From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f193.google.com ([209.85.210.193]:34246 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726210AbfACBAD (ORCPT ); Wed, 2 Jan 2019 20:00:03 -0500 Date: Wed, 2 Jan 2019 17:00:00 -0800 From: Andrei Vagin To: David Howells Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org, Li Zefan Subject: Re: [PATCH vfs/for-next v4] cgroup: fix top cgroup refcnt leak Message-ID: <20190103010000.GA32003@gmail.com> References: <20190102210659.3125-1-avagin@gmail.com> <20190102200223.GI2217@ZenIV.linux.org.uk> <8617.1546475183@warthog.procyon.org.uk> <20190103004339.GA20154@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <20190103004339.GA20154@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Jan 02, 2019 at 04:43:39PM -0800, Andrei Vagin wrote: > On Thu, Jan 03, 2019 at 12:26:23AM +0000, David Howells wrote: > > Andrei Vagin wrote: > > > > > It looks like the c6b3d5bcd67c ("cgroup: fix top cgroup refcnt leak") > > > commit was reverted by mistake. > > > > > > $ mkdir /tmp/cgroup > > > $ mkdir /tmp/cgroup2 > > > $ mount -t cgroup -o none,name=test test /tmp/cgroup > > > $ mount -t cgroup -o none,name=test test /tmp/cgroup2 > > > $ umount /tmp/cgroup > > > $ umount /tmp/cgroup2 > > > $ cat /proc/self/cgroup | grep test > > > 12:name=test:/ > > > > > > You can see the test cgroup was not freed. > > > > > > Cc: Li Zefan > > > Fixes: aea3f2676c83 ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context") > > > Signed-off-by: Andrei Vagin > > > --- > > > > > > v2: clean up code and add the vfs/for-next tag > > > v3: fix a reference leak when kernfs_node_dentry fails > > > v4: call deactivate_locked_super() in a error case > > > v5: don't dereference fc->root after dput() > > > > > > kernel/cgroup/cgroup.c | 25 ++++++++++++++++++------- > > > 1 file changed, 18 insertions(+), 7 deletions(-) > > > > This patch doesn't work either. > > I'm sorry, but we can't say anything about this patch now, because it > looks like recent changes in vfs-next break something else here... I found a reason why this patch doesn't work on Al's vfs/for-next: [avagin@laptop linux]$ git diff 40effd960becd8a355b7aafc789712afd64f5759..vfs/for-next kernel/cgroup/cgroup-v1.c | grep -B 5 -A 5 cgroup_get /* @@ -1280,8 +1285,8 @@ int cgroup1_get_tree(struct fs_context *fc) mutex_lock(&cgroup_mutex); percpu_ref_reinit(&root->cgrp.self.refcnt); mutex_unlock(&cgroup_mutex); + cgroup_get(&root->cgrp); } - cgroup_get(&root->cgrp); /* * If @pinned_sb, we're reusing an existing root and holding an 40effd960becd8a355b7aafc789712afd64f5759 is the previous head of vfs/for-next I reverted this hunk, applied my patch and all criu test passed. > > > > > percpu ref (css_release) <= 0 (0) after switching to atomic > > RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x90/0x1a0 > > > > Btw, note that the subject says "v4" but the changelog says "v5". > > It is v5. > > > > > David