From: Tejun Heo Subject: Re: [PATCH cgroup/for-4.3-fixes] cgroup, writeback: don't enable cgroup writeback on traditional hierarchies Date: Thu, 24 Sep 2015 16:48:06 -0400 Message-ID: <20150924204806.GH25415@mtj.duckdns.org> References: <1434495193-31182-1-git-send-email-tj@kernel.org> <1434495193-31182-3-git-send-email-tj@kernel.org> <20150722035620.GD2944@thunk.org> <1443012552.19983.209.camel@gmail.com> <20150923180934.GE26647@mtj.duckdns.org> <20150923185137.GJ26647@mtj.duckdns.org> <20150923210729.GA23180@mtj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Ts'o , axboe@kernel.dk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, lizefan@huawei.com, cgroups@vger.kernel.org, hannes@cmpxchg.org, kernel-team@fb.com, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, Dexuan Cui To: Artem Bityutskiy Return-path: Content-Disposition: inline In-Reply-To: <20150923210729.GA23180@mtj.duckdns.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed, Sep 23, 2015 at 05:07:29PM -0400, Tejun Heo wrote: > inode_cgwb_enabled() gates cgroup writeback support. If it returns > true, each inode is attached to the corresponding memory domain which > gets mapped to io domain. It currently only tests whether the > filesystem and bdi support cgroup writeback; however, cgroup writeback > support doesn't work on traditional hierarchies and thus it should > also test whether memcg and iocg are on the default hierarchy. > > This caused traditional hierarchy setups to hit the cgroup writeback > path inadvertently and ended up creating separate writeback domains > for each memcg and mapping them all to the root iocg uncovering a > couple issues in the cgroup writeback path. > > cgroup writeback was never meant to be enabled on traditional > hierarchies. Make inode_cgwb_enabled() test whether both memcg and > iocg are on the default hierarchy. > > Signed-off-by: Tejun Heo > Reported-by: Artem Bityutskiy > Reported-by: Dexuan Cui > Link: http://lkml.kernel.org/g/1443012552.19983.209.camel@gmail.com > Link: http://lkml.kernel.org/g/f30d4a6aa8a546ff88f73021d026a453@SIXPR30MB031.064d.mgd.msft.net Applying to cgroup/for-4.3-fixes. Thanks. -- tejun