commit: Set commit_top_bs->total_sectors

Like in the mirror filter driver, we also need to set the image size for
the commit filter driver. This is less likely to be a problem in
practice than for the mirror because we're not at the active layer here,
but attaching new parents to a node in the middle of the chain is
possible, so the size needs to be correct anyway.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>

block/commit.c

@@ -335,6 +335,7 @@ void commit_start(const char *job_id, BlockDriverState *bs,
     if (commit_top_bs == NULL) {
         goto fail;
     }
+    commit_top_bs->total_sectors = top->total_sectors;
     bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(top));
 
     bdrv_set_backing_hd(commit_top_bs, top, &local_err);