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687 lines
17 KiB
687 lines
17 KiB
/* |
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* Copyright (C) 2011 Red Hat, Inc. |
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* |
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* This file is released under the GPL. |
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*/ |
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|
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#include "dm-btree.h" |
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#include "dm-btree-internal.h" |
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#include "dm-transaction-manager.h" |
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|
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#include <linux/export.h> |
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|
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/* |
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* Removing an entry from a btree |
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* ============================== |
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* |
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* A very important constraint for our btree is that no node, except the |
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* root, may have fewer than a certain number of entries. |
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* (MIN_ENTRIES <= nr_entries <= MAX_ENTRIES). |
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* |
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* Ensuring this is complicated by the way we want to only ever hold the |
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* locks on 2 nodes concurrently, and only change nodes in a top to bottom |
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* fashion. |
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* |
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* Each node may have a left or right sibling. When decending the spine, |
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* if a node contains only MIN_ENTRIES then we try and increase this to at |
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* least MIN_ENTRIES + 1. We do this in the following ways: |
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* |
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* [A] No siblings => this can only happen if the node is the root, in which |
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* case we copy the childs contents over the root. |
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* |
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* [B] No left sibling |
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* ==> rebalance(node, right sibling) |
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* |
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* [C] No right sibling |
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* ==> rebalance(left sibling, node) |
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* |
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* [D] Both siblings, total_entries(left, node, right) <= DEL_THRESHOLD |
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* ==> delete node adding it's contents to left and right |
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* |
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* [E] Both siblings, total_entries(left, node, right) > DEL_THRESHOLD |
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* ==> rebalance(left, node, right) |
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* |
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* After these operations it's possible that the our original node no |
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* longer contains the desired sub tree. For this reason this rebalancing |
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* is performed on the children of the current node. This also avoids |
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* having a special case for the root. |
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* |
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* Once this rebalancing has occurred we can then step into the child node |
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* for internal nodes. Or delete the entry for leaf nodes. |
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*/ |
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|
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/* |
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* Some little utilities for moving node data around. |
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*/ |
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static void node_shift(struct btree_node *n, int shift) |
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{ |
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uint32_t nr_entries = le32_to_cpu(n->header.nr_entries); |
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uint32_t value_size = le32_to_cpu(n->header.value_size); |
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if (shift < 0) { |
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shift = -shift; |
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BUG_ON(shift > nr_entries); |
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BUG_ON((void *) key_ptr(n, shift) >= value_ptr(n, shift)); |
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memmove(key_ptr(n, 0), |
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key_ptr(n, shift), |
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(nr_entries - shift) * sizeof(__le64)); |
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memmove(value_ptr(n, 0), |
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value_ptr(n, shift), |
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(nr_entries - shift) * value_size); |
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} else { |
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BUG_ON(nr_entries + shift > le32_to_cpu(n->header.max_entries)); |
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memmove(key_ptr(n, shift), |
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key_ptr(n, 0), |
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nr_entries * sizeof(__le64)); |
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memmove(value_ptr(n, shift), |
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value_ptr(n, 0), |
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nr_entries * value_size); |
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} |
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} |
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static void node_copy(struct btree_node *left, struct btree_node *right, int shift) |
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{ |
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uint32_t nr_left = le32_to_cpu(left->header.nr_entries); |
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uint32_t value_size = le32_to_cpu(left->header.value_size); |
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BUG_ON(value_size != le32_to_cpu(right->header.value_size)); |
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if (shift < 0) { |
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shift = -shift; |
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BUG_ON(nr_left + shift > le32_to_cpu(left->header.max_entries)); |
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memcpy(key_ptr(left, nr_left), |
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key_ptr(right, 0), |
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shift * sizeof(__le64)); |
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memcpy(value_ptr(left, nr_left), |
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value_ptr(right, 0), |
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shift * value_size); |
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} else { |
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BUG_ON(shift > le32_to_cpu(right->header.max_entries)); |
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memcpy(key_ptr(right, 0), |
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key_ptr(left, nr_left - shift), |
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shift * sizeof(__le64)); |
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memcpy(value_ptr(right, 0), |
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value_ptr(left, nr_left - shift), |
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shift * value_size); |
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} |
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} |
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/* |
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* Delete a specific entry from a leaf node. |
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*/ |
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static void delete_at(struct btree_node *n, unsigned index) |
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{ |
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unsigned nr_entries = le32_to_cpu(n->header.nr_entries); |
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unsigned nr_to_copy = nr_entries - (index + 1); |
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uint32_t value_size = le32_to_cpu(n->header.value_size); |
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BUG_ON(index >= nr_entries); |
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if (nr_to_copy) { |
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memmove(key_ptr(n, index), |
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key_ptr(n, index + 1), |
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nr_to_copy * sizeof(__le64)); |
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memmove(value_ptr(n, index), |
