[Qemu-devel] [PATCH v4 01/11] block: Accept node-name for block-stream

[Kevin Wolf <kwolf@redhat.com>]

In order to remove the necessity to use BlockBackend names in the
external API, we want to allow node-names everywhere. This converts
block-stream to accept a node-name without lifting the restriction that
we're operating at a root node.

In case of an invalid device name, the command returns the GenericError
error class now instead of DeviceNotFound, because this is what
qmp_get_root_bs() returns.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/block-backend.c          | 16 ++++++++++++++++
 blockdev.c                     | 32 ++++++++++++++++++++------------
 include/sysemu/block-backend.h |  1 +
 qapi/block-core.json           |  5 +----
 qmp-commands.hx                |  2 +-
 tests/qemu-iotests/030         |  2 +-
 6 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index f9cea1b..4a00f8a 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -410,6 +410,22 @@ bool bdrv_has_blk(BlockDriverState *bs)
 }
 
 /*
+ * Returns true if @bs has only BlockBackends as parents.
+ */
+bool bdrv_is_root_node(BlockDriverState *bs)
+{
+    BdrvChild *c;
+
+    QLIST_FOREACH(c, &bs->parents, next_parent) {
+        if (c->role != &child_root) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/*
  * Return @blk's DriveInfo if any, else null.
  */
 DriveInfo *blk_legacy_dinfo(BlockBackend *blk)
diff --git a/blockdev.c b/blockdev.c
index 384ad3b..739906e 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1174,6 +1174,23 @@ fail:
     return dinfo;
 }
 
+static BlockDriverState *qmp_get_root_bs(const char *name, Error **errp)
+{
+    BlockDriverState *bs;
+
+    bs = bdrv_lookup_bs(name, name, errp);
+    if (bs == NULL) {
+        return NULL;
+    }
+
+    if (!bdrv_is_root_node(bs)) {
+        error_setg(errp, "Need a root block node");
+        return NULL;
+    }
+
+    return bs;
+}
+
 void hmp_commit(Monitor *mon, const QDict *qdict)
 {
     const char *device = qdict_get_str(qdict, "device");
@@ -3014,7 +3031,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
                       bool has_on_error, BlockdevOnError on_error,
                       Error **errp)
 {
-    BlockBackend *blk;
     BlockDriverState *bs;
     BlockDriverState *base_bs = NULL;
     AioContext *aio_context;
@@ -3025,22 +3041,14 @@ void qmp_block_stream(bool has_job_id, const char *job_id, 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 = qmp_get_root_bs(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)) {
-        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;
     }
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 3c3e82f..e1c89d8 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -98,6 +98,7 @@ BlockDriverState *blk_bs(BlockBackend *blk);
 void blk_remove_bs(BlockBackend *blk);
 void blk_insert_bs(BlockBackend *blk, BlockDriverState *bs);
 bool bdrv_has_blk(BlockDriverState *bs);
+bool bdrv_is_root_node(BlockDriverState *bs);
 
 void blk_set_allow_write_beyond_eof(BlockBackend *blk, bool allow);
 void blk_iostatus_enable(BlockBackend *blk);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 3444a9b..d9958d5 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1434,7 +1434,7 @@
 # @job-id: #optional identifier for the newly-created block job. If
 #          omitted, the device name will be used. (Since 2.7)
 #
-# @device: the device name
+# @device: the device name or node-name of a root node
 #
 # @base:   #optional the common backing file name
 #
@@ -1459,9 +1459,6 @@
 #            'stop' and 'enospc' can only be used if the block device
 #            supports io-status (see BlockInfo).  Since 1.3.
 #
-# Returns: Nothing on success
-#          If @device does not exist, DeviceNotFound
-#
 # Since: 1.1
 ##
 { 'command': 'block-stream',
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c46c65c..68fb925 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1120,7 +1120,7 @@ Arguments:
 
 - "job-id": Identifier for the newly-created block job. If omitted,
             the device name will be used. (json-string, optional)
-- "device": The device's ID, must be unique (json-string)
+- "device": The device name or node-name of a root node (json-string)
 - "base": The file name of the backing image above which copying starts
           (json-string, optional)
 - "backing-file": The backing file string to write into the active layer. This
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):
-- 
1.8.3.1