From nobody Tue Apr 28 02:28:04 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C56A0C43334 for ; Tue, 7 Jun 2022 14:41:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245740AbiFGOl4 (ORCPT ); Tue, 7 Jun 2022 10:41:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245742AbiFGOlx (ORCPT ); Tue, 7 Jun 2022 10:41:53 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 033A4BE176 for ; Tue, 7 Jun 2022 07:41:52 -0700 (PDT) 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 Content-Transfer-Encoding: quoted-printable 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 =3D=3D head_pfn + 2) - prep_compound_head(head, order); } + prep_compound_head(head, order); } =20 void __ref memmap_init_zone_device(struct zone *zone, --=20 2.23.0