Re: [PATCH 8/9] xfs/166: fix golden output failures when multipage folios enabled

[Dave Chinner <david@fromorbit.com>]

On Tue, Jun 28, 2022 at 01:22:02PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Beginning with 5.18, some filesystems support creating large folios for
> the page cache.  A system with 64k pages can create 256k folios, which
> means that with the old file size of 1M, the last half of the file is
> completely converted from unwritten to written by page_mkwrite.  The
> test encodes a translated version of the xfs_bmap output in the golden
> output, which means that the test now fails on 64k pages.  Fixing the
> 64k page case by increasing the file size to 2MB broke fsdax because
> fsdax uses 2MB PMDs, hence 12MB.
> 
> Increase the size to prevent this from happening.  This may require
> further revision if folios get larger or fsdax starts supporting PMDs
> that are larger than 2MB.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  tests/xfs/166 |   19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> 
> diff --git a/tests/xfs/166 b/tests/xfs/166
> index 42379961..d45dc5e8 100755
> --- a/tests/xfs/166
> +++ b/tests/xfs/166
> @@ -16,12 +16,12 @@ _begin_fstest rw metadata auto quick
>  # the others are unwritten.
>  _filter_blocks()
>  {
> -	$AWK_PROG '
> +	$AWK_PROG -v file_size=$FILE_SIZE '
>  /^ +[0-9]/ {
>  	if (!written_size) {
>  		written_size = $6
> -		unwritten1 = ((1048576/512) / 2) - written_size
> -		unwritten2 = ((1048576/512) / 2) - 2 * written_size
> +		unwritten1 = ((file_size/512) / 2) - written_size
> +		unwritten2 = ((file_size/512) / 2) - 2 * written_size
>  	}
>  
>  	# is the extent unwritten?
> @@ -58,7 +58,18 @@ _scratch_mount
>  
>  TEST_FILE=$SCRATCH_MNT/test_file
>  TEST_PROG=$here/src/unwritten_mmap
> -FILE_SIZE=1048576
> +
> +# Beginning with 5.18, some filesystems support creating large folios for the
> +# page cache.  A system with 64k pages can create 256k folios, which means
> +# that with the old file size of 1M, the last half of the file is completely
> +# converted from unwritten to written by page_mkwrite.  The test will fail on
> +# the golden output when this happens, so increase the size from the original
> +# 1MB file size to at least (6 * 256k == 1.5MB) prevent this from happening.
> +#
> +# However, increasing the file size to around 2MB causes regressions when fsdax
> +# is enabled because fsdax will try to use PMD entries for the mappings.  Hence
> +# we need to set the file size to (6 * 2MB == 12MB) to cover all cases.
> +FILE_SIZE=$((12 * 1048576))

LGTM.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
-- 
Dave Chinner
david@fromorbit.com