From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx152.postini.com [74.125.245.152]) by kanga.kvack.org (Postfix) with SMTP id AE0226B004D for ; Wed, 11 Apr 2012 15:20:56 -0400 (EDT) Date: Wed, 11 Apr 2012 21:20:52 +0200 From: Michal Hocko Subject: Re: [PATCH] remove BUG() in possible but rare condition Message-ID: <20120411192052.GB24831@tiehlicka.suse.cz> References: <1334167824-19142-1-git-send-email-glommer@parallels.com> <20120411184845.GA24831@tiehlicka.suse.cz> 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: Linus Torvalds Cc: Glauber Costa , 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 On Wed 11-04-12 11:57:56, 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? I personally do not care as I do not allow anything to map at that area. It just seems that there are some callers who do not expect that the allocation fails. BUG at the allocation failure which dates back when it replaced buffer_error might have let to some assumptions (not good of course but we should better fix them. That being said I am not against the patch. BUG on an allocation failure just doesn't feel right... > > Linus > > -- > 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/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: email@kvack.org -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org