[v6,0/7] block atomic writes for xfs

Message

John Garry Sept. 30, 2024, 12:54 p.m. UTC

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

Flag FS_XFLAG_ATOMICWRITES is added as an enabling flag for atomic writes.

XFS can be formatted for atomic writes as follows:
mkfs.xfs  -i atomicwrites=1 -b size=16384 /dev/sda

Support can be enabled through xfs_io command:
$xfs_io -c "chattr +W" filename
$xfs_io -c "lsattr -v" filename
[atomic-writes] filename
$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
...

Dependence on forcealign is gone for the moment. This means that we can
only write a single FS block atomically. Since we can now have FS block
size > PAGE_SIZE for XFS, we can write atomically write > 4K blocks on
x86.

Using the large FS block size has downsides, so we still want the
forcealign feature.

Baseline is v6.12-rc1

Basic xfsprogs support at:
https://github.com/johnpgarry/xfsprogs-dev/tree/atomic-writes-v6

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

Changes since v5:
- Drop forcealign dependency
- Can support atomically writing a single FS block
- XFS_DIFLAG2_ATOMICWRITES is inherited from parent directories
- Add RB tags from Darrick (thanks!)

Changes since v4:
- Drop iomap extent-based zeroing and use single bio to cover multiple
  extents
- Move forcealign to another series
- Various change in ioctl, sb, inode validation
- Add patch to tweak generic_atomic_write_valid() API

John Garry (7):
  block/fs: Pass an iocb to generic_atomic_write_valid()
  fs: Export generic_atomic_write_valid()
  fs: iomap: Atomic write support
  xfs: Support FS_XFLAG_ATOMICWRITES
  xfs: Support atomic write for statx
  xfs: Validate atomic writes
  xfs: Support setting FMODE_CAN_ATOMIC_WRITE

 block/fops.c                   |  8 +++----
 fs/iomap/direct-io.c           | 26 ++++++++++++++++++++---
 fs/iomap/trace.h               |  3 ++-
 fs/read_write.c                |  5 +++--
 fs/xfs/libxfs/xfs_format.h     | 11 ++++++++--
 fs/xfs/libxfs/xfs_inode_buf.c  | 38 ++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_inode_util.c |  6 ++++++
 fs/xfs/libxfs/xfs_sb.c         |  2 ++
 fs/xfs/xfs_buf.c               | 15 +++++++++++++-
 fs/xfs/xfs_buf.h               |  5 ++++-
 fs/xfs/xfs_buf_mem.c           |  2 +-
 fs/xfs/xfs_file.c              | 19 +++++++++++++++++
 fs/xfs/xfs_inode.h             | 22 ++++++++++++++++++++
 fs/xfs/xfs_ioctl.c             | 37 +++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iops.c              | 24 +++++++++++++++++++++
 fs/xfs/xfs_mount.h             |  2 ++
 fs/xfs/xfs_reflink.c           |  4 ++++
 fs/xfs/xfs_super.c             |  4 ++++
 include/linux/fs.h             |  2 +-
 include/linux/iomap.h          |  1 +
 include/uapi/linux/fs.h        |  1 +
 21 files changed, 221 insertions(+), 16 deletions(-)