SUNRPC: Convert the credcache lookup code to use RCU

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

1 files changed, 57 insertions, 34 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 00f9649b0901..ad7bde2c437e 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -112,6 +112,14 @@ rpcauth_release(struct rpc_auth *auth)
 
 static DEFINE_SPINLOCK(rpc_credcache_lock);
 
+static void
+rpcauth_unhash_cred_locked(struct rpc_cred *cred)
+{
+        hlist_del_rcu(&cred->cr_hash);
+        smp_mb__before_clear_bit();
+        clear_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
+}
+
 /*
  * Initialize RPC credential cache
  */
@@ -166,8 +174,7 @@ rpcauth_clear_credcache(struct rpc_cred_cache *cache)
                         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);
+                        rpcauth_unhash_cred_locked(cred);
                 }
         }
         spin_unlock(&rpc_credcache_lock);
@@ -207,8 +214,7 @@ rpcauth_prune_expired(struct list_head *free)
                         continue;
                 get_rpccred(cred);
                 list_add_tail(&cred->cr_lru, free);
-                smp_wmb();
-                hlist_del_init(&cred->cr_hash);
+                rpcauth_unhash_cred_locked(cred);
         }
 }
 
@@ -218,10 +224,12 @@ rpcauth_prune_expired(struct list_head *free)
 static void
 rpcauth_gc_credcache(struct rpc_cred_cache *cache, struct list_head *free)
 {
-        if (time_before(jiffies, cache->nextgc))
+        if (list_empty(&cred_unused) || time_before(jiffies, cache->nextgc))
                 return;
+        spin_lock(&rpc_credcache_lock);
         cache->nextgc = jiffies + cache->expire;
         rpcauth_prune_expired(free);
+        spin_unlock(&rpc_credcache_lock);
 }
 
 /*
@@ -234,42 +242,57 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
         LIST_HEAD(free);
         struct rpc_cred_cache *cache = auth->au_credcache;
         struct hlist_node *pos;
-        struct rpc_cred *new = NULL,
-                        *cred = NULL,
-                        *entry;
+        struct rpc_cred *cred = NULL,
+                        *entry, *new;
         int             nr = 0;
 
         if (!(flags & RPCAUTH_LOOKUP_ROOTCREDS))
                 nr = acred->uid & RPC_CREDCACHE_MASK;
-retry:
-        spin_lock(&rpc_credcache_lock);
-        hlist_for_each_entry(entry, pos, &cache->hashtable[nr], cr_hash) {
+
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(entry, pos, &cache->hashtable[nr], cr_hash) {
                 if (!entry->cr_ops->crmatch(acred, entry, flags))
                         continue;
+                spin_lock(&rpc_credcache_lock);
+                if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) == 0) {
+                        spin_unlock(&rpc_credcache_lock);
+                        continue;
+                }
                 cred = get_rpccred(entry);
-                hlist_del(&entry->cr_hash);
+                spin_unlock(&rpc_credcache_lock);
                 break;
         }
-        if (new) {
-                if (cred)
-                        list_add_tail(&new->cr_lru, &free);
-                else
-                        cred = new;
-        }
-        if (cred) {
-                hlist_add_head(&cred->cr_hash, &cache->hashtable[nr]);
+        rcu_read_unlock();
+
+        if (cred != NULL) {
+                rpcauth_gc_credcache(cache, &free);
+                goto found;
         }
-        rpcauth_gc_credcache(cache, &free);
-        spin_unlock(&rpc_credcache_lock);
 
-        rpcauth_destroy_credlist(&free);
+        new = auth->au_ops->crcreate(auth, acred, flags);
+        if (IS_ERR(new)) {
+                cred = new;
+                goto out;
+        }
 
-        if (!cred) {
-                new = auth->au_ops->crcreate(auth, acred, flags);
-                if (!IS_ERR(new))
-                        goto retry;
+        spin_lock(&rpc_credcache_lock);
+        hlist_for_each_entry(entry, pos, &cache->hashtable[nr], cr_hash) {
+                if (!entry->cr_ops->crmatch(acred, entry, flags))
+                        continue;
+                cred = get_rpccred(entry);
+                break;
+        }
+        if (cred == NULL) {
                 cred = new;
-        } else if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags)
+                set_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
+                hlist_add_head_rcu(&cred->cr_hash, &cache->hashtable[nr]);
+        } else
+                list_add_tail(&new->cr_lru, &free);
+        rpcauth_prune_expired(&free);
+        cache->nextgc = jiffies + cache->expire;
+        spin_unlock(&rpc_credcache_lock);
+found:
+        if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags)
                         && cred->cr_ops->cr_init != NULL
                         && !(flags & RPCAUTH_LOOKUP_NEW)) {
                 int res = cred->cr_ops->cr_init(auth, cred);
@@ -278,8 +301,9 @@ retry:
                         cred = ERR_PTR(res);
                 }
         }
-
-        return (struct rpc_cred *) cred;
+        rpcauth_destroy_credlist(&free);
+out:
+        return cred;
 }
 
 struct rpc_cred *
@@ -357,21 +381,20 @@ void
 put_rpccred(struct rpc_cred *cred)
 {
         /* Fast path for unhashed credentials */
-        if (!hlist_unhashed(&cred->cr_hash))
+        if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0)
                 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)) {
+                rpcauth_unhash_cred_locked(cred);
+        else if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0) {
                 cred->cr_expire = jiffies;
                 list_add_tail(&cred->cr_lru, &cred_unused);
                 spin_unlock(&rpc_credcache_lock);