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value_ptr(n, index + 1), |
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nr_to_copy * value_size); |
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} |
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n->header.nr_entries = cpu_to_le32(nr_entries - 1); |
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} |
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static unsigned merge_threshold(struct btree_node *n) |
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{ |
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return le32_to_cpu(n->header.max_entries) / 3; |
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} |
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struct child { |
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unsigned index; |
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struct dm_block *block; |
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struct btree_node *n; |
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}; |
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static int init_child(struct dm_btree_info *info, struct dm_btree_value_type *vt, |
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struct btree_node *parent, |
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unsigned index, struct child *result) |
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{ |
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int r, inc; |
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dm_block_t root; |
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result->index = index; |
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root = value64(parent, index); |
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r = dm_tm_shadow_block(info->tm, root, &btree_node_validator, |
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&result->block, &inc); |
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if (r) |
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return r; |
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result->n = dm_block_data(result->block); |
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if (inc) |
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inc_children(info->tm, result->n, vt); |
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*((__le64 *) value_ptr(parent, index)) = |
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cpu_to_le64(dm_block_location(result->block)); |
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return 0; |
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} |
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static void exit_child(struct dm_btree_info *info, struct child *c) |
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{ |
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dm_tm_unlock(info->tm, c->block); |
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} |
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static void shift(struct btree_node *left, struct btree_node *right, int count) |
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{ |
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uint32_t nr_left = le32_to_cpu(left->header.nr_entries); |
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uint32_t nr_right = le32_to_cpu(right->header.nr_entries); |
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uint32_t max_entries = le32_to_cpu(left->header.max_entries); |
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uint32_t r_max_entries = le32_to_cpu(right->header.max_entries); |
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BUG_ON(max_entries != r_max_entries); |
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BUG_ON(nr_left - count > max_entries); |
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BUG_ON(nr_right + count > max_entries); |
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if (!count) |
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return; |
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if (count > 0) { |
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node_shift(right, count); |
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node_copy(left, right, count); |
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} else { |
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node_copy(left, right, count); |
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node_shift(right, count); |
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} |
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left->header.nr_entries = cpu_to_le32(nr_left - count); |
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right->header.nr_entries = cpu_to_le32(nr_right + count); |
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} |
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static void __rebalance2(struct dm_btree_info *info, struct btree_node *parent, |
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struct child *l, struct child *r) |
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{ |
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struct btree_node *left = l->n; |
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struct btree_node *right = r->n; |
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uint32_t nr_left = le32_to_cpu(left->header.nr_entries); |
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uint32_t nr_right = le32_to_cpu(right->header.nr_entries); |
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/* |
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* Ensure the number of entries in each child will be greater |
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* than or equal to (max_entries / 3 + 1), so no matter which |
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* child is used for removal, the number will still be not |
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* less than (max_entries / 3). |
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*/ |
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unsigned int threshold = 2 * (merge_threshold(left) + 1); |
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if (nr_left + nr_right < threshold) { |
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/* |
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* Merge |
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*/ |
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node_copy(left, right, -nr_right); |
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left->header.nr_entries = cpu_to_le32(nr_left + nr_right); |
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delete_at(parent, r->index); |
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/* |
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* We need to decrement the right block, but not it's |
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* children, since they're still referenced by left. |
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*/ |
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dm_tm_dec(info->tm, dm_block_location(r->block)); |
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} else { |
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/* |
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* Rebalance. |
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*/ |
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unsigned target_left = (nr_left + nr_right) / 2; |
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shift(left, right, nr_left - target_left); |
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*key_ptr(parent, r->index) = right->keys[0]; |
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} |
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} |
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static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info, |
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struct dm_btree_value_type *vt, unsigned left_index) |
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{ |
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int r; |
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struct btree_node *parent; |
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struct child left, right; |
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parent = dm_block_data(shadow_current(s)); |
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r = init_child(info, vt, parent, left_index, &left); |
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if (r) |
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return r; |
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r = init_child(info, vt, parent, left_index + 1, &right); |
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if (r) { |
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exit_child(info, &left); |
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return r; |
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} |
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__rebalance2(info, parent, &left, &right); |
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exit_child(info, &left); |
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exit_child(info, &right); |
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return 0; |
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} |
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/* |
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* We dump as many entries from center as possible into left, then the rest |
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* in right, then rebalance2. This wastes some cpu, but I want something |
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* simple atm. |
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*/ |
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static void delete_center_node(struct dm_btree_info *info, struct btree_node *parent, |
