From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933036Ab2DKTZ6 (ORCPT ); Wed, 11 Apr 2012 15:25:58 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55983 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760945Ab2DKTZ4 (ORCPT ); Wed, 11 Apr 2012 15:25:56 -0400 Date: Wed, 11 Apr 2012 21:25:54 +0200 From: Michal Hocko To: Glauber Costa Cc: Linus Torvalds , linux-kernel@vger.kernel.org, devel@openvz.org, linux-mm@kvack.org, cgroups@vger.kernel.org, Johannes Weiner , kamezawa.hiroyu@jp.fujitsu.com, Greg Thelen , Suleiman Souhlal , Andrew Morton Subject: Re: [PATCH] remove BUG() in possible but rare condition Message-ID: <20120411192554.GC24831@tiehlicka.suse.cz> References: <1334167824-19142-1-git-send-email-glommer@parallels.com> <20120411184845.GA24831@tiehlicka.suse.cz> <4F85D53B.1070806@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F85D53B.1070806@parallels.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 11-04-12 16:02:19, Glauber Costa wrote: > On 04/11/2012 03:57 PM, Linus Torvalds wrote: > >On Wed, Apr 11, 2012 at 11:48 AM, Michal Hocko wrote: > >> > >>I am not familiar with the code much but a trivial call chain walk up to > >>write_dev_supers (in btrfs) shows that we do not check for the return value > >>from __getblk so we would nullptr and there might be more. > >>I guess these need some treat before the BUG might be removed, right? > > > >Well, realistically, isn't BUG() as bad as a NULL pointer dereference? > > > >Do you care about the exact message on the screen when your machine dies? > Not particular, but I don't see why (I might be wrong) it would > necessarily lead to a NULL pointer dereference. Ahh, OK scratch that. I have misread __getblk_slow which returns NULL only if grow_buffers returned with < 0 which doesn't happen for the allocation failure. Sorry about noise -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic