linux-kernel - Re: Warning and BUG with btrfs and corrupted image

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Message-ID: <20090204182951.GC4797@elf.ucw.cz>
Date:	Wed, 4 Feb 2009 19:29:51 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	Christoph Hellwig <hch@...radead.org>,
	Eric Sesterhenn <snakebyte@....de>,
	Chris Mason <chris.mason@...cle.com>,
	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: Warning and BUG with btrfs and corrupted image

On Sun 2009-02-01 12:40:50, Dave Chinner wrote:
> On Mon, Jan 26, 2009 at 05:27:11PM +0100, Pavel Machek wrote:
> > On Wed 2009-01-21 15:00:42, Dave Chinner wrote:
> > > On Tue, Jan 20, 2009 at 11:20:19PM +0100, Pavel Machek wrote:
> > > > On Tue 2009-01-20 08:28:29, Christoph Hellwig wrote:
> > > > > I think that was the issue with the debug builds.  If you do this
> > > > > testing always do it without CONFIG_XFS_DEBUG set as with that option
> > > > > we intentionally panic on detected disk corruptions.
> > > > 
> > > > Uhuh, *_DEBUG options are not supposed to make kernel less
> > > > stable/robust. Should that crashing functionality be guarded with
> > > > command line option or something? ext2 has errors=panic mount
> > > > option...
> > > 
> > > No, it's a debugging option that is described as:
> > > 
> > > 	"Say N unless you are an XFS developer, or you play one on TV."
> > > 
> > > Seriously, if you aren't trying to develop XFS stuff then *don't turn it
> > > on*.
> > 
> > What about this, then?
> 
> ....
> 
> > +	  Turning this option on will result in kernel panicking any time
> > +	  it detects on-disk corruption.
> 
> Thin end of a wedge. There's a couple of thousand conditions that
> CONFIG_XFS_DEBUG introduces kernel panics on:
> 
> $ grep -r ASSERT fs/xfs |wc -l
> 2095
> 
> 
> CONFIG_*_DEBUG means include *debug* code there to help developers,
> including adding additional failure tests into the kernel. Besides,
> which bit of "don't turn it on unless you are an XFS developer"
> don't you understand?

Yes, but DEBUG code is normally to help debugging, not to crash
kernels. IMO xfs should use errors=panic mount option as ext3 does,
but...
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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