| /* |
| * Copyright (C) 2011 Red Hat, Inc. |
| * |
| * This file is released under the GPL. |
| */ |
| |
| #include "dm-btree.h" |
| #include "dm-btree-internal.h" |
| #include "dm-transaction-manager.h" |
| |
| #include <linux/export.h> |
| |
| /* |
| * Removing an entry from a btree |
| * ============================== |
| * |
| * A very important constraint for our btree is that no node, except the |
| * root, may have fewer than a certain number of entries. |
| * (MIN_ENTRIES <= nr_entries <= MAX_ENTRIES). |
| * |
| * Ensuring this is complicated by the way we want to only ever hold the |
| * locks on 2 nodes concurrently, and only change nodes in a top to bottom |
| * fashion. |
| * |
| * Each node may have a left or right sibling. When decending the spine, |
| * if a node contains only MIN_ENTRIES then we try and increase this to at |
| * least MIN_ENTRIES + 1. We do this in the following ways: |
| * |
| * [A] No siblings => this can only happen if the node is the root, in which |
| * case we copy the childs contents over the root. |
| * |
| * [B] No left sibling |
| * ==> rebalance(node, right sibling) |
| * |
| * [C] No right sibling |
| * ==> rebalance(left sibling, node) |
| * |
| * [D] Both siblings, total_entries(left, node, right) <= DEL_THRESHOLD |
| * ==> delete node adding it's contents to left and right |
| * |
| * [E] Both siblings, total_entries(left, node, right) > DEL_THRESHOLD |
| * ==> rebalance(left, node, right) |
| * |
| * After these operations it's possible that the our original node no |
| * longer contains the desired sub tree. For this reason this rebalancing |
| * is performed on the children of the current node. This also avoids |
| * having a special case for the root. |
| * |
| * Once this rebalancing has occurred we can then step into the child node |
| * for internal nodes. Or delete the entry for leaf nodes. |
| */ |
| |
| /* |
| * Some little utilities for moving node data around. |
| */ |
| static void node_shift(struct btree_node *n, int shift) |
| { |
| uint32_t nr_entries = le32_to_cpu(n->header.nr_entries); |
| uint32_t value_size = le32_to_cpu(n->header.value_size); |
| |
| if (shift < 0) { |
| shift = -shift; |
| BUG_ON(shift > nr_entries); |
| BUG_ON((void *) key_ptr(n, shift) >= value_ptr(n, shift)); |
| memmove(key_ptr(n, 0), |
| key_ptr(n, shift), |
| (nr_entries - shift) * sizeof(__le64)); |
| memmove(value_ptr(n, 0), |
| value_ptr(n, shift), |
| (nr_entries - shift) * value_size); |
| } else { |
| BUG_ON(nr_entries + shift > le32_to_cpu(n->header.max_entries)); |
| memmove(key_ptr(n, shift), |
| key_ptr(n, 0), |
| nr_entries * sizeof(__le64)); |
| memmove(value_ptr(n, shift), |
| value_ptr(n, 0), |
| nr_entries * value_size); |
| } |
| } |
| |
| static void node_copy(struct btree_node *left, struct btree_node *right, int shift) |
| { |
| uint32_t nr_left = le32_to_cpu(left->header.nr_entries); |
| uint32_t value_size = le32_to_cpu(left->header.value_size); |
| BUG_ON(value_size != le32_to_cpu(right->header.value_size)); |
| |
| if (shift < 0) { |
| shift = -shift; |
| BUG_ON(nr_left + shift > le32_to_cpu(left->header.max_entries)); |
| memcpy(key_ptr(left, nr_left), |
| key_ptr(right, 0), |
| shift * sizeof(__le64)); |
| memcpy(value_ptr(left, nr_left), |
| value_ptr(right, 0), |
| shift * value_size); |
| } else { |
| BUG_ON(shift > le32_to_cpu(right->header.max_entries)); |
| memcpy(key_ptr(right, 0), |
| key_ptr(left, nr_left - shift), |
| shift * sizeof(__le64)); |
| memcpy(value_ptr(right, 0), |
| value_ptr(left, nr_left - shift), |
| shift * value_size); |
| } |
| } |
| |
| /* |
| * Delete a specific entry from a leaf node. |
| */ |
| static void delete_at(struct btree_node *n, unsigned index) |
| { |
| unsigned nr_entries = le32_to_cpu(n->header.nr_entries); |
| unsigned nr_to_copy = nr_entries - (index + 1); |
| uint32_t value_size = le32_to_cpu(n->header.value_size); |
| BUG_ON(index >= nr_entries); |
| |
| if (nr_to_copy) { |
