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Commit 709c0486 authored by Arne Jansen's avatar Arne Jansen Committed by Jan Schmidt
Browse files

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



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.
This code is only effective when SCRAMBLE_DELAYED_REFS is defined.

Signed-off-by: default avatarArne Jansen <sensille@gmx.net>
parent 416ac51d

fs/btrfs/extent-tree.c

+49 −0
Original line number Original line Diff line number Diff line
@@ -34,6 +34,8 @@ 
#include "locking.h"

#include "locking.h"

#include "free-space-cache.h"

#include "free-space-cache.h"





#undef SCRAMBLE_DELAYED_REFS



/*

/*

 * control flags for do_chunk_alloc's force field

 * control flags for do_chunk_alloc's force field

 * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk

 * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk
@@ -2364,6 +2366,49 @@ static void wait_for_more_refs(struct btrfs_fs_info *fs_info, 
	spin_lock(&delayed_refs->lock);

	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

 * this starts processing the delayed reference count updates and

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

 * extent insertions we have queued up so far.  count can be
@@ -2406,6 +2451,10 @@ again: 
	consider_waiting = 0;

	consider_waiting = 0;

	spin_lock(&delayed_refs->lock);

	spin_lock(&delayed_refs->lock);





#ifdef SCRAMBLE_DELAYED_REFS

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

#endif



	if (count == 0) {

	if (count == 0) {

		count = delayed_refs->num_entries * 2;

		count = delayed_refs->num_entries * 2;

		run_most = 1;

		run_most = 1;