qmp: add block-job-pause and block-job-resume

Add QMP commands matching the functionality.

Paused jobs cannot be canceled without first resuming them.  This
ensures that I/O errors are never missed by management.  However, an
optional force argument can be specified to allow that.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -1213,7 +1213,29 @@ void qmp_block_job_set_speed(const char *device, int64_t speed, Error **errp)
     block_job_set_speed(job, speed, errp);
 }
 
-void qmp_block_job_cancel(const char *device, Error **errp)
+void qmp_block_job_cancel(const char *device,
+                          bool has_force, bool force, Error **errp)
+{
+    BlockJob *job = find_block_job(device);
+
+    if (!has_force) {
+        force = false;
+    }
+
+    if (!job) {
+        error_set(errp, QERR_BLOCK_JOB_NOT_ACTIVE, device);
+        return;
+    }
+    if (job->paused && !force) {
+        error_set(errp, QERR_BLOCK_JOB_PAUSED, device);
+        return;
+    }
+
+    trace_qmp_block_job_cancel(job);
+    block_job_cancel(job);
+}
+
+void qmp_block_job_pause(const char *device, Error **errp)
 {
     BlockJob *job = find_block_job(device);
 
@@ -1221,13 +1243,22 @@ void qmp_block_job_cancel(const char *device, Error **errp)
         error_set(errp, QERR_BLOCK_JOB_NOT_ACTIVE, device);
         return;
     }
-    if (job->paused) {
-        error_set(errp, QERR_BLOCK_JOB_PAUSED, device);
+
+    trace_qmp_block_job_pause(job);
+    block_job_pause(job);
+}
+
+void qmp_block_job_resume(const char *device, Error **errp)
+{
+    BlockJob *job = find_block_job(device);
+
+    if (!job) {
+        error_set(errp, QERR_BLOCK_JOB_NOT_ACTIVE, device);
         return;
     }
 
-    trace_qmp_block_job_cancel(job);
-    block_job_cancel(job);
+    trace_qmp_block_job_resume(job);
+    block_job_resume(job);
 }
 
 static void do_qmp_query_block_jobs_one(void *opaque, BlockDriverState *bs)

hmp-commands.hx

@@ -99,9 +99,10 @@ ETEXI
 
     {
         .name       = "block_job_cancel",
-        .args_type  = "device:B",
-        .params     = "device",
-        .help       = "stop an active background block operation",
+        .args_type  = "force:-f,device:B",
+        .params     = "[-f] device",
+        .help       = "stop an active background block operation (use -f"
+                      "\n\t\t\t if the operation is currently paused)",
         .mhandler.cmd = hmp_block_job_cancel,
     },
 
@@ -109,6 +110,34 @@ STEXI
 @item block_job_cancel
 @findex block_job_cancel
 Stop an active block streaming operation.
+ETEXI
+
+    {
+        .name       = "block_job_pause",
+        .args_type  = "device:B",
+        .params     = "device",
+        .help       = "pause an active background block operation",
+        .mhandler.cmd = hmp_block_job_pause,
+    },
+
+STEXI
+@item block_job_pause
+@findex block_job_pause
+Pause an active block streaming operation.
+ETEXI
+
+    {
+        .name       = "block_job_resume",
+        .args_type  = "device:B",
+        .params     = "device",
+        .help       = "resume a paused background block operation",
+        .mhandler.cmd = hmp_block_job_resume,
+    },
+
+STEXI
+@item block_job_resume
+@findex block_job_resume
+Resume a paused block streaming operation.
 ETEXI
 
     {

hmp.c

@@ -950,8 +950,29 @@ void hmp_block_job_cancel(Monitor *mon, const QDict *qdict)
 {
     Error *error = NULL;
     const char *device = qdict_get_str(qdict, "device");
+    bool force = qdict_get_try_bool(qdict, "force", 0);
 
