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>

1 files changed, 79 insertions, 64 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 18e5e8e6f622..da872f9fe1e0 100644
--- 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)