From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751512AbcEIKEV (ORCPT ); Mon, 9 May 2016 06:04:21 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:18885 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080AbcEIKEU (ORCPT ); Mon, 9 May 2016 06:04:20 -0400 Message-ID: <57306038.1070907@huawei.com> Date: Mon, 9 May 2016 18:02:32 +0800 From: Xishi Qiu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Vlastimil Babka CC: Andrew Morton , Mel Gorman , Michal Hocko , David Rientjes , "'Kirill A . Shutemov'" , Joonsoo Kim , "Taku Izumi" , Alexander Duyck , Johannes Weiner , "Linux MM" , LKML Subject: Re: [PATCH] mm: fix pfn spans two sections in has_unmovable_pages() References: <57304B9A.40504@huawei.com> <57305AD8.9090202@suse.cz> In-Reply-To: <57305AD8.9090202@suse.cz> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.25.179] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020206.5730606A.01ED,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: cc2c8b5a05976ecd4dd4625a4106161d Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/5/9 17:39, Vlastimil Babka wrote: > On 05/09/2016 10:34 AM, Xishi Qiu wrote: >> If the pfn is not aligned to pageblock, the check pfn may access a next >> pageblcok, and the next pageblock may belong to a next section. Because >> struct page has not been alloced in the next section, so kernel panic. >> >> I find the caller of has_unmovable_pages() has passed a aligned pfn, so it >> doesn't have this problem. But the earlier kernel version(e.g. v3.10) has. >> e.g. echo xxx > /sys/devices/system/memory/soft_offline_page could trigger >> it. The following log is from RHEL v7.1 > > I think has_unmovable_pages() is wrong layer where to fix such problem, as I'll explain below. > >> [14111.611492] Stack: >> [14111.611494] ffffffff8115d952 0000000000000000 01ff880c393ebe40 ffff880c7ffd9000 >> [14111.611500] ffffea0061ffffc0 ffff880c7ffd9068 0000000000000286 0000000000000001 >> [14111.611505] ffff880c393ebe10 ffffffff811c265a 000000000187ffff 0000000000000200 >> [14111.611511] Call Trace: >> [14111.611516] [] ? has_unmovable_pages+0xd2/0x130 >> [14111.611521] [] set_migratetype_isolate+0xda/0x170 >> [14111.611526] [] soft_offline_page+0x9a/0x590 >> [14111.611530] [] ? _kstrtoull+0x3b/0xa0 >> [14111.611535] [] store_soft_offline_page+0xaf/0xf0 >> [14111.611539] [] dev_attr_store+0x18/0x30 >> [14111.611544] [] sysfs_write_file+0xc6/0x140 >> [14111.611548] [] vfs_write+0xbd/0x1e0 >> [14111.611551] [] SyS_write+0x58/0xb0 >> [14111.611556] [] system_call_fastpath+0x16/0x1b >> [14111.611559] Code: 66 66 66 90 48 83 e0 fd 0c a0 5d c3 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 66 66 66 90 48 83 c8 42 0c a0 5d c3 90 66 66 66 66 90 <8b> 07 25 00 c0 00 00 75 02 f3 c3 48 8b 07 f6 c4 80 75 0f 48 81 >> [14111.611594] RIP [] PageHuge+0x5/0x40 >> [14111.611598] RSP >> [14111.611600] CR2: ffffea0062000000 >> [14111.611604] ---[ end trace 9f780ed1def334c6 ]--- >> [14111.678586] Kernel panic - not syncing: Fatal exception >> >> Signed-off-by: Xishi Qiu > > It's not CC'd stable, so how will this patch fix the older kernels? Also you should determine which upstream kernel versions are affected, not a RHEL derivative. > Also is the current upstream broken or not? > OK, I'll resend it later. The current upstream has not this problem. >> --- >> mm/page_alloc.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 59de90d..9afc1bc 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6842,6 +6842,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, >> return false; >> >> pfn = page_to_pfn(page); >> + pfn = pfn & ~(pageblock_nr_pages - 1); > > I think it's wrong that has_unmovable_pages() would silently correct wrong input. See e.g. the call path from start_isolate_page_range -> set_migratetype_isolate -> has_unmovable_pages. In start_isolate_page_range() there are BUG_ON's to check the alignment. That would be more appropriate here as well (but use VM_BUG_ON please). > Yes, this path is correct. But the older kernel like the following path has the problem. soft_offline_page get_any_page __get_any_page set_migratetype_isolate has_unmovable_pages > One danger of the self-correction is that the adjusted pfn might be of > a different zone, so let's not go there. If there's a call stack that passes unaligned page, it has to be fixed higher in the stack IMHO. > How about change the pfn when calling set_migratetype_isolate()? e.g. set_migratetype_isolate((p & ~(pageblock_nr_pages - 1)), true); Thanks, Xishi Qiu >> for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { >> unsigned long check = pfn + iter; >> >> > > > . >