Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753463AbaF0IRj (ORCPT ); Fri, 27 Jun 2014 04:17:39 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:28290 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753152AbaF0IRg (ORCPT ); Fri, 27 Jun 2014 04:17:36 -0400 Message-ID: <53AD2852.2060304@huawei.com> Date: Fri, 27 Jun 2014 16:16:18 +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: LKML , Cgroups Subject: Re: [PATCH v2 1/3] cgroup: fix mount failure in a corner case References: <53AD18D0.3090100@huawei.com> In-Reply-To: <53AD18D0.3090100@huawei.com> 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 Oh sorry the cut&paste was incomplete. Here's the complete one: ================ From: Li Zefan Date: Thu, 12 Jun 2014 09:11:00 +0800 Subject: [PATCH v2 1/3] cgroup: fix mount failure in a corner case # cat test.sh #! /bin/bash mount -t cgroup -o cpu xxx /cgroup umount /cgroup mount -t cgroup -o cpu,cpuacct xxx /cgroup umount /cgroup # ./test.sh mount: xxx already mounted or /cgroup busy mount: according to mtab, xxx is already mounted on /cgroup It's because the cgroupfs_root of the first mount was under destruction asynchronously. Fix this by delaying and then retrying mount for this case. v2: - use percpu_ref_tryget_live() rather that introducing percpu_ref_alive(). (Tejun) - adjust comment. Signed-off-by: Li Zefan --- kernel/cgroup.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1c65f24..6826227 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1648,10 +1648,12 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, int flags, const char *unused_dev_name, void *data) { + struct cgroup_subsys *ss; struct cgroup_root *root; struct cgroup_sb_opts opts; struct dentry *dentry; int ret; + int i, j = -1; bool new_sb; /* @@ -1677,6 +1679,25 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, goto out_unlock; } + /* + * Destruction of cgroup root is asynchronous, so we may fail to + * mount a cgroupfs if it immediately follows a umount. Let's wait + * a little bit and retry. + */ + for_each_subsys(ss, i) { + if (!(opts.subsys_mask & (1 << i)) || + ss->root === &cgrp_dfl_root) + continue; + + if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) { + mutex_unlock(&cgroup_mutex); + msleep(10); + ret = restart_syscall(); + goto out_free; + } + j = i; + } + for_each_root(root) { bool name_match = false; @@ -1763,6 +1784,14 @@ out_free: kfree(opts.release_agent); kfree(opts.name); + for_each_subsys(ss, i) { + if (i > j) + break; + if (!(opts.subsys_mask & (1 << i))) + continue; + cgroup_put(&ss->root->cgrp); + } + if (ret) return ERR_PTR(ret); -- 1.8.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/