From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Menage Subject: [PATCH] cgroup: Fix root_count when mount fails due to busy subsystem Date: Thu, 22 Jan 2009 16:48:41 -0800 Message-ID: <20090123004703.25103.29754.stgit@menage.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: akpm@linux-foundation.org, serue@us.ibm.com Cc: linux-kernel@vger.kernel.org, containers@lists.osdl.org List-Id: containers.vger.kernel.org cgroup: Fix root_count when mount fails due to busy subsystem root_count was being incremented in cgroup_get_sb() after all error checking was complete, but decremented in cgroup_kill_sb(), which can be called on a superblock that we gave up on due to an error. This patch changes cgroup_kill_sb() to only decrement root_count if the root was previously linked into the list of roots. Signed-off-by: Paul Menage --- I was actually surprised to find that list_del() doesn't crash when run on an unattached list_head structure. kernel/cgroup.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index adcd0bb..9ce27e8 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1115,8 +1115,10 @@ static void cgroup_kill_sb(struct super_block *sb) { } write_unlock(&css_set_lock); - list_del(&root->root_list); - root_count--; + if (!list_empty(&root->root_list)) { + list_del(&root->root_list); + root_count--; + } mutex_unlock(&cgroup_mutex);