From: Zi Yan <[email protected]> COW on PUD THPs has the same behavior as COW on PMD THPs to avoid high COW overhead. As a result, do_huge_pmd_wp will see PMD-mapped PUD THPs, thus needs to count PUD mappings in total mapcount when calling page_trans_huge_map_swapcount in reuse_swap_page to avoid false positive. Change page_trans_huge_map_swapcount to get it right.
Signed-off-by: Zi Yan <[email protected]> --- include/linux/huge_mm.h | 5 +++++ mm/huge_memory.c | 13 +++++++++++++ mm/memory.c | 3 +-- mm/swapfile.c | 7 ++++++- 4 files changed, 25 insertions(+), 3 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index e5c68e680907..589e5af5a1c2 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -19,6 +19,7 @@ extern int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD extern void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud); extern int do_huge_pud_anonymous_page(struct vm_fault *vmf); +extern vm_fault_t do_huge_pud_wp_page(struct vm_fault *vmf, pud_t orig_pud); #else static inline void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) { @@ -27,6 +28,10 @@ extern int do_huge_pud_anonymous_page(struct vm_fault *vmf) { return VM_FAULT_FALLBACK; } +extern vm_fault_t do_huge_pud_wp_page(struct vm_fault *vmf, pud_t orig_pud) +{ + return VM_FAULT_FALLBACK; +} #endif extern vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 4a899e856088..9aa19aa643cd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1335,6 +1335,19 @@ void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) unlock: spin_unlock(vmf->ptl); } + +vm_fault_t do_huge_pud_wp_page(struct vm_fault *vmf, pud_t orig_pud) +{ + struct vm_area_struct *vma = vmf->vma; + + /* + * split pud directly. a whole pud page is not swappable, so there is + * no need to try reuse_swap_page + */ + __split_huge_pud(vma, vmf->pud, vmf->address, false, NULL); + return VM_FAULT_FALLBACK; +} + #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) diff --git a/mm/memory.c b/mm/memory.c index e0e0459c0caf..ab80d13807aa 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4141,9 +4141,8 @@ static vm_fault_t create_huge_pud(struct vm_fault *vmf) static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE - /* No support for anonymous transparent PUD pages yet */ if (vma_is_anonymous(vmf->vma)) - return VM_FAULT_FALLBACK; + return do_huge_pud_wp_page(vmf, orig_pud); if (vmf->vma->vm_ops->huge_fault) return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ diff --git a/mm/swapfile.c b/mm/swapfile.c index 495ecdbd7859..a6989b0c4d44 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1635,7 +1635,12 @@ static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount, /* hugetlbfs shouldn't call it */ VM_BUG_ON_PAGE(PageHuge(page), page); - if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) { + if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)) || + /* + * PMD-mapped PUD THP need to take PUD mappings into account by + * using page_trans_huge_mapcount + */ + unlikely(thp_order(page) == HPAGE_PUD_ORDER)) { mapcount = page_trans_huge_mapcount(page, total_mapcount); if (PageSwapCache(page)) swapcount = page_swapcount(page); -- 2.28.0
