[PATCH 46/56] xfs: fix xfs_get_extsz_hint behavior with realtime alwayscow files

Darrick J. Wong
2025-02-06T22:47:08Z

Source kernel commit: 6853d23badd0f1852d3b711128924e2456d27634

Currently, we (ab)use xfs_get_extsz_hint so that it always returns a
nonzero value for realtime files. This apparently was done to disable
delayed allocation for realtime files.

However, once we enable realtime reflink, we can also turn on the
alwayscow flag to force CoW writes to realtime files. In this case, the
logic will incorrectly send the write through the delalloc write path.

Fix this by adjusting the logic slightly.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
libxfs/xfs_bmap.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index 9cfbdb85c975a5..ed969983cccd1b 100644
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -6494,9 +6494,8 @@ xfs_get_extsz_hint(
* No point in aligning allocations if we need to COW to actually
* write to them.
*/
- if (xfs_is_always_cow_inode(ip))
- return 0;
- if ((ip->i_diflags & XFS_DIFLAG_EXTSIZE) && ip->i_extsize)
+ if (!xfs_is_always_cow_inode(ip) &&
+ (ip->i_diflags & XFS_DIFLAG_EXTSIZE) && ip->i_extsize)
return ip->i_extsize;
if (XFS_IS_REALTIME_INODE(ip) &&
ip->i_mount->m_sb.sb_rextsize > 1)