Re: btrfsck: checksum verify failed

[Chris Mason <chris.mason@oracle.com>]

On Thu, Nov 12, 2009 at 06:43:00PM +0300, Alexander Beregalov wrote:
> 2009/11/12 Chris Mason <chris.mason@oracle.com>:
> > On Thu, Nov 12, 2009 at 05:16:34PM +0300, Alexander Beregalov wrote=
:
> >> 2009/11/12 Chris Mason <chris.mason@oracle.com>:
> >> > On Thu, Nov 12, 2009 at 05:08:53AM +0300, Alexander Beregalov wr=
ote:
> >> >> # for i in `seq 1 20`; do btrfsck /dev/sde|grep "checksum verif=
y
> >> >> failed";echo; done
> >> >> checksum verify failed on 31945617408 wanted 6607632D found 9CC=
3ED0
> >> >> checksum verify failed on 31945617408 wanted 6607632D found AFB=
BF41
> >> >
> >> > Was your filesystem mounted at the time? =A0It's strange that th=
e checksum
> >> > keeps changing, that points to the data in the block changing.
> >>
> >> It was not.
> >> Any tips how I can try to find a root cause?
> >> It is raid0 of two disks.
> >
> > Well, I'd start by looking for anything else that could be touching=
 the
> > FS or the devices. =A0You shouldn't see more than two different csu=
ms in this
> > configuration (one from each disk).
> I always see only these two blocks in output.

The wanted is always the same but the found is always different?

> >
> > Somehow the disk is giving us different answers each time, which po=
ints
> > to a problem in the storage stack.
> Hm, I will try to check discs by "badblocks" with few cycles of write=
-read.
> >
> > Otherwise it is possible that block 31945617408 is multiply linked =
and
> > is actually in use somehow else. =A0btrfsck is a readonly operation
> > though, it doesn't change the FS while it is running.
>=20
> Can it be a bug in the filesystem itself - in checksum calculation
> code, wrong pointer to data or something else?

We can check,  I'll make a program to map a logical block number to the
physical sector.

-chris

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