Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
Sender: Tejun Heo <htejun@gmail.com>
Date:   Tue, 17 Oct 2023 22:43:53 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Jingbo Xu <jefflexu@linux.alibaba.com>
Cc:     guro@fb.com, lizefan.x@bytedance.com, hannes@cmpxchg.org,
        cgroups@vger.kernel.org, jack@suse.cz,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org,
        joseph.qi@linux.alibaba.com
Subject: Re: [PATCH v2] writeback, cgroup: switch inodes with dirty
 timestamps to release dying cgwbs
Message-ID: <ZS-aydAgB5SIkHyk@slm.duckdns.org>
References: <20231013055208.15457-1-jefflexu@linux.alibaba.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20231013055208.15457-1-jefflexu@linux.alibaba.com>
Precedence: bulk

On Fri, Oct 13, 2023 at 01:52:08PM +0800, Jingbo Xu wrote:
> The cgwb cleanup routine will try to release the dying cgwb by switching
> the attached inodes.  It fetches the attached inodes from wb->b_attached
> list, omitting the fact that inodes only with dirty timestamps reside in
> wb->b_dirty_time list, which is the case when lazytime is enabled.  This
> causes enormous zombie memory cgroup when lazytime is enabled, as inodes
> with dirty timestamps can not be switched to a live cgwb for a long time.
> 
> It is reasonable not to switch cgwb for inodes with dirty data, as
> otherwise it may break the bandwidth restrictions.  However since the
> writeback of inode metadata is not accounted for, let's also switch
> inodes with dirty timestamps to avoid zombie memory and block cgroups
> when laztytime is enabled.
> 
> Fixs: c22d70a162d3 ("writeback, cgroup: release dying cgwbs by switching attached inodes")
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun