block: Add blk_make_empty()

Two callers of BlockDriver.bdrv_make_empty() remain that should not call
this method directly.  Both do not have access to a BdrvChild, but they
can use a BlockBackend, so we add this function that lets them use it.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200429141126.85159-4-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index f4944861fa..47bd56244d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2402,3 +2402,13 @@ const BdrvChild *blk_root(BlockBackend *blk)
 {
     return blk->root;
 }
+
+int blk_make_empty(BlockBackend *blk, Error **errp)
+{
+    if (!blk_is_available(blk)) {
+        error_setg(errp, "No medium inserted");
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_make_empty(blk->root, errp);
+}