and not just trying to haphazardly do the
conversion like I have previously done :)
Patch 13 - Fixes two remaining Sphinx warnings.
If/when this goes in perhaps I, or someone else, will update the content
to document a newer kernel version.
thanks,
Tobin.
Changes since v1:
- Re-base onto commit 9834857754ff ("doc:it_IT: translations for documents in process/")
- Add 'Tested-by:' tag for Randy (thanks!)
Tobin C. Harding (13):
docs: filesystems: vfs: Remove space before tab
docs: filesystems: vfs: Use uniform space after period.
docs: filesystems: vfs: Use 72 character column width
docs: filesystems: vfs: Use uniform spacing around headings
docs: filesystems: vfs: Use correct initial heading
docs: filesystems: vfs: Use SPDX identifier
docs: filesystems: vfs: Fix pre-amble indentation
docs: filesystems: vfs: Use list character for lists
docs: filesystems: vfs: Add code-block and txt->RST
docs: filesystems: vfs: Use ticks for listed items
docs: filesystems: vfs: Clean up lists
docs: filesystems: vfs: Do minor grammar fixes
docs: filesystems: vfs: Use backticks to guard star
Documentation/filesystems/index.rst | 1 +
Documentation/filesystems/vfs.rst | 1283 +++++++++++++++++++++++++++
Documentation/filesystems/vfs.txt | 1264 --------------------------
3 files changed, 1284 insertions(+), 1264 deletions(-)
create mode 100644 Documentation/filesystems/vfs.rst
delete mode 100644 Documentation/filesystems/vfs.txt
--
2.21.0
Currently the file has a bunch of spaces before tabspaces. This is a
nuisance when patching the file because they show up whenever we touch
these lines. Let's just fix them all now in preparation for doing the
RST conversion.
Remove spaces before tabspaces.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 78 +++++++++++++++----------------
1 file changed, 39 insertions(+), 39 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 761c6fd24a53..637fd1756b89 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -136,7 +136,7 @@ struct file_system_type {
should be shut down
owner: for internal VFS use: you should initialize this to THIS_MODULE in
- most cases.
+ most cases.
next: for internal VFS use: you should initialize this to NULL
@@ -145,7 +145,7 @@ struct file_system_type {
The mount() method has the following arguments:
struct file_system_type *fs_type: describes the filesystem, partly initialized
- by the specific filesystem code
+ by the specific filesystem code
int flags: mount flags
@@ -182,12 +182,12 @@ and provides a fill_super() callback instead. The generic variants are:
mount_nodev: mount a filesystem that is not backed by a device
mount_single: mount a filesystem which shares the instance between
- all mounts
+ all mounts
A fill_super() callback implementation has the following arguments:
struct super_block *sb: the superblock structure. The callback
- must initialize this properly.
+ must initialize this properly.
void *data: arbitrary mount options, usually comes as an ASCII
string (see "Mount Options" section)
@@ -238,14 +238,14 @@ only called from a process context (i.e. not from an interrupt handler
or bottom half).
alloc_inode: this method is called by alloc_inode() to allocate memory
- for struct inode and initialize it. If this function is not
- defined, a simple 'struct inode' is allocated. Normally
- alloc_inode will be used to allocate a larger structure which
- contains a 'struct inode' embedded within it.
+ for struct inode and initialize it. If this function is not
+ defined, a simple 'struct inode' is allocated. Normally
+ alloc_inode will be used to allocate a larger structure which
+ contains a 'struct inode' embedded within it.
destroy_inode: this method is called by destroy_inode() to release
- resources allocated for struct inode. It is only required if
- ->alloc_inode was defined and simply undoes anything done by
+ resources allocated for struct inode. It is only required if
+ ->alloc_inode was defined and simply undoes anything done by
->alloc_inode.
dirty_inode: this method is called by the VFS to mark an inode dirty.
@@ -273,15 +273,15 @@ or bottom half).
(i.e. unmount). This is called with the superblock lock held
sync_fs: called when VFS is writing out all dirty data associated with
- a superblock. The second parameter indicates whether the method
+ a superblock. The second parameter indicates whether the method
should wait until the write out has been completed. Optional.
freeze_fs: called when VFS is locking a filesystem and
- forcing it into a consistent state. This method is currently
- used by the Logical Volume Manager (LVM).
+ forcing it into a consistent state. This method is currently
+ used by the Logical Volume Manager (LVM).
unfreeze_fs: called when VFS is unlocking a filesystem and making it writable
- again.
+ again.
statfs: called when the VFS needs to get filesystem statistics.
@@ -472,30 +472,30 @@ otherwise noted.
that.
permission: called by the VFS to check for access rights on a POSIX-like
- filesystem.
+ filesystem.
May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
- mode, the filesystem must check the permission without blocking or
+ mode, the filesystem must check the permission without blocking or
storing to the inode.
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
setattr: called by the VFS to set attributes for a file. This method
- is called by chmod(2) and related system calls.
+ is called by chmod(2) and related system calls.
getattr: called by the VFS to get attributes of a file. This method
- is called by stat(2) and related system calls.
+ is called by stat(2) and related system calls.
listxattr: called by the VFS to list all extended attributes for a
given file. This method is called by the listxattr(2) system call.
update_time: called by the VFS to update a specific time or the i_version of
- an inode. If this is not defined the VFS will update the inode itself
- and call mark_inode_dirty_sync.
+ an inode. If this is not defined the VFS will update the inode itself
+ and call mark_inode_dirty_sync.
atomic_open: called on the last component of an open. Using this optional
- method the filesystem can look up, possibly create and open the file in
+ method the filesystem can look up, possibly create and open the file in
one atomic operation. If it wants to leave actual opening to the
caller (e.g. if the file turned out to be a symlink, device, or just
something filesystem won't do atomic open for), it may signal this by
@@ -683,13 +683,13 @@ struct address_space_operations {
that all succeeds, ->readpage will be called again.
writepages: called by the VM to write out pages associated with the
- address_space object. If wbc->sync_mode is WBC_SYNC_ALL, then
- the writeback_control will specify a range of pages that must be
- written out. If it is WBC_SYNC_NONE, then a nr_to_write is given
+ address_space object. If wbc->sync_mode is WBC_SYNC_ALL, then
+ the writeback_control will specify a range of pages that must be
+ written out. If it is WBC_SYNC_NONE, then a nr_to_write is given
and that many pages should be written if possible.
If no ->writepages is given, then mpage_writepages is used
- instead. This will choose pages from the address space that are
- tagged as DIRTY and will pass them to ->writepage.
+ instead. This will choose pages from the address space that are
+ tagged as DIRTY and will pass them to ->writepage.
set_page_dirty: called by the VM to set a page dirty.
This is particularly needed if an address space attaches
@@ -700,11 +700,11 @@ struct address_space_operations {
PAGECACHE_TAG_DIRTY tag in the radix tree.
readpages: called by the VM to read pages associated with the address_space
- object. This is essentially just a vector version of
- readpage. Instead of just one page, several pages are
- requested.
+ object. This is essentially just a vector version of
+ readpage. Instead of just one page, several pages are
+ requested.
readpages is only used for read-ahead, so read errors are
- ignored. If anything goes wrong, feel free to give up.
+ ignored. If anything goes wrong, feel free to give up.
write_begin:
Called by the generic buffered write code to ask the filesystem to
@@ -741,12 +741,12 @@ struct address_space_operations {
that were able to be copied into pagecache.
bmap: called by the VFS to map a logical block offset within object to
- physical block number. This method is used by the FIBMAP
- ioctl and for working with swap-files. To be able to swap to
- a file, the file must have a stable mapping to a block
- device. The swap system does not go through the filesystem
- but instead uses bmap to find out where the blocks in the file
- are and uses those addresses directly.
+ physical block number. This method is used by the FIBMAP
+ ioctl and for working with swap-files. To be able to swap to
+ a file, the file must have a stable mapping to a block
+ device. The swap system does not go through the filesystem
+ but instead uses bmap to find out where the blocks in the file
+ are and uses those addresses directly.
invalidatepage: If a page has PagePrivate set, then invalidatepage
will be called when part or all of the page is to be removed
@@ -806,7 +806,7 @@ struct address_space_operations {
putback_page: Called by the VM when isolated page's migration fails.
launder_page: Called before freeing a page - it writes back the dirty page. To
- prevent redirtying the page, it is kept locked during the whole
+ prevent redirtying the page, it is kept locked during the whole
operation.
is_partially_uptodate: Called by the VM when reading a file through the
@@ -917,7 +917,7 @@ otherwise noted.
unlocked_ioctl: called by the ioctl(2) system call.
compat_ioctl: called by the ioctl(2) system call when 32 bit system calls
- are used on 64 bit kernels.
+ are used on 64 bit kernels.
mmap: called by the mmap(2) system call
@@ -942,7 +942,7 @@ otherwise noted.
(non-blocking) mode is enabled for a file
lock: called by the fcntl(2) system call for F_GETLK, F_SETLK, and F_SETLKW
- commands
+ commands
get_unmapped_area: called by the mmap(2) system call
--
2.21.0
In preparation for conversion to RST format use the kernels favoured
documentation column width. If we are going to do this we might as well
do it thoroughly. Just to the paragraphs (not the indented stuff), the
rest will be done during indentation fix up patch.
Use 72 character column width for all paragraph sections.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 198 +++++++++++++++---------------
1 file changed, 97 insertions(+), 101 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 2a610b9355e0..14839bc84d38 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -14,15 +14,14 @@
Introduction
============
-The Virtual File System (also known as the Virtual Filesystem Switch)
-is the software layer in the kernel that provides the filesystem
-interface to userspace programs. It also provides an abstraction
-within the kernel which allows different filesystem implementations to
-coexist.
+The Virtual File System (also known as the Virtual Filesystem Switch) is
+the software layer in the kernel that provides the filesystem interface
+to userspace programs. It also provides an abstraction within the
+kernel which allows different filesystem implementations to coexist.
-VFS system calls open(2), stat(2), read(2), write(2), chmod(2) and so
-on are called from a process context. Filesystem locking is described
-in the document Documentation/filesystems/Locking.
+VFS system calls open(2), stat(2), read(2), write(2), chmod(2) and so on
+are called from a process context. Filesystem locking is described in
+the document Documentation/filesystems/Locking.
Directory Entry Cache (dcache)
@@ -36,11 +35,10 @@ translate a pathname (filename) into a specific dentry. Dentries live
in RAM and are never saved to disc: they exist only for performance.
The dentry cache is meant to be a view into your entire filespace. As
-most computers cannot fit all dentries in the RAM at the same time,
-some bits of the cache are missing. In order to resolve your pathname
-into a dentry, the VFS may have to resort to creating dentries along
-the way, and then loading the inode. This is done by looking up the
-inode.
+most computers cannot fit all dentries in the RAM at the same time, some
+bits of the cache are missing. In order to resolve your pathname into a
+dentry, the VFS may have to resort to creating dentries along the way,
+and then loading the inode. This is done by looking up the inode.
The Inode Object
@@ -48,33 +46,32 @@ The Inode Object
An individual dentry usually has a pointer to an inode. Inodes are
filesystem objects such as regular files, directories, FIFOs and other
-beasts. They live either on the disc (for block device filesystems)
-or in the memory (for pseudo filesystems). Inodes that live on the
-disc are copied into the memory when required and changes to the inode
-are written back to disc. A single inode can be pointed to by multiple
+beasts. They live either on the disc (for block device filesystems) or
+in the memory (for pseudo filesystems). Inodes that live on the disc
+are copied into the memory when required and changes to the inode are
+written back to disc. A single inode can be pointed to by multiple
dentries (hard links, for example, do this).
To look up an inode requires that the VFS calls the lookup() method of
the parent directory inode. This method is installed by the specific
-filesystem implementation that the inode lives in. Once the VFS has
-the required dentry (and hence the inode), we can do all those boring
-things like open(2) the file, or stat(2) it to peek at the inode
-data. The stat(2) operation is fairly simple: once the VFS has the
-dentry, it peeks at the inode data and passes some of it back to
-userspace.
+filesystem implementation that the inode lives in. Once the VFS has the
+required dentry (and hence the inode), we can do all those boring things
+like open(2) the file, or stat(2) it to peek at the inode data. The
+stat(2) operation is fairly simple: once the VFS has the dentry, it
+peeks at the inode data and passes some of it back to userspace.
The File Object
---------------
Opening a file requires another operation: allocation of a file
-structure (this is the kernel-side implementation of file
-descriptors). The freshly allocated file structure is initialized with
-a pointer to the dentry and a set of file operation member functions.
-These are taken from the inode data. The open() file method is then
-called so the specific filesystem implementation can do its work. You
-can see that this is another switch performed by the VFS. The file
-structure is placed into the file descriptor table for the process.
+structure (this is the kernel-side implementation of file descriptors).
+The freshly allocated file structure is initialized with a pointer to
+the dentry and a set of file operation member functions. These are
+taken from the inode data. The open() file method is then called so the
+specific filesystem implementation can do its work. You can see that
+this is another switch performed by the VFS. The file structure is
+placed into the file descriptor table for the process.
Reading, writing and closing files (and other assorted VFS operations)
is done by using the userspace file descriptor to grab the appropriate
@@ -95,11 +92,12 @@ functions:
extern int unregister_filesystem(struct file_system_type *);
The passed struct file_system_type describes your filesystem. When a
-request is made to mount a filesystem onto a directory in your namespace,
-the VFS will call the appropriate mount() method for the specific
-filesystem. New vfsmount referring to the tree returned by ->mount()
-will be attached to the mountpoint, so that when pathname resolution
-reaches the mountpoint it will jump into the root of that vfsmount.
+request is made to mount a filesystem onto a directory in your
+namespace, the VFS will call the appropriate mount() method for the
+specific filesystem. New vfsmount referring to the tree returned by
+->mount() will be attached to the mountpoint, so that when pathname
+resolution reaches the mountpoint it will jump into the root of that
+vfsmount.
You can see all filesystems that are registered to the kernel in the
file /proc/filesystems.
@@ -158,21 +156,21 @@ The mount() method must return the root dentry of the tree requested by
caller. An active reference to its superblock must be grabbed and the
superblock must be locked. On failure it should return ERR_PTR(error).
-The arguments match those of mount(2) and their interpretation
-depends on filesystem type. E.g. for block filesystems, dev_name is
-interpreted as block device name, that device is opened and if it
-contains a suitable filesystem image the method creates and initializes
-struct super_block accordingly, returning its root dentry to caller.
+The arguments match those of mount(2) and their interpretation depends
+on filesystem type. E.g. for block filesystems, dev_name is interpreted
+as block device name, that device is opened and if it contains a
+suitable filesystem image the method creates and initializes struct
+super_block accordingly, returning its root dentry to caller.
->mount() may choose to return a subtree of existing filesystem - it
doesn't have to create a new one. The main result from the caller's
-point of view is a reference to dentry at the root of (sub)tree to
-be attached; creation of new superblock is a common side effect.
+point of view is a reference to dentry at the root of (sub)tree to be
+attached; creation of new superblock is a common side effect.
-The most interesting member of the superblock structure that the
-mount() method fills in is the "s_op" field. This is a pointer to
-a "struct super_operations" which describes the next level of the
-filesystem implementation.
+The most interesting member of the superblock structure that the mount()
+method fills in is the "s_op" field. This is a pointer to a "struct
+super_operations" which describes the next level of the filesystem
+implementation.
Usually, a filesystem uses one of the generic mount() implementations
and provides a fill_super() callback instead. The generic variants are:
@@ -319,16 +317,16 @@ or bottom half).
implementations will cause holdoff problems due to large scan batch
sizes.
-Whoever sets up the inode is responsible for filling in the "i_op" field. This
-is a pointer to a "struct inode_operations" which describes the methods that
-can be performed on individual inodes.
+Whoever sets up the inode is responsible for filling in the "i_op"
+field. This is a pointer to a "struct inode_operations" which describes
+the methods that can be performed on individual inodes.
struct xattr_handlers
---------------------
On filesystems that support extended attributes (xattrs), the s_xattr
-superblock field points to a NULL-terminated array of xattr handlers. Extended
-attributes are name:value pairs.
+superblock field points to a NULL-terminated array of xattr handlers.
+Extended attributes are name:value pairs.
name: Indicates that the handler matches attributes with the specified name
(such as "system.posix_acl_access"); the prefix field must be NULL.
@@ -348,9 +346,9 @@ attributes are name:value pairs.
attribute. This method is called by the the setxattr(2) and
removexattr(2) system calls.
-When none of the xattr handlers of a filesystem match the specified attribute
-name or when a filesystem doesn't support extended attributes, the various
-*xattr(2) system calls return -EOPNOTSUPP.
+When none of the xattr handlers of a filesystem match the specified
+attribute name or when a filesystem doesn't support extended attributes,
+the various *xattr(2) system calls return -EOPNOTSUPP.
The Inode Object
@@ -362,8 +360,8 @@ An inode object represents an object within the filesystem.
struct inode_operations
-----------------------
-This describes how the VFS can manipulate an inode in your
-filesystem. As of kernel 2.6.22, the following members are defined:
+This describes how the VFS can manipulate an inode in your filesystem.
+As of kernel 2.6.22, the following members are defined:
struct inode_operations {
int (*create) (struct inode *,struct dentry *, umode_t, bool);
@@ -513,42 +511,40 @@ The Address Space Object
========================
The address space object is used to group and manage pages in the page
-cache. It can be used to keep track of the pages in a file (or
-anything else) and also track the mapping of sections of the file into
-process address spaces.
+cache. It can be used to keep track of the pages in a file (or anything
+else) and also track the mapping of sections of the file into process
+address spaces.
There are a number of distinct yet related services that an
-address-space can provide. These include communicating memory
-pressure, page lookup by address, and keeping track of pages tagged as
-Dirty or Writeback.
+address-space can provide. These include communicating memory pressure,
+page lookup by address, and keeping track of pages tagged as Dirty or
+Writeback.
The first can be used independently to the others. The VM can try to
-either write dirty pages in order to clean them, or release clean
-pages in order to reuse them. To do this it can call the ->writepage
-method on dirty pages, and ->releasepage on clean pages with
-PagePrivate set. Clean pages without PagePrivate and with no external
-references will be released without notice being given to the
-address_space.
+either write dirty pages in order to clean them, or release clean pages
+in order to reuse them. To do this it can call the ->writepage method
+on dirty pages, and ->releasepage on clean pages with PagePrivate set.
+Clean pages without PagePrivate and with no external references will be
+released without notice being given to the address_space.
To achieve this functionality, pages need to be placed on an LRU with
-lru_cache_add and mark_page_active needs to be called whenever the
-page is used.
+lru_cache_add and mark_page_active needs to be called whenever the page
+is used.
Pages are normally kept in a radix tree index by ->index. This tree
-maintains information about the PG_Dirty and PG_Writeback status of
-each page, so that pages with either of these flags can be found
-quickly.
+maintains information about the PG_Dirty and PG_Writeback status of each
+page, so that pages with either of these flags can be found quickly.
The Dirty tag is primarily used by mpage_writepages - the default
->writepages method. It uses the tag to find dirty pages to call
->writepage on. If mpage_writepages is not used (i.e. the address
-provides its own ->writepages) , the PAGECACHE_TAG_DIRTY tag is
-almost unused. write_inode_now and sync_inode do use it (through
+provides its own ->writepages) , the PAGECACHE_TAG_DIRTY tag is almost
+unused. write_inode_now and sync_inode do use it (through
__sync_single_inode) to check if ->writepages has been successful in
writing out the whole address_space.
-The Writeback tag is used by filemap*wait* and sync_page* functions,
-via filemap_fdatawait_range, to wait for all writeback to complete.
+The Writeback tag is used by filemap*wait* and sync_page* functions, via
+filemap_fdatawait_range, to wait for all writeback to complete.
An address_space handler may attach extra information to a page,
typically using the 'private' field in the 'struct page'. If such
@@ -558,25 +554,24 @@ handler to deal with that data.
An address space acts as an intermediate between storage and
application. Data is read into the address space a whole page at a
-time, and provided to the application either by copying of the page,
-or by memory-mapping the page.
-Data is written into the address space by the application, and then
-written-back to storage typically in whole pages, however the
-address_space has finer control of write sizes.
+time, and provided to the application either by copying of the page, or
+by memory-mapping the page. Data is written into the address space by
+the application, and then written-back to storage typically in whole
+pages, however the address_space has finer control of write sizes.
The read process essentially only requires 'readpage'. The write
process is more complicated and uses write_begin/write_end or
-set_page_dirty to write data into the address_space, and writepage
-and writepages to writeback data to storage.
+set_page_dirty to write data into the address_space, and writepage and
+writepages to writeback data to storage.
Adding and removing pages to/from an address_space is protected by the
inode's i_mutex.
When data is written to a page, the PG_Dirty flag should be set. It
typically remains set until writepage asks for it to be written. This
-should clear PG_Dirty and set PG_Writeback. It can be actually
-written at any point after PG_Dirty is clear. Once it is known to be
-safe, PG_Writeback is cleared.
+should clear PG_Dirty and set PG_Writeback. It can be actually written
+at any point after PG_Dirty is clear. Once it is known to be safe,
+PG_Writeback is cleared.
Writeback makes use of a writeback_control structure to direct the
operations. This gives the the writepage and writepages operations some
@@ -605,9 +600,10 @@ file descriptors should get back an error is not possible.
Instead, the generic writeback error tracking infrastructure in the
kernel settles for reporting errors to fsync on all file descriptions
that were open at the time that the error occurred. In a situation with
-multiple writers, all of them will get back an error on a subsequent fsync,
-even if all of the writes done through that particular file descriptor
-succeeded (or even if there were no writes on that file descriptor at all).
+multiple writers, all of them will get back an error on a subsequent
+fsync, even if all of the writes done through that particular file
+descriptor succeeded (or even if there were no writes on that file
+descriptor at all).
Filesystems that wish to use this infrastructure should call
mapping_set_error to record the error in the address_space when it
@@ -619,8 +615,8 @@ point in the stream of errors emitted by the backing device(s).
struct address_space_operations
-------------------------------
-This describes how the VFS can manipulate mapping of a file to page cache in
-your filesystem. The following members are defined:
+This describes how the VFS can manipulate mapping of a file to page
+cache in your filesystem. The following members are defined:
struct address_space_operations {
int (*writepage)(struct page *page, struct writeback_control *wbc);
@@ -1227,8 +1223,8 @@ filesystems.
Showing options
---------------
-If a filesystem accepts mount options, it must define show_options()
-to show all the currently active options. The rules are:
+If a filesystem accepts mount options, it must define show_options() to
+show all the currently active options. The rules are:
- options MUST be shown which are not default or their values differ
from the default
@@ -1236,14 +1232,14 @@ to show all the currently active options. The rules are:
- options MAY be shown which are enabled by default or have their
default value
-Options used only internally between a mount helper and the kernel
-(such as file descriptors), or which only have an effect during the
-mounting (such as ones controlling the creation of a journal) are exempt
-from the above rules.
+Options used only internally between a mount helper and the kernel (such
+as file descriptors), or which only have an effect during the mounting
+(such as ones controlling the creation of a journal) are exempt from the
+above rules.
-The underlying reason for the above rules is to make sure, that a
-mount can be accurately replicated (e.g. umounting and mounting again)
-based on the information found in /proc/mounts.
+The underlying reason for the above rules is to make sure, that a mount
+can be accurately replicated (e.g. umounting and mounting again) based
+on the information found in /proc/mounts.
Resources
=========
--
2.21.0
Currently the licence is indicated via a custom string. We have SPDX
license identifiers now for this task.
Use SPDX license identifier matching current license string.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 790feccca5f4..5c8358c73e30 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: GPL-2.0
+
=========================================
Overview of the Linux Virtual File System
=========================================
@@ -9,8 +11,6 @@ Overview of the Linux Virtual File System
Copyright (C) 1999 Richard Gooch
Copyright (C) 2005 Pekka Enberg
- This file is released under the GPLv2.
-
Introduction
============
--
2.21.0
Currently file pre-amble contains custom indentation. RST is not going
to like this, lets left-align the text. Put the copyright notices in a
list in preparation for converting document to RST.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Any better ideas than using a list to hold the copyright lines?
Documentation/filesystems/vfs.txt | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 5c8358c73e30..43b18bafbc20 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -4,12 +4,12 @@
Overview of the Linux Virtual File System
=========================================
- Original author: Richard Gooch <[email protected]>
+Original author: Richard Gooch <[email protected]>
- Last updated on June 24, 2007.
+Last updated on June 24, 2007.
- Copyright (C) 1999 Richard Gooch
- Copyright (C) 2005 Pekka Enberg
+- Copyright (C) 1999 Richard Gooch
+- Copyright (C) 2005 Pekka Enberg
Introduction
--
2.21.0
Use code-block for C source code. With this in place we can rename the
.txt file to .rst. This introduces a few warnings that will be fixed
in proceeding patches.
Add '.. code-block:: c' to C source code snippets. Rename the file to
use rst file suffix.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
This ones a punish to review. It fixes up spacing around the struct
definitions. In hindsight this may not be what we want because now the
docs do not _exactly_ mirror the code. If this goes through update to
vfs.rst aims to patch the code first then update vfs.rst :)
Documentation/filesystems/index.rst | 1 +
.../filesystems/{vfs.txt => vfs.rst} | 321 +++++++++---------
2 files changed, 169 insertions(+), 153 deletions(-)
rename Documentation/filesystems/{vfs.txt => vfs.rst} (86%)
diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
index 1131c34d77f6..35644840a690 100644
--- a/Documentation/filesystems/index.rst
+++ b/Documentation/filesystems/index.rst
@@ -16,6 +16,7 @@ algorithms work.
