[Qemu-devel] [PATCH 4/8] qmp: add block_stream command

[Stefan Hajnoczi]

Add the block_stream command, which starts copy backing file contents
into the image file.  Later patches add control over the background copy
speed, cancelation, and querying running streaming operations.

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 blockdev.c      |   69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 blockdev.h      |    1 +
 hmp-commands.hx |   14 +++++++++++
 monitor.c       |    3 ++
 monitor.h       |    1 +
 qerror.c        |    4 +++
 qerror.h        |    3 ++
 qmp-commands.hx |   65 +++++++++++++++++++++++++++++++++++++++++++++++++++
 trace-events    |    4 +++
 9 files changed, 164 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 1dd0f23..de911de 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -13,8 +13,10 @@
 #include "qerror.h"
 #include "qemu-option.h"
 #include "qemu-config.h"
+#include "qemu-objects.h"
 #include "sysemu.h"
 #include "block_int.h"
+#include "trace.h"
 
 static QTAILQ_HEAD(drivelist, DriveInfo) drives = 
QTAILQ_HEAD_INITIALIZER(drives);
 
@@ -782,3 +784,70 @@ int do_block_resize(Monitor *mon, const QDict *qdict, 
QObject **ret_data)
 
     return 0;
 }
+
+static QObject *qobject_from_block_job(BlockJob *job)
+{
+    return qobject_from_jsonf("{ 'type': %s,"
+                              "'device': %s,"
+                              "'len': %" PRId64 ","
+                              "'offset': %" PRId64 ","
+                              "'speed': %" PRId64 " }",
+                              job->job_type->job_type,
+                              bdrv_get_device_name(job->bs),
+                              job->len,
+                              job->offset,
+                              job->speed);
+}
+
+static void block_stream_cb(void *opaque, int ret)
+{
+    BlockDriverState *bs = opaque;
+    QObject *obj;
+
+    trace_block_stream_cb(bs, bs->job, ret);
+
+    assert(bs->job);
+    obj = qobject_from_block_job(bs->job);
+    if (ret < 0) {
+        QDict *dict = qobject_to_qdict(obj);
+        qdict_put(dict, "error", qstring_from_str(strerror(-ret)));
+    }
+
+    monitor_protocol_event(QEVENT_BLOCK_JOB_COMPLETED, obj);
+    qobject_decref(obj);
+}
+
+int do_block_stream(Monitor *mon, const QDict *params, QObject **ret_data)
+{
+    const char *device = qdict_get_str(params, "device");
+    const char *base = qdict_get_try_str(params, "base");
+    BlockDriverState *bs;
+    int ret;
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        qerror_report(QERR_DEVICE_NOT_FOUND, device);
+        return -1;
+    }
+
+    /* Base device not supported */
+    if (base) {
+        qerror_report(QERR_NOT_SUPPORTED);
+        return -1;
+    }
+
+    ret = stream_start(bs, NULL, block_stream_cb, bs);
+    if (ret < 0) {
+        switch (ret) {
+        case -EBUSY:
+            qerror_report(QERR_DEVICE_IN_USE, device);
+            return -1;
+        default:
+            qerror_report(QERR_NOT_SUPPORTED);
+            return -1;
+        }
+    }
+
+    trace_do_block_stream(bs, bs->job);
+    return 0;
+}
diff --git a/blockdev.h b/blockdev.h
index 3587786..ad98d37 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -65,5 +65,6 @@ int do_change_block(Monitor *mon, const char *device,
 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);
 
 #endif
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 05a1498..2aeb2e0 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -70,6 +70,20 @@ but should be used with extreme caution.  Note that this 
command only
 resizes image files, it can not resize block devices like LVM volumes.
 ETEXI
 
+    {
+        .name       = "block_stream",
+        .args_type  = "device:B,base:s?",
+        .params     = "device [base]",
+        .help       = "copy data from a backing file into a block device",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_stream,
+    },
+
+STEXI
address@hidden block_stream
address@hidden block_stream
+Copy data from a backing file into a block device.
+ETEXI
 
