From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx140.postini.com [74.125.245.140]) by kanga.kvack.org (Postfix) with SMTP id 10E4D6B0069 for ; Thu, 30 Aug 2012 13:55:50 -0400 (EDT) Received: by dadi14 with SMTP id i14so1500784dad.14 for ; Thu, 30 Aug 2012 10:55:49 -0700 (PDT) Date: Fri, 31 Aug 2012 02:55:43 +0900 From: Minchan Kim Subject: Re: [PATCH] staging: zcache: fix cleancache race condition with shrinker Message-ID: <20120830175543.GA3534@barrios> References: <1346277525-22062-1-git-send-email-sjenning@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1346277525-22062-1-git-send-email-sjenning@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Seth Jennings Cc: Greg Kroah-Hartman , Andrew Morton , Nitin Gupta , Konrad Rzeszutek Wilk , Dan Magenheimer , Robert Jennings , Xiao Guangrong , linux-mm@kvack.org, linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org On Wed, Aug 29, 2012 at 04:58:45PM -0500, Seth Jennings wrote: > This patch fixes a race condition that results in memory > corruption when using cleancache. > > The race exists between the zcache shrinker handler, > shrink_zcache_memory() and cleancache_get_page(). > > In most cases, the shrinker will both evict a zbpg > from its buddy list and flush it from tmem before a > cleancache_get_page() occurs on that page. A subsequent > cleancache_get_page() will fail in the tmem layer. > > In the rare case that two occur together and the > cleancache_get_page() path gets through the tmem > layer before the shrinker path can flush tmem, > zbud_decompress() does a check to see if the zbpg is a > "zombie", i.e. not on a buddy list, which means the shrinker > is in the process of reclaiming it. If the zbpg is a zombie, > zbud_decompress() returns -EINVAL. > > However, this return code is being ignored by the caller, > zcache_pampd_get_data_and_free(), which results in the > caller of cleancache_get_page() thinking that the page has > been properly retrieved when it has not. > > This patch modifies zcache_pampd_get_data_and_free() to > convey the failure up the stack so that the caller of > cleancache_get_page() knows the page retrieval failed. > > --- > Based on v3.6-rc3. > > This needs to be applied to stable trees as well. > zcache-main.c was named zcache.c before v3.1, so > I'm not sure how you want to handle trees earlier > than that. > > Signed-off-by: Seth Jennings Reviewed-by: Minchan Kim Thanks! -- 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