[Qemu-devel] [PATCH v2 6/6] add mirroring to blockdev-transaction

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 blockdev.c       |   42 ++++++++++++++++++++++++++++++++----------
 qapi-schema.json |   19 ++++++++++++++++++-
 qmp-commands.hx  |   12 +++++++++++-
 3 files changed, 61 insertions(+), 12 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 8fcdf0e..f181c6f 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -733,6 +733,7 @@ void qmp_blockdev_transaction(BlockdevActionList *dev_list,
     int ret = 0;
     BlockdevActionList *dev_entry = dev_list;
     BlkTransactionStates *states;
+    char *new_source = NULL;
 
     QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionStates) snap_bdrv_states;
     QSIMPLEQ_INIT(&snap_bdrv_states);
@@ -744,12 +745,12 @@ void qmp_blockdev_transaction(BlockdevActionList *dev_list,
     while (NULL != dev_entry) {
         BlockdevAction *dev_info = NULL;
         BlockDriver *proto_drv;
-        BlockDriver *drv;
+        BlockDriver *target_drv;
+        BlockDriver *drv = NULL;
         int flags;
         const char *device;
         const char *format = "qcow2";
         const char *new_image_file = NULL;
-        bool do_snapshot;
 
         dev_info = dev_entry->value;
         dev_entry = dev_entry->next;
@@ -760,21 +761,40 @@ void qmp_blockdev_transaction(BlockdevActionList *dev_list,
         switch (dev_info->kind) {
         case BLOCKDEV_ACTION_KIND_SNAPSHOT:
             device = dev_info->snapshot->device;
-            do_snapshot = !dev_info->snapshot->has_reuse || !dev_info->snapshot->reuse;
+            if (!dev_info->snapshot->has_reuse || !dev_info->snapshot->reuse) {
+                new_image_file = dev_info->snapshot->snapshot_file;
+            }
             if (dev_info->snapshot->has_format) {
                 format = dev_info->snapshot->format;
             }
-            new_image_file = dev_info->snapshot->snapshot_file;
+            new_source = g_strdup(dev_info->snapshot->snapshot_file);
             break;
+
+        case BLOCKDEV_ACTION_KIND_MIRROR:
+            device = dev_info->mirror->device;
+            drv = bdrv_find_format("blkmirror");
+            if (!dev_info->mirror->has_reuse || !dev_info->mirror->reuse) {
+                new_image_file = dev_info->mirror->target;
+            }
+            if (dev_info->mirror->has_format) {
+                format = dev_info->mirror->format;
+            }
+            new_source = g_strdup_printf("blkmirror:%s:%s", format,
+                                         dev_info->mirror->target);
+            break;
+
         default:
             abort();
         }
 
-        drv = bdrv_find_format(format);
-        if (!drv) {
+        target_drv = bdrv_find_format(format);
+        if (!target_drv) {
             error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
             goto delete_and_fail;
         }
+        if (!drv) {
+            drv = target_drv;
+        }
 
         states->old_bs = bdrv_find(device);
         if (!states->old_bs) {
@@ -798,14 +817,14 @@ void qmp_blockdev_transaction(BlockdevActionList *dev_list,
 
         flags = states->old_bs->open_flags;
 
-        proto_drv = bdrv_find_protocol(new_image_file);
+        proto_drv = bdrv_find_protocol(new_source);
         if (!proto_drv) {
             error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
             goto delete_and_fail;
         }
 
         /* create new image w/backing file */
-        if (do_snapshot) {
+        if (new_image_file) {
             ret = bdrv_img_create(new_image_file, format,
                                   states->old_bs->filename,
                                   states->old_bs->drv->format_name,
@@ -818,12 +837,14 @@ void qmp_blockdev_transaction(BlockdevActionList *dev_list,
 
         /* We will manually add the backing_hd field to the bs later */
         states->new_bs = bdrv_new("");
-        ret = bdrv_open(states->new_bs, new_image_file,
+        ret = bdrv_open(states->new_bs, new_source,
                         flags | BDRV_O_NO_BACKING, drv);
         if (ret != 0) {
-            error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
+            error_set(errp, QERR_OPEN_FILE_FAILED, new_source);
             goto delete_and_fail;
         }
+        g_free(new_source);
+        new_source = NULL;
     }
 
 
@@ -851,6 +872,7 @@ exit:
     QSIMPLEQ_FOREACH(states, &snap_bdrv_states, entry) {
         g_free(states);
     }
+    g_free(new_source);
     return;
 }
 
diff --git a/qapi-schema.json b/qapi-schema.json
index 78df122..fd5973d 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1131,6 +1131,22 @@
             '*reuse': 'bool' } }
 
 ##
+# @BlockdevMirror
+#
+# @device:  the name of the device to start mirroring.
+#
+# @target: the image that will start receiving writes for @device. A new
+#          file will be created if @reuse is absent or false.
+#
+# @format: #optional the format of the target image, default is 'qcow2'.
+#
+# @reuse: #optional whether QEMU should create a new image.
+##
+{ 'type': 'BlockdevMirror',
+  'data': { 'device': 'str', 'target': 'str', '*format': 'str',
+            '*reuse': 'bool' } }
+
+##
 # @BlockdevAction
 #
 # A discriminated record of operations that can be performed with
@@ -1138,7 +1154,8 @@
 ##
 { 'union': 'BlockdevAction',
   'data': {
-       'snapshot': 'BlockdevSnapshot'
+       'snapshot': 'BlockdevSnapshot',
+       'mirror': 'BlockdevMirror',
    } }
 
 ##
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 817b689..50ac5a0 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -701,7 +701,11 @@ operation for now is snapshotting.  If there is any failure performing
 any of the operations, all snapshots for the group are abandoned, and
 the original disks pre-snapshot attempt are used.
 
+Mirrored writes keep the previous image file open, and start writing
+data also to the new file specified in the command.
+
 A list of dictionaries is accepted, that contains the actions to be performed.
+
 For snapshots this is the device, the file to use for the new snapshot,
 and the format.  The default format, if not specified, is qcow2.
 
@@ -716,7 +720,7 @@ Arguments:
 
 actions array:
     - "type": the operation to perform.  The only supported
-      value is "snapshot". (json-string)
+      values are "snapshot" and "mirror". (json-string)
     - "data": a dictionary.  The contents depend on the value
       of "type".  When "type" is "snapshot":
       - "device": device name to snapshot (json-string)
@@ -724,6 +728,12 @@ actions array:
       - "format": format of new image (json-string, optional)
       - "reuse": whether QEMU should look for an existing image file
         (json-bool, optional, default false)
+      When "type" is "mirror":
+      - "device": device name to snapshot (json-string)
+      - "target": name of destination image file (json-string)
+      - "format": format of new image (json-string, optional)
+      - "reuse": whether QEMU should look for an existing image file
+        (json-bool, optional, default false)
 
 Example:
 
-- 
1.7.7.6