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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CF0EC3DA7A for ; Tue, 3 Jan 2023 01:58:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236592AbjACB6m (ORCPT ); Mon, 2 Jan 2023 20:58:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232893AbjACB6j (ORCPT ); Mon, 2 Jan 2023 20:58:39 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3494127 for ; Mon, 2 Jan 2023 17:58:38 -0800 (PST) Received: from dggpemm500001.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4NmG863QvMzJqnq; Tue, 3 Jan 2023 09:57:26 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Tue, 3 Jan 2023 09:58:37 +0800 Message-ID: Date: Tue, 3 Jan 2023 09:58:36 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2] mm: huge_memory: convert split_huge_pages_all() to use a folio Content-Language: en-US To: Andrew Morton CC: , , References: <20221230093020.9664-1-wangkefeng.wang@huawei.com> <20221230134535.240f49e0ad8bf6d82f8cc393@linux-foundation.org> From: Kefeng Wang In-Reply-To: <20221230134535.240f49e0ad8bf6d82f8cc393@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/12/31 5:45, Andrew Morton wrote: > On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang wrote: > >> Straightforwardly convert split_huge_pages_all() to use a folio. >> >> ... >> >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void) >> { >> struct zone *zone; >> struct page *page; >> + struct folio *folio; >> unsigned long pfn, max_zone_pfn; >> unsigned long total = 0, split = 0; >> >> @@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void) >> int nr_pages; >> >> page = pfn_to_online_page(pfn); >> - if (!page || !get_page_unless_zero(page)) >> + if (!page || PageTail(page)) >> + continue; >> + folio = page_folio(page); >> + if (!folio_try_get(folio)) >> continue; >> >> - if (zone != page_zone(page)) >> + if (unlikely(page_folio(page) != folio)) >> + goto next; >> + >> + if (zone != folio_zone(folio)) >> goto next; > > I'm still not understanding the above hunk. Why is the > "page_folio(page) != folio" check added? Should it be commented? There is a comment in try_get_folio(), is it enough?