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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 C47A6C04ABB for ; Tue, 11 Sep 2018 14:08:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79BDF2087F for ; Tue, 11 Sep 2018 14:08:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 79BDF2087F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727798AbeIKTHq (ORCPT ); Tue, 11 Sep 2018 15:07:46 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:43068 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726798AbeIKTHp (ORCPT ); Tue, 11 Sep 2018 15:07:45 -0400 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w8BE5Uv7088483 for ; Tue, 11 Sep 2018 10:08:16 -0400 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0a-001b2d01.pphosted.com with ESMTP id 2meetv16a5-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 11 Sep 2018 10:08:15 -0400 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 11 Sep 2018 08:08:11 -0600 Received: from b03ledav002.gho.boulder.ibm.com (b03ledav002.gho.boulder.ibm.com [9.17.130.233]) by b03cxnp07028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w8BE8AVI56688714 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 11 Sep 2018 07:08:10 -0700 Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 36CA013604F; Tue, 11 Sep 2018 08:08:10 -0600 (MDT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BE989136051; Tue, 11 Sep 2018 08:08:08 -0600 (MDT) Received: from [9.152.99.211] (unknown [9.152.99.211]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTPS; Tue, 11 Sep 2018 08:08:08 -0600 (MDT) Subject: Re: [PATCH] memory_hotplug: fix the panic when memory end is not on the section boundary To: Pasha Tatashin , Michal Hocko , Mikhail Zaslonko Cc: "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "osalvador@suse.de" , "gerald.schaefer@de.ibm.com" References: <20180910123527.71209-1-zaslonko@linux.ibm.com> <20180910131754.GG10951@dhcp22.suse.cz> From: Zaslonko Mikhail Date: Tue, 11 Sep 2018 16:08:09 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18091114-0004-0000-0000-00001487E7DD X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009703; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01086780; UDB=6.00561133; IPR=6.00866791; MB=3.00023231; MTD=3.00000008; XFM=3.00000015; UTC=2018-09-11 14:08:13 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18091114-0005-0000-0000-000088C61226 Message-Id: <639fd656-033b-0fdb-a182-83d4acf7fe2b@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-09-11_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1809110145 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10.09.2018 15:46, Pasha Tatashin wrote: > > On 9/10/18 9:17 AM, Michal Hocko wrote: >> [Cc Pavel] >> >> On Mon 10-09-18 14:35:27, Mikhail Zaslonko wrote: >>> If memory end is not aligned with the linux memory section boundary, such >>> a section is only partly initialized. This may lead to VM_BUG_ON due to >>> uninitialized struct pages access from is_mem_section_removable() or >>> test_pages_in_a_zone() function. >>> >>> Here is one of the panic examples: >>> CONFIG_DEBUG_VM_PGFLAGS=y >>> kernel parameter mem=3075M >> OK, so the last memory section is not full and we have a partial memory >> block right? >> >>> page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) >> OK, this means that the struct page is not fully initialized. Do you >> have a specific place which has triggered this assert? >> >>> ------------[ cut here ]------------ >>> Call Trace: >>> ([<000000000039b8a4>] is_mem_section_removable+0xcc/0x1c0) >>> [<00000000009558ba>] show_mem_removable+0xda/0xe0 >>> [<00000000009325fc>] dev_attr_show+0x3c/0x80 >>> [<000000000047e7ea>] sysfs_kf_seq_show+0xda/0x160 >>> [<00000000003fc4e0>] seq_read+0x208/0x4c8 >>> [<00000000003cb80e>] __vfs_read+0x46/0x180 >>> [<00000000003cb9ce>] vfs_read+0x86/0x148 >>> [<00000000003cc06a>] ksys_read+0x62/0xc0 >>> [<0000000000c001c0>] system_call+0xdc/0x2d8 >>> >>> This fix checks if the page lies within the zone boundaries before >>> accessing the struct page data. The check is added to both functions. >>> Actually similar check has already been present in >>> is_pageblock_removable_nolock() function but only after the struct page >>> is accessed. >>> >> Well, I am afraid this is not the proper solution. We are relying on the >> full pageblock worth of initialized struct pages at many other place. We >> used to do that in the past because we have initialized the full >> section but this has been changed recently. Pavel, do you have any ideas >> how to deal with this partial mem sections now? > We have: > > remove_memory() > BUG_ON(check_hotplug_memory_range(start, size)) > > That supposed to safely check for this condition: if [start, start + > size) not block size aligned (and we know block size is section > aligned), hot remove is not allowed. The problem is this check is late, > and only happens when invalid range has already passed through previous > checks. > > We could add check_hotplug_memory_range() to is_mem_section_removable(): > > is_mem_section_removable(start_pfn, nr_pages) > if (check_hotplug_memory_range(PFN_PHYS(start_pfn), PFN_PHYS(nr_pages))) > return false; > > I think it should work. I don't think so since is_mem_section_removable() is called for for the entire section. Thus [start_pfn, start_pfn + nr_pages) is always memory block aligned. > > Pavel > >>> Signed-off-by: Mikhail Zaslonko >>> Reviewed-by: Gerald Schaefer >>> Cc: >>> --- >>> mm/memory_hotplug.c | 20 +++++++++++--------- >>> 1 file changed, 11 insertions(+), 9 deletions(-) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 9eea6e809a4e..8e20e8fcc3b0 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -1229,9 +1229,8 @@ static struct page *next_active_pageblock(struct page *page) >>> return page + pageblock_nr_pages; >>> } >>> >>> -static bool is_pageblock_removable_nolock(struct page *page) >>> +static bool is_pageblock_removable_nolock(struct page *page, struct zone **zone) >>> { >>> - struct zone *zone; >>> unsigned long pfn; >>> >>> /* >>> @@ -1241,15 +1240,14 @@ static bool is_pageblock_removable_nolock(struct page *page) >>> * We have to take care about the node as well. If the node is offline >>> * its NODE_DATA will be NULL - see page_zone. >>> */ >>> - if (!node_online(page_to_nid(page))) >>> - return false; >>> - >>> - zone = page_zone(page); >>> pfn = page_to_pfn(page); >>> - if (!zone_spans_pfn(zone, pfn)) >>> + if (*zone && !zone_spans_pfn(*zone, pfn)) >>> return false; >>> + if (!node_online(page_to_nid(page))) >>> + return false; >>> + *zone = page_zone(page); >>> >>> - return !has_unmovable_pages(zone, page, 0, MIGRATE_MOVABLE, true); >>> + return !has_unmovable_pages(*zone, page, 0, MIGRATE_MOVABLE, true); >>> } >>> >>> /* Checks if this range of memory is likely to be hot-removable. */ >>> @@ -1257,10 +1255,11 @@ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) >>> { >>> struct page *page = pfn_to_page(start_pfn); >>> struct page *end_page = page + nr_pages; >>> + struct zone *zone = NULL; >>> >>> /* Check the starting page of each pageblock within the range */ >>> for (; page < end_page; page = next_active_pageblock(page)) { >>> - if (!is_pageblock_removable_nolock(page)) >>> + if (!is_pageblock_removable_nolock(page, &zone)) >>> return false; >>> cond_resched(); >>> } >>> @@ -1296,6 +1295,9 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn, >>> i++; >>> if (i == MAX_ORDER_NR_PAGES || pfn + i >= end_pfn) >>> continue; >>> + /* Check if we got outside of the zone */ >>> + if (zone && !zone_spans_pfn(zone, pfn)) >>> + return 0; >>> page = pfn_to_page(pfn + i); >>> if (zone && page_zone(page) != zone) >>> return 0; >>> -- >>> 2.16.4