[PATCH v8 27/43] block: Use child access functions for QAPI queries

[Max Reitz <mreitz@redhat.com>]

query-block, query-named-block-nodes, and query-blockstats now return
any filtered child under "backing", not just bs->backing or COW
children.  This is so that filters do not interrupt the reported backing
chain.  This changes the output for iotest 184, as the throttled node
now appears as a backing child.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qapi.c               | 33 ++++++++++++++++++++-------------
 tests/qemu-iotests/184.out |  8 +++++++-
 2 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/block/qapi.c b/block/qapi.c
index c57b42d86d..2628323b63 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -163,9 +163,13 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk,
             break;
         }
 
-        if (bs0->drv && bs0->backing) {
+        if (bs0->drv && bdrv_filter_or_cow_child(bs0)) {
+            /*
+             * Put any filtered child here (for backwards compatibility to when
+             * we put bs0->backing here, which might be any filtered child).
+             */
             info->backing_file_depth++;
-            bs0 = bs0->backing->bs;
+            bs0 = bdrv_filter_or_cow_bs(bs0);
             (*p_image_info)->has_backing_image = true;
             p_image_info = &((*p_image_info)->backing_image);
         } else {
@@ -174,9 +178,8 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk,
 
         /* Skip automatically inserted nodes that the user isn't aware of for
          * query-block (blk != NULL), but not for query-named-block-nodes */
-        while (blk && bs0->drv && bs0->implicit) {
-            bs0 = backing_bs(bs0);
-            assert(bs0);
+        if (blk) {
+            bs0 = bdrv_skip_implicit_filters(bs0);
         }
     }
 
@@ -362,9 +365,7 @@ static void bdrv_query_info(BlockBackend *blk, BlockInfo **p_info,
     char *qdev;
 
     /* Skip automatically inserted nodes that the user isn't aware of */
-    while (bs && bs->drv && bs->implicit) {
-        bs = backing_bs(bs);
-    }
+    bs = bdrv_skip_implicit_filters(bs);
 
     info->device = g_strdup(blk_name(blk));
     info->type = g_strdup("unknown");
@@ -527,6 +528,7 @@ static BlockStats *bdrv_query_bds_stats(BlockDriverState *bs,
                                         bool blk_level)
 {
     BdrvChild *parent_child;
+    BlockDriverState *filter_or_cow_bs;
     BlockStats *s = NULL;
 
     s = g_malloc0(sizeof(*s));
@@ -539,9 +541,8 @@ static BlockStats *bdrv_query_bds_stats(BlockDriverState *bs,
     /* Skip automatically inserted nodes that the user isn't aware of in
      * a BlockBackend-level command. Stay at the exact node for a node-level
      * command. */
-    while (blk_level && bs->drv && bs->implicit) {
-        bs = backing_bs(bs);
-        assert(bs);
+    if (blk_level) {
+        bs = bdrv_skip_implicit_filters(bs);
     }
 
     if (bdrv_get_node_name(bs)[0]) {
@@ -587,9 +588,15 @@ static BlockStats *bdrv_query_bds_stats(BlockDriverState *bs,
         s->parent = bdrv_query_bds_stats(parent_child->bs, blk_level);
     }
 
-    if (blk_level && bs->backing) {
+    filter_or_cow_bs = bdrv_filter_or_cow_bs(bs);
+    if (blk_level && filter_or_cow_bs) {
+        /*
+         * Put any filtered or COW child here (for backwards
+         * compatibility to when we put bs0->backing here, which might
+         * be either)
+         */
         s->has_backing = true;
-        s->backing = bdrv_query_bds_stats(bs->backing->bs, blk_level);
+        s->backing = bdrv_query_bds_stats(filter_or_cow_bs, blk_level);
     }
 
     return s;
diff --git a/tests/qemu-iotests/184.out b/tests/qemu-iotests/184.out
index dec4017ad5..87c73070e3 100644
--- a/tests/qemu-iotests/184.out
+++ b/tests/qemu-iotests/184.out
@@ -27,6 +27,12 @@ Testing:
             "iops_rd": 0,
             "detect_zeroes": "off",
             "image": {
+                "backing-image": {
+                    "virtual-size": 1073741824,
+                    "filename": "null-co://",
+                    "format": "null-co",
+                    "actual-size": 0
+                },
                 "virtual-size": 1073741824,
                 "filename": "json:{\"throttle-group\": \"group0\", \"driver\": \"throttle\", \"file\": {\"driver\": \"null-co\"}}",
                 "format": "throttle",
@@ -35,7 +41,7 @@ Testing:
             "iops_wr": 0,
             "ro": false,
             "node-name": "throttle0",
-            "backing_file_depth": 0,
+            "backing_file_depth": 1,
             "drv": "throttle",
             "iops": 0,
             "bps_wr": 0,
-- 
2.26.2