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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 01-24-2012, 10:50 AM
Joe Thornber
 
Default break up __rebalance3 function.

This function was getting too big. Two functions are factored out
delete_center_node() and redistribute3(). No functional changes.
---
drivers/md/persistent-data/dm-btree-remove.c | 109 +++++++++++++------------
1 files changed, 57 insertions(+), 52 deletions(-)

diff --git a/drivers/md/persistent-data/dm-btree-remove.c b/drivers/md/persistent-data/dm-btree-remove.c
index 8d6f958..9480fcc 100644
--- a/drivers/md/persistent-data/dm-btree-remove.c
+++ b/drivers/md/persistent-data/dm-btree-remove.c
@@ -269,6 +269,57 @@ static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info,
return exit_child(info, &right);
}

+/*
+ * We dump as many entries from center as possible into left, then the rest
+ * in right, then rebalance2. This wastes some cpu, but I want something
+ * simple atm.
+ */
+static void delete_center_node(struct dm_btree_info *info, struct node *parent,
+ struct child *l, struct child *c, struct child *r,
+ struct node *left, struct node *center, struct node *right,
+ uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
+{
+ uint32_t max_entries = le32_to_cpu(left->header.max_entries);
+ unsigned shift = min(max_entries - nr_left, nr_center);
+
+ BUG_ON(nr_left + shift > max_entries);
+ node_copy(left, center, -shift);
+ left->header.nr_entries = cpu_to_le32(nr_left + shift);
+
+ if (shift != nr_center) {
+ shift = nr_center - shift;
+ BUG_ON((nr_right + shift) >= max_entries);
+ node_shift(right, shift);
+ node_copy(center, right, shift);
+ right->header.nr_entries = cpu_to_le32(nr_right + shift);
+ }
+ *key_ptr(parent, r->index) = right->keys[0];
+
+ delete_at(parent, c->index);
+ r->index--;
+
+ dm_tm_dec(info->tm, dm_block_location(c->block));
+ __rebalance2(info, parent, l, r);
+}
+
+/*
+ * Redistributes entries among 3 sibling nodes.
+ */
+static void redistribute3(struct dm_btree_info *info, struct node *parent,
+ struct child *l, struct child *c, struct child *r,
+ struct node *left, struct node *center, struct node *right,
+ uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
+{
+ uint32_t max_entries = le32_to_cpu(left->header.max_entries);
+ unsigned target = (nr_left + nr_center + nr_right) / 3;
+ BUG_ON(target > max_entries);
+
+ shift(left, center, nr_left - target);
+ shift(center, right, target - nr_right);
+ *key_ptr(parent, c->index) = center->keys[0];
+ *key_ptr(parent, r->index) = right->keys[0];
+}
+
static void __rebalance3(struct dm_btree_info *info, struct node *parent,
struct child *l, struct child *c, struct child *r)
{
@@ -279,62 +330,16 @@ static void __rebalance3(struct dm_btree_info *info, struct node *parent,
uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
uint32_t nr_center = le32_to_cpu(center->header.nr_entries);
uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
- uint32_t max_entries = le32_to_cpu(left->header.max_entries);
-
- unsigned target;

BUG_ON(left->header.max_entries != center->header.max_entries);
BUG_ON(center->header.max_entries != right->header.max_entries);

- if (((nr_left + nr_center + nr_right) / 2) < merge_threshold(center)) {
- /*
- * Delete center node:
- *
- * We dump as many entries from center as possible into
- * left, then the rest in right, then rebalance2. This
- * wastes some cpu, but I want something simple atm.
- */
- unsigned shift = min(max_entries - nr_left, nr_center);
-
- BUG_ON(nr_left + shift > max_entries);
- node_copy(left, center, -shift);
- left->header.nr_entries = cpu_to_le32(nr_left + shift);
-
- if (shift != nr_center) {
- shift = nr_center - shift;
- BUG_ON((nr_right + shift) >= max_entries);
- node_shift(right, shift);
- node_copy(center, right, shift);
- right->header.nr_entries = cpu_to_le32(nr_right + shift);
- }
- *key_ptr(parent, r->index) = right->keys[0];
-
- delete_at(parent, c->index);
- r->index--;
-
- dm_tm_dec(info->tm, dm_block_location(c->block));
- __rebalance2(info, parent, l, r);
-
- return;
- }
-
- /*
- * Rebalance
- */
- target = (nr_left + nr_center + nr_right) / 3;
- BUG_ON(target > max_entries);
-
- /*
- * Adjust the left node
- */
- shift(left, center, nr_left - target);
-
- /*
- * Adjust the right node
- */
- shift(center, right, target - nr_right);
- *key_ptr(parent, c->index) = center->keys[0];
- *key_ptr(parent, r->index) = right->keys[0];
+ if (((nr_left + nr_center + nr_right) / 2) < merge_threshold(center))
+ delete_center_node(info, parent, l, c, r, left, center, right,
+ nr_left, nr_center, nr_right);
+ else
+ redistribute3(info, parent, l, c, r, left, center, right,
+ nr_left, nr_center, nr_right);
}

static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info,
--
1.7.5.4

--
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