nfs_lock_request
if (!list_empty(&head->wb_list) || !nfs_lock_request(head))
nfs_lock_request(req);
nfs_lock_request(ret);
while (!nfs_lock_request(subreq)) {
while (!nfs_lock_request(head)) {
nfs_lock_request(req);
if (!nfs_lock_request(req)) {