2 files changed, 42 insertions, 2 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 2bfbde0f7176..1b5f38f48dab 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2079,7 +2079,7 @@ MODULE_PARM_DESC(nfs_access_max_cachesize, "NFS access maximum total cache lengt
 static void nfs_access_free_entry(struct nfs_access_entry *entry)
 {
         put_rpccred(entry->cred);
-        kfree(entry);
+        kfree_rcu(entry, rcu_head);
         smp_mb__before_atomic();
         atomic_long_dec(&nfs_access_nr_entries);
         smp_mb__after_atomic();
@@ -2257,6 +2257,38 @@ out_zap:
         return -ENOENT;
 }
 
+static int nfs_access_get_cached_rcu(struct inode *inode, struct rpc_cred *cred, struct nfs_access_entry *res)
+{
+        /* Only check the most recently returned cache entry,
+         * but do it without locking.
+         */
+        struct nfs_inode *nfsi = NFS_I(inode);
+        struct nfs_access_entry *cache;
+        int err = -ECHILD;
+        struct list_head *lh;
+
+        rcu_read_lock();
+        if (nfsi->cache_validity & NFS_INO_INVALID_ACCESS)
+                goto out;
+        lh = rcu_dereference(nfsi->access_cache_entry_lru.prev);
+        cache = list_entry(lh, struct nfs_access_entry, lru);
+        if (lh == &nfsi->access_cache_entry_lru ||
+            cred != cache->cred)
+                cache = NULL;
+        if (cache == NULL)
+                goto out;
+        if (!nfs_have_delegated_attributes(inode) &&
+            !time_in_range_open(jiffies, cache->jiffies, cache->jiffies + nfsi->attrtimeo))
+                goto out;
+        res->jiffies = cache->jiffies;
+        res->cred = cache->cred;
+        res->mask = cache->mask;
+        err = 0;
+out:
+        rcu_read_unlock();
+        return err;
+}
+
 static void nfs_access_add_rbtree(struct inode *inode, struct nfs_access_entry *set)
 {
         struct nfs_inode *nfsi = NFS_I(inode);
@@ -2300,6 +2332,11 @@ void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set)
         cache->cred = get_rpccred(set->cred);
         cache->mask = set->mask;
 
+        /* The above field assignments must be visible
+         * before this item appears on the lru.  We cannot easily
+         * use rcu_assign_pointer, so just force the memory barrier.
+         */
+        smp_wmb();
         nfs_access_add_rbtree(inode, cache);
 
         /* Update accounting */
@@ -2339,7 +2376,9 @@ static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)
 
         trace_nfs_access_enter(inode);
 
-        status = nfs_access_get_cached(inode, cred, &cache);
+        status = nfs_access_get_cached_rcu(inode, cred, &cache);
+        if (status != 0)
+                status = nfs_access_get_cached(inode, cred, &cache);
         if (status == 0)
                 goto out_cached;
 
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 60cd9e377926..5180a7ededec 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -52,6 +52,7 @@ struct nfs_access_entry {
         unsigned long           jiffies;
         struct rpc_cred *       cred;
         int                     mask;
+        struct rcu_head         rcu_head;
 };
 
 struct nfs_lockowner {