public inbox for [email protected]
 help / color / mirror / Atom feed
From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>, Daurnimator <[email protected]>
Cc: [email protected]
Subject: Re: [PATCHSET 0/4] Add support for shared io-wq backends
Date: Tue, 28 Jan 2020 00:45:22 +0300	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>


[-- Attachment #1.1: Type: text/plain, Size: 1924 bytes --]

On 27/01/2020 23:33, Jens Axboe wrote:
> On 1/27/20 7:07 AM, Pavel Begunkov wrote:
>> On 1/27/2020 4:39 PM, Jens Axboe wrote:
>>> On 1/27/20 6:29 AM, Pavel Begunkov wrote:
>>>> On 1/26/2020 8:00 PM, Jens Axboe wrote:
>>>>> On 1/26/20 8:11 AM, Pavel Begunkov wrote:
>>>>>> On 1/26/2020 4:51 AM, Daurnimator wrote:
>>>>>>> On Fri, 24 Jan 2020 at 10:16, Jens Axboe <[email protected]> wrote:
>>>> Ok. I can't promise it'll play handy for sharing. Though, you'll be out
>>>> of space in struct io_uring_params soon anyway.
>>>
>>> I'm going to keep what we have for now, as I'm really not imagining a
>>> lot more sharing - what else would we share? So let's not over-design
>>> anything.
>>>
>> Fair enough. I prefer a ptr to an extendable struct, that will take the
>> last u64, when needed.
>>
>> However, it's still better to share through file descriptors. It's just
>> not secure enough the way it's now.
> 
> Is the file descriptor value really a good choice? We just had some
> confusion on ring sharing across forks. Not sure using an fd value
> is a sane "key" to use across processes.
> 
As I see it, the problem with @mm is that uring is dead-bound to it. For
example, a process can create and send uring (e.g. via socket), and then be
killed. And that basically means
1. @mm of the process is locked just because of the sent uring instance.
2. a process may have an io_uring, which bound to @mm of another process, even
though the layouts may be completely different.

File descriptors are different here, because io_uring doesn't know about them,
They are controlled by the userspace (send, dup, fork, etc), and don't sabotage
all isolation work done in the kernel. A dire example here is stealing io-wq
from within a container, which is trivial with global self-made id. I would love
to hear, if I am mistaken somewhere.

Is there some better option?

-- 
Pavel Begunkov


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  reply	other threads:[~2020-01-27 21:46 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23 23:16 [PATCHSET 0/4] Add support for shared io-wq backends Jens Axboe
2020-01-23 23:16 ` [PATCH 1/4] io-wq: make the io_wq ref counted Jens Axboe
2020-01-23 23:16 ` [PATCH 2/4] io-wq: add 'id' to io_wq Jens Axboe
2020-01-23 23:16 ` [PATCH 3/4] io-wq: allow lookup of existing io_wq with given id Jens Axboe
2020-01-24  9:54   ` Stefan Metzmacher
2020-01-24 16:41     ` Jens Axboe
2020-01-23 23:16 ` [PATCH 4/4] io_uring: add support for sharing kernel io-wq workqueue Jens Axboe
2020-01-24  9:51 ` [PATCHSET 0/4] Add support for shared io-wq backends Stefan Metzmacher
2020-01-24 16:43   ` Jens Axboe
2020-01-24 19:14     ` Stefan Metzmacher
2020-01-24 21:37       ` Jens Axboe
2020-01-24 20:34 ` Pavel Begunkov
2020-01-24 21:38   ` Jens Axboe
2020-01-26  1:51 ` Daurnimator
2020-01-26 15:11   ` Pavel Begunkov
2020-01-26 17:00     ` Jens Axboe
2020-01-27 13:29       ` Pavel Begunkov
2020-01-27 13:39         ` Jens Axboe
2020-01-27 14:07           ` Pavel Begunkov
2020-01-27 19:39             ` Pavel Begunkov
2020-01-27 19:45               ` Jens Axboe
2020-01-27 20:33             ` Jens Axboe
2020-01-27 21:45               ` Pavel Begunkov [this message]
2020-01-27 22:40                 ` Jens Axboe
2020-01-27 23:00                   ` Jens Axboe
2020-01-27 23:17                     ` Pavel Begunkov
2020-01-27 23:23                       ` Jens Axboe
2020-01-27 23:25                         ` Pavel Begunkov
2020-01-27 23:38                           ` Jens Axboe
2020-01-28 10:01                             ` Stefan Metzmacher
2020-01-28 10:30                               ` Pavel Begunkov
2020-01-28 10:35                                 ` Stefan Metzmacher
2020-01-28 10:51                                   ` Pavel Begunkov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox