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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY 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 74FF1C433E0 for ; Mon, 10 Aug 2020 23:05:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 42AD820734 for ; Mon, 10 Aug 2020 23:05:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 42AD820734 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DB8CA6B0006; Mon, 10 Aug 2020 19:05:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D69936B0007; Mon, 10 Aug 2020 19:05:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CA72A6B0008; Mon, 10 Aug 2020 19:05:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0252.hostedemail.com [216.40.44.252]) by kanga.kvack.org (Postfix) with ESMTP id B6F386B0006 for ; Mon, 10 Aug 2020 19:05:51 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 76FC78248047 for ; Mon, 10 Aug 2020 23:05:51 +0000 (UTC) X-FDA: 77136193302.18.tax38_0c07d7726fde Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id 45CD4100ED0FD for ; Mon, 10 Aug 2020 23:05:51 +0000 (UTC) X-HE-Tag: tax38_0c07d7726fde X-Filterd-Recvd-Size: 3145 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Mon, 10 Aug 2020 23:05:49 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04397;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U5Pi6VE_1597100744; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U5Pi6VE_1597100744) by smtp.aliyun-inc.com(127.0.0.1); Tue, 11 Aug 2020 07:05:45 +0800 Date: Tue, 11 Aug 2020 07:05:44 +0800 From: Wei Yang To: Mike Kravetz Cc: Wei Yang , Baoquan He , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/10] mm/hugetlb: make sure to get NULL when list is empty Message-ID: <20200810230544.GA27669@L-31X9LVDL-1304.local> Reply-To: Wei Yang References: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com> <20200807091251.12129-3-richard.weiyang@linux.alibaba.com> <20200807124951.GM14854@MiWiFi-R3L-srv> <20200807142800.GA14692@L-31X9LVDL-1304.local> <9cf6749d-3a0a-480a-ef76-ae8cf5413a90@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9cf6749d-3a0a-480a-ef76-ae8cf5413a90@oracle.com> X-Rspamd-Queue-Id: 45CD4100ED0FD X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 10, 2020 at 01:28:46PM -0700, Mike Kravetz wrote: >On 8/7/20 7:28 AM, Wei Yang wrote: >> On Fri, Aug 07, 2020 at 08:49:51PM +0800, Baoquan He wrote: >>> On 08/07/20 at 05:12pm, Wei Yang wrote: >>>> list_first_entry() may not return NULL even when the list is empty. >>>> >>>> Let's make sure the behavior by using list_first_entry_or_null(), >>>> otherwise it would corrupt the list. >>>> >>>> Signed-off-by: Wei Yang >>>> --- >>>> mm/hugetlb.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>> index 62ec74f6d03f..0a2f3851b828 100644 >>>> --- a/mm/hugetlb.c >>>> +++ b/mm/hugetlb.c >>>> @@ -237,7 +237,8 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to) >>>> VM_BUG_ON(resv->region_cache_count <= 0); >>> >>> >>> We have had above line, is it possible to be NULL from list_first_entry? >>> >>>> >>>> resv->region_cache_count--; >>>> - nrg = list_first_entry(&resv->region_cache, struct file_region, link); >>>> + nrg = list_first_entry_or_null(&resv->region_cache, >>>> + struct file_region, link); >>>> VM_BUG_ON(!nrg); >> >> Or we can remove this VM_BUG_ON()? >> > >I would prefer that we just remove the 'VM_BUG_ON(!nrg)'. Code elsewhere >is responsible for making sure there is ALWAYS an entry in the cache. That >is why the 'VM_BUG_ON(resv->region_cache_count <= 0)' is at the beginning >of the routine. Sure, will change to this. > >-- >Mike Kravetz -- Wei Yang Help you, Help me