[PATCH v9 0/8] block atomic writes for xfs

John Garry
2024-10-16T10:03:59Z

This series expands atomic write support to filesystems, specifically
XFS.

Initially we will only support writing exactly 1x FS block atomically.

Since we can now have FS block size > PAGE_SIZE for XFS, we can write
atomically 4K+ blocks on x86.

No special per-inode flag is required for enabling writing 1x F block.
In future, to support writing more than one FS block atomically, a new FS
XFLAG flag may then introduced - like FS_XFLAG_BIG_ATOMICWRITES. This
would depend on a feature like forcealign.

So if we format the FS for 16K FS block size:
mkfs.xfs -b size=16384 /dev/sda

The statx reports atomic write unit min/max = FS block size:
$xfs_io -c statx filename
...
stat.stx_atomic_write_unit_min = 16384
stat.stx_atomic_write_unit_max = 16384
stat.stx_atomic_write_segments_max = 1
...

Baseline is 77bfe1b11ea0 (tag: xfs-6.12-fixes-3, xfs/xfs-6.12-fixesC,
xfs/for-next) xfs: fix a typo

Patches for this series can be found at:
https://github.com/johnpgarry/linux/tree/atomic-writes-v6.12-fs-v9

Changes since v8:
- Add bdev atomic write unit helpers (Christoph)
- Add comment on FS block size limit (Christoph)
- Stylistic improvements (Christoph)
- Add RB tags from Christoph (thanks!)

Changes since v7:
- Drop FS_XFLAG_ATOMICWRITES
- Reorder block/fs patches and add fixes tags (Christoph)
- Add RB tag from Christoph (Thanks!)
- Rebase

Changes since v6:
- Add iomap documentation update (Darrick)
- Drop reflink restriction (Darrick, Christoph)
- Catch XFS buffered IO fallback (Darrick)
- Check IOCB_DIRECT in generic_atomic_write_valid()
- Tweaks to coding style (Darrick)
- Add RB tags from Darrick and Christoph (thanks!)

John Garry (8):
block/fs: Pass an iocb to generic_atomic_write_valid()
fs/block: Check for IOCB_DIRECT in generic_atomic_write_valid()
block: Add bdev atomic write limits helpers
fs: Export generic_atomic_write_valid()
fs: iomap: Atomic write support
xfs: Support atomic write for statx
xfs: Validate atomic writes
xfs: Support setting FMODE_CAN_ATOMIC_WRITE

.../filesystems/iomap/operations.rst | 11 ++++++
block/fops.c | 22 ++++++-----
fs/iomap/direct-io.c | 38 +++++++++++++++++--
fs/iomap/trace.h | 3 +-
fs/read_write.c | 16 +++++---
fs/xfs/xfs_buf.c | 7 ++++
fs/xfs/xfs_buf.h | 4 ++
fs/xfs/xfs_file.c | 16 ++++++++
fs/xfs/xfs_inode.h | 15 ++++++++
fs/xfs/xfs_iops.c | 22 +++++++++++
include/linux/blkdev.h | 16 ++++++++
include/linux/fs.h | 2 +-
include/linux/iomap.h | 1 +
13 files changed, 151 insertions(+), 22 deletions(-)

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2.31.1