linux-kernel - Re: bio linked list corruption.

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Message-ID: <2951bc27-2453-203a-009d-260bccf2d038@fb.com>
Date:   Wed, 26 Oct 2016 17:21:22 -0600
From:   Jens Axboe <axboe@...com>
To:     Chris Mason <clm@...com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Jones <davej@...emonkey.org.uk>,
        Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Josef Bacik" <jbacik@...com>, David Sterba <dsterba@...e.com>,
        linux-btrfs <linux-btrfs@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Dave Chinner <david@...morbit.com>
Subject: Re: bio linked list corruption.

On 10/26/2016 05:19 PM, Chris Mason wrote:
> On Wed, Oct 26, 2016 at 05:03:45PM -0600, Jens Axboe wrote:
>> On 10/26/2016 04:58 PM, Linus Torvalds wrote:
>>> On Wed, Oct 26, 2016 at 3:51 PM, Linus Torvalds
>>> <torvalds@...ux-foundation.org> wrote:
>>>>
>>>> Dave: it might be a good idea to split that "WARN_ON_ONCE()" in
>>>> blk_mq_merge_queue_io() into two
>>>
>>> I did that myself too, since Dave sees this during boot.
>>>
>>> But I'm not getting the warning ;(
>>>
>>> Dave gets it with ext4, and thats' what I have too, so I'm not sure
>>> what the required trigger would be.
>>
>> Actually, I think I see what might trigger it. You are on nvme, iirc,
>> and that has a deep queue. Dave, are you testing on a sata drive or
>> something similar with a shallower queue depth? If we end up sleeping
>> for a request, I think we could trigger data->ctx being different.
>>
>> Dave, can you hit the warnings with this? Totally untested...
>
> Confirmed, totally untested ;)  Don't try this one at home folks
> (working this out with Jens offlist)

Ahem, I did say untested! The one I just sent in reply to Linus should
be better. Though that one is completely untested as well...

-- 
Jens Axboe