[Qemu-devel] [PATCH 3/4] qmp: add block_job_cancel command

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

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

block_job_cancel
----------------

Stop an active block streaming operation.

This command returns once the active block streaming operation has been
stopped.  It is an error to call this command if no operation is in
progress.

The image file retains its backing file unless the streaming operation
happens to complete just as it is being cancelled.

A new block streaming operation can be started at a later time to finish
copying all data from the backing file.

Arguments:

- device: device name (json-string)

Errors:

DeviceNotActive: streaming is not active on this device
DeviceInUse:     cancellation already in progress

Examples:

-> { "execute": "block_job_cancel", "arguments": { "device": "virtio0" }
}
<- { "return":  {} }

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 blockdev.c      |    8 ++++++++
 blockdev.h      |    1 +
 hmp-commands.hx |   15 +++++++++++++++
 qmp-commands.hx |   40 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 64 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index ee40263..036b7eb 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -827,3 +827,11 @@ int do_block_job_set_speed(Monitor *mon, const QDict *params,
     qerror_report(QERR_NOT_SUPPORTED);
     return -1;
 }
+
+int do_block_job_cancel(Monitor *mon, const QDict *params, QObject **ret_data)
+{
+    const char *device = qdict_get_str(params, "device");
+
+    qerror_report(QERR_DEVICE_NOT_ACTIVE, device);
+    return -1;
+}
diff --git a/blockdev.h b/blockdev.h
index 6b48405..a132d36 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -68,5 +68,6 @@ 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);
+int do_block_job_cancel(Monitor *mon, const QDict *qdict, QObject **ret_data);
 
 #endif
diff --git a/hmp-commands.hx b/hmp-commands.hx
index a5fb4d5..ff1a54b 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -101,6 +101,21 @@ Set maximum speed for a background block operation.
 ETEXI
 
     {
+        .name       = "block_job_cancel",
+        .args_type  = "device:B",
+        .params     = "device",
+        .help       = "stop an active block streaming operation",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_job_cancel,
+    },
+
+STEXI
+@item block_job_cancel
+@findex block_job_cancel
+Stop an active block streaming operation.
+ETEXI
+
+    {
         .name       = "eject",
         .args_type  = "force:-f,device:B",
         .params     = "[-f] device",
diff --git a/qmp-commands.hx b/qmp-commands.hx
index eface05..de442f7 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -794,6 +794,46 @@ Example:
 EQMP
 
     {
+        .name       = "block_job_cancel",
+        .args_type  = "device:B",
+        .params     = "device",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_job_cancel,
+    },
+
+SQMP
+
+block_job_cancel
+----------------
+
+Stop an active block streaming operation.
+
+This command returns once the active block streaming operation has been
+stopped.  It is an error to call this command if no operation is in progress.
+
+The image file retains its backing file unless the streaming operation happens
+to complete just as it is being cancelled.
+
+A new block streaming operation can be started at a later time to finish
+copying all data from the backing file.
+
+Arguments:
+
+- device: device name (json-string)
+
+Errors:
+
+DeviceNotActive: streaming is not active on this device
+DeviceInUse:     cancellation already in progress
+
+Examples:
+
+-> { "execute": "block_job_cancel", "arguments": { "device": "virtio0" } }
+<- { "return":  {} }
+
+EQMP
+
+    {
         .name       = "blockdev-snapshot-sync",
         .args_type  = "device:B,snapshot-file:s?,format:s?",
         .params     = "device [new-image-file] [format]",
-- 
1.7.5.4