From: Jens Axboe <axboe@kernel.dk>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] pipe: read/write_iter() handler should check for IOCB_NOWAIT
Date: Thu, 30 Apr 2020 22:21:51 -0600 [thread overview]
Message-ID: <269ef3a5-e30f-ceeb-5f5e-58563e7c5367@kernel.dk> (raw)
In-Reply-To: <210c6b72-179a-993f-1ec8-1960db107174@kernel.dk>
On 4/30/20 10:14 PM, Jens Axboe wrote:
> On 4/30/20 9:58 PM, Al Viro wrote:
>> On Thu, Apr 30, 2020 at 10:24:46AM -0600, Jens Axboe wrote:
>>> Pipe read/write only checks for the file O_NONBLOCK flag, but we should
>>> also check for IOCB_NOWAIT for whether or not we should handle this read
>>> or write in a non-blocking fashion. If we don't, then we will block on
>>> data or space for iocbs that explicitly asked for non-blocking
>>> operation. This messes up callers that explicitly ask for non-blocking
>>> operations.
>>
>> Why does io_uring allow setting IOCB_NOWAIT without FMODE_NOWAIT, anyway?
>
> To do per-io non-blocking operations. It's not practical or convenient
> to flip the file flag, nor does it work if you have multiple of them
> going. If pipes honor the flag for the read/write iter handlers, then
> we can handle them a lot more efficiently instead of requiring async
> offload.
Sorry, I think I misread you and the answer, while correct by itself, is
not the answer to the question you are asking. You're saying we should
not be using IOCB_NOWAIT if FMODE_NOWAIT isn't set, which is fair. I'll
re-do the patch, we can probably just use FMODE_NOWAIT for the final
check in io_uring instead.
For pipes, we should include the setting of FMODE_NOWAIT for fifo_open()
with the patch, at least.
--
Jens Axboe
prev parent reply other threads:[~2020-05-01 4:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-30 16:24 [PATCH] pipe: read/write_iter() handler should check for IOCB_NOWAIT Jens Axboe
2020-04-30 17:58 ` Matthew Wilcox
2020-04-30 18:47 ` Jens Axboe
2020-04-30 19:51 ` Jens Axboe
2020-04-30 19:56 ` Jens Axboe
2020-05-01 3:58 ` Al Viro
2020-05-01 4:14 ` Jens Axboe
2020-05-01 4:21 ` Jens Axboe [this message]
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 \
--in-reply-to=269ef3a5-e30f-ceeb-5f5e-58563e7c5367@kernel.dk \
--to=axboe@kernel.dk \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=viro@zeniv.linux.org.uk \
/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;
as well as URLs for NNTP newsgroup(s).