generic: Test filesystem lockup on full overprovisioned dm-thin

generic: Test filesystem lockup on full overprovisioned dm-thin

With thin devices, it's possible to have a virtual device larger
than the physical device itself, and such situation can cause
problems to filesystems, once the filesystem 'believe' to have more
space than it actually has.

This can lead the filesystem to several weird behaviors. The one
tested here is filesystem lockup.

In case of XFS, it locks up when trying to writeback AIL metadata
back to the filesystem, but, once there is no physical space
available, XFS locks up and do not gracefuly handle this case.

Other filesystems usually are remounted as read-only, so they
already have this situation covered.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>