Thread (104 messages) 104 messages, 13 authors, 2023-12-05

Re: [PATCH 11/21] fs: xfs: Don't use low-space allocator for alignment > 1

From: "Darrick J. Wong" <djwong@kernel.org>
Date: 2023-10-03 03:00:14
Also in: linux-block, linux-fsdevel, linux-nvme, linux-xfs, lkml

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
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