Re: [PATCH] generic/563: allow read tolerance for f2fs in scenario 3

On Fri, May 15, 2026 at 08:26:08AM +0000, Jan Prusakowski wrote:
> F2FS is a log-structured file system that allocates new blocks even for
> overwrites. To perform allocation, it may need to read metadata blocks
> (such as the Node Address Table (NAT) or Segment Info Table (SIT)) if
> they are not already in memory.
> 
> In scenario 3 (read -> read/write), unlike scenario 2, there is no prior
> write in the same mount session to load these metadata blocks into memory.
> Therefore, the write operation in the second cgroup triggers metadata
> reads, which are charged to that cgroup.
> 
> Relax the read tolerance for f2fs in scenario 3 to accommodate these
> expected metadata reads, matching the tolerance already used in scenario 2.
> 
> Signed-off-by: Jan Prusakowski <[email protected]>
> ---
>  tests/generic/563 | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/generic/563 b/tests/generic/563
> index c3705c2f..f95eb073 100755
> --- a/tests/generic/563
> +++ b/tests/generic/563
> @@ -151,7 +151,10 @@ $XFS_IO_PROG -c "pread 0 $iosize" -c "pwrite -b $blksize 0 $iosize" $SCRATCH_MNT
>  switch_cg $cgdir
>  $XFS_IO_PROG -c fsync $SCRATCH_MNT/file
>  check_cg $cgdir/$seq-cg $iosize $iosize 5% 5%
> -check_cg $cgdir/$seq-cg-2 0 0 0 0
> +# F2FS may perform metadata reads during write in this scenario
> +read_tol=0
> +[ "$FSTYP" = "f2fs" ] && read_tol=33792
> +check_cg $cgdir/$seq-cg-2 0 0 $read_tol 0

Make sense to me,

Reviewed-by: Zorro Lang <[email protected]>

>  
>  if [ "$drop_io_cgroup" = 1 ]; then
>  	echo "-io" > $cgdir/cgroup.subtree_control || _fail "subtree control"
> -- 
> 2.54.0.563.g4f69b47b94-goog
>