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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 B509DC55194 for ; Thu, 23 Apr 2020 07:57:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9236C2168B for ; Thu, 23 Apr 2020 07:57:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="VBDSp624" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726384AbgDWH5d (ORCPT ); Thu, 23 Apr 2020 03:57:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726371AbgDWH5c (ORCPT ); Thu, 23 Apr 2020 03:57:32 -0400 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 912D1C08E859 for ; Thu, 23 Apr 2020 00:57:30 -0700 (PDT) Received: by mail-ej1-x643.google.com with SMTP id x1so4002137ejd.8 for ; Thu, 23 Apr 2020 00:57:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0AZ3LfYwwbdgd8+Gj6pfmGUhFDqMfSzSNioVUGjPTRU=; b=VBDSp624eeG5DG/gndTNaHMLvSdjtkZwVvqIk0HLfICAWTd3DdqJGCOdF+j3ZkiaF6 OkJMkZajYDgkASdTcGVDQrKBArkOd3uXBgFTNPbyeCHS2d5P8A4O/ddQo/nRm1J/P6HS 8YiyHoRzIG8e5maMV6UFDTwGB3oaF3TD+HG1c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0AZ3LfYwwbdgd8+Gj6pfmGUhFDqMfSzSNioVUGjPTRU=; b=EOJwi33Z+5vJ32p86WrFAZxe/h5uGL/5HLEA8BYErhx0icfGXRZzZvzmFfNtmgAVTr tos9Wi4SjliQ8UthBe1boKXWX4AaVhYw65OC/VK9V3oLE2F0lByQxTnuMFr9M5APR4/N 6pNd8nM04GIFuR+zcgfwZMvohx2v9y+F2TOjJhp/jihIeexFvV1ZvarfIG/YSYFetW8U 35bUJdN3dAHgZqVwI+j6fpVwoMeplw9+DloTzJ6EK5yPtW1YQEKIFN25pxMtz8EsIUSH KH8l1EJxv4syuao14P35U/56FVZ5oIfEd11Je4qrMeCJXGvtDvyMqb1NPsUowxQo+csl p7Qg== X-Gm-Message-State: AGi0PuZQRooxTIaEhtFVi01NdscAGqSrwYqyzMm2MX8CHyGa7BeU19H1 myQ/oU/EQFZhz1QWacl0OCI3IICahpETVPnR5u526MXa X-Google-Smtp-Source: APiQypL8rnmcwmDcw0tzT8pkej1MVZvhOLUD9Stz7ZrjoCE/HfT+UO7lMR79fX8pKJtq7nSgVTmdAXP4XeG1L6cdh0M= X-Received: by 2002:a17:906:340a:: with SMTP id c10mr1706242ejb.218.1587628649150; Thu, 23 Apr 2020 00:57:29 -0700 (PDT) MIME-Version: 1.0 References: <9873b8bd7d14ff8cd2a5782b434b39f076679eeb.1587531463.git.josh@joshtriplett.org> <20200423004807.GC161058@localhost> <20200423044226.GH161058@localhost> <20200423073310.GA169998@localhost> In-Reply-To: From: Miklos Szeredi Date: Thu, 23 Apr 2020 09:57:17 +0200 Message-ID: Subject: Re: [PATCH v5 2/3] fs: openat2: Extend open_how to allow userspace-selected fds To: Josh Triplett Cc: Michael Kerrisk , io-uring@vger.kernel.org, "linux-fsdevel@vger.kernel.org" , lkml , Alexander Viro , Arnd Bergmann , Jens Axboe , Aleksa Sarai , linux-man , Linux API Content-Type: text/plain; charset="UTF-8" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, Apr 23, 2020 at 9:45 AM Miklos Szeredi wrote: > > 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, we could add an op to dup/move a private > descriptor to a public one. io_uring can return values, right? > > Still not convinced... Oh, and we haven't even touched on the biggest advantage of a private fd table: not having to dirty a cacheline on fdget/fdput due to the possibility of concurrent close() in a MT application. I believe this is a sticking point in some big enterprise apps and it may even be a driving force for io_uring. Thanks, Miklos