Re: [PATCH] generic/388: randomly recover via read-only mounts

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Dec 17, 2020 at 09:59:41AM -0500, Brian Foster wrote:
> XFS has an issue where superblock counters may not be properly
> synced when recovery occurs via a read-only mount. This causes the
> filesystem to become inconsistent after unmount. To cover this test
> case, update generic/388 to switch between read-only and read-write
> mounts to perform log recovery.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
> 
> I didn't think it was worth duplicating generic/388 to a whole new test
> just to invoke log recovery from a read-only mount. generic/388 is a
> rather general log recovery test and this preserves historical behavior
> of the test.
> 
> A prospective fix for the issue this reproduces on XFS is posted here:
> 
> https://lore.kernel.org/linux-xfs/20201217145334.2512475-1-bfoster@redhat.com/
> 
> Brian
> 
>  tests/generic/388 | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/generic/388 b/tests/generic/388
> index 451a6be2..cdd547f4 100755
> --- a/tests/generic/388
> +++ b/tests/generic/388
> @@ -66,8 +66,14 @@ for i in $(seq 1 $((50 * TIME_FACTOR)) ); do
>  		ps -e | grep fsstress > /dev/null 2>&1
>  	done
>  
> -	# quit if mount fails so we don't shutdown the host fs
> -	_scratch_cycle_mount || _fail "cycle mount failed"
> +	# Toggle between rw and ro mounts for recovery. Quit if any mount
> +	# attempt fails so we don't shutdown the host fs.
> +	if [ $((RANDOM % 2)) -eq 0 ]; then
> +		_scratch_cycle_mount || _fail "cycle mount failed"
> +	else
> +		_scratch_cycle_mount "ro" || _fail "cycle ro mount failed"
> +		_scratch_cycle_mount || _fail "cycle mount failed"

I would change that third failure message to something distinct, like:

_fail "cycle remount failed"

To give us extra clues as to which branch encountered failure.
This looks like a fun way to find new bugs. :)

--D

> +	fi
>  done
>  
>  # success, all done
> -- 
> 2.26.2
>