SUNRPC: Replace the cache_detail->hash_lock with a regular spinlock

Now that the reader functions are all RCU protected, use a regular
spinlock rather than a reader/writer lock.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index c3d67e8..5a3e950 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -67,7 +67,7 @@ struct cache_detail {
 	struct module *		owner;
 	int			hash_size;
 	struct hlist_head *	hash_table;
-	rwlock_t		hash_lock;
+	spinlock_t		hash_lock;
 
 	char			*name;
 	void			(*cache_put)(struct kref *);