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assoc_array.c
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1751 lines (1539 loc) · 52.6 KB
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/* Generic associative array implementation.
*
* See Documentation/assoc_array.txt for information.
*
* Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
//#define DEBUG
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/assoc_array_priv.h>
/*
* Iterate over an associative array. The caller must hold the RCU read lock
* or better.
*/
static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
const struct assoc_array_ptr *stop,
int (*iterator)(const void *leaf,
void *iterator_data),
void *iterator_data)
{
const struct assoc_array_shortcut *shortcut;
const struct assoc_array_node *node;
const struct assoc_array_ptr *cursor, *ptr, *parent;
unsigned long has_meta;
int slot, ret;
cursor = root;
begin_node:
if (assoc_array_ptr_is_shortcut(cursor)) {
/* Descend through a shortcut */
shortcut = assoc_array_ptr_to_shortcut(cursor);
smp_read_barrier_depends();
cursor = ACCESS_ONCE(shortcut->next_node);
}
node = assoc_array_ptr_to_node(cursor);
smp_read_barrier_depends();
slot = 0;
/* We perform two passes of each node.
*
* The first pass does all the leaves in this node. This means we
* don't miss any leaves if the node is split up by insertion whilst
* we're iterating over the branches rooted here (we may, however, see
* some leaves twice).
*/
has_meta = 0;
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = ACCESS_ONCE(node->slots[slot]);
has_meta |= (unsigned long)ptr;
if (ptr && assoc_array_ptr_is_leaf(ptr)) {
/* We need a barrier between the read of the pointer
* and dereferencing the pointer - but only if we are
* actually going to dereference it.
*/
smp_read_barrier_depends();
/* Invoke the callback */
ret = iterator(assoc_array_ptr_to_leaf(ptr),
iterator_data);
if (ret)
return ret;
}
}
/* The second pass attends to all the metadata pointers. If we follow
* one of these we may find that we don't come back here, but rather go
* back to a replacement node with the leaves in a different layout.
*
* We are guaranteed to make progress, however, as the slot number for
* a particular portion of the key space cannot change - and we
* continue at the back pointer + 1.
*/
if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))
goto finished_node;
slot = 0;
continue_node:
node = assoc_array_ptr_to_node(cursor);
smp_read_barrier_depends();
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = ACCESS_ONCE(node->slots[slot]);
if (assoc_array_ptr_is_meta(ptr)) {
cursor = ptr;
goto begin_node;
}
}
finished_node:
/* Move up to the parent (may need to skip back over a shortcut) */
parent = ACCESS_ONCE(node->back_pointer);
slot = node->parent_slot;
if (parent == stop)
return 0;
if (assoc_array_ptr_is_shortcut(parent)) {
shortcut = assoc_array_ptr_to_shortcut(parent);
smp_read_barrier_depends();
cursor = parent;
parent = ACCESS_ONCE(shortcut->back_pointer);
slot = shortcut->parent_slot;
if (parent == stop)
return 0;
}
/* Ascend to next slot in parent node */
cursor = parent;
slot++;
goto continue_node;
}
/**
* assoc_array_iterate - Pass all objects in the array to a callback
* @array: The array to iterate over.
* @iterator: The callback function.
* @iterator_data: Private data for the callback function.
*
* Iterate over all the objects in an associative array. Each one will be
* presented to the iterator function.
*
* If the array is being modified concurrently with the iteration then it is
* possible that some objects in the array will be passed to the iterator
* callback more than once - though every object should be passed at least
* once. If this is undesirable then the caller must lock against modification
* for the duration of this function.
*
* The function will return 0 if no objects were in the array or else it will
* return the result of the last iterator function called. Iteration stops
* immediately if any call to the iteration function results in a non-zero
* return.
*
* The caller should hold the RCU read lock or better if concurrent
* modification is possible.
