sunrpc/cache: change deferred-request hash table to use hlist.

Being a hash table, hlist is the best option.

There is currently some ugliness were we treat "->next == NULL" as
a special case to avoid having to initialise the whole array.
This change nicely gets rid of that case.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 11 insertions, 19 deletions

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 52a7d7224e90..03496357f455 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -133,7 +133,7 @@ struct cache_req {
  * delayed awaiting cache-fill
  */
 struct cache_deferred_req {
-        struct list_head        hash;   /* on hash chain */
+        struct hlist_node       hash;   /* on hash chain */
         struct list_head        recent; /* on fifo */
         struct cache_head       *item;  /* cache item we wait on */
         void                    *owner; /* we might need to discard all defered requests
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index ca7c621cd975..2a8405194056 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -506,13 +506,13 @@ EXPORT_SYMBOL_GPL(cache_purge);
 
 static DEFINE_SPINLOCK(cache_defer_lock);
 static LIST_HEAD(cache_defer_list);
-static struct list_head cache_defer_hash[DFR_HASHSIZE];
+static struct hlist_head cache_defer_hash[DFR_HASHSIZE];
 static int cache_defer_cnt;
 
 static void __unhash_deferred_req(struct cache_deferred_req *dreq)
 {
         list_del_init(&dreq->recent);
-        list_del_init(&dreq->hash);
+        hlist_del_init(&dreq->hash);
         cache_defer_cnt--;
 }
 
@@ -521,9 +521,7 @@ static void __hash_deferred_req(struct cache_deferred_req *dreq, struct cache_he
         int hash = DFR_HASH(item);
 
         list_add(&dreq->recent, &cache_defer_list);
-        if (cache_defer_hash[hash].next == NULL)
-                INIT_LIST_HEAD(&cache_defer_hash[hash]);
-        list_add(&dreq->hash, &cache_defer_hash[hash]);
+        hlist_add_head(&dreq->hash, &cache_defer_hash[hash]);
 }
 
 static int setup_deferral(struct cache_deferred_req *dreq, struct cache_head *item)
@@ -588,7 +586,7 @@ static int cache_wait_req(struct cache_req *req, struct cache_head *item)
                  * to clean up
                  */
                 spin_lock(&cache_defer_lock);
-                if (!list_empty(&sleeper.handle.hash)) {
+                if (!hlist_unhashed(&sleeper.handle.hash)) {
                         __unhash_deferred_req(&sleeper.handle);
                         spin_unlock(&cache_defer_lock);
                 } else {
@@ -642,24 +640,18 @@ static void cache_revisit_request(struct cache_head *item)
 {
         struct cache_deferred_req *dreq;
         struct list_head pending;
-
-        struct list_head *lp;
+        struct hlist_node *lp, *tmp;
         int hash = DFR_HASH(item);
 
         INIT_LIST_HEAD(&pending);
         spin_lock(&cache_defer_lock);
 
-        lp = cache_defer_hash[hash].next;
-        if (lp) {
-                while (lp != &cache_defer_hash[hash]) {
-                        dreq = list_entry(lp, struct cache_deferred_req, hash);
-                        lp = lp->next;
-                        if (dreq->item == item) {
-                                __unhash_deferred_req(dreq);
-                                list_add(&dreq->recent, &pending);
-                        }
+        hlist_for_each_entry_safe(dreq, lp, tmp, &cache_defer_hash[hash], hash)
+                if (dreq->item == item) {
+                        __unhash_deferred_req(dreq);
+                        list_add(&dreq->recent, &pending);
                 }
-        }
+
         spin_unlock(&cache_defer_lock);
 
         while (!list_empty(&pending)) {