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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 79A98C31E47 for ; Sat, 15 Jun 2019 04:01:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EC2B21473 for ; Sat, 15 Jun 2019 04:01:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560571319; bh=ACe1Clulv/XGccKcTCcOd9Qt05JKYgvd+gemVer94Y8=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=b3rzata2Rj5lCxpbGwLj09sk2JiEJMCXK8J+Kftklz8eZYzmzLOXYX8nwZvSs5VtM pzjuT/fFm94sKVjjF3F2wo52D9pDy3hJGndv7GPRnA0ydsPuh3yjBzNzDhJXbHHRBd eA/j2v2w9gu6baV49+BhHSGrxs1Pa14CvavAhEgs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726234AbfFOEBa (ORCPT ); Sat, 15 Jun 2019 00:01:30 -0400 Received: from mail-lj1-f170.google.com ([209.85.208.170]:43649 "EHLO mail-lj1-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbfFOEB3 (ORCPT ); Sat, 15 Jun 2019 00:01:29 -0400 Received: by mail-lj1-f170.google.com with SMTP id 16so4256527ljv.10 for ; Fri, 14 Jun 2019 21:01:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=LNCCQDzXq6yRFhVLoEUQSeznUefXALf/b6AvjDf5zbk=; b=K+NlbgNmc77iE+WvrjEBgMNlZucBcKdO/O5/nk7OZOBx6QGiPLKgW6xHqeUKR/z1/9 zyhhdNgrB4+1BFo6Zu6tRLbi1YgVBxzcym14Fw3e1Cvu/GabpqLG0GbD6xnKbRNydIPE 3038hUhYpnFUOgY2FK0lkFrB+J3deHeUX1FtU= 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=LNCCQDzXq6yRFhVLoEUQSeznUefXALf/b6AvjDf5zbk=; b=j96fJzXtcXXm/vNqH/90lJnYv8GlCDRreuH3C6gZDxQHX7F9y+qiH3pQ0vQQNIQzxV WtW3bAg4IXaS2ey0CwnkrKwSfWjhR1Gxh3BCURgblhK6BWK3V5vstdRcLAzUH18VpVj6 nxDMr39CXS/UcwCB6k+Fae7F6O1ppzkB63GOMdzxo2dbUmZXoJ6NlLdiT7ObRmGhRFl/ w8B08l2ntX/K85PRsgvoKJ9+0vjzWGI8e/4QwOtfzw4NmhlWZtUsPKuHzKEB7zeJGp+R 54EYxu/54N8jIUrQ4WmybNl9Muh3s4vu1FIBm98opxvx/SWQYfNuMkCB1u0ybfF5dVg7 oM8g== X-Gm-Message-State: APjAAAVHOnKyLMPtW0birSD25XqbFMkErNGi2XpsjngHjpTrKaC/qxzZ HDIqIVxt4/EkiCk0wcSoa6omuv+GsR4= X-Google-Smtp-Source: APXvYqwIefNGBgFt/em7vqk51EYY5g7bQ4PfNrqERzTvto7mbH22hHBZuNjqKPWfGdEcsv2JC0fuMA== X-Received: by 2002:a2e:9b48:: with SMTP id o8mr5269078ljj.122.1560571287250; Fri, 14 Jun 2019 21:01:27 -0700 (PDT) Received: from mail-lj1-f182.google.com (mail-lj1-f182.google.com. [209.85.208.182]) by smtp.gmail.com with ESMTPSA id f16sm805583lfc.81.2019.06.14.21.01.23 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Fri, 14 Jun 2019 21:01:24 -0700 (PDT) Received: by mail-lj1-f182.google.com with SMTP id h10so4311665ljg.0 for ; Fri, 14 Jun 2019 21:01:23 -0700 (PDT) X-Received: by 2002:a2e:b003:: with SMTP id y3mr18772815ljk.72.1560571283486; Fri, 14 Jun 2019 21:01:23 -0700 (PDT) MIME-Version: 1.0 References: <20190610191420.27007-1-kent.overstreet@gmail.com> <20190611011737.GA28701@kmo-pixel> <20190611043336.GB14363@dread.disaster.area> <20190612162144.GA7619@kmo-pixel> <20190612230224.GJ14308@dread.disaster.area> <20190613183625.GA28171@kmo-pixel> <20190613235524.GK14363@dread.disaster.area> In-Reply-To: From: Linus Torvalds Date: Fri, 14 Jun 2019 18:01:07 -1000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: pagecache locking (was: bcachefs status update) merged) To: Dave Chinner Cc: Kent Overstreet , Dave Chinner , "Darrick J . Wong" , Christoph Hellwig , Matthew Wilcox , Amir Goldstein , Jan Kara , Linux List Kernel Mailing , linux-xfs , linux-fsdevel , Josef Bacik , Alexander Viro , Andrew Morton Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 13, 2019 at 5:08 PM Linus Torvalds wrote: > > I do not believe that posix itself actually requires that at all, > although extended standards may. So I tried to see if I could find what this perhaps alludes to. And I suspect it's not in the read/write thing, but the pthreads side talks about atomicity. Interesting, but I doubt if that's actually really intentional, since the non-thread read/write behavior specifically seems to avoid the whole concurrency issue. The pthreads atomicity thing seems to be about not splitting up IO and doing it in chunks when you have m:n threading models, but can be (mis-)construed to have threads given higher atomicity guarantees than processes. Linus