[Qemu-devel] [PATCH v3 7/9] qmp: add block_job_cancel command

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

Add block_job_cancel, which stops an active block streaming operation.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 blockdev.c       |   19 ++++++++++++++++++-
 hmp-commands.hx  |   14 ++++++++++++++
 hmp.c            |   13 +++++++++++++
 hmp.h            |    1 +
 monitor.c        |    3 +++
 monitor.h        |    1 +
 qapi-schema.json |   36 ++++++++++++++++++++++++++++++++++++
 qmp-commands.hx  |   18 ++++++++++++++++++
 trace-events     |    1 +
 9 files changed, 105 insertions(+), 1 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index b101ba1..b276b2f 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -919,7 +919,11 @@ static void block_stream_cb(void *opaque, int ret)
         qdict_put(dict, "error", qstring_from_str(strerror(-ret)));
     }
 
-    monitor_protocol_event(QEVENT_BLOCK_JOB_COMPLETED, obj);
+    if (block_job_is_cancelled(bs->job)) {
+        monitor_protocol_event(QEVENT_BLOCK_JOB_CANCELLED, obj);
+    } else {
+        monitor_protocol_event(QEVENT_BLOCK_JOB_COMPLETED, obj);
+    }
     qobject_decref(obj);
 }
 
@@ -980,3 +984,16 @@ void qmp_block_job_set_speed(const char *device, int64_t value, Error **errp)
         error_set(errp, QERR_NOT_SUPPORTED);
     }
 }
+
+void qmp_block_job_cancel(const char *device, Error **errp)
+{
+    BlockJob *job = find_block_job(device);
+
+    if (!job) {
+        error_set(errp, QERR_DEVICE_NOT_ACTIVE, device);
+        return;
+    }
+
+    trace_qmp_block_job_cancel(job);
+    block_job_cancel(job);
+}
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 788ec97..cc91055 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -99,6 +99,20 @@ 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",
+        .mhandler.cmd = hmp_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/hmp.c b/hmp.c
index f3edf7c..66d9d0f 100644
--- a/hmp.c
+++ b/hmp.c
@@ -559,3 +559,16 @@ void hmp_block_job_set_speed(Monitor *mon, const QDict *qdict)
         error_free(error);
     }
 }
+
+void hmp_block_job_cancel(Monitor *mon, const QDict *qdict)
+{
+    Error *error = NULL;
+    const char *device = qdict_get_str(qdict, "device");
+
+    qmp_block_job_cancel(device, &error);
+
+    if (error) {
+        monitor_printf(mon, "%s\n", error_get_pretty(error));
+        error_free(error);
+    }
+}
diff --git a/hmp.h b/hmp.h
index 4c1458e..30d9051 100644
--- a/hmp.h
+++ b/hmp.h
@@ -39,5 +39,6 @@ void hmp_system_powerdown(Monitor *mon, const QDict *qdict);
 void hmp_cpu(Monitor *mon, const QDict *qdict);
 void hmp_block_stream(Monitor *mon, const QDict *qdict);
 void hmp_block_job_set_speed(Monitor *mon, const QDict *qdict);
+void hmp_block_job_cancel(Monitor *mon, const QDict *qdict);
 
 #endif
diff --git a/monitor.c b/monitor.c
index a33218c..5bf29f2 100644
--- a/monitor.c
+++ b/monitor.c
@@ -482,6 +482,9 @@ void monitor_protocol_event(MonitorEvent event, QObject *data)
         case QEVENT_BLOCK_JOB_COMPLETED:
             event_name = "BLOCK_JOB_COMPLETED";
             break;
+        case QEVENT_BLOCK_JOB_CANCELLED:
+            event_name = "BLOCK_JOB_CANCELLED";
+            break;
         default:
             abort();
             break;
diff --git a/monitor.h b/monitor.h
index d9b07dc..2e7f38a 100644
--- a/monitor.h
+++ b/monitor.h
@@ -36,6 +36,7 @@ typedef enum MonitorEvent {
     QEVENT_SPICE_INITIALIZED,
     QEVENT_SPICE_DISCONNECTED,
     QEVENT_BLOCK_JOB_COMPLETED,
+    QEVENT_BLOCK_JOB_CANCELLED,
     QEVENT_MAX,
 } MonitorEvent;
 
diff --git a/qapi-schema.json b/qapi-schema.json
index f6a8252..270d05e 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -943,6 +943,10 @@
 # - speed:    rate limit, bytes per second (json-int)
 # - error:    error message (json-string, only on error)
 #
+# If the operation was cancelled using block_job_cancel then the
+# BLOCK_JOB_CANCELLED event is raised with the same fields as
+# BLOCK_JOB_COMPLETED.
+#
 # The completion event is raised both on success and on failure.  On
 # success offset is equal to len.  On failure offset and len can be
 # used to indicate at which point the operation failed.
@@ -977,3 +981,35 @@
 ##
 { 'command': 'block_job_set_speed',
   'data': { 'device': 'str', 'value': 'int' } }
+
+##
+# @block_job_cancel:
+#
+# Stop an active block streaming operation.
+#
+# This command returns immediately after marking the active block streaming
+# operation for cancellation.  It is an error to call this command if no
+# operation is in progress.
+#
+# The operation will cancel as soon as possible and emit the
+# BLOCK_JOB_CANCELLED event.  Before that happens the job is still visible when
+# enumerated using query-block-jobs.
+#
+# 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
+#
+# Errors:
+#
+# DeviceNotActive: streaming is not active on this device
+# DeviceInUse:     cancellation already in progress
+#
+# Since: 1.1
+##
+{ 'command': 'block_job_cancel', 'data': { 'device': 'str' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 5541ca0..a57d079 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -719,6 +719,24 @@ Example:
 EQMP
 
     {
+        .name       = "block_job_cancel",
+        .args_type  = "device:B",
+        .mhandler.cmd_new = qmp_marshal_input_block_job_cancel,
+    },
+
+SQMP
+block_job_cancel
+----------------
+See qapi-schema.json for documentation.
+
+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]",
diff --git a/trace-events b/trace-events
index 6c1eec2..cbca6d5 100644
--- a/trace-events
+++ b/trace-events
@@ -74,6 +74,7 @@ stream_one_iteration(void *s, int64_t sector_num, int nb_sectors, int is_allocat
 stream_start(void *bs, void *base, void *s, void *co, void *opaque) "bs %p base %p s %p co %p opaque %p"
 
 # blockdev.c
+qmp_block_job_cancel(void *job) "job %p"
 block_stream_cb(void *bs, void *job, int ret) "bs %p job %p ret %d"
 qmp_block_stream(void *bs, void *job) "bs %p job %p"
 
-- 
1.7.7.3