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[209.85.208.179]) by smtp.gmail.com with ESMTPSA id x1sm429754lfq.240.2021.06.03.12.15.55 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Jun 2021 12:15:55 -0700 (PDT) Received: by mail-lj1-f179.google.com with SMTP id c11so8506890ljd.6 for ; Thu, 03 Jun 2021 12:15:55 -0700 (PDT) X-Received: by 2002:a05:651c:1311:: with SMTP id u17mr626097lja.48.1622747755672; Thu, 03 Jun 2021 12:15:55 -0700 (PDT) MIME-Version: 1.0 References: <1622589753-9206-1-git-send-email-mlin@kernel.org> <1622589753-9206-3-git-send-email-mlin@kernel.org> <79a27014-5450-1345-9eea-12fc9ae25777@kernel.org> In-Reply-To: From: Linus Torvalds Date: Thu, 3 Jun 2021 12:15:39 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] mm: adds NOSIGBUS extension for out-of-band shmem read To: Hugh Dickins Cc: Ming Lin , Simon Ser , Linux-MM , Linux Kernel Mailing List , linux-fsdevel , Linux API Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 3, 2021 at 12:12 PM Linus Torvalds wrote: > > Yeah, if that's sufficient, then that original patch should just work as-is. To clarify: it obviously needs the VM_xyz flags things, but the VM_SHARED check in do_anonymous_page() is fine, and the whole issue with VM_MAYWRITE is entirely moot. MAP_PRIVATE works fine with zero pages even when writable - they get COW'ed properly, of course. Linus 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=-5.8 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 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 1C1B0C47082 for ; Thu, 3 Jun 2021 19:16:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 924DB613F4 for ; Thu, 3 Jun 2021 19:16:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 924DB613F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 015AE6B0036; Thu, 3 Jun 2021 15:16:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F307D6B006C; Thu, 3 Jun 2021 15:16:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD0D46B006E; Thu, 3 Jun 2021 15:16:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0147.hostedemail.com [216.40.44.147]) by kanga.kvack.org (Postfix) with ESMTP id A971C6B0036 for ; Thu, 3 Jun 2021 15:16:07 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 4BBC8181AC9CB for ; Thu, 3 Jun 2021 19:16:07 +0000 (UTC) X-FDA: 78213367974.27.D4D39DD Received: from mail-lj1-f170.google.com (mail-lj1-f170.google.com [209.85.208.170]) by imf24.hostedemail.com (Postfix) with ESMTP id 76600A0021D9 for ; Thu, 3 Jun 2021 19:15:44 +0000 (UTC) Received: by mail-lj1-f170.google.com with SMTP id bn21so8539776ljb.1 for ; Thu, 03 Jun 2021 12:15:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6CRsT8crQOoq4KK7EHvJ7QQM+oKI52My1kzGYaLGrfI=; b=R8VDVRcPoGt4k3cTxV+3sOakxWxFIWv9QitfEwkiZuFc+TePCnjK5n4i0LW5CY7vBE 13FlE07lfLUcNnJ843cb2LCV/zg8vLt0u8cwi/gVWfImNpe1FxwNQ+MJ/WaTmrDjfj+J vXkTFwqZubZn2FR3ewqOSGR+9hjtemq0rhKHo= 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=6CRsT8crQOoq4KK7EHvJ7QQM+oKI52My1kzGYaLGrfI=; b=iKGA8wrePF5KLjz74smVjUN2ehDlENAWLPDAK6DszZTE9Kx8wuH2Odn5BcXASv7zN+ ALtmIGpi7VU+7byiKiUt869evrwzvNJ9l26wQIfHhwipc1wqxUyObnrZVccJYLMmK3vn cBznd6+LqFG2VsJVBwC/bEhAMwzwErq0mSA3VZCjyO63SRzaRxe5IEVt/Irc7WehB7Z+ cm7VMl6U6dl5lhWkS3bbgQ73DehMkstXRR7H/xM0MHc9vDaV5cWPObl88BtmCJVxuuxk Sy2wDJMurNYXeYDqoF3NeOOwrHXV1fODtUqJ4MiNcfn+Alb0S31keAHCHQm9VdWOLbEF +kDA== X-Gm-Message-State: AOAM530CadScyOqVS+uluxNzmJZHlZ4J1mNif+RPqh/RZtgShf4wXFES iyESylOoUEoQB2iBXzkbJrjjuv0MoSALNwbL X-Google-Smtp-Source: ABdhPJyv1m1pSAmdYS9VseixD/WvB4aL9UMa0b7t6sYVb5SK+krH/wM6EZBw1cdLYN5LChvbp5lGkA== X-Received: by 2002:a05:651c:104e:: with SMTP id x14mr614683ljm.345.1622747756501; Thu, 03 Jun 2021 12:15:56 -0700 (PDT) Received: from mail-lj1-f176.google.com (mail-lj1-f176.google.com. [209.85.208.176]) by smtp.gmail.com with ESMTPSA id d3sm398932lfv.9.2021.06.03.12.15.55 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Jun 2021 12:15:56 -0700 (PDT) Received: by mail-lj1-f176.google.com with SMTP id u22so8498595ljh.7 for ; Thu, 03 Jun 2021 12:15:55 -0700 (PDT) X-Received: by 2002:a05:651c:1311:: with SMTP id u17mr626097lja.48.1622747755672; Thu, 03 Jun 2021 12:15:55 -0700 (PDT) MIME-Version: 1.0 References: <1622589753-9206-1-git-send-email-mlin@kernel.org> <1622589753-9206-3-git-send-email-mlin@kernel.org> <79a27014-5450-1345-9eea-12fc9ae25777@kernel.org> In-Reply-To: From: Linus Torvalds Date: Thu, 3 Jun 2021 12:15:39 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] mm: adds NOSIGBUS extension for out-of-band shmem read To: Hugh Dickins Cc: Ming Lin , Simon Ser , Linux-MM , Linux Kernel Mailing List , linux-fsdevel , Linux API Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 76600A0021D9 Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=R8VDVRcP; spf=temperror (imf24.hostedemail.com: error in processing during lookup of torvalds@linuxfoundation.org: DNS error) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=temperror reason="query timed out" header.from=linux-foundation.org (policy=temperror) X-Rspamd-Server: rspam04 X-Stat-Signature: udoynyyychiejm4fwuefn3atat9pkjcx X-HE-Tag: 1622747744-132596 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 Thu, Jun 3, 2021 at 12:12 PM Linus Torvalds wrote: > > Yeah, if that's sufficient, then that original patch should just work as-is. To clarify: it obviously needs the VM_xyz flags things, but the VM_SHARED check in do_anonymous_page() is fine, and the whole issue with VM_MAYWRITE is entirely moot. MAP_PRIVATE works fine with zero pages even when writable - they get COW'ed properly, of course. Linus