From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756109AbaA2EDI (ORCPT ); Tue, 28 Jan 2014 23:03:08 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:56007 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756083AbaA2EDG (ORCPT ); Tue, 28 Jan 2014 23:03:06 -0500 Message-ID: <52E87D64.30800@huawei.com> Date: Wed, 29 Jan 2014 12:02:44 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Tejun Heo CC: , , Subject: Re: [PATCH 4/4] cgroup: move the one-off opts sanity check in cgroup_root_from_opts() to parse_cgroupfs_options() References: <1390923125-4369-1-git-send-email-tj@kernel.org> <1390923125-4369-5-git-send-email-tj@kernel.org> In-Reply-To: <1390923125-4369-5-git-send-email-tj@kernel.org> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.18.230] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/1/28 23:32, Tejun Heo wrote: > cgroup_root_from_opts() checks whether (!opts->subsys_mask && > !opts->none) and returns NULL if so. After that, if allocation fails, > returns ERR_PTR(-ENOMEM). The caller, cgroup_mount(), doesn't treat > NULL as an error but set opts.new_root to NULL; however, later on, > cgroup_set_super() fails with -EINVAL if new_root is NULL. This patch changes mount semantics. If cgroup_root_from_opts() returns NULL, it means we should be looking for existing superblock only. This will fail: # mount -t cgroup -o name=abc xxx /mnt But this is ok: # mount -t cgroup -o none,name=abc xxx /mnt # mkdir /mnt/sub # umount /mnt # mount -t cgroup -o name=abc xxx /mnt <-- this won't work with your patch > > This is one bizarre error handling sequence especially when all other > opts sanity checks including the very close (!opts->subsys_mask && > !opts->name) check are done in parse_cgroupfs_options(). > > Let's move the one-off check in cgroup_root_from_opts() to > parse_cgroupfs_options() where it can be combined with the > (!opts->subsys_mask && !opts->name) check. cgroup_root_from_opts() is > updated to return NULL on memory allocation failure. > > Signed-off-by: Tejun Heo