From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f48.google.com (mail-pb0-f48.google.com [209.85.160.48]) by kanga.kvack.org (Postfix) with ESMTP id A6ACD6B0031 for ; Wed, 25 Sep 2013 04:31:11 -0400 (EDT) Received: by mail-pb0-f48.google.com with SMTP id ma3so5718175pbc.35 for ; Wed, 25 Sep 2013 01:31:11 -0700 (PDT) Received: by mail-ve0-f181.google.com with SMTP id oy12so4516570veb.12 for ; Wed, 25 Sep 2013 01:31:08 -0700 (PDT) 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 Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Weijie Yang Cc: Minchan Kim , Bob Liu , Seth Jennings , Linux-MM , Linux-Kernel 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, 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