linux-ext4 - Re: ext3_valid_block_bitmap: Invalid block bitmap in 2.6.25rc in memory

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Date:	Tue, 15 Apr 2008 04:04:22 -0600
From:	Andreas Dilger <adilger@....com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Mingming Cao <cmm@...ibm.com>, Andi Kleen <andi@...stfloor.org>,
	linux-ext4@...r.kernel.org
Subject: Re: ext3_valid_block_bitmap: Invalid block bitmap in 2.6.25rc in	memory

On Apr 15, 2008  14:17 +0530, Aneesh Kumar K.V wrote:
> On Mon, Apr 14, 2008 at 05:40:59PM -0600, Andreas Dilger wrote:
> > On Apr 14, 2008  07:50 -0700, Mingming Cao wrote:
> > > On Sat, 2008-04-12 at 22:57 +0200, Andi Kleen wrote:
> > > > FYI, a system here running various 2.6.25rc kernels (latest upto rc7-git6) 
> > > > with longer uptimes suddenly decided to fsck one of its file systems
> > > > due to an error after reboot.
> > > > 
> > > > The error causing this was:
> > > > 
> > > > kernel: EXT3-fs error (device dm-0): ext3_valid_block_bitmap: Invalid block bitmap - block_group = 285, block = 9338882
> > > > 
> > > > detected by the 2.6.25rc7-git6 kernel.
> > > > 
> > > > I don't see any ill effects from it and fsck didn't find anything wrong
> > > > so it must have been something spurious in memory only (or fsck
> > > > fails to check for this condition, but that is hard to imagine) 
> > > 
> > > The ext3_valid_block_bitmap() is to check whether the block or inode
> > > bitmap block is marked as "used" in the block group bitmap, to prevent
> > > allocating blocks from these system meta data blocks.
> > 
> > Right.
> > 
> > > The error messages seems indicating that one of the block group meta
> > > data is corrupted, but I don't why fsck doesn't catch this, Andreas?
> > 
> > It might have been corrupted on read (e.g. bad cable, or bad/wrong
> > data read from disk the first time).
> > 
> > The message itself isn't very useful though.  It should report what it
> > thinks is wrong with the bitmap (e.g. whether block/inode bitmaps are
> > unallocated, which/how many itable blocks are unallocated).
> 
> debugfs should help to find these details right ?

It isn't always possible to run debugfs on a customer system, and the
information would be lost after a reboot or an e2fsck.  The e2fsck might
even happen automatically after an errors=panic reboot and auto e2fsck.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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