Re: [Bacula-users] iSCSI-Tape problems

[Josh F. <jf...@pv...>]

Christoph Litauer wrote:
> Dear bacula users,
>
> I am running bacula-mysql 2.2.5 (rpm from sourceforge) on a SuSE SLES
> 10SP1 machine, kernel version 2.6.16 (SMP).
>
> I configured and mounted tape drive via iSCSI. I can tar from and to
> this drive without problems. I can label a tape with btape, read this
> label without problems. But immediatly after writing a few blocks using
> qfill or wr the machine stops working. One of my write attempts left a
> kernel panic message in /var/log/messages:
>
> Oct 24 13:28:26 bacula kernel: Bad page state in process 'btape'
> Oct 24 13:28:26 bacula kernel: page:c16cce40 flags:0x80000000
> mapping:00000000 mapcount:0 count:1
> Oct 24 13:28:26 bacula kernel: Trying to fix it up, but a reboot is needed
> Oct 24 13:28:26 bacula kernel: Backtrace:
> Oct 24 13:28:26 bacula kernel:  [<c0149955>] bad_page+0x42/0x68
> Oct 24 13:28:26 bacula kernel:  [<c0149dbd>] __free_pages_ok+0x55/0xe4
> Oct 24 13:28:26 bacula kernel:  [<f906e0bb>] normalize_buffer+0x31/0x63 [st]
> Oct 24 13:28:26 bacula kernel:  [<f9070492>] st_release+0x1e/0x45 [st]
> Oct 24 13:28:26 bacula kernel:  [<c01613d5>] __fput+0xa1/0x167
> Oct 24 13:28:26 bacula kernel:  [<c015ed5d>] filp_close+0x4e/0x54
> Oct 24 13:28:26 bacula kernel:  [<c0103bdb>] sysenter_past_esp+0x54/0x79
> Oct 24 13:28:26 bacula kernel: Bad page state in process 'btape'
> Oct 24 13:28:26 bacula kernel: page:c16cce60 flags:0x80000080
> mapping:00000000 mapcount:0 count:1
> Oct 24 13:28:26 bacula kernel: Trying to fix it up, but a reboot is needed
> Oct 24 13:28:26 bacula kernel: Backtrace:
> Oct 24 13:28:26 bacula kernel:  [<c0149955>] bad_page+0x42/0x68
> Oct 24 13:28:26 bacula kernel:  [<c0149dbd>] __free_pages_ok+0x55/0xe4
> Oct 24 13:28:26 bacula kernel:  [<f906e0bb>] normalize_buffer+0x31/0x63 [st]
> Oct 24 13:28:26 bacula kernel:  [<f9070492>] st_release+0x1e/0x45 [st]
> Oct 24 13:28:26 bacula kernel:  [<c01613d5>] __fput+0xa1/0x167
> Oct 24 13:28:26 bacula kernel:  [<c015ed5d>] filp_close+0x4e/0x54
> Oct 24 13:28:26 bacula kernel:  [<c0103bdb>] sysenter_past_esp+0x54/0x79
>
> So this seems to be a kernel bug. Googling lead me to
> http://www.mail-archive.com/bac...@li.../msg17890.html
> but this didn't help too much ...
>   

This can happen when ClearPageReserved() is not called for a reserved
kernel memory page. Could be an iSCSI driver (included with the  Linux
kernel) problem or, if you are using a hardware iSCSI adapter, it could
be a problem with its driver.

> My question is: What is the difference between the tape write actions of
> tar and btape? Maybe I will be able to configure the tape device so that
> btape doesn't run in kernel panics any more?
>   

Well, btape is very likely using a different block size than you used
with tar. The default block size for btape is 126x512 = 64,512 bytes.
The default for tar is 20x512 = 10,240 bytes. Try setting 'Maximum block
size = 10240' and 'Minimum block size = 10240' in the bacula-sd.conf
config file being used by btape. If that works, then try tar with '-b
64512' and see if tar causes the same problem with large block sizes. If
neither wroks with the larger block size, then you will have to use the
smaller block size until the iSCSI bug is fixed.