*/
int assoc_array_iterate(const struct assoc_array *array,
int (*iterator)(const void *object,
void *iterator_data),
void *iterator_data)
{
struct assoc_array_ptr *root = ACCESS_ONCE(array->root);
if (!root)
return 0;
return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data);
}
enum assoc_array_walk_status {
assoc_array_walk_tree_empty,
assoc_array_walk_found_terminal_node,
assoc_array_walk_found_wrong_shortcut,
};
struct assoc_array_walk_result {
struct {
struct assoc_array_node *node; /* Node in which leaf might be found */
int level;
int slot;
} terminal_node;
struct {
struct assoc_array_shortcut *shortcut;
int level;
int sc_level;
unsigned long sc_segments;
unsigned long dissimilarity;
} wrong_shortcut;
};
/*
* Navigate through the internal tree looking for the closest node to the key.
*/
static enum assoc_array_walk_status
assoc_array_walk(const struct assoc_array *array,
const struct assoc_array_ops *ops,
const void *index_key,
struct assoc_array_walk_result *result)
{
struct assoc_array_shortcut *shortcut;
struct assoc_array_node *node;
struct assoc_array_ptr *cursor, *ptr;
unsigned long sc_segments, dissimilarity;
unsigned long segments;
int level, sc_level, next_sc_level;
int slot;
pr_devel("-->%s()\n", __func__);
cursor = ACCESS_ONCE(array->root);
if (!cursor)
return assoc_array_walk_tree_empty;
level = 0;
/* Use segments from the key for the new leaf to navigate through the
* internal tree, skipping through nodes and shortcuts that are on
* route to the destination. Eventually we'll come to a slot that is
* either empty or contains a leaf at which point we've found a node in
* which the leaf we're looking for might be found or into which it
* should be inserted.
*/
jumped:
segments = ops->get_key_chunk(index_key, level);
pr_devel("segments[%d]: %lx\n", level, segments);
if (assoc_array_ptr_is_shortcut(cursor))
goto follow_shortcut;
consider_node:
node = assoc_array_ptr_to_node(cursor);
smp_read_barrier_depends();
slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
slot &= ASSOC_ARRAY_FAN_MASK;
ptr = ACCESS_ONCE(node->slots[slot]);
pr_devel("consider slot %x [ix=%d type=%lu]\n",
slot, level, (unsigned long)ptr & 3);
if (!assoc_array_ptr_is_meta(ptr)) {
/* The node doesn't have a node/shortcut pointer in the slot
* corresponding to the index key that we have to follow.
*/
result->terminal_node.node = node;
result->terminal_node.level = level;
result->terminal_node.slot = slot;
pr_devel("<--%s() = terminal_node\n", __func__);
return assoc_array_walk_found_terminal_node;
}
if (assoc_array_ptr_is_node(ptr)) {
/* There is a pointer to a node in the slot corresponding to
* this index key segment, so we need to follow it.
*/
cursor = ptr;
level += ASSOC_ARRAY_LEVEL_STEP;
if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0)
goto consider_node;
goto jumped;
}
/* There is a shortcut in the slot corresponding to the index key
* segment. We follow the shortcut if its partial index key matches
* this leaf's. Otherwise we need to split the shortcut.
*/
cursor = ptr;
follow_shortcut:
shortcut = assoc_array_ptr_to_shortcut(cursor);
smp_read_barrier_depends();
pr_devel("shortcut to %d\n", shortcut->skip_to_level);
sc_level = level + ASSOC_ARRAY_LEVEL_STEP;
BUG_ON(sc_level > shortcut->skip_to_level);
do {
/* Check the leaf against the shortcut's index key a word at a
* time, trimming the final word (the shortcut stores the index
* key completely from the root to the shortcut's target).
