fix block readahead in btrfs_next_leaf

Send the correct slot down to reada_for_search

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 7cf43da..51eea5c 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2120,7 +2120,7 @@
 		if (!level)
 			break;
 		if (path->reada)
-			reada_for_search(root, path, level, slot);
+			reada_for_search(root, path, level, 0);
 		next = read_tree_block(root,
 		       btrfs_node_blockptr(btrfs_buffer_node(next), 0));
 	}