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From: Josh Triplett <[email protected]>
To: Miklos Szeredi <[email protected]>
Cc: Michael Kerrisk <[email protected]>,
	[email protected],
	"[email protected]" <[email protected]>,
	lkml <[email protected]>,
	Alexander Viro <[email protected]>,
	Arnd Bergmann <[email protected]>, Jens Axboe <[email protected]>,
	Aleksa Sarai <[email protected]>,
	linux-man <[email protected]>,
	Linux API <[email protected]>
Subject: Re: [PATCH v5 2/3] fs: openat2: Extend open_how to allow userspace-selected fds
Date: Thu, 23 Apr 2020 01:06:44 -0700	[thread overview]
Message-ID: <20200423080644.GA171696@localhost> (raw)
In-Reply-To: <CAJfpegtXj4bSbhpx+=z=R0_ZT8uPEJAAev0O+DVg3AX242e=-g@mail.gmail.com>

On Thu, Apr 23, 2020 at 09:45:45AM +0200, Miklos Szeredi wrote:
> On Thu, Apr 23, 2020 at 9:33 AM Josh Triplett <[email protected]> wrote:
> > > What are the plans for those syscalls that don't easily lend
> > > themselves to this modification (such as accept(2))?
> >
> > accept4 has a flags argument with more flags available, so it'd be
> > entirely possible to cleanly extend it further without introducing a new
> > version.
>
> Variable argument syscalls, you are thinking?

That or repurposing an existing pointer-sized argument as an
open_how-style struct, yes. But in any case, I'm not proposing that; I'm
proposing changes to the existing highly extensible openat2 syscall.

> > > I mean, you could open the file descriptor outside of io_uring in such
> > > cases, no?
> >
> > I would prefer to not introduce that limitation in the first place, and
> > instead open normal file descriptors.
> >
> > > The point of O_SPECIFIC_FD is to be able to perform short
> > > sequences of open/dosomething/close without having to block and having
> > > to issue separate syscalls.
> >
> > "close" is not a required component. It's entirely possible to use
> > io_uring to open a file descriptor, do various things with it, and then
> > leave it open for subsequent usage via either other io_uring chains or
> > standalone syscalls.
> 
> If this use case arraises,

This wasn't a hypothetical "someone might want this". I'm stating that
this is a requirement I'm seeking to meet with this patch series, and
one I intend to use. The primary use case is interoperability with
other code using file descriptors and not using io_uring.

  parent reply	other threads:[~2020-04-23  8:06 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-22  5:19 [PATCH v5 0/3] Support userspace-selected fds Josh Triplett
2020-04-22  5:19 ` [PATCH v5 1/3] fs: Support setting a minimum fd for "lowest available fd" allocation Josh Triplett
2020-04-22  6:06   ` Michael Kerrisk (man-pages)
2020-04-23  1:12   ` Dmitry V. Levin
2020-04-23  4:51     ` Josh Triplett
2020-04-23  9:24   ` Arnd Bergmann
2020-04-22  5:20 ` [PATCH v5 2/3] fs: openat2: Extend open_how to allow userspace-selected fds Josh Triplett
2020-04-22  6:06   ` Michael Kerrisk (man-pages)
2020-04-22  7:55     ` Miklos Szeredi
2020-04-23  0:48       ` Josh Triplett
2020-04-23  4:24         ` Miklos Szeredi
2020-04-23  4:42           ` Josh Triplett
2020-04-23  6:04             ` Miklos Szeredi
2020-04-23  7:33               ` Josh Triplett
2020-04-23  7:45                 ` Miklos Szeredi
2020-04-23  7:57                   ` Miklos Szeredi
2020-04-23  9:20                     ` Miklos Szeredi
2020-04-23  9:46                       ` Miklos Szeredi
2020-04-23  8:06                   ` Josh Triplett [this message]
2020-04-22  5:20 ` [PATCH v5 3/3] fs: pipe2: Support O_SPECIFIC_FD Josh Triplett
2020-04-22  6:06   ` Michael Kerrisk (man-pages)
2020-04-22 15:44   ` Florian Weimer
2020-04-23  0:44     ` Josh Triplett
2020-04-22  6:05 ` [PATCH v5 0/3] Support userspace-selected fds Michael Kerrisk (man-pages)

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