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,URIBL_BLOCKED, 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 01AE3C433E0 for ; Wed, 20 Jan 2021 02:12:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B24922245C for ; Wed, 20 Jan 2021 02:12:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729342AbhATCMB (ORCPT ); Tue, 19 Jan 2021 21:12:01 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:11407 "EHLO szxga07-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726672AbhATCKy (ORCPT ); Tue, 19 Jan 2021 21:10:54 -0500 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4DL88c3QNYz7XfZ; Wed, 20 Jan 2021 10:09:04 +0800 (CST) Received: from [10.174.177.2] (10.174.177.2) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.498.0; Wed, 20 Jan 2021 10:10:09 +0800 Subject: Re: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve To: Mike Kravetz CC: , , Andrew Morton References: <20210116092644.42697-1-linmiaohe@huawei.com> <2900fea0-e77c-8c6a-1529-c95ded5319e6@oracle.com> From: Miaohe Lin Message-ID: <52159266-f3bf-1043-9f63-f6147355f043@huawei.com> Date: Wed, 20 Jan 2021 10:10:08 +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: <2900fea0-e77c-8c6a-1529-c95ded5319e6@oracle.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.2] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi: On 2021/1/20 2:41, Mike Kravetz wrote: > Please CC Andrew on hugetlb patches as they need to go through his tree. > > On 1/16/21 1:26 AM, Miaohe Lin wrote: >> The variable avoid_reserve is meaningless because we never changed its >> value and just passed it to alloc_huge_page(). So remove it to make code >> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc >> hugepage yet. > > One might argue that using a named variable makes the call to alloc_huge_page > more clear. I do not disagree with the change, However, there are some > subtle reasons why alloc_huge_page is called with 'avoid_reserve = 0' from > fallocate. Therefore, I would prefer that a comment be added above the call > in addition to this change. See below. > >> >> Signed-off-by: Miaohe Lin >> --- >> fs/hugetlbfs/inode.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c >> index 88751e35e69d..23ad6ed8b75f 100644 >> --- a/fs/hugetlbfs/inode.c >> +++ b/fs/hugetlbfs/inode.c >> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, >> */ >> struct page *page; >> unsigned long addr; >> - int avoid_reserve = 0; >> >> cond_resched(); >> >> @@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, >> } >> >> /* Allocate page and add to page cache */ > > Perhaps, change comment to read: > > /* > * Allocate page without setting the avoid_reserve argument. > * There certainly are no reserves associated with the > * pseudo_vma. However, there could be shared mappings with > * reserves for the file at the inode level. If we fallocate > * pages in these areas, we need to consume the reserves > * to keep reservation accounting consistent. > */ > Many thanks for detailed and excellent comment. Will do it in v2. Thanks again.