linux-ext4 - Re: INFO: task hung in blk_queue

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Message-Id: <0B5A5D8D-BA17-45C2-BCF7-609CDCF1A8DB@kernel.dk>
Date:   Sat, 2 Jun 2018 07:48:26 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Bart.VanAssche@....com, dvyukov@...gle.com,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        jthumshirn@...e.de, alan.christopher.jenkins@...il.com,
        syzbot+c4f9cebf9d651f6e54de@...kaller.appspotmail.com,
        martin.petersen@...cle.com, dan.j.williams@...el.com, hch@....de,
        oleksandr@...alenko.name, martin@...htvoll.de, hare@...e.com,
        syzkaller-bugs@...glegroups.com, ross.zwisler@...ux.intel.com,
        keith.busch@...el.com, linux-ext4@...r.kernel.org
Subject: Re: INFO: task hung in blk_queue_enter


> On Jun 1, 2018, at 10:54 PM, Ming Lei <ming.lei@...hat.com> wrote:
> 
>> On Fri, Jun 01, 2018 at 10:31:13PM -0600, Jens Axboe wrote:
>> On 6/1/18 8:36 PM, Ming Lei wrote:
>>>> clear the bit when we need to, potentially even adding a debug check to
>>>> blk_queue_enter_live() that complains if the ref was not already
>>>> elevated. Though that would be expensive, compared to the percpu inc
>>>> now. Not saying the bit is necessarily the best way forward, but I do
>>>> like it a LOT more than adding an argument to generic_make_request.
>>> 
>>> We may introduce generic_make_request_with_ref() for blk_queue_split(),
>>> what do you think of the following patch?
>> 
>> Functionally it'll work as well.
> 
> If you are fine with this one, I'm glad to prepare for a normal one,
> so that we can save one precious bio flag, and the total number is
> just 13.

We’ve never had much issue with bio specific flags, I prefer that approach to a wrapper around generic_make_request().