gfs2: Prevent double iput for journal on error

When a gfs2 file system is withdrawn it does iput on its journal to
allow recovery from another cluster node. If it's unable to get a
replacement inode for whatever reason, the journal descriptor would
still be pointing at the evicted inode. So when unmount clears out the
list of journals, it would do a second iput referencing the pointer.
To avoid this, set the inode pointer to NULL.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/util.c

@@ -204,6 +204,7 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
 	 * exception code in glock_dq.
 	 */
 	iput(inode);
+	sdp->sd_jdesc->jd_inode = NULL;
 	/*
 	 * Wait until the journal inode's glock is freed. This allows try locks
 	 * on other nodes to be successful, otherwise we remain the owner of