Re: [PATCH v2] generic/459: improve shutdown/read-only check to accommodate bcachefs

[Bill O'Donnell <bodonnel@redhat.com>]

On Wed, Nov 29, 2023 at 03:16:14PM -0500, Brian Foster wrote:
> generic/459 occasionally fails on bcachefs because the deliberately
> induced I/O errors caused by exhausting the overprovisioned thin
> pool can lead to filesystem shutdown. This test considers this
> expected behavior on certain fs', but only checks for the ext4
> remount read-only behavior. bcachefs does a similar emergency
> read-only transition in response to certain I/O errors, but it
> behaves more similar to an XFS shutdown and doesn't necessarily
> reflect "ro" state in the mount table (unless induced by userspace).
> 
> Since the test already runs a touch command to help trigger the ext4
> error handling sequence, this can be tweaked to serve double duty
> and also more accurately detect read-only status on bcachefs.
> Refactor into a small helper, check for touch command failure, and
> consider the fs read-only if either that or the mount entry check
> indicates it.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>

Looks fine.

Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>

> ---
> 
> v2:
> - Drop error filtering and just check touch failure.
> - Comment tweaks.
> v1: https://lore.kernel.org/fstests/20231117144317.10882-1-bfoster@redhat.com/
> 
>  tests/generic/459 | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/tests/generic/459 b/tests/generic/459
> index 4dd7a43b..c3f0b2b0 100755
> --- a/tests/generic/459
> +++ b/tests/generic/459
> @@ -57,6 +57,24 @@ origpsize=200
>  virtsize=300
>  newpsize=300
>  
> +# Check whether the filesystem has shutdown or remounted read-only. Shutdown
> +# behavior can differ based on filesystem and configuration. Some fs' may not
> +# have remounted without an additional write while others may have shutdown but
> +# do not necessarily reflect read-only state in the mount options. Check both
> +# here by first trying a simple write and following with an explicit ro check.
> +is_shutdown_or_ro()
> +{
> +	ro=0
> +
> +	# if the fs has not shutdown, this may help trigger a remount-ro
> +	touch $SCRATCH_MNT/newfile > /dev/null 2>&1 || ro=1
> +
> +	_fs_options /dev/mapper/$vgname-$snapname | grep -w "ro" > /dev/null
> +	[ $? == 0 ] && ro=1
> +
> +	echo $ro
> +}
> +
>  # Ensure we have enough disk space
>  _scratch_mkfs_sized $((350 * 1024 * 1024)) >>$seqres.full 2>&1
>  
> @@ -113,13 +131,9 @@ ret=$?
>  #	- The filesystem stays in Read-Write mode, but can be frozen/thawed
>  #	  without getting stuck.
>  if [ $ret -ne 0 ]; then
> -	# freeze failed, filesystem should reject further writes and remount
> -	# as readonly. Sometimes the previous write process won't trigger
> -	# ro-remount, e.g. on ext3/4, do additional touch here to make sure
> -	# filesystems see the metadata I/O error.
> -	touch $SCRATCH_MNT/newfile >/dev/null 2>&1
> -	ISRO=$(_fs_options /dev/mapper/$vgname-$snapname | grep -w "ro")
> -	if [ -n "$ISRO" ]; then
> +	# freeze failed, filesystem should reject further writes
> +	ISRO=`is_shutdown_or_ro`
> +	if [ $ISRO == 1 ]; then
>  		echo "Test OK"
>  	else
>  		echo "Freeze failed and FS isn't Read-Only. Test Failed"
> -- 
> 2.41.0
> 
>