*/
if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0)
segments = ops->get_key_chunk(index_key, sc_level);
sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT];
dissimilarity = segments ^ sc_segments;
if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) {
/* Trim segments that are beyond the shortcut */
int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK;
dissimilarity &= ~(ULONG_MAX << shift);
next_sc_level = shortcut->skip_to_level;
} else {
next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE;
next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
}
if (dissimilarity != 0) {
/* This shortcut points elsewhere */
result->wrong_shortcut.shortcut = shortcut;
result->wrong_shortcut.level = level;
result->wrong_shortcut.sc_level = sc_level;
result->wrong_shortcut.sc_segments = sc_segments;
result->wrong_shortcut.dissimilarity = dissimilarity;
return assoc_array_walk_found_wrong_shortcut;
}
sc_level = next_sc_level;
} while (sc_level < shortcut->skip_to_level);
/* The shortcut matches the leaf's index to this point. */
cursor = ACCESS_ONCE(shortcut->next_node);
if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) {
level = sc_level;
goto jumped;
} else {
level = sc_level;
goto consider_node;
}
}
/**
* assoc_array_find - Find an object by index key
* @array: The associative array to search.
* @ops: The operations to use.
* @index_key: The key to the object.
*
* Find an object in an associative array by walking through the internal tree
* to the node that should contain the object and then searching the leaves
* there. NULL is returned if the requested object was not found in the array.
*
* The caller must hold the RCU read lock or better.
*/
void *assoc_array_find(const struct assoc_array *array,
const struct assoc_array_ops *ops,
const void *index_key)
{
struct assoc_array_walk_result result;
const struct assoc_array_node *node;
const struct assoc_array_ptr *ptr;
const void *leaf;
int slot;
if (assoc_array_walk(array, ops, index_key, &result) !=
assoc_array_walk_found_terminal_node)
return NULL;
node = result.terminal_node.node;
smp_read_barrier_depends();
/* If the target key is available to us, it's has to be pointed to by
* the terminal node.
*/
for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = ACCESS_ONCE(node->slots[slot]);
if (ptr && assoc_array_ptr_is_leaf(ptr)) {
/* We need a barrier between the read of the pointer
* and dereferencing the pointer - but only if we are
* actually going to dereference it.
*/
leaf = assoc_array_ptr_to_leaf(ptr);
smp_read_barrier_depends();
if (ops->compare_object(leaf, index_key))
return (void *)leaf;
}
}
return NULL;
}
/*
* Destructively iterate over an associative array. The caller must prevent
* other simultaneous accesses.
*/
static void assoc_array_destroy_subtree(struct assoc_array_ptr *root,
const struct assoc_array_ops *ops)
{
struct assoc_array_shortcut *shortcut;
struct assoc_array_node *node;
struct assoc_array_ptr *cursor, *parent = NULL;
int slot = -1;
pr_devel("-->%s()\n", __func__);
cursor = root;
if (!cursor) {
pr_devel("empty\n");
return;
}
move_to_meta:
if (assoc_array_ptr_is_shortcut(cursor)) {
/* Descend through a shortcut */
pr_devel("[%d] shortcut\n", slot);
BUG_ON(!assoc_array_ptr_is_shortcut(cursor));
shortcut = assoc_array_ptr_to_shortcut(cursor);
BUG_ON(shortcut->back_pointer != parent);
BUG_ON(slot != -1 && shortcut->parent_slot != slot);
parent = cursor;
cursor = shortcut->next_node;
slot = -1;
BUG_ON(!assoc_array_ptr_is_node(cursor));
}
pr_devel("[%d] node\n", slot);
node = assoc_array_ptr_to_node(cursor);
BUG_ON(node->back_pointer != parent);
BUG_ON(slot != -1 && node->parent_slot != slot);
slot = 0;
continue_node:
pr_devel("Node %p [back=%p]\n", node, node->back_pointer);
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
struct assoc_array_ptr *ptr = node->slots[slot];
if (!ptr)
continue;
if (assoc_array_ptr_is_meta(ptr)) {
parent = cursor;
cursor = ptr;
goto move_to_meta;
}
if (ops) {
pr_devel("[%d] free leaf\n", slot);
ops->free_object(assoc_array_ptr_to_leaf(ptr));
}
}
parent = node->back_pointer;
slot = node->parent_slot;
pr_devel("free node\n");
kfree(node);
if (!parent)
return; /* Done */
/* Move back up to the parent (may need to free a shortcut on
* the way up) */
if (assoc_array_ptr_is_shortcut(parent)) {
shortcut = assoc_array_ptr_to_shortcut(parent);
BUG_ON(shortcut->next_node != cursor);
cursor = parent;
parent = shortcut->back_pointer;
slot = shortcut->parent_slot;
pr_devel("free shortcut\n");
kfree(shortcut);
if (!parent)
return;
BUG_ON(!assoc_array_ptr_is_node(parent));
}
/* Ascend to next slot in parent node */
pr_devel("ascend to %p[%d]\n", parent, slot);
cursor = parent;
node = assoc_array_ptr_to_node(cursor);
slot++;
goto continue_node;
}
/**
* assoc_array_destroy - Destroy an associative array
* @array: The array to destroy.
