From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 27 Sep 2017 08:20:46 +0900 From: Minchan Kim To: Shaohua Li Cc: linux-mm@kvack.org, asavkov@redhat.com, Kernel-team@fb.com, Shaohua Li , stable@vger.kernel.org, Johannes Weiner , Hillf Danton , Hugh Dickins , Rik van Riel , Mel Gorman , Andrew Morton Subject: Re: [PATCH V3 2/2] mm: fix data corruption caused by lazyfree page Message-ID: <20170926232046.GB32370@bbox> References: <08c84256b007bf3f63c91d94383bd9eb6fee2daa.1506446061.git.shli@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <08c84256b007bf3f63c91d94383bd9eb6fee2daa.1506446061.git.shli@fb.com> Sender: owner-linux-mm@kvack.org List-ID: On Tue, Sep 26, 2017 at 10:26:26AM -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 page reclaim finds such > page, it will simply add the page to swap cache without pageout the page > to swap because the page is marked as clean. Next time, page fault will > read data from the swap slot which doesn't have the original data, so we > have a data corruption. To fix issue, we mark the page dirty and pageout > the page. > > However, we shouldn't dirty all pages which is clean and in swap cache. > swapin page is swap cache and clean too. So we only dirty page which is > added into swap cache in page reclaim, which shouldn't be swapin page. > As Minchan suggested, simply dirty the page in add_to_swap can do the > job. > > Reported-by: Artem Savkov > Fix: 802a3a92ad7a(mm: reclaim MADV_FREE pages) > Signed-off-by: Shaohua Li Acked-by: Minchan Kim -- 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