dlm: Change rwlock which is only used in write mode to a spinlock

The ls_dirtbl[].lock was an rwlock, but since it was only used in write
mode a spinlock will suffice.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index aa32e5f..cd8e2df 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -487,7 +487,7 @@
 		goto out_lkbfree;
 	for (i = 0; i < size; i++) {
 		INIT_LIST_HEAD(&ls->ls_dirtbl[i].list);
-		rwlock_init(&ls->ls_dirtbl[i].lock);
+		spin_lock_init(&ls->ls_dirtbl[i].lock);
 	}
 
 	INIT_LIST_HEAD(&ls->ls_waiters);