* @ops: The operations to use.
*
* Discard all metadata and free all objects in an associative array. The
* array will be empty and ready to use again upon completion. This function
* cannot fail.
*
* The caller must prevent all other accesses whilst this takes place as no
* attempt is made to adjust pointers gracefully to permit RCU readlock-holding
* accesses to continue. On the other hand, no memory allocation is required.
*/
void assoc_array_destroy(struct assoc_array *array,
const struct assoc_array_ops *ops)
{
assoc_array_destroy_subtree(array->root, ops);
array->root = NULL;
}
/*
* Handle insertion into an empty tree.
*/
static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit)
{
struct assoc_array_node *new_n0;
pr_devel("-->%s()\n", __func__);
new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
if (!new_n0)
return false;
edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
edit->leaf_p = &new_n0->slots[0];
edit->adjust_count_on = new_n0;
edit->set[0].ptr = &edit->array->root;
edit->set[0].to = assoc_array_node_to_ptr(new_n0);
pr_devel("<--%s() = ok [no root]\n", __func__);
return true;
}
/*
* Handle insertion into a terminal node.
*/
static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
const struct assoc_array_ops *ops,
const void *index_key,
struct assoc_array_walk_result *result)
{
struct assoc_array_shortcut *shortcut, *new_s0;
struct assoc_array_node *node, *new_n0, *new_n1, *side;
struct assoc_array_ptr *ptr;
unsigned long dissimilarity, base_seg, blank;
size_t keylen;
bool have_meta;
int level, diff;
int slot, next_slot, free_slot, i, j;
node = result->terminal_node.node;
level = result->terminal_node.level;
edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot;
pr_devel("-->%s()\n", __func__);
/* We arrived at a node which doesn't have an onward node or shortcut
* pointer that we have to follow. This means that (a) the leaf we
* want must go here (either by insertion or replacement) or (b) we
* need to split this node and insert in one of the fragments.
*/
free_slot = -1;
/* Firstly, we have to check the leaves in this node to see if there's
* a matching one we should replace in place.
*/
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
ptr = node->slots[i];
if (!ptr) {
free_slot = i;
continue;
}
if (assoc_array_ptr_is_leaf(ptr) &&
ops->compare_object(assoc_array_ptr_to_leaf(ptr),
index_key)) {
pr_devel("replace in slot %d\n", i);
edit->leaf_p = &node->slots[i];
edit->dead_leaf = node->slots[i];
pr_devel("<--%s() = ok [replace]\n", __func__);
return true;
}
}
/* If there is a free slot in this node then we can just insert the
* leaf here.
*/
if (free_slot >= 0) {
pr_devel("insert in free slot %d\n", free_slot);
edit->leaf_p = &node->slots[free_slot];
edit->adjust_count_on = node;
pr_devel("<--%s() = ok [insert]\n", __func__);
return true;
}
/* The node has no spare slots - so we're either going to have to split
* it or insert another node before it.
*
* Whatever, we're going to need at least two new nodes - so allocate
* those now. We may also need a new shortcut, but we deal with that
* when we need it.