.. toctree::
:maxdepth: 2
+ vfs
path-lookup.rst
api-summary
splice
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.rst
similarity index 86%
rename from Documentation/filesystems/vfs.txt
rename to Documentation/filesystems/vfs.rst
index 6e709815a6dd..dc2dd81f5e83 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.rst
@@ -87,6 +87,8 @@ Registering and Mounting a Filesystem
To register and unregister a filesystem, use the following API
functions:
+.. code-block:: c
+
#include <linux/fs.h>
extern int register_filesystem(struct file_system_type *);
@@ -110,18 +112,19 @@ struct file_system_type
This describes the filesystem. As of kernel 2.6.39, the following
members are defined:
-struct file_system_type {
- const char *name;
- int fs_flags;
- struct dentry *(*mount) (struct file_system_type *, int,
- const char *, void *);
- void (*kill_sb) (struct super_block *);
- struct module *owner;
- struct file_system_type * next;
- struct list_head fs_supers;
- struct lock_class_key s_lock_key;
- struct lock_class_key s_umount_key;
-};
+.. code-block:: c
+
+ struct file_system_type {
+ const char *name;
+ int fs_flags;
+ struct dentry *(*mount) (struct file_system_type *, int, const char *, void *);
+ void (*kill_sb) (struct super_block *);
+ struct module *owner;
+ struct file_system_type * next;
+ struct list_head fs_supers;
+ struct lock_class_key s_lock_key;
+ struct lock_class_key s_umount_key;
+ };
- name: the name of the filesystem type, such as "ext2", "iso9660",
"msdos" and so on
@@ -206,30 +209,31 @@ struct super_operations
This describes how the VFS can manipulate the superblock of your
filesystem. As of kernel 2.6.22, the following members are defined:
-struct super_operations {
- struct inode *(*alloc_inode)(struct super_block *sb);
- void (*destroy_inode)(struct inode *);
-
- void (*dirty_inode) (struct inode *, int flags);
- int (*write_inode) (struct inode *, int);
- void (*drop_inode) (struct inode *);
- void (*delete_inode) (struct inode *);
- void (*put_super) (struct super_block *);
- int (*sync_fs)(struct super_block *sb, int wait);
- int (*freeze_fs) (struct super_block *);
- int (*unfreeze_fs) (struct super_block *);
- int (*statfs) (struct dentry *, struct kstatfs *);
- int (*remount_fs) (struct super_block *, int *, char *);
- void (*clear_inode) (struct inode *);
- void (*umount_begin) (struct super_block *);
-
- int (*show_options)(struct seq_file *, struct dentry *);
-
- ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
- ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
- int (*nr_cached_objects)(struct super_block *);
- void (*free_cached_objects)(struct super_block *, int);
-};
+.. code-block:: c
+
+ struct super_operations {
+ struct inode *(*alloc_inode)(struct super_block *sb);
+ void (*destroy_inode)(struct inode *);
+ void (*dirty_inode) (struct inode *, int flags);
+ int (*write_inode) (struct inode *, int);
+ void (*drop_inode) (struct inode *);
+ void (*delete_inode) (struct inode *);
+ void (*put_super) (struct super_block *);
+ int (*sync_fs)(struct super_block *sb, int wait);
+ int (*freeze_fs) (struct super_block *);
+ int (*unfreeze_fs) (struct super_block *);
+ int (*statfs) (struct dentry *, struct kstatfs *);
+ int (*remount_fs) (struct super_block *, int *, char *);
+ void (*clear_inode) (struct inode *);
+ void (*umount_begin) (struct super_block *);
+
+ int (*show_options)(struct seq_file *, struct dentry *);
+
+ ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
+ ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
+ int (*nr_cached_objects)(struct super_block *);
+ void (*free_cached_objects)(struct super_block *, int);
+ };
All methods are called without any locks being held, unless otherwise
noted. This means that most methods can block safely. All methods are
@@ -365,30 +369,32 @@ struct inode_operations
This describes how the VFS can manipulate an inode in your filesystem.
As of kernel 2.6.22, the following members are defined:
-struct inode_operations {
- int (*create) (struct inode *,struct dentry *, umode_t, bool);
- struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
- int (*link) (struct dentry *,struct inode *,struct dentry *);
- int (*unlink) (struct inode *,struct dentry *);
- int (*symlink) (struct inode *,struct dentry *,const char *);
- int (*mkdir) (struct inode *,struct dentry *,umode_t);
- int (*rmdir) (struct inode *,struct dentry *);
- int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
- int (*rename) (struct inode *, struct dentry *,
- struct inode *, struct dentry *, unsigned int);
- int (*readlink) (struct dentry *, char __user *,int);
- const char *(*get_link) (struct dentry *, struct inode *,
- struct delayed_call *);
- int (*permission) (struct inode *, int);
- int (*get_acl)(struct inode *, int);
- int (*setattr) (struct dentry *, struct iattr *);
- int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
- ssize_t (*listxattr) (struct dentry *, char *, size_t);
- void (*update_time)(struct inode *, struct timespec *, int);
- int (*atomic_open)(struct inode *, struct dentry *, struct file *,
- unsigned open_flag, umode_t create_mode);
- int (*tmpfile) (struct inode *, struct dentry *, umode_t);
-};
+.. code-block:: c
+
+ struct inode_operations {
+ int (*create) (struct inode *,struct dentry *, umode_t, bool);
+ struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
+ int (*link) (struct dentry *,struct inode *,struct dentry *);
+ int (*unlink) (struct inode *,struct dentry *);
+ int (*symlink) (struct inode *,struct dentry *,const char *);
+ int (*mkdir) (struct inode *,struct dentry *,umode_t);
+ int (*rmdir) (struct inode *,struct dentry *);
+ int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
+ int (*rename) (struct inode *, struct dentry *,
+ struct inode *, struct dentry *, unsigned int);
+ int (*readlink) (struct dentry *, char __user *,int);
+ const char *(*get_link) (struct dentry *, struct inode *,
+ struct delayed_call *);
+ int (*permission) (struct inode *, int);
+ int (*get_acl)(struct inode *, int);
+ int (*setattr) (struct dentry *, struct iattr *);
+ int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
+ ssize_t (*listxattr) (struct dentry *, char *, size_t);
+ void (*update_time)(struct inode *, struct timespec *, int);
+ int (*atomic_open)(struct inode *, struct dentry *, struct file *,
+ unsigned open_flag, umode_t create_mode);
+ int (*tmpfile) (struct inode *, struct dentry *, umode_t);
+ };
Again, all methods are called without any locks being held, unless
otherwise noted.
@@ -624,39 +630,41 @@ struct address_space_operations
This describes how the VFS can manipulate mapping of a file to page
cache in your filesystem. The following members are defined:
-struct address_space_operations {
- int (*writepage)(struct page *page, struct writeback_control *wbc);
- int (*readpage)(struct file *, struct page *);
- int (*writepages)(struct address_space *, struct writeback_control *);
- int (*set_page_dirty)(struct page *page);
- int (*readpages)(struct file *filp, struct address_space *mapping,
- struct list_head *pages, unsigned nr_pages);
- int (*write_begin)(struct file *, struct address_space *mapping,
- loff_t pos, unsigned len, unsigned flags,
- struct page **pagep, void **fsdata);
- int (*write_end)(struct file *, struct address_space *mapping,
- loff_t pos, unsigned len, unsigned copied,
- struct page *page, void *fsdata);
- sector_t (*bmap)(struct address_space *, sector_t);
- void (*invalidatepage) (struct page *, unsigned int, unsigned int);
- int (*releasepage) (struct page *, int);
- void (*freepage)(struct page *);
- ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
- /* isolate a page for migration */
- bool (*isolate_page) (struct page *, isolate_mode_t);
- /* migrate the contents of a page to the specified target */
- int (*migratepage) (struct page *, struct page *);
- /* put migration-failed page back to right list */
- void (*putback_page) (struct page *);
- int (*launder_page) (struct page *);
-
- int (*is_partially_uptodate) (struct page *, unsigned long,
- unsigned long);
- void (*is_dirty_writeback) (struct page *, bool *, bool *);
- int (*error_remove_page) (struct mapping *mapping, struct page *page);
- int (*swap_activate)(struct file *);
- int (*swap_deactivate)(struct file *);
-};
+.. code-block:: c
+
+ struct address_space_operations {
+ int (*writepage)(struct page *page, struct writeback_control *wbc);
+ int (*readpage)(struct file *, struct page *);
+ int (*writepages)(struct address_space *, struct writeback_control *);
+ int (*set_page_dirty)(struct page *page);
+ int (*readpages)(struct file *filp, struct address_space *mapping,
+ struct list_head *pages, unsigned nr_pages);
+ int (*write_begin)(struct file *, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned flags,
+ struct page **pagep, void **fsdata);
+ int (*write_end)(struct file *, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata);
+ sector_t (*bmap)(struct address_space *, sector_t);
+ void (*invalidatepage) (struct page *, unsigned int, unsigned int);
+ int (*releasepage) (struct page *, int);
+ void (*freepage)(struct page *);
+ ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
+ /* isolate a page for migration */
+ bool (*isolate_page) (struct page *, isolate_mode_t);
+ /* migrate the contents of a page to the specified target */
+ int (*migratepage) (struct page *, struct page *);
+ /* put migration-failed page back to right list */
+ void (*putback_page) (struct page *);
+ int (*launder_page) (struct page *);
+
+ int (*is_partially_uptodate) (struct page *, unsigned long,
+ unsigned long);
+ void (*is_dirty_writeback) (struct page *, bool *, bool *);
+ int (*error_remove_page) (struct mapping *mapping, struct page *page);
+ int (*swap_activate)(struct file *);
+ int (*swap_deactivate)(struct file *);
+ };
- writepage: called by the VM to write a dirty page to backing store.
This may happen for data integrity reasons (i.e. 'sync'), or
@@ -852,45 +860,50 @@ struct file_operations
This describes how the VFS can manipulate an open file. As of kernel
4.18, the following members are defined:
-struct file_operations {
- struct module *owner;
- loff_t (*llseek) (struct file *, loff_t, int);
- ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
- ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
- ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
- ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
- int (*iopoll)(struct kiocb *kiocb, bool spin);
- int (*iterate) (struct file *, struct dir_context *);
- int (*iterate_shared) (struct file *, struct dir_context *);
- __poll_t (*poll) (struct file *, struct poll_table_struct *);
- long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
- long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
- int (*mmap) (struct file *, struct vm_area_struct *);
- int (*open) (struct inode *, struct file *);
- int (*flush) (struct file *, fl_owner_t id);
- int (*release) (struct inode *, struct file *);
- int (*fsync) (struct file *, loff_t, loff_t, int datasync);
- int (*fasync) (int, struct file *, int);
- int (*lock) (struct file *, int, struct file_lock *);
- ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
- unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
- int (*check_flags)(int);
- int (*flock) (struct file *, int, struct file_lock *);
- ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
- ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
- int (*setlease)(struct file *, long, struct file_lock **, void **);
- long (*fallocate)(struct file *file, int mode, loff_t offset,
- loff_t len);
- void (*show_fdinfo)(struct seq_file *m, struct file *f);
-#ifndef CONFIG_MMU
- unsigned (*mmap_capabilities)(struct file *);
-#endif
- ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t, size_t, unsigned int);
- loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- loff_t len, unsigned int remap_flags);
- int (*fadvise)(struct file *, loff_t, loff_t, int);
-};
+.. code-block:: c
+
+ struct file_operations {
+ struct module *owner;
+ loff_t (*llseek) (struct file *, loff_t, int);
+ ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
+ ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
+ ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
+ ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
+ int (*iopoll)(struct kiocb *kiocb, bool spin);
+ int (*iterate) (struct file *, struct dir_context *);
+ int (*iterate_shared) (struct file *, struct dir_context *);
+ __poll_t (*poll) (struct file *, struct poll_table_struct *);
+ long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
+ long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
+ int (*mmap) (struct file *, struct vm_area_struct *);
+ int (*open) (struct inode *, struct file *);
+ int (*flush) (struct file *, fl_owner_t id);
+ int (*release) (struct inode *, struct file *);
+ int (*fsync) (struct file *, loff_t, loff_t, int datasync);
+ int (*fasync) (int, struct file *, int);
+ int (*lock) (struct file *, int, struct file_lock *);
+ ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
+ unsigned long (*get_unmapped_area)(struct file *, unsigned long,
+ unsigned long, unsigned long, unsigned long);
+ int (*check_flags)(int);
+ int (*flock) (struct file *, int, struct file_lock *);
+ ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
+ loff_t *, size_t, unsigned int);
+ ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
+ size_t, unsigned int);
+ int (*setlease)(struct file *, long, struct file_lock **, void **);
+ long (*fallocate)(struct file *file, int mode, loff_t offset, loff_t len);
+ void (*show_fdinfo)(struct seq_file *m, struct file *f);
+ #ifndef CONFIG_MMU
+ unsigned (*mmap_capabilities)(struct file *);
+ #endif
+ ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t,
+ size_t, unsigned int);
+ loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ loff_t len, unsigned int remap_flags);
+ int (*fadvise)(struct file *, loff_t, loff_t, int);
+ };
Again, all methods are called without any locks being held, unless
otherwise noted.
@@ -1006,21 +1019,23 @@ here. These methods may be set to NULL, as they are either optional or
the VFS uses a default. As of kernel 2.6.22, the following members are
defined:
-struct dentry_operations {
- int (*d_revalidate)(struct dentry *, unsigned int);
- int (*d_weak_revalidate)(struct dentry *, unsigned int);
- int (*d_hash)(const struct dentry *, struct qstr *);
- int (*d_compare)(const struct dentry *,
- unsigned int, const char *, const struct qstr *);
- int (*d_delete)(const struct dentry *);
- int (*d_init)(struct dentry *);
- void (*d_release)(struct dentry *);
- void (*d_iput)(struct dentry *, struct inode *);
- char *(*d_dname)(struct dentry *, char *, int);
- struct vfsmount *(*d_automount)(struct path *);
- int (*d_manage)(const struct path *, bool);
- struct dentry *(*d_real)(struct dentry *, const struct inode *);
-};
+.. code-block:: c
+
+ struct dentry_operations {
+ int (*d_revalidate)(struct dentry *, unsigned int);
+ int (*d_weak_revalidate)(struct dentry *, unsigned int);
+ int (*d_hash)(const struct dentry *, struct qstr *);
+ int (*d_compare)(const struct dentry *,
+ unsigned int, const char *, const struct qstr *);
+ int (*d_delete)(const struct dentry *);
+ int (*d_init)(struct dentry *);
+ void (*d_release)(struct dentry *);
+ void (*d_iput)(struct dentry *, struct inode *);
+ char *(*d_dname)(struct dentry *, char *, int);
+ struct vfsmount *(*d_automount)(struct path *);
+ int (*d_manage)(const struct path *, bool);
+ struct dentry *(*d_real)(struct dentry *, const struct inode *);
+ };
- d_revalidate: called when the VFS needs to revalidate a dentry. This
is called whenever a name look-up finds a dentry in the
@@ -1106,13 +1121,13 @@ struct dentry_operations {
at the end of the buffer, and returns a pointer to the first char.
dynamic_dname() helper function is provided to take care of this.
- Example :
+ .. code-block:: c
- static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
- {
- return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
- dentry->d_inode->i_ino);
- }
+ static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
+ {
+ return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+ dentry->d_inode->i_ino);
+ }
- d_automount: called when an automount dentry is to be traversed (optional).
This should create a new VFS mount record and return the record to the
--
2.21.0
File makes heavy use of lists to describe function parameters. These
are not super clear to read in the HTML output. We can make them
clearer by using backticks to mark them as code.
Use back ticks for listed function parameters.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.rst | 254 +++++++++++++++---------------
1 file changed, 126 insertions(+), 128 deletions(-)
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index dc2dd81f5e83..7ab885de9085 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -126,34 +126,34 @@ members are defined:
struct lock_class_key s_umount_key;
};
-- name: the name of the filesystem type, such as "ext2", "iso9660",
+- ``name``: the name of the filesystem type, such as "ext2", "iso9660",
"msdos" and so on
-- fs_flags: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.)
+- ``fs_flags``: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.)
-- mount: the method to call when a new instance of this
+- ``mount``: the method to call when a new instance of this
filesystem should be mounted
-- kill_sb: the method to call when an instance of this filesystem
+- ``kill_sb``: the method to call when an instance of this filesystem
should be shut down
-- owner: for internal VFS use: you should initialize this to THIS_MODULE in
+- ``owner``: for internal VFS use: you should initialize this to THIS_MODULE in
most cases.
-- next: for internal VFS use: you should initialize this to NULL
+- ``next``: for internal VFS use: you should initialize this to NULL
-- s_lock_key, s_umount_key: lockdep-specific
+- ``s_lock_key``, ``s_umount_key``: lockdep-specific
The mount() method has the following arguments:
-- struct file_system_type *fs_type: describes the filesystem, partly initialized
+- ``struct file_system_type *fs_type``: describes the filesystem, partly initialized
by the specific filesystem code
-- int flags: mount flags
+- ``int flags``: mount flags
-- const char *dev_name: the device name we are mounting.
+- ``const char *dev_name``: the device name we are mounting.
-- void *data: arbitrary mount options, usually comes as an ASCII
+- ``void *data``: arbitrary mount options, usually comes as an ASCII
string (see "Mount Options" section)
The mount() method must return the root dentry of the tree requested by
@@ -179,22 +179,22 @@ implementation.
Usually, a filesystem uses one of the generic mount() implementations
and provides a fill_super() callback instead. The generic variants are:
-- mount_bdev: mount a filesystem residing on a block device
+- ``mount_bdev``: mount a filesystem residing on a block device
-- mount_nodev: mount a filesystem that is not backed by a device
+- ``mount_nodev``: mount a filesystem that is not backed by a device
-- mount_single: mount a filesystem which shares the instance between
+- ``mount_single``: mount a filesystem which shares the instance between
all mounts
A fill_super() callback implementation has the following arguments:
-- struct super_block *sb: the superblock structure. The callback
+- ``struct super_block *sb``: the superblock structure. The callback
must initialize this properly.
-- void *data: arbitrary mount options, usually comes as an ASCII
+- ``void *data``: arbitrary mount options, usually comes as an ASCII
string (see "Mount Options" section)
-- int silent: whether or not to be silent on error
+- ``int silent``: whether or not to be silent on error
The Superblock Object
@@ -240,24 +240,24 @@ noted. This means that most methods can block safely. All methods are
only called from a process context (i.e. not from an interrupt handler
or bottom half).
-- alloc_inode: this method is called by alloc_inode() to allocate memory
+- ``alloc_inode``: this method is called by alloc_inode() to allocate memory
for struct inode and initialize it. If this function is not
defined, a simple 'struct inode' is allocated. Normally
alloc_inode will be used to allocate a larger structure which
contains a 'struct inode' embedded within it.
-- destroy_inode: this method is called by destroy_inode() to release
+- ``destroy_inode``: this method is called by destroy_inode() to release
resources allocated for struct inode. It is only required if
->alloc_inode was defined and simply undoes anything done by
->alloc_inode.
-- dirty_inode: this method is called by the VFS to mark an inode dirty.
+- ``dirty_inode``: this method is called by the VFS to mark an inode dirty.
-- write_inode: this method is called when the VFS needs to write an
+- ``write_inode``: this method is called when the VFS needs to write an
inode to disc. The second parameter indicates whether the write
should be synchronous or not, not all filesystems check this flag.
-- drop_inode: called when the last access to the inode is dropped,
+- ``drop_inode``: called when the last access to the inode is dropped,
with the inode->i_lock spinlock held.
This method should be either NULL (normal UNIX filesystem
@@ -270,43 +270,43 @@ or bottom half).
but does not have the races that the "force_delete()" approach
had.
-- delete_inode: called when the VFS wants to delete an inode
+- ``delete_inode``: called when the VFS wants to delete an inode
-- put_super: called when the VFS wishes to free the superblock
+- ``put_super``: called when the VFS wishes to free the superblock
(i.e. unmount). This is called with the superblock lock held
-- sync_fs: called when VFS is writing out all dirty data associated with
+- ``sync_fs``: called when VFS is writing out all dirty data associated with
a superblock. The second parameter indicates whether the method
should wait until the write out has been completed. Optional.
-- freeze_fs: called when VFS is locking a filesystem and
+- ``freeze_fs``: called when VFS is locking a filesystem and
forcing it into a consistent state. This method is currently
used by the Logical Volume Manager (LVM).
-- unfreeze_fs: called when VFS is unlocking a filesystem and making it writable
+- ``unfreeze_fs``: called when VFS is unlocking a filesystem and making it writable
again.
-- statfs: called when the VFS needs to get filesystem statistics.
+- ``statfs``: called when the VFS needs to get filesystem statistics.
-- remount_fs: called when the filesystem is remounted. This is called
+- ``remount_fs``: called when the filesystem is remounted. This is called
with the kernel lock held
-- clear_inode: called then the VFS clears the inode. Optional
+- ``clear_inode``: called then the VFS clears the inode. Optional
-- umount_begin: called when the VFS is unmounting a filesystem.
+- ``umount_begin``: called when the VFS is unmounting a filesystem.
-- show_options: called by the VFS to show mount options for
+- ``show_options``: called by the VFS to show mount options for
/proc/<pid>/mounts. (see "Mount Options" section)
-- quota_read: called by the VFS to read from filesystem quota file.
+- ``quota_read``: called by the VFS to read from filesystem quota file.
-- quota_write: called by the VFS to write to filesystem quota file.
+- ``quota_write``: called by the VFS to write to filesystem quota file.
-- nr_cached_objects: called by the sb cache shrinking function for the
+- ``nr_cached_objects``: called by the sb cache shrinking function for the
filesystem to return the number of freeable cached objects it contains.
Optional.
-- free_cache_objects: called by the sb cache shrinking function for the
+- ``free_cache_objects``: called by the sb cache shrinking function for the
filesystem to scan the number of objects indicated to try to free them.
Optional, but any filesystem implementing this method needs to also
implement ->nr_cached_objects for it to be called correctly.
@@ -334,20 +334,20 @@ On filesystems that support extended attributes (xattrs), the s_xattr
superblock field points to a NULL-terminated array of xattr handlers.
Extended attributes are name:value pairs.
-- name: Indicates that the handler matches attributes with the specified name
+- ``name``: Indicates that the handler matches attributes with the specified name
(such as "system.posix_acl_access"); the prefix field must be NULL.
-- prefix: Indicates that the handler matches all attributes with the specified
+- ``prefix``: Indicates that the handler matches all attributes with the specified
name prefix (such as "user."); the name field must be NULL.
-- list: Determine if attributes matching this xattr handler should be listed
+- ``list``: Determine if attributes matching this xattr handler should be listed
for a particular dentry. Used by some listxattr implementations like
generic_listxattr.
-- get: Called by the VFS to get the value of a particular extended attribute.
+- ``get``: Called by the VFS to get the value of a particular extended attribute.
This method is called by the getxattr(2) system call.
-- set: Called by the VFS to set the value of a particular extended attribute.
+- ``set``: Called by the VFS to set the value of a particular extended attribute.
When the new value is NULL, called to remove a particular extended
attribute. This method is called by the the setxattr(2) and
removexattr(2) system calls.
@@ -399,13 +399,13 @@ As of kernel 2.6.22, the following members are defined:
Again, all methods are called without any locks being held, unless
otherwise noted.
-- create: called by the open(2) and creat(2) system calls. Only
+- ``create``: called by the open(2) and creat(2) system calls. Only
required if you want to support regular files. The dentry you
get should not have an inode (i.e. it should be a negative
dentry). Here you will probably call d_instantiate() with the
dentry and the newly created inode
-- lookup: called when the VFS needs to look up an inode in a parent
+- ``lookup``: called when the VFS needs to look up an inode in a parent
directory. The name to look for is found in the dentry. This
method must call d_add() to insert the found inode into the
dentry. The "i_count" field in the inode structure should be
@@ -419,31 +419,31 @@ otherwise noted.
to a struct "dentry_operations".
This method is called with the directory inode semaphore held
-- link: called by the link(2) system call. Only required if you want
+- ``link``: called by the link(2) system call. Only required if you want
to support hard links. You will probably need to call
d_instantiate() just as you would in the create() method
-- unlink: called by the unlink(2) system call. Only required if you
+- ``unlink``: called by the unlink(2) system call. Only required if you
want to support deleting inodes
-- symlink: called by the symlink(2) system call. Only required if you
+- ``symlink``: called by the symlink(2) system call. Only required if you
want to support symlinks. You will probably need to call
d_instantiate() just as you would in the create() method
-- mkdir: called by the mkdir(2) system call. Only required if you want
+- ``mkdir``: called by the mkdir(2) system call. Only required if you want
to support creating subdirectories. You will probably need to
call d_instantiate() just as you would in the create() method
-- rmdir: called by the rmdir(2) system call. Only required if you want
+- ``rmdir``: called by the rmdir(2) system call. Only required if you want
to support deleting subdirectories
-- mknod: called by the mknod(2) system call to create a device (char,
+- ``mknod``: called by the mknod(2) system call to create a device (char,
block) inode or a named pipe (FIFO) or socket. Only required
if you want to support creating these types of inodes. You
will probably need to call d_instantiate() just as you would
in the create() method
-- rename: called by the rename(2) system call to rename the object to
+- ``rename``: called by the rename(2) system call to rename the object to
have the parent and name given by the second inode and dentry.
The filesystem must return -EINVAL for any unsupported or
@@ -457,7 +457,7 @@ otherwise noted.
exist; this is checked by the VFS. Unlike plain rename,
source and target may be of different type.
-- get_link: called by the VFS to follow a symbolic link to the
+- ``get_link``: called by the VFS to follow a symbolic link to the
inode it points to. Only required if you want to support
symbolic links. This method returns the symlink body
to traverse (and possibly resets the current position with
@@ -471,13 +471,13 @@ otherwise noted.
argument. If request can't be handled without leaving RCU mode,
have it return ERR_PTR(-ECHILD).
-- readlink: this is now just an override for use by readlink(2) for the
+- ``readlink``: this is now just an override for use by readlink(2) for the
cases when ->get_link uses nd_jump_link() or object is not in
fact a symlink. Normally filesystems should only implement
->get_link for symlinks and readlink(2) will automatically use
that.
