On Tue, Oct 03, 2023 at 12:16:26PM +1100, Dave Chinner wrote:

On Fri, Sep 29, 2023 at 10:27:16AM +0000, John Garry wrote:

quoted

The low-space allocator doesn't honour the alignment requirement, so don't
attempt to even use it (when we have an alignment requirement).

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/libxfs/xfs_bmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 30c931b38853..328134c22104 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c

@@ -3569,6 +3569,10 @@ xfs_bmap_btalloc_low_space(
 {
 	int			error;
 
+	/* The allocator doesn't honour args->alignment */
+	if (args->alignment > 1)
+		return 0;
+

How does this happen?

The earlier failing aligned allocations will clear alignment before
we get here....

I was thinking the predicate should be xfs_inode_force_align(ip) to save
me/us from thinking about all the other weird ways args->alignment could
end up 1.

	/* forced-alignment means we don't use low mode */
	if (xfs_inode_force_align(ip))
		return -ENOSPC;

--D

-Dave.
-- 
Dave Chinner
david@fromorbit.com