From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx200.postini.com [74.125.245.200]) by kanga.kvack.org (Postfix) with SMTP id BD2D26B0034 for ; Fri, 23 Aug 2013 13:56:03 -0400 (EDT) Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 23 Aug 2013 11:56:02 -0600 Received: from b01cxnp22035.gho.pok.ibm.com (b01cxnp22035.gho.pok.ibm.com [9.57.198.25]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id EAA85C90044 for ; Fri, 23 Aug 2013 13:55:57 -0400 (EDT) Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by b01cxnp22035.gho.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r7NHtxuS28639406 for ; Fri, 23 Aug 2013 17:55:59 GMT Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r7NHtx4e007052 for ; Fri, 23 Aug 2013 13:55:59 -0400 Date: Fri, 23 Aug 2013 10:22:29 -0500 From: Seth Jennings 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: Sender: owner-linux-mm@kvack.org List-ID: To: Weijie Yang Cc: Minchan Kim , Bob Liu , weijie.yang@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org 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, 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