From: Jens Axboe <axboe@kernel.dk>
To: Bart Van Assche <bvanassche@acm.org>, Stefan Roesch <shr@fb.com>,
kernel-team@fb.com, linux-block@vger.kernel.org
Cc: io-uring@vger.kernel.org
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: <601dac34-c3e3-5e86-852f-aaa489226733@kernel.dk> (raw)
In-Reply-To: <24aad185-fc3e-420b-b638-227c4564bcf8@acm.org>
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
next prev parent 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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