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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 157ACC43461 for ; Tue, 27 Apr 2021 18:03:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBE4461403 for ; Tue, 27 Apr 2021 18:03:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238819AbhD0SEJ (ORCPT ); Tue, 27 Apr 2021 14:04:09 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59983 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238526AbhD0SEE (ORCPT ); Tue, 27 Apr 2021 14:04:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619546600; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=uxq6LnPiTdql8TXSE99+fcYiPX1sdJEySNHvDoQFyd4=; b=SKhB7exCvRRzgTjbfIbZovSy+ZRh3bNfNB9xomIZaflGLM7Zx4oUBV1+hmLD72PDTSwVe+ cX1JHmDX7XJgxcwEzgEjP7NY3elVF6JWmrAVWdkFzz5GFX3G6C8qMn4HSXn5cg0R+I8SGE YHfxGWnWtN/pFuFCMXkbst2Bf4+H/KQ= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-402-RsPhAnXONL6OXC2L6WDObQ-1; Tue, 27 Apr 2021 14:03:18 -0400 X-MC-Unique: RsPhAnXONL6OXC2L6WDObQ-1 Received: by mail-qk1-f197.google.com with SMTP id h15-20020a37de0f0000b029029a8ada2e18so23482369qkj.11 for ; Tue, 27 Apr 2021 11:03:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=uxq6LnPiTdql8TXSE99+fcYiPX1sdJEySNHvDoQFyd4=; b=PMGBZaMm0qPkH236WuNX3KZhbuI4Ng6z69990BWP9T/EyTHTYDOnOy9xqwvppBHsRl ZdJwOVsYhcthGXyuvAdaKkGs0uqqFefI9vxrjfm2PCe9QngiSG5rh2G7i3a7IwClvU2H whr1i+6MCutwvHK9Vl23Or1XodwNev5eg9GMJPOqHfJJQNVY8nBzkH5OIv6BwTPvhVya hKBPE48HY0/GG+t8V25+yu+7xra64oF2zOaMr0aYwUQRZpkt0NgaNmuuQbGhcXUQvdt/ aOlcqQgJ+Gvh7Inhl1MEegFxjoMcckzOUwIND7Y77A1MEoDTSW8YQKUufHk6giNUmHmb u58Q== X-Gm-Message-State: AOAM530ixlqx2S8+93bfpzGqPfDeUdS+RRJqz+L3Ahve0BXDl3wuV5gr gwAGVMZYVt5I7qiHOIHmyM6N11m+t9xL9rm9i4Z11IpnLhi/dZJQiqBFzehs/A+KE8cWPheKR2V +AHohNqV4EGAOiNr6dh8x X-Received: by 2002:a05:620a:f:: with SMTP id j15mr24057474qki.307.1619546597725; Tue, 27 Apr 2021 11:03:17 -0700 (PDT) X-Google-Smtp-Source: ABdhPJztCC+XrZldYdKF/5ItbBDWFXLnijjmmS8bfVQi6TI1Vej0NaMb+NFRcFob5jVc3TcuhD2/Iw== X-Received: by 2002:a05:620a:f:: with SMTP id j15mr24057430qki.307.1619546597418; Tue, 27 Apr 2021 11:03:17 -0700 (PDT) Received: from xz-x1 (bras-base-toroon474qw-grc-77-184-145-104-227.dsl.bell.ca. [184.145.104.227]) by smtp.gmail.com with ESMTPSA id q26sm1313209qkn.81.2021.04.27.11.03.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Apr 2021 11:03:16 -0700 (PDT) Date: Tue, 27 Apr 2021 14:03:14 -0400 From: Peter Xu To: Axel Rasmussen Cc: Hugh Dickins , Alexander Viro , Andrea Arcangeli , Andrew Morton , Jerome Glisse , Joe Perches , Lokesh Gidra , Mike Kravetz , Mike Rapoport , Shaohua Li , Shuah Khan , Stephen Rothwell , Wang Qing , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, LKML , linux-kselftest@vger.kernel.org, Linux MM , Brian Geffon , "Dr . David Alan Gilbert" , Mina Almasry , Oliver Upton Subject: Re: [PATCH v4 03/10] userfaultfd/shmem: support UFFDIO_CONTINUE for shmem Message-ID: <20210427180314.GD6820@xz-x1> References: <20210420220804.486803-1-axelrasmussen@google.com> <20210420220804.486803-4-axelrasmussen@google.com> <20210427155414.GB6820@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Tue, Apr 27, 2021 at 09:57:16AM -0700, Axel Rasmussen wrote: > I'd prefer to keep them separate, as they are not tiny patches (they > are roughly +200/-150 each). And, they really are quite independent - > at least in the sense that I can reorder them via rebase with no > conflicts, and the code builds at each commit in either orientation. I > think this implies they're easier to review separately, rather than > squashed. > > I don't have a strong feeling about the order. I slightly prefer > swapping them compared to this v4 series: first introduce minor > faults, then introduce CONTINUE. > > Since Peter also has no strong opinion, and Hugh it sounds like you > prefer it the other way around, I'll swap them as we had in some > previous version of this series: first introduce minor faults, then > introduce CONTINUE. Yes I have no strong opinion, but that's probably the least I prefer. :-) Because you'll declare UFFD_FEATURE_MINOR_SHMEM and enable this feature without the feature being completely implemented (without UFFDIO_CONTINUE, it's not complete since no one will be able to resolve that minor fault). Not a big deal anyway, but since we're at it... Basically I think three things to do for minor shmem support: (1) UFFDIO_CONTINUE (resolving path) (2) Handle fault path for shmem minor fault (faulting path) (3) Enablement of UFFD_FEATURE_MINOR_SHMEM (from which point, user can detect and enable it) I have no preference on how you'd like to merge these steps (right now you did 1 first, then 2+3 later; or as Hugh suggested do 1+2+3 together), but I'd still hope item 3 should always be the last, if possible... Thanks, -- Peter Xu