-- permission: called by the VFS to check for access rights on a POSIX-like
+- ``permission``: called by the VFS to check for access rights on a POSIX-like
filesystem.
May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
@@ -487,20 +487,20 @@ otherwise noted.
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
-- setattr: called by the VFS to set attributes for a file. This method
+- ``setattr``: called by the VFS to set attributes for a file. This method
is called by chmod(2) and related system calls.
-- getattr: called by the VFS to get attributes of a file. This method
+- ``getattr``: called by the VFS to get attributes of a file. This method
is called by stat(2) and related system calls.
-- listxattr: called by the VFS to list all extended attributes for a
+- ``listxattr``: called by the VFS to list all extended attributes for a
given file. This method is called by the listxattr(2) system call.
-- update_time: called by the VFS to update a specific time or the i_version of
+- ``update_time``: called by the VFS to update a specific time or the i_version of
an inode. If this is not defined the VFS will update the inode itself
and call mark_inode_dirty_sync.
-- atomic_open: called on the last component of an open. Using this optional
+- ``atomic_open``: called on the last component of an open. Using this optional
method the filesystem can look up, possibly create and open the file in
one atomic operation. If it wants to leave actual opening to the
caller (e.g. if the file turned out to be a symlink, device, or just
@@ -512,7 +512,7 @@ otherwise noted.
the method must only succeed if the file didn't exist and hence FMODE_CREATED
shall always be set on success.
-- tmpfile: called in the end of O_TMPFILE open(). Optional, equivalent to
+- ``tmpfile``: called in the end of O_TMPFILE open(). Optional, equivalent to
atomically creating, opening and unlinking a file in given directory.
@@ -666,7 +666,7 @@ cache in your filesystem. The following members are defined:
int (*swap_deactivate)(struct file *);
};
-- writepage: called by the VM to write a dirty page to backing store.
+- ``writepage``: called by the VM to write a dirty page to backing store.
This may happen for data integrity reasons (i.e. 'sync'), or
to free up memory (flush). The difference can be seen in
wbc->sync_mode.
@@ -684,7 +684,7 @@ cache in your filesystem. The following members are defined:
See the file "Locking" for more details.
-- readpage: called by the VM to read a page from backing store.
+- ``readpage``: called by the VM to read a page from backing store.
The page will be Locked when readpage is called, and should be
unlocked and marked uptodate once the read completes.
If ->readpage discovers that it needs to unlock the page for
@@ -692,7 +692,7 @@ cache in your filesystem. The following members are defined:
In this case, the page will be relocated, relocked and if
that all succeeds, ->readpage will be called again.
-- writepages: called by the VM to write out pages associated with the
+- ``writepages``: called by the VM to write out pages associated with the
address_space object. If wbc->sync_mode is WBC_SYNC_ALL, then
the writeback_control will specify a range of pages that must be
written out. If it is WBC_SYNC_NONE, then a nr_to_write is given
@@ -701,7 +701,7 @@ cache in your filesystem. The following members are defined:
instead. This will choose pages from the address space that are
tagged as DIRTY and will pass them to ->writepage.
-- set_page_dirty: called by the VM to set a page dirty.
+- ``set_page_dirty``: called by the VM to set a page dirty.
This is particularly needed if an address space attaches
private data to a page, and that data needs to be updated when
a page is dirtied. This is called, for example, when a memory
@@ -709,14 +709,14 @@ cache in your filesystem. The following members are defined:
If defined, it should set the PageDirty flag, and the
PAGECACHE_TAG_DIRTY tag in the radix tree.
-- readpages: called by the VM to read pages associated with the address_space
+- ``readpages``: called by the VM to read pages associated with the address_space
object. This is essentially just a vector version of
readpage. Instead of just one page, several pages are
requested.
readpages is only used for read-ahead, so read errors are
ignored. If anything goes wrong, feel free to give up.
-- write_begin:
+- ``write_begin``:
Called by the generic buffered write code to ask the filesystem to
prepare to write len bytes at the given offset in the file. The
address_space should check that the write will be able to complete,
@@ -740,7 +740,7 @@ cache in your filesystem. The following members are defined:
Returns 0 on success; < 0 on failure (which is the error code), in
which case write_end is not called.
-- write_end: After a successful write_begin, and data copy, write_end must
+- ``write_end``: After a successful write_begin, and data copy, write_end must
be called. len is the original len passed to write_begin, and copied
is the amount that was able to be copied.
@@ -750,7 +750,7 @@ cache in your filesystem. The following members are defined:
Returns < 0 on failure, otherwise the number of bytes (<= 'copied')
that were able to be copied into pagecache.
-- bmap: called by the VFS to map a logical block offset within object to
+- ``bmap``: called by the VFS to map a logical block offset within object to
physical block number. This method is used by the FIBMAP
ioctl and for working with swap-files. To be able to swap to
a file, the file must have a stable mapping to a block
@@ -758,7 +758,7 @@ cache in your filesystem. The following members are defined:
but instead uses bmap to find out where the blocks in the file
are and uses those addresses directly.
-- invalidatepage: If a page has PagePrivate set, then invalidatepage
+- ``invalidatepage``: If a page has PagePrivate set, then invalidatepage
will be called when part or all of the page is to be removed
from the address space. This generally corresponds to either a
truncation, punch hole or a complete invalidation of the address
@@ -770,7 +770,7 @@ cache in your filesystem. The following members are defined:
be done by calling the ->releasepage function, but in this case the
release MUST succeed.
-- releasepage: releasepage is called on PagePrivate pages to indicate
+- ``releasepage``: releasepage is called on PagePrivate pages to indicate
that the page should be freed if possible. ->releasepage
should remove any private data from the page and clear the
PagePrivate flag. If releasepage() fails for some reason, it must
@@ -791,40 +791,40 @@ cache in your filesystem. The following members are defined:
need to ensure this. Possibly it can clear the PageUptodate
bit if it cannot free private data yet.
-- freepage: freepage is called once the page is no longer visible in
+- ``freepage``: freepage is called once the page is no longer visible in
the page cache in order to allow the cleanup of any private
data. Since it may be called by the memory reclaimer, it
should not assume that the original address_space mapping still
exists, and it should not block.
-- direct_IO: called by the generic read/write routines to perform
+- ``direct_IO``: called by the generic read/write routines to perform
direct_IO - that is IO requests which bypass the page cache
and transfer data directly between the storage and the
application's address space.
-- isolate_page: Called by the VM when isolating a movable non-lru page.
+- ``isolate_page``: Called by the VM when isolating a movable non-lru page.
If page is successfully isolated, VM marks the page as PG_isolated
via __SetPageIsolated.
-- migrate_page: This is used to compact the physical memory usage.
+- ``migrate_page``: This is used to compact the physical memory usage.
If the VM wants to relocate a page (maybe off a memory card
that is signalling imminent failure) it will pass a new page
and an old page to this function. migrate_page should
transfer any private data across and update any references
that it has to the page.
-- putback_page: Called by the VM when isolated page's migration fails.
+- ``putback_page``: Called by the VM when isolated page's migration fails.
-- launder_page: Called before freeing a page - it writes back the dirty page. To
+- ``launder_page``: Called before freeing a page - it writes back the dirty page. To
prevent redirtying the page, it is kept locked during the whole
operation.
-- is_partially_uptodate: Called by the VM when reading a file through the
+- ``is_partially_uptodate``: Called by the VM when reading a file through the
pagecache when the underlying blocksize != pagesize. If the required
block is up to date then the read can complete without needing the IO
to bring the whole page up to date.
-- is_dirty_writeback: Called by the VM when attempting to reclaim a page.
+- ``is_dirty_writeback``: Called by the VM when attempting to reclaim a page.
The VM uses dirty and writeback information to determine if it needs
to stall to allow flushers a chance to complete some IO. Ordinarily
it can use PageDirty and PageWriteback but some filesystems have
@@ -833,17 +833,17 @@ cache in your filesystem. The following members are defined:
allows a filesystem to indicate to the VM if a page should be
treated as dirty or writeback for the purposes of stalling.
-- error_remove_page: normally set to generic_error_remove_page if truncation
+- ``error_remove_page``: normally set to generic_error_remove_page if truncation
is ok for this address space. Used for memory failure handling.
Setting this implies you deal with pages going away under you,
unless you have them locked or reference counts increased.
-- swap_activate: Called when swapon is used on a file to allocate
+- ``swap_activate``: Called when swapon is used on a file to allocate
space if necessary and pin the block lookup information in
memory. A return value of zero indicates success,
in which case this file can be used to back swapspace.
-- swap_deactivate: Called during swapoff on files where swap_activate
+- ``swap_deactivate``: Called during swapoff on files where swap_activate
was successful.
@@ -908,35 +908,33 @@ This describes how the VFS can manipulate an open file. As of kernel
Again, all methods are called without any locks being held, unless
otherwise noted.
-- llseek: called when the VFS needs to move the file position index
+- ``llseek``: called when the VFS needs to move the file position index
-- read: called by read(2) and related system calls
+- ``read``: called by read(2) and related system calls
-- read_iter: possibly asynchronous read with iov_iter as destination
+- ``read_iter``: possibly asynchronous read with iov_iter as destination
-- write: called by write(2) and related system calls
+- ``write``: called by write(2) and related system calls
-- write_iter: possibly asynchronous write with iov_iter as source
+- ``write_iter``: possibly asynchronous write with iov_iter as source
-- iopoll: called when aio wants to poll for completions on HIPRI iocbs
+- ``iopoll``: called when aio wants to poll for completions on HIPRI iocbs
-- iterate: called when the VFS needs to read the directory contents
-
-- iterate_shared: called when the VFS needs to read the directory contents
+- ``iterate_shared``: called when the VFS needs to read the directory contents
when filesystem supports concurrent dir iterators
-- poll: called by the VFS when a process wants to check if there is
+- ``poll``: called by the VFS when a process wants to check if there is
activity on this file and (optionally) go to sleep until there
is activity. Called by the select(2) and poll(2) system calls
-- unlocked_ioctl: called by the ioctl(2) system call.
+- ``unlocked_ioctl``: called by the ioctl(2) system call.
-- compat_ioctl: called by the ioctl(2) system call when 32 bit system calls
+- ``compat_ioctl``: called by the ioctl(2) system call when 32 bit system calls
are used on 64 bit kernels.
-- mmap: called by the mmap(2) system call
+- ``mmap``: called by the mmap(2) system call
-- open: called by the VFS when an inode should be opened. When the VFS
+- ``open``: called by the VFS when an inode should be opened. When the VFS
opens a file, it creates a new "struct file". It then calls the
open method for the newly allocated file structure. You might
think that the open method really belongs in
@@ -946,40 +944,40 @@ otherwise noted.
"private_data" member in the file structure if you want to point
to a device structure
-- flush: called by the close(2) system call to flush a file
+- ``flush``: called by the close(2) system call to flush a file
-- release: called when the last reference to an open file is closed
+- ``release``: called when the last reference to an open file is closed
-- fsync: called by the fsync(2) system call. Also see the section above
+- ``fsync``: called by the fsync(2) system call. Also see the section above
entitled "Handling errors during writeback".
-- fasync: called by the fcntl(2) system call when asynchronous
+- ``fasync``: called by the fcntl(2) system call when asynchronous
(non-blocking) mode is enabled for a file
-- lock: called by the fcntl(2) system call for F_GETLK, F_SETLK, and F_SETLKW
+- ``lock``: called by the fcntl(2) system call for F_GETLK, F_SETLK, and F_SETLKW
commands
-- get_unmapped_area: called by the mmap(2) system call
+- ``get_unmapped_area``: called by the mmap(2) system call
-- check_flags: called by the fcntl(2) system call for F_SETFL command
+- ``check_flags``: called by the fcntl(2) system call for F_SETFL command
-- flock: called by the flock(2) system call
+- ``flock``: called by the flock(2) system call
-- splice_write: called by the VFS to splice data from a pipe to a file. This
+- ``splice_write``: called by the VFS to splice data from a pipe to a file. This
method is used by the splice(2) system call
-- splice_read: called by the VFS to splice data from file to a pipe. This
+- ``splice_read``: called by the VFS to splice data from file to a pipe. This
method is used by the splice(2) system call
-- setlease: called by the VFS to set or release a file lock lease. setlease
+- ``setlease``: called by the VFS to set or release a file lock lease. setlease
implementations should call generic_setlease to record or remove
the lease in the inode after setting it.
-- fallocate: called by the VFS to preallocate blocks or punch a hole.
+- ``fallocate``: called by the VFS to preallocate blocks or punch a hole.
-- copy_file_range: called by the copy_file_range(2) system call.
+- ``copy_file_range``: called by the copy_file_range(2) system call.
-- remap_file_range: called by the ioctl(2) system call for FICLONERANGE and
+- ``remap_file_range``: called by the ioctl(2) system call for FICLONERANGE and
FICLONE and FIDEDUPERANGE commands to remap file ranges. An
implementation should remap len bytes at pos_in of the source file into
the dest file at pos_out. Implementations must handle callers passing
@@ -992,7 +990,7 @@ otherwise noted.
set, the caller is ok with the implementation shortening the request
length to satisfy alignment or EOF requirements (or any other reason).
-- fadvise: possibly called by the fadvise64() system call.
+- ``fadvise``: possibly called by the fadvise64() system call.
Note that the file operations are implemented by the specific
filesystem in which the inode resides. When opening a device node
@@ -1037,7 +1035,7 @@ defined:
struct dentry *(*d_real)(struct dentry *, const struct inode *);
};
-- d_revalidate: called when the VFS needs to revalidate a dentry. This
+- ``d_revalidate``: called when the VFS needs to revalidate a dentry. This
is called whenever a name look-up finds a dentry in the
dcache. Most local filesystems leave this as NULL, because all their
dentries in the dcache are valid. Network filesystems are different
@@ -1056,7 +1054,7 @@ defined:
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
--d_weak_revalidate: called when the VFS needs to revalidate a "jumped" dentry.
+- ``d_weak_revalidate``: called when the VFS needs to revalidate a "jumped" dentry.
This is called when a path-walk ends at dentry that was not acquired by
doing a lookup in the parent directory. This includes "/", "." and "..",
as well as procfs-style symlinks and mountpoint traversal.
@@ -1070,14 +1068,14 @@ defined:
d_weak_revalidate is only called after leaving rcu-walk mode.
-- d_hash: called when the VFS adds a dentry to the hash table. The first
+- ``d_hash``: called when the VFS adds a dentry to the hash table. The first
dentry passed to d_hash is the parent directory that the name is
to be hashed into.
Same locking and synchronisation rules as d_compare regarding
what is safe to dereference etc.
-- d_compare: called to compare a dentry name with a given name. The first
+- ``d_compare``: called to compare a dentry name with a given name. The first
dentry is the parent of the dentry to be compared, the second is
the child dentry. len and name string are properties of the dentry
to be compared. qstr is the name to compare it with.
@@ -1094,22 +1092,22 @@ defined:
It is a tricky calling convention because it needs to be called under
"rcu-walk", ie. without any locks or references on things.
-- d_delete: called when the last reference to a dentry is dropped and the
+- ``d_delete``: called when the last reference to a dentry is dropped and the
dcache is deciding whether or not to cache it. Return 1 to delete
immediately, or 0 to cache the dentry. Default is NULL which means to
always cache a reachable dentry. d_delete must be constant and
idempotent.
-- d_init: called when a dentry is allocated
+- ``d_init``: called when a dentry is allocated
-- d_release: called when a dentry is really deallocated
+- ``d_release``: called when a dentry is really deallocated
-- d_iput: called when a dentry loses its inode (just prior to its
+- ``d_iput``: called when a dentry loses its inode (just prior to its
being deallocated). The default when this is NULL is that the
VFS calls iput(). If you define this method, you must call
iput() yourself
-- d_dname: called when the pathname of a dentry should be generated.
+- ``d_dname``: called when the pathname of a dentry should be generated.
Useful for some pseudo filesystems (sockfs, pipefs, ...) to delay
pathname generation. (Instead of doing it when dentry is created,
it's done only when the path is needed.). Real filesystems probably
@@ -1129,7 +1127,7 @@ defined:
dentry->d_inode->i_ino);
}
-- d_automount: called when an automount dentry is to be traversed (optional).
+- ``d_automount``: called when an automount dentry is to be traversed (optional).
This should create a new VFS mount record and return the record to the
caller. The caller is supplied with a path parameter giving the
automount directory to describe the automount target and the parent
@@ -1149,7 +1147,7 @@ defined:
dentry. This is set by __d_instantiate() if S_AUTOMOUNT is set on the
inode being added.
-- d_manage: called to allow the filesystem to manage the transition from a
+- ``d_manage``: called to allow the filesystem to manage the transition from a
dentry (optional). This allows autofs, for example, to hold up clients
waiting to explore behind a 'mountpoint' while letting the daemon go
past and construct the subtree there. 0 should be returned to let the
@@ -1167,7 +1165,7 @@ defined:
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.
-- d_real: overlay/union type filesystems implement this method to return one of
+- ``d_real``: overlay/union type filesystems implement this method to return one of
the underlying dentries hidden by the overlay. It is used in two
different modes:
@@ -1189,36 +1187,36 @@ Directory Entry Cache API
There are a number of functions defined which permit a filesystem to
manipulate dentries:
-- dget: open a new handle for an existing dentry (this just increments
+- ``dget``: open a new handle for an existing dentry (this just increments
the usage count)
-- dput: close a handle for a dentry (decrements the usage count). If
+- ``dput``: close a handle for a dentry (decrements the usage count). If
the usage count drops to 0, and the dentry is still in its
parent's hash, the "d_delete" method is called to check whether
it should be cached. If it should not be cached, or if the dentry
is not hashed, it is deleted. Otherwise cached dentries are put
into an LRU list to be reclaimed on memory shortage.
-- d_drop: this unhashes a dentry from its parents hash list. A
+- ``d_drop``: this unhashes a dentry from its parents hash list. A
subsequent call to dput() will deallocate the dentry if its
usage count drops to 0
-- d_delete: delete a dentry. If there are no other open references to
+- ``d_delete``: delete a dentry. If there are no other open references to
the dentry then the dentry is turned into a negative dentry
(the d_iput() method is called). If there are other
references, then d_drop() is called instead
-- d_add: add a dentry to its parents hash list and then calls
+- ``d_add``: add a dentry to its parents hash list and then calls
d_instantiate()
-- d_instantiate: add a dentry to the alias hash list for the inode and
+- ``d_instantiate``: add a dentry to the alias hash list for the inode and
updates the "d_inode" member. The "i_count" member in the
inode structure should be set/incremented. If the inode
pointer is NULL, the dentry is called a "negative
dentry". This function is commonly called when an inode is
created for an existing negative dentry
-- d_lookup: look up a dentry given its parent and path name component
+- ``d_lookup``: look up a dentry given its parent and path name component
It looks up the child of that given name from the dcache
hash table. If it is found, the reference count is incremented
and the dentry is returned. The caller must use dput()
--
2.21.0
During conversion of txt file to rst format we added a bunch of lists.
To ease the review of that patch the list contents were not changed. We
do that now as a separate patch.
This patch does not change the contents of the document in any real way,
does whitespace fixes and adds missing periods to list items.
Clean up lists by:
- Adding missing periods.
- Correcting the column width.
- Correcting the indentation.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.rst | 1114 ++++++++++++++---------------
1 file changed, 557 insertions(+), 557 deletions(-)
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 7ab885de9085..bd8f7891f44b 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -127,34 +127,34 @@ members are defined:
};
- ``name``: the name of the filesystem type, such as "ext2", "iso9660",
- "msdos" and so on
+ "msdos" and so on.
-- ``fs_flags``: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.)
+- ``fs_flags``: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.).
-- ``mount``: the method to call when a new instance of this
- filesystem should be mounted
+- ``mount``: the method to call when a new instance of this filesystem
+ should be mounted.
- ``kill_sb``: the method to call when an instance of this filesystem
- should be shut down
+ should be shut down.
-- ``owner``: for internal VFS use: you should initialize this to THIS_MODULE in
- most cases.
+- ``owner``: for internal VFS use: you should initialize this to
+ THIS_MODULE in most cases.
-- ``next``: for internal VFS use: you should initialize this to NULL
+- ``next``: for internal VFS use: you should initialize this to NULL.
-- ``s_lock_key``, ``s_umount_key``: lockdep-specific
+- ``s_lock_key``, ``s_umount_key``: lockdep-specific.
The mount() method has the following arguments:
-- ``struct file_system_type *fs_type``: describes the filesystem, partly initialized
- by the specific filesystem code
+- ``struct file_system_type *fs_type``: describes the filesystem, partly
+ initialized by the specific filesystem code.
-- ``int flags``: mount flags
+- ``int flags``: mount flags.
- ``const char *dev_name``: the device name we are mounting.
- ``void *data``: arbitrary mount options, usually comes as an ASCII
- string (see "Mount Options" section)
+ string (see "Mount Options" section)
The mount() method must return the root dentry of the tree requested by
caller. An active reference to its superblock must be grabbed and the
@@ -179,22 +179,22 @@ implementation.
Usually, a filesystem uses one of the generic mount() implementations
and provides a fill_super() callback instead. The generic variants are:
-- ``mount_bdev``: mount a filesystem residing on a block device
+- ``mount_bdev``: mount a filesystem residing on a block device.
-- ``mount_nodev``: mount a filesystem that is not backed by a device
+- ``mount_nodev``: mount a filesystem that is not backed by a device.
- ``mount_single``: mount a filesystem which shares the instance between
- all mounts
+ all mounts.
A fill_super() callback implementation has the following arguments:
- ``struct super_block *sb``: the superblock structure. The callback
- must initialize this properly.
+ must initialize this properly.
- ``void *data``: arbitrary mount options, usually comes as an ASCII
- string (see "Mount Options" section)
+ string (see "Mount Options" section).
-- ``int silent``: whether or not to be silent on error
+- ``int silent``: whether or not to be silent on error.
The Superblock Object
@@ -240,87 +240,87 @@ noted. This means that most methods can block safely. All methods are
only called from a process context (i.e. not from an interrupt handler
or bottom half).
-- ``alloc_inode``: this method is called by alloc_inode() to allocate memory
- for struct inode and initialize it. If this function is not
- defined, a simple 'struct inode' is allocated. Normally
- alloc_inode will be used to allocate a larger structure which
- contains a 'struct inode' embedded within it.
+- ``alloc_inode``: this method is called by alloc_inode() to allocate
+ memory for struct inode and initialize it. If this function is not
+ defined, a simple 'struct inode' is allocated. Normally alloc_inode
+ will be used to allocate a larger structure which contains a 'struct
+ inode' embedded within it.
- ``destroy_inode``: this method is called by destroy_inode() to release
- resources allocated for struct inode. It is only required if
- ->alloc_inode was defined and simply undoes anything done by
- ->alloc_inode.
+ resources allocated for struct inode. It is only required if
+ ->alloc_inode was defined and simply undoes anything done by
+ ->alloc_inode.
-- ``dirty_inode``: this method is called by the VFS to mark an inode dirty.
+- ``dirty_inode``: this method is called by the VFS to mark an inode
+ dirty.
- ``write_inode``: this method is called when the VFS needs to write an
- inode to disc. The second parameter indicates whether the write
- should be synchronous or not, not all filesystems check this flag.
+ inode to disc. The second parameter indicates whether the write
+ should be synchronous or not, not all filesystems check this flag.
- ``drop_inode``: called when the last access to the inode is dropped,
- with the inode->i_lock spinlock held.
+ with the inode->i_lock spinlock held.
- This method should be either NULL (normal UNIX filesystem
- semantics) or "generic_delete_inode" (for filesystems that do not
- want to cache inodes - causing "delete_inode" to always be
- called regardless of the value of i_nlink)
+ This method should be either NULL (normal UNIX filesystem semantics)
+ or "generic_delete_inode" (for filesystems that do not want to cache
+ inodes - causing "delete_inode" to always be called regardless of the
+ value of i_nlink).
- The "generic_delete_inode()" behavior is equivalent to the
- old practice of using "force_delete" in the put_inode() case,
- but does not have the races that the "force_delete()" approach
- had.
+ The "generic_delete_inode()" behavior is equivalent to the old
+ practice of using "force_delete" in the put_inode() case, but does not
+ have the races that the "force_delete()" approach had.
-- ``delete_inode``: called when the VFS wants to delete an inode
+- ``delete_inode``: called when the VFS wants to delete an inode.
- ``put_super``: called when the VFS wishes to free the superblock
- (i.e. unmount). This is called with the superblock lock held
+ (i.e. unmount). This is called with the superblock lock held.
-- ``sync_fs``: called when VFS is writing out all dirty data associated with
- a superblock. The second parameter indicates whether the method
- should wait until the write out has been completed. Optional.
+- ``sync_fs``: called when VFS is writing out all dirty data associated
+ with a superblock. The second parameter indicates whether the method
+ should wait until the write out has been completed. Optional.
-- ``freeze_fs``: called when VFS is locking a filesystem and
- forcing it into a consistent state. This method is currently
- used by the Logical Volume Manager (LVM).
+- ``freeze_fs``: called when VFS is locking a filesystem and forcing it
+ into a consistent state. This method is currently used by the Logical
+ Volume Manager (LVM).
-- ``unfreeze_fs``: called when VFS is unlocking a filesystem and making it writable
- again.
+- ``unfreeze_fs``: called when VFS is unlocking a filesystem and making
+ it writable again.
- ``statfs``: called when the VFS needs to get filesystem statistics.
-- ``remount_fs``: called when the filesystem is remounted. This is called
- with the kernel lock held
+- ``remount_fs``: called when the filesystem is remounted. This is
+ called with the kernel lock held.
-- ``clear_inode``: called then the VFS clears the inode. Optional
+- ``clear_inode``: called then the VFS clears the inode. Optional.
- ``umount_begin``: called when the VFS is unmounting a filesystem.
