Re: [PATCH] mm/hugetlb: create hugetlb cgroup file in hugetlb_init

[Xishi Qiu]

On 2012/12/12 18:19, Michal Hocko wrote:

> On Wed 12-12-12 16:25:59, Jianguo Wu wrote:
>> Build kernel with CONFIG_HUGETLBFS=y,CONFIG_HUGETLB_PAGE=y
>> and CONFIG_CGROUP_HUGETLB=y, then specify hugepagesz=xx boot option,
>> system will boot fail.
>>
>> This failure is caused by following code path:
>> setup_hugepagesz
>> 	hugetlb_add_hstate
>> 		hugetlb_cgroup_file_init
>> 			cgroup_add_cftypes
>> 				kzalloc <--slab is *not available* yet
>>
>> For this path, slab is not available yet, so memory allocated will be
>> failed, and cause WARN_ON() in hugetlb_cgroup_file_init().
>>
>> So I move hugetlb_cgroup_file_init() into hugetlb_init().
> 
> I do not think this is a good idea. hugetlb_init is in __init section as
> well so what guarantees that the slab is initialized by then? Isn't this
> just a good ordering that makes this working?

Hi Michal,

__initcall functions will be called in
start_kernel()
	rest_init()  // -> slab is already
		kernel_init()
			kernel_init_freeable()
				do_basic_setup()
					do_initcalls()

and setup_hugepagesz() will be called in
start_kernel()
	parse_early_param()  // -> before mm_init() -> kmem_cache_init()

Is this right?

Thanks
Xishi Qiu

> Shouldn't this be rather placed in hugetlb_cgroup_create?
> 
>> Signed-off-by: Jianguo Wu <wujianguo@xxxxxxxxxx>
>> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
>> ---
>>  include/linux/hugetlb_cgroup.h |    7 ++-----
>>  mm/hugetlb.c                   |   11 +----------
>>  mm/hugetlb_cgroup.c            |   23 +++++++++++++++++++++--
>>  3 files changed, 24 insertions(+), 17 deletions(-)
>>
>> diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
>> index d73878c..5bb9c28 100644
>> --- a/include/linux/hugetlb_cgroup.h
>> +++ b/include/linux/hugetlb_cgroup.h
>> @@ -62,7 +62,7 @@ extern void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
>>  					 struct page *page);
>>  extern void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
>>  					   struct hugetlb_cgroup *h_cg);
>> -extern int hugetlb_cgroup_file_init(int idx) __init;
>> +extern void hugetlb_cgroup_file_init(void) __init;
>>  extern void hugetlb_cgroup_migrate(struct page *oldhpage,
>>  				   struct page *newhpage);
>>  
>> @@ -111,10 +111,7 @@ hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
>>  	return;
>>  }
>>  
>> -static inline int __init hugetlb_cgroup_file_init(int idx)
>> -{
>> -	return 0;
>> -}
>> +static inline void __init hugetlb_cgroup_file_init() {}
>>  
>>  static inline void hugetlb_cgroup_migrate(struct page *oldhpage,
>>  					  struct page *newhpage)
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 1ef2cd4..a30da48 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -1906,14 +1906,12 @@ static int __init hugetlb_init(void)
>>  		default_hstate.max_huge_pages = default_hstate_max_huge_pages;
>>  
>>  	hugetlb_init_hstates();
>> -
>>  	gather_bootmem_prealloc();
>> -
>>  	report_hugepages();
>>  
>>  	hugetlb_sysfs_init();
>> -
>>  	hugetlb_register_all_nodes();
>> +	hugetlb_cgroup_file_init();
>>  
>>  	return 0;
>>  }
>> @@ -1943,13 +1941,6 @@ void __init hugetlb_add_hstate(unsigned order)
>>  	h->next_nid_to_free = first_node(node_states[N_HIGH_MEMORY]);
>>  	snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
>>  					huge_page_size(h)/1024);
>> -	/*
>> -	 * Add cgroup control files only if the huge page consists
>> -	 * of more than two normal pages. This is because we use
>> -	 * page[2].lru.next for storing cgoup details.
>> -	 */
>> -	if (order >= HUGETLB_CGROUP_MIN_ORDER)
>> -		hugetlb_cgroup_file_init(hugetlb_max_hstate - 1);
>>  
>>  	parsed_hstate = h;
>>  }
>> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
>> index a3f358f..284cb68 100644
>> --- a/mm/hugetlb_cgroup.c
>> +++ b/mm/hugetlb_cgroup.c
>> @@ -340,7 +340,7 @@ static char *mem_fmt(char *buf, int size, unsigned long hsize)
>>  	return buf;
>>  }
>>  
>> -int __init hugetlb_cgroup_file_init(int idx)
>> +static void __init __hugetlb_cgroup_file_init(int idx)
>>  {
>>  	char buf[32];
>>  	struct cftype *cft;
>> @@ -382,7 +382,26 @@ int __init hugetlb_cgroup_file_init(int idx)
>>  
>>  	WARN_ON(cgroup_add_cftypes(&hugetlb_subsys, h->cgroup_files));
>>  
>> -	return 0;
>> +	return;
>> +}
>> +
>> +void __init hugetlb_cgroup_file_init()
>> +{
>> +	struct hstate *h;
>> +	int idx;
>> +
>> +	idx = 0;
>> +	for_each_hstate(h) {
>> +		/*
>> +		 * Add cgroup control files only if the huge page consists
>> +		 * of more than two normal pages. This is because we use
>> +		 * page[2].lru.next for storing cgoup details.
>> +		 */
>> +		if (h->order >= HUGETLB_CGROUP_MIN_ORDER)
>> +			__hugetlb_cgroup_file_init(idx);
>> +
>> +		idx++;
>> +	}
>>  }
>>  
>>  /*
>> -- 1.7.1
>>
> 



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