From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
Subject: Re: LVM Checksum error when using persistent grants
 (#linux-next + stable/for-jens-3.8)
Date: Fri, 7 Dec 2012 11:08:00 +0100
Message-ID: <50C1C000.5020803@citrix.com>
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	<20121206031455.GA4408@phenom.dumpdata.com>
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To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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On 06/12/12 04:14, Konrad Rzeszutek Wilk wrote:
> Hey Roger,
> 
> I am seeing this weird behavior when using #linux-next + stable/for-jens-3.8 tree.
> 
> Basically I can do 'pvscan' on xvd* disk and quite often I get checksum errors:
> 
> # pvscan /dev/xvdf
>   PV /dev/xvdf2   VG VolGroup00        lvm2 [18.88 GiB / 0    free]
>   PV /dev/dm-14   VG vg_x86_64-pvhvm   lvm2 [4.00 GiB / 68.00 MiB free]
>   PV /dev/dm-12   VG vg_i386-pvhvm     lvm2 [4.00 GiB / 68.00 MiB free]
>   PV /dev/dm-11   VG vg_i386           lvm2 [4.00 GiB / 68.00 MiB free]
>   PV /dev/sda     VG guests            lvm2 [931.51 GiB / 220.51 GiB free]
>   Total: 5 [962.38 GiB] / in use: 5 [962.38 GiB] / in no VG: 0 [0   ]
> # pvscan /dev/xvdf
>   /dev/xvdf2: Checksum error
>   Couldn't read volume group metadata.
>   /dev/xvdf2: Checksum error
>   Couldn't read volume group metadata.
>   PV /dev/dm-14   VG vg_x86_64-pvhvm   lvm2 [4.00 GiB / 68.00 MiB free]
>   PV /dev/dm-12   VG vg_i386-pvhvm     lvm2 [4.00 GiB / 68.00 MiB free]
>   PV /dev/dm-11   VG vg_i386           lvm2 [4.00 GiB / 68.00 MiB free]
>   PV /dev/sda     VG guests            lvm2 [931.51 GiB / 220.51 GiB free]
>   Total: 4 [943.50 GiB] / in use: 4 [943.50 GiB] / in no VG: 0 [0   ]
> 
> This is with a i386 dom0, 64-bit Xen 4.1.3 hypervisor, and with either
> 64-bit or 32-bit PV or PVHVM guest.
> 
> Have you seen something like this?
> 
> Note, the other LV disks are over iSCSI and are working fine.

Thanks for the report Konrad, I'm able to reproduce this:

root@debian:~# pvscan -d -v /dev/xvdb2
    Wiping cache of LVM-capable devices
    Wiping internal VG cache
    Walking through all physical volumes
  PV /dev/xvdb2                      lvm2 [4.99 GiB]
  Total: 1 [4.99 GiB] / in use: 0 [0   ] / in no VG: 1 [4.99 GiB]
root@debian:~# pvscan -d -v /dev/xvdb2
    Wiping cache of LVM-capable devices
    Wiping internal VG cache
    Walking through all physical volumes
  No matching physical volumes found

What I find strange is that this only happens when using partitions as
LVM PVs, if I use the full disk (/dev/xvdb) as a PV I'm not able to
reproduce it. I will investigate further.