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_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 B68E4C433E6 for ; Tue, 1 Sep 2020 07:45:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F0DA0204EC for ; Tue, 1 Sep 2020 07:45:10 +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="B29SfsAQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F0DA0204EC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=szeredi.hu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 922456B0055; Tue, 1 Sep 2020 03:45:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8D3B86B005A; Tue, 1 Sep 2020 03:45:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7EAE36B005C; Tue, 1 Sep 2020 03:45:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0176.hostedemail.com [216.40.44.176]) by kanga.kvack.org (Postfix) with ESMTP id 6A4946B0055 for ; Tue, 1 Sep 2020 03:45:10 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 27EF81F06 for ; Tue, 1 Sep 2020 07:45:10 +0000 (UTC) X-FDA: 77213706780.08.sleep88_1810eb227096 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id DAE0E1819E772 for ; Tue, 1 Sep 2020 07:45:09 +0000 (UTC) X-HE-Tag: sleep88_1810eb227096 X-Filterd-Recvd-Size: 4192 Received: from mail-ua1-f65.google.com (mail-ua1-f65.google.com [209.85.222.65]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Tue, 1 Sep 2020 07:45:09 +0000 (UTC) Received: by mail-ua1-f65.google.com with SMTP id y15so131124uan.9 for ; Tue, 01 Sep 2020 00:45:08 -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=3qQWrPjd+3tD5k74/h4nn6JbgY+asqimo3r0Ngu+psg=; b=B29SfsAQZZtD1+O9ml+4HmyYDPIUxcQ20/gonjENigHsMvM14mDH356np4XtIEg+o/ KqY0Wexzya3EP+VCf+VszUx+g8lxV+qC4wAvPUxxnQ8KlGtcfZ3iRe02vd8fpC9lmoov IWDiNxOASUhmkzHOVPyaZtaCwTnBFRschNkkI= 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=3qQWrPjd+3tD5k74/h4nn6JbgY+asqimo3r0Ngu+psg=; b=mOoNeoWxTwXfhkrI9EHRhPGdMrHKGeg1kWwMucZDlSmxUhWnKxJvPBuSa9ci19QxA8 n4T3dlL5ZOdEYOggkeGfYvI8EdOT8BnO4uOD/q3/dS1eSOzFBbOVxOi5eV5WlPf+yM52 4qji4LNsXrDAruqQbHcW5cqtCTlawjEexFd7HGc00EPSgBVxi1VHjmE6hoJ8HLVLs5V2 BgPDxiAxhuw883GTk+oc3WErfjrtWbFxLvHqjbFKB5h+gl17KFuCQrDEL0cTJ4WaTdfz 6G0Ak8OL6PZYjNPGS9WEiJLViPSsLXI1RPcVicwaG1czrtYvZp8CUFerPVrsaDQNprsC 4RVA== X-Gm-Message-State: AOAM532kvFO/vYGfgBhwSFpnRRB4njm1RTQMb/rZBIu21aU8x+HzEiT6 H/FLWqBdZ6iOrugmtm/fpoivJOWp3IyClwu4efJ4ZQ== X-Google-Smtp-Source: ABdhPJy+TdGpYqYf9MgROG/FQwWb9tyDw2oStkVxZTn7KESL0/FTPF1RWJcNaI1FlNO0iKCPaJAXhEZw+S8/8ZeOCCk= X-Received: by 2002:ab0:4d54:: with SMTP id k20mr243579uag.142.1598946308191; Tue, 01 Sep 2020 00:45:08 -0700 (PDT) MIME-Version: 1.0 References: <20200829095101.25350-1-cgxu519@mykernel.net> <20200829095101.25350-4-cgxu519@mykernel.net> In-Reply-To: From: Miklos Szeredi Date: Tue, 1 Sep 2020 09:44:57 +0200 Message-ID: Subject: Re: [RFC PATCH 3/3] ovl: implement stacked mmap for shared map To: Amir Goldstein Cc: cgxu , overlayfs , Linux MM , Andrew Morton , Ritesh Harjani Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: DAE0E1819E772 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 31, 2020 at 5:52 PM Amir Goldstein wrote: > > On Mon, Aug 31, 2020 at 4:47 PM cgxu wrote: > > > > On 8/30/20 7:33 PM, Amir Goldstein wrote: > > > Interesting direction, not sure if this is workable. > > > I don't know enough about mm to say. > > > > > > But what about the rest of the operations? > > > Did you go over them and decide that overlay doesn't need to implement them? > > > I doubt it, but if you did, please document that. > > > > I did some check for rest of them, IIUC ->fault will be enough for this > > special case (shared read-only mmap with no upper), I will remove > > ->page_mkwrite in v2. Hmm, so this is just for that specific corner case? Not a generic shared mmap implementation? > > Ok I suppose you checked that ->map_pages is not relevant? > > > > > # I do not consider support ->huge_fault in current stage due to many fs > > cannot support DAX properly. > > > > BTW, do you know who should I add to CC list for further deep review of > > this code? fadevel-list? > > > > fsdevel would be good, but I would wait for initial feedback from Miklos > before you post v2... I could dig into the details of page fault handling, but that's not an area that I'm intimately familiar with. So yeah, a high level description of what happens on mmap, page fault, write fault, etc... would be really appreciated. Thanks, Miklos