Messages in this thread | | | Date | Wed, 4 May 2022 10:49:23 +0800 | Subject | Re: [PATCH v2 3/3] mm: rmap: Use flush_cache_range() to flush cache for hugetlb pages | From | Baolin Wang <> |
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On 5/4/2022 4:17 AM, Mike Kravetz wrote: > On 4/27/22 03:52, Baolin Wang wrote: >> Now we will use flush_cache_page() to flush cache for anonymous hugetlb >> pages when unmapping or migrating a hugetlb page mapping, but the >> flush_cache_page() only handles a PAGE_SIZE range on some architectures >> (like arm32, arc and so on), which will cause potential cache issues. >> Thus change to use flush_cache_range() to cover the whole size of a >> hugetlb page. >> >> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> --- >> mm/rmap.c | 90 ++++++++++++++++++++++++++++++++++----------------------------- >> 1 file changed, 48 insertions(+), 42 deletions(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 4f0d115..6fdd198 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1528,13 +1528,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> anon_exclusive = folio_test_anon(folio) && >> PageAnonExclusive(subpage); >> >> - if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) { >> - /* >> - * To call huge_pmd_unshare, i_mmap_rwsem must be >> - * held in write mode. Caller needs to explicitly >> - * do this outside rmap routines. >> - */ >> - VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + if (folio_test_hugetlb(folio)) { >> /* >> * huge_pmd_unshare may unmap an entire PMD page. >> * There is no way of knowing exactly which PMDs may >> @@ -1544,22 +1538,31 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> */ >> flush_cache_range(vma, range.start, range.end); >> >> - if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> - flush_tlb_range(vma, range.start, range.end); >> - mmu_notifier_invalidate_range(mm, range.start, >> - range.end); >> - >> + if (!folio_test_anon(folio)) { >> /* >> - * The ref count of the PMD page was dropped >> - * which is part of the way map counting >> - * is done for shared PMDs. Return 'true' >> - * here. When there is no other sharing, >> - * huge_pmd_unshare returns false and we will >> - * unmap the actual page and drop map count >> - * to zero. >> + * To call huge_pmd_unshare, i_mmap_rwsem must be >> + * held in write mode. Caller needs to explicitly >> + * do this outside rmap routines. >> */ >> - page_vma_mapped_walk_done(&pvmw); >> - break; >> + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + >> + if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> + flush_tlb_range(vma, range.start, range.end); >> + mmu_notifier_invalidate_range(mm, range.start, >> + range.end); >> + >> + /* >> + * The ref count of the PMD page was dropped >> + * which is part of the way map counting >> + * is done for shared PMDs. Return 'true' >> + * here. When there is no other sharing, >> + * huge_pmd_unshare returns false and we will >> + * unmap the actual page and drop map count >> + * to zero. >> + */ >> + page_vma_mapped_walk_done(&pvmw); >> + break; >> + } >> } >> } else { >> flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); >> @@ -1885,13 +1888,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, >> anon_exclusive = folio_test_anon(folio) && >> PageAnonExclusive(subpage); >> >> - if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) { >> - /* >> - * To call huge_pmd_unshare, i_mmap_rwsem must be >> - * held in write mode. Caller needs to explicitly >> - * do this outside rmap routines. >> - */ >> - VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + if (folio_test_hugetlb(folio)) { >> /* >> * huge_pmd_unshare may unmap an entire PMD page. >> * There is no way of knowing exactly which PMDs may >> @@ -1901,22 +1898,31 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, >> */ >> flush_cache_range(vma, range.start, range.end); >> >> - if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> - flush_tlb_range(vma, range.start, range.end); >> - mmu_notifier_invalidate_range(mm, range.start, >> - range.end); >> - >> + if (!folio_test_anon(folio)) { >> /* >> - * The ref count of the PMD page was dropped >> - * which is part of the way map counting >> - * is done for shared PMDs. Return 'true' >> - * here. When there is no other sharing, >> - * huge_pmd_unshare returns false and we will >> - * unmap the actual page and drop map count >> - * to zero. >> + * To call huge_pmd_unshare, i_mmap_rwsem must be >> + * held in write mode. Caller needs to explicitly >> + * do this outside rmap routines. >> */ >> - page_vma_mapped_walk_done(&pvmw); >> - break; >> + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + >> + if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> + flush_tlb_range(vma, range.start, range.end); >> + mmu_notifier_invalidate_range(mm, range.start, >> + range.end); >> + >> + /* >> + * The ref count of the PMD page was dropped >> + * which is part of the way map counting >> + * is done for shared PMDs. Return 'true' >> + * here. When there is no other sharing, >> + * huge_pmd_unshare returns false and we will >> + * unmap the actual page and drop map count >> + * to zero. >> + */ >> + page_vma_mapped_walk_done(&pvmw); >> + break; >> + } >> } >> } else { >> flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); > > Thanks, > The code looks fine. It is unfortunate that we need so many levels of > indenting and exceed 80 columns. But, that is OK.
I'll do a cleanup to make it more readable with factoring the hugetlb case into a new function after the fix series[1].
[1] https://lore.kernel.org/linux-arm-kernel/20220503120343.6264e126@thinkpad/T/
> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> > > I see you have a followup series to address the call to ptep_clear_flush() > for hugetlb pages not unmapped via huge_pmd_share and will take a look at > that soon.
Thanks.
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