Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752726AbaF0HKR (ORCPT ); Fri, 27 Jun 2014 03:10:17 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:24306 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756AbaF0HKP (ORCPT ); Fri, 27 Jun 2014 03:10:15 -0400 Message-ID: <53AD18D0.3090100@huawei.com> Date: Fri, 27 Jun 2014 15:10:08 +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: [PATCH v2 1/3] cgroup: fix mount failure in a corner case 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 # 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 /mnt busy mount: according to mtab, xxx is already mounted on /mnt 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 | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1c65f24..ae2b382 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 +1679,23 @@ 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))) + continue; + if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) { + mutex_unlock(&cgroup_mutex); + msleep(10); + ret = restart_syscall -- 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/