sunrpc: add a cache_notify callback

A later patch will be changing the kernel to send a netlink notification
when there is a pending cache_request. Add a new cache_notify operation
to struct cache_detail for this purpose.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: jtlayton

include/linux/sunrpc/cache.h

@@ -80,6 +80,9 @@ struct cache_detail {
 	int			(*cache_upcall)(struct cache_detail *,
 						struct cache_head *);
 
+	int			(*cache_notify)(struct cache_detail *cd,
+						struct cache_head *h);
+
 	void			(*cache_request)(struct cache_detail *cd,
 						 struct cache_head *ch,
 						 char **bpp, int *blen);

net/sunrpc/cache.c

@@ -1233,6 +1233,8 @@ static int cache_do_upcall(struct cache_detail *detail, struct cache_head *h)
 		/* Lost a race, no longer PENDING, so don't enqueue */
 		ret = -EAGAIN;
 	spin_unlock(&detail->queue_lock);
+	if (ret != -EAGAIN && detail->cache_notify)
+		detail->cache_notify(detail, h);
 	wake_up(&detail->queue_wait);
 	if (ret == -EAGAIN) {
 		kfree(buf);