Commit 982785c6 authored Sep 19, 2016 by Ebru Akagunduz Committed by Linus Torvalds Sep 19, 2016

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 <ebru.akagunduz@gmail.com>
Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c131f751

mm/khugepaged.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -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 */

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