From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id A57716B0038 for ; Mon, 25 Sep 2017 01:07:15 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id y29so11640327pff.6 for ; Sun, 24 Sep 2017 22:07:15 -0700 (PDT) Received: from lgeamrelo13.lge.com (LGEAMRELO13.lge.com. [156.147.23.53]) by mx.google.com with ESMTP id t65si3535615pgb.16.2017.09.24.22.07.13 for ; Sun, 24 Sep 2017 22:07:14 -0700 (PDT) Date: Mon, 25 Sep 2017 14:07:11 +0900 From: Minchan Kim Subject: Re: [PATCH V2 1/2] mm: avoid marking swap cached page as lazyfree Message-ID: <20170925050711.GA27410@bbox> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Shaohua Li Cc: linux-mm@kvack.org, Artem Savkov , Kernel-team@fb.com, Shaohua Li , stable@vger.kernel.org, Johannes Weiner , Michal Hocko , Hillf Danton , Hugh Dickins , Mel Gorman , Andrew Morton On Fri, Sep 22, 2017 at 11:46:30AM -0700, Shaohua Li wrote: > From: Shaohua Li > > MADV_FREE clears pte dirty bit and then marks the page lazyfree (clear > SwapBacked). There is no lock to prevent the page is added to swap cache > between these two steps by page reclaim. If the page is added to swap > cache, marking the page lazyfree will confuse page fault if the page is > reclaimed and refault. If page is added to swapcache while it stays lru_lazyfree_pvec, it ends up having !PG_swapbacked, PG_swapcache and !PG_dirty. Most important thing is PG_dirty. Without it, VM will reclaim the page without *writeback* so we lose the data. Although we prevent the page adding to swapcache, we lose the data unless we apply [2/2] so this patch alone doesn't fix the problem. That's why I said to you we don't need to separate patches. > > Reported-and-tested-by: Artem Savkov > Fix: 802a3a92ad7a(mm: reclaim MADV_FREE pages) > Signed-off-by: Shaohua Li > Cc: stable@vger.kernel.org > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Hillf Danton > Cc: Minchan Kim > Cc: Hugh Dickins > Cc: Mel Gorman > Cc: Andrew Morton > Reviewed-by: Rik van Riel > --- > mm/swap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 9295ae9..a77d68f 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -575,7 +575,7 @@ static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec, > void *arg) > { > if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) && > - !PageUnevictable(page)) { > + !PageSwapCache(page) && !PageUnevictable(page)) { > bool active = PageActive(page); > > del_page_from_lru_list(page, lruvec, > @@ -665,7 +665,7 @@ void deactivate_file_page(struct page *page) > void mark_page_lazyfree(struct page *page) > { > if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) && > - !PageUnevictable(page)) { > + !PageSwapCache(page) && !PageUnevictable(page)) { > struct pagevec *pvec = &get_cpu_var(lru_lazyfree_pvecs); > > get_page(page); > -- > 2.9.5 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org