On 02/08/2023 12:14, Ryan Roberts wrote: > On 28/07/2023 08:09, Yin Fengwei wrote: >> It will be used to check whether the folio is mapped to specific >> VMA and whether the mapping address of folio is in the range. >> >> Also a helper function folio_within_vma() to check whether folio >> is in the range of vma based on folio_in_range(). >> >> Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx> >> --- >> mm/internal.h | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 69 insertions(+) >> >> diff --git a/mm/internal.h b/mm/internal.h >> index 5a03bc4782a2..63de32154a48 100644 >> --- a/mm/internal.h >> +++ b/mm/internal.h >> @@ -585,6 +585,75 @@ extern long faultin_vma_page_range(struct vm_area_struct *vma, >> bool write, int *locked); >> extern bool mlock_future_ok(struct mm_struct *mm, unsigned long flags, >> unsigned long bytes); >> + >> +/* >> + * Check whether the folio is in specific range >> + * >> + * First, check whether the folio is in the range of vma. >> + * Then, check whether the folio is mapped to the range of [start, end]. >> + * In the end, check whether the folio is fully mapped to the range. >> + * >> + * @pte page table pointer will be checked whether the large folio >> + * is fully mapped to. Currently, if mremap in the middle of >> + * large folio, the large folio could be mapped to to different >> + * VMA and address check can't identify this situation. >> + */ >> +static inline bool >> +folio_in_range(struct folio *folio, struct vm_area_struct *vma, >> + unsigned long start, unsigned long end, pte_t *pte) > > This api seems a bit redundant to me. Wouldn't it be better to remove the vma > parameter and instead fix up the start/end addresses in folio_within_vma()? I have created a function as part of my "pte batch-zap" patch set [1], which counts the number of contiguously mapped pages of a folio (folio_nr_pages_cont_mapped()). I wonder if actually this should be the primitive, which can be shared for more cases. Then your folio_within_vma() function could just compare the nr_pages to folio_nr_pages() to decide if the folio is fully and contiguously mapped in the VMA. I also wonder if you should change the name of folio_within_vma() to something like folio_test_cont_in_vma() to disambiguate from the case where the folio may be fully mapped with a discontiguity (although perhaps that's not possible because a mremap would result in distinct vmas... would a new mmap in the hole cause a merge of all 3?). [1] https://lore.kernel.org/linux-mm/20230727141837.3386072-4-ryan.roberts@xxxxxxx/ > >> +{ >> + pte_t ptent; >> + unsigned long i, nr = folio_nr_pages(folio); >> + pgoff_t pgoff, addr; >> + unsigned long vma_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; >> + >> + VM_WARN_ON_FOLIO(folio_test_ksm(folio), folio); >> + >> + if (start < vma->vm_start) >> + start = vma->vm_start; >> + if (end > vma->vm_end) >> + end = vma->vm_end; >> + >> + pgoff = folio_pgoff(folio); >> + /* if folio start address is not in vma range */ >> + if (pgoff < vma->vm_pgoff || pgoff > vma->vm_pgoff + vma_pglen) >> + return false; >> + >> + addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); >> + if (addr < start || end - addr < folio_size(folio)) >> + return false; >> + >> + /* not necessary to check pte for none large folio */ >> + if (!folio_test_large(folio)) >> + return true; >> + >> + if (!pte) >> + return false; >> + >> + /* check whether parameter pte is associated with folio */ >> + ptent = ptep_get(pte); >> + if (pte_none(ptent) || !pte_present(ptent) || >> + pte_pfn(ptent) - folio_pfn(folio) >= nr) >> + return false; >> + >> + pte -= pte_pfn(ptent) - folio_pfn(folio); >> + for (i = 0; i < nr; i++, pte++) { >> + ptent = ptep_get(pte); >> + >> + if (pte_none(ptent) || !pte_present(ptent) || >> + pte_pfn(ptent) - folio_pfn(folio) >= nr) >> + return false; >> + } > > I don't think I see anything to ensure you don't wander off the end (or start) > of the pgtable? If the folio is mremapped so that it straddles multiple tables > (or is bigger than a single table?) then I think pte can become invalid? Perhaps > you intended start/end to always be within the same pgtable, but that is not > guarranteed in the case that folio_within_vma() is making the call. > > Also I want to check that this function is definitely always called under the > PTL for the table that pte belongs to? > >> + >> + return true; >> +} >> + >> +static inline bool >> +folio_within_vma(struct folio *folio, struct vm_area_struct *vma, pte_t *pte) >> +{ >> + return folio_in_range(folio, vma, vma->vm_start, vma->vm_end, pte); >> +} >> + >> /* >> * mlock_vma_folio() and munlock_vma_folio(): >> * should be called with vma's mmap_lock held for read or write, >
