On 1/31/2023 3:24 PM, Huang, Ying wrote:
> Yin Fengwei <fengwei.yin@xxxxxxxxx> writes:
>
>> page_add_file_rmap_range() allows to add specific range of
>> large folio rmap.
>>
>> Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
>> ---
>> include/linux/rmap.h | 2 ++
>> mm/rmap.c | 70 ++++++++++++++++++++++++++++----------------
>> 2 files changed, 46 insertions(+), 26 deletions(-)
>>
>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
>> index a6bd1f0a183d..063e0addcbf8 100644
>> --- a/include/linux/rmap.h
>> +++ b/include/linux/rmap.h
>> @@ -198,6 +198,8 @@ void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
>> unsigned long address);
>> void page_add_file_rmap(struct page *, struct vm_area_struct *,
>> bool compound);
>> +void page_add_file_rmap_range(struct folio *, struct page *, int len,
>> + struct vm_area_struct *, bool compound);
>> void page_remove_rmap(struct page *, struct vm_area_struct *,
>> bool compound);
>>
>> diff --git a/mm/rmap.c b/mm/rmap.c
>> index 948ca17a96ad..cc7fe3010330 100644
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -1301,40 +1301,19 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
>> __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
>> }
>>
>> -/**
>> - * page_add_file_rmap - add pte mapping to a file page
>> - * @page: the page to add the mapping to
>> - * @vma: the vm area in which the mapping is added
>> - * @compound: charge the page as compound or small page
>> - *
>> - * The caller needs to hold the pte lock.
>> - */
>> -void page_add_file_rmap(struct page *page, struct vm_area_struct *vma,
>> - bool compound)
>> +void page_add_file_rmap_range(struct folio *folio, struct page *page, int len,
>> + struct vm_area_struct *vma, bool compound)
>> {
>> - struct folio *folio = page_folio(page);
>> atomic_t *mapped = &folio->_nr_pages_mapped;
>> - int nr = 0, nr_pmdmapped = 0;
>> + int nr = 0, nr_pmdmapped = 0, nr_pages = folio_nr_pages(folio);
>> bool first;
>>
>> - VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
>> -
>> - /* Is page being mapped by PTE? Is this its first map to be added? */
>> - if (likely(!compound)) {
>> - first = atomic_inc_and_test(&page->_mapcount);
>> - nr = first;
>> - if (first && folio_test_large(folio)) {
>> - nr = atomic_inc_return_relaxed(mapped);
>> - nr = (nr < COMPOUND_MAPPED);
>> - }
>> - } else if (folio_test_pmd_mappable(folio)) {
>> - /* That test is redundant: it's for safety or to optimize out */
>> -
>> + if (compound) {
>> first = atomic_inc_and_test(&folio->_entire_mapcount);
>> if (first) {
>> nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped);
>> if (likely(nr < COMPOUND_MAPPED + COMPOUND_MAPPED)) {
>> - nr_pmdmapped = folio_nr_pages(folio);
>> + nr_pmdmapped = nr_pages;
>> nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
>> /* Raced ahead of a remove and another add? */
>> if (unlikely(nr < 0))
>> @@ -1344,6 +1323,20 @@ void page_add_file_rmap(struct page *page, struct vm_area_struct *vma,
>> nr = 0;
>> }
>> }
>> + } else {
>> + int i = 0, new_mapped = 0, count;
>> +
>> + count = min_t(int, len, nr_pages - folio_page_idx(folio, page));
>
> It appears that count isn't used after assignment.
Oops. This should be used in while (page++, ++i < count);
Maybe this line can be removed if we are sure the range is not out of
folio size? Thanks.
Regards
Yin, Fengwei
>
> Best Regards,
> Huang, Ying
>
>> + do {
>> + first = atomic_inc_and_test(&page->_mapcount);
>> + new_mapped = first;
>> + if (first && folio_test_large(folio)) {
>> + new_mapped = atomic_inc_return_relaxed(mapped);
>> + new_mapped = (new_mapped < COMPOUND_MAPPED);
>> + }
>> + if (new_mapped)
>> + nr++;
>> + } while (page++, ++i < len);
>> }
>>
>> if (nr_pmdmapped)
>> @@ -1355,6 +1348,31 @@ void page_add_file_rmap(struct page *page, struct vm_area_struct *vma,
>> mlock_vma_folio(folio, vma, compound);
>> }
>>
>> +/**
>> + * page_add_file_rmap - add pte mapping to a file page
>> + * @page: the page to add the mapping to
>> + * @vma: the vm area in which the mapping is added
>> + * @compound: charge the page as compound or small page
>> + *
>> + * The caller needs to hold the pte lock.
>> + */
>> +void page_add_file_rmap(struct page *page, struct vm_area_struct *vma,
>> + bool compound)
>> +{
>> + struct folio *folio = page_folio(page);
>> + int nr_pages;
>> +
>> + VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
>> +
>> + if (likely(!compound))
>> + nr_pages = 1;
>> + else
>> + nr_pages = folio_nr_pages(folio);
>> +
>> + page_add_file_rmap_range(folio, page, nr_pages, vma, compound);
>> +}
>> +
>> /**
>> * page_remove_rmap - take down pte mapping from a page
>> * @page: page to remove mapping from
