push BKL down into ->put_super

Move BKL into ->put_super from the only caller.  A couple of
filesystems had trivial enough ->put_super (only kfree and NULLing of
s_fs_info + stuff in there) to not get any locking: coda, cramfs, efs,
hugetlbfs, omfs, qnx4, shmem, all others got the full treatment.  Most
of them probably don't need it, but I'd rather sort that out individually.
Preferably after all the other BKL pushdowns in that area.

[AV: original used to move lock_super() down as well; these changes are
removed since we don't do lock_super() at all in generic_shutdown_super()
now]
[AV: fuse, btrfs and xfs are known to need no damn BKL, exempt]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/gfs2/super.c

@@ -719,6 +719,8 @@ static void gfs2_put_super(struct super_block *sb)
 	int error;
 	struct gfs2_jdesc *jd;
 
+	lock_kernel();
+
 	/*  Unfreeze the filesystem, if we need to  */
 
 	mutex_lock(&sdp->sd_freeze_lock);
@@ -785,6 +787,8 @@ restart:
 
 	/*  At this point, we're through participating in the lockspace  */
 	gfs2_sys_fs_del(sdp);
+
+	unlock_kernel();
 }
 
 /**