Re: [PATCH v2 5/5] common/overlay: silence some mount messages for fuse-overlayfs

[Amir Goldstein <amir73il@gmail.com>]

On Fri, Feb 14, 2020 at 5:19 PM Mauricio Faria de Oliveira
<mfo@canonical.com> wrote:
>
> When mouting fuse-overlayfs there are some messages that make
> the tests report failures due to output mismatch; ignore them:
>
>   uid=unchanged
>   uid=unchanged
>   upperdir=/mnt/test/ovl-upper
>   workdir=/mnt/test/ovl-work
>   lowerdir=/mnt/test/ovl-lower
>   mountpoint=/mnt/test/ovl-mnt
>
> For other filesystem types (e.g., overlay and aufs) make sure to
> only print non-null output, to avoid blank lines output mismatch.
>
> And return the status of the mount command, not other commands.
>
> Currently, running './check -overlay' tests (excluding generic/062)
> the numbers for fuse-overlayfs on loop devices on v5.4-based Ubuntu
> kernel with the fuse-overlayfs package from Ubuntu Eoan/19.10 are:
>
>  - Ran: 530
>  - Not run: 395
>  - Failures: 29
>
> And hopefully this helps with testing for fuse-overlayfs too.
>
> Steps:
>
>   $ export OVL_FSTYP=fuse.fuse-overlayfs
>   $ export FSTYP=ext4
>   $ export TEST_DEV=/dev/loop0
>   $ export TEST_DIR=/mnt/test
>   $ export SCRATCH_DEV=/dev/loop1
>   $ export SCRATCH_MNT=/mnt/scratch
>
>   $ sudo mkfs.$FSTYP -F $TEST_DEV
>   $ sudo mkfs.$FSTYP -F $SCRATCH_DEV
>   $ sudo mkdir $TEST_DIR $SCRATCH_MNT
>
>   $ cat <<EOF >/tmp/exclude-tests
>   generic/062
>   EOF
>
>   $ sudo -E ./check -overlay -E /tmp/exclude-tests
>
> Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
> ---
>  common/overlay | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/common/overlay b/common/overlay
> index a1076926c23f..27f3c08252ee 100644
> --- a/common/overlay
> +++ b/common/overlay
> @@ -19,6 +19,8 @@ _overlay_mount_dirs()
>         local upperdir=$2
>         local workdir=$3
>         local options
> +       local output
> +       local rc
>         shift 3
>
>         options="-o lowerdir=$lowerdir -o upperdir=$upperdir -o workdir=$workdir"
> @@ -26,7 +28,23 @@ _overlay_mount_dirs()
>                 options="-o br=$upperdir=rw -o br=$lowerdir=ro"
>         fi
>
> -       $MOUNT_PROG -t $OVL_FSTYP $options `_common_dev_mount_options $*`
> +       options="$options `_common_dev_mount_options $*`"
> +       output="`$MOUNT_PROG -t $OVL_FSTYP $options 2>&1`"
> +       rc=$?
> +
> +       if [ "$OVL_FSTYP" = "fuse.fuse-overlayfs" ]; then
> +               # Less verbosity to avoid output mismatch.
> +               echo "$output" | grep -v \
> +                       -e "^uid=" \
> +                       -e "^upperdir=" \
> +                       -e "^lowerdir=" \
> +                       -e "^workdir=" \
> +                       -e "^mountpoint="
> +       elif [ -n "$output" ]; then
> +               echo "$output"
> +       fi
> +
> +       return $rc

rc will always be 0 because it holds the return code of the assignment
expression 'output=...', not the return code of mount.

Does fuse mount verbose output go to stdout or to stderr?
I don't think we ever care about stdout of this mount command
on golden output - it is always assumed to be silent and
only a silent or noisy stderr is verified in golden output.
So if I am not mistaken and if fuse verbose output it to stdout,
then maybe would be enough to redirect stdout to /dev/null?

Thanks,
Amir.