From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 3C80D6B6DD9 for ; Tue, 4 Dec 2018 03:56:43 -0500 (EST) Received: by mail-ed1-f69.google.com with SMTP id e12so7895416edd.16 for ; Tue, 04 Dec 2018 00:56:43 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id e19sor8504482edq.29.2018.12.04.00.56.41 for (Google Transport Security); Tue, 04 Dec 2018 00:56:41 -0800 (PST) MIME-Version: 1.0 References: <1543892757-4323-1-git-send-email-kernelfans@gmail.com> <20181204072251.GT31738@dhcp22.suse.cz> <20181204084052.gpwwlnp6n2zehjy5@master> In-Reply-To: <20181204084052.gpwwlnp6n2zehjy5@master> From: Pingfan Liu Date: Tue, 4 Dec 2018 16:56:29 +0800 Message-ID: Subject: Re: [PATCH] mm/alloc: fallback to first node if the wanted node offline Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: richard.weiyang@gmail.com Cc: mhocko@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Vlastimil Babka , Mike Rapoport , Bjorn Helgaas , Jonathan Cameron On Tue, Dec 4, 2018 at 4:40 PM Wei Yang wrote: > > On Tue, Dec 04, 2018 at 04:20:32PM +0800, Pingfan Liu wrote: > >On Tue, Dec 4, 2018 at 3:22 PM Michal Hocko wrote: > >> > >> On Tue 04-12-18 11:05:57, Pingfan Liu wrote: > >> > During my test on some AMD machine, with kexec -l nr_cpus=x option, the > >> > kernel failed to bootup, because some node's data struct can not be allocated, > >> > e.g, on x86, initialized by init_cpu_to_node()->init_memory_less_node(). But > >> > device->numa_node info is used as preferred_nid param for > >> > __alloc_pages_nodemask(), which causes NULL reference > >> > ac->zonelist = node_zonelist(preferred_nid, gfp_mask); > >> > This patch tries to fix the issue by falling back to the first online node, > >> > when encountering such corner case. > >> > >> We have seen similar issues already and the bug was usually that the > >> zonelists were not initialized yet or the node is completely bogus. > >> Zonelists should be initialized by build_all_zonelists quite early so I > >> am wondering whether the later is the case. What is the actual node > >> number the device is associated with? > >> > >The device's node num is 2. And in my case, I used nr_cpus param. Due > >to init_cpu_to_node() initialize all the possible node. It is hard > >for me to figure out without this param, how zonelists is accessed > >before page allocator works. > > If my understanding is correct, we can't do page alloc before zonelist > is initialized. > > I guess Michal's point is to figure out this reason. > Yeah, I know. I just want to emphasize that I hit this bug using nr_cpus, which may be rarely used by people. Hence it may be a different bug as Michal had seen. Sorry for bad English if it cause confusion. Thanks [...]