1 files changed, 43 insertions, 24 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 49115b107fbd..ba61d0fa4b80 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -513,22 +513,25 @@ static int cache_defer_cnt;
 
 static void __unhash_deferred_req(struct cache_deferred_req *dreq)
 {
-	list_del_init(&dreq->recent);
 	hlist_del_init(&dreq->hash);
-	cache_defer_cnt--;
+	if (!list_empty(&dreq->recent)) {
+		list_del_init(&dreq->recent);
+		cache_defer_cnt--;
+	}
 }
 
 static void __hash_deferred_req(struct cache_deferred_req *dreq, struct cache_head *item)
 {
 	int hash = DFR_HASH(item);
 
-	list_add(&dreq->recent, &cache_defer_list);
+	INIT_LIST_HEAD(&dreq->recent);
 	hlist_add_head(&dreq->hash, &cache_defer_hash[hash]);
 }
 
-static void setup_deferral(struct cache_deferred_req *dreq, struct cache_head *item)
+static void setup_deferral(struct cache_deferred_req *dreq,
+			   struct cache_head *item,
+			   int count_me)
 {
-	struct cache_deferred_req *discard;
 
 	dreq->item = item;
 
@@ -536,18 +539,13 @@ static void setup_deferral(struct cache_deferred_req *dreq, struct cache_head *i
 
 	__hash_deferred_req(dreq, item);
 
-	/* it is in, now maybe clean up */
-	discard = NULL;
-	if (++cache_defer_cnt > DFR_MAX) {
-		discard = list_entry(cache_defer_list.prev,
-				     struct cache_deferred_req, recent);
-		__unhash_deferred_req(discard);
+	if (count_me) {
+		cache_defer_cnt++;
+		list_add(&dreq->recent, &cache_defer_list);
 	}
+
 	spin_unlock(&cache_defer_lock);
 
-	if (discard)
-		/* there was one too many */
-		discard->revisit(discard, 1);
 }
 
 struct thread_deferred_req {
@@ -570,7 +568,7 @@ static void cache_wait_req(struct cache_req *req, struct cache_head *item)
 	sleeper.completion = COMPLETION_INITIALIZER_ONSTACK(sleeper.completion);
 	dreq->revisit = cache_restart_thread;
 
-	setup_deferral(dreq, item);
+	setup_deferral(dreq, item, 0);
 
 	if (!test_bit(CACHE_PENDING, &item->flags) ||
 	    wait_for_completion_interruptible_timeout(
@@ -594,17 +592,36 @@ static void cache_wait_req(struct cache_req *req, struct cache_head *item)
 	}
 }
 
-static void cache_defer_req(struct cache_req *req, struct cache_head *item)
+static void cache_limit_defers(void)
 {
-	struct cache_deferred_req *dreq;
+	/* Make sure we haven't exceed the limit of allowed deferred
+	 * requests.
+	 */
+	struct cache_deferred_req *discard = NULL;
 
-	if (cache_defer_cnt >= DFR_MAX)
-		/* too much in the cache, randomly drop this one,
-		 * or continue and drop the oldest
-		 */
-		if (net_random()&1)
-			return;
+	if (cache_defer_cnt <= DFR_MAX)
+		return;
+
+	spin_lock(&cache_defer_lock);
 
+	/* Consider removing either the first or the last */
+	if (cache_defer_cnt > DFR_MAX) {
+		if (net_random() & 1)
+			discard = list_entry(cache_defer_list.next,
+					     struct cache_deferred_req, recent);
+		else
+			discard = list_entry(cache_defer_list.prev,
+					     struct cache_deferred_req, recent);
+		__unhash_deferred_req(discard);
+	}
+	spin_unlock(&cache_defer_lock);
+	if (discard)
+		discard->revisit(discard, 1);
+}
+
+static void cache_defer_req(struct cache_req *req, struct cache_head *item)
+{
+	struct cache_deferred_req *dreq;
 
 	if (req->thread_wait) {
 		cache_wait_req(req, item);
@@ -614,12 +631,14 @@ static void cache_defer_req(struct cache_req *req, struct cache_head *item)
 	dreq = req->defer(req);
 	if (dreq == NULL)
 		return;
-	setup_deferral(dreq, item);
+	setup_deferral(dreq, item, 1);
 	if (!test_bit(CACHE_PENDING, &item->flags))
 		/* Bit could have been cleared before we managed to
 		 * set up the deferral, so need to revisit just in case
 		 */
 		cache_revisit_request(item);
+
+	cache_limit_defers();
 }
 
 static void cache_revisit_request(struct cache_head *item)