NFS: Lockless DNS lookups

Enable RCU protected lookup in the legacy DNS resolver.

Signed-off-by: Trond Myklebust <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfs/dns_resolve.c

···
 
 	struct sockaddr_storage addr;
 	size_t addrlen;
+	struct rcu_head rcu_head;
 };
 
 
···
 	}
 }
 
+static void nfs_dns_ent_free_rcu(struct rcu_head *head)
+{
+	struct nfs_dns_ent *item;
+
+	item = container_of(head, struct nfs_dns_ent, rcu_head);
+	kfree(item->hostname);
+	kfree(item);
+}
+
 static void nfs_dns_ent_put(struct kref *ref)
 {
 	struct nfs_dns_ent *item;
 
 	item = container_of(ref, struct nfs_dns_ent, h.ref);
-	kfree(item->hostname);
-	kfree(item);
+	call_rcu(item, nfs_dns_ent_free_rcu);
 }
 
 static struct cache_head *nfs_dns_ent_alloc(void)
···
 {
 	struct cache_head *ch;
 
-	ch = sunrpc_cache_lookup(cd,
+	ch = sunrpc_cache_lookup_rcu(cd,
 			&key->h,
 			nfs_dns_hash(key));
 	if (!ch)