zonefs is a very simple file system exposing each zone of a zoned block
device as a file. Unlike a regular file system with zoned block device
support (e.g. f2fs or the on-going btrfs effort), zonefs does not hide
the sequential write constraint of zoned block devices to the user.
Files representing sequential write zones of the device must be written
sequentially starting from the end of the file (append only writes).
zonefs is not a POSIX compliant file system. It's goal is to simplify
the implementation of zoned block devices support in applications by
replacing raw block device file accesses with a richer file based API,
avoiding relying on direct block device file ioctls which may
be more obscure to developers. One example of this approach is the
implementation of LSM (log-structured merge) tree structures (such as
used in RocksDB and LevelDB) on zoned block devices by allowing SSTables
to be stored in a zone file similarly to a regular file system rather
than as a range of sectors of a zoned device. The introduction of the
higher level construct "one file is one zone" can help reducing the
amount of changes needed in the application while at the same time
allowing the use of zoned block devices with various programming
languages other than C.
zonefs IO management implementation uses the new iomap generic code.
Changes from v9:
* Changed mount options to ia more useful set of possible actions for
zone corruption handling: repair, remount-ro, zone-ro or zone-offline
* Check IMMUTABLE inodes to prevent write operations
* Documented mount options
Changes from v8:
* Comments typos fixes and improvements as suggested by Darrick and
Dave.
* Improved IO error handling:
- Better sequential file write pointer checks on write IO error
- Extended zone condition checks on IO error to all types of IOs
- Added mount options for controlling the FS behavior when a zone
write pointer corruption is detected.
* Cleanup zonefs_iomap_begin() and its use in zonefs_map_blocks()
* Ignore RWF_NOWAIT to avoid out of order writes on sequential zone
files.
* Improved documentation file
Changes from v7:
* Fixed static checker warnings:
- Set-but-not-used variable in zonefs_file_buffered_write()
- Use S_ISDIR() in zonefs_inode_setattr()
Changes from v6:
* Fixed documentation as suggested by Randy.
Changes from v5:
* Added simple description of zoned block devices to the documentation,
as suggested by Johannes.
* Added a 64-char max label field to the super block to allow label
based identification of volumes using libblkid (checked with a patch
to libblkid).
Changes from v4:
* Use octal values for file and directory permissions
* Set initial directory permissions to 0555 (no write permission)
* Prevent setting write permissions for directories
Changes from v3:
* Fixed many typos in the documentation
* Use symbolic file permission macros instead of octal values
(checkpatch.pl complains about this)
Changes from v2:
* Address comments and suggestions from Darrick:
- Make the inode of OFFLINE and READONLY zones immutable when
mounting. Also do this during zone information check after an IO
error.
- Change super block CRC seed to ~0.
- Avoid potential compiler warning in zonefs_create_zgroup().
* Fixed endianness related compilation warning detected by kbuild bot.
Changes from v1:
* Fixed comment typo
* Improved documentation as suggested by Hannes
Damien Le Moal (2):
fs: New zonefs file system
zonefs: Add documentation
Documentation/filesystems/zonefs.txt | 301 ++++++
MAINTAINERS | 10 +
fs/Kconfig | 1 +
fs/Makefile | 1 +
fs/zonefs/Kconfig | 9 +
fs/zonefs/Makefile | 4 +
fs/zonefs/super.c | 1427 ++++++++++++++++++++++++++
fs/zonefs/zonefs.h | 192 ++++
include/uapi/linux/magic.h | 1 +
9 files changed, 1946 insertions(+)
create mode 100644 Documentation/filesystems/zonefs.txt
create mode 100644 fs/zonefs/Kconfig
create mode 100644 fs/zonefs/Makefile
create mode 100644 fs/zonefs/super.c
create mode 100644 fs/zonefs/zonefs.h
--
2.24.1
zonefs is a very simple file system exposing each zone of a zoned block
device as a file. Unlike a regular file system with zoned block device
support (e.g. f2fs), zonefs does not hide the sequential write
constraint of zoned block devices to the user. Files representing
sequential write zones of the device must be written sequentially
starting from the end of the file (append only writes).
As such, zonefs is in essence closer to a raw block device access
interface than to a full featured POSIX file system. The goal of zonefs
is to simplify the implementation of zoned block device support in
applications by replacing raw block device file accesses with a richer
file API, avoiding relying on direct block device file ioctls which may
be more obscure to developers. One example of this approach is the
implementation of LSM (log-structured merge) tree structures (such as
used in RocksDB and LevelDB) on zoned block devices by allowing SSTables
to be stored in a zone file similarly to a regular file system rather
than as a range of sectors of a zoned device. The introduction of the
higher level construct "one file is one zone" can help reducing the
amount of changes needed in the application as well as introducing
support for different application programming languages.
Zonefs on-disk metadata is reduced to an immutable super block to
persistently store a magic number and optional feature flags and
values. On mount, zonefs uses blkdev_report_zones() to obtain the device
zone configuration and populates the mount point with a static file tree
solely based on this information. E.g. file sizes come from the device
zone type and write pointer offset managed by the device itself.
The zone files created on mount have the following characteristics.
1) Files representing zones of the same type are grouped together
under a common sub-directory:
* For conventional zones, the sub-directory "cnv" is used.
* For sequential write zones, the sub-directory "seq" is used.
These two directories are the only directories that exist in zonefs.
Users cannot create other directories and cannot rename nor delete
the "cnv" and "seq" sub-directories.
2) The name of zone files is the number of the file within the zone
type sub-directory, in order of increasing zone start sector.
3) The size of conventional zone files is fixed to the device zone size.
Conventional zone files cannot be truncated.
4) The size of sequential zone files represent the file's zone write
pointer position relative to the zone start sector. Truncating these
files is allowed only down to 0, in which case, the zone is reset to
rewind the zone write pointer position to the start of the zone, or
up to the zone size, in which case the file's zone is transitioned
to the FULL state (finish zone operation).
5) All read and write operations to files are not allowed beyond the
file zone size. Any access exceeding the zone size is failed with
the -EFBIG error.
6) Creating, deleting, renaming or modifying any attribute of files and
sub-directories is not allowed.
7) There are no restrictions on the type of read and write operations
that can be issued to conventional zone files. Buffered, direct and
mmap read & write operations are accepted. For sequential zone files,
there are no restrictions on read operations, but all write
operations must be direct IO append writes. mmap write of sequential
files is not allowed.
Several optional features of zonefs can be enabled at format time.
* Conventional zone aggregation: ranges of contiguous conventional
zones can be aggregated into a single larger file instead of the
default one file per zone.
* File ownership: The owner UID and GID of zone files is by default 0
(root) but can be changed to any valid UID/GID.
* File access permissions: the default 640 access permissions can be
changed.
The mkzonefs tool is used to format zoned block devices for use with
zonefs. This tool is available on Github at:
[email protected]:damien-lemoal/zonefs-tools.git.
zonefs-tools also includes a test suite which can be run against any
zoned block device, including null_blk block device created with zoned
mode.
Example: the following formats a 15TB host-managed SMR HDD with 256 MB
zones with the conventional zones aggregation feature enabled.
$ sudo mkzonefs -o aggr_cnv /dev/sdX
$ sudo mount -t zonefs /dev/sdX /mnt
$ ls -l /mnt/
total 0
dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
The size of the zone files sub-directories indicate the number of files
existing for each type of zones. In this example, there is only one
conventional zone file (all conventional zones are aggregated under a
single file).
$ ls -l /mnt/cnv
total 137101312
-rw-r----- 1 root root 140391743488 Nov 25 13:23 0
This aggregated conventional zone file can be used as a regular file.
$ sudo mkfs.ext4 /mnt/cnv/0
$ sudo mount -o loop /mnt/cnv/0 /data
The "seq" sub-directory grouping files for sequential write zones has
in this example 55356 zones.
$ ls -lv /mnt/seq
total 14511243264
-rw-r----- 1 root root 0 Nov 25 13:23 0
-rw-r----- 1 root root 0 Nov 25 13:23 1
-rw-r----- 1 root root 0 Nov 25 13:23 2
...
-rw-r----- 1 root root 0 Nov 25 13:23 55354
-rw-r----- 1 root root 0 Nov 25 13:23 55355
For sequential write zone files, the file size changes as data is
appended at the end of the file, similarly to any regular file system.
$ dd if=/dev/zero of=/mnt/seq/0 bs=4K count=1 conv=notrunc oflag=direct
1+0 records in
1+0 records out
4096 bytes (4.1 kB, 4.0 KiB) copied, 0.000452219 s, 9.1 MB/s
$ ls -l /mnt/seq/0
-rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
The written file can be truncated to the zone size, preventing any
further write operation.
$ truncate -s 268435456 /mnt/seq/0
$ ls -l /mnt/seq/0
-rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
Truncation to 0 size allows freeing the file zone storage space and
restart append-writes to the file.
$ truncate -s 0 /mnt/seq/0
$ ls -l /mnt/seq/0
-rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
Since files are statically mapped to zones on the disk, the number of
blocks of a file as reported by stat() and fstat() indicates the size
of the file zone.
$ stat /mnt/seq/0
File: /mnt/seq/0
Size: 0 Blocks: 524288 IO Block: 4096 regular empty file
Device: 870h/2160d Inode: 50431 Links: 1
Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2019-11-25 13:23:57.048971997 +0900
Modify: 2019-11-25 13:52:25.553805765 +0900
Change: 2019-11-25 13:52:25.553805765 +0900
Birth: -
The number of blocks of the file ("Blocks") in units of 512B blocks
gives the maximum file size of 524288 * 512 B = 256 MB, corresponding
to the device zone size in this example. Of note is that the "IO block"
field always indicates the minimum IO size for writes and corresponds
to the device physical sector size.
This code contains contributions from:
* Johannes Thumshirn <[email protected]>,
* Darrick J. Wong <[email protected]>,
* Christoph Hellwig <[email protected]>,
* Chaitanya Kulkarni <[email protected]> and
* Ting Yao <[email protected]>.
