From: Claudio Imbrenda imbrenda@linux.vnet.ibm.com Subject: 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.vn... Fixes: e86c59b1b1 ("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 ---
mm/ksm.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff -puN mm/ksm.c~mm-ksm-fix-inconsistent-accounting-of-zero-pages mm/ksm.c --- a/mm/ksm.c~mm-ksm-fix-inconsistent-accounting-of-zero-pages +++ a/mm/ksm.c @@ -1131,6 +1131,13 @@ static int replace_page(struct vm_area_s } 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)); _