From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [202.81.18.234]) by e23smtp06.au.ibm.com (8.13.1/8.13.1) with ESMTP id m9LBSeBs009735 for ; Tue, 21 Oct 2008 22:28:40 +1100 Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id m9LBTY3n2142314 for ; Tue, 21 Oct 2008 22:29:36 +1100 Received: from d23av02.au.ibm.com (loopback [127.0.0.1]) by d23av02.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m9LBTXLw019970 for ; Tue, 21 Oct 2008 22:29:34 +1100 Message-ID: <48FDBD18.6090100@linux.vnet.ibm.com> Date: Tue, 21 Oct 2008 16:59:28 +0530 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com MIME-Version: 1.0 Subject: Re: [memcg BUG] unable to handle kernel NULL pointer derefence at 00000000 References: <20081021161621.bb51af90.kamezawa.hiroyu@jp.fujitsu.com> <48FD82E3.9050502@cn.fujitsu.com> <20081021171801.4c16c295.kamezawa.hiroyu@jp.fujitsu.com> <48FD943D.5090709@cn.fujitsu.com> <20081021175735.0c3d3534.kamezawa.hiroyu@jp.fujitsu.com> <48FD9D30.2030500@cn.fujitsu.com> <20081021182551.0158a47b.kamezawa.hiroyu@jp.fujitsu.com> <48FDA6D4.3090809@cn.fujitsu.com> <20081021191417.02ab97cc.kamezawa.hiroyu@jp.fujitsu.com> <48FDB584.7080608@cn.fujitsu.com> <20081021111951.GB4476@elte.hu> <20081021202325.938678c0.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20081021202325.938678c0.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki Cc: Ingo Molnar , Li Zefan , Paul Menage , Daisuke Nishimura , linux-mm@kvack.org, mel@csn.ul.ie List-ID: KAMEZAWA Hiroyuki wrote: > On Tue, 21 Oct 2008 13:19:51 +0200 > Ingo Molnar wrote: > >> * Li Zefan wrote: >> >>>> Oh! thanks...but it seems pc->page is NULL in the middle of ZONE_NORMAL.. >>>> == >>>> Normal 0x00001000 -> 0x000373fe >>>> == >>>> This is appearently in the range of page_cgroup initialization. >>>> (if pgdat->node_page_cgroup is initalized correctly...) >>>> >>>> I think write to page_cgroup->page happens only at initialization. >>>> Hmm ? not initilization failure but curruption ? >>>> >>> Yes, curruption. I didn't find informatation about initialization failure. >>> >>>> What happens if replacing __alloc_bootmem() with vmalloc() in page_cgroup.c init ? >>>> >>> So I did this change, and the box booted up without any problem. >>> >>> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c >>> index 5d86550..82a30b1 100644 >>> --- a/mm/page_cgroup.c >>> +++ b/mm/page_cgroup.c >>> @@ -48,8 +48,7 @@ static int __init alloc_node_page_cgroup(int nid) >>> >>> table_size = sizeof(struct page_cgroup) * nr_pages; >>> >>> - base = __alloc_bootmem_node_nopanic(NODE_DATA(nid), >>> - table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS)); >>> + base = vmalloc_node(table_size, nid); >>> if (!base) >>> return -ENOMEM; >> i have this: >> >> CONFIG_FAILSLAB=y >> CONFIG_FAIL_PAGE_ALLOC=y >> # CONFIG_FAIL_MAKE_REQUEST is not set >> CONFIG_FAIL_IO_TIMEOUT=y >> >> so the bug was perhaps that the __alloc_bootmem_node_nopanic() failed >> and this code continued silently? vmalloc_node() probably is more >> agressive about allocating memory. >> > Sorry. I think I cannot use alloc_bootmem() at this point because > it's too late in init-path. (we can use usual page allocator) > So, just replacing alloc_bootmem() with vmalloc_node() is a fix.... Kamezawa-San, I would prefer to use alloc_bootmem() instead of vmalloc_node(). May be we can shift cgroups, so that we use early_init for allocating page_cgroups. What do you think? -- Balbir -- 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