SUNRPC: cleanup rpc credential cache garbage collection

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 73 insertions, 49 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 4d7c78b05d1e..00f9649b0901 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -25,6 +25,8 @@ static const struct rpc_authops *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
         NULL,                   /* others can be loadable modules */
 };
 
+static LIST_HEAD(cred_unused);
+
 static u32
 pseudoflavor_to_flavor(u32 flavor) {
         if (flavor >= RPC_AUTH_MAXFLAVOR)
@@ -134,13 +136,13 @@ rpcauth_init_credcache(struct rpc_auth *auth, unsigned long expire)
  * Destroy a list of credentials
  */
 static inline
-void rpcauth_destroy_credlist(struct hlist_head *head)
+void rpcauth_destroy_credlist(struct list_head *head)
 {
         struct rpc_cred *cred;
 
-        while (!hlist_empty(head)) {
-                cred = hlist_entry(head->first, struct rpc_cred, cr_hash);
-                hlist_del_init(&cred->cr_hash);
+        while (!list_empty(head)) {
+                cred = list_entry(head->next, struct rpc_cred, cr_lru);
+                list_del_init(&cred->cr_lru);
                 put_rpccred(cred);
         }
 }
@@ -152,17 +154,20 @@ void rpcauth_destroy_credlist(struct hlist_head *head)
 void
 rpcauth_clear_credcache(struct rpc_cred_cache *cache)
 {
-        HLIST_HEAD(free);
-        struct hlist_node *pos, *next;
+        LIST_HEAD(free);
+        struct hlist_head *head;
         struct rpc_cred *cred;
         int             i;
 
         spin_lock(&rpc_credcache_lock);
         for (i = 0; i < RPC_CREDCACHE_NR; i++) {
-                hlist_for_each_safe(pos, next, &cache->hashtable[i]) {
-                        cred = hlist_entry(pos, struct rpc_cred, cr_hash);
-                        __hlist_del(&cred->cr_hash);
-                        hlist_add_head(&cred->cr_hash, &free);
+                head = &cache->hashtable[i];
+                while (!hlist_empty(head)) {
+                        cred = hlist_entry(head->first, struct rpc_cred, cr_hash);
+                        get_rpccred(cred);
+                        list_move_tail(&cred->cr_lru, &free);
+                        smp_wmb();
+                        hlist_del_init(&cred->cr_hash);
                 }
         }
         spin_unlock(&rpc_credcache_lock);
@@ -184,38 +189,39 @@ rpcauth_destroy_credcache(struct rpc_auth *auth)
         }
 }
 
+/*
+ * Remove stale credentials. Avoid sleeping inside the loop.
+ */
 static void
-rpcauth_prune_expired(struct rpc_auth *auth, struct rpc_cred *cred, struct hlist_head *free)
+rpcauth_prune_expired(struct list_head *free)
 {
-        if (atomic_read(&cred->cr_count) != 1)
-               return;
-        if (time_after(jiffies, cred->cr_expire + auth->au_credcache->expire))
-                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
-        if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0) {
-                __hlist_del(&cred->cr_hash);
-                hlist_add_head(&cred->cr_hash, free);
+        struct rpc_cred *cred;
+
+        while (!list_empty(&cred_unused)) {
+                cred = list_entry(cred_unused.next, struct rpc_cred, cr_lru);
+                if (time_after(jiffies, cred->cr_expire +
+                                        cred->cr_auth->au_credcache->expire))
+                        break;
+                list_del_init(&cred->cr_lru);
+                if (atomic_read(&cred->cr_count) != 0)
+                        continue;
+                get_rpccred(cred);
+                list_add_tail(&cred->cr_lru, free);
+                smp_wmb();
+                hlist_del_init(&cred->cr_hash);
         }
 }
 
 /*
- * Remove stale credentials. Avoid sleeping inside the loop.
+ * Run garbage collector.
  */
 static void
-rpcauth_gc_credcache(struct rpc_auth *auth, struct hlist_head *free)
+rpcauth_gc_credcache(struct rpc_cred_cache *cache, struct list_head *free)
 {
-        struct rpc_cred_cache *cache = auth->au_credcache;
-        struct hlist_node *pos, *next;
-        struct rpc_cred *cred;
-        int             i;
-
-        dprintk("RPC:       gc'ing RPC credentials for auth %p\n", auth);
-        for (i = 0; i < RPC_CREDCACHE_NR; i++) {
-                hlist_for_each_safe(pos, next, &cache->hashtable[i]) {
-                        cred = hlist_entry(pos, struct rpc_cred, cr_hash);
-                        rpcauth_prune_expired(auth, cred, free);
-                }
-        }
+        if (time_before(jiffies, cache->nextgc))
+                return;
         cache->nextgc = jiffies + cache->expire;
+        rpcauth_prune_expired(free);
 }
 
