On 11/29/2009 12:45 AM, Chris Webb wrote:
MORITA Kazutaka <[email protected]> writes:
Even read-only access is not allowed while another qemu is doing
write access. However, there is no problem about your patch, I guess.
It is because Sheepdog allow us to clone images only from
snapshot images. It means a backing image is always read-only.
If users specify writable Sheepdog VDI as a backing image,
qemu-img returns error.
What about the case of (for example) a qcow2 file backed by a Sheepdog
image? Is that also restricted to be a snapshot image (and therefore safe)
or is there a potential problem there?
Yes, in this case, a backing Sheepdog image is restricted to a snapshot
image, too.
However, taking other formats into account, bdrv_claim may be required
even when opening as read-only. It is because qcow2 cannot prevent other
VMs write data to an opened backing image.
If so, bdrv_claim need more arguments such as open flags
to notify the opened image is read-only or not, right?
Regards,
MORITA Kazutaka
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