block: Connect BlockBackend to BlockDriverState

Convenience function blk_new_with_bs() creates a BlockBackend with its
BlockDriverState.  Callers have to unref both.  The commit after next
will relieve them of the need to unref the BlockDriverState.

Complication: due to the silly way drive_del works, we need a way to
hide a BlockBackend, just like bdrv_make_anon().  To emphasize its
"special" status, give the function a suitably off-putting name:
blk_hide_on_behalf_of_do_drive_del().  Unfortunately, hiding turns the
BlockBackend's name into the empty string.  Can't avoid that without
breaking the blk->bs->device_name equals blk->name invariant.

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

1 files changed, 2 insertions, 6 deletions

diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 265cf13..0022083 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -860,15 +860,11 @@ static int blk_connect(struct XenDevice *xendev)
 
         /* setup via xenbus -> create new block driver instance */
         xen_be_printf(&blkdev->xendev, 2, "create new bdrv (xenbus setup)\n");
-        blk = blk_new(blkdev->dev, NULL);
+        blk = blk_new_with_bs(blkdev->dev, NULL);
         if (!blk) {
             return -1;
         }
-        blkdev->bs = bdrv_new_root(blkdev->dev, NULL);
-        if (!blkdev->bs) {
-            blk_unref(blk);
-            return -1;
-        }
+        blkdev->bs = blk_bs(blk);
 
         drv = bdrv_find_whitelisted_format(blkdev->fileproto, readonly);
         if (bdrv_open(&blkdev->bs, blkdev->filename, NULL, NULL, qflags,