[v8,0/7] block atomic writes for xfs

Message

John Garry Oct. 15, 2024, 9:01 a.m. UTC

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 write 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-v8

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 (7):
  block/fs: Pass an iocb to generic_atomic_write_valid()
  fs/block: Check for IOCB_DIRECT in generic_atomic_write_valid()
  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                              |  3 ++
 fs/xfs/xfs_file.c                             | 10 +++++
 fs/xfs/xfs_inode.h                            | 15 ++++++++
 fs/xfs/xfs_iops.c                             | 25 ++++++++++++
 include/linux/fs.h                            |  2 +-
 include/linux/iomap.h                         |  1 +
 12 files changed, 131 insertions(+), 22 deletions(-)