Fix LVM snapshot deadlock

Fix LVM snapshot deadlock: it is a bad idea to try to flush all running
transactions while we already hold the superblock lock.  Drop the sb lock
while we flush.

This only affects kernels that have the extra LVM VFS locking added in
for filesystem quiescing on snapshots.

--- linux-2.4.19-ext3/fs/ext3/super.c.=K0010=.orig	Mon Feb 25 19:38:08 2002
+++ linux-2.4.19-ext3/fs/ext3/super.c	Fri Oct 11 15:52:00 2002
@@ -1589,8 +1589,10 @@
 		journal_t *journal = EXT3_SB(sb)->s_journal;
 
 		/* Now we set up the journal barrier. */
+		unlock_super(sb);
 		journal_lock_updates(journal);
 		journal_flush(journal);
+		lock_super(sb);
 
 		/* Journal blocked and flushed, clear needs_recovery flag. */
 		EXT3_CLEAR_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_RECOVER);