From: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx Fixes: e86c59b1b1 ("mm/ksm: improve deduplication of zero pages with colouring") Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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)); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