Signed-off-by: Damien Le Moal <[email protected]>
---
MAINTAINERS | 9 +
fs/Kconfig | 1 +
fs/Makefile | 1 +
fs/zonefs/Kconfig | 9 +
fs/zonefs/Makefile | 4 +
fs/zonefs/super.c | 1427 ++++++++++++++++++++++++++++++++++++
fs/zonefs/zonefs.h | 192 +++++
include/uapi/linux/magic.h | 1 +
8 files changed, 1644 insertions(+)
create mode 100644 fs/zonefs/Kconfig
create mode 100644 fs/zonefs/Makefile
create mode 100644 fs/zonefs/super.c
create mode 100644 fs/zonefs/zonefs.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 56765f542244..089fd879632a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18303,6 +18303,15 @@ L: [email protected]
S: Maintained
F: arch/x86/kernel/cpu/zhaoxin.c
+ZONEFS FILESYSTEM
+M: Damien Le Moal <[email protected]>
+M: Naohiro Aota <[email protected]>
+R: Johannes Thumshirn <[email protected]>
+L: [email protected]
+T: git git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/zonefs.git
+S: Maintained
+F: fs/zonefs/
+
ZPOOL COMPRESSED PAGE STORAGE API
M: Dan Streetman <[email protected]>
L: [email protected]
diff --git a/fs/Kconfig b/fs/Kconfig
index 7b623e9fc1b0..a3f97ca2bd46 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -40,6 +40,7 @@ source "fs/ocfs2/Kconfig"
source "fs/btrfs/Kconfig"
source "fs/nilfs2/Kconfig"
source "fs/f2fs/Kconfig"
+source "fs/zonefs/Kconfig"
config FS_DAX
bool "Direct Access (DAX) support"
diff --git a/fs/Makefile b/fs/Makefile
index 1148c555c4d3..527f228a5e8a 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -133,3 +133,4 @@ obj-$(CONFIG_CEPH_FS) += ceph/
obj-$(CONFIG_PSTORE) += pstore/
obj-$(CONFIG_EFIVAR_FS) += efivarfs/
obj-$(CONFIG_EROFS_FS) += erofs/
+obj-$(CONFIG_ZONEFS_FS) += zonefs/
diff --git a/fs/zonefs/Kconfig b/fs/zonefs/Kconfig
new file mode 100644
index 000000000000..fb87ad372e29
--- /dev/null
+++ b/fs/zonefs/Kconfig
@@ -0,0 +1,9 @@
+config ZONEFS_FS
+ tristate "zonefs filesystem support"
+ depends on BLOCK
+ depends on BLK_DEV_ZONED
+ help
+ zonefs is a simple file system which exposes zones of a zoned block
+ device (e.g. host-managed or host-aware SMR disk drives) as files.
+
+ If unsure, say N.
diff --git a/fs/zonefs/Makefile b/fs/zonefs/Makefile
new file mode 100644
index 000000000000..75a380aa1ae1
--- /dev/null
+++ b/fs/zonefs/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_ZONEFS_FS) += zonefs.o
+
+zonefs-y := super.o
diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
new file mode 100644
index 000000000000..5232878d7919
--- /dev/null
+++ b/fs/zonefs/super.c
@@ -0,0 +1,1427 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple file system for zoned block devices exposing zones as files.
+ *
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/iomap.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/statfs.h>
+#include <linux/writeback.h>
+#include <linux/quotaops.h>
+#include <linux/seq_file.h>
+#include <linux/parser.h>
+#include <linux/uio.h>
+#include <linux/mman.h>
+#include <linux/sched/mm.h>
+#include <linux/crc32.h>
+
+#include "zonefs.h"
+
+static int zonefs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
+ unsigned int flags, struct iomap *iomap,
+ struct iomap *srcmap)
+{
+ struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ loff_t isize;
+
+ /* All I/Os should always be within the file maximum size */
+ if (WARN_ON_ONCE(offset + length > zi->i_max_size))
+ return -EIO;
+
+ /*
+ * Sequential zones can only accept direct writes. This is already
+ * checked when writes are issued, so warn about writeback operations.
+ */
+ if (WARN_ON_ONCE(zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
+ (flags & IOMAP_WRITE) && !(flags & IOMAP_DIRECT)))
+ return -EIO;
+
+ /*
+ * For conventional zones, all blocks are always mapped.
+ * For sequential zones, all blocks after always mapped below the
+ * inode size (zone write pointer) and unwriten beyond.
+ */
+ mutex_lock(&zi->i_truncate_mutex);
+ isize = i_size_read(inode);
+ if (offset >= isize)
+ iomap->type = IOMAP_UNWRITTEN;
+ else
+ iomap->type = IOMAP_MAPPED;
+ if (flags & IOMAP_WRITE)
+ length = zi->i_max_size - offset;
+ else
+ length = min(length, isize - offset);
+ mutex_unlock(&zi->i_truncate_mutex);
+
+ iomap->offset = offset & (~sbi->s_blocksize_mask);
+ iomap->length = ((offset + length + sbi->s_blocksize_mask) &
+ (~sbi->s_blocksize_mask)) - iomap->offset;
+ iomap->bdev = inode->i_sb->s_bdev;
+ iomap->addr = (zi->i_zsector << SECTOR_SHIFT) + iomap->offset;
+
+ return 0;
+}
+
+static const struct iomap_ops zonefs_iomap_ops = {
+ .iomap_begin = zonefs_iomap_begin,
+};
+
+static int zonefs_readpage(struct file *unused, struct page *page)
+{
+ return iomap_readpage(page, &zonefs_iomap_ops);
+}
+
+static int zonefs_readpages(struct file *unused, struct address_space *mapping,
+ struct list_head *pages, unsigned int nr_pages)
+{
+ return iomap_readpages(mapping, pages, nr_pages, &zonefs_iomap_ops);
+}
+
+/*
+ * Map blocks for page writeback. This is used only on conventional zone files,
+ * which implies that the page range can only be within the fixed inode size.
+ */
+static int zonefs_map_blocks(struct iomap_writepage_ctx *wpc,
+ struct inode *inode, loff_t offset)
+{
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+
+ if (WARN_ON_ONCE(zi->i_ztype != ZONEFS_ZTYPE_CNV))
+ return -EIO;
+ if (WARN_ON_ONCE(offset >= i_size_read(inode)))
+ return -EIO;
+
+ /* If the mapping is already OK, nothing needs to be done */
+ if (offset >= wpc->iomap.offset &&
+ offset < wpc->iomap.offset + wpc->iomap.length)
+ return 0;
+
+ return zonefs_iomap_begin(inode, offset, zi->i_max_size - offset,
+ IOMAP_WRITE, &wpc->iomap, NULL);
+}
+
+static const struct iomap_writeback_ops zonefs_writeback_ops = {
+ .map_blocks = zonefs_map_blocks,
+};
+
+static int zonefs_writepage(struct page *page, struct writeback_control *wbc)
+{
+ struct iomap_writepage_ctx wpc = { };
+
+ return iomap_writepage(page, wbc, &wpc, &zonefs_writeback_ops);
+}
+
+static int zonefs_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ struct iomap_writepage_ctx wpc = { };
+
+ return iomap_writepages(mapping, wbc, &wpc, &zonefs_writeback_ops);
+}
+
+static const struct address_space_operations zonefs_file_aops = {
+ .readpage = zonefs_readpage,
+ .readpages = zonefs_readpages,
+ .writepage = zonefs_writepage,
+ .writepages = zonefs_writepages,
+ .set_page_dirty = iomap_set_page_dirty,
+ .releasepage = iomap_releasepage,
+ .invalidatepage = iomap_invalidatepage,
+ .migratepage = iomap_migrate_page,
+ .is_partially_uptodate = iomap_is_partially_uptodate,
+ .error_remove_page = generic_error_remove_page,
+ .direct_IO = noop_direct_IO,
+};
+
+static void zonefs_update_stats(struct inode *inode, loff_t new_isize)
+{
+ struct super_block *sb = inode->i_sb;
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ loff_t old_isize = i_size_read(inode);
+ loff_t nr_blocks;
+
+ if (new_isize == old_isize)
+ return;
+
+ spin_lock(&sbi->s_lock);
+
+ /*
+ * This may be called for an IO error recovery update.
+ * So beware of the values seen.
+ */
+ if (new_isize < old_isize) {
+ nr_blocks = (old_isize - new_isize) >> sb->s_blocksize_bits;
+ if (sbi->s_used_blocks > nr_blocks)
+ sbi->s_used_blocks -= nr_blocks;
+ else
+ sbi->s_used_blocks = 0;
+ } else {
+ sbi->s_used_blocks +=
+ (new_isize - old_isize) >> sb->s_blocksize_bits;
+ if (sbi->s_used_blocks > sbi->s_blocks)
+ sbi->s_used_blocks = sbi->s_blocks;
+ }
+
+ spin_unlock(&sbi->s_lock);
+}
+
+static int zonefs_file_truncate(struct inode *inode, loff_t isize)
+{
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ loff_t old_isize;
+ enum req_opf op;
+ int ret = 0;
+
+ /*
+ * Only sequential zone files can be truncated and Truncation is allowed
+ * only down to a 0 size, which is equivalent to a zone reset, and to
+ * the maximum file size, which is equivalent to a zone finish.
+ */
+ if (zi->i_ztype != ZONEFS_ZTYPE_SEQ)
+ return -EPERM;
+
+ if (!isize)
+ op = REQ_OP_ZONE_RESET;
+ else if (isize == zi->i_max_size)
+ op = REQ_OP_ZONE_FINISH;
+ else
+ return -EPERM;
+
+ inode_dio_wait(inode);
+
+ /* Serialize against page faults */
+ down_write(&zi->i_mmap_sem);
+
+ /* Serialize against zonefs_iomap_begin() */
+ mutex_lock(&zi->i_truncate_mutex);
+
+ old_isize = i_size_read(inode);
+ if (isize == old_isize)
+ goto unlock;
+
+ ret = blkdev_zone_mgmt(inode->i_sb->s_bdev, op, zi->i_zsector,
+ zi->i_max_size >> SECTOR_SHIFT, GFP_NOFS);
+ if (ret) {
+ zonefs_err(inode->i_sb,
+ "Zone management operation at %llu failed %d",
+ zi->i_zsector, ret);
+ goto unlock;
+ }
+
+ zonefs_update_stats(inode, isize);
+ truncate_setsize(inode, isize);
+ zi->i_wpoffset = isize;
+
+unlock:
+ mutex_unlock(&zi->i_truncate_mutex);
+ up_write(&zi->i_mmap_sem);
+
+ return ret;
+}
+
+static int zonefs_inode_setattr(struct dentry *dentry, struct iattr *iattr)
+{
+ struct inode *inode = d_inode(dentry);
+ int ret;
+
+ if (unlikely(IS_IMMUTABLE(inode)))
+ return -EPERM;
+
+ ret = setattr_prepare(dentry, iattr);
+ if (ret)
+ return ret;
+
+ /*
+ * Since files and directories cannot be created nor deleted, do not
+ * allow setting any write attributes on the zone types sub-directories.
