1 files changed, 39 insertions, 15 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index e433e7580e27..72ad836e4fe0 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -37,7 +37,7 @@
 
 #define  RPCDBG_FACILITY RPCDBG_CACHE
 
-static void cache_defer_req(struct cache_req *req, struct cache_head *item);
+static bool cache_defer_req(struct cache_req *req, struct cache_head *item);
 static void cache_revisit_request(struct cache_head *item);
 
 static void cache_init(struct cache_head *h)
@@ -128,6 +128,7 @@ static void cache_fresh_locked(struct cache_head *head, time_t expiry)
 {
         head->expiry_time = expiry;
         head->last_refresh = seconds_since_boot();
+        smp_wmb(); /* paired with smp_rmb() in cache_is_valid() */
         set_bit(CACHE_VALID, &head->flags);
 }
 
@@ -208,11 +209,36 @@ static inline int cache_is_valid(struct cache_detail *detail, struct cache_head
                 /* entry is valid */
                 if (test_bit(CACHE_NEGATIVE, &h->flags))
                         return -ENOENT;
-                else
+                else {
+                        /*
+                         * In combination with write barrier in
+                         * sunrpc_cache_update, ensures that anyone
+                         * using the cache entry after this sees the
+                         * updated contents:
+                         */
+                        smp_rmb();
                         return 0;
+                }
         }
 }
 
+static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h)
+{
+        int rv;
+
+        write_lock(&detail->hash_lock);
+        rv = cache_is_valid(detail, h);
+        if (rv != -EAGAIN) {
+                write_unlock(&detail->hash_lock);
+                return rv;
+        }
+        set_bit(CACHE_NEGATIVE, &h->flags);
+        cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
+        write_unlock(&detail->hash_lock);
+        cache_fresh_unlocked(h, detail);
+        return -ENOENT;
+}
+
 /*
  * This is the generic cache management routine for all
  * the authentication caches.
@@ -251,14 +277,8 @@ int cache_check(struct cache_detail *detail,
                         case -EINVAL:
                                 clear_bit(CACHE_PENDING, &h->flags);
                                 cache_revisit_request(h);
-                                if (rv == -EAGAIN) {
-                                        set_bit(CACHE_NEGATIVE, &h->flags);
-                                        cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
-                                        cache_fresh_unlocked(h, detail);
-                                        rv = -ENOENT;
-                                }
+                                rv = try_to_negate_entry(detail, h);
                                 break;
-
                         case -EAGAIN:
                                 clear_bit(CACHE_PENDING, &h->flags);
                                 cache_revisit_request(h);
@@ -268,9 +288,11 @@ int cache_check(struct cache_detail *detail,
         }
 
         if (rv == -EAGAIN) {
-                cache_defer_req(rqstp, h);
-                if (!test_bit(CACHE_PENDING, &h->flags)) {
-                        /* Request is not deferred */
+                if (!cache_defer_req(rqstp, h)) {
+                        /*
+                         * Request was not deferred; handle it as best
+                         * we can ourselves:
+                         */
                         rv = cache_is_valid(detail, h);
                         if (rv == -EAGAIN)
                                 rv = -ETIMEDOUT;
@@ -618,18 +640,19 @@ static void cache_limit_defers(void)
                 discard->revisit(discard, 1);
 }
 
-static void cache_defer_req(struct cache_req *req, struct cache_head *item)
+/* Return true if and only if a deferred request is queued. */
+static bool 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);
                 if (!test_bit(CACHE_PENDING, &item->flags))
-                        return;
+                        return false;
         }
         dreq = req->defer(req);
         if (dreq == NULL)
-                return;
+                return false;
         setup_deferral(dreq, item, 1);
         if (!test_bit(CACHE_PENDING, &item->flags))
                 /* Bit could have been cleared before we managed to
@@ -638,6 +661,7 @@ static void cache_defer_req(struct cache_req *req, struct cache_head *item)
                 cache_revisit_request(item);
 
         cache_limit_defers();
+        return true;
 }
 
 static void cache_revisit_request(struct cache_head *item)