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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C8D29C43461 for ; Wed, 5 May 2021 01:34:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 74F9E6140F for ; Wed, 5 May 2021 01:34:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74F9E6140F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 122EB8D002A; Tue, 4 May 2021 21:34:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0AECA8D0003; Tue, 4 May 2021 21:34:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E6A1D8D002A; Tue, 4 May 2021 21:34:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0254.hostedemail.com [216.40.44.254]) by kanga.kvack.org (Postfix) with ESMTP id C21CF8D0003 for ; Tue, 4 May 2021 21:34:37 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 836F18777 for ; Wed, 5 May 2021 01:34:37 +0000 (UTC) X-FDA: 78105457794.04.9A56562 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf30.hostedemail.com (Postfix) with ESMTP id 904B3E000105 for ; Wed, 5 May 2021 01:34:12 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 38D276140E; Wed, 5 May 2021 01:34:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620178476; bh=+kxJsZ3bUkrf1i/p3WMPwrvJzcXe4xUv631W5mLCy44=; h=Date:From:To:Subject:In-Reply-To:From; b=jhr+LgmHjsEhh3t4RqIMcp9Z9eRL7gyV5vAnhHNATHma15sh8gY1AO5QkmS7CGSmH a7tJkSQErz3Cp5Jo/75lfr0dgZHS05Y4xfmTD+2dp+7TC5UE8el6hZK+NvXVeSHBEN cVcFhgOIytJkfDdE7LVptBlZHwib4yyiFtRGId3A= Date: Tue, 04 May 2021 18:34:35 -0700 From: Andrew Morton To: akpm@linux-foundation.org, linfeilong@huawei.com, linmiaohe@huawei.com, linux-mm@kvack.org, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 036/143] mm/hugeltb: clarify (chg - freed) won't go negative in hugetlb_unreserve_pages() Message-ID: <20210505013435.BSlxlrD-G%akpm@linux-foundation.org> In-Reply-To: <20210504183219.a3cc46aee4013d77402276c5@linux-foundation.org> User-Agent: s-nail v14.8.16 Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=jhr+LgmH; dmarc=none; spf=pass (imf30.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam03 X-Stat-Signature: 6w6k6wmhbpdkqtwxu573f9d68oqtwcso X-Rspamd-Queue-Id: 904B3E000105 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620178452-697780 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: From: Miaohe Lin Subject: mm/hugeltb: clarify (chg - freed) won't go negative in hugetlb_unreserve_pages() The resv_map could be NULL since this routine can be called in the evict inode path for all hugetlbfs inodes and we will have chg = 0 in this case. But (chg - freed) won't go negative as Mike pointed out: "If resv_map is NULL, then no hugetlb pages can be allocated/associated with the file. As a result, remove_inode_hugepages will never find any huge pages associated with the inode and the passed value 'freed' will always be zero." Add a comment clarifying this to make it clear and also avoid confusion. Link: https://lkml.kernel.org/r/20210410072348.20437-4-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Cc: Feilong Lin Cc: Mike Kravetz Signed-off-by: Andrew Morton --- mm/hugetlb.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/hugetlb.c~mm-hugeltb-clarify-chg-freed-wont-go-negative-in-hugetlb_unreserve_pages +++ a/mm/hugetlb.c @@ -5267,6 +5267,9 @@ long hugetlb_unreserve_pages(struct inod /* * If the subpool has a minimum size, the number of global * reservations to be released may be adjusted. + * + * Note that !resv_map implies freed == 0. So (chg - freed) + * won't go negative. */ gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed)); hugetlb_acct_memory(h, -gbl_reserve); _