[Qemu-devel] [PATCH v3 5/9] qmp: add block_stream command

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

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 <stefanha@linux.vnet.ibm.com>
---
 blockdev.c       |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 hmp-commands.hx  |   13 ++++++++++
 hmp.c            |   14 +++++++++++
 hmp.h            |    1 +
 monitor.c        |    3 ++
 monitor.h        |    1 +
 qapi-schema.json |   53 ++++++++++++++++++++++++++++++++++++++++++
 qerror.c         |    4 +++
 qerror.h         |    3 ++
 qmp-commands.hx  |   18 ++++++++++++++
 trace-events     |    4 +++
 11 files changed, 182 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index dbf0251..08355cf 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -13,8 +13,11 @@
 #include "qerror.h"
 #include "qemu-option.h"
 #include "qemu-config.h"
+#include "qemu-objects.h"
 #include "sysemu.h"
 #include "block_int.h"
+#include "qmp-commands.h"
+#include "trace.h"
 
 static QTAILQ_HEAD(drivelist, DriveInfo) drives = QTAILQ_HEAD_INITIALIZER(drives);
 
@@ -887,3 +890,68 @@ 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);
+}
+
+void qmp_block_stream(const char *device, bool has_base,
+                      const char *base, Error **errp)
+{
+    BlockDriverState *bs;
+    int ret;
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+
+    /* Base device not supported */
+    if (base) {
+        error_set(errp, QERR_NOT_SUPPORTED);
+        return;
+    }
+
+    ret = stream_start(bs, NULL, block_stream_cb, bs);
+    if (ret < 0) {
+        switch (ret) {
+        case -EBUSY:
+            error_set(errp, QERR_DEVICE_IN_USE, device);
+            return;
+        default:
+            error_set(errp, QERR_NOT_SUPPORTED);
+            return;
+        }
+    }
+
+    trace_qmp_block_stream(bs, bs->job);
+}
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 79a9195..c0de41c 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -70,6 +70,19 @@ 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",
+        .mhandler.cmd = hmp_block_stream,
+    },
+
+STEXI
+@item block_stream
+@findex block_stream
+Copy data from a backing file into a block device.
+ETEXI
 
     {
         .name       = "eject",
diff --git a/hmp.c b/hmp.c
index dfab7ad..8b7d7d4 100644
--- a/hmp.c
+++ b/hmp.c
@@ -531,3 +531,17 @@ void hmp_cpu(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "invalid CPU index\n");
     }
 }
+
+void hmp_block_stream(Monitor *mon, const QDict *qdict)
+{
+    Error *error = NULL;
+    const char *device = qdict_get_str(qdict, "device");
+    const char *base = qdict_get_try_str(qdict, "base");
+
+    qmp_block_stream(device, base != NULL, base, &error);
+
+    if (error) {
+        monitor_printf(mon, "%s\n", error_get_pretty(error));
+        error_free(error);
+    }
+}
diff --git a/hmp.h b/hmp.h
index 4422578..3cb6fe5 100644
--- a/hmp.h
+++ b/hmp.h
@@ -37,5 +37,6 @@ void hmp_stop(Monitor *mon, const QDict *qdict);
 void hmp_system_reset(Monitor *mon, const QDict *qdict);
 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);
 
 #endif
diff --git a/monitor.c b/monitor.c
index 1be222e..a33218c 100644
--- a/monitor.c
+++ b/monitor.c
@@ -479,6 +479,9 @@ 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 e76795f..d9b07dc 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/qapi-schema.json b/qapi-schema.json
index fbbdbe0..65308d2 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -901,3 +901,56 @@
 # Notes: Do not use this command.
 ##
 { 'command': 'cpu', 'data': {'index': 'int'} }
+
+##
+# @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
+# @base:   common backing file
+#
+# 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.
+#
+# Since: 1.1
+##
+{ 'command': 'block_stream', 'data': { 'device': 'str', '*base': 'str' } }
diff --git a/qerror.c b/qerror.c
index 14a1d59..605381a 100644
--- a/qerror.c
+++ b/qerror.c
@@ -174,6 +174,10 @@ 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 560d458..b5c0cfe 100644
--- a/qerror.h
+++ b/qerror.h
@@ -147,6 +147,9 @@ 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 94da2a8..8c1c934 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -683,6 +683,24 @@ Example:
 EQMP
 
     {
+        .name       = "block_stream",
+        .args_type  = "device:B,base:s?",
+        .mhandler.cmd_new = qmp_marshal_input_block_stream,
+    },
+
+SQMP
+block_stream
+------------
+See qapi-schema.json for documentation.
+
+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 4efcd95..6c1eec2 100644
--- a/trace-events
+++ b/trace-events
@@ -73,6 +73,10 @@ 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 nb_sectors, int is_allocated) "s %p sector_num %"PRId64" nb_sectors %d is_allocated %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"
+qmp_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"
-- 
1.7.7.3