linux-kernel - Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in populate_section

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Date:   Tue, 10 Mar 2020 15:59:08 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>, Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, richardw.yang@...ux.intel.com,
        dan.j.williams@...el.com, osalvador@...e.de, rppt@...ux.ibm.com
Subject: Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in
 populate_section_memmap()

On 10.03.20 15:56, Michal Hocko wrote:
> On Sat 07-03-20 16:42:29, Baoquan He wrote:
>> This removes the unnecessary goto, and simplify codes.
>>
>> Signed-off-by: Baoquan He <bhe@...hat.com>
>> Reviewed-by: Wei Yang <richardw.yang@...ux.intel.com>
>> ---
>>  mm/sparse.c | 16 ++++++----------
>>  1 file changed, 6 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index fde651ab8741..266f7f5040fb 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -735,23 +735,19 @@ static void free_map_bootmem(struct page *memmap)
>>  struct page * __meminit populate_section_memmap(unsigned long pfn,
>>  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>>  {
>> -	struct page *page, *ret;
>> +	struct page *ret;
>>  	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
>>  
>> -	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
>> -	if (page)
>> -		goto got_map_page;
>> +	ret = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
>> +				get_order(memmap_size));
>> +	if (ret)
>> +		return ret;
>>  
>>  	ret = vmalloc(memmap_size);
>>  	if (ret)
>> -		goto got_map_ptr;
>> +		return ret;
>>  
>>  	return NULL;
>> -got_map_page:
>> -	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
>> -got_map_ptr:
>> -
>> -	return ret;
>>  }
> 
> Boy this code is ugly. Is there any reason we cannot simply use
> kvmalloc_array(PAGES_PER_SECTION, sizeof(struct page), GFP_KERNEL | __GFP_NOWARN)
> 
> And if we care about locality then go even one step further
> kvmalloc_node(PAGES_PER_SECTION * sizeof(struct page), GFP_KERNEL | __GFP_NOWARN, nid)
> 

Makes perfect sense to me.

-- 
Thanks,

David / dhildenb