Re: [PATCH] generic/798: exclude nfs from cachestat dirty page reporting test

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Aug 24, 2026 at 05:11:06PM +0200, Avinesh Kumar wrote:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> generic/798 checks cachestat() page cache dirty state between write and
> fsync operations.
> 
> On NFS, the client flushes dirty pages to the server during close() to
> enforce its close-to-open consistency model. Because the test uses separate
> xfs_io invocations, the file is closed after writing, leaving pages already
> clean by the time the subsequent cachestat command executes, causing the
> test to fail.
> 
> - output mismatch (see /opt/xfstests/results//generic/798.out.bad)
>     --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
>     +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
>     @@ -1,16 +1,16 @@
>      QA output created by 798
>      === Test with 1 pages ===
>     -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      === Test with 2 pages ===
>     -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     ...
> 
> Exclude 'nfs' from running this test.
> 
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
> ---
>  tests/generic/798 | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..80b2acc9 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -16,6 +16,12 @@ _require_scratch
>  _exclude_scratch_mount_option "dax"
>  _exclude_scratch_mount_option "sync"
>  
> +# NFS flushes dirty data back to the server on close() as part of its
> +# close-to-open cache consistency model, so a page written and closed in
> +# one xfs_io invocation is no longer dirty by the time cachestat runs in
> +# a later invocation.
> +_exclude_fs nfs

Could you just chain all the xfs_io commands together into a single
invocation?

$XFS_IO_PROG -f \
	-c "pwrite -b $pagesize 0 $size" \
	-c "cachestat 0 $size" \
	-c "fsync" \
	-c "cachestat 0 $size" \
	$SCRATCH_MNT/foobar

to solve this problem?

--D

> +
>  pagesize=$(_get_page_size)
>  
>  _scratch_mkfs > /dev/null
> -- 
> 2.55.0
> 
>