| memmove(key_ptr(n, index), |
| key_ptr(n, index + 1), |
| nr_to_copy * sizeof(__le64)); |
| |
| memmove(value_ptr(n, index), |
| value_ptr(n, index + 1), |
| nr_to_copy * value_size); |
| } |
| |
| n->header.nr_entries = cpu_to_le32(nr_entries - 1); |
| } |
| |
| static unsigned merge_threshold(struct btree_node *n) |
| { |
| return le32_to_cpu(n->header.max_entries) / 3; |
| } |
| |
| struct child { |
| unsigned index; |
| struct dm_block *block; |
| struct btree_node *n; |
| }; |
| |
| static int init_child(struct dm_btree_info *info, struct dm_btree_value_type *vt, |
| struct btree_node *parent, |
| unsigned index, struct child *result) |
| { |
| int r, inc; |
| dm_block_t root; |
| |
| result->index = index; |
| root = value64(parent, index); |
| |
| r = dm_tm_shadow_block(info->tm, root, &btree_node_validator, |
| &result->block, &inc); |
| if (r) |
| return r; |
| |
| result->n = dm_block_data(result->block); |
| |
| if (inc) |
| inc_children(info->tm, result->n, vt); |
| |
| *((__le64 *) value_ptr(parent, index)) = |
| cpu_to_le64(dm_block_location(result->block)); |
| |
| return 0; |
| } |
| |
| static int exit_child(struct dm_btree_info *info, struct child *c) |
| { |
| return dm_tm_unlock(info->tm, c->block); |
| } |
| |
| static void shift(struct btree_node *left, struct btree_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; |
| |
| if (count > 0) { |
| node_shift(right, count); |
| node_copy(left, right, count); |
| } else { |
| node_copy(left, right, count); |
| node_shift(right, count); |
| } |
| |
| 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 btree_node *parent, |
| struct child *l, struct child *r) |
| { |
| struct btree_node *left = l->n; |
| struct btree_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 < threshold) { |
| /* |
| * Merge |
| */ |
| node_copy(left, right, -nr_right); |
| left->header.nr_entries = cpu_to_le32(nr_left + nr_right); |
| delete_at(parent, r->index); |
| |
| /* |
| * We need to decrement the right block, but not it's |
| * children, since they're still referenced by left. |
| */ |
| dm_tm_dec(info->tm, dm_block_location(r->block)); |
| } else { |
| /* |
| * Rebalance. |
| */ |
| unsigned target_left = (nr_left + nr_right) / 2; |
| shift(left, right, nr_left - target_left); |
| *key_ptr(parent, r->index) = right->keys[0]; |
| } |
| } |
| |
| static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info, |
| struct dm_btree_value_type *vt, unsigned left_index) |
| { |
| int r; |
| struct btree_node *parent; |
| struct child left, right; |
| |
| parent = dm_block_data(shadow_current(s)); |
| |
| r = init_child(info, vt, parent, left_index, &left); |
| if (r) |
| return r; |
| |
| r = init_child(info, vt, parent, left_index + 1, &right); |
| if (r) { |
| exit_child(info, &left); |
| return r; |
| } |
| |
| __rebalance2(info, parent, &left, &right); |
| |
| r = exit_child(info, &left); |
| if (r) { |
| exit_child(info, &right); |
| return r; |
| } |
| |
| 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 btree_node *parent, |
| struct child *l, struct child *c, struct child *r, |
| struct btree_node *left, struct btree_node *center, struct btree_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 btree_node *parent, |
| struct child *l, struct child *c, struct child *r, |
| struct btree_node *left, struct btree_node *center, struct btree_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; |
| 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 -= 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 btree_node *parent, |
| struct child *l, struct child *c, struct child *r) |
| { |
| struct btree_node *left = l->n; |
| struct btree_node *center = c->n; |
| struct btree_node *right = r->n; |
| |
| 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); |
| |
| 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) < 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, |
| struct dm_btree_value_type *vt, unsigned left_index) |
