linux-kernel - Re: BLKSECDISCARD ioctl and hung tasks

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Message-ID: <CAJmaN=miqzhnZUTqaTOPp+OWY8+QYhXoE=h5apSucMkEU4nvtA@mail.gmail.com>
Date:   Tue, 18 Feb 2020 08:11:53 -0800
From:   Jesse Barnes <jsbarnes@...gle.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Salman Qazi <sqazi@...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 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.

Thanks,
Jesse