[Qemu-devel] [PATCH 2/4] qmp: add block_job_set_speed command

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

This patch introduces the block_job_set_speed HMP/QMP command.  It is
currently unimplemented and returns the 'NotSupported' error.

block_job_set_speed
-------------------

Set maximum speed for a background block operation.

This command can only be issued when there is an active block job.

Throttling can be disabled by setting the speed to 0.

Arguments:

- device: device name (json-string)
- value:  maximum speed, in bytes per second (json-int)

Errors:
NotSupported:    job type does not support speed setting
DeviceNotActive: streaming is not active on this device

Example:

-> { "execute": "block_job_set_speed",
    "arguments": { "device": "virtio0", "value": 1024 } }

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 blockdev.c      |   19 +++++++++++++++++++
 blockdev.h      |    2 ++
 hmp-commands.hx |   15 +++++++++++++++
 qmp-commands.hx |   35 +++++++++++++++++++++++++++++++++++
 4 files changed, 71 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 208bfc9..ee40263 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -808,3 +808,22 @@ int do_block_stream(Monitor *mon, const QDict *params, QObject **ret_data)
     qerror_report(QERR_NOT_SUPPORTED);
     return -1;
 }
+
+int do_block_job_set_speed(Monitor *mon, const QDict *params,
+                           QObject **ret_data)
+{
+    const char *device = qdict_get_str(params, "device");
+    BlockDriverState *bs;
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        qerror_report(QERR_DEVICE_NOT_ACTIVE, device);
+        return -1;
+    }
+
+    /* This command is not yet implemented.  The device not found check above
+     * is done so that error ordering will not change when fully implemented.
+     */
+    qerror_report(QERR_NOT_SUPPORTED);
+    return -1;
+}
diff --git a/blockdev.h b/blockdev.h
index ad98d37..6b48405 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -66,5 +66,7 @@ int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data);
 int do_snapshot_blkdev(Monitor *mon, const QDict *qdict, QObject **ret_data);
 int do_block_resize(Monitor *mon, const QDict *qdict, QObject **ret_data);
 int do_block_stream(Monitor *mon, const QDict *qdict, QObject **ret_data);
+int do_block_job_set_speed(Monitor *mon, const QDict *qdict,
+                           QObject **ret_data);
 
 #endif
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 2a16fd9..a5fb4d5 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -86,6 +86,21 @@ Copy data from a backing file into a block device.
 ETEXI
 
     {
+        .name       = "block_job_set_speed",
+        .args_type  = "device:B,value:o",
+        .params     = "device value",
+        .help       = "set maximum speed for a background block operation",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_job_set_speed,
+    },
+
+STEXI
+@item block_job_set_stream
+@findex block_job_set_stream
+Set maximum speed for a background block operation.
+ETEXI
+
+    {
         .name       = "eject",
         .args_type  = "force:-f,device:B",
         .params     = "[-f] device",
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 60c9bdf..eface05 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -759,6 +759,41 @@ Examples:
 EQMP
 
     {
+        .name       = "block_job_set_speed",
+        .args_type  = "device:B,value:o",
+        .params     = "device value",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_job_set_speed,
+    },
+
+SQMP
+
+block_job_set_speed
+-------------------
+
+Set maximum speed for a background block operation.
+
+This command can only be issued when there is an active block job.
+
+Throttling can be disabled by setting the speed to 0.
+
+Arguments:
+
+- device: device name (json-string)
+- value:  maximum speed, in bytes per second (json-int)
+
+Errors:
+NotSupported:    job type does not support speed setting
+DeviceNotActive: streaming is not active on this device
+
+Example:
+
+-> { "execute": "block_job_set_speed",
+    "arguments": { "device": "virtio0", "value": 1024 } }
+
+EQMP
+
+    {
         .name       = "blockdev-snapshot-sync",
         .args_type  = "device:B,snapshot-file:s?,format:s?",
         .params     = "device [new-image-file] [format]",
-- 
1.7.5.4