*/
new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
if (!new_n0)
return false;
edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
if (!new_n1)
return false;
edit->new_meta[1] = assoc_array_node_to_ptr(new_n1);
/* We need to find out how similar the leaves are. */
pr_devel("no spare slots\n");
have_meta = false;
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
ptr = node->slots[i];
if (assoc_array_ptr_is_meta(ptr)) {
edit->segment_cache[i] = 0xff;
have_meta = true;
continue;
}
base_seg = ops->get_object_key_chunk(
assoc_array_ptr_to_leaf(ptr), level);
base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
}
if (have_meta) {
pr_devel("have meta\n");
goto split_node;
}
/* The node contains only leaves */
dissimilarity = 0;
base_seg = edit->segment_cache[0];
for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++)
dissimilarity |= edit->segment_cache[i] ^ base_seg;
pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity);
if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) {
/* The old leaves all cluster in the same slot. We will need
* to insert a shortcut if the new node wants to cluster with them.
*/
if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0)
goto all_leaves_cluster_together;
/* Otherwise we can just insert a new node ahead of the old
* one.
*/
goto present_leaves_cluster_but_not_new_leaf;
}
split_node:
pr_devel("split node\n");
/* We need to split the current node; we know that the node doesn't
* simply contain a full set of leaves that cluster together (it
* contains meta pointers and/or non-clustering leaves).
*
* We need to expel at least two leaves out of a set consisting of the
* leaves in the node and the new leaf.
*
* We need a new node (n0) to replace the current one and a new node to
* take the expelled nodes (n1).
*/
edit->set[0].to = assoc_array_node_to_ptr(new_n0);
new_n0->back_pointer = node->back_pointer;
new_n0->parent_slot = node->parent_slot;
new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
new_n1->parent_slot = -1; /* Need to calculate this */
do_split_node:
pr_devel("do_split_node\n");
new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
new_n1->nr_leaves_on_branch = 0;
/* Begin by finding two matching leaves. There have to be at least two
* that match - even if there are meta pointers - because any leaf that
* would match a slot with a meta pointer in it must be somewhere
* behind that meta pointer and cannot be here. Further, given N
* remaining leaf slots, we now have N+1 leaves to go in them.
*/
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
slot = edit->segment_cache[i];
if (slot != 0xff)
for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)
if (edit->segment_cache[j] == slot)
goto found_slot_for_multiple_occupancy;
}
found_slot_for_multiple_occupancy:
pr_devel("same slot: %x %x [%02x]\n", i, j, slot);
BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);
BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);
BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);
new_n1->parent_slot = slot;
/* Metadata pointers cannot change slot */
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
if (assoc_array_ptr_is_meta(node->slots[i]))
new_n0->slots[i] = node->slots[i];
else
new_n0->slots[i] = NULL;
BUG_ON(new_n0->slots[slot] != NULL);
new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);
/* Filter the leaf pointers between the new nodes */
free_slot = -1;
next_slot = 0;
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
if (assoc_array_ptr_is_meta(node->slots[i]))
continue;
if (edit->segment_cache[i] == slot) {
new_n1->slots[next_slot++] = node->slots[i];
new_n1->nr_leaves_on_branch++;
} else {
do {
free_slot++;
} while (new_n0->slots[free_slot] != NULL);
new_n0->slots[free_slot] = node->slots[i];
}
}
pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);
if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {
do {
free_slot++;
} while (new_n0->slots[free_slot] != NULL);
edit->leaf_p = &new_n0->slots[free_slot];
edit->adjust_count_on = new_n0;
} else {
edit->leaf_p = &new_n1->slots[next_slot++];
edit->adjust_count_on = new_n1;
}
BUG_ON(next_slot <= 1);
edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
if (edit->segment_cache[i] == 0xff) {
ptr = node->slots[i];
BUG_ON(assoc_array_ptr_is_leaf(ptr));
if (assoc_array_ptr_is_node(ptr)) {
side = assoc_array_ptr_to_node(ptr);
edit->set_backpointers[i] = &side->back_pointer;
} else {
shortcut = assoc_array_ptr_to_shortcut(ptr);
edit->set_backpointers[i] = &shortcut->back_pointer;
}
}
}
ptr = node->back_pointer;
if (!ptr)
edit->set[0].ptr = &edit->array->root;
else if (assoc_array_ptr_is_node(ptr))
edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];
else
edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;
edit->excised_meta[0] = assoc_array_node_to_ptr(node);
pr_devel("<--%s() = ok [split node]\n", __func__);
return true;
present_leaves_cluster_but_not_new_leaf:
/* All the old leaves cluster in the same slot, but the new leaf wants
* to go into a different slot, so we create a new node to hold the new
* leaf and a pointer to a new node holding all the old leaves.
