linux-ext4 - Re: BUG_ON at mballoc.c:3752

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Message-ID: <20080208031408.GA7111@skywalker>
Date:	Fri, 8 Feb 2008 08:44:08 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Mingming Cao <cmm@...ibm.com>
Cc:	Eric Sesterhenn <snakebyte@....de>, linux-ext4@...r.kernel.org,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Eric Sandeen <sandeen@...hat.com>
Subject: Re: BUG_ON at mballoc.c:3752

On Thu, Feb 07, 2008 at 05:30:48PM -0800, Mingming Cao wrote:
> On Thu, 2008-02-07 at 18:25 +0530, Aneesh Kumar K.V wrote:
> 
> > ext4: Don't panic in case of corrupt bitmap
> > 
> > From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> > 
> > Multiblock allocator was calling BUG_ON in many case if the free and used
> > blocks count obtained looking at the bitmap is different from what
> > the allocator internally accounted for. Use ext4_error in such case
> > and don't panic the system.
> > 
> 
> There seems a lot of BUG_ON() and BUG() in mballoc code, other than this
> case. Should it always panic the whole system in those cases? Perhaps
> replacing with ext4_error() or some cases just WARN_ON is enough.
> 

I had looked at the BUG_ON in mballoc code and found them very useful
while stabilizing the mballoc code. It helped to catch wrong usage of
functions. Most of the BUG_ON are there to make sure we call the API
with the lock held or the API should not return value greater than 'x'
Should not call the function with a particular argument as NULL ...etc
kind of thing. So i would suggest to keep them as such.


-aneesh
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