[Qemu-block] [PATCH v9 07/11] block: Add QMP support for streaming to an intermediate layer

[Alberto Garcia]

This patch makes the 'device' parameter of the 'block-stream' command
accept a node name as well as a device name.

In addition to that, operation blockers will be checked in all
intermediate nodes between the top and the base node.

Since qmp_block_stream() now uses the error from bdrv_lookup_bs() and
no longer returns DeviceNotFound, iotest 030 is updated to expect
GenericError instead.

Signed-off-by: Alberto Garcia <address@hidden>
---
 blockdev.c             | 31 +++++++++++++++++++++++--------
 qapi/block-core.json   | 10 +++++++---
 tests/qemu-iotests/030 |  2 +-
 3 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 2e7712e..bfdc0e3 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2989,6 +2989,7 @@ void qmp_block_stream(const char *device,
     BlockBackend *blk;
     BlockDriverState *bs;
     BlockDriverState *base_bs = NULL;
+    BlockDriverState *active;
     AioContext *aio_context;
     Error *local_err = NULL;
     const char *base_name = NULL;
@@ -2997,21 +2998,19 @@ void qmp_block_stream(const char *device,
         on_error = BLOCKDEV_ON_ERROR_REPORT;
     }
 
-    blk = blk_by_name(device);
-    if (!blk) {
-        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
-                  "Device '%s' not found", device);
+    bs = bdrv_lookup_bs(device, device, errp);
+    if (!bs) {
         return;
     }
 
-    aio_context = blk_get_aio_context(blk);
+    aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    if (!blk_is_available(blk)) {
+    blk = blk_by_name(device);
+    if (blk && !blk_is_available(blk)) {
         error_setg(errp, "Device '%s' has no medium", device);
         goto out;
     }
-    bs = blk_bs(blk);
 
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_STREAM, errp)) {
         goto out;
@@ -3027,6 +3026,22 @@ void qmp_block_stream(const char *device,
         base_name = base;
     }
 
+    /* Look for the top-level node that contains 'bs' in its chain */
+    active = NULL;
+    do {
+        active = bdrv_next(active);
+    } while (active && !bdrv_chain_contains(active, bs));
+
+    if (active == NULL) {
+        error_setg(errp, "Cannot find top level node for '%s'", device);
+        goto out;
+    }
+
+    /* Check for op blockers in the top-level node too */
+    if (bdrv_op_is_blocked(active, BLOCK_OP_TYPE_STREAM, errp)) {
+        goto out;
+    }
+
     /* if we are streaming the entire chain, the result will have no backing
      * file, and specifying one is therefore an error */
     if (base_bs == NULL && has_backing_file) {
@@ -3038,7 +3053,7 @@ void qmp_block_stream(const char *device,
     /* backing_file string overrides base bs filename */
     base_name = has_backing_file ? backing_file : base_name;
 
-    stream_start(bs, NULL, base_bs, base_name, has_speed ? speed : 0,
+    stream_start(bs, active, base_bs, base_name, has_speed ? speed : 0,
                  on_error, block_job_cb, bs, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 59107ed..e20193a 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1405,6 +1405,10 @@
 # with query-block-jobs.  The operation can be stopped before it has completed
 # using the block-job-cancel command.
 #
+# The node that receives the data is called the top image, can be located
+# in any part of the whole chain and can be specified using its device
+# or node name.
+#
 # If a base file is specified then sectors are not copied from that base file 
and
 # its backing chain.  When streaming completes the image file will have the 
base
 # file as its backing file.  This can be used to stream a subset of the backing
@@ -1413,12 +1417,12 @@
 # On successful completion the image file is updated to drop the backing file
 # and the BLOCK_JOB_COMPLETED event is emitted.
 #
-# @device: the device name
+# @device: the device or node name of the top image
 #
 # @base:   #optional the common backing file name
 #
-# @backing-file: #optional The backing file string to write into the active
-#                          layer. This filename is not validated.
+# @backing-file: #optional The backing file string to write into the top
+#                          image. This filename is not validated.
 #
 #                          If a pathname string is such that it cannot be
 #                          resolved by QEMU, that means that subsequent QMP or
diff --git a/tests/qemu-iotests/030 b/tests/qemu-iotests/030
index 3ac2443..107049b 100755
--- a/tests/qemu-iotests/030
+++ b/tests/qemu-iotests/030
@@ -126,7 +126,7 @@ class TestSingleDrive(iotests.QMPTestCase):
 
     def test_device_not_found(self):
         result = self.vm.qmp('block-stream', device='nonexistent')
-        self.assert_qmp(result, 'error/class', 'DeviceNotFound')
+        self.assert_qmp(result, 'error/class', 'GenericError')
 
 
 class TestSmallerBackingFile(iotests.QMPTestCase):
-- 
2.8.0.rc3