Re: [Xen-users] Re: [Xen-devel] tap:qcow causes dom-U to hang in 3.0.3

[Roland Paterson-Jones <roland@xxxxxxxxxxxx>]

Julian Chesterfield wrote:

> Can you also verify whether there's an active tapdisk process running 
> in Dom0 for each tap:{aio,qcow} vbd. We are aware of a bug with the 
> qcow implementation that we hope to submit a fix for very soon. It's 
> likely that you are seeing the same issue.
Sorry, this is not what you asked for, but this is what an 'ls' of the  
qcow file shows:
[root@dom0-0-50-45-5d-6a-bc ~]# ls -als /mnt/instance_image_store_0/
total 1564108
     4 drwxr-xr-x  2 root root          4096 Nov 10 15:42 .
     8 drwxr-xr-x  8 root root          4096 Nov  7 17:56 ..
1563132 -rw-r--r--  1 root root    1599078400 Nov 10 15:42 2
   964 -rw-r--r--  1 root root 1099645846016 Nov 10 15:50 2.qcow

It looks like the qcow file has grown to > 1000GB in (apparent) size(!) 
Could this be the root of the problem?
At this stage the dom-U is still running, but the qcow file is clearly 
not right. The file called '2' is a loopback image backing the qcow file.
The qcow overlay was created using '/usr/sbin/qcow-create $((10*1024)) 
/mnt/instance_image_store_0/2.qcow /mnt/instance_image_store_0/2'. I'm 
guessing there's no danger in making the qcow overlay extent (10GB) 
larger than the underlying loopback file extend (1.5GB) but please 
correct me if I'm wrong.
Earlier, an ls of the same directory (soon after dom-U creation) looked 
like:
[root@dom0-0-50-45-5d-6a-bc ~]# ls -als /mnt/instance_image_store_0/
total 1564052
     4 drwxr-xr-x  2 root root       4096 Nov 10 15:42 .
     8 drwxr-xr-x  8 root root       4096 Nov  7 17:56 ..
1563132 -rw-r--r--  1 root root 1599078400 Nov 10 15:42 2
   908 -rw-r--r--  1 root root     925696 Nov 10 15:43 2.qcow

Could this be the root of the problem - i.e. something in the qcow 
driver is getting it's offsets in the qcow file mangled?
Can I try to compile the qcow (tapdisk) driver with debug enabled? Where 
would the output go?
Regards
Roland


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