Re: [PATCH 1/9] mm: Convert ksm_might_need_to_copy() to work on folios

[David Hildenbrand <david@redhat.com>]

On 12.12.23 13:43, Matthew Wilcox wrote:
> On Tue, Dec 12, 2023 at 01:32:50PM +0100, David Hildenbrand wrote:
>>> +++ b/mm/swapfile.c
>>> @@ -1749,11 +1749,13 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>>>    	int ret = 1;
>>>    	swapcache = page;
>>> -	page = ksm_might_need_to_copy(page, vma, addr);
>>> -	if (unlikely(!page))
>>> +	folio = ksm_might_need_to_copy(folio, vma, addr);
>>> +	if (unlikely(!folio))
>>>    		return -ENOMEM;
>>> -	else if (unlikely(PTR_ERR(page) == -EHWPOISON))
>>> +	else if (unlikely(folio == ERR_PTR(-EHWPOISON)))
>>>    		hwpoisoned = true;
>>> +	else
>>> +		page = folio_file_page(folio, swp_offset(entry));
>>
>> Just to double-check:
>>
>> assuming ksm_might_need_to_copy() in fact allocated a fresh (order-0) folio,
>> folio_file_page() will simply translate to "folio_page(folio, 0)" and should
>> be fine.
> 
> That's right:
> 
> static inline struct page *folio_file_page(struct folio *folio, pgoff_t index)
> {
>          return folio_page(folio, index & (folio_nr_pages(folio) - 1));
> }
> 
> so an order-0 folio will return the only page in the folio.
> 

LGTM then

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb