From: Christoph Hellwig <hch@infradead.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, dm-devel@redhat.com,
Eric Wheeler <dm-devel@lists.ewheeler.net>
Subject: Re: [PATCH] dm crypt: fix lost ioprio when queuing crypto bios from task with ioprio
Date: Fri, 7 Dec 2018 11:43:20 -0800 [thread overview]
Message-ID: <20181207194319.GA1690@infradead.org> (raw)
In-Reply-To: <20181206221507.5423-1-snitzer@redhat.com>
On Thu, Dec 06, 2018 at 05:15:07PM -0500, Mike Snitzer wrote:
> From: Eric Wheeler <dm-devel@lists.ewheeler.net>
>
> Since dm-crypt queues writes (and sometimes reads) to a different kernel
> thread (workqueue), the bios will dispatch from tasks with different
> io_context->ioprio settings than the submitting task, thus giving
> incorrect ioprio hints to the io scheduler.
>
> By assigning the ioprio to the bio before queuing to a workqueue, the
> original submitting task's io_context->ioprio setting can be retained
> through the life of the bio. We only set the bio's ioprio in dm-crypt
> if not already set (by somewhere else, higher in the stack).
The scheme looks a little odd to me. Instead of requring a driver
call why don't we just make sure bios always have the submitting
tasks priority set and then make sure the lower layers can rely on it?
next prev parent reply other threads:[~2018-12-07 19:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-06 22:15 [PATCH] dm crypt: fix lost ioprio when queuing crypto bios from task with ioprio Mike Snitzer
2018-12-06 23:04 ` Jens Axboe
2018-12-07 19:43 ` Christoph Hellwig [this message]
2018-12-07 20:20 ` Mike Snitzer
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