[Qemu-block] [RFC PATCH 6/7] block: Accept node-name for block-stream

[Kevin Wolf]

In order to remove the necessity to use BlockBackend names in the
external API, we want to allow node-names everywhere. This is an example
conversion that accepts a node-name without lifting the restriction that
we're operating at a root node. Changing QMP commands so that they can
work in the middle of the graph is a completely orthogonal thing.

Signed-off-by: Kevin Wolf <address@hidden>
---
 blockdev.c           | 32 ++++++++++++++++++++------------
 qapi/block-core.json |  2 +-
 qmp-commands.hx      |  2 +-
 3 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 24c4d0a..bd93190 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1196,6 +1196,23 @@ static BlockBackend *qmp_get_blk(const char *blk_name, 
const char *qdev_id,
     return blk;
 }
 
+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_has_blk(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");
@@ -3041,7 +3058,6 @@ void qmp_block_stream(const char *device,
                       bool has_on_error, BlockdevOnError on_error,
                       Error **errp)
 {
-    BlockBackend *blk;
     BlockDriverState *bs;
     BlockDriverState *base_bs = NULL;
     AioContext *aio_context;
@@ -3052,22 +3068,14 @@ 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 = 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/qapi/block-core.json b/qapi/block-core.json
index 15669b3..60fa70a 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1413,7 +1413,7 @@
 # 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 name or node-name of a root node
 #
 # @base:   #optional the common backing file name
 #
diff --git a/qmp-commands.hx b/qmp-commands.hx
index ae0105f..d4c7c93 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1118,7 +1118,7 @@ Copy data from a backing file into a block device.
 
 Arguments:
 
-- "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
-- 
1.8.3.1