Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753330Ab3IYIbL (ORCPT ); Wed, 25 Sep 2013 04:31:11 -0400 Received: from mail-vc0-f179.google.com ([209.85.220.179]:44727 "EHLO mail-vc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774Ab3IYIbJ (ORCPT ); Wed, 25 Sep 2013 04:31:09 -0400 MIME-Version: 1.0 In-Reply-To: References: <52118042.30101@oracle.com> <20130819054742.GA28062@bbox> <20130821074939.GE3022@bbox> Date: Wed, 25 Sep 2013 16:31:08 +0800 Message-ID: Subject: Re: [BUG REPORT] ZSWAP: theoretical race condition issues From: Bob Liu To: Weijie Yang Cc: Minchan Kim , Bob Liu , Seth Jennings , Linux-MM , Linux-Kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1177 Lines: 33 On Wed, Sep 25, 2013 at 4:09 PM, Weijie Yang wrote: > I think I find a new issue, for integrity of this mail thread, I reply > to this mail. > > It is a concurrence issue either, when duplicate store and reclaim > concurrentlly. > > zswap entry x with offset A is already stored in zswap backend. > Consider the following scenario: > > thread 0: reclaim entry x (get refcount, but not call zswap_get_swap_cache_page) > > thread 1: store new page with the same offset A, alloc a new zswap entry y. > store finished. shrink_page_list() call __remove_mapping(), and now > it is not in swap_cache > But I don't think swap layer will call zswap with the same offset A. > thread 0: zswap_get_swap_cache_page called. old page data is added to swap_cache > > Now, swap cache has old data rather than new data for offset A. > error will happen If do_swap_page() get page from swap_cache. > -- Regards, --Bob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/