Re: [PATCH 23/33] generic/{409,410,411,589}: check for stacking mount support

Amir Goldstein
2025-10-30T10:25:25Z

On Wed, Oct 29, 2025 at 2:29 AM Darrick J. Wong <djwong@kernel.org> wrote:
>
> From: Darrick J. Wong <djwong@kernel.org>
>
> _get_mount depends on the ability for commands such as "mount /dev/sda
> /a/second/mountpoint -o per_mount_opts" to succeed when /dev/sda is
> already mounted elsewhere.
>
> The kernel isn't going to notice that /dev/sda is already mounted, so
> the mount(8) call won't do the right thing even if per_mount_opts match
> the existing mount options.
>
> If per_mount_opts doesn't match, we'd have to convey the new per-mount
> options to the kernel. In theory we could make the fuse2fs argument
> parsing even more complex to support this use case, but for now fuse2fs
> doesn't know how to do that.
>
> Until that happens, let's _notrun these tests.
>
> Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
> ---
> common/rc | 24 ++++++++++++++++++++++++
> tests/generic/409 | 1 +
> tests/generic/410 | 1 +
> tests/generic/411 | 1 +
> tests/generic/589 | 1 +
> 5 files changed, 28 insertions(+)
>
>
> diff --git a/common/rc b/common/rc
> index f5b10a280adec9..b6e76c03a12445 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -364,6 +364,30 @@ _clear_mount_stack()
> MOUNTED_POINT_STACK=""
> }
>
> +# Check that this filesystem supports stack mounts
> +_require_mount_stack()
> +{
> + case "$FSTYP" in
> + fuse.ext[234])
> + # _get_mount depends on the ability for commands such as
> + # "mount /dev/sda /a/second/mountpoint -o per_mount_opts" to
> + # succeed when /dev/sda is already mounted elsewhere.
> + #
> + # The kernel isn't going to notice that /dev/sda is already
> + # mounted, so the mount(8) call won't do the right thing even
> + # if per_mount_opts match the existing mount options.
> + #
> + # If per_mount_opts doesn't match, we'd have to convey the new
> + # per-mount options to the kernel. In theory we could make the
> + # fuse2fs argument parsing even more complex to support this
> + # use case, but for now fuse2fs doesn't know how to do that.
> + _notrun "fuse2fs servers do not support stacking mounts"
> + ;;

I believe this is true for fuse* in general. no?

Thanks,
Amir.