Re: [xfstests PATCH] ext4/053: fix the rejected mount option testing

[Eric Biggers <ebiggers@kernel.org>]

On Sat, Apr 30, 2022 at 12:21:30PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> 'not_mnt OPTIONS' seems to have been intended to test that the
> filesystem cannot be mounted at all with the given OPTIONS, meaning that
> the mount fails as opposed to the options being ignored.  However, this
> doesn't actually work, as shown by the fact that the test case 'not_mnt
> test_dummy_encryption=v3' is passing in the !CONFIG_FS_ENCRYPTION case.
> Actually ext4 ignores this mount option when !CONFIG_FS_ENCRYPTION.
> (The ext4 behavior might be changed, but that is besides the point.)
> 
> The problem is that the do_mnt() helper function is being misused in a
> context where a mount failure is expected, and it does some additional
> remount tests that don't make sense in that context.  So if the mount
> unexpectedly succeeds, then one of these later tests can still "fail",
> causing the unexpected success to be shadowed by a later failure, which
> causes the overall test case to pass since it expects a failure.
> 
> Fix this by reworking not_mnt() and not_remount_noumount() to use
> simple_mount() in cases where they are expecting a failure.  Also fix
> up some of the naming and calling conventions to be less confusing.
> Finally, make sure to test that remounting fails too, not just mounting.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  tests/ext4/053 | 148 ++++++++++++++++++++++++++-----------------------
>  1 file changed, 78 insertions(+), 70 deletions(-)

Lukas, any thoughts on this patch?  You're the author of this test.

- Eric