[Qemu-devel] [PATCH 4/5] block: Accept node-name arguments for block-commit

[Jeff Cody]

This modifies the block operation block-commit so that it will
accept node-name arguments for either 'top' or 'base' BDS.

The filename and node-name are mutually exclusive to each other;
i.e.:
    "top" and "top-node-name" are mutually exclusive (enforced)
    "base" and "base-node-name" are mutually exclusive (enforced)

The preferred and recommended method now of using block-commit
is to specify the BDS to operate on via their node-name arguments.

This also adds an explicit check that base_bs is in the chain of
top_bs, because if they are referenced by their unique node-name
arguments, the discovery process does not intrinsically verify
they are in the same chain.

Signed-off-by: Jeff Cody <address@hidden>
---
 blockdev.c       | 35 +++++++++++++++++++++++++++++++++--
 qapi-schema.json | 35 ++++++++++++++++++++++++++---------
 qmp-commands.hx  | 29 ++++++++++++++++++++++-------
 3 files changed, 81 insertions(+), 18 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 02c6525..d8cb396 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1869,7 +1869,9 @@ void qmp_block_stream(const char *device, bool has_base,
 
 void qmp_block_commit(const char *device,
                       bool has_base, const char *base,
+                      bool has_base_node_name, const char *base_node_name,
                       bool has_top, const char *top,
+                      bool has_top_node_name, const char *top_node_name,
                       bool has_speed, int64_t speed,
                       Error **errp)
 {
@@ -1888,6 +1890,15 @@ void qmp_block_commit(const char *device,
     /* drain all i/o before commits */
     bdrv_drain_all();
 
+    if (has_base && has_base_node_name) {
+        error_setg(errp, "'base' and 'base-node-name' are mutually exclusive");
+        return;
+    }
+    if (has_top && has_top_node_name) {
+        error_setg(errp, "'top' and 'top-node-name' are mutually exclusive");
+        return;
+    }
+
     bs = bdrv_find(device);
     if (!bs) {
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
@@ -1897,7 +1908,14 @@ void qmp_block_commit(const char *device,
     /* default top_bs is the active layer */
     top_bs = bs;
 
-    if (top) {
+    /* Find the 'top' image file for the commit */
+    if (has_top_node_name) {
+        top_bs = bdrv_lookup_bs(NULL, top_node_name, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
+        }
+    } else if (has_top && top) {
         if (strcmp(bs->filename, top) != 0) {
             top_bs = bdrv_find_backing_image(bs, top);
         }
@@ -1908,7 +1926,14 @@ void qmp_block_commit(const char *device,
         return;
     }
 
-    if (has_base && base) {
+    /* Find the 'base' image file for the commit */
+    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;
+        }
+    } else if (has_base && base) {
         base_bs = bdrv_find_backing_image(top_bs, base);
     } else {
         base_bs = bdrv_find_base(top_bs);
@@ -1919,6 +1944,12 @@ void qmp_block_commit(const char *device,
         return;
     }
 
+    /* Verify that 'base' is in the same chain as 'top' */
+    if (!bdrv_is_in_chain(top_bs, base_bs)) {
+        error_setg(errp, "'base' and 'top' are not in the same chain");
+        return;
+    }
+
     if (top_bs == bs) {
         commit_active_start(bs, base_bs, speed, on_error, block_job_cb,
                             bs, &local_err);
diff --git a/qapi-schema.json b/qapi-schema.json
index 06a9b5d..eddb2b8 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2096,12 +2096,27 @@
 #
 # @device:  the name of the device
 #
-# @base:   #optional The file name of the backing image to write data into.
-#                    If not specified, this is the deepest backing image
+# For 'base', either @base or @base-node-name may be set but not both. If
+# neither is specified, this is the deepest backing image
 #
-# @top:    #optional The file name of the backing image within the image chain,
-#                    which contains the topmost data to be committed down. If
-#                    not specified, this is the active layer.
+# @base:          #optional The file name of the backing image to write data
+#                           into.
+#
+# @base-node-name #optional The name of the block driver state node of the
+#                           backing image to write data into.
+#                           (Since 2.1)
+#
+# For 'top', either @top or @top-node-name must be set but not both.
+#
+# @top:           #optional The file name of the backing image within the image
+#                           chain, which contains the topmost data to be
+#                           committed down. If not specified, this is the
+#                           active layer.
+#
+# @top-node-name: #optional The block driver state node name of the backing
+#                           image within the image chain, which contains the
+#                           topmost data to be committed down.
+#                           (Since 2.1)
 #
 #                    If top == base, that is an error.
 #                    If top == active, the job will not be completed by itself,
@@ -2120,17 +2135,19 @@
 #
 # Returns: Nothing on success
 #          If commit or stream is already active on this device, DeviceInUse
-#          If @device does not exist, DeviceNotFound
+#          If @device does not exist or cannot be determined, DeviceNotFound
 #          If image commit is not supported by this device, NotSupported
-#          If @base or @top is invalid, a generic error is returned
+#          If @base, @top, @base-node-name, @top-node-name invalid, 
GenericError
 #          If @speed is invalid, InvalidParameter
+#          If both @base and @base-node-name are specified, GenericError
+#          If both @top and @top-node-name are specified, GenericError
 #
 # Since: 1.3
 #
 ##
 { 'command': 'block-commit',
-  'data': { 'device': 'str', '*base': 'str', '*top': 'str',
-            '*speed': 'int' } }
+  'data': { 'device': 'str', '*base': 'str', '*base-node-name': 'str',
+            '*top': 'str', '*top-node-name': 'str', '*speed': 'int' } }
 
 ##
 # @drive-backup
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 1aa3c65..2b9b1dc 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -985,7 +985,7 @@ EQMP
 
     {
         .name       = "block-commit",
-        .args_type  = "device:B,base:s?,top:s?,speed:o?",
+        .args_type  = 
"device:B,base:s?,base-node-name:s?,top:s?,top-node-name:s?,speed:o?",
         .mhandler.cmd_new = qmp_marshal_input_block_commit,
     },
 
@@ -999,12 +999,27 @@ data between 'top' and 'base' into 'base'.
 Arguments:
 
 - "device": The device's ID, must be unique (json-string)
-- "base": The file name of the backing image to write data into.
-          If not specified, this is the deepest backing image
-          (json-string, optional)
-- "top":  The file name of the backing image within the image chain,
-          which contains the topmost data to be committed down. If
-          not specified, this is the active layer. (json-string, optional)
+
+For 'base', either base or base-node-name may be set but not both. If
+neither is specified, this is the deepest backing image
+
+- "base":           The file name of the backing image to write data into.
+                    (json-string, optional)
+- "base-node-name": The name of the block driver state node of the
+                    backing image to write data into.
+                    (json-string, optional) (Since 2.1)
+
+For 'top', either top or top-node-name must be set but not both.
+
+- "top":            The file name of the backing image within the image chain,
+                    which contains the topmost data to be committed down. If
+                    not specified, this is the active layer.
+                    (json-string, optional)
+
+- "top-node-name": The block driver state node name of the backing
+                   image within the image chain, which contains the
+                   topmost data to be committed down.
+                   (json-string, optional) (Since 2.1)
 
           If top == base, that is an error.
           If top == active, the job will not be completed by itself,
-- 
1.8.3.1