Btrfs: Test code to change the order of delayed-ref processing

#include "locking.h"

#include "free-space-cache.h"

#undef SCRAMBLE_DELAYED_REFS

/*

 * control flags for do_chunk_alloc's force field

 * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk

	spin_lock(&delayed_refs->lock);

}

#ifdef SCRAMBLE_DELAYED_REFS

/*

 * Normally delayed refs get processed in ascending bytenr order. This

 * correlates in most cases to the order added. To expose dependencies on this

 * order, we start to process the tree in the middle instead of the beginning

 */

static u64 find_middle(struct rb_root *root)

{

	struct rb_node *n = root->rb_node;

	struct btrfs_delayed_ref_node *entry;

	int alt = 1;

	u64 middle;

	u64 first = 0, last = 0;

	n = rb_first(root);

	if (n) {

		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);

		first = entry->bytenr;

	}

	n = rb_last(root);

	if (n) {

		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);

		last = entry->bytenr;

	}

	n = root->rb_node;

	while (n) {

		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);

		WARN_ON(!entry->in_tree);

		middle = entry->bytenr;

		if (alt)

			n = n->rb_left;

		else

			n = n->rb_right;

		alt = 1 - alt;

	}

	return middle;

}

#endif

/*

 * this starts processing the delayed reference count updates and

 * extent insertions we have queued up so far.  count can be

	consider_waiting = 0;

	spin_lock(&delayed_refs->lock);

#ifdef SCRAMBLE_DELAYED_REFS

	delayed_refs->run_delayed_start = find_middle(&delayed_refs->root);

#endif

	if (count == 0) {

		count = delayed_refs->num_entries * 2;

		run_most = 1;