GFS2: Set s_mode before parsing mount options

In the generic mount_bdev() function, deactivate_locked_super() is
called after the fill_super() call fails, at which point s_mode has been
set. kill_block_super() expects this and dumps a warning when
FMODE_EXCL is not set in s_mode.

In gfs2_mount() we call deactivate_locked_super() on failure of
gfs2_mount_args(), at which point s_mode has not yet been set. This
causes kill_block_super() to dump a stack trace when gfs2 fails to mount
with invalid options. Set s_mode earlier in gfs2_mount() to avoid that.
Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/ops_fstype.c

@@ -1291,6 +1291,9 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags,
 		up_write(&s->s_umount);
 		blkdev_put(bdev, mode);
 		down_write(&s->s_umount);
+	} else {
+		/* s_mode must be set before deactivate_locked_super calls */
+		s->s_mode = mode;
 	}
 
 	memset(&args, 0, sizeof(args));
@@ -1314,7 +1317,6 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags,
 	} else {
 		char b[BDEVNAME_SIZE];
 
-		s->s_mode = mode;
 		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 		sb_set_blocksize(s, block_size(bdev));
 		error = fill_super(s, &args, flags & MS_SILENT ? 1 : 0);