From: Ming Lei <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Linus Torvalds <[email protected]>,
Andy Lutomirski <[email protected]>,
Dave Chinner <[email protected]>,
Matthew Wilcox <[email protected]>,
Stefan Metzmacher <[email protected]>,
linux-fsdevel <[email protected]>,
Linux API Mailing List <[email protected]>,
io-uring <[email protected]>,
"[email protected]" <[email protected]>,
Al Viro <[email protected]>,
Samba Technical <[email protected]>,
[email protected]
Subject: Re: copy on write for splice() from file to pipe?
Date: Sat, 11 Feb 2023 23:05:35 +0800 [thread overview]
Message-ID: <Y+euv+zR5ltTELqk@T590> (raw)
In-Reply-To: <[email protected]>
On Sat, Feb 11, 2023 at 07:13:44AM -0700, Jens Axboe wrote:
> On 2/10/23 8:18?PM, Ming Lei wrote:
> > On Fri, Feb 10, 2023 at 02:08:35PM -0800, Linus Torvalds wrote:
> >> On Fri, Feb 10, 2023 at 1:51 PM Jens Axboe <[email protected]> wrote:
> >>>
> >>> Speaking of splice/io_uring, Ming posted this today:
> >>>
> >>> https://lore.kernel.org/io-uring/[email protected]/
> >>
> >> Ugh. Some of that is really ugly. Both 'ignore_sig' and
> >> 'ack_page_consuming' just look wrong. Pure random special cases.
> >>
> >> And that 'ignore_sig' is particularly ugly, since the only thing that
> >> sets it also sets SPLICE_F_NONBLOCK.
> >>
> >> And the *only* thing that actually then checks that field is
> >> 'splice_from_pipe_next()', where there are exactly two
> >> signal_pending() checks that it adds to, and
> >>
> >> (a) the first one is to protect from endless loops
> >>
> >> (b) the second one is irrelevant when SPLICE_F_NONBLOCK is set
> >>
> >> So honestly, just NAK on that series.
> >>
> >> I think that instead of 'ignore_sig' (which shouldn't exist), that
> >> first 'signal_pending()' check in splice_from_pipe_next() should just
> >> be changed into a 'fatal_signal_pending()'.
> >
> > Good point, here the signal is often from task_work_add() called by
> > io_uring.
>
> Usually you'd use task_sigpending() to distinguis the two, but
> fatal_signal_pending() as Linus suggests would also work. The only
> concern here is that since you'll be potentially blocking on waiting for
> the pipe to be readable - if task does indeed have task_work pending and
> that very task_work is the one that will ensure that the pipe is now
> readable, then you're waiting condition will never be satisfied.
The 2nd signal_pending() will break the loop to get task_work handled,
so it is safe to only change the 1st one to fatal_signal_pending().
Thanks,
Ming
next prev parent reply other threads:[~2023-02-11 15:06 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-09 13:55 copy on write for splice() from file to pipe? Stefan Metzmacher
2023-02-09 14:11 ` Matthew Wilcox
2023-02-09 14:29 ` Stefan Metzmacher
2023-02-09 16:41 ` Linus Torvalds
2023-02-09 19:17 ` Stefan Metzmacher
2023-02-09 19:36 ` Linus Torvalds
2023-02-09 19:48 ` Linus Torvalds
2023-02-09 20:33 ` Jeremy Allison
2023-02-10 20:45 ` Stefan Metzmacher
2023-02-10 20:51 ` Linus Torvalds
2023-02-10 2:16 ` Dave Chinner
2023-02-10 4:06 ` Dave Chinner
2023-02-10 4:44 ` Matthew Wilcox
2023-02-10 6:57 ` Dave Chinner
2023-02-10 15:14 ` Andy Lutomirski
2023-02-10 16:33 ` Linus Torvalds
2023-02-10 17:57 ` Andy Lutomirski
2023-02-10 18:19 ` Jeremy Allison
2023-02-10 19:29 ` Stefan Metzmacher
2023-02-10 18:37 ` Linus Torvalds
2023-02-10 19:01 ` Andy Lutomirski
2023-02-10 19:18 ` Linus Torvalds
2023-02-10 19:27 ` Jeremy Allison
2023-02-10 19:42 ` Stefan Metzmacher
2023-02-10 19:42 ` Linus Torvalds
2023-02-10 19:54 ` Stefan Metzmacher
2023-02-10 19:29 ` Linus Torvalds
2023-02-13 9:07 ` Herbert Xu
2023-02-10 19:55 ` Andy Lutomirski
2023-02-10 20:27 ` Linus Torvalds
2023-02-10 20:32 ` Jens Axboe
2023-02-10 20:36 ` Linus Torvalds
2023-02-10 20:39 ` Jens Axboe
2023-02-10 20:44 ` Linus Torvalds
2023-02-10 20:50 ` Jens Axboe
2023-02-10 21:14 ` Andy Lutomirski
2023-02-10 21:27 ` Jens Axboe
2023-02-10 21:51 ` Jens Axboe
2023-02-10 22:08 ` Linus Torvalds
2023-02-10 22:16 ` Jens Axboe
2023-02-10 22:17 ` Linus Torvalds
2023-02-10 22:25 ` Jens Axboe
2023-02-10 22:35 ` Linus Torvalds
2023-02-10 22:51 ` Jens Axboe
2023-02-11 3:18 ` Ming Lei
2023-02-11 6:17 ` Ming Lei
2023-02-11 14:13 ` Jens Axboe
2023-02-11 15:05 ` Ming Lei [this message]
2023-02-11 15:33 ` Jens Axboe
2023-02-11 18:57 ` Linus Torvalds
2023-02-12 2:46 ` Jens Axboe
2023-02-10 4:47 ` Linus Torvalds
2023-02-10 6:19 ` Dave Chinner
2023-02-10 17:23 ` Linus Torvalds
2023-02-10 17:47 ` Linus Torvalds
2023-02-13 9:28 ` Herbert Xu
2023-02-10 22:41 ` David Laight
2023-02-10 22:51 ` Jens Axboe
2023-02-13 9:30 ` Herbert Xu
2023-02-13 9:25 ` Herbert Xu
2023-02-13 18:01 ` Andy Lutomirski
2023-02-14 1:22 ` Herbert Xu
2023-02-17 23:13 ` Andy Lutomirski
2023-02-20 4:54 ` Herbert Xu
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