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=ham 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 6D3B2C31E50 for ; Sat, 15 Jun 2019 04:01:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46409217D6 for ; Sat, 15 Jun 2019 04:01:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560571287; bh=ACe1Clulv/XGccKcTCcOd9Qt05JKYgvd+gemVer94Y8=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=lrURVzwtGP4rtbCWuHgvE6mxL+oxSA3Vjj/6aFp03QLnFbm5UEBGi3rblKZEP+7Ff eQedKa5G2CtPAZteCjHXzT0iBFfHXl+4N2Pp4v21hwNSMtecQPLeNQCkxd6mHnc9g1 YrrhZ+XD3/wUYoi3R4eKQc3VSnSt1jPm2ePuR50E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725817AbfFOEB0 (ORCPT ); Sat, 15 Jun 2019 00:01:26 -0400 Received: from mail-lf1-f51.google.com ([209.85.167.51]:44794 "EHLO mail-lf1-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbfFOEB0 (ORCPT ); Sat, 15 Jun 2019 00:01:26 -0400 Received: by mail-lf1-f51.google.com with SMTP id r15so3003029lfm.11 for ; Fri, 14 Jun 2019 21:01:25 -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=MJaoZGF6y9tRwCUrDXrUgbZZt2SFJGzIwOrqDe++KmbjiE5r1eU+43AwwpagyXXN0w r05Ev0bPN9riZP9/AruzKAHT2VE+DsQ/4Zw0bL4c8bWGZvmcb1omLcXfRgEsD4DruV7m HyHtBUlqoV84yj0OH1bMYpd0BPuFUWSiXKdWhRte24sD+n7W9HVSuBzM0ASK4J4ZX5e3 TD+nTJZ9WqiE0/A8cT/sw9rMrV+wvvTuIzwF2dOK36tg11CBQL1gdUL6Hxv0PCw8mzeG kckKYlUyFpNABtJ67RIT6S2lqiW3A/DSWOLvOwjfma+BLpjuicw2F7fIYTRcKuHAwLCM 3ogg== X-Gm-Message-State: APjAAAXpZ+6hZoM8YKiuCgl5UnF+ojc/1VroTwoW3rYBACtIQ4N1BRJp qMXS7wTX8VXjYA8R2lw8CgYhpkiucJk= X-Google-Smtp-Source: APXvYqylm0jY7Zh+scteXSQuuKBwBbUdFk6dbPobs1BFd3B+GX3ZQoE17q7UTyAF2tNN1TXSPs7IRA== X-Received: by 2002:a19:740e:: with SMTP id v14mr51779692lfe.144.1560571284436; Fri, 14 Jun 2019 21:01:24 -0700 (PDT) Received: from mail-lj1-f180.google.com (mail-lj1-f180.google.com. [209.85.208.180]) by smtp.gmail.com with ESMTPSA id x20sm886616ljc.15.2019.06.14.21.01.23 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-f180.google.com with SMTP id m23so4248896lje.12 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-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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