[PATCH] Hold BKL for shorter period in generic_shutdown_super().

Testing revealed long pauses of the entire system while autofs initiated
umounts as a result of timing out the mounts.

It was noticed that during a umount, the BKL is held while scanning the
inode_list and removing and inodes that are candidates.  This patch moves
locking until after the first pass had gone through the inode_list.

Testing revelead that on an ia64 machine with a filesystem that had 8.4
Million inodes, there were no observable pauses during the umount.  This
was down from over 4 seconds without this patch.
Signed-Off-By: Robin Holt <holt@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/super.c

@@ -232,10 +232,10 @@ void generic_shutdown_super(struct super_block *sb)
 		dput(root);
 		fsync_super(sb);
 		lock_super(sb);
-		lock_kernel();
 		sb->s_flags &= ~MS_ACTIVE;
 		/* bad name - it should be evict_inodes() */
 		invalidate_inodes(sb);
+		lock_kernel();
 
 		if (sop->write_super && sb->s_dirt)
 			sop->write_super(sb);