From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx125.postini.com [74.125.245.125]) by kanga.kvack.org (Postfix) with SMTP id 1B0E96B0032 for ; Fri, 23 Aug 2013 07:26:02 -0400 (EDT) Received: by mail-ie0-f176.google.com with SMTP id s9so580112iec.21 for ; Fri, 23 Aug 2013 04:26:01 -0700 (PDT) MIME-Version: 1.0 Date: Fri, 23 Aug 2013 19:26:01 +0800 Message-ID: Subject: [PATCH 0/4] zswap bugfix: memory leaks and other problem From: Weijie Yang Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim , Bob Liu , sjenning@linux.vnet.ibm.com Cc: weijie.yang@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org 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 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