The 20/07/11, Daniel P. Berrange wrote:
To make the decision whether the filename from QEMU is valid, we have to parse the master image header data to see if the filename actually matches the backing file required by the image assigned to the guest.
Actually, libvirt should not have to worry if the filename provided by QEMU is valid. I think it should trust QEMU. If QEMU doesn't provide information others can trust; it should be fixed at QEMU side.
We're not fighting over the internals of metadata. We just need to know ahead of launching QEMU, what backing files an image has & what format they are in. We do that by reading at the metadata headers of the disk images. We never attempt to write to the disk images. Either someone provides a library todo that, or we write the probing code for each file format in libvirt. Currently we have the latter.
This is what I would call "fighting with QEMU internals". How do you prevent from concurrency access and modifications? Ideally speacking libvirt should be able to co-exist with foreign implementations, all requesting QEMU. -- Nicolas Sebrecht