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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A24FCC2D0BF for ; Fri, 6 Dec 2019 00:04:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5BE2F2173E for ; Fri, 6 Dec 2019 00:04:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="e4500oBY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5BE2F2173E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 09BBE6B12DF; Thu, 5 Dec 2019 19:04:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 04C116B12E0; Thu, 5 Dec 2019 19:04:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E7D386B12E1; Thu, 5 Dec 2019 19:04:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0018.hostedemail.com [216.40.44.18]) by kanga.kvack.org (Postfix) with ESMTP id CE74F6B12DF for ; Thu, 5 Dec 2019 19:04:12 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 987CB80178D3 for ; Fri, 6 Dec 2019 00:04:12 +0000 (UTC) X-FDA: 76232769144.17.time01_5ee4182d64d12 X-HE-Tag: time01_5ee4182d64d12 X-Filterd-Recvd-Size: 4926 Received: from hqemgate16.nvidia.com (hqemgate16.nvidia.com [216.228.121.65]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Fri, 6 Dec 2019 00:04:11 +0000 (UTC) Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqemgate16.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 05 Dec 2019 16:04:14 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Thu, 05 Dec 2019 16:04:10 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Thu, 05 Dec 2019 16:04:10 -0800 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 6 Dec 2019 00:04:09 +0000 Received: from [10.110.48.28] (10.124.1.5) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 6 Dec 2019 00:04:09 +0000 Subject: Re: [v3 PATCH] mm: move_pages: return valid node id in status if the page is already on the target node To: Qian Cai CC: Yang Shi , , , , , , , , , References: <2139CED9-6C12-48A5-BF61-F36923EB948E@lca.pw> From: John Hubbard X-Nvconfidentiality: public Message-ID: <22b5bfde-45be-95bd-5c98-2ab13302c107@nvidia.com> Date: Thu, 5 Dec 2019 16:04:09 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <2139CED9-6C12-48A5-BF61-F36923EB948E@lca.pw> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To DRHQMAIL107.nvidia.com (10.27.9.16) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1575590654; bh=HDeKv827CiSQ8RzNL5TATYMtNjIBTbYkbw7NU4jWVmc=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=e4500oBYXGcC8/koWSWB6iUl1ZFKQ4hL8OjrgxarlmjN3W3BViEVFRWaojft72r6L hQ6AOW5/XOYcPNF5NN+IXSM8oiN5AW8G2lcmXuIVwVuYThty7VJnJH9Urj1pbrwJh+ KPUFCPxXk6/ydWrdWtKS/WxIPbTHPVdj8IAGRAt1m5sHpqe4/aeYquIJK4YctH2Kvf WQ3wBtGo3e4IF6k09tVlTbaLO+9vY0vONgSfhnHIYykDP0w3kcfY+TnluubN9eov7b 2xpZkdqgepyjgEU2AilCc/axH7i+s6jq8CZvE2olsutb7UUchierqqoz6SkVlRiV6m RJ6UWykhSVDMg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.009743, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/5/19 3:58 PM, Qian Cai wrote: >=20 >=20 >> On Dec 5, 2019, at 6:24 PM, John Hubbard wrote: >> >> Let's check in the fix that is clearly correct and non-controversial, in= one >> patch. Then another patch can be created for the other case. This allows= forward >> progress and quick resolution of the user's bug report, while still deal= ing >> with all the problems. >> >> If you try to fix too many problems in one patch (and remember, sometime= s ">1" >> is too many), then things bog down. It's always a judgment call, but wha= t's=20 >> unfolding here is quite consistent with the usual judgment calls in this= area. >> >> I don't think anyone is saying, "don't work on the second problem", it's= just >> that it's less urgent, due to no reports from the field. If you are pass= ionate >> about fixing the second problem (and are ready and willing to handle the= fallout >> from user space, if it occurs), then I'd encourage you to look into it. >> >> It could turn out to be one of those "cannot change this because user sp= ace expectations >> have baked and hardened, and changes would break user space" situations,= just to >> warn you in advance, though. >=20 > There is no need to paper over the underlying issue. One can think there = is only one problem. The way move_pages() deal with pages are already in th= e desired node. Then, I don=E2=80=99t see there is any controversy that it = was broken for so long and just restore it to according to the manpage. If = you worried about people has already depended on the broken behavior, it co= uld stay in linux-next for many releases to gather feedback. In any case, I= don=E2=80=99t see it need to hurry to fix this until someone can show the = real world use case for it apart from some random test code. >=20 Felix's code is not random test code. It's code he wrote and he expected it= to work. Anyway, I've explained what I want here, and done my best to explain it. So= I'm=20 dropping off now. :) thanks, --=20 John Hubbard NVIDIA