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Sender: Tejun Heo <htejun@gmail.com>
Date:   Tue, 17 Oct 2023 22:44:18 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Jingbo Xu <jefflexu@linux.alibaba.com>
Cc:     guro@fb.com, jack@suse.cz, lizefan.x@bytedance.com,
        hannes@cmpxchg.org, cgroups@vger.kernel.org,
        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 v3] writeback, cgroup: switch inodes with dirty
 timestamps to release dying cgwbs
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References: <20231014125511.102978-1-jefflexu@linux.alibaba.com>
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On Sat, Oct 14, 2023 at 08:55:11PM +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.
> 
> Fixes: c22d70a162d3 ("writeback, cgroup: release dying cgwbs by switching attached inodes")
> Reviewed-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>

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

Thanks.

-- 
tejun