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=-15.3 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 CA88FC433ED for ; Wed, 28 Apr 2021 08:23:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87126613CE for ; Wed, 28 Apr 2021 08:23:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237172AbhD1IYM (ORCPT ); Wed, 28 Apr 2021 04:24:12 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:17067 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236961AbhD1IYL (ORCPT ); Wed, 28 Apr 2021 04:24:11 -0400 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FVWmS4HTwz16MPc; Wed, 28 Apr 2021 16:20:56 +0800 (CST) Received: from [10.174.176.174] (10.174.176.174) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.498.0; Wed, 28 Apr 2021 16:23:22 +0800 Subject: Re: [PATCH 2/5] mm/huge_memory.c: use page->deferred_list To: Anshuman Khandual , CC: , , , , , , , , , , , , References: <20210427133214.2270207-1-linmiaohe@huawei.com> <20210427133214.2270207-3-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <2cda7d1a-d769-2635-24ce-928e33d6bfcc@huawei.com> Date: Wed, 28 Apr 2021 16:23:21 +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: [10.174.176.174] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/4/28 11:07, Anshuman Khandual wrote: > > On 4/27/21 7:02 PM, Miaohe Lin wrote: >> Now that we can represent the location of ->deferred_list instead of >> ->mapping + ->index, make use of it to improve readability. > > Could you please explain how page->deferred_list and page->mapping > are interchangeable here ? It's because there is a union in struct page: union { struct { struct list_head lru; struct address_space *mapping; pgoff_t index; unsigned long private; }; struct { unsigned long _compound_pad_1; atomic_t hpage_pinned_refcount; struct list_head *deferred_list*; }; }; And initially there is no deferred_list and it's added via commit 66a6ffd2af42 ("mm: combine first three unions in struct page"). Also commit fa3015b7eed5 ("mm: use page->deferred_list") did the similar cleanup. Am I expected to add these to the commit log? Many thanks. > >> >> Signed-off-by: Miaohe Lin >> --- >> mm/huge_memory.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 63ed6b25deaa..76ca1eb2a223 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2868,7 +2868,7 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, >> spin_lock_irqsave(&ds_queue->split_queue_lock, flags); >> /* Take pin on all head pages to avoid freeing them under us */ >> list_for_each_safe(pos, next, &ds_queue->split_queue) { >> - page = list_entry((void *)pos, struct page, mapping); >> + page = list_entry((void *)pos, struct page, deferred_list); >> page = compound_head(page); >> if (get_page_unless_zero(page)) { >> list_move(page_deferred_list(page), &list); >> @@ -2883,7 +2883,7 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, >> spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); >> >> list_for_each_safe(pos, next, &list) { >> - page = list_entry((void *)pos, struct page, mapping); >> + page = list_entry((void *)pos, struct page, deferred_list); >> if (!trylock_page(page)) >> goto next; >> /* split_huge_page() removes page from list on success */ >> > . >