| { |
| int r; |
| struct btree_node *parent = dm_block_data(shadow_current(s)); |
| struct child left, center, right; |
| |
| /* |
| * FIXME: fill out an array? |
| */ |
| r = init_child(info, vt, parent, left_index, &left); |
| if (r) |
| return r; |
| |
| r = init_child(info, vt, parent, left_index + 1, ¢er); |
| if (r) { |
| exit_child(info, &left); |
| return r; |
| } |
| |
| r = init_child(info, vt, parent, left_index + 2, &right); |
| if (r) { |
| exit_child(info, &left); |
| exit_child(info, ¢er); |
| return r; |
| } |
| |
| __rebalance3(info, parent, &left, ¢er, &right); |
| |
| r = exit_child(info, &left); |
| if (r) { |
| exit_child(info, ¢er); |
| exit_child(info, &right); |
| return r; |
| } |
| |
| r = exit_child(info, ¢er); |
| if (r) { |
| exit_child(info, &right); |
| return r; |
| } |
| |
| r = exit_child(info, &right); |
| if (r) |
| return r; |
| |
| return 0; |
| } |
| |
| static int rebalance_children(struct shadow_spine *s, |
| struct dm_btree_info *info, |
| struct dm_btree_value_type *vt, uint64_t key) |
| { |
| int i, r, has_left_sibling, has_right_sibling; |
| struct btree_node *n; |
| |
| n = dm_block_data(shadow_current(s)); |
| |
| if (le32_to_cpu(n->header.nr_entries) == 1) { |
| struct dm_block *child; |
| dm_block_t b = value64(n, 0); |
| |
| r = dm_tm_read_lock(info->tm, b, &btree_node_validator, &child); |
| if (r) |
| return r; |
| |
| memcpy(n, dm_block_data(child), |
| dm_bm_block_size(dm_tm_get_bm(info->tm))); |
| r = dm_tm_unlock(info->tm, child); |
| if (r) |
| return r; |
| |
| dm_tm_dec(info->tm, dm_block_location(child)); |
| return 0; |
| } |
| |
| i = lower_bound(n, key); |
| if (i < 0) |
| return -ENODATA; |
| |
| has_left_sibling = i > 0; |
| has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1); |
| |
| if (!has_left_sibling) |
| r = rebalance2(s, info, vt, i); |
| |
| else if (!has_right_sibling) |
| r = rebalance2(s, info, vt, i - 1); |
| |
| else |
| r = rebalance3(s, info, vt, i - 1); |
| |
| return r; |
| } |
| |
| static int do_leaf(struct btree_node *n, uint64_t key, unsigned *index) |
| { |
| int i = lower_bound(n, key); |
| |
| if ((i < 0) || |
| (i >= le32_to_cpu(n->header.nr_entries)) || |
| (le64_to_cpu(n->keys[i]) != key)) |
| return -ENODATA; |
| |
| *index = i; |
| |
| return 0; |
| } |
| |
| /* |
| * Prepares for removal from one level of the hierarchy. The caller must |
| * call delete_at() to remove the entry at index. |
| */ |
| static int remove_raw(struct shadow_spine *s, struct dm_btree_info *info, |
| struct dm_btree_value_type *vt, dm_block_t root, |
| uint64_t key, unsigned *index) |
| { |
| int i = *index, r; |
| struct btree_node *n; |
| |
| for (;;) { |
| r = shadow_step(s, root, vt); |
| if (r < 0) |
| break; |
| |
| /* |
| * We have to patch up the parent node, ugly, but I don't |
| * see a way to do this automatically as part of the spine |
| * op. |
| */ |
| if (shadow_has_parent(s)) { |
| __le64 location = cpu_to_le64(dm_block_location(shadow_current(s))); |
| memcpy(value_ptr(dm_block_data(shadow_parent(s)), i), |
| &location, sizeof(__le64)); |
| } |
| |
| n = dm_block_data(shadow_current(s)); |
| |
| if (le32_to_cpu(n->header.flags) & LEAF_NODE) |
| return do_leaf(n, key, index); |
| |
| r = rebalance_children(s, info, vt, key); |
| if (r) |
| break; |
| |
| n = dm_block_data(shadow_current(s)); |
| if (le32_to_cpu(n->header.flags) & LEAF_NODE) |
| return do_leaf(n, key, index); |
| |
| i = lower_bound(n, key); |
| |
| /* |
| * We know the key is present, or else |
| * rebalance_children would have returned |
| * -ENODATA |
| */ |
| root = value64(n, i); |
| } |
| |
| return r; |
| } |
| |
| int dm_btree_remove(struct dm_btree_info *info, dm_block_t root, |
| uint64_t *keys, dm_block_t *new_root) |
| { |
| unsigned level, last_level = info->levels - 1; |
| int index = 0, r = 0; |
| struct shadow_spine spine; |
| struct btree_node *n; |
| struct dm_btree_value_type le64_vt; |
| |
