From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f172.google.com (mail-we0-f172.google.com [74.125.82.172]) by kanga.kvack.org (Postfix) with ESMTP id BD88E6B0070 for ; Thu, 22 Jan 2015 10:19:52 -0500 (EST) Received: by mail-we0-f172.google.com with SMTP id k11so2361690wes.3 for ; Thu, 22 Jan 2015 07:19:52 -0800 (PST) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id cj10si5170189wid.85.2015.01.22.07.19.50 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 22 Jan 2015 07:19:51 -0800 (PST) Date: Thu, 22 Jan 2015 10:19:43 -0500 From: Johannes Weiner Subject: Re: [Regression] 3.19-rc3 : memcg: Hang in mount memcg Message-ID: <20150122151943.GA27368@phnom.home.cmpxchg.org> References: <54B01335.4060901@arm.com> <20150110085525.GD2110@esperanza> <54BCFDCF.9090603@arm.com> <20150121163955.GM4549@arm.com> <20150122134550.GA13876@phnom.home.cmpxchg.org> <20150122143454.GA4507@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150122143454.GA4507@htj.dyndns.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Will Deacon , "Suzuki K. Poulose" , Vladimir Davydov , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "mhocko@suse.cz" , "akpm@linux-foundation.org" Hi, On Thu, Jan 22, 2015 at 09:34:54AM -0500, Tejun Heo wrote: > On Thu, Jan 22, 2015 at 08:45:50AM -0500, Johannes Weiner wrote: > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > > index bb263d0caab3..9a09308c8066 100644 > > --- a/kernel/cgroup.c > > +++ b/kernel/cgroup.c > > @@ -1819,8 +1819,11 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, > > goto out_unlock; > > } > > > > - if (root->flags ^ opts.flags) > > - pr_warn("new mount options do not match the existing superblock, will be ignored\n"); > > + if (root->flags ^ opts.flags) { > > + pr_warn("new mount options do not match the existing superblock\n"); > > + ret = -EBUSY; > > + goto out_unlock; > > + } > > Do we really need the above chunk? Inform and ignore or fail hard? I guess we can drop this hunk and keep with the current behavior. > > @@ -1909,7 +1912,7 @@ static void cgroup_kill_sb(struct super_block *sb) > > * > > * And don't kill the default root. > > */ > > - if (css_has_online_children(&root->cgrp.self) || > > + if (!list_empty(&root->cgrp.self.children) || > > root == &cgrp_dfl_root) > > cgroup_put(&root->cgrp); > > I tried to do something a bit more advanced so that eventual async > release of dying children, if they happen, can also release the > hierarchy but I don't think it really matters unless we can forcefully > drain. So, shouldn't just the above part be enough? Yep, I'd be fine with that. ---