Re: [PATCH v1 02/11] mm/page_alloc: split prep_compound_page into head and tail subparts

Joao Martins
2021-04-24T19:05:51Z

On 4/24/21 1:16 AM, Dan Williams wrote:
> On Thu, Mar 25, 2021 at 4:10 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>>
>> Split the utility function prep_compound_page() into head and tail
>> counterparts, and use them accordingly.
>
> To make this patch stand alone better lets add another sentence:
>
> "This is in preparation for sharing the storage for / deduplicating
> compound page metadata."
>
Yeap, I've fixed it up.

> Other than that, looks good to me.
>
/me nods

>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>> mm/page_alloc.c | 32 +++++++++++++++++++++-----------
>> 1 file changed, 21 insertions(+), 11 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index c53fe4fa10bf..43dd98446b0b 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -692,24 +692,34 @@ void free_compound_page(struct page *page)
>> __free_pages_ok(page, compound_order(page), FPI_NONE);
>> }
>>
>> +static void prep_compound_head(struct page *page, unsigned int order)
>> +{
>> + set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
>> + set_compound_order(page, order);
>> + atomic_set(compound_mapcount_ptr(page), -1);
>> + if (hpage_pincount_available(page))
>> + atomic_set(compound_pincount_ptr(page), 0);
>> +}
>> +
>> +static void prep_compound_tail(struct page *head, int tail_idx)
>> +{
>> + struct page *p = head + tail_idx;
>> +
>> + set_page_count(p, 0);
>> + p->mapping = TAIL_MAPPING;
>> + set_compound_head(p, head);
>> +}
>> +
>> void prep_compound_page(struct page *page, unsigned int order)
>> {
>> int i;
>> int nr_pages = 1 << order;
>>
>> __SetPageHead(page);
>> - for (i = 1; i < nr_pages; i++) {
>> - struct page *p = page + i;
>> - set_page_count(p, 0);
>> - p->mapping = TAIL_MAPPING;
>> - set_compound_head(p, page);
>> - }
>> + for (i = 1; i < nr_pages; i++)
>> + prep_compound_tail(page, i);
>>
>> - set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
>> - set_compound_order(page, order);
>> - atomic_set(compound_mapcount_ptr(page), -1);
>> - if (hpage_pincount_available(page))
>> - atomic_set(compound_pincount_ptr(page), 0);
>> + prep_compound_head(page, order);
>> }
>>
>> #ifdef CONFIG_DEBUG_PAGEALLOC
>> --
>> 2.17.1
>>