+ */
+ if ((iattr->ia_valid & ATTR_MODE) && S_ISDIR(inode->i_mode) &&
+ (iattr->ia_mode & 0222))
+ return -EPERM;
+
+ if (((iattr->ia_valid & ATTR_UID) &&
+ !uid_eq(iattr->ia_uid, inode->i_uid)) ||
+ ((iattr->ia_valid & ATTR_GID) &&
+ !gid_eq(iattr->ia_gid, inode->i_gid))) {
+ ret = dquot_transfer(inode, iattr);
+ if (ret)
+ return ret;
+ }
+
+ if (iattr->ia_valid & ATTR_SIZE) {
+ ret = zonefs_file_truncate(inode, iattr->ia_size);
+ if (ret)
+ return ret;
+ }
+
+ setattr_copy(inode, iattr);
+
+ return 0;
+}
+
+static const struct inode_operations zonefs_file_inode_operations = {
+ .setattr = zonefs_inode_setattr,
+};
+
+static int zonefs_file_fsync(struct file *file, loff_t start, loff_t end,
+ int datasync)
+{
+ struct inode *inode = file_inode(file);
+ int ret = 0;
+
+ if (unlikely(IS_IMMUTABLE(inode)))
+ return -EPERM;
+
+ /*
+ * Since only direct writes are allowed in sequential files, page cache
+ * flush is needed only for conventional zone files.
+ */
+ if (ZONEFS_I(inode)->i_ztype == ZONEFS_ZTYPE_CNV) {
+ ret = file_write_and_wait_range(file, start, end);
+ if (ret)
+ return ret;
+ ret = file_check_and_advance_wb_err(file);
+ }
+
+ if (ret == 0)
+ ret = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
+
+ return ret;
+}
+
+static vm_fault_t zonefs_filemap_fault(struct vm_fault *vmf)
+{
+ struct zonefs_inode_info *zi = ZONEFS_I(file_inode(vmf->vma->vm_file));
+ vm_fault_t ret;
+
+ down_read(&zi->i_mmap_sem);
+ ret = filemap_fault(vmf);
+ up_read(&zi->i_mmap_sem);
+
+ return ret;
+}
+
+static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
+{
+ struct inode *inode = file_inode(vmf->vma->vm_file);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ vm_fault_t ret;
+
+ if (unlikely(IS_IMMUTABLE(inode)))
+ return VM_FAULT_SIGBUS;
+
+ /*
+ * Sanity check: only conventional zone files can have shared
+ * writeable mappings.
+ */
+ if (WARN_ON_ONCE(zi->i_ztype != ZONEFS_ZTYPE_CNV))
+ return VM_FAULT_NOPAGE;
+
+ sb_start_pagefault(inode->i_sb);
+ file_update_time(vmf->vma->vm_file);
+
+ /* Serialize against truncates */
+ down_read(&zi->i_mmap_sem);
+ ret = iomap_page_mkwrite(vmf, &zonefs_iomap_ops);
+ up_read(&zi->i_mmap_sem);
+
+ sb_end_pagefault(inode->i_sb);
+ return ret;
+}
+
+static const struct vm_operations_struct zonefs_file_vm_ops = {
+ .fault = zonefs_filemap_fault,
+ .map_pages = filemap_map_pages,
+ .page_mkwrite = zonefs_filemap_page_mkwrite,
+};
+
+static int zonefs_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ /*
+ * Conventional zones accept random writes, so their files can support
+ * shared writable mappings. For sequential zone files, only read
+ * mappings are possible since there are no guarantees for write
+ * ordering with msync() and page cache writeback.
+ */
+ if (ZONEFS_I(file_inode(file))->i_ztype == ZONEFS_ZTYPE_SEQ &&
+ (vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+ return -EINVAL;
+
+ file_accessed(file);
+ vma->vm_ops = &zonefs_file_vm_ops;
+
+ return 0;
+}
+
+static loff_t zonefs_file_llseek(struct file *file, loff_t offset, int whence)
+{
+ loff_t isize = i_size_read(file_inode(file));
+
+ /*
+ * Seeks are limited to below the zone size for conventional zones
+ * and below the zone write pointer for sequential zones. In both
+ * cases, this limit is the inode size.
+ */
+ return generic_file_llseek_size(file, offset, whence, isize, isize);
+}
+
+/*
+ * Check a zone condition and adjust its file inode access permissions for
+ * offline and readonly zones. Return the inode size corresponding to the
+ * amount of readable data in the zone.
+ */
+static loff_t zonefs_check_zone_condition(struct inode *inode,
+ struct blk_zone *zone)
+{
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+
+ switch (zone->cond) {
+ case BLK_ZONE_COND_OFFLINE:
+ /*
+ * Dead zone: make the inode immutable, disable all accesses
+ * and set the file size to 0 (zone wp set to zone start).
+ */
+ zonefs_warn(inode->i_sb, "inode %lu: offline zone\n",
+ inode->i_ino);
+ inode->i_flags |= S_IMMUTABLE;
+ inode->i_mode &= ~0777;
+ zone->wp = zone->start;
+ return 0;
+ case BLK_ZONE_COND_READONLY:
+ /* Do not allow writes in read-only zones */
+ zonefs_warn(inode->i_sb, "inode %lu: read-only zone\n",
+ inode->i_ino);
+ inode->i_flags |= S_IMMUTABLE;
+ inode->i_mode &= ~0222;
+ /* fallthrough */
+ default:
+ if (zi->i_ztype == ZONEFS_ZTYPE_CNV)
+ return zi->i_max_size;
+ return (zone->wp - zone->start) << SECTOR_SHIFT;
+ }
+}
+
+struct zonefs_ioerr_data {
+ struct inode *inode;
+ bool write;
+};
+
+static int zonefs_io_err_cb(struct blk_zone *zone, unsigned int idx, void *data)
+{
+ struct zonefs_ioerr_data *ioerr = data;
+ struct inode *inode = ioerr->inode;
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ struct super_block *sb = inode->i_sb;
+ loff_t isize, wp_ofst;
+
+
+ /*
+ * The condition of the zone may have change. Fix the file access
+ * permissions if necessary. For dead zones (offline zones), no recovery
+ * can be done so return early.
+ */
+ wp_ofst = zonefs_check_zone_condition(inode, zone);
+
+ /*
+ * There is no write pointer on conventional zones and read operations
+ * do not change a zone write pointer, so no further checks are needed.
+ * The same applies if the device reported that the zone went offline
+ * or read only: we need to handle this event regardless of the mount
+ * options specified for error handling.
+ */
+ if (zi->i_ztype == ZONEFS_ZTYPE_CNV ||
+ !ioerr->write ||
+ zone->cond == BLK_ZONE_COND_OFFLINE ||
+ zone->cond == BLK_ZONE_COND_READONLY)
+ goto update_stats;
+
+ /*
+ * For sequential zones write, make sure that the zone write pointer
+ * position is as expected, that is, in sync with the inode size.
+ */
+ zi->i_wpoffset = wp_ofst;
+ isize = i_size_read(inode);
+ if (isize == wp_ofst)
+ return 0;
+
+ /*
+ * The inode size and the zone write pointer are not in sync. Two cases
+ * need to be considered (Note: WP == write pointer):
+ * 1) The inode size is below the zone WP: data was writen at the end of
+ * the file despite the failed IO. This can happen in the case of a
+ * partial write failure of a large DIO needing several BIOs and/or
+ * write requests to be processed. Since the zone WP position
+ * relative to the zone start always indicates the amount of data
+ * written (and readable) in the zone, simply increase the inode
+ * size to reflect the amount of readable data that was writen.
+ * 2) The inode size is over the zone WP: this can only happen if there
+ * was an external corruption, e.g. an application reset the zone
+ * directly, or if the device has a serious problem (e.g. FW bug).
+ * For this case, act based on mount options: remount readonly, set
+ * the zone readonly or set the zone offline.
+ */
+ zonefs_warn(sb, "inode %lu: size %lld should be %lld\n",
+ inode->i_ino, isize, wp_ofst);
+
+ if (isize > wp_ofst) {
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ const char *action = NULL;
+
+ if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_REPAIR) {
+ action = ", file repaired";
+ } else if ((sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_RO) &&
+ !sb_rdonly(sb)) {
+ action = ", remounting fs read-only";
+ sb->s_flags |= SB_RDONLY;
+ } else if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZRO) {
+ action = ", zone file changed to read-only";
+ zone->cond = BLK_ZONE_COND_READONLY;
+ } else if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZOL) {
+ action = ", zone file read/write access disabled";
+ zone->cond = BLK_ZONE_COND_OFFLINE;
+ }
+
+ wp_ofst = zonefs_check_zone_condition(inode, zone);
+
+ if (action)
+ zonefs_warn(sb, "Zone %lu corruption detected%s\n",
+ inode->i_ino, action);
+ }
+
+update_stats:
+ zonefs_update_stats(inode, wp_ofst);
+ i_size_write(inode, wp_ofst);
+
+ return 0;
+}
+
+/*
+ * When an IO error occurs, check the target zone to see if there is a change
+ * in the zone condition (e.g. offline or read-only). For a failed write to a
+ * sequential zone, the zone write pointer position must also be checked to
+ * eventually correct the file size and zonefs inode write pointer offset
+ * (which can be out of sync with the drive due to partial write failures).
+ */
+static void zonefs_io_error(struct inode *inode, bool write)
+{
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ struct super_block *sb = inode->i_sb;
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ unsigned int noio_flag;
+ unsigned int nr_zones =
+ zi->i_max_size >> (sbi->s_zone_sectors_shift + SECTOR_SHIFT);
+ struct zonefs_ioerr_data ioerr = {
+ .inode = inode,
+ .write = write
+ };
+ int ret;
+
+ mutex_lock(&zi->i_truncate_mutex);
+
+ /*
+ * Memory allocations in blkdev_report_zones() can trigger a memory
+ * reclaim which may in turn cause a recursion into zonefs as well as
+ * BIO allocations for the same device. The former case may end up in
+ * a deadlock on the inode truncate mutex, while the latter may prevent
+ * forward progress with BIO and struct request allocations. Executing
+ * the report zones under GFP_NOIO context avoids both problems.
