From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F4B3C3F2CE for ; Wed, 4 Mar 2020 20:09:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C08720870 for ; Wed, 4 Mar 2020 20:09:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728278AbgCDUJg (ORCPT ); Wed, 4 Mar 2020 15:09:36 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:49379 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727835AbgCDUJg (ORCPT ); Wed, 4 Mar 2020 15:09:36 -0500 X-Originating-IP: 92.243.9.8 Received: from localhost (joshtriplett.org [92.243.9.8]) (Authenticated sender: josh@joshtriplett.org) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id B53531C0003; Wed, 4 Mar 2020 20:09:34 +0000 (UTC) Date: Wed, 4 Mar 2020 12:09:34 -0800 From: Josh Triplett To: Jens Axboe Cc: io-uring@vger.kernel.org, jlayton@kernel.org Subject: Re: [PATCHSET v2 0/6] Support selectable file descriptors Message-ID: <20200304200934.GC16527@localhost> References: <20200304180016.28212-1-axboe@kernel.dk> <20200304190341.GB16251@localhost> <121d15a7-4b21-368c-e805-a0660b1c851a@kernel.dk> <20200304195642.GB16527@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, Mar 04, 2020 at 01:00:05PM -0700, Jens Axboe wrote: > On 3/4/20 12:56 PM, Josh Triplett wrote: > > On Wed, Mar 04, 2020 at 12:10:08PM -0700, Jens Axboe wrote: > >> On 3/4/20 12:03 PM, Josh Triplett wrote: > >>> On Wed, Mar 04, 2020 at 11:00:10AM -0700, Jens Axboe wrote: > >>>> One of the fabled features with chains has long been the desire to > >>>> support things like: > >>>> > >>>> > >>>> > >>>> in a single chain. This currently doesn't work, since the read/close > >>>> depends on what file descriptor we get on open. > >>>> > >>>> The original attempt at solving this provided a means to pass > >>>> descriptors between chains in a link, this version takes a different > >>>> route. Based on Josh's support for O_SPECIFIC_FD, we can instead control > >>>> what fd value we're going to get out of open (or accept). With that in > >>>> place, we don't need to do any magic to make this work. The above chain > >>>> then becomes: > >>>> > >>>> > >>>> > >>>> which is a lot more useful, and allows any sort of weird chains without > >>>> needing to nest "last open" file descriptors. > >>>> > >>>> Updated the test program to use this approach: > >>>> > >>>> https://git.kernel.dk/cgit/liburing/plain/test/orc.c?h=fd-select > >>>> > >>>> which forces the use of fd==89 for the open, and then uses that for the > >>>> read and close. > >>>> > >>>> Outside of this adaptation, fixed a few bugs and cleaned things up. > >>> > >>> I posted one comment about an issue in patch 6. > >>> > >>> Patches 2-5 look great; for those: > >>> Reviewed-by: Josh Triplett > >>> > >>> Thanks for picking this up and running with it! > >> > >> Thanks for doing the prep work! I think it turned out that much better > >> for it. > >> > >> Are you going to post your series for general review? I just stole > >> your 1 patch that was needed for me. > > > > Since your patch series depends on mine, please feel free to run with > > the series. Would you mind adding my patch 1 and 3 at the end of your > > series? You need patch 1 to make this more usable for userspace, and > > patch 3 would allow for an OP_PIPE which I'd love to have. > > Let me add patch 1 to the top of the stack, for the pipe part that > probably should be taken in separately. But not a huge deal to me, > as long as we can get it reviewed. That works for me; I don't mind if the pipe support goes in a bit later. And there are many other fd-producing syscalls that need support for userspace-selected FDs, including signalfd4, eventfd2, timerfd_create, epoll_create1, memfd_create, userfaultfd, and the pidfd family. > > Do you plan to submit this during the next merge window? > > Maybe? In terms of timing, I think we're well within the opportunity > to do so, at least. I look forward to seeing it go in. - Josh Triplett