From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id A05B36B007E for ; Thu, 12 May 2016 08:01:01 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id d139so82676445oig.1 for ; Thu, 12 May 2016 05:01:01 -0700 (PDT) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com. [119.145.14.65]) by mx.google.com with ESMTPS id v18si5179619otv.39.2016.05.12.05.00.58 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 12 May 2016 05:01:00 -0700 (PDT) Message-ID: <57346FD6.6000306@huawei.com> Date: Thu, 12 May 2016 19:58:14 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [PATCH] mm: fix pfn spans two sections in has_unmovable_pages() References: <57304B9A.40504@huawei.com> <57305AD8.9090202@suse.cz> <57306038.1070907@huawei.com> <57346ADA.6050102@suse.cz> In-Reply-To: <57346ADA.6050102@suse.cz> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , Naoya Horiguchi Cc: Andrew Morton , Mel Gorman , Michal Hocko , David Rientjes , "'Kirill A . Shutemov'" , Joonsoo Kim , Taku Izumi , Alexander Duyck , Johannes Weiner , Linux MM , LKML On 2016/5/12 19:36, Vlastimil Babka wrote: > On 05/09/2016 12:02 PM, Xishi Qiu wrote: >> 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); > > Sounds ok, please try. > Hi Vlastimil and Naoya, The mainline doesn't have this problem, because commit add05cecef80 ("mm: soft-offline: don't free target page in successful page migration") fixed it in v4.2. I guess the above patch can't be applied to older kernel directly. So shall we rewrite a new one or backport the whole patches which it depend? Thanks, Xishi Qiu >> >> Thanks, >> Xishi Qiu >> >>>> for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { >>>> unsigned long check = pfn + iter; > > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org