diff options
Diffstat (limited to 'drivers/md/persistent-data/dm-btree-remove.c')
| -rw-r--r-- | drivers/md/persistent-data/dm-btree-remove.c | 174 |
1 files changed, 99 insertions, 75 deletions
diff --git a/drivers/md/persistent-data/dm-btree-remove.c b/drivers/md/persistent-data/dm-btree-remove.c index 023fbc2d389e..1a35caf2563d 100644 --- a/drivers/md/persistent-data/dm-btree-remove.c +++ b/drivers/md/persistent-data/dm-btree-remove.c @@ -128,18 +128,9 @@ static void delete_at(struct node *n, unsigned index) n->header.nr_entries = cpu_to_le32(nr_entries - 1); } -static unsigned del_threshold(struct node *n) -{ - return le32_to_cpu(n->header.max_entries) / 3; -} - static unsigned merge_threshold(struct node *n) { - /* - * The extra one is because we know we're potentially going to - * delete an entry. - */ - return 2 * (le32_to_cpu(n->header.max_entries) / 3) + 1; + return le32_to_cpu(n->header.max_entries) / 3; } struct child { @@ -188,6 +179,15 @@ static int exit_child(struct dm_btree_info *info, struct child *c) static void shift(struct node *left, struct node *right, int count) { + uint32_t nr_left = le32_to_cpu(left->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); + uint32_t r_max_entries = le32_to_cpu(right->header.max_entries); + + BUG_ON(max_entries != r_max_entries); + BUG_ON(nr_left - count > max_entries); + BUG_ON(nr_right + count > max_entries); + if (!count) return; @@ -199,13 +199,8 @@ static void shift(struct node *left, struct node *right, int count) node_shift(right, count); } - left->header.nr_entries = - cpu_to_le32(le32_to_cpu(left->header.nr_entries) - count); - BUG_ON(le32_to_cpu(left->header.nr_entries) > le32_to_cpu(left->header.max_entries)); - - right->header.nr_entries = - cpu_to_le32(le32_to_cpu(right->header.nr_entries) + count); - BUG_ON(le32_to_cpu(right->header.nr_entries) > le32_to_cpu(right->header.max_entries)); + left->header.nr_entries = cpu_to_le32(nr_left - count); + right->header.nr_entries = cpu_to_le32(nr_right + count); } static void __rebalance2(struct dm_btree_info *info, struct node *parent, @@ -215,8 +210,9 @@ static void __rebalance2(struct dm_btree_info *info, struct node *parent, struct node *right = r->n; uint32_t nr_left = le32_to_cpu(left->header.nr_entries); uint32_t nr_right = le32_to_cpu(right->header.nr_entries); + unsigned threshold = 2 * merge_threshold(left) + 1; - if (nr_left + nr_right <= merge_threshold(left)) { + if (nr_left + nr_right < threshold) { /* * Merge */ @@ -234,9 +230,6 @@ static void __rebalance2(struct dm_btree_info *info, struct node *parent, * Rebalance. */ unsigned target_left = (nr_left + nr_right) / 2; - unsigned shift_ = nr_left - target_left; - BUG_ON(le32_to_cpu(left->header.max_entries) <= nr_left - shift_); - BUG_ON(le32_to_cpu(right->header.max_entries) <= nr_right + shift_); shift(left, right, nr_left - target_left); *key_ptr(parent, r->index) = right->keys[0]; } @@ -272,6 +265,84 @@ 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) +{ + int s; + 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); + + if (nr_left < nr_right) { + s = nr_left - target; + + if (s < 0 && nr_center < -s) { + /* not enough in central node */ + shift(left, center, nr_center); + s = nr_center - target; + shift(left, right, s); + nr_right += s; + } else + shift(left, center, s); + + shift(center, right, target - nr_right); + + } else { + s = target - nr_right; + if (s > 0 && nr_center < s) { + /* not enough in central node */ + shift(center, right, nr_center); + s = target - nr_center; + shift(left, right, s); + nr_left -= s; + } else + shift(center, right, s); + + shift(left, center, nr_left - target); + } + + *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) { @@ -282,62 +353,18 @@ 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; + unsigned threshold = merge_threshold(left) * 4 + 1; 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) < threshold) + 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, @@ -441,9 +468,6 @@ static int rebalance_children(struct shadow_spine *s, if (r) return r; - if (child_entries > del_threshold(n)) - return 0; - has_left_sibling = i > 0; has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1); |