From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f199.google.com (mail-ot0-f199.google.com [74.125.82.199]) by kanga.kvack.org (Postfix) with ESMTP id 9EA246B0003 for ; Mon, 11 Jun 2018 08:33:25 -0400 (EDT) Received: by mail-ot0-f199.google.com with SMTP id p12-v6so14090952oti.6 for ; Mon, 11 Jun 2018 05:33:25 -0700 (PDT) Received: from huawei.com ([45.249.212.35]) by mx.google.com with ESMTPS id v127-v6si12326026oif.119.2018.06.11.05.33.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Jun 2018 05:33:24 -0700 (PDT) Subject: Re: [PATCH 1/2] arm64: avoid alloc memory on offline node References: <1527768879-88161-1-git-send-email-xiexiuqi@huawei.com> <1527768879-88161-2-git-send-email-xiexiuqi@huawei.com> <20180606154516.GL6631@arm.com> <20180607105514.GA13139@dhcp22.suse.cz> <5ed798a0-6c9c-086e-e5e8-906f593ca33e@huawei.com> <20180607122152.GP32433@dhcp22.suse.cz> <20180611085237.GI13364@dhcp22.suse.cz> From: Xie XiuQi Message-ID: <16c4db2f-bc70-d0f2-fb38-341d9117ff66@huawei.com> Date: Mon, 11 Jun 2018 20:32:10 +0800 MIME-Version: 1.0 In-Reply-To: <20180611085237.GI13364@dhcp22.suse.cz> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Hanjun Guo , Bjorn Helgaas , Will Deacon , Catalin Marinas , Greg Kroah-Hartman , "Rafael J. Wysocki" , Jarkko Sakkinen , linux-arm , Linux Kernel Mailing List , wanghuiqiang@huawei.com, tnowicki@caviumnetworks.com, linux-pci@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, zhongjiang Hi Michal, On 2018/6/11 16:52, Michal Hocko wrote: > On Mon 11-06-18 11:23:18, Xie XiuQi wrote: >> Hi Michal, >> >> On 2018/6/7 20:21, Michal Hocko wrote: >>> On Thu 07-06-18 19:55:53, Hanjun Guo wrote: >>>> On 2018/6/7 18:55, Michal Hocko wrote: >>> [...] >>>>> I am not sure I have the full context but pci_acpi_scan_root calls >>>>> kzalloc_node(sizeof(*info), GFP_KERNEL, node) >>>>> and that should fall back to whatever node that is online. Offline node >>>>> shouldn't keep any pages behind. So there must be something else going >>>>> on here and the patch is not the right way to handle it. What does >>>>> faddr2line __alloc_pages_nodemask+0xf0 tells on this kernel? >>>> >>>> The whole context is: >>>> >>>> The system is booted with a NUMA node has no memory attaching to it >>>> (memory-less NUMA node), also with NR_CPUS less than CPUs presented >>>> in MADT, so CPUs on this memory-less node are not brought up, and >>>> this NUMA node will not be online (but SRAT presents this NUMA node); >>>> >>>> Devices attaching to this NUMA node such as PCI host bridge still >>>> return the valid NUMA node via _PXM, but actually that valid NUMA node >>>> is not online which lead to this issue. >>> >>> But we should have other numa nodes on the zonelists so the allocator >>> should fall back to other node. If the zonelist is not intiailized >>> properly, though, then this can indeed show up as a problem. Knowing >>> which exact place has blown up would help get a better picture... >>> >> >> I specific a non-exist node to allocate memory using kzalloc_node, >> and got this following error message. >> >> And I found out there is just a VM_WARN, but it does not prevent the memory >> allocation continue. >> >> This nid would be use to access NODE_DADA(nid), so if nid is invalid, >> it would cause oops here. >> >> 459 /* >> 460 * Allocate pages, preferring the node given as nid. The node must be valid and >> 461 * online. For more general interface, see alloc_pages_node(). >> 462 */ >> 463 static inline struct page * >> 464 __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) >> 465 { >> 466 VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); >> 467 VM_WARN_ON(!node_online(nid)); >> 468 >> 469 return __alloc_pages(gfp_mask, order, nid); >> 470 } >> 471 >> >> (I wrote a ko, to allocate memory on a non-exist node using kzalloc_node().) > > OK, so this is an artificialy broken code, right. You shouldn't get a > non-existent node via standard APIs AFAICS. The original report was > about an existing node which is offline AFAIU. That would be a different > case. If I am missing something and there are legitimate users that try > to allocate from non-existing nodes then we should handle that in > node_zonelist. I think hanjun's comments may help to understood this question: - NUMA node will be built if CPUs and (or) memory are valid on this NUMA node; - But if we boot the system with memory-less node and also with CONFIG_NR_CPUS less than CPUs in SRAT, for example, 64 CPUs total with 4 NUMA nodes, 16 CPUs on each NUMA node, if we boot with CONFIG_NR_CPUS=48, then we will not built numa node for node 3, but with devices on that numa node, alloc memory will be panic because NUMA node 3 is not a valid node. I triggered this BUG on arm64 platform, and I found a similar bug has been fixed on x86 platform. So I sent a similar patch for this bug. Or, could we consider to fix it in the mm subsystem?