+ */
+ noio_flag = memalloc_noio_save();
+ ret = blkdev_report_zones(sb->s_bdev, zi->i_zsector, nr_zones,
+ zonefs_io_err_cb, &ioerr);
+ if (ret != nr_zones)
+ zonefs_err(sb, "Get inode %lu zone information failed %d\n",
+ inode->i_ino, ret);
+ memalloc_noio_restore(noio_flag);
+
+ mutex_unlock(&zi->i_truncate_mutex);
+}
+
+static int zonefs_file_write_dio_end_io(struct kiocb *iocb, ssize_t size,
+ int error, unsigned int flags)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+
+ if (error) {
+ zonefs_io_error(inode, true);
+ return error;
+ }
+
+ if (size && zi->i_ztype != ZONEFS_ZTYPE_CNV) {
+ /*
+ * Note that we may be seeing completions out of order,
+ * but that is not a problem since a write completed
+ * successfully necessarily means that all preceding writes
+ * were also successful. So we can safely increase the inode
+ * size to the write end location.
+ */
+ mutex_lock(&zi->i_truncate_mutex);
+ if (i_size_read(inode) < iocb->ki_pos + size) {
+ zonefs_update_stats(inode, iocb->ki_pos + size);
+ i_size_write(inode, iocb->ki_pos + size);
+ }
+ mutex_unlock(&zi->i_truncate_mutex);
+ }
+
+ return 0;
+}
+
+static const struct iomap_dio_ops zonefs_write_dio_ops = {
+ .end_io = zonefs_file_write_dio_end_io,
+};
+
+/*
+ * Handle direct writes. For sequential zone files, this is the only possible
+ * write path. For these files, check that the user is issuing writes
+ * sequentially from the end of the file. This code assumes that the block layer
+ * delivers write requests to the device in sequential order. This is always the
+ * case if a block IO scheduler implementing the ELEVATOR_F_ZBD_SEQ_WRITE
+ * elevator feature is being used (e.g. mq-deadline). The block layer always
+ * automatically select such an elevator for zoned block devices during the
+ * device initialization.
+ */
+static ssize_t zonefs_file_dio_write(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ size_t count;
+ ssize_t ret;
+
+ /*
+ * For async direct IOs to sequential zone files, ignore IOCB_NOWAIT
+ * as this can cause write reordering (e.g. the first aio gets EAGAIN
+ * on the inode lock but the second goes through but is now unaligned).
+ */
+ if (zi->i_ztype == ZONEFS_ZTYPE_SEQ && !is_sync_kiocb(iocb)
+ && (iocb->ki_flags & IOCB_NOWAIT))
+ iocb->ki_flags &= ~IOCB_NOWAIT;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!inode_trylock(inode))
+ return -EAGAIN;
+ } else {
+ inode_lock(inode);
+ }
+
+ ret = generic_write_checks(iocb, from);
+ if (ret <= 0)
+ goto inode_unlock;
+
+ iov_iter_truncate(from, zi->i_max_size - iocb->ki_pos);
+ count = iov_iter_count(from);
+
+ if ((iocb->ki_pos | count) & sbi->s_blocksize_mask) {
+ ret = -EINVAL;
+ goto inode_unlock;
+ }
+
+ /* Enforce sequential writes (append only) in sequential zones */
+ mutex_lock(&zi->i_truncate_mutex);
+ if (zi->i_ztype == ZONEFS_ZTYPE_SEQ && iocb->ki_pos != zi->i_wpoffset) {
+ zonefs_err(inode->i_sb,
+ "Unaligned direct write at %llu + %zu (wp %llu)\n",
+ iocb->ki_pos, count,
+ zi->i_wpoffset);
+ mutex_unlock(&zi->i_truncate_mutex);
+ ret = -EINVAL;
+ goto inode_unlock;
+ }
+ mutex_unlock(&zi->i_truncate_mutex);
+
+ ret = iomap_dio_rw(iocb, from, &zonefs_iomap_ops,
+ &zonefs_write_dio_ops, is_sync_kiocb(iocb));
+ if (zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
+ (ret > 0 || ret == -EIOCBQUEUED)) {
+ if (ret > 0)
+ count = ret;
+ mutex_lock(&zi->i_truncate_mutex);
+ zi->i_wpoffset += count;
+ mutex_unlock(&zi->i_truncate_mutex);
+ }
+
+inode_unlock:
+ inode_unlock(inode);
+
+ return ret;
+}
+
+static ssize_t zonefs_file_buffered_write(struct kiocb *iocb,
+ struct iov_iter *from)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ ssize_t ret;
+
+ /*
+ * Direct IO writes are mandatory for sequential zones so that the
+ * write IO order is preserved.
+ */
+ if (zi->i_ztype != ZONEFS_ZTYPE_CNV)
+ return -EIO;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!inode_trylock(inode))
+ return -EAGAIN;
+ } else {
+ inode_lock(inode);
+ }
+
+ ret = generic_write_checks(iocb, from);
+ if (ret <= 0)
+ goto inode_unlock;
+
+ iov_iter_truncate(from, zi->i_max_size - iocb->ki_pos);
+
+ ret = iomap_file_buffered_write(iocb, from, &zonefs_iomap_ops);
+ if (ret > 0)
+ iocb->ki_pos += ret;
+ else if (ret == -EIO)
+ zonefs_io_error(inode, false);
+
+inode_unlock:
+ inode_unlock(inode);
+ if (ret > 0)
+ ret = generic_write_sync(iocb, ret);
+
+ return ret;
+}
+
+static ssize_t zonefs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+
+ if (unlikely(IS_IMMUTABLE(inode)))
+ return -EPERM;
+
+ if (sb_rdonly(inode->i_sb))
+ return -EROFS;
+
+ /* Write operations beyond the zone size are not allowed */
+ if (iocb->ki_pos >= ZONEFS_I(inode)->i_max_size)
+ return -EFBIG;
+
+ if (iocb->ki_flags & IOCB_DIRECT)
+ return zonefs_file_dio_write(iocb, from);
+
+ return zonefs_file_buffered_write(iocb, from);
+}
+
+static int zonefs_file_read_dio_end_io(struct kiocb *iocb, ssize_t size,
+ int error, unsigned int flags)
+{
+ if (error) {
+ zonefs_io_error(file_inode(iocb->ki_filp), false);
+ return error;
+ }
+
+ return 0;
+}
+
+static const struct iomap_dio_ops zonefs_read_dio_ops = {
+ .end_io = zonefs_file_read_dio_end_io,
+};
+
+static ssize_t zonefs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ loff_t isize;
+ ssize_t ret;
+
+ /* Offline zones cannot be read */
+ if (unlikely(IS_IMMUTABLE(inode) && !(inode->i_mode & 0777)))
+ return -EPERM;
+
+ if (iocb->ki_pos >= zi->i_max_size)
+ return 0;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!inode_trylock_shared(inode))
+ return -EAGAIN;
+ } else {
+ inode_lock_shared(inode);
+ }
+
+ /* Limit read operations to written data */
+ mutex_lock(&zi->i_truncate_mutex);
+ isize = i_size_read(inode);
+ if (iocb->ki_pos >= isize) {
+ mutex_unlock(&zi->i_truncate_mutex);
+ ret = 0;
+ goto inode_unlock;
+ }
+ iov_iter_truncate(to, isize - iocb->ki_pos);
+ mutex_unlock(&zi->i_truncate_mutex);
+
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ size_t count = iov_iter_count(to);
+
+ if ((iocb->ki_pos | count) & sbi->s_blocksize_mask) {
+ ret = -EINVAL;
+ goto inode_unlock;
+ }
+ file_accessed(iocb->ki_filp);
+ ret = iomap_dio_rw(iocb, to, &zonefs_iomap_ops,
+ &zonefs_read_dio_ops, is_sync_kiocb(iocb));
+ } else {
+ ret = generic_file_read_iter(iocb, to);
+ if (ret == -EIO)
+ zonefs_io_error(inode, false);
+ }
+
+inode_unlock:
+ inode_unlock_shared(inode);
+
+ return ret;
+}
+
+static const struct file_operations zonefs_file_operations = {
+ .open = generic_file_open,
+ .fsync = zonefs_file_fsync,
+ .mmap = zonefs_file_mmap,
+ .llseek = zonefs_file_llseek,
+ .read_iter = zonefs_file_read_iter,
+ .write_iter = zonefs_file_write_iter,
+ .splice_read = generic_file_splice_read,
+ .splice_write = iter_file_splice_write,
+ .iopoll = iomap_dio_iopoll,
+};
+
+static struct kmem_cache *zonefs_inode_cachep;
+
+static struct inode *zonefs_alloc_inode(struct super_block *sb)
+{
+ struct zonefs_inode_info *zi;
+
+ zi = kmem_cache_alloc(zonefs_inode_cachep, GFP_KERNEL);
+ if (!zi)
+ return NULL;
+
+ inode_init_once(&zi->i_vnode);
+ mutex_init(&zi->i_truncate_mutex);
+ init_rwsem(&zi->i_mmap_sem);
+
+ return &zi->i_vnode;
+}
+
+static void zonefs_free_inode(struct inode *inode)
+{
+ kmem_cache_free(zonefs_inode_cachep, ZONEFS_I(inode));
+}
+
+/*
+ * File system stat.
