From 68456d05eb57a5d16b4be2d3caf421bdcf2de72e Mon Sep 17 00:00:00 2001 From: John Garry Date: Thu, 24 Jul 2025 08:12:14 +0000 Subject: xfs: disallow atomic writes on DAX Atomic writes are not currently supported for DAX, but two problems exist: - we may go down DAX write path for IOCB_ATOMIC, which does not handle IOCB_ATOMIC properly - we report non-zero atomic write limits in statx (for DAX inodes) We may want atomic writes support on DAX in future, but just disallow for now. For this, ensure when IOCB_ATOMIC is set that we check the write size versus the atomic write min and max before branching off to the DAX write path. This is not strictly required for DAX, as we should not get this far in the write path as FMODE_CAN_ATOMIC_WRITE should not be set. In addition, due to reflink being supported for DAX, we automatically get CoW-based atomic writes support being advertised. Remedy this by disallowing atomic writes for a DAX inode for both sw and hw modes. Reported-by: Darrick J. Wong Fixes: 9dffc58f2384 ("xfs: update atomic write limits") Reviewed-by: Darrick J. Wong Signed-off-by: John Garry Signed-off-by: Carlos Maiolino --- fs/xfs/xfs_iops.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'fs/xfs/xfs_iops.c') diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c index 149b5460fbfd..603effabe1ee 100644 --- a/fs/xfs/xfs_iops.c +++ b/fs/xfs/xfs_iops.c @@ -616,7 +616,8 @@ xfs_get_atomic_write_min( * write of exactly one single fsblock if the bdev will make that * guarantee for us. */ - if (xfs_inode_can_hw_atomic_write(ip) || xfs_can_sw_atomic_write(mp)) + if (xfs_inode_can_hw_atomic_write(ip) || + xfs_inode_can_sw_atomic_write(ip)) return mp->m_sb.sb_blocksize; return 0; @@ -633,7 +634,7 @@ xfs_get_atomic_write_max( * write of exactly one single fsblock if the bdev will make that * guarantee for us. */ - if (!xfs_can_sw_atomic_write(mp)) { + if (!xfs_inode_can_sw_atomic_write(ip)) { if (xfs_inode_can_hw_atomic_write(ip)) return mp->m_sb.sb_blocksize; return 0; -- cgit v1.2.3