Re: [PATCH RFC v2 3/3] ext4: don't advertise atomic writes for DAX inodes

[sashiko-bot@kernel.org]

> ext4_file_write_iter() hands DAX inodes to ext4_dax_write_iter() before
> any of the atomic write handling, and the DAX path neither checks
> IOCB_ATOMIC nor provides torn-write protection.
> ext4_inode_can_atomic_write() doesn't exclude DAX inodes, so on a device
> that supported both DAX and atomic writes, statx() would advertise
> atomic writes for such an inode and the VFS would let an RWF_ATOMIC
> write through to a plain DAX write.
> 
> No DAX-capable block device advertises atomic write limits today, so
> this isn't reachable. When XFS gained its corresponding check, Ritesh
> Harjani suggested excluding DAX inodes in ext4 anyway [1], so that what
> is advertised matches what the write path can do. XFS does the same in
> xfs_inode_can_hw_atomic_write() and xfs_inode_can_sw_atomic_write().
> 
> Link: https://lore.kernel.org/linux-ext4/87a54e4cdn.fsf@gmail.com/ [1]
> Signed-off-by: Tal Zussman <tz2294@columbia.edu>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261012-ext4-atomic-no-fallback-v2-0-c4b30c60e500@columbia.edu?part=3