+ */
+static int zonefs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ struct super_block *sb = dentry->d_sb;
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ enum zonefs_ztype t;
+ u64 fsid;
+
+ buf->f_type = ZONEFS_MAGIC;
+ buf->f_bsize = sb->s_blocksize;
+ buf->f_namelen = ZONEFS_NAME_MAX;
+
+ spin_lock(&sbi->s_lock);
+
+ buf->f_blocks = sbi->s_blocks;
+ if (WARN_ON(sbi->s_used_blocks > sbi->s_blocks))
+ buf->f_bfree = 0;
+ else
+ buf->f_bfree = buf->f_blocks - sbi->s_used_blocks;
+ buf->f_bavail = buf->f_bfree;
+
+ for (t = 0; t < ZONEFS_ZTYPE_MAX; t++) {
+ if (sbi->s_nr_files[t])
+ buf->f_files += sbi->s_nr_files[t] + 1;
+ }
+ buf->f_ffree = 0;
+
+ spin_unlock(&sbi->s_lock);
+
+ fsid = le64_to_cpup((void *)sbi->s_uuid.b) ^
+ le64_to_cpup((void *)sbi->s_uuid.b + sizeof(u64));
+ buf->f_fsid.val[0] = (u32)fsid;
+ buf->f_fsid.val[1] = (u32)(fsid >> 32);
+
+ return 0;
+}
+
+enum {
+ Opt_errors_repair, Opt_errors_ro, Opt_errors_zro, Opt_errors_zol,
+ Opt_err,
+};
+
+static const match_table_t tokens = {
+ { Opt_errors_ro, "errors=repair"},
+ { Opt_errors_ro, "errors=remount-ro"},
+ { Opt_errors_zro, "errors=zone-ro"},
+ { Opt_errors_zol, "errors=zone-offline"},
+ { Opt_err, NULL}
+};
+
+static int zonefs_parse_options(struct super_block *sb, char *options)
+{
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ substring_t args[MAX_OPT_ARGS];
+ char *p;
+
+ if (!options)
+ return 0;
+
+ while ((p = strsep(&options, ",")) != NULL) {
+ int token;
+
+ if (!*p)
+ continue;
+
+ token = match_token(p, tokens, args);
+ switch (token) {
+ case Opt_errors_repair:
+ sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
+ sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_REPAIR;
+ break;
+ case Opt_errors_ro:
+ sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
+ sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_RO;
+ break;
+ case Opt_errors_zro:
+ sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
+ sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_ZRO;
+ break;
+ case Opt_errors_zol:
+ sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
+ sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_ZOL;
+ break;
+ default:
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+static int zonefs_show_options(struct seq_file *seq, struct dentry *root)
+{
+ struct zonefs_sb_info *sbi = ZONEFS_SB(root->d_sb);
+
+ if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_REPAIR)
+ seq_puts(seq, ",errors=repair");
+ if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_RO)
+ seq_puts(seq, ",errors=remount-ro");
+ if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZRO)
+ seq_puts(seq, ",errors=zone-ro");
+ if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZOL)
+ seq_puts(seq, ",errors=zone-offline");
+
+ return 0;
+}
+
+static int zonefs_remount(struct super_block *sb, int *flags, char *data)
+{
+ sync_filesystem(sb);
+
+ return zonefs_parse_options(sb, data);
+}
+
+static const struct super_operations zonefs_sops = {
+ .alloc_inode = zonefs_alloc_inode,
+ .free_inode = zonefs_free_inode,
+ .statfs = zonefs_statfs,
+ .remount_fs = zonefs_remount,
+ .show_options = zonefs_show_options,
+};
+
+static const struct inode_operations zonefs_dir_inode_operations = {
+ .lookup = simple_lookup,
+ .setattr = zonefs_inode_setattr,
+};
+
+static void zonefs_init_dir_inode(struct inode *parent, struct inode *inode,
+ enum zonefs_ztype type)
+{
+ struct super_block *sb = parent->i_sb;
+
+ inode->i_ino = blkdev_nr_zones(sb->s_bdev->bd_disk) + type + 1;
+ inode_init_owner(inode, parent, S_IFDIR | 0555);
+ inode->i_op = &zonefs_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+ set_nlink(inode, 2);
+ inc_nlink(parent);
+}
+
+static void zonefs_init_file_inode(struct inode *inode, struct blk_zone *zone,
+ enum zonefs_ztype type)
+{
+ struct super_block *sb = inode->i_sb;
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+
+ inode->i_ino = zone->start >> sbi->s_zone_sectors_shift;
+ inode->i_mode = S_IFREG | sbi->s_perm;
+
+ zi->i_ztype = type;
+ zi->i_zsector = zone->start;
+ zi->i_max_size = min_t(loff_t, MAX_LFS_FILESIZE,
+ zone->len << SECTOR_SHIFT);
+ zi->i_wpoffset = zonefs_check_zone_condition(inode, zone);
+
+ inode->i_uid = sbi->s_uid;
+ inode->i_gid = sbi->s_gid;
+ inode->i_size = zi->i_wpoffset;
+ inode->i_blocks = zone->len;
+
+ inode->i_op = &zonefs_file_inode_operations;
+ inode->i_fop = &zonefs_file_operations;
+ inode->i_mapping->a_ops = &zonefs_file_aops;
+
+ sb->s_maxbytes = max(zi->i_max_size, sb->s_maxbytes);
+ sbi->s_blocks += zi->i_max_size >> sb->s_blocksize_bits;
+ sbi->s_used_blocks += zi->i_wpoffset >> sb->s_blocksize_bits;
+}
+
+static struct dentry *zonefs_create_inode(struct dentry *parent,
+ const char *name, struct blk_zone *zone,
+ enum zonefs_ztype type)
+{
+ struct inode *dir = d_inode(parent);
+ struct dentry *dentry;
+ struct inode *inode;
+
+ dentry = d_alloc_name(parent, name);
+ if (!dentry)
+ return NULL;
+
+ inode = new_inode(parent->d_sb);
+ if (!inode)
+ goto dput;
+
+ inode->i_ctime = inode->i_mtime = inode->i_atime = dir->i_ctime;
+ if (zone)
+ zonefs_init_file_inode(inode, zone, type);
+ else
+ zonefs_init_dir_inode(dir, inode, type);
+ d_add(dentry, inode);
+ dir->i_size++;
+
+ return dentry;
+
+dput:
+ dput(dentry);
+
+ return NULL;
+}
+
+static const char *zgroups_name[ZONEFS_ZTYPE_MAX] = { "cnv", "seq" };
+
+struct zonefs_zone_data {
+ struct super_block *sb;
+ unsigned int nr_zones[ZONEFS_ZTYPE_MAX];
+ struct blk_zone *zones;
+};
+
+/*
+ * Create a zone group and populate it with zone files.
+ */
+static int zonefs_create_zgroup(struct zonefs_zone_data *zd,
+ enum zonefs_ztype type)
+{
+ struct super_block *sb = zd->sb;
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ struct blk_zone *zone, *next, *end;
+ char name[ZONEFS_NAME_MAX];
+ struct dentry *dir;
+ unsigned int n = 0;
+
+ /* If the group is empty, there is nothing to do */
+ if (!zd->nr_zones[type])
+ return 0;
+
+ dir = zonefs_create_inode(sb->s_root, zgroups_name[type], NULL, type);
+ if (!dir)
+ return -ENOMEM;
+
+ /*
+ * The first zone contains the super block: skip it.
+ */
+ end = zd->zones + blkdev_nr_zones(sb->s_bdev->bd_disk);
+ for (zone = &zd->zones[1]; zone < end; zone = next) {
+
+ next = zone + 1;
+ if (zonefs_zone_type(zone) != type)
+ continue;
+
+ /*
+ * For conventional zones, contiguous zones can be aggregated
+ * together to form larger files. Note that this overwrites the
+ * length of the first zone of the set of contiguous zones
+ * aggregated together. If one offline or read-only zone is
+ * found, assume that all zones aggregated have the same
+ * condition.
+ */
+ if (type == ZONEFS_ZTYPE_CNV &&
+ (sbi->s_features & ZONEFS_F_AGGRCNV)) {
+ for (; next < end; next++) {
+ if (zonefs_zone_type(next) != type)
+ break;
+ zone->len += next->len;
+ if (next->cond == BLK_ZONE_COND_READONLY &&
+ zone->cond != BLK_ZONE_COND_OFFLINE)
+ zone->cond = BLK_ZONE_COND_READONLY;
+ else if (next->cond == BLK_ZONE_COND_OFFLINE)
+ zone->cond = BLK_ZONE_COND_OFFLINE;
+ }
+ }
+
+ /*
+ * Use the file number within its group as file name.
+ */
+ snprintf(name, ZONEFS_NAME_MAX - 1, "%u", n);
+ if (!zonefs_create_inode(dir, name, zone, type))
+ return -ENOMEM;
+
+ n++;
+ }
+
+ zonefs_info(sb, "Zone group \"%s\" has %u file%s\n",
+ zgroups_name[type], n, n > 1 ? "s" : "");
+
+ sbi->s_nr_files[type] = n;
+
+ return 0;
+}
+
+static int zonefs_get_zone_info_cb(struct blk_zone *zone, unsigned int idx,
+ void *data)
+{
+ struct zonefs_zone_data *zd = data;
+
+ /*
+ * Count the number of usable zones: the first zone at index 0 contains
+ * the super block and is ignored.
+ */
+ switch (zone->type) {
+ case BLK_ZONE_TYPE_CONVENTIONAL:
+ zone->wp = zone->start + zone->len;
+ if (idx)
+ zd->nr_zones[ZONEFS_ZTYPE_CNV]++;
+ break;
+ case BLK_ZONE_TYPE_SEQWRITE_REQ:
+ case BLK_ZONE_TYPE_SEQWRITE_PREF:
+ if (idx)
+ zd->nr_zones[ZONEFS_ZTYPE_SEQ]++;
+ break;
+ default:
+ zonefs_err(zd->sb, "Unsupported zone type 0x%x\n",
+ zone->type);
+ return -EIO;
+ }
+
+ memcpy(&zd->zones[idx], zone, sizeof(struct blk_zone));
+
+ return 0;
+}
+
+static int zonefs_get_zone_info(struct zonefs_zone_data *zd)
+{
+ struct block_device *bdev = zd->sb->s_bdev;
+ int ret;
+
+ zd->zones = kvcalloc(blkdev_nr_zones(bdev->bd_disk),
+ sizeof(struct blk_zone), GFP_KERNEL);
+ if (!zd->zones)
+ return -ENOMEM;
+
+ /* Get zones information from the device */
+ ret = blkdev_report_zones(bdev, 0, BLK_ALL_ZONES,
+ zonefs_get_zone_info_cb, zd);
+ if (ret < 0) {
+ zonefs_err(zd->sb, "Zone report failed %d\n", ret);
+ return ret;
+ }
+
+ if (ret != blkdev_nr_zones(bdev->bd_disk)) {
+ zonefs_err(zd->sb, "Invalid zone report (%d/%u zones)\n",
+ ret, blkdev_nr_zones(bdev->bd_disk));
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static inline void zonefs_cleanup_zone_info(struct zonefs_zone_data *zd)
+{
+ kvfree(zd->zones);
+}
+
+/*
+ * Read super block information from the device.