- ``show_options``: called by the VFS to show mount options for
- /proc/<pid>/mounts. (see "Mount Options" section)
+ /proc/<pid>/mounts (see "Mount Options" section).
- ``quota_read``: called by the VFS to read from filesystem quota file.
- ``quota_write``: called by the VFS to write to filesystem quota file.
-- ``nr_cached_objects``: called by the sb cache shrinking function for the
- filesystem to return the number of freeable cached objects it contains.
- Optional.
+- ``nr_cached_objects``: called by the sb cache shrinking function for
+ the filesystem to return the number of freeable cached objects it
+ contains. Optional.
-- ``free_cache_objects``: called by the sb cache shrinking function for the
- filesystem to scan the number of objects indicated to try to free them.
- Optional, but any filesystem implementing this method needs to also
- implement ->nr_cached_objects for it to be called correctly.
+- ``free_cache_objects``: called by the sb cache shrinking function for
+ the filesystem to scan the number of objects indicated to try to free
+ them. Optional, but any filesystem implementing this method needs to
+ also implement ->nr_cached_objects for it to be called correctly.
- We can't do anything with any errors that the filesystem might
- encountered, hence the void return type. This will never be called if
- the VM is trying to reclaim under GFP_NOFS conditions, hence this
- method does not need to handle that situation itself.
+ We can't do anything with any errors that the filesystem might
+ encountered, hence the void return type. This will never be called if
+ the VM is trying to reclaim under GFP_NOFS conditions, hence this
+ method does not need to handle that situation itself.
- Implementations must include conditional reschedule calls inside any
- scanning loop that is done. This allows the VFS to determine
- appropriate scan batch sizes without having to worry about whether
- implementations will cause holdoff problems due to large scan batch
- sizes.
+ Implementations must include conditional reschedule calls inside any
+ scanning loop that is done. This allows the VFS to determine
+ appropriate scan batch sizes without having to worry about whether
+ implementations will cause holdoff problems due to large scan batch
+ sizes.
Whoever sets up the inode is responsible for filling in the "i_op"
field. This is a pointer to a "struct inode_operations" which describes
@@ -334,23 +334,24 @@ On filesystems that support extended attributes (xattrs), the s_xattr
superblock field points to a NULL-terminated array of xattr handlers.
Extended attributes are name:value pairs.
-- ``name``: Indicates that the handler matches attributes with the specified name
- (such as "system.posix_acl_access"); the prefix field must be NULL.
+- ``name``: Indicates that the handler matches attributes with the
+ specified name (such as "system.posix_acl_access"); the prefix field
+ must be NULL.
-- ``prefix``: Indicates that the handler matches all attributes with the specified
- name prefix (such as "user."); the name field must be NULL.
+- ``prefix``: Indicates that the handler matches all attributes with the
+ specified name prefix (such as "user."); the name field must be NULL.
-- ``list``: Determine if attributes matching this xattr handler should be listed
- for a particular dentry. Used by some listxattr implementations like
- generic_listxattr.
+- ``list``: Determine if attributes matching this xattr handler should
+ be listed for a particular dentry. Used by some listxattr
+ implementations like generic_listxattr.
-- ``get``: Called by the VFS to get the value of a particular extended attribute.
- This method is called by the getxattr(2) system call.
+- ``get``: Called by the VFS to get the value of a particular extended
+ attribute. This method is called by the getxattr(2) system call.
-- ``set``: Called by the VFS to set the value of a particular extended attribute.
- When the new value is NULL, called to remove a particular extended
- attribute. This method is called by the the setxattr(2) and
- removexattr(2) system calls.
+- ``set``: Called by the VFS to set the value of a particular extended
+ attribute. When the new value is NULL, called to remove a particular
+ extended attribute. This method is called by the the setxattr(2) and
+ removexattr(2) system calls.
When none of the xattr handlers of a filesystem match the specified
attribute name or when a filesystem doesn't support extended attributes,
@@ -400,120 +401,118 @@ Again, all methods are called without any locks being held, unless
otherwise noted.
- ``create``: called by the open(2) and creat(2) system calls. Only
- required if you want to support regular files. The dentry you
- get should not have an inode (i.e. it should be a negative
- dentry). Here you will probably call d_instantiate() with the
- dentry and the newly created inode
+ required if you want to support regular files. The dentry you get
+ should not have an inode (i.e. it should be a negative dentry). Here
+ you will probably call d_instantiate() with the dentry and the newly
+ created inode.
- ``lookup``: called when the VFS needs to look up an inode in a parent
- directory. The name to look for is found in the dentry. This
- method must call d_add() to insert the found inode into the
- dentry. The "i_count" field in the inode structure should be
- incremented. If the named inode does not exist a NULL inode
- should be inserted into the dentry (this is called a negative
- dentry). Returning an error code from this routine must only
- be done on a real error, otherwise creating inodes with system
- calls like create(2), mknod(2), mkdir(2) and so on will fail.
- If you wish to overload the dentry methods then you should
- initialise the "d_dop" field in the dentry; this is a pointer
- to a struct "dentry_operations".
- This method is called with the directory inode semaphore held
-
-- ``link``: called by the link(2) system call. Only required if you want
- to support hard links. You will probably need to call
- d_instantiate() just as you would in the create() method
+ directory. The name to look for is found in the dentry. This method
+ must call d_add() to insert the found inode into the dentry. The
+ "i_count" field in the inode structure should be incremented. If the
+ named inode does not exist a NULL inode should be inserted into the
+ dentry (this is called a negative dentry). Returning an error code
+ from this routine must only be done on a real error, otherwise
+ creating inodes with system calls like create(2), mknod(2), mkdir(2)
+ and so on will fail. If you wish to overload the dentry methods then
+ you should initialise the "d_dop" field in the dentry; this is a
+ pointer to a struct "dentry_operations". This method is called with
+ the directory inode semaphore held.
+
+- ``link``: called by the link(2) system call. Only required if you
+ want to support hard links. You will probably need to call
+ d_instantiate() just as you would in the create() method.
- ``unlink``: called by the unlink(2) system call. Only required if you
- want to support deleting inodes
-
-- ``symlink``: called by the symlink(2) system call. Only required if you
- want to support symlinks. You will probably need to call
- d_instantiate() just as you would in the create() method
-
-- ``mkdir``: called by the mkdir(2) system call. Only required if you want
- to support creating subdirectories. You will probably need to
- call d_instantiate() just as you would in the create() method
-
-- ``rmdir``: called by the rmdir(2) system call. Only required if you want
- to support deleting subdirectories
-
-- ``mknod``: called by the mknod(2) system call to create a device (char,
- block) inode or a named pipe (FIFO) or socket. Only required
- if you want to support creating these types of inodes. You
- will probably need to call d_instantiate() just as you would
- in the create() method
-
-- ``rename``: called by the rename(2) system call to rename the object to
- have the parent and name given by the second inode and dentry.
-
- The filesystem must return -EINVAL for any unsupported or
- unknown flags. Currently the following flags are implemented:
- (1) RENAME_NOREPLACE: this flag indicates that if the target
- of the rename exists the rename should fail with -EEXIST
- instead of replacing the target. The VFS already checks for
- existence, so for local filesystems the RENAME_NOREPLACE
- implementation is equivalent to plain rename.
- (2) RENAME_EXCHANGE: exchange source and target. Both must
- exist; this is checked by the VFS. Unlike plain rename,
- source and target may be of different type.
-
-- ``get_link``: called by the VFS to follow a symbolic link to the
- inode it points to. Only required if you want to support
- symbolic links. This method returns the symlink body
- to traverse (and possibly resets the current position with
- nd_jump_link()). If the body won't go away until the inode
- is gone, nothing else is needed; if it needs to be otherwise
- pinned, arrange for its release by having get_link(..., ..., done)
- do set_delayed_call(done, destructor, argument).
- In that case destructor(argument) will be called once VFS is
- done with the body you've returned.
- May be called in RCU mode; that is indicated by NULL dentry
- argument. If request can't be handled without leaving RCU mode,
- have it return ERR_PTR(-ECHILD).
-
-- ``readlink``: this is now just an override for use by readlink(2) for the
- cases when ->get_link uses nd_jump_link() or object is not in
- fact a symlink. Normally filesystems should only implement
- ->get_link for symlinks and readlink(2) will automatically use
- that.
-
-- ``permission``: called by the VFS to check for access rights on a POSIX-like
- filesystem.
-
- May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
- mode, the filesystem must check the permission without blocking or
- storing to the inode.
-
- If a situation is encountered that rcu-walk cannot handle, return
- -ECHILD and it will be called again in ref-walk mode.
-
-- ``setattr``: called by the VFS to set attributes for a file. This method
- is called by chmod(2) and related system calls.
-
-- ``getattr``: called by the VFS to get attributes of a file. This method
- is called by stat(2) and related system calls.
+ want to support deleting inodes.
+
+- ``symlink``: called by the symlink(2) system call. Only required if
+ you want to support symlinks. You will probably need to call
+ d_instantiate() just as you would in the create() method.
+
+- ``mkdir``: called by the mkdir(2) system call. Only required if you
+ want to support creating subdirectories. You will probably need to
+ call d_instantiate() just as you would in the create() method.
+
+- ``rmdir``: called by the rmdir(2) system call. Only required if you
+ want to support deleting subdirectories.
+
+- ``mknod``: called by the mknod(2) system call to create a device
+ (char, block) inode or a named pipe (FIFO) or socket. Only required
+ if you want to support creating these types of inodes. You will
+ probably need to call d_instantiate() just as you would in the
+ create() method.
+
+- ``rename``: called by the rename(2) system call to rename the object
+ to have the parent and name given by the second inode and dentry.
+
+ The filesystem must return -EINVAL for any unsupported or unknown
+ flags. Currently the following flags are implemented:
+
+ 1. ``RENAME_NOREPLACE``: this flag indicates that if the target of the
+ rename exists the rename should fail with -EEXIST instead of
+ replacing the target. The VFS already checks for existence, so for
+ local filesystems the RENAME_NOREPLACE implementation is equivalent
+ to plain rename.
+ 2. ``RENAME_EXCHANGE``: exchange source and target. Both must exist;
+ this is checked by the VFS. Unlike plain rename, source and target
+ may be of different type.
+
+- ``get_link``: called by the VFS to follow a symbolic link to the inode
+ it points to. Only required if you want to support symbolic links.
+ This method returns the symlink body to traverse (and possibly resets
+ the current position with nd_jump_link()). If the body won't go away
+ until the inode is gone, nothing else is needed; if it needs to be
+ otherwise pinned, arrange for its release by having get_link(..., ...,
+ done) do set_delayed_call(done, destructor, argument). In that case
+ destructor(argument) will be called once VFS is done with the body
+ you've returned. May be called in RCU mode; that is indicated by NULL
+ dentry argument. If request can't be handled without leaving RCU
+ mode, have it return ERR_PTR(-ECHILD).
+
+- ``readlink``: this is now just an override for use by readlink(2) for
+ the cases when ->get_link uses nd_jump_link() or object is not in fact
+ a symlink. Normally filesystems should only implement ->get_link for
+ symlinks and readlink(2) will automatically use that.
+
+- ``permission``: called by the VFS to check for access rights on a
+ POSIX-like filesystem.
+
+ May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
+ mode, the filesystem must check the permission without blocking or
+ storing to the inode.
+
+ If a situation is encountered that rcu-walk cannot handle, return
+ -ECHILD and it will be called again in ref-walk mode.
+
+- ``setattr``: called by the VFS to set attributes for a file. This
+ method is called by chmod(2) and related system calls.
+
+- ``getattr``: called by the VFS to get attributes of a file. This
+ method is called by stat(2) and related system calls.
- ``listxattr``: called by the VFS to list all extended attributes for a
- given file. This method is called by the listxattr(2) system call.
+ given file. This method is called by the listxattr(2) system call.
-- ``update_time``: called by the VFS to update a specific time or the i_version of
- an inode. If this is not defined the VFS will update the inode itself
- and call mark_inode_dirty_sync.
+- ``update_time``: called by the VFS to update a specific time or the
+ i_version of an inode. If this is not defined the VFS will update the
+ inode itself and call mark_inode_dirty_sync.
-- ``atomic_open``: called on the last component of an open. Using this optional
- method the filesystem can look up, possibly create and open the file in
- one atomic operation. If it wants to leave actual opening to the
- caller (e.g. if the file turned out to be a symlink, device, or just
- something filesystem won't do atomic open for), it may signal this by
- returning finish_no_open(file, dentry). This method is only called if
- the last component is negative or needs lookup. Cached positive dentries
- are still handled by f_op->open(). If the file was created,
- FMODE_CREATED flag should be set in file->f_mode. In case of O_EXCL
- the method must only succeed if the file didn't exist and hence FMODE_CREATED
- shall always be set on success.
+- ``atomic_open``: called on the last component of an open. Using this
+ optional method the filesystem can look up, possibly create and open
+ the file in one atomic operation. If it wants to leave actual opening
+ to the caller (e.g. if the file turned out to be a symlink, device, or
+ just something filesystem won't do atomic open for), it may signal
+ this by returning finish_no_open(file, dentry). This method is only
+ called if the last component is negative or needs lookup. Cached
+ positive dentries are still handled by f_op->open(). If the file was
+ created, FMODE_CREATED flag should be set in file->f_mode. In case of
+ O_EXCL the method must only succeed if the file didn't exist and hence
+ FMODE_CREATED shall always be set on success.
-- ``tmpfile``: called in the end of O_TMPFILE open(). Optional, equivalent to
- atomically creating, opening and unlinking a file in given directory.
+- ``tmpfile``: called in the end of O_TMPFILE open(). Optional,
+ equivalent to atomically creating, opening and unlinking a file in
+ given directory.
The Address Space Object
@@ -666,185 +665,180 @@ cache in your filesystem. The following members are defined:
int (*swap_deactivate)(struct file *);
};
-- ``writepage``: called by the VM to write a dirty page to backing store.
- This may happen for data integrity reasons (i.e. 'sync'), or
- to free up memory (flush). The difference can be seen in
- wbc->sync_mode.
- The PG_Dirty flag has been cleared and PageLocked is true.
- writepage should start writeout, should set PG_Writeback,
- and should make sure the page is unlocked, either synchronously
- or asynchronously when the write operation completes.
-
- If wbc->sync_mode is WB_SYNC_NONE, ->writepage doesn't have to
- try too hard if there are problems, and may choose to write out
- other pages from the mapping if that is easier (e.g. due to
- internal dependencies). If it chooses not to start writeout, it
- should return AOP_WRITEPAGE_ACTIVATE so that the VM will not keep
- calling ->writepage on that page.
-
- See the file "Locking" for more details.
-
-- ``readpage``: called by the VM to read a page from backing store.
- The page will be Locked when readpage is called, and should be
- unlocked and marked uptodate once the read completes.
- If ->readpage discovers that it needs to unlock the page for
- some reason, it can do so, and then return AOP_TRUNCATED_PAGE.
- In this case, the page will be relocated, relocked and if
- that all succeeds, ->readpage will be called again.
-
-- ``writepages``: called by the VM to write out pages associated with the
- address_space object. If wbc->sync_mode is WBC_SYNC_ALL, then
- the writeback_control will specify a range of pages that must be
- written out. If it is WBC_SYNC_NONE, then a nr_to_write is given
- and that many pages should be written if possible.
- If no ->writepages is given, then mpage_writepages is used
- instead. This will choose pages from the address space that are
- tagged as DIRTY and will pass them to ->writepage.
-
-- ``set_page_dirty``: called by the VM to set a page dirty.
- This is particularly needed if an address space attaches
- private data to a page, and that data needs to be updated when
- a page is dirtied. This is called, for example, when a memory
- mapped page gets modified.
- If defined, it should set the PageDirty flag, and the
- PAGECACHE_TAG_DIRTY tag in the radix tree.
-
-- ``readpages``: called by the VM to read pages associated with the address_space
- object. This is essentially just a vector version of
- readpage. Instead of just one page, several pages are
- requested.
- readpages is only used for read-ahead, so read errors are
- ignored. If anything goes wrong, feel free to give up.
-
-- ``write_begin``:
- Called by the generic buffered write code to ask the filesystem to
- prepare to write len bytes at the given offset in the file. The
- address_space should check that the write will be able to complete,
- by allocating space if necessary and doing any other internal
- housekeeping. If the write will update parts of any basic-blocks on
- storage, then those blocks should be pre-read (if they haven't been
- read already) so that the updated blocks can be written out properly.
-
- The filesystem must return the locked pagecache page for the specified
- offset, in *pagep, for the caller to write into.
-
- It must be able to cope with short writes (where the length passed to
- write_begin is greater than the number of bytes copied into the page).
-
- flags is a field for AOP_FLAG_xxx flags, described in
- include/linux/fs.h.
-
- A void * may be returned in fsdata, which then gets passed into
- write_end.
-
- Returns 0 on success; < 0 on failure (which is the error code), in
- which case write_end is not called.
-
-- ``write_end``: After a successful write_begin, and data copy, write_end must
- be called. len is the original len passed to write_begin, and copied
- is the amount that was able to be copied.
-
- The filesystem must take care of unlocking the page and releasing it
- refcount, and updating i_size.
-
- Returns < 0 on failure, otherwise the number of bytes (<= 'copied')
- that were able to be copied into pagecache.
-
-- ``bmap``: called by the VFS to map a logical block offset within object to
- physical block number. This method is used by the FIBMAP
- ioctl and for working with swap-files. To be able to swap to
- a file, the file must have a stable mapping to a block
- device. The swap system does not go through the filesystem
- but instead uses bmap to find out where the blocks in the file
- are and uses those addresses directly.
+- ``writepage``: called by the VM to write a dirty page to backing
+ store. This may happen for data integrity reasons (i.e. 'sync'), or
+ to free up memory (flush). The difference can be seen in
+ wbc->sync_mode. The PG_Dirty flag has been cleared and PageLocked is
+ true. writepage should start writeout, should set PG_Writeback, and
+ should make sure the page is unlocked, either synchronously or
+ asynchronously when the write operation completes.
+
+ If wbc->sync_mode is WB_SYNC_NONE, ->writepage doesn't have to try too
+ hard if there are problems, and may choose to write out other pages
+ from the mapping if that is easier (e.g. due to internal
+ dependencies). If it chooses not to start writeout, it should return
+ AOP_WRITEPAGE_ACTIVATE so that the VM will not keep calling
+ ->writepage on that page.
+
+ See the file "Locking" for more details.
+
+- ``readpage``: called by the VM to read a page from backing store. The
+ page will be Locked when readpage is called, and should be unlocked
+ and marked uptodate once the read completes. If ->readpage discovers
+ that it needs to unlock the page for some reason, it can do so, and
+ then return AOP_TRUNCATED_PAGE. In this case, the page will be
+ relocated, relocked and if that all succeeds, ->readpage will be
+ called again.
+
+- ``writepages``: called by the VM to write out pages associated with
+ the address_space object. If wbc->sync_mode is WBC_SYNC_ALL, then the
+ writeback_control will specify a range of pages that must be written
+ out. If it is WBC_SYNC_NONE, then a nr_to_write is given and that
+ many pages should be written if possible. If no ->writepages is
+ given, then mpage_writepages is used instead. This will choose pages
+ from the address space that are tagged as DIRTY and will pass them to
+ ->writepage.
+
+- ``set_page_dirty``: called by the VM to set a page dirty. This is
+ particularly needed if an address space attaches private data to a
+ page, and that data needs to be updated when a page is dirtied. This
+ is called, for example, when a memory mapped page gets modified. If
+ defined, it should set the PageDirty flag, and the PAGECACHE_TAG_DIRTY
+ tag in the radix tree.
+
+- ``readpages``: called by the VM to read pages associated with the
+ address_space object. This is essentially just a vector version of
+ readpage. Instead of just one page, several pages are requested.
+ readpages is only used for read-ahead, so read errors are ignored. If
+ anything goes wrong, feel free to give up.
+
+- ``write_begin``: Called by the generic buffered write code to ask the
+ filesystem to prepare to write len bytes at the given offset in the
+ file. The address_space should check that the write will be able to
+ complete, by allocating space if necessary and doing any other
+ internal housekeeping. If the write will update parts of any
+ basic-blocks on storage, then those blocks should be pre-read (if they
+ haven't been read already) so that the updated blocks can be written
+ out properly.
+
+ The filesystem must return the locked pagecache page for the specified
+ offset, in *pagep, for the caller to write into.
+
+ It must be able to cope with short writes (where the length passed to
+ write_begin is greater than the number of bytes copied into the page).
+
+ flags is a field for AOP_FLAG_xxx flags, described in
+ include/linux/fs.h.
+
+ A void * may be returned in fsdata, which then gets passed into
+ write_end.
+
+ Returns 0 on success; < 0 on failure (which is the error code), in
+ which case write_end is not called.
+
+- ``write_end``: After a successful write_begin, and data copy,
+ write_end must be called. len is the original len passed to
+ write_begin, and copied is the amount that was able to be copied.
+
+ The filesystem must take care of unlocking the page and releasing it
+ refcount, and updating i_size.
+
+ Returns < 0 on failure, otherwise the number of bytes (<= 'copied')
+ that were able to be copied into pagecache.
+
+- ``bmap``: called by the VFS to map a logical block offset within
+ object to physical block number. This method is used by the FIBMAP
+ ioctl and for working with swap-files. To be able to swap to a file,
+ the file must have a stable mapping to a block device. The swap
+ system does not go through the filesystem but instead uses bmap to
+ find out where the blocks in the file are and uses those addresses
+ directly.
- ``invalidatepage``: If a page has PagePrivate set, then invalidatepage
- will be called when part or all of the page is to be removed
- from the address space. This generally corresponds to either a
- truncation, punch hole or a complete invalidation of the address
- space (in the latter case 'offset' will always be 0 and 'length'
- will be PAGE_SIZE). Any private data associated with the page
- should be updated to reflect this truncation. If offset is 0 and
- length is PAGE_SIZE, then the private data should be released,
- because the page must be able to be completely discarded. This may
- be done by calling the ->releasepage function, but in this case the
- release MUST succeed.
-
-- ``releasepage``: releasepage is called on PagePrivate pages to indicate
- that the page should be freed if possible. ->releasepage
- should remove any private data from the page and clear the
- PagePrivate flag. If releasepage() fails for some reason, it must
- indicate failure with a 0 return value.
- releasepage() is used in two distinct though related cases. The
- first is when the VM finds a clean page with no active users and
- wants to make it a free page. If ->releasepage succeeds, the
- page will be removed from the address_space and become free.
-
- The second case is when a request has been made to invalidate
- some or all pages in an address_space. This can happen
- through the fadvise(POSIX_FADV_DONTNEED) system call or by the
- filesystem explicitly requesting it as nfs and 9fs do (when
- they believe the cache may be out of date with storage) by
- calling invalidate_inode_pages2().
- If the filesystem makes such a call, and needs to be certain
- that all pages are invalidated, then its releasepage will
- need to ensure this. Possibly it can clear the PageUptodate
- bit if it cannot free private data yet.
+ will be called when part or all of the page is to be removed from the
+ address space. This generally corresponds to either a truncation,
+ punch hole or a complete invalidation of the address space (in the
+ latter case 'offset' will always be 0 and 'length' will be PAGE_SIZE).
+ Any private data associated with the page should be updated to reflect
+ this truncation. If offset is 0 and length is PAGE_SIZE, then the
+ private data should be released, because the page must be able to be
+ completely discarded. This may be done by calling the ->releasepage
+ function, but in this case the release MUST succeed.
+
+- ``releasepage``: releasepage is called on PagePrivate pages to
+ indicate that the page should be freed if possible. ->releasepage
+ should remove any private data from the page and clear the PagePrivate
+ flag. If releasepage() fails for some reason, it must indicate
+ failure with a 0 return value. releasepage() is used in two distinct
+ though related cases. The first is when the VM finds a clean page
+ with no active users and wants to make it a free page. If
+ ->releasepage succeeds, the page will be removed from the
+ address_space and become free.
+
+ The second case is when a request has been made to invalidate some or
+ all pages in an address_space. This can happen through the
+ fadvise(POSIX_FADV_DONTNEED) system call or by the filesystem
+ explicitly requesting it as nfs and 9fs do (when they believe the
+ cache may be out of date with storage) by calling
+ invalidate_inode_pages2(). If the filesystem makes such a call, and
+ needs to be certain that all pages are invalidated, then its
+ releasepage will need to ensure this. Possibly it can clear the
+ PageUptodate bit if it cannot free private data yet.
- ``freepage``: freepage is called once the page is no longer visible in
- the page cache in order to allow the cleanup of any private
- data. Since it may be called by the memory reclaimer, it
- should not assume that the original address_space mapping still
- exists, and it should not block.
+ the page cache in order to allow the cleanup of any private data.
+ Since it may be called by the memory reclaimer, it should not assume
+ that the original address_space mapping still exists, and it should
+ not block.
- ``direct_IO``: called by the generic read/write routines to perform
- direct_IO - that is IO requests which bypass the page cache
- and transfer data directly between the storage and the
- application's address space.
-
-- ``isolate_page``: Called by the VM when isolating a movable non-lru page.
- If page is successfully isolated, VM marks the page as PG_isolated
- via __SetPageIsolated.
-
-- ``migrate_page``: This is used to compact the physical memory usage.
- If the VM wants to relocate a page (maybe off a memory card
- that is signalling imminent failure) it will pass a new page
- and an old page to this function. migrate_page should
- transfer any private data across and update any references
- that it has to the page.
-
-- ``putback_page``: Called by the VM when isolated page's migration fails.
-
-- ``launder_page``: Called before freeing a page - it writes back the dirty page. To
- prevent redirtying the page, it is kept locked during the whole
- operation.
-
-- ``is_partially_uptodate``: Called by the VM when reading a file through the
- pagecache when the underlying blocksize != pagesize. If the required
- block is up to date then the read can complete without needing the IO
- to bring the whole page up to date.
-
-- ``is_dirty_writeback``: Called by the VM when attempting to reclaim a page.
