This documentation for ->swap_activate() has been out-of-date for a long
time. This patch updates it to match recent changes, and adds
documentation for the associated ->swap_rw()
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: NeilBrown <[email protected]>
---
Documentation/filesystems/locking.rst | 18 ++++++++++++------
Documentation/filesystems/vfs.rst | 17 ++++++++++++-----
2 files changed, 24 insertions(+), 11 deletions(-)
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 3f9b1497ebb8..fbb10378d5ee 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -260,8 +260,9 @@ prototypes::
int (*launder_page)(struct page *);
int (*is_partially_uptodate)(struct page *, unsigned long, unsigned long);
int (*error_remove_page)(struct address_space *, struct page *);
- int (*swap_activate)(struct file *);
+ int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span)
int (*swap_deactivate)(struct file *);
+ int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter);
locking rules:
All except set_page_dirty and freepage may block
@@ -290,6 +291,7 @@ is_partially_uptodate: yes
error_remove_page: yes
swap_activate: no
swap_deactivate: no
+swap_rw: yes, unlocks
====================== ======================== ========= ===============
->write_begin(), ->write_end() and ->readpage() may be called from
@@ -392,15 +394,19 @@ cleaned, or an error value if not. Note that in order to prevent the page
getting mapped back in and redirtied, it needs to be kept locked
across the entire operation.
-->swap_activate will be called with a non-zero argument on
-files backing (non block device backed) swapfiles. A return value
-of zero indicates success, in which case this file can be used for
-backing swapspace. The swapspace operations will be proxied to the
-address space operations.
+->swap_activate() will be called to prepare the given file for swap. It
+should perform any validation and preparation necessary to ensure that
+writes can be performed with minimal memory allocation. It should call
+add_swap_extent(), or the helper iomap_swapfile_activate(), and return
+the number of extents added. If IO should be submitted through
+->swap_rw(), it should set SWP_FS_OPS, otherwise IO will be submitted
+directly to the block device ``sis->bdev``.
->swap_deactivate() will be called in the sys_swapoff()
path after ->swap_activate() returned success.
+->swap_rw will be called for swap IO if SWP_FS_OPS was set by ->swap_activate().
+
file_lock_operations
====================
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index bf5c48066fac..779d23fc7954 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -751,8 +751,9 @@ cache in your filesystem. The following members are defined:
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_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span)
int (*swap_deactivate)(struct file *);
+ int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter);
};
``writepage``
@@ -959,15 +960,21 @@ cache in your filesystem. The following members are defined:
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.
+
+ Called to prepare the given file for swap. It should perform
+ any validation and preparation necessary to ensure that writes
+ can be performed with minimal memory allocation. It should call
+ add_swap_extent(), or the helper iomap_swapfile_activate(), and
+ return the number of extents added. If IO should be submitted
+ through ->swap_rw(), it should set SWP_FS_OPS, otherwise IO will
+ be submitted directly to the block device ``sis->bdev``.
``swap_deactivate``
Called during swapoff on files where swap_activate was
successful.
+``swap_rw``
+ Called to read or write swap pages when SWP_FS_OPS is set.
The File Object
===============