[Libguestfs] [PATCH v2v 1/2] input: libvirt: Share a single connection to the source NBD server

When using virt-p2v from RHEL 7, it starts a very old qemu-nbd server (probably 1.5.3) which required the --shared parameter to enable sharing even in read-only mode. Since it doesn't pass this parameter only a single connection at a time is allowed, and further connections will deadlock. Note that later versions of qemu-nbd changed this so that read-only connections permit sharing. In modular virt-v2v we now use nbdkit-nbd-plugin to proxy the connection to virt-p2v / qemu-nbd. When you connect to this multiple times, as virt-v2v does, it will make multiple connections to the backend qemu-nbd. This will cause a deadlock. We can use the nbdkit-nbd-plugin shared=true flag to enable the plugin to share a single connection to the backend between multiple nbdkit clients. --- input/input_libvirt.ml | 1 + 1 file changed, 1 insertion(+) diff --git a/input/input_libvirt.ml b/input/input_libvirt.ml index 33f61086ec..42050c157b 100644 --- a/input/input_libvirt.ml +++ b/input/input_libvirt.ml @@ -76,6 +76,7 @@ and libvirt_servers dir disks = Nbdkit.add_filter cmd "cow"; Nbdkit.add_arg cmd "hostname" hostname; Nbdkit.add_arg cmd "port" (string_of_int port); + Nbdkit.add_arg cmd "shared" "true"; let _, pid = Nbdkit.run_unix ~socket cmd in (* --exit-with-parent should ensure nbdkit is cleaned -- 2.32.0