linux-ext4 - Re: ext4fs error "ext4_mb_generate_buddy:741:group 16, 8160 clusters in bitmap, 4064 in gd" (with repro)

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Message-ID: <20120816200032.GE31346@thunk.org>
Date:	Thu, 16 Aug 2012 16:00:32 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Lukáš Czerner <lczerner@...hat.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	"Linux Kernel Mailinlinux-ext4@...r.kernel.orgg List" 
	<linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org
Subject: Re: ext4fs error "ext4_mb_generate_buddy:741:group 16, 8160 clusters
 in bitmap, 4064 in gd" (with repro)

On Thu, Aug 16, 2012 at 04:28:07PM +0200, Lukáš Czerner wrote:
> 
> After a little bit of tracing with the systemtap and blktrace ext4
> does not seem to be doing anything wrong and yet we get part of the
> block bitmap trimmed. This lead me to the scsi_debug driver itself
> and indeed it seems that we have off-by-one bug there in the
> unamp_region() which is causing the problem.

Thanks for finding this --- I was getting scared that ext4 users were
losing data in production.  It's good to know it was just a bug in the
scsi_debug driver.

						- Ted
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