block: Make BlockBackend own its BlockDriverState

On BlockBackend destruction, unref its BlockDriverState.  Replaces the
callers' unrefs.

This turns the pointer from BlockBackend to BlockDriverState into a
strong reference, managed with bdrv_ref() / bdrv_unref().  The
back-pointer remains weak.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/qemu-nbd.c b/qemu-nbd.c
index f741973687..5cd6c6d187 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -775,7 +775,6 @@ int main(int argc, char **argv)
         }
     } while (state != TERMINATED);
 
-    bdrv_unref(bs);
     blk_unref(blk);
     if (sockpath) {
         unlink(sockpath);