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struct child *l, struct child *c, struct child *r, |
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struct btree_node *left, struct btree_node *center, struct btree_node *right, |
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uint32_t nr_left, uint32_t nr_center, uint32_t nr_right) |
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{ |
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uint32_t max_entries = le32_to_cpu(left->header.max_entries); |
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unsigned shift = min(max_entries - nr_left, nr_center); |
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BUG_ON(nr_left + shift > max_entries); |
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node_copy(left, center, -shift); |
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left->header.nr_entries = cpu_to_le32(nr_left + shift); |
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if (shift != nr_center) { |
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shift = nr_center - shift; |
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BUG_ON((nr_right + shift) > max_entries); |
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node_shift(right, shift); |
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node_copy(center, right, shift); |
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right->header.nr_entries = cpu_to_le32(nr_right + shift); |
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} |
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*key_ptr(parent, r->index) = right->keys[0]; |
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delete_at(parent, c->index); |
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r->index--; |
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dm_tm_dec(info->tm, dm_block_location(c->block)); |
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__rebalance2(info, parent, l, r); |
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} |
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/* |
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* Redistributes entries among 3 sibling nodes. |
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*/ |
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static void redistribute3(struct dm_btree_info *info, struct btree_node *parent, |
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struct child *l, struct child *c, struct child *r, |
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struct btree_node *left, struct btree_node *center, struct btree_node *right, |
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uint32_t nr_left, uint32_t nr_center, uint32_t nr_right) |
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{ |
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int s; |
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uint32_t max_entries = le32_to_cpu(left->header.max_entries); |
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unsigned total = nr_left + nr_center + nr_right; |
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unsigned target_right = total / 3; |
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unsigned remainder = (target_right * 3) != total; |
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unsigned target_left = target_right + remainder; |
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BUG_ON(target_left > max_entries); |
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BUG_ON(target_right > max_entries); |
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if (nr_left < nr_right) { |
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s = nr_left - target_left; |
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if (s < 0 && nr_center < -s) { |
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/* not enough in central node */ |
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shift(left, center, -nr_center); |
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s += nr_center; |
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shift(left, right, s); |
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nr_right += s; |
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} else |
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shift(left, center, s); |
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shift(center, right, target_right - nr_right); |
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} else { |
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s = target_right - nr_right; |
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if (s > 0 && nr_center < s) { |
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/* not enough in central node */ |
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shift(center, right, nr_center); |
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s -= nr_center; |
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shift(left, right, s); |
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nr_left -= s; |
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} else |
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shift(center, right, s); |
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shift(left, center, nr_left - target_left); |
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} |
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*key_ptr(parent, c->index) = center->keys[0]; |
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*key_ptr(parent, r->index) = right->keys[0]; |
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} |
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static void __rebalance3(struct dm_btree_info *info, struct btree_node *parent, |
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struct child *l, struct child *c, struct child *r) |
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{ |
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struct btree_node *left = l->n; |
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struct btree_node *center = c->n; |
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struct btree_node *right = r->n; |
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uint32_t nr_left = le32_to_cpu(left->header.nr_entries); |
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uint32_t nr_center = le32_to_cpu(center->header.nr_entries); |
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uint32_t nr_right = le32_to_cpu(right->header.nr_entries); |
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unsigned threshold = merge_threshold(left) * 4 + 1; |
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BUG_ON(left->header.max_entries != center->header.max_entries); |
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BUG_ON(center->header.max_entries != right->header.max_entries); |
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if ((nr_left + nr_center + nr_right) < threshold) |
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delete_center_node(info, parent, l, c, r, left, center, right, |
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nr_left, nr_center, nr_right); |
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else |
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redistribute3(info, parent, l, c, r, left, center, right, |
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nr_left, nr_center, nr_right); |
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} |
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static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info, |
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struct dm_btree_value_type *vt, unsigned left_index) |
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{ |
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int r; |
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struct btree_node *parent = dm_block_data(shadow_current(s)); |
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struct child left, center, right; |
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/* |
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* FIXME: fill out an array? |
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*/ |
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r = init_child(info, vt, parent, left_index, &left); |
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if (r) |
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return r; |
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r = init_child(info, vt, parent, left_index + 1, ¢er); |
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if (r) { |
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exit_child(info, &left); |
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return r; |
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} |
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r = init_child(info, vt, parent, left_index + 2, &right); |
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if (r) { |
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exit_child(info, &left); |
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exit_child(info, ¢er); |
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return r; |
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} |
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__rebalance3(info, parent, &left, ¢er, &right); |
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exit_child(info, &left); |
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exit_child(info, ¢er); |
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exit_child(info, &right); |
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return 0; |
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} |
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static int rebalance_children(struct shadow_spine *s, |
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struct dm_btree_info *info, |
