From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: [PATCH] cgroup: Fix root_count when mount fails due to busy subsystem Date: Thu, 22 Jan 2009 20:20:14 -0600 Message-ID: <20090123022014.GB9267@us.ibm.com> References: <20090123004703.25103.29754.stgit@menage.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20090123004703.25103.29754.stgit@menage.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org To: Paul Menage Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, containers@lists.osdl.org List-Id: containers.vger.kernel.org Quoting Paul Menage (menage@google.com): > 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 Tested-by: Serge Hallyn thanks, -serge > > --- > > 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); >