Re: [memcg BUG ?] failed to boot on IA64 with CONFIG_DISCONTIGMEM=y

["KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>]

Andrew Morton said:
> On Fri, 5 Dec 2008 12:24:58 +0900 KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
>> On Fri, 5 Dec 2008 12:20:24 +0900
>> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>>
>> > On Fri, 05 Dec 2008 11:09:29 +0800
>> > Li Zefan <lizf@cn.fujitsu.com> wrote:
>> >
>> > > Kernel version: 2.6.28-rc7
>> > > Arch: IA64
>> > > Memory model: DISCONTIGMEM
>> > >
>> > > ELILO boot: Uncompressing Linux... done
>> > > Loading file initrd-2.6.28-rc7-lizf.img...done
>> > > (frozen)
>> > >
>> > >
>> > > Booted successfully with cgroup_disable=memory, here is the dmesg:
>> > >
>> >
>> > thx, will dig into...Maybe you're the first person using DISCONTIGMEM
>> with
>> > empty_node after page_cgroup-alloc-at-boot.
>> >
>> > How about this ?
>>
>> Ahhh..sorry.
>>
>> this one please.
>> ==
>>
>> From: kamezawa.hiroyu@jp.fujitsu.com
>>
>> page_cgroup should ignore empty-nodes.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>>
>> ---
>>  mm/page_cgroup.c |    3 +++
>>  1 file changed, 3 insertions(+)
>>
>> Index: mmotm-2.6.28-Dec03/mm/page_cgroup.c
>> ===================================================================
>> --- mmotm-2.6.28-Dec03.orig/mm/page_cgroup.c
>> +++ mmotm-2.6.28-Dec03/mm/page_cgroup.c
>> @@ -51,6 +51,9 @@ static int __init alloc_node_page_cgroup
>>  	start_pfn = NODE_DATA(nid)->node_start_pfn;
>>  	nr_pages = NODE_DATA(nid)->node_spanned_pages;
>>
>> +	if (!nr_pages)
>> +		return 0;
>> +
>>  	table_size = sizeof(struct page_cgroup) * nr_pages;
>>
>>  	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
>
> Why did the kernel fail?
>
> Either __alloc_bootmem_node_nopanic() succeeds, in which case the code
> looks like it handles that OK.
>
> Or __alloc_bootmem_node_nopanic() fails this zero-sized allocation, and
> the code attempts to handle that, but fails to do so, which might be a
> bug, and the above patch just papers over it.
>
After this, print a message like "memcg cannot allocate memory, please try
cgroup_disable=memory as boot option", and panic.
This is a boot time failure which can be avoided by boot option.

> Of course, a full description of the problem will clear all this up.
> Better changelogs, please.
>

will do.

-Kame


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