*/
pr_devel("present leaves cluster but not new leaf\n");
new_n0->back_pointer = node->back_pointer;
new_n0->parent_slot = node->parent_slot;
new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
new_n1->parent_slot = edit->segment_cache[0];
new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch;
edit->adjust_count_on = new_n0;
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
new_n1->slots[i] = node->slots[i];
new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0);
edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]];
edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot];
edit->set[0].to = assoc_array_node_to_ptr(new_n0);
edit->excised_meta[0] = assoc_array_node_to_ptr(node);
pr_devel("<--%s() = ok [insert node before]\n", __func__);
return true;
all_leaves_cluster_together:
/* All the leaves, new and old, want to cluster together in this node
* in the same slot, so we have to replace this node with a shortcut to
* skip over the identical parts of the key and then place a pair of
* nodes, one inside the other, at the end of the shortcut and
* distribute the keys between them.
*
* Firstly we need to work out where the leaves start diverging as a
* bit position into their keys so that we know how big the shortcut
* needs to be.
*
* We only need to make a single pass of N of the N+1 leaves because if
* any keys differ between themselves at bit X then at least one of
* them must also differ with the base key at bit X or before.
*/
pr_devel("all leaves cluster together\n");
diff = INT_MAX;
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]),
index_key);
if (x < diff) {
BUG_ON(x < 0);
diff = x;
}
}
BUG_ON(diff == INT_MAX);
BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);
keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
keylen * sizeof(unsigned long), GFP_KERNEL);
if (!new_s0)
return false;
edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
new_s0->back_pointer = node->back_pointer;
new_s0->parent_slot = node->parent_slot;
new_s0->next_node = assoc_array_node_to_ptr(new_n0);
new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
new_n0->parent_slot = 0;
new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
new_n1->parent_slot = -1; /* Need to calculate this */
new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;
pr_devel("skip_to_level = %d [diff %d]\n", level, diff);
BUG_ON(level <= 0);
for (i = 0; i < keylen; i++)
new_s0->index_key[i] =
ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
new_s0->index_key[keylen - 1] &= ~blank;
/* This now reduces to a node splitting exercise for which we'll need
* to regenerate the disparity table.
*/
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
ptr = node->slots[i];
base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),
level);
base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
}
base_seg = ops->get_key_chunk(index_key, level);
base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;
goto do_split_node;
}
/*
* Handle insertion into the middle of a shortcut.
*/
static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
const struct assoc_array_ops *ops,
struct assoc_array_walk_result *result)
{
struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;
struct assoc_array_node *node, *new_n0, *side;
unsigned long sc_segments, dissimilarity, blank;
size_t keylen;
int level, sc_level, diff;
int sc_slot;
shortcut = result->wrong_shortcut.shortcut;
level = result->wrong_shortcut.level;
sc_level = result->wrong_shortcut.sc_level;
sc_segments = result->wrong_shortcut.sc_segments;
dissimilarity = result->wrong_shortcut.dissimilarity;
pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",
__func__, level, dissimilarity, sc_level);
/* We need to split a shortcut and insert a node between the two
* pieces. Zero-length pieces will be dispensed with entirely.
*
* First of all, we need to find out in which level the first
* difference was.
