mirror: Block the source BlockDriverState in mirror_start_job()

The mirror_start_job() function used for the commit-active job blocks
the source, target and all intermediate nodes for the duration of the
job.

   target <- intermediate <- source

Since 4ef85a9c2339 this function creates a dummy mirror_top_bs that
goes on top of the source node, and it is this dummy node that gets
blocked instead. The source node is never blocked or added to the
job's list of nodes.

   target <- intermediate <- source <- mirror_top

At the moment I don't think it is possible to exploit this problem
because any additional job on 'source' would either be forbidden for
other reasons or it would need to involve an additional node that is
blocked, causing an error.

This can be seen in the error messages, however, because they never
refer to the source node being blocked:

  $ qemu-img create -f qcow2 hd0.qcow2 1M
  $ qemu-img create -f qcow2 -b hd0.qcow2 hd1.qcow2
  $ qemu-io -c 'write 0 1M' hd0.qcow2
  $ $QEMU -drive if=none,file=hd1.qcow2,node-name=hd1
  { "execute": "qmp_capabilities" }
  { "execute": "block-commit", "arguments": {"device": "hd1", "speed": 256}}
  { "execute": "block-stream", "arguments": {"device": "hd1"}}
  { "error": {"class": "GenericError",
    "desc": "Node 'hd0' is busy: block device is in use by block job: commit"}}

After this patch the error message refers to 'hd1', as it should.

The expected output of iotest 141 also needs to be updated for the
same reason.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out
index f252c86875..41c7291258 100644
--- a/tests/qemu-iotests/141.out
+++ b/tests/qemu-iotests/141.out
@@ -28,7 +28,7 @@ Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "mirror"}}
 {"return": {}}
-{"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: node is used as backing hd of 'NODE_NAME'"}}
+{"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: block device is in use by block job: mirror"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "job0"}}
@@ -45,7 +45,7 @@ Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}
 {"return": {}}
-{"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: node is used as backing hd of 'NODE_NAME'"}}
+{"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: block device is in use by block job: commit"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "job0"}}