linux-kernel - Re: INFO: task hung in generic_file_write

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Message-ID: <e51a7822-3fdc-3f7a-25bd-5d8d8df44749@i-love.sakura.ne.jp>
Date:   Mon, 20 Aug 2018 23:12:10 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        syzbot <syzbot+9933e4476f365f5d5a1b@...kaller.appspotmail.com>,
        linux-mm@...ck.org, mgorman@...hsingularity.net,
        Michal Hocko <mhocko@...nel.org>, ak@...ux.intel.com,
        jlayton@...hat.com, linux-kernel@...r.kernel.org,
        mawilcox@...rosoft.com, syzkaller-bugs@...glegroups.com,
        tim.c.chen@...ux.intel.com,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: INFO: task hung in generic_file_write_iter

On 2018/08/06 20:56, Tetsuo Handa wrote:
> On 2018/08/06 19:09, Jan Kara wrote:
>> Looks like some kind of a race where device block size gets changed while
>> getblk() runs (and creates buffers for underlying page). I don't have time
>> to nail it down at this moment can have a look into it later unless someone
>> beats me to it.
>>
> 
> It seems that loop device is relevant to this problem.

Speak of loop device, I'm waiting for Jens for three months
http://lkml.kernel.org/r/1527297408-4428-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
but Jens is too busy to come up with an alternative. Since that is a big patch, I wish we can
start testing that patch before Jan starts writing a patch for fixing getblk() race problem.