mirror: Add filter-node-name to blockdev-mirror

Management tools need to be able to know about every node in the graph
and need a way to address them. Changing the graph structure was okay
because libvirt doesn't really manage the node level yet, but future
libvirt versions need to deal with both new and old version of qemu.

This new option to blockdev-mirror allows the client to set a node-name
for the automatically inserted filter driver, and at the same time
serves as a witness for a future libvirt that this version of qemu does
automatically insert a filter driver.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Acked-by: Fam Zheng <famz@redhat.com>

block/mirror.c

@@ -1088,7 +1088,7 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs,
                              void *opaque, Error **errp,
                              const BlockJobDriver *driver,
                              bool is_none_mode, BlockDriverState *base,
-                             bool auto_complete)
+                             bool auto_complete, const char *filter_node_name)
 {
     MirrorBlockJob *s;
     BlockDriverState *mirror_top_bs;
@@ -1114,8 +1114,8 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs,
     /* In the case of active commit, add dummy driver to provide consistent
      * reads on the top, while disabling it in the intermediate nodes, and make
      * the backing chain writable. */
-    mirror_top_bs = bdrv_new_open_driver(&bdrv_mirror_top, NULL, BDRV_O_RDWR,
-                                         errp);
+    mirror_top_bs = bdrv_new_open_driver(&bdrv_mirror_top, filter_node_name,
+                                         BDRV_O_RDWR, errp);
     if (mirror_top_bs == NULL) {
         return;
     }
@@ -1225,7 +1225,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
                   MirrorSyncMode mode, BlockMirrorBackingMode backing_mode,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
-                  bool unmap, Error **errp)
+                  bool unmap, const char *filter_node_name, Error **errp)
 {
     bool is_none_mode;
     BlockDriverState *base;
@@ -1239,7 +1239,8 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
     mirror_start_job(job_id, bs, BLOCK_JOB_DEFAULT, target, replaces,
                      speed, granularity, buf_size, backing_mode,
                      on_source_error, on_target_error, unmap, NULL, NULL, errp,
-                     &mirror_job_driver, is_none_mode, base, false);
+                     &mirror_job_driver, is_none_mode, base, false,
+                     filter_node_name);
 }
 
 void commit_active_start(const char *job_id, BlockDriverState *bs,
@@ -1260,7 +1261,8 @@ void commit_active_start(const char *job_id, BlockDriverState *bs,
     mirror_start_job(job_id, bs, creation_flags, base, NULL, speed, 0, 0,
                      MIRROR_LEAVE_BACKING_CHAIN,
                      on_error, on_error, true, cb, opaque, &local_err,
-                     &commit_active_job_driver, false, base, auto_complete);
+                     &commit_active_job_driver, false, base, auto_complete,
+                     NULL);
     if (local_err) {
         error_propagate(errp, local_err);
         goto error_restore_flags;

blockdev.c

@@ -3366,6 +3366,8 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
                                    bool has_on_target_error,
                                    BlockdevOnError on_target_error,
                                    bool has_unmap, bool unmap,
+                                   bool has_filter_node_name,
+                                   const char *filter_node_name,
                                    Error **errp)
 {
 
@@ -3387,6 +3389,9 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
     if (!has_unmap) {
         unmap = true;
     }
+    if (!has_filter_node_name) {
+        filter_node_name = NULL;
+    }
 
     if (granularity != 0 && (granularity < 512 || granularity > 1048576 * 64)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "granularity",
@@ -3416,7 +3421,8 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
     mirror_start(job_id, bs, target,
                  has_replaces ? replaces : NULL,
                  speed, granularity, buf_size, sync, backing_mode,
-                 on_source_error, on_target_error, unmap, errp);
+                 on_source_error, on_target_error, unmap, filter_node_name,
+                 errp);
 }
 
 void qmp_drive_mirror(DriveMirror *arg, Error **errp)
@@ -3554,6 +3560,7 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
                            arg->has_on_source_error, arg->on_source_error,
                            arg->has_on_target_error, arg->on_target_error,
                            arg->has_unmap, arg->unmap,
+                           false, NULL,
                            &local_err);
     bdrv_unref(target_bs);
     error_propagate(errp, local_err);
@@ -3572,6 +3579,8 @@ void qmp_blockdev_mirror(bool has_job_id, const char *job_id,
                          BlockdevOnError on_source_error,
                          bool has_on_target_error,
                          BlockdevOnError on_target_error,
+                         bool has_filter_node_name,
+                         const char *filter_node_name,
                          Error **errp)
 {
     BlockDriverState *bs;
@@ -3603,6 +3612,7 @@ void qmp_blockdev_mirror(bool has_job_id, const char *job_id,
                            has_on_source_error, on_source_error,
                            has_on_target_error, on_target_error,
                            true, true,
+                           has_filter_node_name, filter_node_name,
                            &local_err);
     error_propagate(errp, local_err);
 

include/block/block_int.h

@@ -824,6 +824,9 @@ void commit_active_start(const char *job_id, BlockDriverState *bs,
  * @on_source_error: The action to take upon error reading from the source.
  * @on_target_error: The action to take upon error writing to the target.
  * @unmap: Whether to unmap target where source sectors only contain zeroes.
+ * @filter_node_name: The node name that should be assigned to the filter
+ * driver that the mirror job inserts into the graph above @bs. NULL means that
+ * a node name should be autogenerated.
  * @errp: Error object.
  *
  * Start a mirroring operation on @bs.  Clusters that are allocated
@@ -837,7 +840,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
                   MirrorSyncMode mode, BlockMirrorBackingMode backing_mode,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
-                  bool unmap, Error **errp);
+                  bool unmap, const char *filter_node_name, Error **errp);
 
 /*
  * backup_job_create:

qapi/block-core.json

@@ -1671,6 +1671,11 @@
 #                   default 'report' (no limitations, since this applies to
 #                   a different block device than @device).
 #
+# @filter-node-name: #optional the node name that should be assigned to the
+#                    filter driver that the mirror job inserts into the graph
+#                    above @device. If this option is not given, a node name is
+#                    autogenerated. (Since: 2.9)
+#
 # Returns: nothing on success.
 #
 # Since: 2.6
@@ -1690,7 +1695,8 @@
             'sync': 'MirrorSyncMode',
             '*speed': 'int', '*granularity': 'uint32',
             '*buf-size': 'int', '*on-source-error': 'BlockdevOnError',
-            '*on-target-error': 'BlockdevOnError' } }
+            '*on-target-error': 'BlockdevOnError',
+            '*filter-node-name': 'str' } }
 
 ##
 # @block_set_io_throttle: