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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 A3CBCC433E0 for ; Fri, 7 Aug 2020 12:50:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C70320866 for ; Fri, 7 Aug 2020 12:50:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Aw66hVFQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726015AbgHGMuB (ORCPT ); Fri, 7 Aug 2020 08:50:01 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:52602 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725792AbgHGMuB (ORCPT ); Fri, 7 Aug 2020 08:50:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596804599; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PFMpCHyvwGa8Ud+s2C9Dt9Z5yJ/jvYtcmcoYAlDhqCc=; b=Aw66hVFQX4h25qqtTGv5aa+53FugHT0tozMBbqIiDnnuA/uxcE6/iMO+Pvu6zCHzJuLD3s p2tXSUG9q/UBB7armuwhOt8Acz7lsp+NKZUGiZD4FFNyRQgA5BUjnXXva7m07HgK0IUoBc 3pZE9fWU2HvG1TSrda4MMZgKhZbbF3o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-467-AulHBLTONrOL5hk-Wkzxcw-1; Fri, 07 Aug 2020 08:49:58 -0400 X-MC-Unique: AulHBLTONrOL5hk-Wkzxcw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BA569800404; Fri, 7 Aug 2020 12:49:56 +0000 (UTC) Received: from localhost (ovpn-12-31.pek2.redhat.com [10.72.12.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 547355DA33; Fri, 7 Aug 2020 12:49:54 +0000 (UTC) Date: Fri, 7 Aug 2020 20:49:51 +0800 From: Baoquan He To: Wei Yang Cc: mike.kravetz@oracle.com, 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: <20200807124951.GM14854@MiWiFi-R3L-srv> References: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com> <20200807091251.12129-3-richard.weiyang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200807091251.12129-3-richard.weiyang@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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); > list_del(&nrg->link); > > -- > 2.20.1 (Apple Git-117) > >