- The VM uses dirty and writeback information to determine if it needs
- to stall to allow flushers a chance to complete some IO. Ordinarily
- it can use PageDirty and PageWriteback but some filesystems have
- more complex state (unstable pages in NFS prevent reclaim) or
- do not set those flags due to locking problems. This callback
- allows a filesystem to indicate to the VM if a page should be
- treated as dirty or writeback for the purposes of stalling.
-
-- ``error_remove_page``: normally set to generic_error_remove_page if truncation
- is ok for this address space. Used for memory failure handling.
- Setting this implies you deal with pages going away under you,
- unless you have them locked or reference counts increased.
+ direct_IO - that is IO requests which bypass the page cache and
+ transfer data directly between the storage and the application's
+ address space.
+
+- ``isolate_page``: Called by the VM when isolating a movable non-lru
+ page. If page is successfully isolated, VM marks the page as
+ PG_isolated via __SetPageIsolated.
+
+- ``migrate_page``: This is used to compact the physical memory usage.
+ If the VM wants to relocate a page (maybe off a memory card that is
+ signalling imminent failure) it will pass a new page and an old page
+ to this function. migrate_page should transfer any private data
+ across and update any references that it has to the page.
+
+- ``putback_page``: Called by the VM when isolated page's migration
+ fails.
+
+- ``launder_page``: Called before freeing a page - it writes back the
+ dirty page. To prevent redirtying the page, it is kept locked during
+ the whole operation.
+
+- ``is_partially_uptodate``: Called by the VM when reading a file
+ through the pagecache when the underlying blocksize != pagesize. If
+ the required block is up to date then the read can complete without
+ needing the IO to bring the whole page up to date.
+
+- ``is_dirty_writeback``: Called by the VM when attempting to reclaim a
+ page. The VM uses dirty and writeback information to determine if it
+ needs to stall to allow flushers a chance to complete some IO.
+ Ordinarily it can use PageDirty and PageWriteback but some filesystems
+ have more complex state (unstable pages in NFS prevent reclaim) or do
+ not set those flags due to locking problems. This callback allows a
+ filesystem to indicate to the VM if a page should be treated as dirty
+ or writeback for the purposes of stalling.
+
+- ``error_remove_page``: normally set to generic_error_remove_page if
+ truncation is ok for this address space. Used for memory failure
+ handling. Setting this implies you deal with pages going away under
+ you, unless you have them locked or reference counts increased.
- ``swap_activate``: Called when swapon is used on a file to allocate
- space if necessary and pin the block lookup information in
- memory. A return value of zero indicates success,
- in which case this file can be used to back swapspace.
+ space if necessary and pin the block lookup information in memory. A
+ return value of zero indicates success, in which case this file can be
+ used to back swapspace.
-- ``swap_deactivate``: Called during swapoff on files where swap_activate
- was successful.
+- ``swap_deactivate``: Called during swapoff on files where
+ swap_activate was successful.
The File Object
@@ -908,87 +902,93 @@ This describes how the VFS can manipulate an open file. As of kernel
Again, all methods are called without any locks being held, unless
otherwise noted.
-- ``llseek``: called when the VFS needs to move the file position index
+- ``llseek``: called when the VFS needs to move the file position index.
-- ``read``: called by read(2) and related system calls
+- ``read``: called by read(2) and related system calls.
-- ``read_iter``: possibly asynchronous read with iov_iter as destination
+- ``read_iter``: possibly asynchronous read with iov_iter as
+ destination.
-- ``write``: called by write(2) and related system calls
+- ``write``: called by write(2) and related system calls.
-- ``write_iter``: possibly asynchronous write with iov_iter as source
+- ``write_iter``: possibly asynchronous write with iov_iter as source.
-- ``iopoll``: called when aio wants to poll for completions on HIPRI iocbs
+- ``iopoll``: called when aio wants to poll for completions on HIPRI
+ iocbs.
-- ``iterate_shared``: called when the VFS needs to read the directory contents
- when filesystem supports concurrent dir iterators
+- ``iterate``: called when the VFS needs to read the directory contents.
+
+- ``iterate_shared``: called when the VFS needs to read the directory
+ contents when filesystem supports concurrent dir iterators.
- ``poll``: called by the VFS when a process wants to check if there is
- activity on this file and (optionally) go to sleep until there
- is activity. Called by the select(2) and poll(2) system calls
+ activity on this file and (optionally) go to sleep until there is
+ activity. Called by the select(2) and poll(2) system calls.
- ``unlocked_ioctl``: called by the ioctl(2) system call.
-- ``compat_ioctl``: called by the ioctl(2) system call when 32 bit system calls
- are used on 64 bit kernels.
+- ``compat_ioctl``: called by the ioctl(2) system call when 32 bit
+ system calls are used on 64 bit kernels.
-- ``mmap``: called by the mmap(2) system call
+- ``mmap``: called by the mmap(2) system call.
-- ``open``: called by the VFS when an inode should be opened. When the VFS
- opens a file, it creates a new "struct file". It then calls the
- open method for the newly allocated file structure. You might
- think that the open method really belongs in
- "struct inode_operations", and you may be right. I think it's
- done the way it is because it makes filesystems simpler to
- implement. The open() method is a good place to initialize the
- "private_data" member in the file structure if you want to point
- to a device structure
+- ``open``: called by the VFS when an inode should be opened. When the
+ VFS opens a file, it creates a new "struct file". It then calls the
+ open method for the newly allocated file structure. You might think
+ that the open method really belongs in "struct inode_operations", and
+ you may be right. I think it's done the way it is because it makes
+ filesystems simpler to implement. The open() method is a good place
+ to initialize the "private_data" member in the file structure if you
+ want to point to a device structure.
-- ``flush``: called by the close(2) system call to flush a file
+- ``flush``: called by the close(2) system call to flush a file.
-- ``release``: called when the last reference to an open file is closed
+- ``release``: called when the last reference to an open file is closed.
-- ``fsync``: called by the fsync(2) system call. Also see the section above
- entitled "Handling errors during writeback".
+- ``fsync``: called by the fsync(2) system call. Also see the section
+ above entitled "Handling errors during writeback".
- ``fasync``: called by the fcntl(2) system call when asynchronous
- (non-blocking) mode is enabled for a file
+ (non-blocking) mode is enabled for a file.
-- ``lock``: called by the fcntl(2) system call for F_GETLK, F_SETLK, and F_SETLKW
- commands
+- ``lock``: called by the fcntl(2) system call for F_GETLK, F_SETLK, and
+ F_SETLKW commands.
-- ``get_unmapped_area``: called by the mmap(2) system call
+- ``get_unmapped_area``: called by the mmap(2) system call.
-- ``check_flags``: called by the fcntl(2) system call for F_SETFL command
+- ``check_flags``: called by the fcntl(2) system call for F_SETFL
+ command.
-- ``flock``: called by the flock(2) system call
+- ``flock``: called by the flock(2) system call.
-- ``splice_write``: called by the VFS to splice data from a pipe to a file. This
- method is used by the splice(2) system call
+- ``splice_write``: called by the VFS to splice data from a pipe to a
+ file. This method is used by the splice(2) system call.
-- ``splice_read``: called by the VFS to splice data from file to a pipe. This
- method is used by the splice(2) system call
+- ``splice_read``: called by the VFS to splice data from file to a pipe.
+ This method is used by the splice(2) system call
-- ``setlease``: called by the VFS to set or release a file lock lease. setlease
- implementations should call generic_setlease to record or remove
- the lease in the inode after setting it.
+- ``setlease``: called by the VFS to set or release a file lock lease.
+ setlease implementations should call generic_setlease to record or
+ remove the lease in the inode after setting it.
-- ``fallocate``: called by the VFS to preallocate blocks or punch a hole.
+- ``fallocate``: called by the VFS to preallocate blocks or punch a
+ hole.
- ``copy_file_range``: called by the copy_file_range(2) system call.
-- ``remap_file_range``: called by the ioctl(2) system call for FICLONERANGE and
- FICLONE and FIDEDUPERANGE commands to remap file ranges. An
- implementation should remap len bytes at pos_in of the source file into
- the dest file at pos_out. Implementations must handle callers passing
- in len == 0; this means "remap to the end of the source file". The
- return value should the number of bytes remapped, or the usual
- negative error code if errors occurred before any bytes were remapped.
- The remap_flags parameter accepts REMAP_FILE_* flags. If
- REMAP_FILE_DEDUP is set then the implementation must only remap if the
- requested file ranges have identical contents. If REMAP_CAN_SHORTEN is
- set, the caller is ok with the implementation shortening the request
- length to satisfy alignment or EOF requirements (or any other reason).
+- ``remap_file_range``: called by the ioctl(2) system call for
+ FICLONERANGE and FICLONE and FIDEDUPERANGE commands to remap file
+ ranges. An implementation should remap len bytes at pos_in of the
+ source file into the dest file at pos_out. Implementations must
+ handle callers passing in len == 0; this means "remap to the end of
+ the source file". The return value should the number of bytes
+ remapped, or the usual negative error code if errors occurred before
+ any bytes were remapped. The remap_flags parameter accepts
+ REMAP_FILE_* flags. If REMAP_FILE_DEDUP is set then the
+ implementation must only remap if the requested file ranges have
+ identical contents. If REMAP_CAN_SHORTEN is set, the caller is ok
+ with the implementation shortening the request length to satisfy
+ alignment or EOF requirements (or any other reason).
- ``fadvise``: possibly called by the fadvise64() system call.
@@ -1035,146 +1035,147 @@ defined:
struct dentry *(*d_real)(struct dentry *, const struct inode *);
};
-- ``d_revalidate``: called when the VFS needs to revalidate a dentry. This
- is called whenever a name look-up finds a dentry in the
- dcache. Most local filesystems leave this as NULL, because all their
- dentries in the dcache are valid. Network filesystems are different
- since things can change on the server without the client necessarily
- being aware of it.
+- ``d_revalidate``: called when the VFS needs to revalidate a dentry.
+ This is called whenever a name look-up finds a dentry in the dcache.
+ Most local filesystems leave this as NULL, because all their dentries
+ in the dcache are valid. Network filesystems are different since
+ things can change on the server without the client necessarily being
+ aware of it.
- This function should return a positive value if the dentry is still
- valid, and zero or a negative error code if it isn't.
+ This function should return a positive value if the dentry is still
+ valid, and zero or a negative error code if it isn't.
- d_revalidate may be called in rcu-walk mode (flags & LOOKUP_RCU).
- If in rcu-walk mode, the filesystem must revalidate the dentry without
- blocking or storing to the dentry, d_parent and d_inode should not be
- used without care (because they can change and, in d_inode case, even
- become NULL under us).
+ d_revalidate may be called in rcu-walk mode (flags & LOOKUP_RCU). If
+ in rcu-walk mode, the filesystem must revalidate the dentry without
+ blocking or storing to the dentry, d_parent and d_inode should not be
+ used without care (because they can change and, in d_inode case, even
+ become NULL under us).
- If a situation is encountered that rcu-walk cannot handle, return
- -ECHILD and it will be called again in ref-walk mode.
+ If a situation is encountered that rcu-walk cannot handle, return
+ -ECHILD and it will be called again in ref-walk mode.
-- ``d_weak_revalidate``: called when the VFS needs to revalidate a "jumped" dentry.
- This is called when a path-walk ends at dentry that was not acquired by
- doing a lookup in the parent directory. This includes "/", "." and "..",
- as well as procfs-style symlinks and mountpoint traversal.
+- ``d_weak_revalidate``: called when the VFS needs to revalidate a
+ "jumped" dentry. This is called when a path-walk ends at dentry that
+ was not acquired by doing a lookup in the parent directory. This
+ includes "/", "." and "..", as well as procfs-style symlinks and
+ mountpoint traversal.
- In this case, we are less concerned with whether the dentry is still
- fully correct, but rather that the inode is still valid. As with
- d_revalidate, most local filesystems will set this to NULL since their
- dcache entries are always valid.
+ In this case, we are less concerned with whether the dentry is still
+ fully correct, but rather that the inode is still valid. As with
+ d_revalidate, most local filesystems will set this to NULL since their
+ dcache entries are always valid.
- This function has the same return code semantics as d_revalidate.
+ This function has the same return code semantics as d_revalidate.
- d_weak_revalidate is only called after leaving rcu-walk mode.
+ d_weak_revalidate is only called after leaving rcu-walk mode.
-- ``d_hash``: called when the VFS adds a dentry to the hash table. The first
- dentry passed to d_hash is the parent directory that the name is
- to be hashed into.
+- ``d_hash``: called when the VFS adds a dentry to the hash table. The
+ first dentry passed to d_hash is the parent directory that the name is
+ to be hashed into.
- Same locking and synchronisation rules as d_compare regarding
- what is safe to dereference etc.
+ Same locking and synchronisation rules as d_compare regarding what is
+ safe to dereference etc.
-- ``d_compare``: called to compare a dentry name with a given name. The first
- dentry is the parent of the dentry to be compared, the second is
- the child dentry. len and name string are properties of the dentry
- to be compared. qstr is the name to compare it with.
+- ``d_compare``: called to compare a dentry name with a given name. The
+ first dentry is the parent of the dentry to be compared, the second is
+ the child dentry. len and name string are properties of the dentry to
+ be compared. qstr is the name to compare it with.
- Must be constant and idempotent, and should not take locks if
- possible, and should not or store into the dentry.
- Should not dereference pointers outside the dentry without
- lots of care (eg. d_parent, d_inode, d_name should not be used).
+ Must be constant and idempotent, and should not take locks if
+ possible, and should not or store into the dentry. Should not
+ dereference pointers outside the dentry without lots of care (eg.
+ d_parent, d_inode, d_name should not be used).
- However, our vfsmount is pinned, and RCU held, so the dentries and
- inodes won't disappear, neither will our sb or filesystem module.
- ->d_sb may be used.
+ However, our vfsmount is pinned, and RCU held, so the dentries and
+ inodes won't disappear, neither will our sb or filesystem module.
+ ->d_sb may be used.
- It is a tricky calling convention because it needs to be called under
- "rcu-walk", ie. without any locks or references on things.
+ It is a tricky calling convention because it needs to be called under
+ "rcu-walk", ie. without any locks or references on things.
-- ``d_delete``: called when the last reference to a dentry is dropped and the
- dcache is deciding whether or not to cache it. Return 1 to delete
- immediately, or 0 to cache the dentry. Default is NULL which means to
- always cache a reachable dentry. d_delete must be constant and
- idempotent.
+- ``d_delete``: called when the last reference to a dentry is dropped
+ and the dcache is deciding whether or not to cache it. Return 1 to
+ delete immediately, or 0 to cache the dentry. Default is NULL which
+ means to always cache a reachable dentry. d_delete must be constant
+ and idempotent.
-- ``d_init``: called when a dentry is allocated
+- ``d_init``: called when a dentry is allocated.
-- ``d_release``: called when a dentry is really deallocated
+- ``d_release``: called when a dentry is really deallocated.
- ``d_iput``: called when a dentry loses its inode (just prior to its
- being deallocated). The default when this is NULL is that the
- VFS calls iput(). If you define this method, you must call
- iput() yourself
+ being deallocated). The default when this is NULL is that the VFS
+ calls iput(). If you define this method, you must call iput()
+ yourself.
- ``d_dname``: called when the pathname of a dentry should be generated.
- Useful for some pseudo filesystems (sockfs, pipefs, ...) to delay
- pathname generation. (Instead of doing it when dentry is created,
- it's done only when the path is needed.). Real filesystems probably
- dont want to use it, because their dentries are present in global
- dcache hash, so their hash should be an invariant. As no lock is
- held, d_dname() should not try to modify the dentry itself, unless
- appropriate SMP safety is used. CAUTION : d_path() logic is quite
- tricky. The correct way to return for example "Hello" is to put it
- at the end of the buffer, and returns a pointer to the first char.
- dynamic_dname() helper function is provided to take care of this.
-
- .. code-block:: c
-
- static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
- {
- return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
- dentry->d_inode->i_ino);
- }
-
-- ``d_automount``: called when an automount dentry is to be traversed (optional).
- This should create a new VFS mount record and return the record to the
- caller. The caller is supplied with a path parameter giving the
- automount directory to describe the automount target and the parent
- VFS mount record to provide inheritable mount parameters. NULL should
- be returned if someone else managed to make the automount first. If
- the vfsmount creation failed, then an error code should be returned.
- If -EISDIR is returned, then the directory will be treated as an
- ordinary directory and returned to pathwalk to continue walking.
-
- If a vfsmount is returned, the caller will attempt to mount it on the
- mountpoint and will remove the vfsmount from its expiration list in
- the case of failure. The vfsmount should be returned with 2 refs on
- it to prevent automatic expiration - the caller will clean up the
- additional ref.
-
- This function is only used if DCACHE_NEED_AUTOMOUNT is set on the
- dentry. This is set by __d_instantiate() if S_AUTOMOUNT is set on the
- inode being added.
-
-- ``d_manage``: called to allow the filesystem to manage the transition from a
- dentry (optional). This allows autofs, for example, to hold up clients
- waiting to explore behind a 'mountpoint' while letting the daemon go
- past and construct the subtree there. 0 should be returned to let the
- calling process continue. -EISDIR can be returned to tell pathwalk to
- use this directory as an ordinary directory and to ignore anything
- mounted on it and not to check the automount flag. Any other error
- code will abort pathwalk completely.
-
- If the 'rcu_walk' parameter is true, then the caller is doing a
- pathwalk in RCU-walk mode. Sleeping is not permitted in this mode,
- and the caller can be asked to leave it and call again by returning
- -ECHILD. -EISDIR may also be returned to tell pathwalk to
- ignore d_automount or any mounts.
-
- This function is only used if DCACHE_MANAGE_TRANSIT is set on the
- dentry being transited from.
-
-- ``d_real``: overlay/union type filesystems implement this method to return one of
- the underlying dentries hidden by the overlay. It is used in two
- different modes:
-
- Called from file_dentry() it returns the real dentry matching the inode
- argument. The real dentry may be from a lower layer already copied up,
- but still referenced from the file. This mode is selected with a
- non-NULL inode argument.
-
- With NULL inode the topmost real underlying dentry is returned.
+ Useful for some pseudo filesystems (sockfs, pipefs, ...) to delay
+ pathname generation. (Instead of doing it when dentry is created,
+ it's done only when the path is needed.). Real filesystems probably
+ dont want to use it, because their dentries are present in global
+ dcache hash, so their hash should be an invariant. As no lock is
+ held, d_dname() should not try to modify the dentry itself, unless
+ appropriate SMP safety is used. CAUTION : d_path() logic is quite
+ tricky. The correct way to return for example "Hello" is to put it at
+ the end of the buffer, and returns a pointer to the first char.
+ dynamic_dname() helper function is provided to take care of this.
+
+ .. code-block:: c
+
+ static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
+ {
+ return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+ dentry->d_inode->i_ino);
+ }
+
+- ``d_automount``: called when an automount dentry is to be traversed
+ (optional). This should create a new VFS mount record and return the
+ record to the caller. The caller is supplied with a path parameter
+ giving the automount directory to describe the automount target and
+ the parent VFS mount record to provide inheritable mount parameters.
+ NULL should be returned if someone else managed to make the automount
+ first. If the vfsmount creation failed, then an error code should be
+ returned. If -EISDIR is returned, then the directory will be treated
+ as an ordinary directory and returned to pathwalk to continue walking.
+
+ If a vfsmount is returned, the caller will attempt to mount it on the
+ mountpoint and will remove the vfsmount from its expiration list in
+ the case of failure. The vfsmount should be returned with 2 refs on
+ it to prevent automatic expiration - the caller will clean up the
+ additional ref.
+
+ This function is only used if DCACHE_NEED_AUTOMOUNT is set on the
+ dentry. This is set by __d_instantiate() if S_AUTOMOUNT is set on the
+ inode being added.
+
+- ``d_manage``: called to allow the filesystem to manage the transition
+ from a dentry (optional). This allows autofs, for example, to hold up
+ clients waiting to explore behind a 'mountpoint' while letting the
+ daemon go past and construct the subtree there. 0 should be returned
+ to let the calling process continue. -EISDIR can be returned to tell
+ pathwalk to use this directory as an ordinary directory and to ignore
+ anything mounted on it and not to check the automount flag. Any other
+ error code will abort pathwalk completely.
+
+ If the 'rcu_walk' parameter is true, then the caller is doing a
+ pathwalk in RCU-walk mode. Sleeping is not permitted in this mode,
+ and the caller can be asked to leave it and call again by returning
+ -ECHILD. -EISDIR may also be returned to tell pathwalk to ignore
+ d_automount or any mounts.
+
+ This function is only used if DCACHE_MANAGE_TRANSIT is set on the
+ dentry being transited from.
+
+- ``d_real``: overlay/union type filesystems implement this method to
+ return one of the underlying dentries hidden by the overlay. It is
+ used in two different modes:
+
+ Called from file_dentry() it returns the real dentry matching the
+ inode argument. The real dentry may be from a lower layer already
+ copied up, but still referenced from the file. This mode is selected
+ with a non-NULL inode argument.
+
+ With NULL inode the topmost real underlying dentry is returned.
Each dentry has a pointer to its parent dentry, as well as a hash list
of child dentries. Child dentries are basically like files in a
@@ -1188,39 +1189,38 @@ There are a number of functions defined which permit a filesystem to
manipulate dentries:
- ``dget``: open a new handle for an existing dentry (this just increments
- the usage count)
+ the usage count).
- ``dput``: close a handle for a dentry (decrements the usage count). If
- the usage count drops to 0, and the dentry is still in its
- parent's hash, the "d_delete" method is called to check whether
- it should be cached. If it should not be cached, or if the dentry
- is not hashed, it is deleted. Otherwise cached dentries are put
- into an LRU list to be reclaimed on memory shortage.
+ the usage count drops to 0, and the dentry is still in its parent's hash,
+ the "d_delete" method is called to check whether it should be cached. If
+ it should not be cached, or if the dentry is not hashed, it is deleted.
+ Otherwise cached dentries are put into an LRU list to be reclaimed on
+ memory shortage.
- ``d_drop``: this unhashes a dentry from its parents hash list. A
- subsequent call to dput() will deallocate the dentry if its
- usage count drops to 0
+ subsequent call to dput() will deallocate the dentry if its usage count
+ drops to 0.
- ``d_delete``: delete a dentry. If there are no other open references to
- the dentry then the dentry is turned into a negative dentry
- (the d_iput() method is called). If there are other
- references, then d_drop() is called instead
+ the dentry then the dentry is turned into a negative dentry (the d_iput()
+ method is called). If there are other references, then d_drop() is
+ called instead.
- ``d_add``: add a dentry to its parents hash list and then calls
- d_instantiate()
+ d_instantiate().
- ``d_instantiate``: add a dentry to the alias hash list for the inode and
- updates the "d_inode" member. The "i_count" member in the
- inode structure should be set/incremented. If the inode
- pointer is NULL, the dentry is called a "negative
- dentry". This function is commonly called when an inode is
- created for an existing negative dentry
+ updates the "d_inode" member. The "i_count" member in the inode
+ structure should be set/incremented. If the inode pointer is NULL, the
+ dentry is called a "negative dentry". This function is commonly called
+ when an inode is created for an existing negative dentry.
-- ``d_lookup``: look up a dentry given its parent and path name component
- It looks up the child of that given name from the dcache
- hash table. If it is found, the reference count is incremented
- and the dentry is returned. The caller must use dput()
- to free the dentry when it finishes using it.
+- ``d_lookup``: look up a dentry given its parent and path name component.
+ It looks up the child of that given name from the dcache hash table. If
+ it is found, the reference count is incremented and the dentry is
+ returned. The caller must use dput() to free the dentry when it finishes
+ using it.
Mount Options
@@ -1234,8 +1234,8 @@ On mount and remount the filesystem is passed a string containing a
comma separated list of mount options. The options can have either of
these forms:
- option
- option=value
+- option
+- option=value
The <linux/parser.h> header defines an API that helps parse these
options. There are plenty of examples on how to use it in existing
@@ -1248,11 +1248,11 @@ Showing options
If a filesystem accepts mount options, it must define show_options() to
show all the currently active options. The rules are:
- - options MUST be shown which are not default or their values differ
- from the default
+- options MUST be shown which are not default or their values differ from
+ the default.
- - options MAY be shown which are enabled by default or have their
- default value
+- options MAY be shown which are enabled by default or have their default
+ value.
Options used only internally between a mount helper and the kernel (such
as file descriptors), or which only have an effect during the mounting
--
2.21.0
Sphinx emits a warning because of the use of a * (C pointer construct)
within the document. We can prevent this by guarding the C source code
with back ticks.
Use backticks to guard star (C pointer).
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.rst | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 12b8e90403eb..8ad2507b3df6 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -355,7 +355,7 @@ Extended attributes are name:value pairs.
When none of the xattr handlers of a filesystem match the specified
attribute name or when a filesystem doesn't support extended attributes,
-the various *xattr(2) system calls return -EOPNOTSUPP.
+the various ``*xattr(2)`` system calls return -EOPNOTSUPP.
The Inode Object
@@ -722,7 +722,7 @@ cache in your filesystem. The following members are defined:
out properly.
The filesystem must return the locked pagecache page for the specified
- offset, in *pagep, for the caller to write into.
+ offset, in ``*pagep``, for the caller to write into.
It must be able to cope with short writes (where the length passed to
write_begin is greater than the number of bytes copied into the page).
--
2.21.0
While converting to RST a few minor grammar mistakes were noticed. Fix
these now the conversion is done.
Fix minor grammar mistakes.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.rst | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index bd8f7891f44b..12b8e90403eb 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -1111,13 +1111,13 @@ defined:
- ``d_dname``: called when the pathname of a dentry should be generated.
