Re: boot panic with memcg enabled (Was [PATCH 3/4] memcg: don't use bootmem allocator in setup code)

[Balbir Singh <balbir@linux.vnet.ibm.com>]

Li Zefan wrote:
> (This patch should have CCed memcg maitainers)
> 
> My box failed to boot due to initialization failure of page_cgroup, and
> it's caused by this patch:
> 
> +	page = alloc_pages_node(nid, GFP_NOWAIT | __GFP_ZERO, order);
> 
> I added a printk, and found that order == 11 == MAX_ORDER.
> 
> Pekka J Enberg wrote:
>> From: Yinghai Lu <yinghai@kernel.org>
>>
>> The bootmem allocator is no longer available for page_cgroup_init() because we
>> set up the kernel slab allocator much earlier now.
>>
>> Cc: Ingo Molnar <mingo@elte.hu>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
>> ---
>>  mm/page_cgroup.c |   12 ++++++++----
>>  1 files changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
>> index 791905c..3dd4a90 100644
>> --- a/mm/page_cgroup.c
>> +++ b/mm/page_cgroup.c
>> @@ -47,6 +47,8 @@ static int __init alloc_node_page_cgroup(int nid)
>>  	struct page_cgroup *base, *pc;
>>  	unsigned long table_size;
>>  	unsigned long start_pfn, nr_pages, index;
>> +	struct page *page;
>> +	unsigned int order;
>>  
>>  	start_pfn = NODE_DATA(nid)->node_start_pfn;
>>  	nr_pages = NODE_DATA(nid)->node_spanned_pages;
>> @@ -55,11 +57,13 @@ static int __init alloc_node_page_cgroup(int nid)
>>  		return 0;
>>  
>>  	table_size = sizeof(struct page_cgroup) * nr_pages;
>> -
>> -	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
>> -			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
>> -	if (!base)
>> +	order = get_order(table_size);
>> +	page = alloc_pages_node(nid, GFP_NOWAIT | __GFP_ZERO, order);
>> +	if (!page)
>> +		page = alloc_pages_node(-1, GFP_NOWAIT | __GFP_ZERO, order);

This should potentially come with a KERN_WARNING indicating the page_cgroup now
is allocated out of the current node rather than the desired node. It'll help
debug potential issues later.

>> +	if (!page)
>>  		return -ENOMEM;
>> +	base = page_address(page);
>>  	for (index = 0; index < nr_pages; index++) {
>>  		pc = base + index;
>>  		__init_page_cgroup(pc, start_pfn + index);

Looks good to me, does it work for you, Yinghai? Kamezawa-San  could you take a look


-- 
	Balbir

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