From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752026AbaAMXzd (ORCPT ); Mon, 13 Jan 2014 18:55:33 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:53640 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951AbaAMXz3 (ORCPT ); Mon, 13 Jan 2014 18:55:29 -0500 Date: Mon, 13 Jan 2014 15:55:27 -0800 From: Andrew Morton To: Minchan Kim Cc: linux-kernel@vger.kernel.org, Nitin Gupta , Jerome Marchand , Sergey Senozhatsky , stable Subject: Re: [PATCH 1/7] zram: fix race between reset and flushing pending work Message-Id: <20140113155527.5731d24ca86f01bfd5ec716f@linux-foundation.org> In-Reply-To: <1389611942-15544-2-git-send-email-minchan@kernel.org> References: <1389611942-15544-1-git-send-email-minchan@kernel.org> <1389611942-15544-2-git-send-email-minchan@kernel.org> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 Jan 2014 20:18:56 +0900 Minchan Kim wrote: > Dan and Sergey reported that there is a racy between reset and > flushing of pending work so that it could make oops by freeing > zram->meta in reset while zram_slot_free can access zram->meta > if new request is adding during the race window. > > This patch moves flush after taking init_lock so it prevents > new request so that it closes the race. > > .. > > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -553,14 +553,14 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity) > size_t index; > struct zram_meta *meta; > > - flush_work(&zram->free_work); > - > down_write(&zram->init_lock); > if (!zram->init_done) { > up_write(&zram->init_lock); > return; > } > > + flush_work(&zram->free_work); > + > meta = zram->meta; > zram->init_done = 0; This makes zram.lock nest inside zram.init_lock, which afaict is new behaviour. That all seems OK and logical - has it been well tested with lockdep?