On 28/06/2023 03:20, Yin Fengwei wrote: > > > On 6/27/23 16:09, Ryan Roberts wrote: >> On 27/06/2023 08:08, Yu Zhao wrote: >>> On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts <ryan.roberts@xxxxxxx> wrote: >>>> >>>> Like folio_add_new_anon_rmap() but batch-rmaps a range of pages >>>> belonging to a folio, for effciency savings. All pages are accounted as >>>> small pages. >>>> >>>> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> >>>> --- >>>> include/linux/rmap.h | 2 ++ >>>> mm/rmap.c | 43 +++++++++++++++++++++++++++++++++++++++++++ >>>> 2 files changed, 45 insertions(+) >>>> >>>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >>>> index a3825ce81102..15433a3d0cbf 100644 >>>> --- a/include/linux/rmap.h >>>> +++ b/include/linux/rmap.h >>>> @@ -196,6 +196,8 @@ void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, >>>> unsigned long address); >>>> void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *, >>>> unsigned long address); >>>> +void folio_add_new_anon_rmap_range(struct folio *folio, struct page *page, >>>> + int nr, struct vm_area_struct *vma, unsigned long address); >>> >>> We should update folio_add_new_anon_rmap() to support large() && >>> !folio_test_pmd_mappable() folios instead. >>> >>> I double checked all places currently using folio_add_new_anon_rmap(), >>> and as expected, none actually allocates large() && >>> !folio_test_pmd_mappable() and maps it one by one, which makes the >>> cases simpler, i.e., >>> if (!large()) >>> // the existing basepage case >>> else if (!folio_test_pmd_mappable()) >>> // our new case >>> else >>> // the existing THP case >> >> I don't have a strong opinion either way. Happy to go with this suggestion. But >> the reason I did it as a new function was because I was following the pattern in >> [1] which adds a new folio_add_file_rmap_range() function. >> >> [1] https://lore.kernel.org/linux-mm/20230315051444.3229621-35-willy@xxxxxxxxxxxxx/ > Oh. There is different here: > For page cache, large folio could be created by previous file access. But later > file access by other process just need map partial large folio. In this case, we need > _range for filemap. > > But for anonymous, I suppose we always map whole folio in. So I agree with Yu. We > don't need _range for folio_add_new_anon_rmap(). Thanks. Yes that makes sense - thanks. I'll merge the new case into folio_add_new_anon_rmap() for v2. > > > Regards > Yin, Fengwei > >> >> >>> >>>> void page_add_file_rmap(struct page *, struct vm_area_struct *, >>>> bool compound); >>>> void folio_add_file_rmap_range(struct folio *, struct page *, unsigned int nr, >>>> diff --git a/mm/rmap.c b/mm/rmap.c >>>> index 1d8369549424..4050bcea7ae7 100644 >>>> --- a/mm/rmap.c >>>> +++ b/mm/rmap.c >>>> @@ -1305,6 +1305,49 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, >>>> __page_set_anon_rmap(folio, &folio->page, vma, address, 1); >>>> } >>>> >>>> +/** >>>> + * folio_add_new_anon_rmap_range - Add mapping to a set of pages within a new >>>> + * anonymous potentially large folio. >>>> + * @folio: The folio containing the pages to be mapped >>>> + * @page: First page in the folio to be mapped >>>> + * @nr: Number of pages to be mapped >>>> + * @vma: the vm area in which the mapping is added >>>> + * @address: the user virtual address of the first page to be mapped >>>> + * >>>> + * Like folio_add_new_anon_rmap() but batch-maps a range of pages within a folio >>>> + * using non-THP accounting. Like folio_add_new_anon_rmap(), the inc-and-test is >>>> + * bypassed and the folio does not have to be locked. All pages in the folio are >>>> + * individually accounted. >>>> + * >>>> + * As the folio is new, it's assumed to be mapped exclusively by a single >>>> + * process. >>>> + */ >>>> +void folio_add_new_anon_rmap_range(struct folio *folio, struct page *page, >>>> + int nr, struct vm_area_struct *vma, unsigned long address) >>>> +{ >>>> + int i; >>>> + >>>> + VM_BUG_ON_VMA(address < vma->vm_start || >>>> + address + (nr << PAGE_SHIFT) > vma->vm_end, vma); >>> >>> BTW, VM_BUG_ON* shouldn't be used in new code: >>> Documentation/process/coding-style.rst >> >> Thanks, sorry about that. Was copy-pasting from folio_add_new_anon_rmap(). >>