+ */
+static int zonefs_read_super(struct super_block *sb)
+{
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+ struct zonefs_super *super;
+ u32 crc, stored_crc;
+ struct page *page;
+ struct bio_vec bio_vec;
+ struct bio bio;
+ int ret;
+
+ page = alloc_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+
+ bio_init(&bio, &bio_vec, 1);
+ bio.bi_iter.bi_sector = 0;
+ bio.bi_opf = REQ_OP_READ;
+ bio_set_dev(&bio, sb->s_bdev);
+ bio_add_page(&bio, page, PAGE_SIZE, 0);
+
+ ret = submit_bio_wait(&bio);
+ if (ret)
+ goto free_page;
+
+ super = kmap(page);
+
+ ret = -EINVAL;
+ if (le32_to_cpu(super->s_magic) != ZONEFS_MAGIC)
+ goto unmap;
+
+ stored_crc = le32_to_cpu(super->s_crc);
+ super->s_crc = 0;
+ crc = crc32(~0U, (unsigned char *)super, sizeof(struct zonefs_super));
+ if (crc != stored_crc) {
+ zonefs_err(sb, "Invalid checksum (Expected 0x%08x, got 0x%08x)",
+ crc, stored_crc);
+ goto unmap;
+ }
+
+ sbi->s_features = le64_to_cpu(super->s_features);
+ if (sbi->s_features & ~ZONEFS_F_DEFINED_FEATURES) {
+ zonefs_err(sb, "Unknown features set 0x%llx\n",
+ sbi->s_features);
+ goto unmap;
+ }
+
+ if (sbi->s_features & ZONEFS_F_UID) {
+ sbi->s_uid = make_kuid(current_user_ns(),
+ le32_to_cpu(super->s_uid));
+ if (!uid_valid(sbi->s_uid)) {
+ zonefs_err(sb, "Invalid UID feature\n");
+ goto unmap;
+ }
+ }
+
+ if (sbi->s_features & ZONEFS_F_GID) {
+ sbi->s_gid = make_kgid(current_user_ns(),
+ le32_to_cpu(super->s_gid));
+ if (!gid_valid(sbi->s_gid)) {
+ zonefs_err(sb, "Invalid GID feature\n");
+ goto unmap;
+ }
+ }
+
+ if (sbi->s_features & ZONEFS_F_PERM)
+ sbi->s_perm = le32_to_cpu(super->s_perm);
+
+ if (memchr_inv(super->s_reserved, 0, sizeof(super->s_reserved))) {
+ zonefs_err(sb, "Reserved area is being used\n");
+ goto unmap;
+ }
+
+ uuid_copy(&sbi->s_uuid, (uuid_t *)super->s_uuid);
+ ret = 0;
+
+unmap:
+ kunmap(page);
+free_page:
+ __free_page(page);
+
+ return ret;
+}
+
+/*
+ * Check that the device is zoned. If it is, get the list of zones and create
+ * sub-directories and files according to the device zone configuration and
+ * format options.
+ */
+static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
+{
+ struct zonefs_zone_data zd;
+ struct zonefs_sb_info *sbi;
+ struct inode *inode;
+ enum zonefs_ztype t;
+ int ret;
+
+ if (!bdev_is_zoned(sb->s_bdev)) {
+ zonefs_err(sb, "Not a zoned block device\n");
+ return -EINVAL;
+ }
+
+ /*
+ * Initialize super block information: the maximum file size is updated
+ * when the zone files are created so that the format option
+ * ZONEFS_F_AGGRCNV which increases the maximum file size of a file
+ * beyond the zone size is taken into account.
+ */
+ sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
+ if (!sbi)
+ return -ENOMEM;
+
+ spin_lock_init(&sbi->s_lock);
+ sb->s_fs_info = sbi;
+ sb->s_magic = ZONEFS_MAGIC;
+ sb->s_maxbytes = 0;
+ sb->s_op = &zonefs_sops;
+ sb->s_time_gran = 1;
+
+ /*
+ * The block size is set to the device physical sector size to ensure
+ * that write operations on 512e devices (512B logical block and 4KB
+ * physical block) are always aligned to the device physical blocks,
+ * as mandated by the ZBC/ZAC specifications.
+ */
+ sb_set_blocksize(sb, bdev_physical_block_size(sb->s_bdev));
+ sbi->s_blocksize_mask = sb->s_blocksize - 1;
+ sbi->s_zone_sectors_shift = ilog2(bdev_zone_sectors(sb->s_bdev));
+ sbi->s_uid = GLOBAL_ROOT_UID;
+ sbi->s_gid = GLOBAL_ROOT_GID;
+ sbi->s_perm = 0640;
+ sbi->s_mount_opts = ZONEFS_MNTOPT_ERRORS_RO;
+
+ ret = zonefs_read_super(sb);
+ if (ret)
+ return ret;
+
+ ret = zonefs_parse_options(sb, data);
+ if (ret)
+ return ret;
+
+ memset(&zd, 0, sizeof(struct zonefs_zone_data));
+ zd.sb = sb;
+ ret = zonefs_get_zone_info(&zd);
+ if (ret)
+ goto cleanup;
+
+ zonefs_info(sb, "Mounting %u zones",
+ blkdev_nr_zones(sb->s_bdev->bd_disk));
+
+ /* Create root directory inode */
+ ret = -ENOMEM;
+ inode = new_inode(sb);
+ if (!inode)
+ goto cleanup;
+
+ inode->i_ino = blkdev_nr_zones(sb->s_bdev->bd_disk);
+ inode->i_mode = S_IFDIR | 0555;
+ inode->i_ctime = inode->i_mtime = inode->i_atime = current_time(inode);
+ inode->i_op = &zonefs_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+ set_nlink(inode, 2);
+
+ sb->s_root = d_make_root(inode);
+ if (!sb->s_root)
+ goto cleanup;
+
+ /* Create and populate files in zone groups directories */
+ for (t = 0; t < ZONEFS_ZTYPE_MAX; t++) {
+ ret = zonefs_create_zgroup(&zd, t);
+ if (ret)
+ break;
+ }
+
+cleanup:
+ zonefs_cleanup_zone_info(&zd);
+
+ return ret;
+}
+
+static struct dentry *zonefs_mount(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data)
+{
+ return mount_bdev(fs_type, flags, dev_name, data, zonefs_fill_super);
+}
+
+static void zonefs_kill_super(struct super_block *sb)
+{
+ struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+
+ if (sb->s_root)
+ d_genocide(sb->s_root);
+ kill_block_super(sb);
+ kfree(sbi);
+}
+
+/*
+ * File system definition and registration.
+ */
+static struct file_system_type zonefs_type = {
+ .owner = THIS_MODULE,
+ .name = "zonefs",
+ .mount = zonefs_mount,
+ .kill_sb = zonefs_kill_super,
+ .fs_flags = FS_REQUIRES_DEV,
+};
+
+static int __init zonefs_init_inodecache(void)
+{
+ zonefs_inode_cachep = kmem_cache_create("zonefs_inode_cache",
+ sizeof(struct zonefs_inode_info), 0,
+ (SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | SLAB_ACCOUNT),
+ NULL);
+ if (zonefs_inode_cachep == NULL)
+ return -ENOMEM;
+ return 0;
+}
+
+static void zonefs_destroy_inodecache(void)
+{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy the inode cache.
+ */
+ rcu_barrier();
+ kmem_cache_destroy(zonefs_inode_cachep);
+}
+
+static int __init zonefs_init(void)
+{
+ int ret;
+
+ BUILD_BUG_ON(sizeof(struct zonefs_super) != ZONEFS_SUPER_SIZE);
+
+ ret = zonefs_init_inodecache();
+ if (ret)
+ return ret;
+
+ ret = register_filesystem(&zonefs_type);
+ if (ret) {
+ zonefs_destroy_inodecache();
+ return ret;
+ }
+
+ return 0;
+}
+
+static void __exit zonefs_exit(void)
+{
+ zonefs_destroy_inodecache();
+ unregister_filesystem(&zonefs_type);
+}
+
+MODULE_AUTHOR("Damien Le Moal");
+MODULE_DESCRIPTION("Zone file system for zoned block devices");
+MODULE_LICENSE("GPL");
+module_init(zonefs_init);
+module_exit(zonefs_exit);
diff --git a/fs/zonefs/zonefs.h b/fs/zonefs/zonefs.h
new file mode 100644
index 000000000000..652303620b1e
--- /dev/null
+++ b/fs/zonefs/zonefs.h
@@ -0,0 +1,192 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Simple zone file system for zoned block devices.
+ *
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ */
+#ifndef __ZONEFS_H__
+#define __ZONEFS_H__
+
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/uuid.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+
+/*
+ * Maximum length of file names: this only needs to be large enough to fit
+ * the zone group directory names and a decimal zone number for file names.
+ * 16 characters is plenty.
+ */
+#define ZONEFS_NAME_MAX 16
+
+/*
+ * Zone types: ZONEFS_ZTYPE_SEQ is used for all sequential zone types
+ * defined in linux/blkzoned.h, that is, BLK_ZONE_TYPE_SEQWRITE_REQ and
+ * BLK_ZONE_TYPE_SEQWRITE_PREF.
+ */
+enum zonefs_ztype {
+ ZONEFS_ZTYPE_CNV,
+ ZONEFS_ZTYPE_SEQ,
+ ZONEFS_ZTYPE_MAX,
+};
+
+static inline enum zonefs_ztype zonefs_zone_type(struct blk_zone *zone)
+{
+ if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
+ return ZONEFS_ZTYPE_CNV;
+ return ZONEFS_ZTYPE_SEQ;
+}
+
+/*
+ * In-memory inode data.
