linux-kernel - Re: BLKSECDISCARD ioctl and hung tasks

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Date:   Wed, 19 Feb 2020 09:37:14 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jesse Barnes <jsbarnes@...gle.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 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.

We may add a warning(device name, request, ...) when one IO isn't completed in
sysctl_hung_task_timeout_secs, so this device misbehavior still can be
caught.

> 
> 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.

OK, I will post it soon.


Thanks,
Ming