btr: Simplify btr_node_status().
authorAndre Noll <maan@systemlinux.org>
Sat, 30 Mar 2013 21:30:54 +0000 (21:30 +0000)
committerAndre Noll <maan@systemlinux.org>
Sun, 29 Sep 2013 11:00:37 +0000 (13:00 +0200)
This changes btr_node_status() to check for errors before looking
at queue sizes. In certain cases this avoids to call the possibly
expensive btr_get_output_queue_size().

If no more input is going to arrive for an internal node whose output
queue is full, btr_node_status() now returns EOF immediately, which
is better than the previous scheme where we waited for the output
queue to become empty before returning EOF.

buffer_tree.c

index 84dc933..56ab2b2 100644 (file)
@@ -1203,21 +1203,20 @@ int btr_node_status(struct btr_node *btrn, size_t min_iqs,
        size_t iqs;
 
        assert(btrn);
-       if (type != BTR_NT_LEAF) {
-               if (btr_no_children(btrn))
-                       return -E_BTR_NO_CHILD;
-               if (btr_get_output_queue_size(btrn) > BTRN_MAX_PENDING)
-                       return 0;
-       }
-       if (type != BTR_NT_ROOT) {
-               if (btr_eof(btrn))
-                       return -E_BTR_EOF;
-               iqs = btr_get_input_queue_size(btrn);
-               if (iqs == 0) /* we have a parent, because not eof */
-                       return 0;
-               if (iqs < min_iqs && !btr_no_parent(btrn))
-                       return 0;
-       }
+       if (type != BTR_NT_LEAF && btr_no_children(btrn))
+               return -E_BTR_NO_CHILD;
+       if (type != BTR_NT_ROOT && btr_eof(btrn))
+               return -E_BTR_EOF;
+
+       if (btr_get_output_queue_size(btrn) > BTRN_MAX_PENDING)
+               return 0;
+       if (type == BTR_NT_ROOT)
+               return 1;
+       iqs = btr_get_input_queue_size(btrn);
+       if (iqs == 0) /* we have a parent, because not eof */
+               return 0;
+       if (iqs < min_iqs && !btr_no_parent(btrn))
+               return 0;
        return 1;
 }