From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753323AbbFCGQe (ORCPT ); Wed, 3 Jun 2015 02:16:34 -0400 Received: from lgeamrelo02.lge.com ([156.147.1.126]:56160 "EHLO lgeamrelo02.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753031AbbFCGPt (ORCPT ); Wed, 3 Jun 2015 02:15:49 -0400 X-Original-SENDERIP: 10.177.222.143 X-Original-MAILFROM: minchan@kernel.org From: Minchan Kim To: Andrew Morton Cc: Hugh Dickins , Rik van Riel , Mel Gorman , Michal Hocko , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , Cyrill Gorcunov , Pavel Emelyanov , Yalin Wang Subject: [RFC 3/6] mm: mark dirty bit on swapped-in page Date: Wed, 3 Jun 2015 15:15:42 +0900 Message-Id: <1433312145-19386-4-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1433312145-19386-1-git-send-email-minchan@kernel.org> References: <1433312145-19386-1-git-send-email-minchan@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Basically, MADV_FREE relys on the dirty bit in page table entry to decide whether VM allows to discard the page or not. IOW, if page table entry includes marked dirty bit, VM shouldn't discard the page. However, if swap-in by read fault happens, page table entry point out the page doesn't have marked dirty bit so MADV_FREE might discard the page wrongly. To fix the problem, this patch marks page table entry of page swapping-in as dirty so VM shouldn't discard the page suddenly under us. With MADV_FREE point of view, marking dirty unconditionally is no problem because we dropped swapped page in MADV_FREE sycall context(ie, Look at madvise_free_pte_range) so every swapping-in pages are no MADV_FREE hinted pages. Cc: Hugh Dickins Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Reported-by: Yalin Wang Signed-off-by: Minchan Kim --- mm/memory.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 8a2fc9945b46..d1709f763152 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2557,9 +2557,11 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, inc_mm_counter_fast(mm, MM_ANONPAGES); dec_mm_counter_fast(mm, MM_SWAPENTS); - pte = mk_pte(page, vma->vm_page_prot); + + /* Mark dirty bit of page table because MADV_FREE relies on it */ + pte = pte_mkdirty(mk_pte(page, vma->vm_page_prot)); if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) { - pte = maybe_mkwrite(pte_mkdirty(pte), vma); + pte = maybe_mkwrite(pte, vma); flags &= ~FAULT_FLAG_WRITE; ret |= VM_FAULT_WRITE; exclusive = 1; -- 1.9.1