fix fs->lock deadlock

[David Mosberger]

The patch below is needed to avoid a deadlock on fs->lock.  Without
the patch, if __emul_lookup_dentry() returns 0, we fail to reacquire
current->fs->lock and then go ahead to read_unlock() it anyhow.  Bad
for your health.

I believe the bug was introduced by this change set (about 9 weeks ago):

  http://linux.bkbits.net:8080/linux-2.5/diffs/fs/namei.c@1.63.1.2

	--david

===== fs/namei.c 1.69 vs edited =====
--- 1.69/fs/namei.c	Wed Apr  2 22:51:31 2003
+++ edited/fs/namei.c	Wed Apr 16 10:18:40 2003
@@ -847,6 +847,7 @@
 			read_unlock(&current->fs->lock);
 			if (__emul_lookup_dentry(name,nd))
 				return 0;
+			read_lock(&current->fs->lock);
 		}
 		nd->mnt = mntget(current->fs->rootmnt);
 		nd->dentry = dget(current->fs->root);