On 05/12/2023 13:32, David Hildenbrand wrote:
> On 05.12.23 14:17, David Hildenbrand wrote:
>> On 05.12.23 14:12, Ryan Roberts wrote:
>>> On 04/12/2023 14:21, David Hildenbrand wrote:
>>>> The last user of page_needs_cow_for_dma() and __page_dup_rmap() are gone,
>>>> remove them.
>>>>
>>>> Add folio_try_dup_anon_rmap_ptes() right away, we want to perform rmap
>>>> baching during fork() soon.
>>>>
>>>> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>>>> ---
>>>> include/linux/mm.h | 6 --
>>>> include/linux/rmap.h | 145 +++++++++++++++++++++++++++++--------------
>>>> 2 files changed, 100 insertions(+), 51 deletions(-)
>>>>
>>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>>> index 24c1c7c5a99c0..f7565b35ae931 100644
>>>> --- a/include/linux/mm.h
>>>> +++ b/include/linux/mm.h
>>>> @@ -1964,12 +1964,6 @@ static inline bool folio_needs_cow_for_dma(struct
>>>> vm_area_struct *vma,
>>>> return folio_maybe_dma_pinned(folio);
>>>> }
>>>> -static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
>>>> - struct page *page)
>>>> -{
>>>> - return folio_needs_cow_for_dma(vma, page_folio(page));
>>>> -}
>>>> -
>>>> /**
>>>> * is_zero_page - Query if a page is a zero page
>>>> * @page: The page to query
>>>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
>>>> index 21d72cc602adc..84439f7720c62 100644
>>>> --- a/include/linux/rmap.h
>>>> +++ b/include/linux/rmap.h
>>>> @@ -354,68 +354,123 @@ static inline void folio_dup_file_rmap_pmd(struct
>>>> folio *folio,
>>>> #endif
>>>> }
>>>> -static inline void __page_dup_rmap(struct page *page, bool compound)
>>>> +static inline int __folio_try_dup_anon_rmap(struct folio *folio,
>>>
>>> __always_inline?
>>
>> Yes.
>>
>>>
>>>> + struct page *page, unsigned int nr_pages,
>>>> + struct vm_area_struct *src_vma, enum rmap_mode mode)
>>>> {
>>>> - VM_WARN_ON(folio_test_hugetlb(page_folio(page)));
>>>> + int i;
>>>> - if (compound) {
>>>> - struct folio *folio = (struct folio *)page;
>>>> + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
>>>> - VM_BUG_ON_PAGE(compound && !PageHead(page), page);
>>>> - atomic_inc(&folio->_entire_mapcount);
>>>> - } else {
>>>> - atomic_inc(&page->_mapcount);
>>>> + /*
>>>> + * No need to check+clear for already shared PTEs/PMDs of the folio.
>>>> + * This includes PTE mappings of (order-0) KSM folios.
>>>> + */
>>>> + if (likely(mode == RMAP_MODE_PTE)) {
>>>
>>> Presumbly if __always_inline then the compiler will remove this if/else and just
>>> keep the part indicated by mode? In which case "likely" is pretty useless? Same
>>> for all similar sites in the other patches.
>>
>> Yes, also had this in mind. As long as we use __always_inline it
>> shouldn't ever matter.
>
> It seems to be cleanest to just do:
>
> switch (mode) {
> case RMAP_MODE_PTE:
> ...
> break;
> case RMAP_MODE_PMD:
> ...
> break;
> }
>
Agreed.
