From f0849ac0b8e072073ec5fcc7fadd05a77434364e Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Thu, 5 Apr 2018 16:22:35 -0700 Subject: [PATCH] mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one() For PTE-mapped THP, the compound THP has not been split to normal 4K pages yet, the whole THP is considered referenced if any one of sub page is referenced. When walking PTE-mapped THP by pvmw, all relevant PTEs will be checked to retrieve referenced bit. But, the current code just returns the result of the last PTE. If the last PTE has not referenced, the referenced flag will be cleared. Just set referenced when ptep{pmdp}_clear_young_notify() returns true. Link: http://lkml.kernel.org/r/1518212451-87134-1-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Yang Shi Reported-by: Gang Deng Suggested-by: Kirill A. Shutemov Reviewed-by: Andrew Morton Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_idle.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/page_idle.c b/mm/page_idle.c index 0a49374e6931..e412a63b2b74 100644 --- a/mm/page_idle.c +++ b/mm/page_idle.c @@ -65,11 +65,15 @@ static bool page_idle_clear_pte_refs_one(struct page *page, while (page_vma_mapped_walk(&pvmw)) { addr = pvmw.address; if (pvmw.pte) { - referenced = ptep_clear_young_notify(vma, addr, - pvmw.pte); + /* + * For PTE-mapped THP, one sub page is referenced, + * the whole THP is referenced. + */ + if (ptep_clear_young_notify(vma, addr, pvmw.pte)) + referenced = true; } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { - referenced = pmdp_clear_young_notify(vma, addr, - pvmw.pmd); + if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) + referenced = true; } else { /* unexpected pmd-mapped page? */ WARN_ON_ONCE(1);