diff options
| -rw-r--r-- | mm/huge_memory.c | 55 |
1 files changed, 42 insertions, 13 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 29bc6e4..cb7be11 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2117,7 +2117,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, { struct page *page; pte_t *_pte; - int referenced = 0, none = 0; + int none = 0; + bool referenced = false, writable = false; for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { pte_t pteval = *_pte; @@ -2127,7 +2128,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, else goto out; } - if (!pte_present(pteval) || !pte_write(pteval)) + if (!pte_present(pteval)) goto out; page = vm_normal_page(vma, address, pteval); if (unlikely(!page)) @@ -2137,9 +2138,6 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, VM_BUG_ON_PAGE(!PageAnon(page), page); VM_BUG_ON_PAGE(!PageSwapBacked(page), page); - /* cannot use mapcount: can't collapse if there's a gup pin */ - if (page_count(page) != 1) - goto out; /* * We can do it before isolate_lru_page because the * page can't be freed from under us. NOTE: PG_lock @@ -2148,6 +2146,29 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, */ if (!trylock_page(page)) goto out; + + /* + * cannot use mapcount: can't collapse if there's a gup pin. + * The page must only be referenced by the scanned process + * and page swap cache. + */ + if (page_count(page) != 1 + !!PageSwapCache(page)) { + unlock_page(page); + goto out; + } + if (pte_write(pteval)) { + writable = true; + } else { + if (PageSwapCache(page) && !reuse_swap_page(page)) { + unlock_page(page); + goto out; + } + /* + * Page is not in the swap cache. It can be collapsed + * into a THP. + */ + } + /* * Isolate the page to avoid collapsing an hugepage * currently in use by the VM. @@ -2164,9 +2185,9 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, /* If there is no mapped pte young don't collapse the page */ if (pte_young(pteval) || PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, address)) - referenced = 1; + referenced = true; } - if (likely(referenced)) + if (likely(referenced && writable)) return 1; out: release_pte_pages(pte, _pte); @@ -2519,11 +2540,12 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, { pmd_t *pmd; pte_t *pte, *_pte; - int ret = 0, referenced = 0, none = 0; + int ret = 0, none = 0; struct page *page; unsigned long _address; spinlock_t *ptl; int node = NUMA_NO_NODE; + bool writable = false, referenced = false; VM_BUG_ON(address & ~HPAGE_PMD_MASK); @@ -2542,8 +2564,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, else goto out_unmap; } - if (!pte_present(pteval) || !pte_write(pteval)) + if (!pte_present(pteval)) goto out_unmap; + if (pte_write(pteval)) + writable = true; + page = vm_normal_page(vma, _address, pteval); if (unlikely(!page)) goto out_unmap; @@ -2560,14 +2585,18 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, VM_BUG_ON_PAGE(PageCompound(page), page); if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) goto out_unmap; - /* cannot use mapcount: can't collapse if there's a gup pin */ - if (page_count(page) != 1) + /* + * cannot use mapcount: can't collapse if there's a gup pin. + * The page must only be referenced by the scanned process + * and page swap cache. + */ + if (page_count(page) != 1 + !!PageSwapCache(page)) goto out_unmap; if (pte_young(pteval) || PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, address)) - referenced = 1; + referenced = true; } - if (referenced) + if (referenced && writable) ret = 1; out_unmap: pte_unmap_unlock(pte, ptl); |