Commit a38c015f authored Apr 10, 2018 by Claudio Imbrenda Committed by Linus Torvalds Apr 11, 2018

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: e86c59b1 ("mm/ksm: improve deduplication of zero pages with colouring")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 8a97ea54

mm/ksm.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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));