Useful for some pseudo filesystems (sockfs, pipefs, ...) to delay
pathname generation. (Instead of doing it when dentry is created,
- it's done only when the path is needed.). Real filesystems probably
- dont want to use it, because their dentries are present in global
+ it's done only when the path is needed.) Real filesystems probably
+ don't want to use it, because their dentries are present in global
dcache hash, so their hash should be an invariant. As no lock is
held, d_dname() should not try to modify the dentry itself, unless
appropriate SMP safety is used. CAUTION : d_path() logic is quite
tricky. The correct way to return for example "Hello" is to put it at
- the end of the buffer, and returns a pointer to the first char.
+ the end of the buffer, and return a pointer to the first char.
dynamic_dname() helper function is provided to take care of this.
.. code-block:: c
@@ -1211,7 +1211,7 @@ manipulate dentries:
d_instantiate().
- ``d_instantiate``: add a dentry to the alias hash list for the inode and
- updates the "d_inode" member. The "i_count" member in the inode
+ update the "d_inode" member. The "i_count" member in the inode
structure should be set/incremented. If the inode pointer is NULL, the
dentry is called a "negative dentry". This function is commonly called
when an inode is created for an existing negative dentry.
--
2.21.0
Currently there are a bunch of lists within the text file (descriptions
of function parameters etc.). In preparation for converting document to
RST format use an acceptable RST list character ('-').
Use RST list character for lists.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 254 +++++++++++++++---------------
1 file changed, 127 insertions(+), 127 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 43b18bafbc20..6e709815a6dd 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -123,34 +123,34 @@ struct file_system_type {
struct lock_class_key s_umount_key;
};
- name: the name of the filesystem type, such as "ext2", "iso9660",
+- name: the name of the filesystem type, such as "ext2", "iso9660",
"msdos" and so on
- fs_flags: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.)
+- fs_flags: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.)
- mount: the method to call when a new instance of this
+- mount: the method to call when a new instance of this
filesystem should be mounted
- kill_sb: the method to call when an instance of this filesystem
+- kill_sb: the method to call when an instance of this filesystem
should be shut down
- owner: for internal VFS use: you should initialize this to THIS_MODULE in
+- owner: for internal VFS use: you should initialize this to THIS_MODULE in
most cases.
- next: for internal VFS use: you should initialize this to NULL
+- next: for internal VFS use: you should initialize this to NULL
- s_lock_key, s_umount_key: lockdep-specific
+- s_lock_key, s_umount_key: lockdep-specific
The mount() method has the following arguments:
- struct file_system_type *fs_type: describes the filesystem, partly initialized
+- struct file_system_type *fs_type: describes the filesystem, partly initialized
by the specific filesystem code
- int flags: mount flags
+- int flags: mount flags
- const char *dev_name: the device name we are mounting.
+- const char *dev_name: the device name we are mounting.
- void *data: arbitrary mount options, usually comes as an ASCII
+- void *data: arbitrary mount options, usually comes as an ASCII
string (see "Mount Options" section)
The mount() method must return the root dentry of the tree requested by
@@ -176,22 +176,22 @@ implementation.
Usually, a filesystem uses one of the generic mount() implementations
and provides a fill_super() callback instead. The generic variants are:
- mount_bdev: mount a filesystem residing on a block device
+- mount_bdev: mount a filesystem residing on a block device
- mount_nodev: mount a filesystem that is not backed by a device
+- mount_nodev: mount a filesystem that is not backed by a device
- mount_single: mount a filesystem which shares the instance between
+- mount_single: mount a filesystem which shares the instance between
all mounts
A fill_super() callback implementation has the following arguments:
- struct super_block *sb: the superblock structure. The callback
+- struct super_block *sb: the superblock structure. The callback
must initialize this properly.
- void *data: arbitrary mount options, usually comes as an ASCII
+- void *data: arbitrary mount options, usually comes as an ASCII
string (see "Mount Options" section)
- int silent: whether or not to be silent on error
+- int silent: whether or not to be silent on error
The Superblock Object
@@ -236,24 +236,24 @@ noted. This means that most methods can block safely. All methods are
only called from a process context (i.e. not from an interrupt handler
or bottom half).
- alloc_inode: this method is called by alloc_inode() to allocate memory
+- alloc_inode: this method is called by alloc_inode() to allocate memory
for struct inode and initialize it. If this function is not
defined, a simple 'struct inode' is allocated. Normally
alloc_inode will be used to allocate a larger structure which
contains a 'struct inode' embedded within it.
- destroy_inode: this method is called by destroy_inode() to release
+- destroy_inode: this method is called by destroy_inode() to release
resources allocated for struct inode. It is only required if
->alloc_inode was defined and simply undoes anything done by
->alloc_inode.
- dirty_inode: this method is called by the VFS to mark an inode dirty.
+- dirty_inode: this method is called by the VFS to mark an inode dirty.
- write_inode: this method is called when the VFS needs to write an
+- write_inode: this method is called when the VFS needs to write an
inode to disc. The second parameter indicates whether the write
should be synchronous or not, not all filesystems check this flag.
- drop_inode: called when the last access to the inode is dropped,
+- drop_inode: called when the last access to the inode is dropped,
with the inode->i_lock spinlock held.
This method should be either NULL (normal UNIX filesystem
@@ -266,43 +266,43 @@ or bottom half).
but does not have the races that the "force_delete()" approach
had.
- delete_inode: called when the VFS wants to delete an inode
+- delete_inode: called when the VFS wants to delete an inode
- put_super: called when the VFS wishes to free the superblock
+- put_super: called when the VFS wishes to free the superblock
(i.e. unmount). This is called with the superblock lock held
- sync_fs: called when VFS is writing out all dirty data associated with
+- sync_fs: called when VFS is writing out all dirty data associated with
a superblock. The second parameter indicates whether the method
should wait until the write out has been completed. Optional.
- freeze_fs: called when VFS is locking a filesystem and
+- freeze_fs: called when VFS is locking a filesystem and
forcing it into a consistent state. This method is currently
used by the Logical Volume Manager (LVM).
- unfreeze_fs: called when VFS is unlocking a filesystem and making it writable
+- unfreeze_fs: called when VFS is unlocking a filesystem and making it writable
again.
- statfs: called when the VFS needs to get filesystem statistics.
+- statfs: called when the VFS needs to get filesystem statistics.
- remount_fs: called when the filesystem is remounted. This is called
+- remount_fs: called when the filesystem is remounted. This is called
with the kernel lock held
- clear_inode: called then the VFS clears the inode. Optional
+- clear_inode: called then the VFS clears the inode. Optional
- umount_begin: called when the VFS is unmounting a filesystem.
+- umount_begin: called when the VFS is unmounting a filesystem.
- show_options: called by the VFS to show mount options for
+- show_options: called by the VFS to show mount options for
/proc/<pid>/mounts. (see "Mount Options" section)
- quota_read: called by the VFS to read from filesystem quota file.
+- quota_read: called by the VFS to read from filesystem quota file.
- quota_write: called by the VFS to write to filesystem quota file.
+- quota_write: called by the VFS to write to filesystem quota file.
- nr_cached_objects: called by the sb cache shrinking function for the
+- nr_cached_objects: called by the sb cache shrinking function for the
filesystem to return the number of freeable cached objects it contains.
Optional.
- free_cache_objects: called by the sb cache shrinking function for the
+- free_cache_objects: called by the sb cache shrinking function for the
filesystem to scan the number of objects indicated to try to free them.
Optional, but any filesystem implementing this method needs to also
implement ->nr_cached_objects for it to be called correctly.
@@ -330,20 +330,20 @@ On filesystems that support extended attributes (xattrs), the s_xattr
superblock field points to a NULL-terminated array of xattr handlers.
Extended attributes are name:value pairs.
- name: Indicates that the handler matches attributes with the specified name
+- name: Indicates that the handler matches attributes with the specified name
(such as "system.posix_acl_access"); the prefix field must be NULL.
- prefix: Indicates that the handler matches all attributes with the specified
+- prefix: Indicates that the handler matches all attributes with the specified
name prefix (such as "user."); the name field must be NULL.
- list: Determine if attributes matching this xattr handler should be listed
+- list: Determine if attributes matching this xattr handler should be listed
for a particular dentry. Used by some listxattr implementations like
generic_listxattr.
- get: Called by the VFS to get the value of a particular extended attribute.
+- get: Called by the VFS to get the value of a particular extended attribute.
This method is called by the getxattr(2) system call.
- set: Called by the VFS to set the value of a particular extended attribute.
+- set: Called by the VFS to set the value of a particular extended attribute.
When the new value is NULL, called to remove a particular extended
attribute. This method is called by the the setxattr(2) and
removexattr(2) system calls.
@@ -393,13 +393,13 @@ struct inode_operations {
Again, all methods are called without any locks being held, unless
otherwise noted.
- create: called by the open(2) and creat(2) system calls. Only
+- create: called by the open(2) and creat(2) system calls. Only
required if you want to support regular files. The dentry you
get should not have an inode (i.e. it should be a negative
dentry). Here you will probably call d_instantiate() with the
dentry and the newly created inode
- lookup: called when the VFS needs to look up an inode in a parent
+- lookup: called when the VFS needs to look up an inode in a parent
directory. The name to look for is found in the dentry. This
method must call d_add() to insert the found inode into the
dentry. The "i_count" field in the inode structure should be
@@ -413,31 +413,31 @@ otherwise noted.
to a struct "dentry_operations".
This method is called with the directory inode semaphore held
- link: called by the link(2) system call. Only required if you want
+- link: called by the link(2) system call. Only required if you want
to support hard links. You will probably need to call
d_instantiate() just as you would in the create() method
- unlink: called by the unlink(2) system call. Only required if you
+- unlink: called by the unlink(2) system call. Only required if you
want to support deleting inodes
- symlink: called by the symlink(2) system call. Only required if you
+- symlink: called by the symlink(2) system call. Only required if you
want to support symlinks. You will probably need to call
d_instantiate() just as you would in the create() method
- mkdir: called by the mkdir(2) system call. Only required if you want
+- mkdir: called by the mkdir(2) system call. Only required if you want
to support creating subdirectories. You will probably need to
call d_instantiate() just as you would in the create() method
- rmdir: called by the rmdir(2) system call. Only required if you want
+- rmdir: called by the rmdir(2) system call. Only required if you want
to support deleting subdirectories
- mknod: called by the mknod(2) system call to create a device (char,
+- mknod: called by the mknod(2) system call to create a device (char,
block) inode or a named pipe (FIFO) or socket. Only required
if you want to support creating these types of inodes. You
will probably need to call d_instantiate() just as you would
in the create() method
- rename: called by the rename(2) system call to rename the object to
+- rename: called by the rename(2) system call to rename the object to
have the parent and name given by the second inode and dentry.
The filesystem must return -EINVAL for any unsupported or
@@ -451,7 +451,7 @@ otherwise noted.
exist; this is checked by the VFS. Unlike plain rename,
source and target may be of different type.
- get_link: called by the VFS to follow a symbolic link to the
+- get_link: called by the VFS to follow a symbolic link to the
inode it points to. Only required if you want to support
symbolic links. This method returns the symlink body
to traverse (and possibly resets the current position with
@@ -465,13 +465,13 @@ otherwise noted.
argument. If request can't be handled without leaving RCU mode,
have it return ERR_PTR(-ECHILD).
- readlink: this is now just an override for use by readlink(2) for the
+- readlink: this is now just an override for use by readlink(2) for the
cases when ->get_link uses nd_jump_link() or object is not in
fact a symlink. Normally filesystems should only implement
->get_link for symlinks and readlink(2) will automatically use
that.
- permission: called by the VFS to check for access rights on a POSIX-like
+- permission: called by the VFS to check for access rights on a POSIX-like
filesystem.
May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
@@ -481,20 +481,20 @@ otherwise noted.
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
- setattr: called by the VFS to set attributes for a file. This method
+- setattr: called by the VFS to set attributes for a file. This method
is called by chmod(2) and related system calls.
- getattr: called by the VFS to get attributes of a file. This method
+- getattr: called by the VFS to get attributes of a file. This method
is called by stat(2) and related system calls.
- listxattr: called by the VFS to list all extended attributes for a
+- listxattr: called by the VFS to list all extended attributes for a
given file. This method is called by the listxattr(2) system call.
- update_time: called by the VFS to update a specific time or the i_version of
+- update_time: called by the VFS to update a specific time or the i_version of
an inode. If this is not defined the VFS will update the inode itself
and call mark_inode_dirty_sync.
- atomic_open: called on the last component of an open. Using this optional
+- atomic_open: called on the last component of an open. Using this optional
method the filesystem can look up, possibly create and open the file in
one atomic operation. If it wants to leave actual opening to the
caller (e.g. if the file turned out to be a symlink, device, or just
@@ -506,7 +506,7 @@ otherwise noted.
the method must only succeed if the file didn't exist and hence FMODE_CREATED
shall always be set on success.
- tmpfile: called in the end of O_TMPFILE open(). Optional, equivalent to
+- tmpfile: called in the end of O_TMPFILE open(). Optional, equivalent to
atomically creating, opening and unlinking a file in given directory.
@@ -658,7 +658,7 @@ struct address_space_operations {
int (*swap_deactivate)(struct file *);
};
- writepage: called by the VM to write a dirty page to backing store.
+- writepage: called by the VM to write a dirty page to backing store.
This may happen for data integrity reasons (i.e. 'sync'), or
to free up memory (flush). The difference can be seen in
wbc->sync_mode.
@@ -676,7 +676,7 @@ struct address_space_operations {
See the file "Locking" for more details.
- readpage: called by the VM to read a page from backing store.
+- readpage: called by the VM to read a page from backing store.
The page will be Locked when readpage is called, and should be
unlocked and marked uptodate once the read completes.
If ->readpage discovers that it needs to unlock the page for
@@ -684,7 +684,7 @@ struct address_space_operations {
In this case, the page will be relocated, relocked and if
that all succeeds, ->readpage will be called again.
- writepages: called by the VM to write out pages associated with the
+- writepages: called by the VM to write out pages associated with the
address_space object. If wbc->sync_mode is WBC_SYNC_ALL, then
the writeback_control will specify a range of pages that must be
written out. If it is WBC_SYNC_NONE, then a nr_to_write is given
@@ -693,7 +693,7 @@ struct address_space_operations {
instead. This will choose pages from the address space that are
tagged as DIRTY and will pass them to ->writepage.
- set_page_dirty: called by the VM to set a page dirty.
+- set_page_dirty: called by the VM to set a page dirty.
This is particularly needed if an address space attaches
private data to a page, and that data needs to be updated when
a page is dirtied. This is called, for example, when a memory
@@ -701,14 +701,14 @@ struct address_space_operations {
If defined, it should set the PageDirty flag, and the
PAGECACHE_TAG_DIRTY tag in the radix tree.
- readpages: called by the VM to read pages associated with the address_space
+- readpages: called by the VM to read pages associated with the address_space
object. This is essentially just a vector version of
readpage. Instead of just one page, several pages are
requested.
readpages is only used for read-ahead, so read errors are
ignored. If anything goes wrong, feel free to give up.
- write_begin:
+- write_begin:
Called by the generic buffered write code to ask the filesystem to
prepare to write len bytes at the given offset in the file. The
address_space should check that the write will be able to complete,
@@ -732,7 +732,7 @@ struct address_space_operations {
Returns 0 on success; < 0 on failure (which is the error code), in
which case write_end is not called.
- write_end: After a successful write_begin, and data copy, write_end must
+- write_end: After a successful write_begin, and data copy, write_end must
be called. len is the original len passed to write_begin, and copied
is the amount that was able to be copied.
@@ -742,7 +742,7 @@ struct address_space_operations {
Returns < 0 on failure, otherwise the number of bytes (<= 'copied')
that were able to be copied into pagecache.
- bmap: called by the VFS to map a logical block offset within object to
+- bmap: called by the VFS to map a logical block offset within object to
physical block number. This method is used by the FIBMAP
ioctl and for working with swap-files. To be able to swap to
a file, the file must have a stable mapping to a block
@@ -750,7 +750,7 @@ struct address_space_operations {
but instead uses bmap to find out where the blocks in the file
are and uses those addresses directly.
- invalidatepage: If a page has PagePrivate set, then invalidatepage
+- invalidatepage: If a page has PagePrivate set, then invalidatepage
will be called when part or all of the page is to be removed
from the address space. This generally corresponds to either a
truncation, punch hole or a complete invalidation of the address
@@ -762,7 +762,7 @@ struct address_space_operations {
be done by calling the ->releasepage function, but in this case the
release MUST succeed.
- releasepage: releasepage is called on PagePrivate pages to indicate
+- releasepage: releasepage is called on PagePrivate pages to indicate
that the page should be freed if possible. ->releasepage
should remove any private data from the page and clear the
PagePrivate flag. If releasepage() fails for some reason, it must
@@ -783,40 +783,40 @@ struct address_space_operations {
need to ensure this. Possibly it can clear the PageUptodate
bit if it cannot free private data yet.
- freepage: freepage is called once the page is no longer visible in
+- freepage: freepage is called once the page is no longer visible in
the page cache in order to allow the cleanup of any private
data. Since it may be called by the memory reclaimer, it
should not assume that the original address_space mapping still
exists, and it should not block.
- direct_IO: called by the generic read/write routines to perform
+- direct_IO: called by the generic read/write routines to perform
direct_IO - that is IO requests which bypass the page cache
and transfer data directly between the storage and the
application's address space.
- isolate_page: Called by the VM when isolating a movable non-lru page.
+- isolate_page: Called by the VM when isolating a movable non-lru page.
If page is successfully isolated, VM marks the page as PG_isolated
via __SetPageIsolated.
- migrate_page: This is used to compact the physical memory usage.
+- migrate_page: This is used to compact the physical memory usage.
If the VM wants to relocate a page (maybe off a memory card
that is signalling imminent failure) it will pass a new page
and an old page to this function. migrate_page should
transfer any private data across and update any references
that it has to the page.
- putback_page: Called by the VM when isolated page's migration fails.
+- putback_page: Called by the VM when isolated page's migration fails.
- launder_page: Called before freeing a page - it writes back the dirty page. To
+- launder_page: Called before freeing a page - it writes back the dirty page. To
prevent redirtying the page, it is kept locked during the whole
operation.
- is_partially_uptodate: Called by the VM when reading a file through the
+- is_partially_uptodate: Called by the VM when reading a file through the
pagecache when the underlying blocksize != pagesize. If the required
block is up to date then the read can complete without needing the IO
to bring the whole page up to date.
- is_dirty_writeback: Called by the VM when attempting to reclaim a page.
+- is_dirty_writeback: Called by the VM when attempting to reclaim a page.
The VM uses dirty and writeback information to determine if it needs
to stall to allow flushers a chance to complete some IO. Ordinarily
it can use PageDirty and PageWriteback but some filesystems have
@@ -825,17 +825,17 @@ struct address_space_operations {
allows a filesystem to indicate to the VM if a page should be
treated as dirty or writeback for the purposes of stalling.
- error_remove_page: normally set to generic_error_remove_page if truncation
+- error_remove_page: normally set to generic_error_remove_page if truncation
is ok for this address space. Used for memory failure handling.
Setting this implies you deal with pages going away under you,
unless you have them locked or reference counts increased.
- swap_activate: Called when swapon is used on a file to allocate
+- swap_activate: Called when swapon is used on a file to allocate
space if necessary and pin the block lookup information in
memory. A return value of zero indicates success,
in which case this file can be used to back swapspace.
- swap_deactivate: Called during swapoff on files where swap_activate
+- swap_deactivate: Called during swapoff on files where swap_activate
was successful.
@@ -895,35 +895,35 @@ struct file_operations {
Again, all methods are called without any locks being held, unless
otherwise noted.
- llseek: called when the VFS needs to move the file position index
+- llseek: called when the VFS needs to move the file position index
- read: called by read(2) and related system calls
+- read: called by read(2) and related system calls
- read_iter: possibly asynchronous read with iov_iter as destination
+- read_iter: possibly asynchronous read with iov_iter as destination
- write: called by write(2) and related system calls
+- write: called by write(2) and related system calls
- write_iter: possibly asynchronous write with iov_iter as source
+- write_iter: possibly asynchronous write with iov_iter as source
- iopoll: called when aio wants to poll for completions on HIPRI iocbs
+- iopoll: called when aio wants to poll for completions on HIPRI iocbs
- iterate: called when the VFS needs to read the directory contents
+- iterate: called when the VFS needs to read the directory contents
- iterate_shared: called when the VFS needs to read the directory contents
+- iterate_shared: called when the VFS needs to read the directory contents
when filesystem supports concurrent dir iterators
- poll: called by the VFS when a process wants to check if there is
+- poll: called by the VFS when a process wants to check if there is
activity on this file and (optionally) go to sleep until there
is activity. Called by the select(2) and poll(2) system calls
- unlocked_ioctl: called by the ioctl(2) system call.
+- unlocked_ioctl: called by the ioctl(2) system call.
- compat_ioctl: called by the ioctl(2) system call when 32 bit system calls
+- compat_ioctl: called by the ioctl(2) system call when 32 bit system calls
are used on 64 bit kernels.
- mmap: called by the mmap(2) system call
+- mmap: called by the mmap(2) system call
- open: called by the VFS when an inode should be opened. When the VFS
+- open: called by the VFS when an inode should be opened. When the VFS
opens a file, it creates a new "struct file". It then calls the
open method for the newly allocated file structure. You might
think that the open method really belongs in
@@ -933,40 +933,40 @@ otherwise noted.
"private_data" member in the file structure if you want to point
to a device structure
- flush: called by the close(2) system call to flush a file
+- flush: called by the close(2) system call to flush a file
- release: called when the last reference to an open file is closed
+- release: called when the last reference to an open file is closed
- fsync: called by the fsync(2) system call. Also see the section above
+- fsync: called by the fsync(2) system call. Also see the section above
entitled "Handling errors during writeback".
- fasync: called by the fcntl(2) system call when asynchronous
+- fasync: called by the fcntl(2) system call when asynchronous
(non-blocking) mode is enabled for a file
- lock: called by the fcntl(2) system call for F_GETLK, F_SETLK, and F_SETLKW
+- lock: called by the fcntl(2) system call for F_GETLK, F_SETLK, and F_SETLKW
commands
- get_unmapped_area: called by the mmap(2) system call
+- get_unmapped_area: called by the mmap(2) system call
- check_flags: called by the fcntl(2) system call for F_SETFL command
+- check_flags: called by the fcntl(2) system call for F_SETFL command
- flock: called by the flock(2) system call
+- flock: called by the flock(2) system call
- splice_write: called by the VFS to splice data from a pipe to a file. This
+- splice_write: called by the VFS to splice data from a pipe to a file. This
method is used by the splice(2) system call
- splice_read: called by the VFS to splice data from file to a pipe. This
+- splice_read: called by the VFS to splice data from file to a pipe. This
method is used by the splice(2) system call
- setlease: called by the VFS to set or release a file lock lease. setlease
+- setlease: called by the VFS to set or release a file lock lease. setlease
implementations should call generic_setlease to record or remove
the lease in the inode after setting it.
- fallocate: called by the VFS to preallocate blocks or punch a hole.
+- fallocate: called by the VFS to preallocate blocks or punch a hole.
- copy_file_range: called by the copy_file_range(2) system call.
+- copy_file_range: called by the copy_file_range(2) system call.
- remap_file_range: called by the ioctl(2) system call for FICLONERANGE and
+- remap_file_range: called by the ioctl(2) system call for FICLONERANGE and
FICLONE and FIDEDUPERANGE commands to remap file ranges. An
implementation should remap len bytes at pos_in of the source file into
the dest file at pos_out. Implementations must handle callers passing
@@ -979,7 +979,7 @@ otherwise noted.
set, the caller is ok with the implementation shortening the request
length to satisfy alignment or EOF requirements (or any other reason).
- fadvise: possibly called by the fadvise64() system call.
+- fadvise: possibly called by the fadvise64() system call.
Note that the file operations are implemented by the specific
filesystem in which the inode resides. When opening a device node
@@ -1022,7 +1022,7 @@ struct dentry_operations {
struct dentry *(*d_real)(struct dentry *, const struct inode *);
};
- d_revalidate: called when the VFS needs to revalidate a dentry. This
+- d_revalidate: called when the VFS needs to revalidate a dentry. This
is called whenever a name look-up finds a dentry in the
dcache. Most local filesystems leave this as NULL, because all their
dentries in the dcache are valid. Network filesystems are different
@@ -1041,7 +1041,7 @@ struct dentry_operations {
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
- d_weak_revalidate: called when the VFS needs to revalidate a "jumped" dentry.
+-d_weak_revalidate: called when the VFS needs to revalidate a "jumped" dentry.
This is called when a path-walk ends at dentry that was not acquired by
doing a lookup in the parent directory. This includes "/", "." and "..",
as well as procfs-style symlinks and mountpoint traversal.
@@ -1055,14 +1055,14 @@ struct dentry_operations {
d_weak_revalidate is only called after leaving rcu-walk mode.
- d_hash: called when the VFS adds a dentry to the hash table. The first
+- d_hash: called when the VFS adds a dentry to the hash table. The first
dentry passed to d_hash is the parent directory that the name is
to be hashed into.
Same locking and synchronisation rules as d_compare regarding
what is safe to dereference etc.
- d_compare: called to compare a dentry name with a given name. The first
+- d_compare: called to compare a dentry name with a given name. The first
dentry is the parent of the dentry to be compared, the second is
the child dentry. len and name string are properties of the dentry
to be compared. qstr is the name to compare it with.
@@ -1079,22 +1079,22 @@ struct dentry_operations {
It is a tricky calling convention because it needs to be called under
"rcu-walk", ie. without any locks or references on things.
- d_delete: called when the last reference to a dentry is dropped and the
+- d_delete: called when the last reference to a dentry is dropped and the
dcache is deciding whether or not to cache it. Return 1 to delete
immediately, or 0 to cache the dentry. Default is NULL which means to
always cache a reachable dentry. d_delete must be constant and
idempotent.
