qmp: add block_stream command

Add the block_stream command, which starts copy backing file contents
into the image file.  Also add the BLOCK_JOB_COMPLETED QMP event which
is emitted when image streaming completes.  Later patches add control
over the background copy speed, cancelation, and querying running
streaming operations.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Acked-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/trace-events b/trace-events
index f6a3cd1..5edba21 100644
--- a/trace-events
+++ b/trace-events
@@ -74,6 +74,10 @@
 stream_one_iteration(void *s, int64_t sector_num, int nb_sectors, int is_allocated) "s %p sector_num %"PRId64" nb_sectors %d is_allocated %d"
 stream_start(void *bs, void *base, void *s, void *co, void *opaque) "bs %p base %p s %p co %p opaque %p"
 
+# blockdev.c
+block_stream_cb(void *bs, void *job, int ret) "bs %p job %p ret %d"
+qmp_block_stream(void *bs, void *job) "bs %p job %p"
+
 # hw/virtio-blk.c
 virtio_blk_req_complete(void *req, int status) "req %p status %d"
 virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"