[PATCH 0/6] block atomic writes for XFS

[John Garry <john.g.garry@oracle.com>]

This series expands atomic write support to filesystems, specifically
XFS. Since XFS rtvol supports extent alignment already, support will
initially be added there. When XFS forcealign feature is merged, then we
can similarly support atomic writes for a non-rtvol filesystem.

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

For XFS rtvol, support can be enabled through xfs_io command:
$xfs_io -c "chattr +W" filename
$xfs_io -c "lsattr -v" filename
[realtime, atomic-writes] filename

The FS needs to be formatted with a specific extent alignment size, like:
mkf.xfs -r rtdev=/dev/sdb,extsize=16K -d rtinherit=1 /dev/sda

This enables 16K atomic write support. There are no checks whether the
underlying HW actually supports that for enabling atomic writes with
xfs_io, though, so statx needs to be issued for a file to know atomic
write limits.

For supporting non-rtvol, we will require forcealign enabled. As such, a
dedicated xfs_io command to enable atomic writes for a regular FS may
be useful, which would enable FS_XFLAG_ATOMICWRITES, enable forcealign,
and set an extent alignment hint.

Baseline is following series (which is based on v6.8-rc1):
https://urldefense.com/v3/__https://lore.kernel.org/linux-nvme/20240124113841.31824-1-john.g.garry@oracle.com/T/*m4ad28b480a8e12eb51467e17208d98ca50041ff2__;Iw!!ACWV5N9M2RV99hQ!PKOcFzPtVYZ9uATl1BrTJmYanWxEtCKJPV-tTPDYqeTjuWmChXn08ZcmP_H07A9mxPyQ8wwjdSzgH0eYU_45MaIOJyEW$ 

Basic xfsprogs support at:
https://urldefense.com/v3/__https://github.com/johnpgarry/xfsprogs-dev/tree/atomicwrites__;!!ACWV5N9M2RV99hQ!PKOcFzPtVYZ9uATl1BrTJmYanWxEtCKJPV-tTPDYqeTjuWmChXn08ZcmP_H07A9mxPyQ8wwjdSzgH0eYU_45MTapy6qp$ 

John Garry (6):
  fs: iomap: Atomic write support
  fs: Add FS_XFLAG_ATOMICWRITES flag
  fs: xfs: Support FS_XFLAG_ATOMICWRITES for rtvol
  fs: xfs: Support atomic write for statx
  fs: xfs: iomap atomic write support
  fs: xfs: Set FMODE_CAN_ATOMIC_WRITE for FS_XFLAG_ATOMICWRITES set

 fs/iomap/direct-io.c       | 21 +++++++++++++++++-
 fs/iomap/trace.h           |  3 ++-
 fs/xfs/libxfs/xfs_format.h |  8 +++++--
 fs/xfs/libxfs/xfs_sb.c     |  2 ++
 fs/xfs/xfs_file.c          |  2 ++
 fs/xfs/xfs_inode.c         | 22 +++++++++++++++++++
 fs/xfs/xfs_inode.h         |  7 ++++++
 fs/xfs/xfs_ioctl.c         | 19 ++++++++++++++--
 fs/xfs/xfs_iomap.c         | 41 ++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iops.c          | 45 ++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iops.h          |  4 ++++
 fs/xfs/xfs_mount.h         |  2 ++
 fs/xfs/xfs_super.c         |  4 ++++
 include/linux/iomap.h      |  1 +
 include/uapi/linux/fs.h    |  1 +
 15 files changed, 176 insertions(+), 6 deletions(-)

-- 
2.31.1