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 0D94CC47096 for ; Thu, 3 Jun 2021 19:35:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 95A2E611CC for ; Thu, 3 Jun 2021 19:35:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95A2E611CC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=emersion.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D93416B0036; Thu, 3 Jun 2021 15:35:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D43AD6B006C; Thu, 3 Jun 2021 15:35:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BE41D6B006E; Thu, 3 Jun 2021 15:35:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0034.hostedemail.com [216.40.44.34]) by kanga.kvack.org (Postfix) with ESMTP id 8CA8C6B0036 for ; Thu, 3 Jun 2021 15:35:57 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 11DA4E0AE for ; Thu, 3 Jun 2021 19:35:57 +0000 (UTC) X-FDA: 78213417954.30.B5E67A8 Received: from mail-40134.protonmail.ch (mail-40134.protonmail.ch [185.70.40.134]) by imf21.hostedemail.com (Postfix) with ESMTP id 74043E0004EE for ; Thu, 3 Jun 2021 19:35:31 +0000 (UTC) Date: Thu, 03 Jun 2021 19:35:35 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=emersion.fr; s=protonmail3; t=1622748936; bh=upIN3rRVlmuGccakb3pkBawIHaqI8SnKPwFBlV2wP3A=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=ih7mvRTeDlgXaPIULSRAbKPIdZ9gIUzCeK3vte6y6mP23bMDrzDX/Sk0/vEeOrpuf J8GFqBTsHW24SKyj5MSoG+PkQPicFn7ty0v81/yNQDLSyDWhGPcrQ32+XDWiqZdYtV ztFTRmbt4a8ylZb3s0Cy9aHF/16s0JBBLsyeiAnKSkZL9fuOXi4QVLI2PhTNTaLZMd 904/8+WerJVMz1mnBlJMEXr2yj7w9LpjPPnk7yCcRdJIAmARpg93jg64mW5L1fMjRD U0+Pqsp0jVn+x5DN/ZAqdTOuPnBTT86gzF0OJYSVZd/7x5rTi++MsSMfXHX2bDEdvn choACIjT9vlYQ== To: Andy Lutomirski From: Simon Ser Cc: Linus Torvalds , Hugh Dickins , Ming Lin , Linux-MM , Linux Kernel Mailing List , linux-fsdevel , Linux API Reply-To: Simon Ser Subject: Re: [PATCH 2/2] mm: adds NOSIGBUS extension for out-of-band shmem read Message-ID: In-Reply-To: <1FD047D2-F5F3-4AC6-A4E4-DB8FB1568821@amacapital.net> References: <1FD047D2-F5F3-4AC6-A4E4-DB8FB1568821@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=emersion.fr header.s=protonmail3 header.b=ih7mvRTe; dmarc=pass (policy=none) header.from=emersion.fr; spf=pass (imf21.hostedemail.com: domain of contact@emersion.fr designates 185.70.40.134 as permitted sender) smtp.mailfrom=contact@emersion.fr X-Stat-Signature: hxw7zhyayxq7nsgtnfz5h7hsxw4f6ndn X-Rspamd-Queue-Id: 74043E0004EE X-Rspamd-Server: rspam02 X-HE-Tag: 1622748931-495744 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thursday, June 3rd, 2021 at 9:24 PM, Andy Lutomirski wrote: > I don=E2=80=99t understand the use case well enough to comment on whether= MAP_PRIVATE > is sufficient, but I=E2=80=99m with Hugh: if this feature is implemented = for > MAP_SHARED, it should be fully coherent. I've tried to explain what we'd need from user-space PoV in [1]. tl;dr the MAP_PRIVATE restriction would get us pretty far, even if it won't allow us to have all of the bells and whistles. [1]: https://lore.kernel.org/linux-mm/vs1Us2sm4qmfvLOqNat0-r16GyfmWzqUzQ4KH= bXJwEcjhzeoQ4sBTxx7QXDG9B6zk5AeT7FsNb3CSr94LaKy6Novh1fbbw8D_BBxYsbPLms=3D@e= mersion.fr/T/#mb321a8d39e824740877ba95f1df780ffd52c3862