From 982785c6b05a82c01e90687b7e25ee87c8970b2e Mon Sep 17 00:00:00 2001 From: Ebru Akagunduz Date: Mon, 19 Sep 2016 14:44:04 -0700 Subject: [PATCH] mm, thp: fix leaking mapped pte in __collapse_huge_page_swapin() Currently, khugepaged does not permit swapin if there are enough young pages in a THP. The problem is when a THP does not have enough young pages, khugepaged leaks mapped ptes. This patch prohibits leaking mapped ptes. Link: http://lkml.kernel.org/r/1472820276-7831-1-git-send-email-ebru.akagunduz@gmail.com Signed-off-by: Ebru Akagunduz Suggested-by: Andrea Arcangeli Reviewed-by: Andrea Arcangeli Reviewed-by: Rik van Riel Cc: Vlastimil Babka Cc: Mel Gorman Cc: Kirill A. Shutemov Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/khugepaged.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 62339bf..728d779 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -882,6 +882,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, .pmd = pmd, }; + /* we only decide to swapin, if there is enough young ptes */ + if (referenced < HPAGE_PMD_NR/2) { + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); + return false; + } fe.pte = pte_offset_map(pmd, address); for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE; fe.pte++, fe.address += PAGE_SIZE) { @@ -889,11 +894,6 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, if (!is_swap_pte(pteval)) continue; swapped_in++; - /* we only decide to swapin, if there is enough young ptes */ - if (referenced < HPAGE_PMD_NR/2) { - trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); - return false; - } ret = do_swap_page(&fe, pteval); /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ -- 2.7.4