[Qemu-devel] [PATCH 6/8] 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      |   35 +++++++++++++++++++++++++++++++++++
 blockdev.h      |    3 +++
 hmp-commands.hx |   16 ++++++++++++++++
 qmp-commands.hx |   41 +++++++++++++++++++++++++++++++++++++++++
 trace-events    |    2 ++
 5 files changed, 97 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 781825b..5ad7d3b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -884,3 +884,38 @@ int do_block_job_set_speed(Monitor *mon, const QDict *params,
     }
     return 0;
 }
+
+typedef struct BlockJobCancelData {
+    MonitorCompletion *cb;
+    void *opaque;
+} BlockJobCancelData;
+
+static void do_block_job_cancel_cb(void *opaque)
+{
+    BlockJobCancelData *cancel_data = opaque;
+
+    trace_block_job_cancel_cb(cancel_data, cancel_data->opaque);
+
+    cancel_data->cb(cancel_data->opaque, NULL);
+    g_free(cancel_data);
+}
+
+int do_block_job_cancel(Monitor *mon, const QDict *params,
+                        MonitorCompletion *cb, void *opaque)
+{
+    const char *device = qdict_get_str(params, "device");
+    BlockJob *job = find_block_job(device);
+    BlockJobCancelData *cancel_data;
+
+    if (!job) {
+        qerror_report(QERR_DEVICE_NOT_ACTIVE, device);
+        return -1;
+    }
+
+    cancel_data = g_malloc(sizeof(*cancel_data));
+    cancel_data->cb = cb;
+    cancel_data->opaque = opaque;
+    trace_do_block_job_cancel(job, cancel_data, opaque);
+    block_job_cancel(job, do_block_job_cancel_cb, cancel_data);
+    return 0;
+}
diff --git a/blockdev.h b/blockdev.h
index 6b48405..7d3db30 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -11,6 +11,7 @@
 #define BLOCKDEV_H
 
 #include "block.h"
+#include "monitor.h"
 #include "qemu-queue.h"
 
 void blockdev_mark_auto_del(BlockDriverState *bs);
@@ -68,5 +69,7 @@ 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 *params,
+                        MonitorCompletion *cb, void *opaque);
 
 #endif
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 2cdfa0b..a8b83f0 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -101,6 +101,22 @@ 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_async = do_block_job_cancel,
+        .flags      = MONITOR_CMD_ASYNC,
+    },
+
+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 6cfb548..741c2f8 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -785,6 +785,47 @@ Example:
 EQMP
 
     {
+        .name       = "block_job_cancel",
+        .args_type  = "device:B",
+        .params     = "device",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_async = do_block_job_cancel,
+        .flags      = MONITOR_CMD_ASYNC,
+    },
+
+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]",
diff --git a/trace-events b/trace-events
index 15a6b7a..39023cc 100644
--- a/trace-events
+++ b/trace-events
@@ -76,6 +76,8 @@ stream_one_iteration(void *s, int64_t sector_num, int max_sectors) "s %p sector_
 stream_start(void *bs, void *base, void *s, void *co, void *opaque) "bs %p base %p s %p co %p opaque %p"
 
 # blockdev.c
+block_job_cancel_cb(void *cancel_data, void *opaque) "cancel_data %p opaque %p"
+do_block_job_cancel(void *job, void *cancel_data, void *opaque) "job %p cancel_data %p opaque %p"
 block_stream_cb(void *bs, void *job, int ret) "bs %p job %p ret %d"
 do_block_stream(void *bs, void *job) "bs %p job %p"
 
-- 
1.7.7