NFSv4: Allow attribute caching with 'noac' mounts if client holds a delegation

If the server has given us a delegation on a file, we _know_ that we can
cache the attribute information even when the user has specified 'noac'.

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 8d965bd..cac96bc 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -161,14 +161,17 @@
 	struct nfs_server *server = NFS_SERVER(inode);
 	struct nfs_inode *nfsi = NFS_I(inode);
 
-	if (server->flags & NFS_MOUNT_NOAC)
-		goto force_reval;
+	if (nfs_have_delegated_attributes(inode))
+		goto out_noreval;
+
 	if (filp->f_flags & O_DIRECT)
 		goto force_reval;
-	if (nfsi->npages != 0)
-		return 0;
-	if (!(nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE) && !nfs_attribute_timeout(inode))
-		return 0;
+	if (nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
+		goto force_reval;
+	if (nfs_attribute_timeout(inode))
+		goto force_reval;
+out_noreval:
+	return 0;
 force_reval:
 	return __nfs_revalidate_inode(server, inode);
 }