- d_init: called when a dentry is allocated
+- d_init: called when a dentry is allocated
- d_release: called when a dentry is really deallocated
+- d_release: called when a dentry is really deallocated
- d_iput: called when a dentry loses its inode (just prior to its
+- d_iput: called when a dentry loses its inode (just prior to its
being deallocated). The default when this is NULL is that the
VFS calls iput(). If you define this method, you must call
iput() yourself
- d_dname: called when the pathname of a dentry should be generated.
+- d_dname: called when the pathname of a dentry should be generated.
Useful for some pseudo filesystems (sockfs, pipefs, ...) to delay
pathname generation. (Instead of doing it when dentry is created,
it's done only when the path is needed.). Real filesystems probably
@@ -1114,7 +1114,7 @@ struct dentry_operations {
dentry->d_inode->i_ino);
}
- d_automount: called when an automount dentry is to be traversed (optional).
+- d_automount: called when an automount dentry is to be traversed (optional).
This should create a new VFS mount record and return the record to the
caller. The caller is supplied with a path parameter giving the
automount directory to describe the automount target and the parent
@@ -1134,7 +1134,7 @@ struct dentry_operations {
dentry. This is set by __d_instantiate() if S_AUTOMOUNT is set on the
inode being added.
- d_manage: called to allow the filesystem to manage the transition from a
+- d_manage: called to allow the filesystem to manage the transition from a
dentry (optional). This allows autofs, for example, to hold up clients
waiting to explore behind a 'mountpoint' while letting the daemon go
past and construct the subtree there. 0 should be returned to let the
@@ -1152,7 +1152,7 @@ struct dentry_operations {
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.
- d_real: overlay/union type filesystems implement this method to return one of
+- d_real: overlay/union type filesystems implement this method to return one of
the underlying dentries hidden by the overlay. It is used in two
different modes:
@@ -1174,36 +1174,36 @@ Directory Entry Cache API
There are a number of functions defined which permit a filesystem to
manipulate dentries:
- dget: open a new handle for an existing dentry (this just increments
+- dget: open a new handle for an existing dentry (this just increments
the usage count)
- dput: close a handle for a dentry (decrements the usage count). If
+- dput: close a handle for a dentry (decrements the usage count). If
the usage count drops to 0, and the dentry is still in its
parent's hash, the "d_delete" method is called to check whether
it should be cached. If it should not be cached, or if the dentry
is not hashed, it is deleted. Otherwise cached dentries are put
into an LRU list to be reclaimed on memory shortage.
- d_drop: this unhashes a dentry from its parents hash list. A
+- d_drop: this unhashes a dentry from its parents hash list. A
subsequent call to dput() will deallocate the dentry if its
usage count drops to 0
- d_delete: delete a dentry. If there are no other open references to
+- d_delete: delete a dentry. If there are no other open references to
the dentry then the dentry is turned into a negative dentry
(the d_iput() method is called). If there are other
references, then d_drop() is called instead
- d_add: add a dentry to its parents hash list and then calls
+- d_add: add a dentry to its parents hash list and then calls
d_instantiate()
- d_instantiate: add a dentry to the alias hash list for the inode and
+- d_instantiate: add a dentry to the alias hash list for the inode and
updates the "d_inode" member. The "i_count" member in the
inode structure should be set/incremented. If the inode
pointer is NULL, the dentry is called a "negative
dentry". This function is commonly called when an inode is
created for an existing negative dentry
- d_lookup: look up a dentry given its parent and path name component
+- d_lookup: look up a dentry given its parent and path name component
It looks up the child of that given name from the dcache
hash table. If it is found, the reference count is incremented
and the dentry is returned. The caller must use dput()
--
2.21.0
Kernel RST has a preferred heading adornment scheme. Currently all the
heading adornments follow this scheme except the document heading.
Use correct heading adornment for initial heading.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index ed12d28bda62..790feccca5f4 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -1,5 +1,6 @@
-
- Overview of the Linux Virtual File System
+=========================================
+Overview of the Linux Virtual File System
+=========================================
Original author: Richard Gooch <[email protected]>
--
2.21.0
Currently spacing before and after headings is non-uniform. Use two
blank lines before a heading and one after the heading.
Use uniform spacing around headings.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 14839bc84d38..ed12d28bda62 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -321,6 +321,7 @@ Whoever sets up the inode is responsible for filling in the "i_op"
field. This is a pointer to a "struct inode_operations" which describes
the methods that can be performed on individual inodes.
+
struct xattr_handlers
---------------------
@@ -507,6 +508,7 @@ otherwise noted.
tmpfile: called in the end of O_TMPFILE open(). Optional, equivalent to
atomically creating, opening and unlinking a file in given directory.
+
The Address Space Object
========================
@@ -580,8 +582,10 @@ and the constraints under which it is being done. It is also used to
return information back to the caller about the result of a writepage or
writepages request.
+
Handling errors during writeback
--------------------------------
+
Most applications that do buffered I/O will periodically call a file
synchronization call (fsync, fdatasync, msync or sync_file_range) to
ensure that data written has made it to the backing store. When there
@@ -612,6 +616,7 @@ file->fsync operation, they should call file_check_and_advance_wb_err to
ensure that the struct file's error cursor has advanced to the correct
point in the stream of errors emitted by the backing device(s).
+
struct address_space_operations
-------------------------------
@@ -1203,9 +1208,11 @@ manipulate dentries:
and the dentry is returned. The caller must use dput()
to free the dentry when it finishes using it.
+
Mount Options
=============
+
Parsing options
---------------
@@ -1220,6 +1227,7 @@ The <linux/parser.h> header defines an API that helps parse these
options. There are plenty of examples on how to use it in existing
filesystems.
+
Showing options
---------------
@@ -1241,6 +1249,7 @@ The underlying reason for the above rules is to make sure, that a mount
can be accurately replicated (e.g. umounting and mounting again) based
on the information found in /proc/mounts.
+
Resources
=========
--
2.21.0
Currently sometimes document has a single space after a period and
sometimes it has double. Whichever we use it should be uniform.
Use double space after period, be uniform.
Tested-by: Randy Dunlap <[email protected]>
Signed-off-by: Tobin C. Harding <[email protected]>
---
Documentation/filesystems/vfs.txt | 246 +++++++++++++++---------------
1 file changed, 123 insertions(+), 123 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 637fd1756b89..2a610b9355e0 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -16,12 +16,12 @@ Introduction
The Virtual File System (also known as the Virtual Filesystem Switch)
is the software layer in the kernel that provides the filesystem
-interface to userspace programs. It also provides an abstraction
+interface to userspace programs. It also provides an abstraction
within the kernel which allows different filesystem implementations to
coexist.
VFS system calls open(2), stat(2), read(2), write(2), chmod(2) and so
-on are called from a process context. Filesystem locking is described
+on are called from a process context. Filesystem locking is described
in the document Documentation/filesystems/Locking.
@@ -29,37 +29,37 @@ Directory Entry Cache (dcache)
------------------------------
The VFS implements the open(2), stat(2), chmod(2), and similar system
-calls. The pathname argument that is passed to them is used by the VFS
+calls. The pathname argument that is passed to them is used by the VFS
to search through the directory entry cache (also known as the dentry
-cache or dcache). This provides a very fast look-up mechanism to
-translate a pathname (filename) into a specific dentry. Dentries live
+cache or dcache). This provides a very fast look-up mechanism to
+translate a pathname (filename) into a specific dentry. Dentries live
in RAM and are never saved to disc: they exist only for performance.
-The dentry cache is meant to be a view into your entire filespace. As
+The dentry cache is meant to be a view into your entire filespace. As
most computers cannot fit all dentries in the RAM at the same time,
-some bits of the cache are missing. In order to resolve your pathname
+some bits of the cache are missing. In order to resolve your pathname
into a dentry, the VFS may have to resort to creating dentries along
-the way, and then loading the inode. This is done by looking up the
+the way, and then loading the inode. This is done by looking up the
inode.
The Inode Object
----------------
-An individual dentry usually has a pointer to an inode. Inodes are
+An individual dentry usually has a pointer to an inode. Inodes are
filesystem objects such as regular files, directories, FIFOs and other
beasts. They live either on the disc (for block device filesystems)
-or in the memory (for pseudo filesystems). Inodes that live on the
+or in the memory (for pseudo filesystems). Inodes that live on the
disc are copied into the memory when required and changes to the inode
-are written back to disc. A single inode can be pointed to by multiple
+are written back to disc. A single inode can be pointed to by multiple
dentries (hard links, for example, do this).
To look up an inode requires that the VFS calls the lookup() method of
-the parent directory inode. This method is installed by the specific
-filesystem implementation that the inode lives in. Once the VFS has
+the parent directory inode. This method is installed by the specific
+filesystem implementation that the inode lives in. Once the VFS has
the required dentry (and hence the inode), we can do all those boring
things like open(2) the file, or stat(2) it to peek at the inode
-data. The stat(2) operation is fairly simple: once the VFS has the
+data. The stat(2) operation is fairly simple: once the VFS has the
dentry, it peeks at the inode data and passes some of it back to
userspace.
@@ -69,17 +69,17 @@ The File Object
Opening a file requires another operation: allocation of a file
structure (this is the kernel-side implementation of file
-descriptors). The freshly allocated file structure is initialized with
+descriptors). The freshly allocated file structure is initialized with
a pointer to the dentry and a set of file operation member functions.
-These are taken from the inode data. The open() file method is then
-called so the specific filesystem implementation can do its work. You
-can see that this is another switch performed by the VFS. The file
+These are taken from the inode data. The open() file method is then
+called so the specific filesystem implementation can do its work. You
+can see that this is another switch performed by the VFS. The file
structure is placed into the file descriptor table for the process.
Reading, writing and closing files (and other assorted VFS operations)
is done by using the userspace file descriptor to grab the appropriate
file structure, and then calling the required file structure method to
-do whatever is required. For as long as the file is open, it keeps the
+do whatever is required. For as long as the file is open, it keeps the
dentry in use, which in turn means that the VFS inode is still in use.
@@ -94,7 +94,7 @@ functions:
extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
-The passed struct file_system_type describes your filesystem. When a
+The passed struct file_system_type describes your filesystem. When a
request is made to mount a filesystem onto a directory in your namespace,
the VFS will call the appropriate mount() method for the specific
filesystem. New vfsmount referring to the tree returned by ->mount()
@@ -108,7 +108,7 @@ file /proc/filesystems.
struct file_system_type
-----------------------
-This describes the filesystem. As of kernel 2.6.39, the following
+This describes the filesystem. As of kernel 2.6.39, the following
members are defined:
struct file_system_type {
@@ -170,12 +170,12 @@ point of view is a reference to dentry at the root of (sub)tree to
be attached; creation of new superblock is a common side effect.
The most interesting member of the superblock structure that the
-mount() method fills in is the "s_op" field. This is a pointer to
+mount() method fills in is the "s_op" field. This is a pointer to
a "struct super_operations" which describes the next level of the
filesystem implementation.
Usually, a filesystem uses one of the generic mount() implementations
-and provides a fill_super() callback instead. The generic variants are:
+and provides a fill_super() callback instead. The generic variants are:
mount_bdev: mount a filesystem residing on a block device
@@ -186,7 +186,7 @@ and provides a fill_super() callback instead. The generic variants are:
A fill_super() callback implementation has the following arguments:
- struct super_block *sb: the superblock structure. The callback
+ struct super_block *sb: the superblock structure. The callback
must initialize this properly.
void *data: arbitrary mount options, usually comes as an ASCII
@@ -205,7 +205,7 @@ struct super_operations
-----------------------
This describes how the VFS can manipulate the superblock of your
-filesystem. As of kernel 2.6.22, the following members are defined:
+filesystem. As of kernel 2.6.22, the following members are defined:
struct super_operations {
struct inode *(*alloc_inode)(struct super_block *sb);
@@ -233,7 +233,7 @@ struct super_operations {
};
All methods are called without any locks being held, unless otherwise
-noted. This means that most methods can block safely. All methods are
+noted. This means that most methods can block safely. All methods are
only called from a process context (i.e. not from an interrupt handler
or bottom half).
@@ -270,11 +270,11 @@ or bottom half).
delete_inode: called when the VFS wants to delete an inode
put_super: called when the VFS wishes to free the superblock
- (i.e. unmount). This is called with the superblock lock held
+ (i.e. unmount). This is called with the superblock lock held
sync_fs: called when VFS is writing out all dirty data associated with
- a superblock. The second parameter indicates whether the method
- should wait until the write out has been completed. Optional.
+ a superblock. The second parameter indicates whether the method
+ should wait until the write out has been completed. Optional.
freeze_fs: called when VFS is locking a filesystem and
forcing it into a consistent state. This method is currently
@@ -285,10 +285,10 @@ or bottom half).
statfs: called when the VFS needs to get filesystem statistics.
- remount_fs: called when the filesystem is remounted. This is called
+ remount_fs: called when the filesystem is remounted. This is called
with the kernel lock held
- clear_inode: called then the VFS clears the inode. Optional
+ clear_inode: called then the VFS clears the inode. Optional
umount_begin: called when the VFS is unmounting a filesystem.
@@ -309,17 +309,17 @@ or bottom half).
implement ->nr_cached_objects for it to be called correctly.
We can't do anything with any errors that the filesystem might
- encountered, hence the void return type. This will never be called if
+ encountered, hence the void return type. This will never be called if
the VM is trying to reclaim under GFP_NOFS conditions, hence this
method does not need to handle that situation itself.
Implementations must include conditional reschedule calls inside any
- scanning loop that is done. This allows the VFS to determine
+ scanning loop that is done. This allows the VFS to determine
appropriate scan batch sizes without having to worry about whether
implementations will cause holdoff problems due to large scan batch
sizes.
-Whoever sets up the inode is responsible for filling in the "i_op" field. This
+Whoever sets up the inode is responsible for filling in the "i_op" field. This
is a pointer to a "struct inode_operations" which describes the methods that
can be performed on individual inodes.
@@ -363,7 +363,7 @@ struct inode_operations
-----------------------
This describes how the VFS can manipulate an inode in your
-filesystem. As of kernel 2.6.22, the following members are defined:
+filesystem. As of kernel 2.6.22, the following members are defined:
struct inode_operations {
int (*create) (struct inode *,struct dentry *, umode_t, bool);
@@ -393,19 +393,19 @@ struct inode_operations {
Again, all methods are called without any locks being held, unless
otherwise noted.
- create: called by the open(2) and creat(2) system calls. Only
- required if you want to support regular files. The dentry you
+ create: called by the open(2) and creat(2) system calls. Only
+ required if you want to support regular files. The dentry you
get should not have an inode (i.e. it should be a negative
- dentry). Here you will probably call d_instantiate() with the
+ dentry). Here you will probably call d_instantiate() with the
dentry and the newly created inode
lookup: called when the VFS needs to look up an inode in a parent
- directory. The name to look for is found in the dentry. This
+ directory. The name to look for is found in the dentry. This
method must call d_add() to insert the found inode into the
- dentry. The "i_count" field in the inode structure should be
- incremented. If the named inode does not exist a NULL inode
+ dentry. The "i_count" field in the inode structure should be
+ incremented. If the named inode does not exist a NULL inode
should be inserted into the dentry (this is called a negative
- dentry). Returning an error code from this routine must only
+ dentry). Returning an error code from this routine must only
be done on a real error, otherwise creating inodes with system
calls like create(2), mknod(2), mkdir(2) and so on will fail.
If you wish to overload the dentry methods then you should
@@ -413,27 +413,27 @@ otherwise noted.
to a struct "dentry_operations".
This method is called with the directory inode semaphore held
- link: called by the link(2) system call. Only required if you want
- to support hard links. You will probably need to call
+ link: called by the link(2) system call. Only required if you want
+ to support hard links. You will probably need to call
d_instantiate() just as you would in the create() method
- unlink: called by the unlink(2) system call. Only required if you
+ unlink: called by the unlink(2) system call. Only required if you
want to support deleting inodes
- symlink: called by the symlink(2) system call. Only required if you
- want to support symlinks. You will probably need to call
+ symlink: called by the symlink(2) system call. Only required if you
+ want to support symlinks. You will probably need to call
d_instantiate() just as you would in the create() method
- mkdir: called by the mkdir(2) system call. Only required if you want
- to support creating subdirectories. You will probably need to
+ mkdir: called by the mkdir(2) system call. Only required if you want
+ to support creating subdirectories. You will probably need to
call d_instantiate() just as you would in the create() method
- rmdir: called by the rmdir(2) system call. Only required if you want
+ rmdir: called by the rmdir(2) system call. Only required if you want
to support deleting subdirectories
mknod: called by the mknod(2) system call to create a device (char,
- block) inode or a named pipe (FIFO) or socket. Only required
- if you want to support creating these types of inodes. You
+ block) inode or a named pipe (FIFO) or socket. Only required
+ if you want to support creating these types of inodes. You
will probably need to call d_instantiate() just as you would
in the create() method
@@ -474,21 +474,21 @@ otherwise noted.
permission: called by the VFS to check for access rights on a POSIX-like
filesystem.
- May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
- mode, the filesystem must check the permission without blocking or
+ May be called in rcu-walk mode (mask & MAY_NOT_BLOCK). If in rcu-walk
+ mode, the filesystem must check the permission without blocking or
storing to the inode.
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
- setattr: called by the VFS to set attributes for a file. This method
+ setattr: called by the VFS to set attributes for a file. This method
is called by chmod(2) and related system calls.
- getattr: called by the VFS to get attributes of a file. This method
+ getattr: called by the VFS to get attributes of a file. This method
is called by stat(2) and related system calls.
listxattr: called by the VFS to list all extended attributes for a
- given file. This method is called by the listxattr(2) system call.
+ given file. This method is called by the listxattr(2) system call.
update_time: called by the VFS to update a specific time or the i_version of
an inode. If this is not defined the VFS will update the inode itself
@@ -526,7 +526,7 @@ The first can be used independently to the others. The VM can try to
either write dirty pages in order to clean them, or release clean
pages in order to reuse them. To do this it can call the ->writepage
method on dirty pages, and ->releasepage on clean pages with
-PagePrivate set. Clean pages without PagePrivate and with no external
+PagePrivate set. Clean pages without PagePrivate and with no external
references will be released without notice being given to the
address_space.
@@ -534,7 +534,7 @@ To achieve this functionality, pages need to be placed on an LRU with
lru_cache_add and mark_page_active needs to be called whenever the
page is used.
-Pages are normally kept in a radix tree index by ->index. This tree
+Pages are normally kept in a radix tree index by ->index. This tree
maintains information about the PG_Dirty and PG_Writeback status of
each page, so that pages with either of these flags can be found
quickly.
@@ -620,7 +620,7 @@ struct address_space_operations
-------------------------------
This describes how the VFS can manipulate mapping of a file to page cache in
-your filesystem. The following members are defined:
+your filesystem. The following members are defined:
struct address_space_operations {
int (*writepage)(struct page *page, struct writeback_control *wbc);
@@ -700,7 +700,7 @@ struct address_space_operations {
PAGECACHE_TAG_DIRTY tag in the radix tree.
readpages: called by the VM to read pages associated with the address_space
- object. This is essentially just a vector version of
+ object. This is essentially just a vector version of
readpage. Instead of just one page, several pages are
requested.
readpages is only used for read-ahead, so read errors are
@@ -708,7 +708,7 @@ struct address_space_operations {
write_begin:
Called by the generic buffered write code to ask the filesystem to
- prepare to write len bytes at the given offset in the file. The
+ prepare to write len bytes at the given offset in the file. The
address_space should check that the write will be able to complete,
by allocating space if necessary and doing any other internal
housekeeping. If the write will update parts of any basic-blocks on
@@ -731,7 +731,7 @@ struct address_space_operations {
which case write_end is not called.
write_end: After a successful write_begin, and data copy, write_end must
- be called. len is the original len passed to write_begin, and copied
+ be called. len is the original len passed to write_begin, and copied
is the amount that was able to be copied.
The filesystem must take care of unlocking the page and releasing it
@@ -741,7 +741,7 @@ struct address_space_operations {
that were able to be copied into pagecache.
bmap: called by the VFS to map a logical block offset within object to
- physical block number. This method is used by the FIBMAP
+ physical block number. This method is used by the FIBMAP
ioctl and for working with swap-files. To be able to swap to
a file, the file must have a stable mapping to a block
device. The swap system does not go through the filesystem
@@ -753,7 +753,7 @@ struct address_space_operations {
from the address space. This generally corresponds to either a
truncation, punch hole or a complete invalidation of the address
space (in the latter case 'offset' will always be 0 and 'length'
- will be PAGE_SIZE). Any private data associated with the page
+ will be PAGE_SIZE). Any private data associated with the page
should be updated to reflect this truncation. If offset is 0 and
length is PAGE_SIZE, then the private data should be released,
because the page must be able to be completely discarded. This may
@@ -763,7 +763,7 @@ struct address_space_operations {
releasepage: releasepage is called on PagePrivate pages to indicate
that the page should be freed if possible. ->releasepage
should remove any private data from the page and clear the
- PagePrivate flag. If releasepage() fails for some reason, it must
+ PagePrivate flag. If releasepage() fails for some reason, it must
indicate failure with a 0 return value.
releasepage() is used in two distinct though related cases. The
first is when the VM finds a clean page with no active users and
@@ -783,7 +783,7 @@ struct address_space_operations {
freepage: freepage is called once the page is no longer visible in
the page cache in order to allow the cleanup of any private
- data. Since it may be called by the memory reclaimer, it
+ data. Since it may be called by the memory reclaimer, it
should not assume that the original address_space mapping still
exists, and it should not block.
@@ -805,32 +805,32 @@ struct address_space_operations {
putback_page: Called by the VM when isolated page's migration fails.
- launder_page: Called before freeing a page - it writes back the dirty page. To
+ launder_page: Called before freeing a page - it writes back the dirty page. To
prevent redirtying the page, it is kept locked during the whole
operation.
is_partially_uptodate: Called by the VM when reading a file through the
- pagecache when the underlying blocksize != pagesize. If the required
+ pagecache when the underlying blocksize != pagesize. If the required
block is up to date then the read can complete without needing the IO
to bring the whole page up to date.
is_dirty_writeback: Called by the VM when attempting to reclaim a page.
The VM uses dirty and writeback information to determine if it needs
- to stall to allow flushers a chance to complete some IO. Ordinarily
+ to stall to allow flushers a chance to complete some IO. Ordinarily
it can use PageDirty and PageWriteback but some filesystems have
more complex state (unstable pages in NFS prevent reclaim) or
- do not set those flags due to locking problems. This callback
+ do not set those flags due to locking problems. This callback
allows a filesystem to indicate to the VM if a page should be
treated as dirty or writeback for the purposes of stalling.
error_remove_page: normally set to generic_error_remove_page if truncation
- is ok for this address space. Used for memory failure handling.
+ is ok for this address space. Used for memory failure handling.
Setting this implies you deal with pages going away under you,
unless you have them locked or reference counts increased.
swap_activate: Called when swapon is used on a file to allocate
space if necessary and pin the block lookup information in
- memory. A return value of zero indicates success,
+ memory. A return value of zero indicates success,
in which case this file can be used to back swapspace.
swap_deactivate: Called during swapoff on files where swap_activate
@@ -840,14 +840,14 @@ struct address_space_operations {
The File Object
===============
-A file object represents a file opened by a process. This is also known
+A file object represents a file opened by a process. This is also known
as an "open file description" in POSIX parlance.
struct file_operations
----------------------
-This describes how the VFS can manipulate an open file. As of kernel
+This describes how the VFS can manipulate an open file. As of kernel
4.18, the following members are defined:
struct file_operations {
@@ -912,7 +912,7 @@ otherwise noted.
poll: called by the VFS when a process wants to check if there is
activity on this file and (optionally) go to sleep until there
- is activity. Called by the select(2) and poll(2) system calls
+ is activity. Called by the select(2) and poll(2) system calls
unlocked_ioctl: called by the ioctl(2) system call.
@@ -921,13 +921,13 @@ otherwise noted.
mmap: called by the mmap(2) system call
- open: called by the VFS when an inode should be opened. When the VFS
- opens a file, it creates a new "struct file". It then calls the
- open method for the newly allocated file structure. You might
+ open: called by the VFS when an inode should be opened. When the VFS
+ opens a file, it creates a new "struct file". It then calls the
+ open method for the newly allocated file structure. You might
think that the open method really belongs in
- "struct inode_operations", and you may be right. I think it's
+ "struct inode_operations", and you may be right. I think it's
done the way it is because it makes filesystems simpler to
- implement. The open() method is a good place to initialize the
+ implement. The open() method is a good place to initialize the
"private_data" member in the file structure if you want to point
to a device structure
@@ -935,7 +935,7 @@ otherwise noted.
release: called when the last reference to an open file is closed
- fsync: called by the fsync(2) system call. Also see the section above
+ fsync: called by the fsync(2) system call. Also see the section above
entitled "Handling errors during writeback".
fasync: called by the fcntl(2) system call when asynchronous
@@ -950,13 +950,13 @@ otherwise noted.
flock: called by the flock(2) system call
- splice_write: called by the VFS to splice data from a pipe to a file. This
+ splice_write: called by the VFS to splice data from a pipe to a file. This
method is used by the splice(2) system call
- splice_read: called by the VFS to splice data from file to a pipe. This
+ splice_read: called by the VFS to splice data from file to a pipe. This
method is used by the splice(2) system call
- setlease: called by the VFS to set or release a file lock lease. setlease
+ setlease: called by the VFS to set or release a file lock lease. setlease
implementations should call generic_setlease to record or remove
the lease in the inode after setting it.
@@ -980,12 +980,12 @@ otherwise noted.
fadvise: possibly called by the fadvise64() system call.
Note that the file operations are implemented by the specific
-filesystem in which the inode resides. When opening a device node
+filesystem in which the inode resides. When opening a device node
(character or block special) most filesystems will call special
support routines in the VFS which will locate the required device
-driver information. These support routines replace the filesystem file
+driver information. These support routines replace the filesystem file
operations with those for the device driver, and then proceed to call
-the new open() method for the file. This is how opening a device file
+the new open() method for the file. This is how opening a device file
in the filesystem eventually ends up calling the device driver open()
method.
