[Qemu-devel] [PATCH 6/8] QAPI: add command for live block commit, 'block-commit'

[Jeff Cody]

The command for live block commit is added, which has the following
arguments:

device: the block device to perform the commit on (mandatory)
base:   the base image to commit into; optional (if not specified,
        it is the underlying original image)
top:    the top image of the commit - all data from inside top down
        to base will be committed into base. optional (if not specified,
        it is the active image) - see note below
speed:  maximum speed, in bytes/sec
on_error: action to take on error (optional - default is report)

note: eventually this will support merging down the active layer,
      but that code is not yet complete.  If the active layer is passed
      in currently as top, or top is left to the default, then the error
      QERR_TOP_NOT_FOUND will be returned.

The is done as a block job, so upon completion a BLOCK_JOB_COMPLETED will
be emitted.

Signed-off-by: Jeff Cody <address@hidden>
---
 QMP/qmp-events.txt |  6 +++--
 blockdev.c         | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 qapi-schema.json   | 35 +++++++++++++++++++++++++++++
 qmp-commands.hx    |  6 +++++
 4 files changed, 109 insertions(+), 3 deletions(-)

diff --git a/QMP/qmp-events.txt b/QMP/qmp-events.txt
index 2878058..4491020 100644
--- a/QMP/qmp-events.txt
+++ b/QMP/qmp-events.txt
@@ -50,7 +50,8 @@ Emitted when a block job has been cancelled.
 
 Data:
 
-- "type":     Job type ("stream" for image streaming, json-string)
+- "type":     Job type (json-string; "stream" for image streaming
+                                     "commit" for block commit)
 - "device":   Device name (json-string)
 - "len":      Maximum progress value (json-int)
 - "offset":   Current progress value (json-int)
@@ -73,7 +74,8 @@ Emitted when a block job has completed.
 
 Data:
 
-- "type":     Job type ("stream" for image streaming, json-string)
+- "type":     Job type (json-string; "stream" for image streaming
+                                     "commit" for block commit)
 - "device":   Device name (json-string)
 - "len":      Maximum progress value (json-int)
 - "offset":   Current progress value (json-int)
diff --git a/blockdev.c b/blockdev.c
index 9caa16f..785e999 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -825,7 +825,6 @@ exit:
     return;
 }
 
-
 static void eject_device(BlockDriverState *bs, int force, Error **errp)
 {
     if (bdrv_in_use(bs)) {
@@ -1124,6 +1123,70 @@ void qmp_block_stream(const char *device, bool has_base,
     trace_qmp_block_stream(bs, bs->job);
 }
 
+void qmp_block_commit(const char *device,
+                      bool has_base, const char *base,
+                      bool has_top, const char *top,
+                      bool has_speed, int64_t speed,
+                      Error **errp)
+{
+    BlockDriverState *bs;
+    BlockDriverState *base_bs, *top_bs;
+    Error *local_err = NULL;
+    /* This will be part of the QMP command, if/when the
+     * BlockdevOnError change for blkmirror makes it in
+     */
+    BlockErrorAction on_error = BLOCK_ERR_REPORT;
+
+    /* drain all i/o before commits */
+    bdrv_drain_all();
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+    if (base && has_base) {
+        base_bs = bdrv_find_backing_image(bs, base);
+    } else {
+        base_bs = bdrv_find_base(bs);
+    }
+
+    if (base_bs == NULL) {
+        error_set(errp, QERR_BASE_NOT_FOUND, base ? base : "NULL");
+        return;
+    }
+
+    if (top && has_top) {
+        /* if we want to allow the active layer,
+         * use 'bdrv_find_image()' here */
+        top_bs = bdrv_find_backing_image(bs, top);
+    } else {
+        /* default is one below the active layer, unless that is
+         * the base */
+        top_bs = bs->backing_hd;
+        if (top_bs == base_bs) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "Invalid files for merge: top and base are the same");
+            return;
+        }
+    }
+    if (top_bs == NULL) {
+        error_set(errp, QERR_TOP_NOT_FOUND, top ? top : "NULL");
+        return;
+    }
+
+    commit_start(bs, base_bs, top_bs, speed, on_error, block_job_cb, bs,
+                &local_err);
+    if (local_err != NULL) {
+        error_propagate(errp, local_err);
+        return;
+    }
+    /* Grab a reference so hotplug does not delete the BlockDriverState from
+     * underneath us.
+     */
+    drive_get_ref(drive_get_by_blockdev(bs));
+}
+
 static BlockJob *find_block_job(const char *device)
 {
     BlockDriverState *bs;
diff --git a/qapi-schema.json b/qapi-schema.json
index a9f465a..c99ccfa 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1404,6 +1404,41 @@
   'returns': 'str' }
 
 ##
+# @block-commit
+#
+# Live commit of data from child image nodes into parent nodes - i.e.,
+# writes data between 'top' and 'base' into 'base'.
+#
+# @device:  the name of the device
+#
+# @base:   #optional The file name of the parent image of the device to write
+#                    data into.  If not specified, this is the original parent
+#                    image.
+#
+# @top:    #optional The file name of the child image, above which data will
+#                    not be committed down.  If not specified, this is one
+#                    layer below the active layer (i.e. active->backing_hd).
+#
+#                    If top == base, that is an error.
+#
+#
+# @speed:  #optional the maximum speed, in bytes per second
+#
+# Returns: Nothing on success
+#          If commit or stream is already active on this device, DeviceInUse
+#          If @device does not exist, DeviceNotFound
+#          If image commit is not supported by this device, NotSupported
+#          If @base does not exist, BaseNotFound
+#          If @top does not exist, TopNotFound
+#          If @speed is invalid, InvalidParameter
+#
+# Since: 1.3
+#
+##
+{ 'command': 'block-commit',
+  'data': { 'device': 'str', '*base': 'str', '*top': 'str',
+            '*speed': 'int' } }
+
 # @migrate_cancel
 #
 # Cancel the current executing migration process.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 6e21ddb..e244763 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -792,6 +792,12 @@ EQMP
     },
 
     {
+        .name       = "block-commit",
+        .args_type  = "device:B,base:s?,top:s?,speed:o?",
+        .mhandler.cmd_new = qmp_marshal_input_block_commit,
+    },
+
+    {
         .name       = "block-job-set-speed",
         .args_type  = "device:B,speed:o",
         .mhandler.cmd_new = qmp_marshal_input_block_job_set_speed,
-- 
1.7.11.4