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

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Message-ID: <6992049.xPdnW5VfcJ@merkaba>
Date:   Sat, 02 Jun 2018 10:07:26 +0200
From:   Martin Steigerwald <martin@...htvoll.de>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        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, 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

Ming Lei - 02.06.18, 06:54:
> 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.
[…]

I am completely lost about what you are talking about.

That is fine with me, but in case there is anything to test… let me 
know. I do not promise quick responses tough, as I have been quite a bit 
overwhelmed with stuff lately.

Currently I run 4.17-rc7 without any blk-mq related patches and it 
appears to be free of hangs or stalls related to blk-mq.

Thanks,
-- 
Martin