Re: [PATCH v2] generic/798: chain xfs_io commands into a single invocation

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

On Wed, Aug 26, 2026 at 05:01:14PM +0200, Avinesh Kumar wrote:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> The write, cachestat, fsync, and cachestat calls were each run as
> separate xfs_io invocations, closing and reopening the file in
> between. Some filesystems flush dirty data back on close(), clearing
> the dirty bit before the first cachestat ever ran, causing test failure
> 
> - 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
>     ...
> 
> Run the whole sequence on one open file descriptor instead by chaining
> all xfs_io commands in single invocation.
> 
> Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
> ---
>  tests/generic/798 | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..171878ee 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -27,12 +27,22 @@ for num_page in 1 2 4 8 16; do
>  	echo "=== Test with $num_page pages ==="
>  
>  	rm -f $SCRATCH_MNT/foobar
> -	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
> -	# Basic cached number reporting
> -	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
>  
> -	# Test dirty page number reporting after a fsync.
> +	# Basic cached number reporting and test dirty page number
> +	# reporting after a fsync.
> +	#
> +	# Do the whole write+cachestat+fsync+cachestat sequence in a
> +	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
> +	# dirty data back to the server as part of their own close()-time
> +	# cache consistency, which would clear the dirty bits before the
> +	# second xfs_io process ever got to run cachestat.
>  	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
> +		$XFS_IO_PROG -f \

Not sure why there are two $XFS_IO_PROG invocations here??

Also the first line of the second invocation should only be indented one
tab, not two.

--D

> +		-c "pwrite -q -b $pagesize 0 $size" \
> +		-c "cachestat 0 $size" \
> +		-c "fsync" \
> +		-c "cachestat 0 $size" \
> +		$SCRATCH_MNT/foobar
>  done
>  
>  _scratch_unmount
> -- 
> 2.55.0
> 
>