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=-6.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 20175C432BE for ; Tue, 31 Aug 2021 01:56:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 984F06101C for ; Tue, 31 Aug 2021 01:56:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 984F06101C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id E08DC6B0071; Mon, 30 Aug 2021 21:56:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D910E6B0072; Mon, 30 Aug 2021 21:56:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C31908D0001; Mon, 30 Aug 2021 21:56:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id AEE7F6B0071 for ; Mon, 30 Aug 2021 21:56:08 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 6066B180AE7F3 for ; Tue, 31 Aug 2021 01:56:08 +0000 (UTC) X-FDA: 78533710416.16.7F8214F Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf23.hostedemail.com (Postfix) with ESMTP id 906E9900009B for ; Tue, 31 Aug 2021 01:56:07 +0000 (UTC) Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Gz9Cp0018z8wNC; Tue, 31 Aug 2021 09:51:49 +0800 (CST) Received: from [10.174.178.75] (10.174.178.75) by dggeme703-chm.china.huawei.com (10.1.199.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.8; Tue, 31 Aug 2021 09:56:03 +0800 Subject: Re: [PATCH 6/6] mm/page_alloc.c: avoid allocating highmem pages via alloc_pages_exact_nid() To: Matthew Wilcox CC: , , , , , , References: <20210830141051.64090-1-linmiaohe@huawei.com> <20210830141051.64090-7-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Tue, 31 Aug 2021 09:56:02 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.75] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggeme703-chm.china.huawei.com (10.1.199.99) X-CFilter-Loop: Reflected Authentication-Results: imf23.hostedemail.com; dkim=none; spf=pass (imf23.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=none) header.from=huawei.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 906E9900009B X-Stat-Signature: ofrwg36yghr8ifwgtht4rajwf1sjq64g X-HE-Tag: 1630374967-265984 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 2021/8/30 22:24, Matthew Wilcox wrote: > On Mon, Aug 30, 2021 at 10:10:51PM +0800, Miaohe Lin wrote: >> Don't use with __GFP_HIGHMEM because page_address() cannot represent >> highmem pages without kmap(). Newly allocated pages would leak as >> page_address() will return NULL for highmem pages here. But It works >> now because the only caller does not specify __GFP_HIGHMEM now. > > This is a misunderstanding of how alloc_pages_exact() / > alloc_pages_exact_nid() work. You simply can't call them with > GFP_HIGHMEM. > Yep, they can't work with GFP_HIGHMEM. So IMO it might be better to get rid of GFP_HIGHMEM explicitly or add a comment to clarify this situation to avoid future misbehavior. But this may be a unnecessary worry... Do you prefer to not change anything here? Many thanks. > If you really must change anything here, > s/__GFP_COMP/(__GFP_COMP|__GFP_HIGHMEM)/g throughout both > alloc_pages_exact() and alloc_pages_exact_nid(). > . >