From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH 09/11] io_uring: prepare fixed rw for dynanic buffers
Date: Fri, 23 Apr 2021 08:25:07 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <16e90af9d67f0f4b3c7c326974b8dbcc1c874797.1619128798.git.asml.silence@gmail.com>
On 4/22/21 6:19 PM, Pavel Begunkov wrote:
> With dynamic buffer updates, registered buffers in the table may change
> at any moment. First of all we want to prevent future races between
> updating and importing (i.e. io_import_fixed()), where the latter one
> may happen without uring_lock held, e.g. from io-wq.
>
> A second problem is that currently we may do importing several times for
> IORING_OP_{READ,WRITE}_FIXED, e.g. getting -EAGAIN on an inline attempt
> and then redoing import after apoll/from iowq. In this case it can see
> two completely different buffers, that's not good, especially since we
> often hide short reads from the userspace.
I don't think this is necessarily a problem. If you unregister a buffer
before IO completion of that IO, then you are putting yourself solidly
in grey zone areas anyway. You could still allow the short retry, just
double check that it's the same buffer at that point as a sanity
check.
--
Jens Axboe
next prev parent reply other threads:[~2021-04-23 14:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-23 0:19 [RFC 00/11] dynamic buffers + rsrc tagging Pavel Begunkov
2021-04-23 0:19 ` [PATCH 01/11] io_uring: move __io_sqe_files_unregister Pavel Begunkov
2021-04-23 0:19 ` [PATCH 02/11] io_uring: return back rsrc data free helper Pavel Begunkov
2021-04-23 0:19 ` [PATCH 03/11] io_uring: decouple CQE filling from requests Pavel Begunkov
2021-04-23 0:19 ` [PATCH 04/11] io_uring: preparation for rsrc tagging Pavel Begunkov
2021-04-23 0:19 ` [PATCH 05/11] io_uring: add generic path for rsrc update Pavel Begunkov
2021-04-23 0:19 ` [PATCH 06/11] io_uring: enumerate dynamic resources Pavel Begunkov
2021-04-23 0:19 ` [PATCH 07/11] io_uring: add IORING_REGISTER_RSRC Pavel Begunkov
2021-04-23 0:19 ` [PATCH 08/11] io_uring: add generic rsrc update with tags Pavel Begunkov
2021-04-23 0:19 ` [PATCH 09/11] io_uring: prepare fixed rw for dynanic buffers Pavel Begunkov
2021-04-23 14:25 ` Jens Axboe [this message]
2021-04-23 0:19 ` [PATCH 10/11] io_uring: implement fixed buffers registration similar to fixed files Pavel Begunkov
2021-04-23 0:19 ` [PATCH 11/11] io_uring: add full-fledged dynamic buffers support Pavel Begunkov
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