From 337ed7eb5fada305c7d5bf168cf5032f825faddf Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Fri, 15 Jan 2016 16:55:15 -0800 Subject: [PATCH] mm/ksm.c: mark stable page dirty The MADV_FREE patchset changes page reclaim to simply free a clean anonymous page with no dirty ptes, instead of swapping it out; but KSM uses clean write-protected ptes to reference the stable ksm page. So be sure to mark that page dirty, so it's never mistakenly discarded. [hughd@google.com: adjusted comments] Signed-off-by: Minchan Kim Acked-by: Hugh Dickins Cc: "James E.J. Bottomley" Cc: "Kirill A. Shutemov" Cc: Shaohua Li Cc: Cc: Andrea Arcangeli Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Catalin Marinas Cc: Chen Gang Cc: Chris Zankel Cc: Daniel Micay Cc: Darrick J. Wong Cc: David S. Miller Cc: Helge Deller Cc: Ivan Kokshaysky Cc: Jason Evans Cc: Johannes Weiner Cc: KOSAKI Motohiro Cc: Kirill A. Shutemov Cc: Matt Turner Cc: Max Filippov Cc: Mel Gorman Cc: Michael Kerrisk Cc: Michal Hocko Cc: Mika Penttil Cc: Ralf Baechle Cc: Richard Henderson Cc: Rik van Riel Cc: Roland Dreier Cc: Russell King Cc: Shaohua Li Cc: Will Deacon Cc: Wu Fengguang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/ksm.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/ksm.c b/mm/ksm.c index 80c29b1b2b8a..ca6d2a06a615 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1013,6 +1013,12 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, */ set_page_stable_node(page, NULL); mark_page_accessed(page); + /* + * Page reclaim just frees a clean page with no dirty + * ptes: make sure that the ksm page would be swapped. + */ + if (!PageDirty(page)) + SetPageDirty(page); err = 0; } else if (pages_identical(page, kpage)) err = replace_page(vma, page, kpage, orig_pte); -- 2.20.1