From a38c015f3156895b07e71d4e4414289f8a3b2745 Mon Sep 17 00:00:00 2001 From: Claudio Imbrenda Date: Tue, 10 Apr 2018 16:29:41 -0700 Subject: [PATCH] mm/ksm.c: fix inconsistent accounting of zero pages When using KSM with use_zero_pages, we replace anonymous pages containing only zeroes with actual zero pages, which are not anonymous. We need to do proper accounting of the mm counters, otherwise we will get wrong values in /proc and a BUG message in dmesg when tearing down the mm. Link: http://lkml.kernel.org/r/1522931274-15552-1-git-send-email-imbrenda@linux.vnet.ibm.com Fixes: e86c59b1b1 ("mm/ksm: improve deduplication of zero pages with colouring") Signed-off-by: Claudio Imbrenda Reviewed-by: Andrew Morton Cc: Andrea Arcangeli Cc: Minchan Kim Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Christian Borntraeger Cc: Gerald Schaefer Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/ksm.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/ksm.c b/mm/ksm.c index e8d6c6210b80..e3cbf9a92f3c 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1131,6 +1131,13 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, } else { newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), vma->vm_page_prot)); + /* + * We're replacing an anonymous page with a zero page, which is + * not anonymous. We need to do proper accounting otherwise we + * will get wrong values in /proc, and a BUG message in dmesg + * when tearing down the mm. + */ + dec_mm_counter(mm, MM_ANONPAGES); } flush_cache_page(vma, addr, pte_pfn(*ptep));