NFS: Fix an Oops in the nfs_access_cache_shrinker()

The nfs_access_cache_shrinker may race with nfs_access_zap_cache().
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

@@ -1743,8 +1743,8 @@ int nfs_access_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
 	struct nfs_inode *nfsi;
 	struct nfs_access_entry *cache;
 
-	spin_lock(&nfs_access_lru_lock);
 restart:
+	spin_lock(&nfs_access_lru_lock);
 	list_for_each_entry(nfsi, &nfs_access_lru_list, access_cache_inode_lru) {
 		struct inode *inode;
 
@@ -1769,6 +1769,7 @@ remove_lru_entry:
 			clear_bit(NFS_INO_ACL_LRU_SET, &nfsi->flags);
 		}
 		spin_unlock(&inode->i_lock);
+		spin_unlock(&nfs_access_lru_lock);
 		iput(inode);
 		goto restart;
 	}