libvirt users - Aug 2012 - virsh command vol-upload purpose question

I use virsh vol-upload to upload some data in a volume and use 
vol-download to download these data from the same volume, both these two 
commands work well. However, when I first use these two commands, I 
thought I can use vol-upload to upload some file, then attach this 
volume to a vm, and  access the upload file in this vm. I did this 
experiment, bud it not success. Once I upload a file into a volume, 
attach it to a vm, then the vm can not recognize the file type of this 
vm, if I mkfs to the volume, the file I upload disappear.

So, my question is the purpose of the vol-upload is just to save some 
data in the volume outside vm? And at this point do we have method to 
access the data upload to the volume from vm?

Thanks

Bests
Kimi Li