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 7497AC433E6 for ; Wed, 20 Jan 2021 02:10:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BA4BF2245C for ; Wed, 20 Jan 2021 02:10:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA4BF2245C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 00C536B0005; Tue, 19 Jan 2021 21:10:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EFFBD6B0006; Tue, 19 Jan 2021 21:10:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E15246B0007; Tue, 19 Jan 2021 21:10:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0104.hostedemail.com [216.40.44.104]) by kanga.kvack.org (Postfix) with ESMTP id CA2FC6B0005 for ; Tue, 19 Jan 2021 21:10:15 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 78508180AD81F for ; Wed, 20 Jan 2021 02:10:15 +0000 (UTC) X-FDA: 77724523590.17.mark62_0f0ec0327556 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 59DE2180D0186 for ; Wed, 20 Jan 2021 02:10:15 +0000 (UTC) X-HE-Tag: mark62_0f0ec0327556 X-Filterd-Recvd-Size: 3384 Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Wed, 20 Jan 2021 02:10:14 +0000 (UTC) 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 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: 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.