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. 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(). >
