[GFS2] Get superblock a different way

The mapping may be NULL by the time the I/O has completed, so
we now get the superblock by a different route (via the bd and glock)
to avoid this problem.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Wendy Cheng <wcheng@redhat.com>
1 file changed