| init_le64_type(info->tm, &le64_vt); |
| init_shadow_spine(&spine, info); |
| for (level = 0; level < info->levels; level++) { |
| r = remove_raw(&spine, info, |
| (level == last_level ? |
| &info->value_type : &le64_vt), |
| root, keys[level], (unsigned *)&index); |
| if (r < 0) |
| break; |
| |
| n = dm_block_data(shadow_current(&spine)); |
| if (level != last_level) { |
| root = value64(n, index); |
| continue; |
| } |
| |
| BUG_ON(index < 0 || index >= le32_to_cpu(n->header.nr_entries)); |
| |
| if (info->value_type.dec) |
| info->value_type.dec(info->value_type.context, |
| value_ptr(n, index)); |
| |
| delete_at(n, index); |
| } |
| |
| *new_root = shadow_root(&spine); |
| exit_shadow_spine(&spine); |
| |
| return r; |
| } |
| EXPORT_SYMBOL_GPL(dm_btree_remove); |
| |
| /*----------------------------------------------------------------*/ |
| |
| static int remove_nearest(struct shadow_spine *s, struct dm_btree_info *info, |
| struct dm_btree_value_type *vt, dm_block_t root, |
| uint64_t key, int *index) |
| { |
| int i = *index, r; |
| struct btree_node *n; |
| |
| for (;;) { |
| r = shadow_step(s, root, vt); |
| if (r < 0) |
| break; |
| |
| /* |
| * We have to patch up the parent node, ugly, but I don't |
| * see a way to do this automatically as part of the spine |
| * op. |
| */ |
| if (shadow_has_parent(s)) { |
| __le64 location = cpu_to_le64(dm_block_location(shadow_current(s))); |
| memcpy(value_ptr(dm_block_data(shadow_parent(s)), i), |
| &location, sizeof(__le64)); |
| } |
| |
| n = dm_block_data(shadow_current(s)); |
| |
| if (le32_to_cpu(n->header.flags) & LEAF_NODE) { |
| *index = lower_bound(n, key); |
| return 0; |
| } |
| |
| r = rebalance_children(s, info, vt, key); |
| if (r) |
| break; |
| |
| n = dm_block_data(shadow_current(s)); |
| if (le32_to_cpu(n->header.flags) & LEAF_NODE) { |
| *index = lower_bound(n, key); |
| return 0; |
| } |
| |
| i = lower_bound(n, key); |
| |
| /* |
| * We know the key is present, or else |
| * rebalance_children would have returned |
| * -ENODATA |
| */ |
| root = value64(n, i); |
| } |
| |
| return r; |
| } |
| |
| static int remove_one(struct dm_btree_info *info, dm_block_t root, |
| uint64_t *keys, uint64_t end_key, |
| dm_block_t *new_root, unsigned *nr_removed) |
| { |
| unsigned level, last_level = info->levels - 1; |
| int index = 0, r = 0; |
| struct shadow_spine spine; |
| struct btree_node *n; |
| struct dm_btree_value_type le64_vt; |
| uint64_t k; |
| |
| init_le64_type(info->tm, &le64_vt); |
| init_shadow_spine(&spine, info); |
| for (level = 0; level < last_level; level++) { |
| r = remove_raw(&spine, info, &le64_vt, |
| root, keys[level], (unsigned *) &index); |
| if (r < 0) |
| goto out; |
| |
| n = dm_block_data(shadow_current(&spine)); |
| root = value64(n, index); |
| } |
| |
| r = remove_nearest(&spine, info, &info->value_type, |
| root, keys[last_level], &index); |
| if (r < 0) |
| goto out; |
| |
| n = dm_block_data(shadow_current(&spine)); |
| |
| if (index < 0) |
| index = 0; |
| |
| if (index >= le32_to_cpu(n->header.nr_entries)) { |
| r = -ENODATA; |
| goto out; |
| } |
| |
| k = le64_to_cpu(n->keys[index]); |
| if (k >= keys[last_level] && k < end_key) { |
| if (info->value_type.dec) |
| info->value_type.dec(info->value_type.context, |
| value_ptr(n, index)); |
| |
| delete_at(n, index); |
| keys[last_level] = k + 1ull; |
| |
| } else |
| r = -ENODATA; |
| |
| out: |
| *new_root = shadow_root(&spine); |
| exit_shadow_spine(&spine); |
| |
| return r; |
| } |
| |
| int dm_btree_remove_leaves(struct dm_btree_info *info, dm_block_t root, |
| uint64_t *first_key, uint64_t end_key, |
| dm_block_t *new_root, unsigned *nr_removed) |
| { |
| int r; |
| |
| *nr_removed = 0; |
| do { |
| r = remove_one(info, root, first_key, end_key, &root, nr_removed); |
| if (!r) |
| (*nr_removed)++; |
| } while (!r); |
| |
| *new_root = root; |
| return r == -ENODATA ? 0 : r; |
| } |
| EXPORT_SYMBOL_GPL(dm_btree_remove_leaves); |