linux-ext4 - Re: ext4 error when testing virtio-scsi & vhost-scsi

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Date:	Tue, 12 Jul 2016 12:43:24 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Zhangfei Gao <zhangfei.gao@...il.com>
Cc:	kvm@...r.kernel.org, qemu-devel@...gnu.org,
	target-devel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: ext4 error when testing virtio-scsi & vhost-scsi

On Tue, Jul 12, 2016 at 03:14:38PM +0800, Zhangfei Gao wrote:
> Some update:
> 
> If test with ext2, no problem in iblock.
> If test with ext4, ext4_mb_generate_buddy reported error in the
> removing files after reboot.
> 
> 
> root@(none)$ rm test
> [   21.006549] EXT4-fs error (device sda): ext4_mb_generate_buddy:758: group 18
> , block bitmap and bg descriptor inconsistent: 26464 vs 25600 free clusters
> [   21.008249] JBD2: Spotted dirty metadata buffer (dev = sda, blocknr = 0). Th
> ere's a risk of filesystem corruption in case of system crash.
> 
> Any special notes of using ext4 in qemu?

Ext4 has more runtime consistency checking than ext2.  So just because
ext4 complains doesn't mean that there isn't a problem with the file
system; it just means that ext4 is more likely to notice before you
lose user data.

So if you test with ext2, try running e2fsck afterwards, to make sure
the file system is consistent.

Given that I'm reguarly testing ext4 using kvm, and I haven't seen
anything like this in a very long time, I suspect the problemb is with
your SCSI code, and not with ext4.

				- Ted
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