Re: [PATCH 1/2] xfs/078: disable all concurrency scaling

[Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Jun 18, 2026 / 09:23, Eric Sandeen wrote:
> On 6/18/26 8:54 AM, Eric Sandeen wrote:
> > On 6/18/26 8:48 AM, Christoph Hellwig wrote:
> >> Disable concurrency scaling to avoid mismatching output on systems with
> >> a large CPU count.
> >>
> >> Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> >> Signed-off-by: Christoph Hellwig <hch@lst.de>
> > 
> > I think this papers over what I still feel is a problem in mkfs.xfs
> > behavior, but that's a different issue and making tests pass is good, so:
> > 
> > Reviewed-by: Eric Sandeen <sandeen@redhat.com>
> 
> Er, hang on - let me retract that. Lukas sent a series to address
> this problem too, right, and one of the things he added in his series
> is a helper to determine whether the concurrency options even exist,
> so that this can continue to run on older xfsprogs, which seems like
> a good idea, no?
> 
> https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/commit/?h=for-next&id=7f162f5bcf50fc32c7e3b432e7ff189571a3151f
> 
> which added _scratch_mkfs_xfs_supports_concurrency()

I agree, I think we can add the change below on top of this patch.
Regardless of the change, I confirmed that this patch avoids the failure
that I reported. Thanks!

Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>

diff --git a/tests/xfs/078 b/tests/xfs/078
index 8ef5261..dc0668e 100755
--- a/tests/xfs/078
+++ b/tests/xfs/078
@@ -59,7 +59,11 @@ _grow_loop()
 
 	# Disable concurrency scaling to avoid output differences due to large
 	# CPU counts.
-	mkfs_opts="-d concurrency=0 -l concurrency=0 -r concurrency=0"
+	if _scratch_mkfs_xfs_supports_concurrency -l >> $seqres.full 2>&1; then
+		mkfs_opts="-d concurrency=0 -l concurrency=0 -r concurrency=0"
+	else
+		mkfs_opts=""
+	fi
 	if [ -n "$agsize" ]; then
 		mkfs_opts="$mkfs_opts -d agsize=$agsize"
 	fi