Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932123Ab3HWR4H (ORCPT ); Fri, 23 Aug 2013 13:56:07 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:53289 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932109Ab3HWR4F (ORCPT ); Fri, 23 Aug 2013 13:56:05 -0400 Date: Fri, 23 Aug 2013 10:22:29 -0500 From: Seth Jennings To: Weijie Yang Cc: Minchan Kim , Bob Liu , weijie.yang@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/4] zswap bugfix: memory leaks and other problem Message-ID: <20130823152229.GA5439@variantweb.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13082317-7182-0000-0000-00000831CB00 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1927 Lines: 47 On Fri, Aug 23, 2013 at 07:26:01PM +0800, Weijie Yang wrote: > This patch series fix a few bugs in zswap based on Linux-3.11-rc6. > > Corresponding mail thread see: lkml.org/lkml/2013/8/18/59 . > > These issues fixed are: > 1. memory leaks when re-swapon > 2. potential problem which store and reclaim functions is called recursively > 3. memory leaks when invalidate and reclaim occur simultaneously > 4. unnecessary page scanning Thanks for the patches! Patches 2-4 have whitespace corruption (line wrapping) probably caused by your mail agent. You might check Documentation/email-clients.txt on how to prevent this. Seth > > Issues discussed in that mail thread NOT fixed as it happens rarely or > not a big problem: > 1. a "theoretical race condition" when reclaim page > when a handle alloced from zbud, zbud considers this handle is used > validly by upper(zswap) and can be a candidate for reclaim. > But zswap has to initialize it such as setting swapentry and adding > it to rbtree. so there is a race condition, such as: > thread 0: obtain handle x from zbud_alloc > thread 1: zbud_reclaim_page is called > thread 1: callback zswap_writeback_entry to reclaim handle x > thread 1: get swpentry from handle x (it is random value now) > thread 1: bad thing may happen > thread 0: initialize handle x with swapentry > > 2. frontswap_map bitmap not cleared after zswap reclaim > Frontswap uses frontswap_map bitmap to track page in "backend" implementation, > when zswap reclaim a page, the corresponding bitmap record is not cleared. > > mm/zswap.c | 35 ++++++++++++++++++++++++----------- > 1 files changed, 24 insertions(+), 11 deletions(-) > -- 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/