block: Add BdrvChildRole.get_parent_desc()

For meaningful error messages in the permission system, we need to get
some human-readable description of the parent of a BdrvChild.

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

1 files changed, 21 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index fcc42b591e..38a3858e96 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -80,6 +80,7 @@ static const AIOCBInfo block_backend_aiocb_info = {
 
 static void drive_info_del(DriveInfo *dinfo);
 static BlockBackend *bdrv_first_blk(BlockDriverState *bs);
+static char *blk_get_attached_dev_id(BlockBackend *blk);
 
 /* All BlockBackends */
 static QTAILQ_HEAD(, BlockBackend) block_backends =
@@ -102,6 +103,25 @@ static void blk_root_drained_end(BdrvChild *child);
 static void blk_root_change_media(BdrvChild *child, bool load);
 static void blk_root_resize(BdrvChild *child);
 
+static char *blk_root_get_parent_desc(BdrvChild *child)
+{
+    BlockBackend *blk = child->opaque;
+    char *dev_id;
+
+    if (blk->name) {
+        return g_strdup(blk->name);
+    }
+
+    dev_id = blk_get_attached_dev_id(blk);
+    if (*dev_id) {
+        return dev_id;
+    } else {
+        /* TODO Callback into the BB owner for something more detailed */
+        g_free(dev_id);
+        return g_strdup("a block device");
+    }
+}
+
 static const char *blk_root_get_name(BdrvChild *child)
 {
     return blk_name(child->opaque);
@@ -113,6 +133,7 @@ static const BdrvChildRole child_root = {
     .change_media       = blk_root_change_media,
     .resize             = blk_root_resize,
     .get_name           = blk_root_get_name,
+    .get_parent_desc    = blk_root_get_parent_desc,
 
     .drained_begin      = blk_root_drained_begin,
     .drained_end        = blk_root_drained_end,