On 27/11/2023 04:36, Barry Song wrote:
>> void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
>> unsigned long address)
>> {
>> - int nr;
>> + int nr = folio_nr_pages(folio);
>>
>> - VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
>> + VM_BUG_ON_VMA(address < vma->vm_start ||
>> + address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
>> __folio_set_swapbacked(folio);
>> + __folio_set_anon(folio, vma, address, true);
>>
>> - if (likely(!folio_test_pmd_mappable(folio))) {
>> + if (likely(!folio_test_large(folio))) {
>> /* increment count (starts at -1) */
>> atomic_set(&folio->_mapcount, 0);
>> - nr = 1;
>> + SetPageAnonExclusive(&folio->page);
>> + } else if (!folio_test_pmd_mappable(folio)) {
>> + int i;
>> +
>> + for (i = 0; i < nr; i++) {
>> + struct page *page = folio_page(folio, i);
>> +
>> + /* increment count (starts at -1) */
>> + atomic_set(&page->_mapcount, 0);
>> + SetPageAnonExclusive(page);
>
> Hi Ryan,
>
> we are doing an entire mapping, right? what is the reason to
> increase mapcount for each subpage? shouldn't we only increase
> mapcount of subpage in either split or doublemap case?
>
> in page_add_anon_rmap(), are we also increasing mapcount of
> each subpage for fork() case where the entire large folio
> is inheritted by child processes?
I think this is all answered by the conversation we just had in the context of
the contpte series? Let me know if you still have concerns.
>
>> + }
>> +
>> + atomic_set(&folio->_nr_pages_mapped, nr);
>> } else {
>> /* increment count (starts at -1) */
>> atomic_set(&folio->_entire_mapcount, 0);
>> atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED);
>> - nr = folio_nr_pages(folio);
>> + SetPageAnonExclusive(&folio->page);
>> __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
>> }
>>
>> __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
>> - __folio_set_anon(folio, vma, address, true);
>> - SetPageAnonExclusive(&folio->page);
>> }
>
> Thanks
> Barry
>
