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 53554C433ED for ; Fri, 14 May 2021 07:07:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B6C2E6140F for ; Fri, 14 May 2021 07:07:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6C2E6140F Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 435E76B0036; Fri, 14 May 2021 03:07:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3BE3D6B006E; Fri, 14 May 2021 03:07:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 214316B0070; Fri, 14 May 2021 03:07:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0224.hostedemail.com [216.40.44.224]) by kanga.kvack.org (Postfix) with ESMTP id E10406B0036 for ; Fri, 14 May 2021 03:07:52 -0400 (EDT) Received: from smtpin35.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 7F2928249980 for ; Fri, 14 May 2021 07:07:52 +0000 (UTC) X-FDA: 78138956784.35.94A7DE8 Received: from mail-pg1-f172.google.com (mail-pg1-f172.google.com [209.85.215.172]) by imf29.hostedemail.com (Postfix) with ESMTP id 57047FE for ; Fri, 14 May 2021 07:07:51 +0000 (UTC) Received: by mail-pg1-f172.google.com with SMTP id i5so18768133pgm.0 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=nAgBH1ObzvFRZ1t0XS1+7YUc7yFSKdV1K2dIxNWa+boE6+Wtj8GEXgi+ujdZ9Fd1LS ruEAQaw7caDCFHNpWz2xjm7diUrixYf7+mxJPpnmYBHJZz1fHEHMBczWm/RmQ+qNuPhq k4oZPDA/jMZWtdr/bcrNYEkFevIEzp7FAUhM86sBQIayn7vF7SxV04EOxvRsjjUqqP/t IIaDKUksqzKph71loVI/bKXV5NTbNSd/oevAeWcu/VSKl3SqR7m2CnZs72V6UEFF3uE4 8IDwnTPBvUzqDEvGIO3LgXQ1fPNrXGga0Wx6xIb6wkYlssmrpOvOXiuB84LU2SoISqez 4jIA== X-Gm-Message-State: AOAM533ZC8L38kKZTbxzy4eA9T2scheYyVq1zkYDs0Xkg6fiBjEfQBRg nhTwggTgne8M+A024PZoxrlWuA== 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 Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=PbVOBlIX; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf29.hostedemail.com: domain of hughd@google.com designates 209.85.215.172 as permitted sender) smtp.mailfrom=hughd@google.com X-Stat-Signature: y4jwi6kaxq8dqmp76hmgzrz7qpdrfymi X-Rspamd-Queue-Id: 57047FE X-Rspamd-Server: rspam02 X-HE-Tag: 1620976071-302748 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 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