writes got stuck

writes got stuck

[Cheng Shao]

Hi there,

I'm periodically having issues with btrfs running in a Ubuntu VM using
VirtualBox. After the VM has been running for a while (a couple days),
any write operation seems getting stuck. The read seems totally fine.
I tried a simple dd of a 4M file and it got stuck after writing 131K
worth of data.

I don't know if this is btrfs related, or it is due to some bug in
VritualBox. Could you guys provide information on how to debug this
(collecting logs, getting dumps etc.)? Thanks a lot!

thanks,
- cheng

Re: writes got stuck

[Chris Mason]

Excerpts from Cheng Shao's message of 2011-04-18 17:49:29 -0400:
> Hi there,
> 
> I'm periodically having issues with btrfs running in a Ubuntu VM using
> VirtualBox. After the VM has been running for a while (a couple days),
> any write operation seems getting stuck. The read seems totally fine.
> I tried a simple dd of a 4M file and it got stuck after writing 131K
> worth of data.
> 
> I don't know if this is btrfs related, or it is due to some bug in
> VritualBox. Could you guys provide information on how to debug this
> (collecting logs, getting dumps etc.)? Thanks a lot!

Which kernel are you running?

Definitely look for kernel messages (run dmesg etc).  If there are no
crashes or related messages you can run sysrq-t and send the output and
we can look for the deadlock.

-chris

Re: writes got stuck

[Chris Murphy]

On Tue, 19 Apr 2011 05:08:05 -0700 Chris Mason wrote:

>  
> Excerpts from Cheng Shao's message of 2011-04-18 17:49:29 -0400:
> > Hi there,
> > 
> > I'm periodically having issues with btrfs running in a Ubuntu VM using
> > VirtualBox. After the VM has been running for a while (a couple days),
> > any write operation seems getting stuck. The read seems totally fine.
> > I tried a simple dd of a 4M file and it got stuck after writing 131K
> > worth of data.
> > 
> > I don't know if this is btrfs related, or it is due to some bug in
> > VritualBox. Could you guys provide information on how to debug this
> > (collecting logs, getting dumps etc.)? Thanks a lot!
> 
> Which kernel are you running?
> 

Not reproducible with Linux 2.6.38.2-9.fc15.x86_64, Fedora 15 beta2, VirtualBox 4.06 on a Mac OS X host. 

Unrelated to btrfs but related to VirtualBox write hang, I did experience numerous hangs during installation of F15, which were apparently* resolved with kernel parameter clocksource=jiffies which is not related to btrfs, and was not previously required for F14 with earlier versions of VirtualBox.


Chris Murphy


* I say apparently with a sample of 8 failures without the option and 1 success with the option.