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In my testing, I was able to provoke an odd block pull failure: $ virsh blockpull dom vda --bandwidth 10000 error: Requested operation is not valid: No active operation on device: drive-virtio-disk0 merely by using gdb to artifically wait to do the block job set speed until after the pull had already finished. But in reality, that should be a success, since the pull finished before we had a chance to set speed. Furthermore, using a double job lock is not only annoying, but a bug in itself - if you do parallel virDomainBlockRebase, and hit the race window just right, the first call grabs the VM job to start a fast block job, then the second call grabs the VM job to start a long-running job with unspecified speed, then the first call finally regrabs the VM job and sets the speed, which ends up running the second job under the speed from the first call. By consolidating things into a single job, we avoid opening that race, as well as reduce the time between starting the job and changing the speed, for less likelihood of the speed change happening after block job completion in the first place. * src/qemu/qemu_monitor.h (BLOCK_JOB_CMD): Add new mode. * src/qemu/qemu_driver.c (qemuDomainBlockRebase): Move secondary job call... (qemuDomainBlockJobImpl): ...here, for fewer locks. * src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockJob): Change return value on new internal mode.
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>