     {
         .name       = "eject",
diff --git a/monitor.c b/monitor.c
index ffda0fe..38addcf 100644
--- a/monitor.c
+++ b/monitor.c
@@ -482,6 +482,9 @@ void monitor_protocol_event(MonitorEvent event, QObject 
*data)
         case QEVENT_SPICE_DISCONNECTED:
             event_name = "SPICE_DISCONNECTED";
             break;
+        case QEVENT_BLOCK_JOB_COMPLETED:
+            event_name = "BLOCK_JOB_COMPLETED";
+            break;
         default:
             abort();
             break;
diff --git a/monitor.h b/monitor.h
index 4f2d328..135c927 100644
--- a/monitor.h
+++ b/monitor.h
@@ -35,6 +35,7 @@ typedef enum MonitorEvent {
     QEVENT_SPICE_CONNECTED,
     QEVENT_SPICE_INITIALIZED,
     QEVENT_SPICE_DISCONNECTED,
+    QEVENT_BLOCK_JOB_COMPLETED,
     QEVENT_MAX,
 } MonitorEvent;
 
diff --git a/qerror.c b/qerror.c
index 68998d4..f531afa 100644
--- a/qerror.c
+++ b/qerror.c
@@ -162,6 +162,10 @@ static const QErrorStringTable qerror_table[] = {
         .desc      = "No '%(bus)' bus found for device '%(device)'",
     },
     {
+        .error_fmt = QERR_NOT_SUPPORTED,
+        .desc      = "Not supported",
+    },
+    {
         .error_fmt = QERR_OPEN_FILE_FAILED,
         .desc      = "Could not open '%(filename)'",
     },
diff --git a/qerror.h b/qerror.h
index d4bfcfd..3988610 100644
--- a/qerror.h
+++ b/qerror.h
@@ -141,6 +141,9 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_NO_BUS_FOR_DEVICE \
     "{ 'class': 'NoBusForDevice', 'data': { 'device': %s, 'bus': %s } }"
 
+#define QERR_NOT_SUPPORTED \
+    "{ 'class': 'NotSupported', 'data': {} }"
+
 #define QERR_OPEN_FILE_FAILED \
     "{ 'class': 'OpenFileFailed', 'data': { 'filename': %s } }"
 
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 4328e8b..31cde4b 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -685,6 +685,71 @@ Example:
 EQMP
 
     {
+        .name       = "block_stream",
+        .args_type  = "device:B,base:s?",
+        .params     = "device [base]",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_stream,
+    },
+
+SQMP
+block_stream
+------------
+
+Copy data from a backing file into a block device.
+
+The block streaming operation is performed in the background until the entire
+backing file has been copied.  This command returns immediately once streaming
+has started.  The status of ongoing block streaming operations can be checked
+with query-block-jobs.  The operation can be stopped before it has completed
+using the block_job_cancel command.
+
+If a base file is specified then sectors are not copied from that base file and
+its backing chain.  When streaming completes the image file will have the base
+file as its backing file.  This can be used to stream a subset of the backing
+file chain instead of flattening the entire image.
+
+On successful completion the image file is updated to drop the backing file.
+
+Arguments:
+
+- device: device name (json-string)
+- base:   common backing file (json-string, optional)
+
+Errors:
+
+DeviceInUse:    streaming is already active on this device
+DeviceNotFound: device name is invalid
+NotSupported:   image streaming is not supported by this device
+
+Events:
+
+On completion the BLOCK_JOB_COMPLETED event is raised with the following
+fields:
+
+- type:     job type ("stream" for image streaming, json-string)
+- device:   device name (json-string)
+- len:      maximum progress value (json-int)
+- offset:   current progress value (json-int)
+- speed:    rate limit, bytes per second (json-int)
+- error:    error message (json-string, only on error)
+
+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.
+
+On failure the error field contains a human-readable error message.  There are
+no semantics other than that streaming has failed and clients should not try
+to interpret the error string.
+
+Examples:
+
+-> { "execute": "block_stream", "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 487d560..15a6b7a 100644
--- a/trace-events
+++ b/trace-events
@@ -75,6 +75,10 @@ bdrv_co_copy_on_readv(void *bs, int64_t sector_num, int 
nb_sectors, int64_t clus
 stream_one_iteration(void *s, int64_t sector_num, int max_sectors) "s %p 
sector_num %"PRId64" max_sectors %d"
 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_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"
+
 # hw/virtio-blk.c
 virtio_blk_req_complete(void *req, int status) "req %p status %d"
 virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
-- 
1.7.7