From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755700AbcHVSbr (ORCPT ); Mon, 22 Aug 2016 14:31:47 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:28191 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752984AbcHVSbp (ORCPT ); Mon, 22 Aug 2016 14:31:45 -0400 Date: Mon, 22 Aug 2016 21:31:40 +0300 From: Dan Carpenter To: "Michael S. Tsirkin" Cc: Jonathan Corbet , linux-kernel@vger.kernel.org, Julia Lawall , Jason Wang , linux-doc@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH] CodingStyle: add some more error handling guidelines Message-ID: <20160822183140.GE4129@mwanda> References: <1471874251-7721-1-git-send-email-mst@redhat.com> <20160822081617.386db8cd@lwn.net> <20160822174355-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160822174355-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org vhost_dev_set_owner() is an example of why come-from labels are bad style. devel/drivers/vhost/vhost.c 473 /* Caller should have device mutex */ 474 long vhost_dev_set_owner(struct vhost_dev *dev) 475 { 476 struct task_struct *worker; 477 int err; 478 479 /* Is there an owner already? */ 480 if (vhost_dev_has_owner(dev)) { 481 err = -EBUSY; 482 goto err_mm; What does goto err_mm do? It's actually a do-nothing goto. It would be easier to read as a direct return. Why is it called err_mm? Because originally the condition was: if (dev->mm) { err = -EBUSY; goto err_mm; } We've changed the code but didn't update the label so it's slightly confusing unless you know how vhost_dev_has_owner() is implemented. 483 } 484 485 /* No owner, become one */ 486 dev->mm = get_task_mm(current); 487 worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid); 488 if (IS_ERR(worker)) { 489 err = PTR_ERR(worker); 490 goto err_worker; 491 } 492 493 dev->worker = worker; 494 wake_up_process(worker); /* avoid contributing to loadavg */ 495 496 err = vhost_attach_cgroups(dev); 497 if (err) 498 goto err_cgroup; 499 500 err = vhost_dev_alloc_iovecs(dev); 501 if (err) 502 goto err_cgroup; This name doesn't make sense because it's a come-from label which is used twice. Some people do: if (err) goto err_iovecs; 503 504 return 0; Then they add two labels here: err_iovecs: err_cgroup: kthread_stop(worker); But if you base the label name on the label location then it makes sense. goto stop_kthread; goto err_mmput;. 505 err_cgroup: 506 kthread_stop(worker); 507 dev->worker = NULL; 508 err_worker: 509 if (dev->mm) 510 mmput(dev->mm); 511 dev->mm = NULL; 512 err_mm: 513 return err; 514 } regards, dan carpenter