linux-ext4 - Re: [PATCH 1/2] ext4: call WARN

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Date:	Fri, 25 Jan 2013 16:14:30 +0100 (CET)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
cc:	Lukáš Czerner <lczerner@...hat.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] ext4: call WARN_ON after the debug message

On Fri, 25 Jan 2013, Theodore Ts'o wrote:

> Date: Fri, 25 Jan 2013 10:09:48 -0500
> From: Theodore Ts'o <tytso@....edu>
> To: Lukáš Czerner <lczerner@...hat.com>
> Cc: linux-ext4@...r.kernel.org
> Subject: Re: [PATCH 1/2] ext4: call WARN_ON after the debug message
> 
> On Fri, Jan 25, 2013 at 10:22:44AM +0100, Lukáš Czerner wrote:
> > 
> > we can get the EIO error from ext4_map_blocks not only in the case
> > of hardware error. The extent tree might not be in consistent state,
> > or we could even ask for blocks outside the file system itself (I
> > believe I've seen this before) and I think that in those cases it
> > might be worth to all WARN_ON.
> 
> Sure, but in those cases, the file system is corrupt, and we should
> have thrown an ext4_error() in ext4_map_blocks().  The point is that a
> WARN_ON is only useful if there is a potential programming bug.  If we
> know for sure that it's caused by a file system corruption, then we
> don't want to throw a WARN_ON.
> 
> Even if there is a kerneloops.org replacement --- in fact, especially
> if there is kerneloops.org replacement --- we only want to throw
> WARN_ON's in cases where it's just a pedestrian file system
> corruption.  Otherwise we'll end up wasting a lot of time chasing down
> something which was caused by a hardware error, and needing to calm
> down users (and breathless, spectacularizing, irresponsible journalism
> from web sites such as Phoronix).
> 
> 					- Ted

Fair enough, I'll remove the WARN_ON and use ext4_warning() instead
of ext4_msg.

Thanks!
-Lukas