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From: Jens Axboe <[email protected]>
To: Bart Van Assche <[email protected]>, Stefan Roesch <[email protected]>,
	[email protected], [email protected]
Cc: [email protected]
Subject: Re: [PATCH v1] block: blk_queue_enter() / __bio_queue_enter() must return -EAGAIN for nowait
Date: Mon, 12 Sep 2022 11:22:02 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 9/12/22 11:14 AM, Bart Van Assche wrote:
> On 9/12/22 09:53, Stefan Roesch wrote:
>> Today blk_queue_enter() and __bio_queue_enter() return -EBUSY for the
>> nowait code path. This is not correct: they should return -EAGAIN
>> instead.
> 
> Why is this considered incorrect? Please explain.
> 
> Since this patch also affects other code, e.g. NVMe pass-through, can
> this patch break existing user space code by changing the value
> returned to user space?

It is currently broken because we always return EAGAIN/EWOULDBLOCK for
these cases, if a non-block flag is set of some sort. I strongly suspect
that nobody has really being doing non-blocking IO to devices before
io_uring made it a lot more common. EAGAIN means "try again later, or
without nonblock said".

We should be consistent here.

-- 
Jens Axboe

  reply	other threads:[~2022-09-12 17:22 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-12 16:53 [PATCH v1] block: blk_queue_enter() / __bio_queue_enter() must return -EAGAIN for nowait Stefan Roesch
2022-09-12 17:14 ` Bart Van Assche
2022-09-12 17:22   ` Jens Axboe [this message]
2022-09-13 21:08 ` Jens Axboe

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