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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 8A8A6C433E0 for ; Tue, 4 Aug 2020 19:17:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 55F712086A for ; Tue, 4 Aug 2020 19:17:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="huSDEUM7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 55F712086A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A89378D0183; Tue, 4 Aug 2020 15:17:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A38718D0081; Tue, 4 Aug 2020 15:17:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 926C18D0183; Tue, 4 Aug 2020 15:17:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0112.hostedemail.com [216.40.44.112]) by kanga.kvack.org (Postfix) with ESMTP id 7AD5C8D0081 for ; Tue, 4 Aug 2020 15:17:43 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id CEB1F3622 for ; Tue, 4 Aug 2020 19:17:42 +0000 (UTC) X-FDA: 77113845564.21.party80_1a0cc6e26fa8 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id 95C4D180442CB for ; Tue, 4 Aug 2020 19:17:41 +0000 (UTC) X-HE-Tag: party80_1a0cc6e26fa8 X-Filterd-Recvd-Size: 3683 Received: from hqnvemgate25.nvidia.com (hqnvemgate25.nvidia.com [216.228.121.64]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Tue, 4 Aug 2020 19:17:40 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 04 Aug 2020 12:16:50 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 04 Aug 2020 12:17:39 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 04 Aug 2020 12:17:39 -0700 Received: from [10.2.58.124] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 4 Aug 2020 19:17:35 +0000 Subject: Re: [PATCH] mm, dump_page: do not crash with bad compound_page() To: Matthew Wilcox CC: , , , , , , , "Kirill A . Shutemov" References: <20200804161414.GG23808@casper.infradead.org> <20200804183943.1244828-1-jhubbard@nvidia.com> <20200804184856.GI23808@casper.infradead.org> From: John Hubbard Message-ID: Date: Tue, 4 Aug 2020 12:17:34 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200804184856.GI23808@casper.infradead.org> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1596568610; bh=EHwpclO/SZMGkYijEZg6asCKYE8M5YnFZrDWai8n6v8=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=huSDEUM7sX6vyTBEb4nMBOobZ9eYG5hIrNQhpphI7yN57hq14oehPUaD73Ht4Kk8c ryPHuD9hgCffbE0W2f4jRiJq3sdeBFcs3zB7Swu6B1jQjkk5k46MV+QX8P8nbbOnDN 1V6TCBNB5kMccAUFmqCeOqmp6+w/QduXMk6ZE3f7aM3FwrIhYkH9+5MyCrJXSC6gw6 Pm14vLMjVruvUkIh4/Zx0Cx4cuiadx2gIQkiVjXHjXXFtxESFhQgXCTqNs2o+t9OwQ N7wD7CtHHSsTbGSrDsW7e/wTRNcR+jYyg3x8uF17NxJIn5JERY193HwW17pt7T/9qx CRXlLtHPq7dHQ== X-Rspamd-Queue-Id: 95C4D180442CB X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: On 8/4/20 11:48 AM, Matthew Wilcox wrote: > On Tue, Aug 04, 2020 at 11:39:43AM -0700, John Hubbard wrote: >> +static inline int __compound_mapcount(struct page *page) >> +{ >> + page = compound_head(page); >> + return atomic_read(compound_mapcount_ptr(page)) + 1; >> +} > > I'd suggest instead: > > static inline int head_mapcount(struct page *head) > { > return atomic_read(compound_mapcount_ptr(head)) + 1; > } > >> +static inline int dump_page_compound_mapcount(struct page *page) >> +{ >> + if (WARN_ON_ONCE(!PageCompound(page))) >> + return 0; >> + return __compound_mapcount(page); >> } > > And just dropping this ... it shouldn't be used outside mm/debug.c anyway. Yes, that's cleaner. I'll send a v2 that is not a reply, so that Andrew can spot it more easily. OK to add your "Suggested-by:" to that? > > Thinking about it, we'll get the hint later that this is not to be trusted > when the flags from the page do not include 'head'. > Good point. I think this will work out pretty well, then. thanks, -- John Hubbard NVIDIA