[Qemu-devel] [PATCH v7 for 2.1 3/4] block: add ability for block-stream to use node-name

[Jeff Cody <jcody@redhat.com>]

This adds the ability for block-stream to use node-name arguments
for base, to specify the backing image to stream from.

Both 'base' and 'base-node-name' are optional, but mutually exclusive.
Either can be specified, but not both together.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 blockdev.c           | 43 +++++++++++++++++++++++++++++++++++--------
 hmp.c                |  3 ++-
 qapi/block-core.json | 17 +++++++++++++----
 qmp-commands.hx      |  2 +-
 4 files changed, 51 insertions(+), 14 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index cb50c18..80bae9d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1868,13 +1868,15 @@ static void block_job_cb(void *opaque, int ret)
 
 void qmp_block_stream(const char *device,
                       bool has_base, const char *base,
+                      bool has_base_node_name, const char *base_node_name,
                       bool has_backing_file, const char *backing_file,
                       bool has_speed, int64_t speed,
                       bool has_on_error, BlockdevOnError on_error,
                       Error **errp)
 {
-    BlockDriverState *bs;
+    BlockDriverState *bs = NULL;
     BlockDriverState *base_bs = NULL;
+    BlockDriverState *tmp_bs;
     Error *local_err = NULL;
     const char *base_name = NULL;
 
@@ -1882,25 +1884,53 @@ void qmp_block_stream(const char *device,
         on_error = BLOCKDEV_ON_ERROR_REPORT;
     }
 
+    if (has_base && has_base_node_name) {
+        error_setg(errp, "'base' and 'base-node-name' are mutually exclusive");
+        return;
+    }
+
     bs = bdrv_find(device);
     if (!bs) {
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
         return;
     }
 
+    if (has_base_node_name) {
+        base_bs = bdrv_lookup_bs(NULL, base_node_name, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
+        }
+        tmp_bs = bdrv_find_overlay(bs, base_bs);
+        if (tmp_bs) {
+            base_name = tmp_bs->backing_file;
+        }
+    }
+
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_STREAM, errp)) {
         return;
     }
 
     if (has_base) {
         base_bs = bdrv_find_backing_image(bs, base);
-        if (base_bs == NULL) {
-            error_set(errp, QERR_BASE_NOT_FOUND, base);
-            return;
-        }
         base_name = base;
     }
 
+    if (base_bs == NULL && (has_base || has_base_node_name)) {
+        error_set(errp, QERR_BASE_NOT_FOUND, base);
+        return;
+    }
+
+    /* backing_file string overrides base bs filename */
+    base_name = has_backing_file ? backing_file : base_name;
+
+    /* Verify that 'base' is in the same chain as 'bs', if 'base' was
+     * specified */
+    if (base_bs && !bdrv_chain_contains(bs, base_bs)) {
+        error_setg(errp, "'device' and 'base' are not in the same chain");
+        return;
+    }
+
     /* 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) {
@@ -1909,9 +1939,6 @@ void qmp_block_stream(const char *device,
         return;
     }
 
-    /* backing_file string overrides base bs filename */
-    base_name = has_backing_file ? backing_file : base_name;
-
     stream_start(bs, base_bs, base_name, has_speed ? speed : 0,
                  on_error, block_job_cb, bs, &local_err);
     if (local_err) {
diff --git a/hmp.c b/hmp.c
index 0dc2499..fcbce6f 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1175,7 +1175,8 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
     const char *base = qdict_get_try_str(qdict, "base");
     int64_t speed = qdict_get_try_int(qdict, "speed", 0);
 
-    qmp_block_stream(device, base != NULL, base, false, NULL,
+    qmp_block_stream(device, base != NULL, base,
+                     false, NULL, false, NULL,
                      qdict_haskey(qdict, "speed"), speed,
                      true, BLOCKDEV_ON_ERROR_REPORT, &error);
 
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 9949add..a68ac45 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -964,9 +964,17 @@
 # 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.
+#
+# For 'base', either @base or @base-node-name may be set but not both. If
+# neither is specified, the entire chain will be streamed into the active image,
+# and the chain will consist of a single image (the current active layer) with
+# no backing file.
 #
-# @base:   #optional the common backing file name
+# @base:           #optional the common backing file name
+#
+# @base-node-name: #optional the block driver state node name of the
+#                            common backing file.  (Since 2.1)
 #
 # @backing-file: #optional The backing file string to write into the active
 #                          layer. This filename is not validated.
@@ -995,8 +1003,9 @@
 # Since: 1.1
 ##
 { 'command': 'block-stream',
-  'data': { 'device': 'str', '*base': 'str', '*backing-file': 'str',
-            '*speed': 'int', '*on-error': 'BlockdevOnError' } }
+  'data': { 'device': 'str', '*base': 'str', '*base-node-name': 'str',
+            '*backing-file': 'str', '*speed': 'int',
+            '*on-error': 'BlockdevOnError' } }
 
 ##
 # @block-job-set-speed:
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 3db8167..bf82603 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -979,7 +979,7 @@ EQMP
 
     {
         .name       = "block-stream",
-        .args_type  = "device:B,base:s?,speed:o?,backing-file:s?,on-error:s?",
+        .args_type  = "device:B,base:s?,base-node-name:s?,speed:o?,backing-file:s?,on-error:s?",
         .mhandler.cmd_new = qmp_marshal_input_block_stream,
     },
 
-- 
1.9.3