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struct dm_btree_value_type *vt, uint64_t key) |
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{ |
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int i, r, has_left_sibling, has_right_sibling; |
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struct btree_node *n; |
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n = dm_block_data(shadow_current(s)); |
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if (le32_to_cpu(n->header.nr_entries) == 1) { |
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struct dm_block *child; |
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dm_block_t b = value64(n, 0); |
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r = dm_tm_read_lock(info->tm, b, &btree_node_validator, &child); |
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if (r) |
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return r; |
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memcpy(n, dm_block_data(child), |
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dm_bm_block_size(dm_tm_get_bm(info->tm))); |
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dm_tm_unlock(info->tm, child); |
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dm_tm_dec(info->tm, dm_block_location(child)); |
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return 0; |
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} |
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i = lower_bound(n, key); |
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if (i < 0) |
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return -ENODATA; |
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has_left_sibling = i > 0; |
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has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1); |
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if (!has_left_sibling) |
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r = rebalance2(s, info, vt, i); |
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else if (!has_right_sibling) |
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r = rebalance2(s, info, vt, i - 1); |
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else |
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r = rebalance3(s, info, vt, i - 1); |
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return r; |
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} |
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static int do_leaf(struct btree_node *n, uint64_t key, unsigned *index) |
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{ |
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int i = lower_bound(n, key); |
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if ((i < 0) || |
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(i >= le32_to_cpu(n->header.nr_entries)) || |
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(le64_to_cpu(n->keys[i]) != key)) |
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return -ENODATA; |
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*index = i; |
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return 0; |
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} |
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/* |
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* Prepares for removal from one level of the hierarchy. The caller must |
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* call delete_at() to remove the entry at index. |
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*/ |
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static int remove_raw(struct shadow_spine *s, struct dm_btree_info *info, |
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struct dm_btree_value_type *vt, dm_block_t root, |
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uint64_t key, unsigned *index) |
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{ |
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int i = *index, r; |
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struct btree_node *n; |
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for (;;) { |
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r = shadow_step(s, root, vt); |
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if (r < 0) |
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break; |
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/* |
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* We have to patch up the parent node, ugly, but I don't |
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* see a way to do this automatically as part of the spine |
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* op. |
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*/ |
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if (shadow_has_parent(s)) { |
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__le64 location = cpu_to_le64(dm_block_location(shadow_current(s))); |
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memcpy(value_ptr(dm_block_data(shadow_parent(s)), i), |
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&location, sizeof(__le64)); |
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} |
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n = dm_block_data(shadow_current(s)); |
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if (le32_to_cpu(n->header.flags) & LEAF_NODE) |
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return do_leaf(n, key, index); |
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r = rebalance_children(s, info, vt, key); |
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if (r) |
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break; |
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n = dm_block_data(shadow_current(s)); |
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if (le32_to_cpu(n->header.flags) & LEAF_NODE) |
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return do_leaf(n, key, index); |
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i = lower_bound(n, key); |
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|
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/* |
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* We know the key is present, or else |
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* rebalance_children would have returned |
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* -ENODATA |
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*/ |
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root = value64(n, i); |
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} |
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return r; |
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} |
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int dm_btree_remove(struct dm_btree_info *info, dm_block_t root, |
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uint64_t *keys, dm_block_t *new_root) |
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{ |
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unsigned level, last_level = info->levels - 1; |
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int index = 0, r = 0; |
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struct shadow_spine spine; |
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struct btree_node *n; |
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struct dm_btree_value_type le64_vt; |
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|
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init_le64_type(info->tm, &le64_vt); |
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init_shadow_spine(&spine, info); |
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for (level = 0; level < info->levels; level++) { |
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r = remove_raw(&spine, info, |
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(level == last_level ? |
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&info->value_type : &le64_vt), |
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root, keys[level], (unsigned *)&index); |
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if (r < 0) |
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break; |
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n = dm_block_data(shadow_current(&spine)); |
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if (level != last_level) { |
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root = value64(n, index); |
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continue; |
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} |
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BUG_ON(index < 0 || index >= le32_to_cpu(n->header.nr_entries)); |
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|
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if (info->value_type.dec) |
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info->value_type.dec(info->value_type.context, |
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value_ptr(n, index)); |
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|
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delete_at(n, index); |
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} |
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*new_root = shadow_root(&spine); |
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exit_shadow_spine(&spine); |
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return r; |
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} |
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EXPORT_SYMBOL_GPL(dm_btree_remove); |
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|
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/*----------------------------------------------------------------*/ |
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|
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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);
|
|
|