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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 19B18C433DF for ; Mon, 19 Oct 2020 06:23:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6ABD92225A for ; Mon, 19 Oct 2020 06:23:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mykernel.net header.i=cgxu519@mykernel.net header.b="gKANIoy/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726744AbgJSGXv (ORCPT ); Mon, 19 Oct 2020 02:23:51 -0400 Received: from sender2-pp-o92.zoho.com.cn ([163.53.93.251]:25368 "EHLO sender2-pp-o92.zoho.com.cn" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726626AbgJSGXv (ORCPT ); Mon, 19 Oct 2020 02:23:51 -0400 ARC-Seal: i=1; a=rsa-sha256; t=1603088610; cv=none; d=zoho.com.cn; s=zohoarc; b=rmH4iprO9Emewa10c+7gnnodsYHCKNw7shaMtG4uei9bzUWptfw1I8/tzCJhjPzCfTDJJcRV7b7hbOGAbF/ipQxd31FBK+YEelgn35S9UlFsS794LXeM+nY27xKaEXdnK4QfnjYjdrHREn8GgE9sgnEeaBgLnZgI8UOcR4q5w4A= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com.cn; s=zohoarc; t=1603088610; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:MIME-Version:Message-ID:Reply-To:References:Subject:To; bh=Ot6p5PKRwlPKGaS1bI/rWvDEIlHWn8D7OxW7I+utZP0=; b=d6zzQRno9KRhNNO0TcAUAtVoPhRRueTosJIDzFKjzOl7AypZ4Jsvi+wjoG48SLQm5dIqUMU8ogvN97enD7BcahnhSXwfb/Eb0Xoh8vLDP2WLN8BFQGnuwU3fVMML/fKjEVNSr4CxGkR2ZJb+5ujpDEgHw2aYoHjnQxIaae8AJ0g= ARC-Authentication-Results: i=1; mx.zoho.com.cn; dkim=pass header.i=mykernel.net; spf=pass smtp.mailfrom=cgxu519@mykernel.net; dmarc=pass header.from= header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1603088610; s=zohomail; d=mykernel.net; i=cgxu519@mykernel.net; h=Date:From:Reply-To:To:Cc:Message-ID:In-Reply-To:References:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding; bh=Ot6p5PKRwlPKGaS1bI/rWvDEIlHWn8D7OxW7I+utZP0=; b=gKANIoy/qte4Jdqb2KifN4aTSC4svMrQxlO6xECpiKCwcKWpd5HvprPtGym+bIce 7J/CrosfL7CyC7OUMT/E61awg0NXzCxH0WqvS4/Jb3D99RDXafIVMplJg2mw92ZrpQU wfCcBOzcahbPmV0IXVVoE648xmoaYKksYTHIpUhs= Received: from mail.baihui.com by mx.zoho.com.cn with SMTP id 1603088608337412.22111476514215; Mon, 19 Oct 2020 14:23:28 +0800 (CST) Date: Mon, 19 Oct 2020 14:23:28 +0800 From: Chengguang Xu Reply-To: cgxu519@mykernel.net To: "Amir Goldstein" Cc: "Miklos Szeredi" , "overlayfs" Message-ID: <1753f86ec4e.11b908e7c48733.2506380417104368548@mykernel.net> In-Reply-To: References: <20201016155745.2876-1-cgxu519@mykernel.net> Subject: Re: (RESEND) [PATCH] ovl: stacked file operation for mmap MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Importance: Medium User-Agent: ZohoCN Mail X-Mailer: ZohoCN Mail Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org ---- =E5=9C=A8 =E6=98=9F=E6=9C=9F=E6=97=A5, 2020-10-18 15:53:23 Amir Golds= tein =E6=92=B0=E5=86=99 ---- > On Fri, Oct 16, 2020 at 7:38 PM Chengguang Xu wro= te: > > > > Currently only mmap does not behave as stacked file operation, > > although in practice there is less change to open a file in > > RDONLY mode and take long time to do mmap but the fix looks > > reasonable. >=20 > I suppose you do not have a real life use case where this fix > is relevant? Detected by some unexpectedly running test scripts. >=20 > The thing is that this change is not without consequence. > It could result in 2 overlapping mmaps on the same RDONLY fd > mapping a different file and it can be even more confusing > than different fd mapping different files. >=20 > It is not clear which non-standard behavior is preferred, so without > any evidence that one strange behavior is preferred over the other > I don't think we should change anything. >=20 Makes sense.