+ */
+struct zonefs_inode_info {
+ struct inode i_vnode;
+
+ /* File zone type */
+ enum zonefs_ztype i_ztype;
+
+ /* File zone start sector (512B unit) */
+ sector_t i_zsector;
+
+ /* File zone write pointer position (sequential zones only) */
+ loff_t i_wpoffset;
+
+ /* File maximum size */
+ loff_t i_max_size;
+
+ /*
+ * To serialise fully against both syscall and mmap based IO and
+ * sequential file truncation, two locks are used. For serializing
+ * zonefs_seq_file_truncate() against zonefs_iomap_begin(), that is,
+ * file truncate operations against block mapping, i_truncate_mutex is
+ * used. i_truncate_mutex also protects against concurrent accesses
+ * and changes to the inode private data, and in particular changes to
+ * a sequential file size on completion of direct IO writes.
+ * Serialization of mmap read IOs with truncate and syscall IO
+ * operations is done with i_mmap_sem in addition to i_truncate_mutex.
+ * Only zonefs_seq_file_truncate() takes both lock (i_mmap_sem first,
+ * i_truncate_mutex second).
+ */
+ struct mutex i_truncate_mutex;
+ struct rw_semaphore i_mmap_sem;
+};
+
+static inline struct zonefs_inode_info *ZONEFS_I(struct inode *inode)
+{
+ return container_of(inode, struct zonefs_inode_info, i_vnode);
+}
+
+/*
+ * On-disk super block (block 0).
+ */
+#define ZONEFS_LABEL_LEN 64
+#define ZONEFS_UUID_SIZE 16
+#define ZONEFS_SUPER_SIZE 4096
+
+struct zonefs_super {
+
+ /* Magic number */
+ __le32 s_magic;
+
+ /* Checksum */
+ __le32 s_crc;
+
+ /* Volume label */
+ char s_label[ZONEFS_LABEL_LEN];
+
+ /* 128-bit uuid */
+ __u8 s_uuid[ZONEFS_UUID_SIZE];
+
+ /* Features */
+ __le64 s_features;
+
+ /* UID/GID to use for files */
+ __le32 s_uid;
+ __le32 s_gid;
+
+ /* File permissions */
+ __le32 s_perm;
+
+ /* Padding to ZONEFS_SUPER_SIZE bytes */
+ __u8 s_reserved[3988];
+
+} __packed;
+
+/*
+ * Feature flags: specified in the s_features field of the on-disk super
+ * block struct zonefs_super and in-memory in the s_feartures field of
+ * struct zonefs_sb_info.
+ */
+enum zonefs_features {
+ /*
+ * Aggregate contiguous conventional zones into a single file.
+ */
+ ZONEFS_F_AGGRCNV = 1ULL << 0,
+ /*
+ * Use super block specified UID for files instead of default 0.
+ */
+ ZONEFS_F_UID = 1ULL << 1,
+ /*
+ * Use super block specified GID for files instead of default 0.
+ */
+ ZONEFS_F_GID = 1ULL << 2,
+ /*
+ * Use super block specified file permissions instead of default 640.
+ */
+ ZONEFS_F_PERM = 1ULL << 3,
+};
+
+#define ZONEFS_F_DEFINED_FEATURES \
+ (ZONEFS_F_AGGRCNV | ZONEFS_F_UID | ZONEFS_F_GID | ZONEFS_F_PERM)
+
+/*
+ * Mount options for zone write pointer error handling.
+ */
+#define ZONEFS_MNTOPT_ERRORS_REPAIR (1 << 0) /* Remount read-only */
+#define ZONEFS_MNTOPT_ERRORS_RO (1 << 1) /* Make zone file readonly */
+#define ZONEFS_MNTOPT_ERRORS_ZRO (1 << 2) /* Make zone file offline */
+#define ZONEFS_MNTOPT_ERRORS_ZOL (1 << 3) /* Make zone file offline */
+#define ZONEFS_MNTOPT_ERRORS_MASK \
+ (ZONEFS_MNTOPT_ERRORS_REPAIR | ZONEFS_MNTOPT_ERRORS_RO | \
+ ZONEFS_MNTOPT_ERRORS_ZRO | ZONEFS_MNTOPT_ERRORS_ZOL)
+
+/*
+ * In-memory Super block information.
+ */
+struct zonefs_sb_info {
+
+ unsigned long s_mount_opts;
+
+ spinlock_t s_lock;
+
+ unsigned long long s_features;
+ kuid_t s_uid;
+ kgid_t s_gid;
+ umode_t s_perm;
+ uuid_t s_uuid;
+ loff_t s_blocksize_mask;
+ unsigned int s_zone_sectors_shift;
+
+ unsigned int s_nr_files[ZONEFS_ZTYPE_MAX];
+
+ loff_t s_blocks;
+ loff_t s_used_blocks;
+};
+
+static inline struct zonefs_sb_info *ZONEFS_SB(struct super_block *sb)
+{
+ return sb->s_fs_info;
+}
+
+#define zonefs_info(sb, format, args...) \
+ pr_info("zonefs (%s): " format, sb->s_id, ## args)
+#define zonefs_err(sb, format, args...) \
+ pr_err("zonefs (%s) ERROR: " format, sb->s_id, ## args)
+#define zonefs_warn(sb, format, args...) \
+ pr_warn("zonefs (%s) WARNING: " format, sb->s_id, ## args)
+#define zonefs_panic(sb, format, args...) \
+ panic("zonefs (%s) PANIC: " format, sb->s_id, ## args)
+
+#endif
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 3ac436376d79..d78064007b17 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -87,6 +87,7 @@
#define NSFS_MAGIC 0x6e736673
#define BPF_FS_MAGIC 0xcafe4a11
#define AAFS_MAGIC 0x5a3c69f0
+#define ZONEFS_MAGIC 0x5a4f4653
/* Since UDF 2.01 is ISO 13346 based... */
#define UDF_SUPER_MAGIC 0x15013346
--
2.24.1
Add the new file Documentation/filesystems/zonefs.txt to document
zonefs principles and user-space tool usage.
Signed-off-by: Damien Le Moal <[email protected]>
---
Documentation/filesystems/zonefs.txt | 301 +++++++++++++++++++++++++++
MAINTAINERS | 1 +
2 files changed, 302 insertions(+)
create mode 100644 Documentation/filesystems/zonefs.txt
diff --git a/Documentation/filesystems/zonefs.txt b/Documentation/filesystems/zonefs.txt
new file mode 100644
index 000000000000..3c14de9b70c3
--- /dev/null
+++ b/Documentation/filesystems/zonefs.txt
@@ -0,0 +1,301 @@
+ZoneFS - Zone filesystem for Zoned block devices
+
+Introduction
+============
+
+zonefs is a very simple file system exposing each zone of a zoned block device
+as a file. Unlike a regular POSIX-compliant file system with native zoned block
+device support (e.g. f2fs), zonefs does not hide the sequential write
+constraint of zoned block devices to the user. Files representing sequential
+write zones of the device must be written sequentially starting from the end
+of the file (append only writes).
+
+As such, zonefs is in essence closer to a raw block device access interface
+than to a full-featured POSIX file system. The goal of zonefs is to simplify
+the implementation of zoned block device support in applications by replacing
+raw block device file accesses with a richer file API, avoiding relying on
+direct block device file ioctls which may be more obscure to developers. One
+example of this approach is the implementation of LSM (log-structured merge)
+tree structures (such as used in RocksDB and LevelDB) on zoned block devices
+by allowing SSTables to be stored in a zone file similarly to a regular file
+system rather than as a range of sectors of the entire disk. The introduction
+of the higher level construct "one file is one zone" can help reducing the
+amount of changes needed in the application as well as introducing support for
+different application programming languages.
+
+Zoned block devices
+-------------------
+
+Zoned storage devices belong to a class of storage devices with an address
+space that is divided into zones. A zone is a group of consecutive LBAs and all
+zones are contiguous (there are no LBA gaps). Zones may have different types.
+* Conventional zones: there are no access constraints to LBAs belonging to
+ conventional zones. Any read or write access can be executed, similarly to a
+ regular block device.
+* Sequential zones: these zones accept random reads but must be written
+ sequentially. Each sequential zone has a write pointer maintained by the
+ device that keeps track of the mandatory start LBA position of the next write
+ to the device. As a result of this write constraint, LBAs in a sequential zone
+ cannot be overwritten. Sequential zones must first be erased using a special
+ command (zone reset) before rewriting.
+
+Zoned storage devices can be implemented using various recording and media
+technologies. The most common form of zoned storage today uses the SCSI Zoned
+Block Commands (ZBC) and Zoned ATA Commands (ZAC) interfaces on Shingled
+Magnetic Recording (SMR) HDDs.
+
+Solid State Disks (SSD) storage devices can also implement a zoned interface
+to, for instance, reduce internal write amplification due to garbage collection.
+The NVMe Zoned NameSpace (ZNS) is a technical proposal of the NVMe standard
+committee aiming at adding a zoned storage interface to the NVMe protocol.
+
+Zonefs Overview
+===============
+
+Zonefs exposes the zones of a zoned block device as files. The files
+representing zones are grouped by zone type, which are themselves represented
+by sub-directories. This file structure is built entirely using zone information
+provided by the device and so does not require any complex on-disk metadata
+structure.
+
+zonefs on-disk metadata
+-----------------------
+
+zonefs on-disk metadata is reduced to an immutable super block which
+persistently stores a magic number and optional feature flags and values. On
+mount, zonefs uses blkdev_report_zones() to obtain the device zone configuration
+and populates the mount point with a static file tree solely based on this
+information. File sizes come from the device zone type and write pointer
+position managed by the device itself.
+
+The super block is always written on disk at sector 0. The first zone of the
+device storing the super block is never exposed as a zone file by zonefs. If
+the zone containing the super block is a sequential zone, the mkzonefs format
+tool always "finishes" the zone, that is, it transitions the zone to a full
+state to make it read-only, preventing any data write.
+
+Zone type sub-directories
+-------------------------
+
+Files representing zones of the same type are grouped together under the same
+sub-directory automatically created on mount.
+
+For conventional zones, the sub-directory "cnv" is used. This directory is
+however created if and only if the device has usable conventional zones. If
+the device only has a single conventional zone at sector 0, the zone will not
+be exposed as a file as it will be used to store the zonefs super block. For
+such devices, the "cnv" sub-directory will not be created.
+
+For sequential write zones, the sub-directory "seq" is used.
+
+These two directories are the only directories that exist in zonefs. Users
+cannot create other directories and cannot rename nor delete the "cnv" and
+"seq" sub-directories.
