From patchwork Tue Jun 7 14:41:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12872024 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF85BCCA47C for ; Tue, 7 Jun 2022 14:41:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 855086B0075; Tue, 7 Jun 2022 10:41:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 803C06B0074; Tue, 7 Jun 2022 10:41:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F2706B0075; Tue, 7 Jun 2022 10:41:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 5DFF26B0073 for ; Tue, 7 Jun 2022 10:41:54 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 3331C60F32 for ; Tue, 7 Jun 2022 14:41:54 +0000 (UTC) X-FDA: 79551704148.27.63AE98E Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf10.hostedemail.com (Postfix) with ESMTP id E5D73C002E for ; Tue, 7 Jun 2022 14:41:02 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4LHY0x4glYzgYXW; Tue, 7 Jun 2022 22:40:01 +0800 (CST) Received: from huawei.com (10.175.124.27) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 7 Jun 2022 22:41:49 +0800 From: Miaohe Lin To: CC: , , Subject: [PATCH] mm/page_alloc: make calling prep_compound_head more reliable Date: Tue, 7 Jun 2022 22:41:57 +0800 Message-ID: <20220607144157.36411-1-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Authentication-Results: imf10.hostedemail.com; dkim=none; spf=pass (imf10.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: E5D73C002E X-Rspam-User: X-Stat-Signature: 188yhwba6gbts99uc3q39c7xqy1j1kxf X-HE-Tag: 1654612862-892684 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: compound_pincount_ptr is stored at first tail page instead of second tail page now. And if it or some other field changes again in the future, data overwritten might happen. Calling prep_compound_head() outside the loop to prevent such possible issue. No functional change intended. Signed-off-by: Miaohe Lin --- mm/page_alloc.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0243a21e69b1..fc3770f28d1a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6772,17 +6772,8 @@ static void __ref memmap_init_compound(struct page *head, __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); prep_compound_tail(head, pfn - head_pfn); set_page_count(page, 0); - - /* - * The first tail page stores compound_mapcount_ptr() and - * compound_order() and the second tail page stores - * compound_pincount_ptr(). Call prep_compound_head() after - * the first and second tail pages have been initialized to - * not have the data overwritten. - */ - if (pfn == head_pfn + 2) - prep_compound_head(head, order); } + prep_compound_head(head, order); } void __ref memmap_init_zone_device(struct zone *zone,