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=-14.8 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1, USER_IN_DEF_DKIM_WL 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 2EF01C433B4 for ; Fri, 14 May 2021 07:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0CAA26140F for ; Fri, 14 May 2021 07:07:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232410AbhENHJE (ORCPT ); Fri, 14 May 2021 03:09:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232078AbhENHJC (ORCPT ); Fri, 14 May 2021 03:09:02 -0400 Received: from mail-pg1-x52a.google.com (mail-pg1-x52a.google.com [IPv6:2607:f8b0:4864:20::52a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91FBCC061574 for ; Fri, 14 May 2021 00:07:51 -0700 (PDT) Received: by mail-pg1-x52a.google.com with SMTP id j12so17447786pgh.7 for ; Fri, 14 May 2021 00:07:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=uMgRMGg/r3gIQINvH+QzQw4VB9eKfNkU/NWagyALQy0=; b=PbVOBlIX5vaNdsa+smKUweNt1LFR3XYJHTQMw1vBkxnXZxn4mb0CHtm+PJwGXlspIi AVZuIhwVKu9c1KehnCjg7xYut3FJp6vO437EX+SJRPW74HPYsOzDElqTDOPvjs6t/x2Z Er6+pGXd74YtlJNXGZVXTTTIMKQFldIeB39fR6md//OrAqD15tctErLDh9FilL/LKgzP +NrGrlqa3hVMGB7xFRYRamHzDUigJHmc1x9cJ6th1wyZU+B9VCpL5XVnXrkduOCoQdYW Hob5oKcfVRtACnBf3/PC8dM6TLAF4J6t1efJblLyO6YM3XOhrAv93inv/Y0VAFD09T57 OA4Q== 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:in-reply-to:message-id :references:user-agent:mime-version; bh=uMgRMGg/r3gIQINvH+QzQw4VB9eKfNkU/NWagyALQy0=; b=LsYbe2wBGvF2yllTzhP3vB49ffRNce719o2WQVJ/1nKsf4Eh9E8mkyjNIBY+SAvJUJ E/gWsvu/7qBbQR0GH41xklEHE1JX0szazDqSNi04H87l33kscNmMNg3o+Pyt5PPFuCNT v2i7hodeXmD2Jv4xm8YR1zP07xCRVZhkmqgLFEPTwv68ZI2ncqidhh4Wz+5o0pA6yGtL iBcspa4AVwsEJxPoSKAwpSJjP5DZoZmABXT3ke/QAsTc9Xp0Jaob2X5/jyfI8hQ8EQ4D DZpC1VTM2tWfL2Knwnzi7E6JnAWdsjeEC0KlVnG6Sr+bbTXydCe6B8ahr+xwTl1NAiQT COyA== X-Gm-Message-State: AOAM530awFeRPLVB6OTov8hwpPrId4NpLOtdzQV3xfLn6FzOxZGdMjzb QnkHz1LKQ/mS6ZFCFeDrfpnXpQ== X-Google-Smtp-Source: ABdhPJwAVGQcyFu8huddUFoRGDzEvr7xGXtt8NmG/sXBUnLfl67u8rYlL3910hnQ0PeqKG/ewx893w== X-Received: by 2002:a63:1165:: with SMTP id 37mr45959674pgr.295.1620976070717; Fri, 14 May 2021 00:07:50 -0700 (PDT) Received: from eggly.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id n11sm3460701pfu.121.2021.05.14.00.07.49 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Fri, 14 May 2021 00:07:50 -0700 (PDT) Date: Fri, 14 May 2021 00:07:38 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Peter Xu cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Nadav Amit , Miaohe Lin , Mike Rapoport , Andrea Arcangeli , Jerome Glisse , Mike Kravetz , Jason Gunthorpe , Matthew Wilcox , Andrew Morton , Axel Rasmussen , "Kirill A . Shutemov" Subject: Re: [PATCH v2 00/24] userfaultfd-wp: Support shmem and hugetlbfs In-Reply-To: Message-ID: References: <20210427161317.50682-1-peterx@redhat.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 12 May 2021, Peter Xu wrote: > On Tue, Apr 27, 2021 at 12:12:53PM -0400, Peter Xu wrote: > > This is v2 of uffd-wp shmem & hugetlbfs support, which completes uffd-wp as a > > kernel full feature, as it only supports anonymous before this series. > > Ping.. > > Thinking about a repost, as this series shouldn't be able to apply after we've > got more relevant patches into -mm. E.g., the full minor fault, and also some > small stuff like pagemap, as we need one more patch to support shmem/hugetlbfs > too. > > Hugh, haven't received any further comment from you on shmem side (or on the > general idea). It would be great to still have some of your input. > > Let me know if you prefer to read a fresh new version otherwise. I am very sorry to let you down, Peter, repeatedly; but it is now very clear that I shall *never* have time to review your patchset - I am too slow, have too much else to attend to, and take too long each time to sink myself deep enough into userfaultfd. I realize that you're being considerate, and expecting no more than a few comments from me, rather than asking for formal review; but it's still too much for me to get into. The only reason I was involved at all, was when you were wondering how to handle the pagetable entries for shmem. I suggested one encoding, Andrea suggested slightly differently: Andrea's was more elegant (no "swap type" required), and it looked like you went with his - good. I wonder whether you noticed https://lore.kernel.org/linux-mm/20210407084238.20443-2-apopple@nvidia.com/ which might interfere. I've had no more time to look at that than yours, so no opinion on it (and I don't know what happened to it after that). Please keep uppermost in mind when modifying mm/shmem.c for userfaultfd, the difference between shared and private; and be on guard against the ways in which CONFIG_USERFAULTFD=y might open a door to abuse. Thanks, Hugh