linux-kernel - Re: BLKSECDISCARD ioctl and hung tasks

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Message-ID: <CAKUOC8UceQ_cDQC8ckvUio0AZHhasi7Np-PQ09e-dQ3fechKoA@mail.gmail.com>
Date:   Wed, 19 Feb 2020 09:54:31 -0800
From:   Salman Qazi <sqazi@...gle.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jesse Barnes <jsbarnes@...gle.com>,
        Ming Lei <tom.leiming@...il.com>,
        Bart Van Assche <bvanassche@....org>,
        Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        Gwendal Grignou <gwendal@...gle.com>
Subject: Re: BLKSECDISCARD ioctl and hung tasks

On Tue, Feb 18, 2020 at 6:55 PM Ming Lei <ming.lei@...hat.com> wrote:
>
> On Tue, Feb 18, 2020 at 08:11:53AM -0800, Jesse Barnes wrote:
> > On Fri, Feb 14, 2020 at 7:47 PM Ming Lei <ming.lei@...hat.com> wrote:
> > > What are the 'other operations'? Are they block IOs?
> > >
> > > If yes, that is why I suggest to fix submit_bio_wait(), which should cover
> > > most of sync bio submission.
> > >
> > > Anyway, the fix is simple & generic enough, I'd plan to post a formal
> > > patch if no one figures out better doable approaches.
> >
> > Yeah I think any block I/O operation that occurs after the
> > BLKSECDISCARD is submitted will also potentially be affected by the
> > hung task timeouts, and I think your patch will address that.  My only
> > concern with it is that it might hide some other I/O "hangs" that are
> > due to device misbehavior instead.  Yes driver and device timeouts
> > should generally catch those, but with this in place we might miss a
> > few bugs.
> >
> > Given the nature of these types of storage devices though, I think
> > that's a minor issue and not worth blocking the patch on, given that
> > it should prevent a lot of false positive hang reports as Salman
> > demonstrated.
>
> Hello Jesse and Salman,
>
> One more question about this issue, do you enable BLK_WBT on your test
> kernel?

It doesn't exist on the original 4.4-based kernel where we reproduced
this bug.  I am curious how this interacts with this bug.

>
> Thanks,
> Ming
>