@@ -998,10 +998,10 @@ struct dentry_operations
------------------------
This describes how a filesystem can overload the standard dentry
-operations. Dentries and the dcache are the domain of the VFS and the
-individual filesystem implementations. Device drivers have no business
-here. These methods may be set to NULL, as they are either optional or
-the VFS uses a default. As of kernel 2.6.22, the following members are
+operations. Dentries and the dcache are the domain of the VFS and the
+individual filesystem implementations. Device drivers have no business
+here. These methods may be set to NULL, as they are either optional or
+the VFS uses a default. As of kernel 2.6.22, the following members are
defined:
struct dentry_operations {
@@ -1020,10 +1020,10 @@ struct dentry_operations {
struct dentry *(*d_real)(struct dentry *, const struct inode *);
};
- d_revalidate: called when the VFS needs to revalidate a dentry. This
+ d_revalidate: called when the VFS needs to revalidate a dentry. This
is called whenever a name look-up finds a dentry in the
- dcache. Most local filesystems leave this as NULL, because all their
- dentries in the dcache are valid. Network filesystems are different
+ dcache. Most local filesystems leave this as NULL, because all their
+ dentries in the dcache are valid. Network filesystems are different
since things can change on the server without the client necessarily
being aware of it.
@@ -1041,11 +1041,11 @@ struct dentry_operations {
d_weak_revalidate: called when the VFS needs to revalidate a "jumped" dentry.
This is called when a path-walk ends at dentry that was not acquired by
- doing a lookup in the parent directory. This includes "/", "." and "..",
+ doing a lookup in the parent directory. This includes "/", "." and "..",
as well as procfs-style symlinks and mountpoint traversal.
In this case, we are less concerned with whether the dentry is still
- fully correct, but rather that the inode is still valid. As with
+ fully correct, but rather that the inode is still valid. As with
d_revalidate, most local filesystems will set this to NULL since their
dcache entries are always valid.
@@ -1053,17 +1053,17 @@ struct dentry_operations {
d_weak_revalidate is only called after leaving rcu-walk mode.
- d_hash: called when the VFS adds a dentry to the hash table. The first
+ d_hash: called when the VFS adds a dentry to the hash table. The first
dentry passed to d_hash is the parent directory that the name is
to be hashed into.
Same locking and synchronisation rules as d_compare regarding
what is safe to dereference etc.
- d_compare: called to compare a dentry name with a given name. The first
+ d_compare: called to compare a dentry name with a given name. The first
dentry is the parent of the dentry to be compared, the second is
- the child dentry. len and name string are properties of the dentry
- to be compared. qstr is the name to compare it with.
+ the child dentry. len and name string are properties of the dentry
+ to be compared. qstr is the name to compare it with.
Must be constant and idempotent, and should not take locks if
possible, and should not or store into the dentry.
@@ -1078,9 +1078,9 @@ struct dentry_operations {
"rcu-walk", ie. without any locks or references on things.
d_delete: called when the last reference to a dentry is dropped and the
- dcache is deciding whether or not to cache it. Return 1 to delete
- immediately, or 0 to cache the dentry. Default is NULL which means to
- always cache a reachable dentry. d_delete must be constant and
+ dcache is deciding whether or not to cache it. Return 1 to delete
+ immediately, or 0 to cache the dentry. Default is NULL which means to
+ always cache a reachable dentry. d_delete must be constant and
idempotent.
d_init: called when a dentry is allocated
@@ -1088,19 +1088,19 @@ struct dentry_operations {
d_release: called when a dentry is really deallocated
d_iput: called when a dentry loses its inode (just prior to its
- being deallocated). The default when this is NULL is that the
- VFS calls iput(). If you define this method, you must call
+ being deallocated). The default when this is NULL is that the
+ VFS calls iput(). If you define this method, you must call
iput() yourself
d_dname: called when the pathname of a dentry should be generated.
Useful for some pseudo filesystems (sockfs, pipefs, ...) to delay
- pathname generation. (Instead of doing it when dentry is created,
- it's done only when the path is needed.). Real filesystems probably
+ pathname generation. (Instead of doing it when dentry is created,
+ it's done only when the path is needed.). Real filesystems probably
dont want to use it, because their dentries are present in global
- dcache hash, so their hash should be an invariant. As no lock is
+ dcache hash, so their hash should be an invariant. As no lock is
held, d_dname() should not try to modify the dentry itself, unless
- appropriate SMP safety is used. CAUTION : d_path() logic is quite
- tricky. The correct way to return for example "Hello" is to put it
+ appropriate SMP safety is used. CAUTION : d_path() logic is quite
+ tricky. The correct way to return for example "Hello" is to put it
at the end of the buffer, and returns a pointer to the first char.
dynamic_dname() helper function is provided to take care of this.
@@ -1162,7 +1162,7 @@ struct dentry_operations {
With NULL inode the topmost real underlying dentry is returned.
Each dentry has a pointer to its parent dentry, as well as a hash list
-of child dentries. Child dentries are basically like files in a
+of child dentries. Child dentries are basically like files in a
directory.
@@ -1175,36 +1175,36 @@ manipulate dentries:
dget: open a new handle for an existing dentry (this just increments
the usage count)
- dput: close a handle for a dentry (decrements the usage count). If
+ dput: close a handle for a dentry (decrements the usage count). If
the usage count drops to 0, and the dentry is still in its
parent's hash, the "d_delete" method is called to check whether
- it should be cached. If it should not be cached, or if the dentry
- is not hashed, it is deleted. Otherwise cached dentries are put
+ it should be cached. If it should not be cached, or if the dentry
+ is not hashed, it is deleted. Otherwise cached dentries are put
into an LRU list to be reclaimed on memory shortage.
- d_drop: this unhashes a dentry from its parents hash list. A
+ d_drop: this unhashes a dentry from its parents hash list. A
subsequent call to dput() will deallocate the dentry if its
usage count drops to 0
- d_delete: delete a dentry. If there are no other open references to
+ d_delete: delete a dentry. If there are no other open references to
the dentry then the dentry is turned into a negative dentry
- (the d_iput() method is called). If there are other
+ (the d_iput() method is called). If there are other
references, then d_drop() is called instead
d_add: add a dentry to its parents hash list and then calls
d_instantiate()
d_instantiate: add a dentry to the alias hash list for the inode and
- updates the "d_inode" member. The "i_count" member in the
- inode structure should be set/incremented. If the inode
+ updates the "d_inode" member. The "i_count" member in the
+ inode structure should be set/incremented. If the inode
pointer is NULL, the dentry is called a "negative
- dentry". This function is commonly called when an inode is
+ dentry". This function is commonly called when an inode is
created for an existing negative dentry
d_lookup: look up a dentry given its parent and path name component
It looks up the child of that given name from the dcache
- hash table. If it is found, the reference count is incremented
- and the dentry is returned. The caller must use dput()
+ hash table. If it is found, the reference count is incremented
+ and the dentry is returned. The caller must use dput()
to free the dentry when it finishes using it.
Mount Options
--
2.21.0
On Tue, Mar 19, 2019 at 10:14:33AM +1100, Tobin C. Harding wrote:
> Use code-block for C source code. With this in place we can rename the
> .txt file to .rst. This introduces a few warnings that will be fixed
> in proceeding patches.
>
> Add '.. code-block:: c' to C source code snippets. Rename the file to
> use rst file suffix.
I just realised that a better way to document these structs is to do so
above the actual struct definition in the source file then include those
docs in the documentation file.
I'm working on that now, I can do it on top of this or we can drop this
and I can do it all as a v3.
No further comments below, leaving for reference.
thanks,
Tobin.
> Tested-by: Randy Dunlap <[email protected]>
> Signed-off-by: Tobin C. Harding <[email protected]>
> ---
>
> This ones a punish to review. It fixes up spacing around the struct
> definitions. In hindsight this may not be what we want because now the
> docs do not _exactly_ mirror the code. If this goes through update to
> vfs.rst aims to patch the code first then update vfs.rst :)
>
> Documentation/filesystems/index.rst | 1 +
> .../filesystems/{vfs.txt => vfs.rst} | 321 +++++++++---------
> 2 files changed, 169 insertions(+), 153 deletions(-)
> rename Documentation/filesystems/{vfs.txt => vfs.rst} (86%)
>
> diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
> index 1131c34d77f6..35644840a690 100644
> --- a/Documentation/filesystems/index.rst
> +++ b/Documentation/filesystems/index.rst
> @@ -16,6 +16,7 @@ algorithms work.
> .. toctree::
> :maxdepth: 2
>
> + vfs
> path-lookup.rst
> api-summary
> splice
> diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.rst
> similarity index 86%
> rename from Documentation/filesystems/vfs.txt
> rename to Documentation/filesystems/vfs.rst
> index 6e709815a6dd..dc2dd81f5e83 100644
> --- a/Documentation/filesystems/vfs.txt
> +++ b/Documentation/filesystems/vfs.rst
> @@ -87,6 +87,8 @@ Registering and Mounting a Filesystem
> To register and unregister a filesystem, use the following API
> functions:
>
> +.. code-block:: c
> +
> #include <linux/fs.h>
>
> extern int register_filesystem(struct file_system_type *);
> @@ -110,18 +112,19 @@ struct file_system_type
> This describes the filesystem. As of kernel 2.6.39, the following
> members are defined:
>
> -struct file_system_type {
> - const char *name;
> - int fs_flags;
> - struct dentry *(*mount) (struct file_system_type *, int,
> - const char *, void *);
> - void (*kill_sb) (struct super_block *);
> - struct module *owner;
> - struct file_system_type * next;
> - struct list_head fs_supers;
> - struct lock_class_key s_lock_key;
> - struct lock_class_key s_umount_key;
> -};
> +.. code-block:: c
> +
> + struct file_system_type {
> + const char *name;
> + int fs_flags;
> + struct dentry *(*mount) (struct file_system_type *, int, const char *, void *);
> + void (*kill_sb) (struct super_block *);
> + struct module *owner;
> + struct file_system_type * next;
> + struct list_head fs_supers;
> + struct lock_class_key s_lock_key;
> + struct lock_class_key s_umount_key;
> + };
>
> - name: the name of the filesystem type, such as "ext2", "iso9660",
> "msdos" and so on
> @@ -206,30 +209,31 @@ struct super_operations
> This describes how the VFS can manipulate the superblock of your
> filesystem. As of kernel 2.6.22, the following members are defined:
>
> -struct super_operations {
> - struct inode *(*alloc_inode)(struct super_block *sb);
> - void (*destroy_inode)(struct inode *);
> -
> - void (*dirty_inode) (struct inode *, int flags);
> - int (*write_inode) (struct inode *, int);
> - void (*drop_inode) (struct inode *);
> - void (*delete_inode) (struct inode *);
> - void (*put_super) (struct super_block *);
> - int (*sync_fs)(struct super_block *sb, int wait);
> - int (*freeze_fs) (struct super_block *);
> - int (*unfreeze_fs) (struct super_block *);
> - int (*statfs) (struct dentry *, struct kstatfs *);
> - int (*remount_fs) (struct super_block *, int *, char *);
> - void (*clear_inode) (struct inode *);
> - void (*umount_begin) (struct super_block *);
> -
> - int (*show_options)(struct seq_file *, struct dentry *);
> -
> - ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
> - ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
> - int (*nr_cached_objects)(struct super_block *);
> - void (*free_cached_objects)(struct super_block *, int);
> -};
> +.. code-block:: c
> +
> + struct super_operations {
> + struct inode *(*alloc_inode)(struct super_block *sb);
> + void (*destroy_inode)(struct inode *);
> + void (*dirty_inode) (struct inode *, int flags);
> + int (*write_inode) (struct inode *, int);
> + void (*drop_inode) (struct inode *);
> + void (*delete_inode) (struct inode *);
> + void (*put_super) (struct super_block *);
> + int (*sync_fs)(struct super_block *sb, int wait);
> + int (*freeze_fs) (struct super_block *);
> + int (*unfreeze_fs) (struct super_block *);
> + int (*statfs) (struct dentry *, struct kstatfs *);
> + int (*remount_fs) (struct super_block *, int *, char *);
> + void (*clear_inode) (struct inode *);
> + void (*umount_begin) (struct super_block *);
> +
> + int (*show_options)(struct seq_file *, struct dentry *);
> +
> + ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
> + ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
> + int (*nr_cached_objects)(struct super_block *);
> + void (*free_cached_objects)(struct super_block *, int);
> + };
>
> All methods are called without any locks being held, unless otherwise
> noted. This means that most methods can block safely. All methods are
> @@ -365,30 +369,32 @@ struct inode_operations
> This describes how the VFS can manipulate an inode in your filesystem.
> As of kernel 2.6.22, the following members are defined:
>
> -struct inode_operations {
> - int (*create) (struct inode *,struct dentry *, umode_t, bool);
> - struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
> - int (*link) (struct dentry *,struct inode *,struct dentry *);
> - int (*unlink) (struct inode *,struct dentry *);
> - int (*symlink) (struct inode *,struct dentry *,const char *);
> - int (*mkdir) (struct inode *,struct dentry *,umode_t);
> - int (*rmdir) (struct inode *,struct dentry *);
> - int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
> - int (*rename) (struct inode *, struct dentry *,
> - struct inode *, struct dentry *, unsigned int);
> - int (*readlink) (struct dentry *, char __user *,int);
> - const char *(*get_link) (struct dentry *, struct inode *,
> - struct delayed_call *);
> - int (*permission) (struct inode *, int);
> - int (*get_acl)(struct inode *, int);
> - int (*setattr) (struct dentry *, struct iattr *);
> - int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
> - ssize_t (*listxattr) (struct dentry *, char *, size_t);
> - void (*update_time)(struct inode *, struct timespec *, int);
> - int (*atomic_open)(struct inode *, struct dentry *, struct file *,
> - unsigned open_flag, umode_t create_mode);
> - int (*tmpfile) (struct inode *, struct dentry *, umode_t);
> -};
> +.. code-block:: c
> +
> + struct inode_operations {
> + int (*create) (struct inode *,struct dentry *, umode_t, bool);
> + struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
> + int (*link) (struct dentry *,struct inode *,struct dentry *);
> + int (*unlink) (struct inode *,struct dentry *);
> + int (*symlink) (struct inode *,struct dentry *,const char *);
> + int (*mkdir) (struct inode *,struct dentry *,umode_t);
> + int (*rmdir) (struct inode *,struct dentry *);
> + int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
> + int (*rename) (struct inode *, struct dentry *,
> + struct inode *, struct dentry *, unsigned int);
> + int (*readlink) (struct dentry *, char __user *,int);
> + const char *(*get_link) (struct dentry *, struct inode *,
> + struct delayed_call *);
> + int (*permission) (struct inode *, int);
> + int (*get_acl)(struct inode *, int);
> + int (*setattr) (struct dentry *, struct iattr *);
> + int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
> + ssize_t (*listxattr) (struct dentry *, char *, size_t);
> + void (*update_time)(struct inode *, struct timespec *, int);
> + int (*atomic_open)(struct inode *, struct dentry *, struct file *,
> + unsigned open_flag, umode_t create_mode);
> + int (*tmpfile) (struct inode *, struct dentry *, umode_t);
> + };
>
> Again, all methods are called without any locks being held, unless
> otherwise noted.
> @@ -624,39 +630,41 @@ struct address_space_operations
> This describes how the VFS can manipulate mapping of a file to page
> cache in your filesystem. The following members are defined:
>
> -struct address_space_operations {
> - int (*writepage)(struct page *page, struct writeback_control *wbc);
> - int (*readpage)(struct file *, struct page *);
> - int (*writepages)(struct address_space *, struct writeback_control *);
> - int (*set_page_dirty)(struct page *page);
> - int (*readpages)(struct file *filp, struct address_space *mapping,
> - struct list_head *pages, unsigned nr_pages);
> - int (*write_begin)(struct file *, struct address_space *mapping,
> - loff_t pos, unsigned len, unsigned flags,
> - struct page **pagep, void **fsdata);
> - int (*write_end)(struct file *, struct address_space *mapping,
> - loff_t pos, unsigned len, unsigned copied,
> - struct page *page, void *fsdata);
> - sector_t (*bmap)(struct address_space *, sector_t);
> - void (*invalidatepage) (struct page *, unsigned int, unsigned int);
> - int (*releasepage) (struct page *, int);
> - void (*freepage)(struct page *);
> - ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
> - /* isolate a page for migration */
> - bool (*isolate_page) (struct page *, isolate_mode_t);
> - /* migrate the contents of a page to the specified target */
> - int (*migratepage) (struct page *, struct page *);
> - /* put migration-failed page back to right list */
> - void (*putback_page) (struct page *);
> - int (*launder_page) (struct page *);
> -
> - int (*is_partially_uptodate) (struct page *, unsigned long,
> - unsigned long);
> - void (*is_dirty_writeback) (struct page *, bool *, bool *);
> - int (*error_remove_page) (struct mapping *mapping, struct page *page);
> - int (*swap_activate)(struct file *);
> - int (*swap_deactivate)(struct file *);
> -};
> +.. code-block:: c
> +
> + struct address_space_operations {
> + int (*writepage)(struct page *page, struct writeback_control *wbc);
> + int (*readpage)(struct file *, struct page *);
> + int (*writepages)(struct address_space *, struct writeback_control *);
> + int (*set_page_dirty)(struct page *page);
> + int (*readpages)(struct file *filp, struct address_space *mapping,
> + struct list_head *pages, unsigned nr_pages);
> + int (*write_begin)(struct file *, struct address_space *mapping,
> + loff_t pos, unsigned len, unsigned flags,
> + struct page **pagep, void **fsdata);
> + int (*write_end)(struct file *, struct address_space *mapping,
> + loff_t pos, unsigned len, unsigned copied,
> + struct page *page, void *fsdata);
> + sector_t (*bmap)(struct address_space *, sector_t);
> + void (*invalidatepage) (struct page *, unsigned int, unsigned int);
> + int (*releasepage) (struct page *, int);
> + void (*freepage)(struct page *);
> + ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
> + /* isolate a page for migration */
> + bool (*isolate_page) (struct page *, isolate_mode_t);
> + /* migrate the contents of a page to the specified target */
> + int (*migratepage) (struct page *, struct page *);
> + /* put migration-failed page back to right list */
> + void (*putback_page) (struct page *);
> + int (*launder_page) (struct page *);
> +
> + int (*is_partially_uptodate) (struct page *, unsigned long,
> + unsigned long);
> + void (*is_dirty_writeback) (struct page *, bool *, bool *);
> + int (*error_remove_page) (struct mapping *mapping, struct page *page);
> + int (*swap_activate)(struct file *);
> + int (*swap_deactivate)(struct file *);
> + };
>
> - writepage: called by the VM to write a dirty page to backing store.
> This may happen for data integrity reasons (i.e. 'sync'), or
> @@ -852,45 +860,50 @@ struct file_operations
> This describes how the VFS can manipulate an open file. As of kernel
> 4.18, the following members are defined:
>
> -struct file_operations {
> - struct module *owner;
> - loff_t (*llseek) (struct file *, loff_t, int);
> - ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
> - ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
> - ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
> - ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
> - int (*iopoll)(struct kiocb *kiocb, bool spin);
> - int (*iterate) (struct file *, struct dir_context *);
> - int (*iterate_shared) (struct file *, struct dir_context *);
> - __poll_t (*poll) (struct file *, struct poll_table_struct *);
> - long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
> - long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
> - int (*mmap) (struct file *, struct vm_area_struct *);
> - int (*open) (struct inode *, struct file *);
> - int (*flush) (struct file *, fl_owner_t id);
> - int (*release) (struct inode *, struct file *);
> - int (*fsync) (struct file *, loff_t, loff_t, int datasync);
> - int (*fasync) (int, struct file *, int);
> - int (*lock) (struct file *, int, struct file_lock *);
> - ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
> - unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
> - int (*check_flags)(int);
> - int (*flock) (struct file *, int, struct file_lock *);
> - ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
> - ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
> - int (*setlease)(struct file *, long, struct file_lock **, void **);
> - long (*fallocate)(struct file *file, int mode, loff_t offset,
> - loff_t len);
> - void (*show_fdinfo)(struct seq_file *m, struct file *f);
> -#ifndef CONFIG_MMU
> - unsigned (*mmap_capabilities)(struct file *);
> -#endif
> - ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t, size_t, unsigned int);
> - loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
> - struct file *file_out, loff_t pos_out,
> - loff_t len, unsigned int remap_flags);
> - int (*fadvise)(struct file *, loff_t, loff_t, int);
> -};
> +.. code-block:: c
> +
> + struct file_operations {
> + struct module *owner;
> + loff_t (*llseek) (struct file *, loff_t, int);
> + ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
> + ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
> + ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
> + ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
> + int (*iopoll)(struct kiocb *kiocb, bool spin);
> + int (*iterate) (struct file *, struct dir_context *);
> + int (*iterate_shared) (struct file *, struct dir_context *);
> + __poll_t (*poll) (struct file *, struct poll_table_struct *);
> + long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
> + long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
> + int (*mmap) (struct file *, struct vm_area_struct *);
> + int (*open) (struct inode *, struct file *);
> + int (*flush) (struct file *, fl_owner_t id);
> + int (*release) (struct inode *, struct file *);
> + int (*fsync) (struct file *, loff_t, loff_t, int datasync);
> + int (*fasync) (int, struct file *, int);
> + int (*lock) (struct file *, int, struct file_lock *);
> + ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
> + unsigned long (*get_unmapped_area)(struct file *, unsigned long,
> + unsigned long, unsigned long, unsigned long);
> + int (*check_flags)(int);
> + int (*flock) (struct file *, int, struct file_lock *);
> + ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
> + loff_t *, size_t, unsigned int);
> + ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
> + size_t, unsigned int);
> + int (*setlease)(struct file *, long, struct file_lock **, void **);
> + long (*fallocate)(struct file *file, int mode, loff_t offset, loff_t len);
> + void (*show_fdinfo)(struct seq_file *m, struct file *f);
> + #ifndef CONFIG_MMU
> + unsigned (*mmap_capabilities)(struct file *);
> + #endif
> + ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t,
> + size_t, unsigned int);
> + loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
> + struct file *file_out, loff_t pos_out,
> + loff_t len, unsigned int remap_flags);
> + int (*fadvise)(struct file *, loff_t, loff_t, int);
> + };
>
> Again, all methods are called without any locks being held, unless
> otherwise noted.
> @@ -1006,21 +1019,23 @@ here. These methods may be set to NULL, as they are either optional or
> the VFS uses a default. As of kernel 2.6.22, the following members are
> defined:
>
> -struct dentry_operations {
> - int (*d_revalidate)(struct dentry *, unsigned int);
> - int (*d_weak_revalidate)(struct dentry *, unsigned int);
> - int (*d_hash)(const struct dentry *, struct qstr *);
> - int (*d_compare)(const struct dentry *,
> - unsigned int, const char *, const struct qstr *);
> - int (*d_delete)(const struct dentry *);
> - int (*d_init)(struct dentry *);
> - void (*d_release)(struct dentry *);
> - void (*d_iput)(struct dentry *, struct inode *);
> - char *(*d_dname)(struct dentry *, char *, int);
> - struct vfsmount *(*d_automount)(struct path *);
> - int (*d_manage)(const struct path *, bool);
> - struct dentry *(*d_real)(struct dentry *, const struct inode *);
> -};
> +.. code-block:: c
> +
> + struct dentry_operations {
> + int (*d_revalidate)(struct dentry *, unsigned int);
> + int (*d_weak_revalidate)(struct dentry *, unsigned int);
> + int (*d_hash)(const struct dentry *, struct qstr *);
> + int (*d_compare)(const struct dentry *,
> + unsigned int, const char *, const struct qstr *);
> + int (*d_delete)(const struct dentry *);
> + int (*d_init)(struct dentry *);
> + void (*d_release)(struct dentry *);
> + void (*d_iput)(struct dentry *, struct inode *);
> + char *(*d_dname)(struct dentry *, char *, int);
> + struct vfsmount *(*d_automount)(struct path *);
> + int (*d_manage)(const struct path *, bool);
> + struct dentry *(*d_real)(struct dentry *, const struct inode *);
> + };
>
> - d_revalidate: called when the VFS needs to revalidate a dentry. This
> is called whenever a name look-up finds a dentry in the
> @@ -1106,13 +1121,13 @@ struct dentry_operations {
> at the end of the buffer, and returns a pointer to the first char.
> dynamic_dname() helper function is provided to take care of this.
>
> - Example :
> + .. code-block:: c
>
> - static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
> - {
> - return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
> - dentry->d_inode->i_ino);
> - }
> + static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
> + {
> + return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
> + dentry->d_inode->i_ino);
> + }
>
> - d_automount: called when an automount dentry is to be traversed (optional).
> This should create a new VFS mount record and return the record to the
> --
> 2.21.0
>
On Tue, Mar 19, 2019 at 12:35:26PM +1100, Tobin C. Harding wrote:
> On Tue, Mar 19, 2019 at 10:14:33AM +1100, Tobin C. Harding wrote:
> > Use code-block for C source code. With this in place we can rename the
> > .txt file to .rst. This introduces a few warnings that will be fixed
> > in proceeding patches.
> >
> > Add '.. code-block:: c' to C source code snippets. Rename the file to
> > use rst file suffix.
>
> I just realised that a better way to document these structs is to do so
> above the actual struct definition in the source file then include those
> docs in the documentation file.
Please either drop this set or only consider patches 1-8 for merge. I
haven't worked out _exactly_ how to move the docs from
Documentation/filesystems/vfs to the source code files but I've played
with it enough now to feel it is possible and it is definitely better.
Just have to massage Sphinx into agreeing with me.
I thought the whole reason we have docstring comments is because we all
agreed that docs close to code hove more chance of staying relevant.
vfs.txt proves that nicely (docs in it from 2.6 for structs that are
actively used and developed).
Sorry for the noise, one day I'll work these things out _before_ sending
the patches :)
thanks,
Tobin.