From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752805Ab1JHMR3 (ORCPT ); Sat, 8 Oct 2011 08:17:29 -0400 Received: from gateway.alibaba-inc.com ([121.0.29.128]:47375 "EHLO CNHZ-ExGW-01.ali.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751802Ab1JHMR1 convert rfc822-to-8bit (ORCPT ); Sat, 8 Oct 2011 08:17:27 -0400 X-Greylist: delayed 901 seconds by postgrey-1.27 at vger.kernel.org; Sat, 08 Oct 2011 08:17:27 EDT X-AuditID: 0a14034b-b7c6fae000005392-f4-4e903bd1e163 Subject: cgroup umount bug From: =?UTF-8?Q?=E5=90=AB=E9=BB=9B?= Reply-To: To: CC: , Content-Type: text/plain; charset="UTF-8" Organization: taobao Date: Sat, 8 Oct 2011 20:02:24 +0800 Message-ID: <1318075344.2168.4.camel@handai-OptiPlex-780> MIME-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 8BIT X-Originating-IP: [10.20.8.3] X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I found a mount/umount problem while using cgroup: I mount a cpu cgroup (or other subsystems) and create some subgroups under it, but later I try to umount it without rmdir those subgroups. I find that I can umount it without any errors but actually the super block still exist. This is because the sb->s_active count is greater than 1 which was added by cgroup_create. But later if I want to mount both cpu and memory subsystems, it will be unsuccessful indicating that the device(cpu subsystem) is busy. This situation will not happen if I rmdir the subgroups manually before umount it. So my question is: Should the umount return success when there are still some subgroups exist ? If this is okay, then it may lead to some *strange* errors using cgroup later. If it can not be umount, then it should inform that the mount point is still busy. Following is an example of this problem: mount -t cgroup -o cpu cgroup /mnt mkdir /mnt/test …..// do some tests umount /mnt /* return successfully */ /* do other subsystems test */ mount -cgroup -o cpu,cpuset cgroup /mnt mount: cgroup already mounted or /mnt busy /*??? which is strange */ Looking forward to your reply. Thanks. ________________________________ This email (including any attachments) is confidential and may be legally privileged. If you received this email in error, please delete it immediately and do not copy it or use it for any purpose or disclose its contents to any other person. Thank you. 本电邮(包括任何附件)可能含有机密资料并受法律保护。如您不是正确的收件人，请您立即删除本邮件。请不要将本电邮进行复制并用作任何其他用途、或透露本邮件之内容。谢谢。