From: Michal Hocko <mhocko@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Glauber Costa <glommer@parallels.com>,
linux-kernel@vger.kernel.org, devel@openvz.org,
linux-mm@kvack.org, cgroups@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>,
kamezawa.hiroyu@jp.fujitsu.com, Greg Thelen <gthelen@google.com>,
Suleiman Souhlal <suleiman@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] remove BUG() in possible but rare condition
Date: Wed, 11 Apr 2012 23:26:22 +0200 [thread overview]
Message-ID: <20120411212621.GD24831@tiehlicka.suse.cz> (raw)
In-Reply-To: <20120411141244.2839d9a8.akpm@linux-foundation.org>
On Wed 11-04-12 14:12:44, Andrew Morton wrote:
> On Wed, 11 Apr 2012 17:51:57 -0300
> Glauber Costa <glommer@parallels.com> wrote:
>
> > On 04/11/2012 05:26 PM, Andrew Morton wrote:
> > >>
> > >> > failed:
> > >> > - BUG();
> > >> > unlock_page(page);
> > >> > page_cache_release(page);
> > >> > return NULL;
> > > Cute.
> > >
> > > AFAICT what happened was that in my April 2002 rewrite of this code I
> > > put a non-fatal buffer_error() warning in that case to tell us that
> > > something bad happened.
> > >
> > > Years later we removed the temporary buffer_error() and mistakenly
> > > replaced that warning with a BUG(). Only it*can* happen.
> > >
> > > We can remove the BUG() and fix up callers, or we can pass retry=1 into
> > > alloc_page_buffers(), so grow_dev_page() "cannot fail". Immortal
> > > functions are a silly fiction, so we should remove the BUG() and fix up
> > > callers.
> > >
> > Any particular caller you are concerned with ?
>
> Didn't someone see a buggy caller in btrfs?
No I missed that __getblk (__getblk_slow) returns NULL only if
grow_buffers < 0 while it returns 0 for the allocation failure.
Sorry for confusion.
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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next prev parent reply other threads:[~2012-04-11 21:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-11 18:10 Glauber Costa
2012-04-11 18:48 ` Michal Hocko
2012-04-11 18:57 ` Linus Torvalds
2012-04-11 19:02 ` Glauber Costa
2012-04-11 19:25 ` Michal Hocko
2012-04-11 19:20 ` Michal Hocko
2012-04-11 19:48 ` Don Morris
2012-04-11 21:33 ` Jiri Kosina
2012-04-11 18:59 ` Glauber Costa
2012-04-11 20:26 ` Andrew Morton
2012-04-11 20:51 ` Glauber Costa
2012-04-11 21:12 ` Andrew Morton
2012-04-11 21:26 ` Michal Hocko [this message]
2012-04-12 9:24 ` Michal Hocko
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