 /*
@@ -225,39 +231,35 @@ struct rpc_cred *
 rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
                 int flags)
 {
+        LIST_HEAD(free);
         struct rpc_cred_cache *cache = auth->au_credcache;
-        HLIST_HEAD(free);
-        struct hlist_node *pos, *next;
+        struct hlist_node *pos;
         struct rpc_cred *new = NULL,
-                        *cred = NULL;
+                        *cred = NULL,
+                        *entry;
         int             nr = 0;
 
         if (!(flags & RPCAUTH_LOOKUP_ROOTCREDS))
                 nr = acred->uid & RPC_CREDCACHE_MASK;
 retry:
         spin_lock(&rpc_credcache_lock);
-        if (time_before(cache->nextgc, jiffies))
-                rpcauth_gc_credcache(auth, &free);
-        hlist_for_each_safe(pos, next, &cache->hashtable[nr]) {
-                struct rpc_cred *entry;
-                entry = hlist_entry(pos, struct rpc_cred, cr_hash);
-                if (entry->cr_ops->crmatch(acred, entry, flags)) {
-                        hlist_del(&entry->cr_hash);
-                        cred = entry;
-                        break;
-                }
-                rpcauth_prune_expired(auth, entry, &free);
+        hlist_for_each_entry(entry, pos, &cache->hashtable[nr], cr_hash) {
+                if (!entry->cr_ops->crmatch(acred, entry, flags))
+                        continue;
+                cred = get_rpccred(entry);
+                hlist_del(&entry->cr_hash);
+                break;
         }
         if (new) {
                 if (cred)
-                        hlist_add_head(&new->cr_hash, &free);
+                        list_add_tail(&new->cr_lru, &free);
                 else
                         cred = new;
         }
         if (cred) {
                 hlist_add_head(&cred->cr_hash, &cache->hashtable[nr]);
-                get_rpccred(cred);
         }
+        rpcauth_gc_credcache(cache, &free);
         spin_unlock(&rpc_credcache_lock);
 
         rpcauth_destroy_credlist(&free);
@@ -303,6 +305,7 @@ rpcauth_init_cred(struct rpc_cred *cred, const struct auth_cred *acred,
                   struct rpc_auth *auth, const struct rpc_credops *ops)
 {
         INIT_HLIST_NODE(&cred->cr_hash);
+        INIT_LIST_HEAD(&cred->cr_lru);
         atomic_set(&cred->cr_count, 1);
         cred->cr_auth = auth;
         cred->cr_ops = ops;
@@ -353,9 +356,29 @@ rpcauth_holdcred(struct rpc_task *task)
 void
 put_rpccred(struct rpc_cred *cred)
 {
-        cred->cr_expire = jiffies;
+        /* Fast path for unhashed credentials */
+        if (!hlist_unhashed(&cred->cr_hash))
+                goto need_lock;
+
         if (!atomic_dec_and_test(&cred->cr_count))
                 return;
+        goto out_destroy;
+
+need_lock:
+        if (!atomic_dec_and_lock(&cred->cr_count, &rpc_credcache_lock))
+                return;
+        if (!list_empty(&cred->cr_lru))
+                list_del_init(&cred->cr_lru);
+        if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
+                hlist_del(&cred->cr_hash);
+        else if (!hlist_unhashed(&cred->cr_hash)) {
+                cred->cr_expire = jiffies;
+                list_add_tail(&cred->cr_lru, &cred_unused);
+                spin_unlock(&rpc_credcache_lock);
+                return;
+        }
+        spin_unlock(&rpc_credcache_lock);
+out_destroy:
         cred->cr_ops->crdestroy(cred);
 }
 
diff --git a/net/sunrpc/auth_null.c b/net/sunrpc/auth_null.c
index 6c905fb11c5d..537d0e8589dd 100644
--- a/net/sunrpc/auth_null.c
+++ b/net/sunrpc/auth_null.c
@@ -133,6 +133,7 @@ const struct rpc_credops null_credops = {
 
 static
 struct rpc_cred null_cred = {
+        .cr_lru         = LIST_HEAD_INIT(null_cred.cr_lru),
         .cr_auth        = &null_auth,
         .cr_ops         = &null_credops,
         .cr_count       = ATOMIC_INIT(1),