-    qmp_block_job_cancel(device, &error);
+    qmp_block_job_cancel(device, true, force, &error);
+
+    hmp_handle_error(mon, &error);
+}
+
+void hmp_block_job_pause(Monitor *mon, const QDict *qdict)
+{
+    Error *error = NULL;
+    const char *device = qdict_get_str(qdict, "device");
+
+    qmp_block_job_pause(device, &error);
+
+    hmp_handle_error(mon, &error);
+}
+
+void hmp_block_job_resume(Monitor *mon, const QDict *qdict)
+{
+    Error *error = NULL;
+    const char *device = qdict_get_str(qdict, "device");
+
+    qmp_block_job_resume(device, &error);
 
     hmp_handle_error(mon, &error);
 }

hmp.h

@@ -64,6 +64,8 @@ void hmp_block_set_io_throttle(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);
+void hmp_block_job_pause(Monitor *mon, const QDict *qdict);
+void hmp_block_job_resume(Monitor *mon, const QDict *qdict);
 void hmp_migrate(Monitor *mon, const QDict *qdict);
 void hmp_device_del(Monitor *mon, const QDict *qdict);
 void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);

qapi-schema.json

@@ -1893,12 +1893,56 @@
 #
 # @device: the device name
 #
+# @force: #optional whether to allow cancellation of a paused job (default
+#         false).  Since 1.3.
+#
 # Returns: Nothing on success
 #          If no background operation is active on this device, DeviceNotActive
 #
 # Since: 1.1
 ##
-{ 'command': 'block-job-cancel', 'data': { 'device': 'str' } }
+{ 'command': 'block-job-cancel', 'data': { 'device': 'str', '*force': 'bool' } }
+
+##
+# @block-job-pause:
+#
+# Pause an active background block operation.
+#
+# This command returns immediately after marking the active background block
+# operation for pausing.  It is an error to call this command if no
+# operation is in progress.  Pausing an already paused job has no cumulative
+# effect; a single block-job-resume command will resume the job.
+#
+# The operation will pause as soon as possible.  No event is emitted when
+# the operation is actually paused.  Cancelling a paused job automatically
+# resumes it.
+#
+# @device: the device name
+#
+# Returns: Nothing on success
+#          If no background operation is active on this device, DeviceNotActive
+#
+# Since: 1.3
+##
+{ 'command': 'block-job-pause', 'data': { 'device': 'str' } }
+
+##
+# @block-job-resume:
+#
+# Resume an active background block operation.
+#
+# This command returns immediately after resuming a paused background block
+# operation.  It is an error to call this command if no operation is in
+# progress.  Resuming an already running job is not an error.
+#
+# @device: the device name
+#
+# Returns: Nothing on success
+#          If no background operation is active on this device, DeviceNotActive
+#
+# Since: 1.3
+##
+{ 'command': 'block-job-resume', 'data': { 'device': 'str' } }
 
 ##
 # @ObjectTypeInfo:

qmp-commands.hx

@@ -805,9 +805,19 @@ EQMP
 
     {
         .name       = "block-job-cancel",
-        .args_type  = "device:B",
+        .args_type  = "device:B,force:b?",
         .mhandler.cmd_new = qmp_marshal_input_block_job_cancel,
     },
+    {
+        .name       = "block-job-pause",
+        .args_type  = "device:B",
+        .mhandler.cmd_new = qmp_marshal_input_block_job_pause,
+    },
+    {
+        .name       = "block-job-resume",
+        .args_type  = "device:B",
+        .mhandler.cmd_new = qmp_marshal_input_block_job_resume,
+    },
     {
         .name       = "transaction",
         .args_type  = "actions:q",

trace-events

@@ -79,6 +79,8 @@ commit_start(void *bs, void *base, void *top, void *s, void *co, void *opaque) "
 
 # blockdev.c
 qmp_block_job_cancel(void *job) "job %p"
+qmp_block_job_pause(void *job) "job %p"
+qmp_block_job_resume(void *job) "job %p"
 block_job_cb(void *bs, void *job, int ret) "bs %p job %p ret %d"
 qmp_block_stream(void *bs, void *job) "bs %p job %p"