+
+The size of the directories indicated by the st_size field of struct stat,
+obtained with the stat() or fstat() system calls, indicates the number of files
+existing under the directory.
+
+Zone files
+----------
+
+Zone files are named using the number of the zone they represent within the set
+of zones of a particular type. That is, both the "cnv" and "seq" directories
+contain files named "0", "1", "2", ... The file numbers also represent
+increasing zone start sector on the device.
+
+All read and write operations to zone files are not allowed beyond the file
+maximum size, that is, beyond the zone size. Any access exceeding the zone
+size is failed with the -EFBIG error.
+
+Creating, deleting, renaming or modifying any attribute of files and
+sub-directories is not allowed.
+
+The number of blocks of a file as reported by stat() and fstat() indicates the
+size of the file zone, or in other words, the maximum file size.
+
+Conventional zone files
+-----------------------
+
+The size of conventional zone files is fixed to the size of the zone they
+represent. Conventional zone files cannot be truncated.
+
+These files can be randomly read and written using any type of I/O operation:
+buffered I/Os, direct I/Os, memory mapped I/Os (mmap), etc. There are no I/O
+constraint for these files beyond the file size limit mentioned above.
+
+Sequential zone files
+---------------------
+
+The size of sequential zone files grouped in the "seq" sub-directory represents
+the file's zone write pointer position relative to the zone start sector.
+
+Sequential zone files can only be written sequentially, starting from the file
+end, that is, write operations can only be append writes. Zonefs makes no
+attempt at accepting random writes and will fail any write request that has a
+start offset not corresponding to the end of the file, or to the end of the last
+write issued and still in-flight (for asynchrnous I/O operations).
+
+Since dirty page writeback by the page cache does not guarantee a sequential
+write pattern, zonefs prevents buffered writes and writeable shared mappings
+on sequential files. Only direct I/O writes are accepted for these files.
+zonefs relies on the sequential delivery of write I/O requests to the device
+implemented by the block layer elevator. An elevator implementing the sequential
+write feature for zoned block device (ELEVATOR_F_ZBD_SEQ_WRITE elevator feature)
+must be used. This type of elevator (e.g. mq-deadline) is the set by default
+for zoned block devices on device initialization.
+
+There are no restrictions on the type of I/O used for read operations in
+sequential zone files. Buffered I/Os, direct I/Os and shared read mappings are
+all accepted.
+
+Truncating sequential zone files is allowed only down to 0, in which case, the
+zone is reset to rewind the file zone write pointer position to the start of
+the zone, or up to the zone size, in which case the file's zone is transitioned
+to the FULL state (finish zone operation).
+
+zonefs format options
+---------------------
+
+Several optional features of zonefs can be enabled at format time.
+* Conventional zone aggregation: ranges of contiguous conventional zones can be
+ aggregated into a single larger file instead of the default one file per zone.
+* File ownership: The owner UID and GID of zone files is by default 0 (root)
+ but can be changed to any valid UID/GID.
+* File access permissions: the default 640 access permissions can be changed.
+
+zonefs mount options
+--------------------
+
+zonefs defines several mount options allowing the user to define what to do in
+case of I/O errors and when inconsistencies between a file size and its zone
+write pointer position are discovered.
+
+These options are as follows.
+* errors=repair
+ Always adjust the size of a file to reflect the current position of the file
+ zone write pointer. This option will have an effect only on sequential zone
+ files.
+* errors=remount-ro
+ When a corrupted sequential zone is discovered, adjust the file size to the
+ zone write pointer position relative to the zone start sector and remount the
+ file system read-only, preventing any further write to all files.
+* errors=zone-ro
+ When a corrupted sequential zone is discovered, adjust the file size to the
+ zone write pointer offset within the zone and set the zone file as read-only,
+ preventing any further modification to the file.
+* errors=zone-offline
+ When a corrupted sequential zone is discovered, treat the zone as being
+ offline. This implies that the file size is changed to 0 and all read/write
+ accesses to the file disabled.
+
+A corrupted zone here is defined as a zone with a write pointer position
+relative to the zone start sector that is lower than the file size. This
+indicates that either an external action triggered a zone reset (eventually
+followed by write operations to the zone) or that the drive is defective.
+
+The other possible type of inconsistency between a sequential file size and
+its zone write pointer position can be caused by partial write failures (e.g.
+one BIO of a multi-bio large direct write fails). These inconsistencies are
+automatically repaired by zonefs without further action taken, regardless of
+the error processing option specified at mount time.
+
+Finally, defective drives may change the condition of any zone to offline
+(zone dead) or read-only. Such changes, when discovered with the IO errors they
+can cause, are handled automatically regardless of the options specified at
+mount time. For offline zones, the action taken is similar to the action defined
+by the errors=zone-offline mount option. FOr read-only zones, the action used is
+as defined by the errors=zone-ro mount option.
+
+Zonefs User Space Tools
+=======================
+
+The mkzonefs tool is used to format zoned block devices for use with zonefs.
+This tool is available on Github at:
+
+https://github.com/damien-lemoal/zonefs-tools
+
+zonefs-tools also includes a test suite which can be run against any zoned
+block device, including null_blk block device created with zoned mode.
+
+Examples
+--------
+
+The following formats a 15TB host-managed SMR HDD with 256 MB zones
+with the conventional zones aggregation feature enabled.
+
+# mkzonefs -o aggr_cnv /dev/sdX
+# mount -t zonefs /dev/sdX /mnt
+# ls -l /mnt/
+total 0
+dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
+dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
+
+The size of the zone files sub-directories indicate the number of files
+existing for each type of zones. In this example, there is only one
+conventional zone file (all conventional zones are aggregated under a single
+file).
+
+# ls -l /mnt/cnv
+total 137101312
+-rw-r----- 1 root root 140391743488 Nov 25 13:23 0
+
+This aggregated conventional zone file can be used as a regular file.
+
+# mkfs.ext4 /mnt/cnv/0
+# mount -o loop /mnt/cnv/0 /data
+
+The "seq" sub-directory grouping files for sequential write zones has in this
+example 55356 zones.
+
+# ls -lv /mnt/seq
+total 14511243264
+-rw-r----- 1 root root 0 Nov 25 13:23 0
+-rw-r----- 1 root root 0 Nov 25 13:23 1
+-rw-r----- 1 root root 0 Nov 25 13:23 2
+...
+-rw-r----- 1 root root 0 Nov 25 13:23 55354
+-rw-r----- 1 root root 0 Nov 25 13:23 55355
+
+For sequential write zone files, the file size changes as data is appended at
+the end of the file, similarly to any regular file system.
+
+# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
+1+0 records in
+1+0 records out
+4096 bytes (4.1 kB, 4.0 KiB) copied, 0.00044121 s, 9.3 MB/s
+
+# ls -l /mnt/seq/0
+-rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
+
+The written file can be truncated to the zone size, preventing any further
+write operation.
+
+# truncate -s 268435456 /mnt/seq/0
+# ls -l /mnt/seq/0
+-rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
+
+Truncation to 0 size allows freeing the file zone storage space and restart
+append-writes to the file.
+
+# truncate -s 0 /mnt/seq/0
+# ls -l /mnt/seq/0
+-rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
+
+Since files are statically mapped to zones on the disk, the number of blocks of
+a file as reported by stat() and fstat() indicates the size of the file zone.
+
+# stat /mnt/seq/0
+ File: /mnt/seq/0
+ Size: 0 Blocks: 524288 IO Block: 4096 regular empty file
+Device: 870h/2160d Inode: 50431 Links: 1
+Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
+Access: 2019-11-25 13:23:57.048971997 +0900
+Modify: 2019-11-25 13:52:25.553805765 +0900
+Change: 2019-11-25 13:52:25.553805765 +0900
+ Birth: -
+
+The number of blocks of the file ("Blocks") in units of 512B blocks gives the
+maximum file size of 524288 * 512 B = 256 MB, corresponding to the device zone
+size in this example. Of note is that the "IO block" field always indicates the
+minimum I/O size for writes and corresponds to the device physical sector size.
diff --git a/MAINTAINERS b/MAINTAINERS
index 089fd879632a..e9dcf8952573 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18311,6 +18311,7 @@ L: [email protected]
T: git git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/zonefs.git
S: Maintained
F: fs/zonefs/
+F: Documentation/filesystems/zonefs.txt
ZPOOL COMPRESSED PAGE STORAGE API
M: Dan Streetman <[email protected]>
--
2.24.1
Looks good,
Reviewed-by: Johannes Thumshirn <[email protected]>
Looks good,
Reviewed-by: Johannes Thumshirn <[email protected]>
> zonefs IO management implementation uses the new iomap generic code.
Can it matter to begin such sentences with the capital letter “Z”?
> Changes from v9:
Are any more adjustments worth to be mentioned here?
Regards,
Markus
…
> +++ b/fs/zonefs/super.c
…
> +static const char *zgroups_name[ZONEFS_ZTYPE_MAX] = { "cnv", "seq" };
Can this array be treated as immutable?
How do you think about to use the following code variant?
+static const char const *zgroups_name[ZONEFS_ZTYPE_MAX] = { "cnv", "seq" };
Regards,
Markus
On Tue, 2020-02-04 at 10:46 +0100, Markus Elfring wrote:
> …
> > +++ b/fs/zonefs/super.c
> …
> > +static const char *zgroups_name[ZONEFS_ZTYPE_MAX] = { "cnv", "seq" };
>
> Can this array be treated as immutable?
> How do you think about to use the following code variant?
>
> +static const char const *zgroups_name[ZONEFS_ZTYPE_MAX] = { "cnv", "seq" };
That does not compile: duplicated const.
In any case, I am not sure what this would achieve since string
literals are constants by default and the pointer to the array is
declared as a constant too. This ends up completely with read-only text
section.
Declaring it as
static const char * const zgroups_name[] = { "cnv", "seq" };
is probably what you are suggesting, but since the string literals are
already constants by default, I do not think there is any difference.
>
> Regards,
> Markus
--
Damien Le Moal
Western Digital Research
> Declaring it as
>
> static const char * const zgroups_name[] = { "cnv", "seq" };
>
> is probably what you are suggesting,
Yes.
> but since the string literals are already constants by default,
> I do not think there is any difference.
I propose to define this array also as a completely immutable data structure.
Regards,
Markus