From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f169.google.com (mail-pf0-f169.google.com [209.85.192.169]) by kanga.kvack.org (Postfix) with ESMTP id 6DC6D6B007E for ; Sat, 26 Mar 2016 01:34:10 -0400 (EDT) Received: by mail-pf0-f169.google.com with SMTP id 4so96375153pfd.0 for ; Fri, 25 Mar 2016 22:34:10 -0700 (PDT) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com. [119.145.14.65]) by mx.google.com with ESMTPS id l90si11593669pfb.194.2016.03.25.22.34.08 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 25 Mar 2016 22:34:09 -0700 (PDT) Message-ID: <56F61EC8.7080508@huawei.com> Date: Sat, 26 Mar 2016 13:31:52 +0800 From: Xishi Qiu MIME-Version: 1.0 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 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Vlastimil Babka , Joonsoo Kim , David Rientjes , Naoya Horiguchi , Laura Abbott , zhuhui@xiaomi.com, wangxq10@lzu.edu.cn, Linux MM , LKML 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 -- 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