Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751839AbcCZFcz (ORCPT ); Sat, 26 Mar 2016 01:32:55 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:58059 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750903AbcCZFcy (ORCPT ); Sat, 26 Mar 2016 01:32:54 -0400 Message-ID: <56F61EC8.7080508@huawei.com> Date: Sat, 26 Mar 2016 13:31:52 +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: Andrew Morton CC: Vlastimil Babka , Joonsoo Kim , "David Rientjes" , Naoya Horiguchi , Laura Abbott , , , Linux MM , LKML Subject: Re: [PATCH] mm: fix invalid node in alloc_migrate_target() References: <56F4E104.9090505@huawei.com> <20160325122237.4ca4e0dbca215ccbf4f49922@linux-foundation.org> In-Reply-To: <20160325122237.4ca4e0dbca215ccbf4f49922@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1" 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=0001.0A020205.56F61EE8.013C,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 735f221714f9b7d6687f203572d3a306 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1663 Lines: 51 On 2016/3/26 3:22, Andrew Morton wrote: > On Fri, 25 Mar 2016 14:56:04 +0800 Xishi Qiu wrote: > >> It is incorrect to use next_node to find a target node, it will >> return MAX_NUMNODES or invalid node. This will lead to crash in >> buddy system allocation. >> >> ... >> >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -289,11 +289,11 @@ struct page *alloc_migrate_target(struct page *page, unsigned long private, >> * now as a simple work-around, we use the next node for destination. >> */ >> if (PageHuge(page)) { >> - nodemask_t src = nodemask_of_node(page_to_nid(page)); >> - nodemask_t dst; >> - nodes_complement(dst, src); >> + int node = next_online_node(page_to_nid(page)); >> + if (node == MAX_NUMNODES) >> + node = first_online_node; >> return alloc_huge_page_node(page_hstate(compound_head(page)), >> - next_node(page_to_nid(page), dst)); >> + node); >> } >> >> if (PageHighMem(page)) > > Indeed. Can you tell us more about this circumstances under which the > kernel will crash? I need to decide which kernel version(s) need the > patch, but the changelog doesn't contain the info needed to make this > decision (it should). > Hi Andrew, I read the code v4.4, and find the following path maybe trigger the bug. alloc_migrate_target() alloc_huge_page_node() // the node may be offline or MAX_NUMNODES __alloc_buddy_huge_page_no_mpol() __alloc_buddy_huge_page() __hugetlb_alloc_buddy_huge_page() alloc_pages_node() __alloc_pages_node() VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); VM_WARN_ON(!node_online(nid)); Thanks, Xishi Qiu