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=-17.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 94825C432BE for ; Thu, 2 Sep 2021 12:45:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7375E60F21 for ; Thu, 2 Sep 2021 12:45:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344669AbhIBMqy (ORCPT ); Thu, 2 Sep 2021 08:46:54 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:19003 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344561AbhIBMqw (ORCPT ); Thu, 2 Sep 2021 08:46:52 -0400 Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4H0gY02qcjzbkW4; Thu, 2 Sep 2021 20:41:56 +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; Thu, 2 Sep 2021 20:45:51 +0800 Subject: Re: [PATCH v2 5/5] mm/page_alloc.c: avoid allocating highmem pages via alloc_pages_exact[_nid] To: David Hildenbrand , CC: , , , , , References: <20210902121242.41607-1-linmiaohe@huawei.com> <20210902121242.41607-6-linmiaohe@huawei.com> <1ef3dc5d-7eb9-90a5-afbf-f551afcf7d8b@redhat.com> From: Miaohe Lin Message-ID: <0a14f77f-2242-e3e3-611b-6d23fdf51756@huawei.com> Date: Thu, 2 Sep 2021 20:45:51 +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: <1ef3dc5d-7eb9-90a5-afbf-f551afcf7d8b@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/9/2 20:16, David Hildenbrand wrote: > On 02.09.21 14:12, 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 callers do not specify __GFP_HIGHMEM now. >> >> Signed-off-by: Miaohe Lin >> --- >>   mm/page_alloc.c | 8 ++++---- >>   1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 9c09dcb24149..e1d0e27d005a 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -5614,8 +5614,8 @@ void *alloc_pages_exact(size_t size, gfp_t gfp_mask) >>       unsigned int order = get_order(size); >>       unsigned long addr; >>   -    if (WARN_ON_ONCE(gfp_mask & __GFP_COMP)) >> -        gfp_mask &= ~__GFP_COMP; >> +    if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM))) >> +        gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM); >>         addr = __get_free_pages(gfp_mask, order); >>       return make_alloc_exact(addr, order, size); >> @@ -5639,8 +5639,8 @@ void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask) >>       unsigned int order = get_order(size); >>       struct page *p; >>   -    if (WARN_ON_ONCE(gfp_mask & __GFP_COMP)) >> -        gfp_mask &= ~__GFP_COMP; >> +    if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM))) >> +        gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM); >>         p = alloc_pages_node(nid, gfp_mask, order); >>       if (!p) >> > > Ideally we would convert this WARN_ON_ONCE() to pr_warn_once(), but I guess this really never ever happens on a production system and would get caught early while testing. > This patch is mainly intended to make it clear that we simply can't call alloc_pages_exact[_nid] with GFP_HIGHMEM. So this warning would never ever happens. > Reviewed-by: David Hildenbrand > Many thanks for your review and reply.