[Qemu-devel] [PATCH] block/stream: Don't stream unbacked devices

[Max Reitz <mreitz@redhat.com>]

If a block device is unbacked, a streaming blockjob should immediately
finish instead of beginning to try to stream, then noticing the backing
file does not contain even the first sector (since it does not exist)
and then finishing normally.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/stream.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/stream.c b/block/stream.c
index 694fd42..46bec7d 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -88,6 +88,11 @@ static void coroutine_fn stream_run(void *opaque)
     int n = 0;
     void *buf;
 
+    if (!bs->backing_hd) {
+        block_job_completed(&s->common, 0);
+        return;
+    }
+
     s->common.len = bdrv_getlength(bs);
     if (s->common.len < 0) {
         block_job_completed(&s->common, s->common.len);
-- 
1.8.4.2