[libvirt] Re: [Qemu-devel] live snapshot wiki updated
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