gfs2: Fix missed wakeups in find_insert_glock

commit 605b0487 upstream.

Mark Syms has reported seeing tasks that are stuck waiting in
find_insert_glock.  It turns out that struct lm_lockname contains four padding
bytes on 64-bit architectures that function glock_waitqueue doesn't skip when
hashing the glock name.  As a result, we can end up waking up the wrong
waitqueue, and the waiting tasks may be stuck forever.

Fix that by using ht_parms.key_len instead of sizeof(struct lm_lockname) for
the key length.
Reported-by: Mark Syms <mark.syms@citrix.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/gfs2/glock.c

@@ -107,7 +107,7 @@ static int glock_wake_function(wait_queue_entry_t *wait, unsigned int mode,
 
 static wait_queue_head_t *glock_waitqueue(struct lm_lockname *name)
 {
-	u32 hash = jhash2((u32 *)name, sizeof(*name) / 4, 0);
+	u32 hash = jhash2((u32 *)name, ht_parms.key_len / 4, 0);
 
 	return glock_wait_table + hash_32(hash, GLOCK_WAIT_TABLE_BITS);
 }