From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758281AbcH3LBP (ORCPT ); Tue, 30 Aug 2016 07:01:15 -0400 Received: from mail-pa0-f67.google.com ([209.85.220.67]:36707 "EHLO mail-pa0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751629AbcH3LAb (ORCPT ); Tue, 30 Aug 2016 07:00:31 -0400 From: wei.guo.simon@gmail.com To: linux-mm@kvack.org Cc: Alexey Klimov , Andrew Morton , Eric B Munson , Geert Uytterhoeven , "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Mel Gorman , Michal Hocko , Shuah Khan , Simon Guo , Thierry Reding , Vlastimil Babka Subject: [PATCH 2/4] mm: mlock: avoid increase mm->locked_vm on mlock() when already mlock2(,MLOCK_ONFAULT) Date: Tue, 30 Aug 2016 18:59:39 +0800 Message-Id: <1472554781-9835-3-git-send-email-wei.guo.simon@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1472554781-9835-1-git-send-email-wei.guo.simon@gmail.com> References: <1472554781-9835-1-git-send-email-wei.guo.simon@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Simon Guo When one vma was with flag VM_LOCKED|VM_LOCKONFAULT (by invoking mlock2(,MLOCK_ONFAULT)), it can again be populated with mlock() with VM_LOCKED flag only. There is a hole in mlock_fixup() which increase mm->locked_vm twice even the two operations are on the same vma and both with VM_LOCKED flags. The issue can be reproduced by following code: mlock2(p, 1024 * 64, MLOCK_ONFAULT); //VM_LOCKED|VM_LOCKONFAULT mlock(p, 1024 * 64); //VM_LOCKED Then check the increase VmLck field in /proc/pid/status(to 128k). When vma is set with different vm_flags, and the new vm_flags is with VM_LOCKED, it is not necessarily be a "new locked" vma. This patch corrects this bug by prevent mm->locked_vm from increment when old vm_flags is already VM_LOCKED. Signed-off-by: Simon Guo --- mm/mlock.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/mlock.c b/mm/mlock.c index 9283187..df29aad 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -516,6 +516,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev, int nr_pages; int ret = 0; int lock = !!(newflags & VM_LOCKED); + vm_flags_t old_flags = vma->vm_flags; if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm)) @@ -550,6 +551,8 @@ success: nr_pages = (end - start) >> PAGE_SHIFT; if (!lock) nr_pages = -nr_pages; + else if (old_flags & VM_LOCKED) + nr_pages = 0; mm->locked_vm += nr_pages; /* -- 1.8.3.1