svcrpc: cache deferral cleanup

Attempt to make obvious the first-try-sleeping-then-try-deferral logic
by putting that logic into a top-level function that calls helpers.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 18e5e8e..da872f9 100644 (file)
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -509,17 +509,6 @@ static LIST_HEAD(cache_defer_list);
 static struct list_head cache_defer_hash[DFR_HASHSIZE];
 static int cache_defer_cnt;
 
-struct thread_deferred_req {
-       struct cache_deferred_req handle;
-       struct completion completion;
-};
-static void cache_restart_thread(struct cache_deferred_req *dreq, int too_many)
-{
-       struct thread_deferred_req *dr =
-               container_of(dreq, struct thread_deferred_req, handle);
-       complete(&dr->completion);
-}
-
 static void __unhash_deferred_req(struct cache_deferred_req *dreq)
 {
        list_del_init(&dreq->recent);
@@ -537,29 +526,9 @@ static void __hash_deferred_req(struct cache_deferred_req *dreq, struct cache_he
        list_add(&dreq->hash, &cache_defer_hash[hash]);
 }
 
-static int cache_defer_req(struct cache_req *req, struct cache_head *item)
+static int setup_deferral(struct cache_deferred_req *dreq, struct cache_head *item)
 {
-       struct cache_deferred_req *dreq, *discard;
-       struct thread_deferred_req sleeper;
-
-       if (cache_defer_cnt >= DFR_MAX) {
-               /* too much in the cache, randomly drop this one,
-                * or continue and drop the oldest below
-                */
-               if (net_random()&1)
-                       return -ENOMEM;
-       }
-       if (req->thread_wait) {
-               dreq = &sleeper.handle;
-               sleeper.completion =
-                       COMPLETION_INITIALIZER_ONSTACK(sleeper.completion);
-               dreq->revisit = cache_restart_thread;
-       } else
-               dreq = req->defer(req);
-
- retry:
-       if (dreq == NULL)
-               return -ENOMEM;
+       struct cache_deferred_req *discard;
 
        dreq->item = item;
 
@@ -585,42 +554,88 @@ static int cache_defer_req(struct cache_req *req, struct cache_head *item)
                cache_revisit_request(item);
                return -EAGAIN;
        }
+       return 0;
+}
 
-       if (dreq == &sleeper.handle) {
-               if (wait_for_completion_interruptible_timeout(
-                           &sleeper.completion, req->thread_wait) <= 0) {
-                       /* The completion wasn't completed, so we need
-                        * to clean up
-                        */
-                       spin_lock(&cache_defer_lock);
-                       if (!list_empty(&sleeper.handle.hash)) {
-                               __unhash_deferred_req(&sleeper.handle);
-                               spin_unlock(&cache_defer_lock);
-                       } else {
-                               /* cache_revisit_request already removed
-                                * this from the hash table, but hasn't
-                                * called ->revisit yet.  It will very soon
-                                * and we need to wait for it.
-                                */
-                               spin_unlock(&cache_defer_lock);
-                               wait_for_completion(&sleeper.completion);
-                       }
-               }
-               if (test_bit(CACHE_PENDING, &item->flags)) {
-                       /* item is still pending, try request
-                        * deferral
+struct thread_deferred_req {
+       struct cache_deferred_req handle;
+       struct completion completion;
+};
+
+static void cache_restart_thread(struct cache_deferred_req *dreq, int too_many)
+{
+       struct thread_deferred_req *dr =
+               container_of(dreq, struct thread_deferred_req, handle);
+       complete(&dr->completion);
+}
+
+static int cache_wait_req(struct cache_req *req, struct cache_head *item)
+{
+       struct thread_deferred_req sleeper;
+       struct cache_deferred_req *dreq = &sleeper.handle;
+       int ret;
+
+       sleeper.completion = COMPLETION_INITIALIZER_ONSTACK(sleeper.completion);
+       dreq->revisit = cache_restart_thread;
+
+       ret = setup_deferral(dreq, item);
+       if (ret)
+               return ret;
+
+       if (wait_for_completion_interruptible_timeout(
+                   &sleeper.completion, req->thread_wait) <= 0) {
+               /* The completion wasn't completed, so we need
+                * to clean up
+                */
+               spin_lock(&cache_defer_lock);
+               if (!list_empty(&sleeper.handle.hash)) {
+                       __unhash_deferred_req(&sleeper.handle);
+                       spin_unlock(&cache_defer_lock);
+               } else {
+                       /* cache_revisit_request already removed
+                        * this from the hash table, but hasn't
+                        * called ->revisit yet.  It will very soon
+                        * and we need to wait for it.
                         */
-                       dreq = req->defer(req);
-                       goto retry;
+                       spin_unlock(&cache_defer_lock);
+                       wait_for_completion(&sleeper.completion);
                }
-               /* only return success if we actually deferred the
-                * request.  In this case we waited until it was
-                * answered so no deferral has happened - rather
-                * an answer already exists.
+       }
+       if (test_bit(CACHE_PENDING, &item->flags)) {
+               /* item is still pending, try request
+                * deferral
                 */
-               return -EEXIST;
+               return -ETIMEDOUT;
        }
-       return 0;
+       /* only return success if we actually deferred the
+        * request.  In this case we waited until it was
+        * answered so no deferral has happened - rather
+        * an answer already exists.
+        */
+       return -EEXIST;
+}
+
+static int cache_defer_req(struct cache_req *req, struct cache_head *item)
+{
+       struct cache_deferred_req *dreq;
+       int ret;
+
+       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 -ENOMEM;
+       }
+       if (req->thread_wait) {
+               ret = cache_wait_req(req, item);
+               if (ret != -ETIMEDOUT)
+                       return ret;
+       }
+       dreq = req->defer(req);
+       if (dreq == NULL)
+               return -ENOMEM;
+       return setup_deferral(dreq, item);
 }
 
 static void cache_revisit_request(struct cache_head *item)