*/
diff = __ffs(dissimilarity);
diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;
diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;
pr_devel("diff=%d\n", diff);
if (!shortcut->back_pointer) {
edit->set[0].ptr = &edit->array->root;
} else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {
node = assoc_array_ptr_to_node(shortcut->back_pointer);
edit->set[0].ptr = &node->slots[shortcut->parent_slot];
} else {
BUG();
}
edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);
/* Create a new node now since we're going to need it anyway */
new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
if (!new_n0)
return false;
edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
edit->adjust_count_on = new_n0;
/* Insert a new shortcut before the new node if this segment isn't of
* zero length - otherwise we just connect the new node directly to the
* parent.
*/
level += ASSOC_ARRAY_LEVEL_STEP;
if (diff > level) {
pr_devel("pre-shortcut %d...%d\n", level, diff);
keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
keylen * sizeof(unsigned long), GFP_KERNEL);
if (!new_s0)
return false;
edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
new_s0->back_pointer = shortcut->back_pointer;
new_s0->parent_slot = shortcut->parent_slot;
new_s0->next_node = assoc_array_node_to_ptr(new_n0);
new_s0->skip_to_level = diff;
new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
new_n0->parent_slot = 0;
memcpy(new_s0->index_key, shortcut->index_key,
keylen * sizeof(unsigned long));
blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
new_s0->index_key[keylen - 1] &= ~blank;
} else {
pr_devel("no pre-shortcut\n");
edit->set[0].to = assoc_array_node_to_ptr(new_n0);
new_n0->back_pointer = shortcut->back_pointer;
new_n0->parent_slot = shortcut->parent_slot;
}
side = assoc_array_ptr_to_node(shortcut->next_node);
new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;
/* We need to know which slot in the new node is going to take a
* metadata pointer.
*/
sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
sc_slot &= ASSOC_ARRAY_FAN_MASK;
pr_devel("new slot %lx >> %d -> %d\n",
sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);
/* Determine whether we need to follow the new node with a replacement
* for the current shortcut. We could in theory reuse the current
* shortcut if its parent slot number doesn't change - but that's a
* 1-in-16 chance so not worth expending the code upon.
*/
level = diff + ASSOC_ARRAY_LEVEL_STEP;
if (level < shortcut->skip_to_level) {
pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);
keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
keylen * sizeof(unsigned long), GFP_KERNEL);
if (!new_s1)
return false;
edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);
new_s1->parent_slot = sc_slot;
new_s1->next_node = shortcut->next_node;
new_s1->skip_to_level = shortcut->skip_to_level;
new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
memcpy(new_s1->index_key, shortcut->index_key,
keylen * sizeof(unsigned long));
edit->set[1].ptr = &side->back_pointer;
edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
} else {
pr_devel("no post-shortcut\n");
/* We don't have to replace the pointed-to node as long as we
* use memory barriers to make sure the parent slot number is
* changed before the back pointer (the parent slot number is
* irrelevant to the old parent shortcut).
*/
new_n0->slots[sc_slot] = shortcut->next_node;
edit->set_parent_slot[0].p = &side->parent_slot;
edit->set_parent_slot[0].to = sc_slot;
edit->set[1].ptr = &side->back_pointer;
edit->set[1].to = assoc_array_node_to_ptr(new_n0);
}
/* Install the new leaf in a spare slot in the new node. */
if (sc_slot == 0)
edit->leaf_p = &new_n0->slots[1];
else
edit->leaf_p = &new_n0->slots[0];
pr_devel("<--%s() = ok [split shortcut]\n", __func__);
return edit;
}
/**
* assoc_array_insert - Script insertion of an object into an associative array
* @array: The array to insert into.
* @ops: The operations to use.
* @index_key: The key to insert at.
* @object: The object to insert.
*
* Precalculate and preallocate a script for the insertion or replacement of an
* object in an associative array. This results in an edit script that can
* either be applied or cancelled.
*
* The function returns a pointer to an edit script or -ENOMEM.
*
* The caller should lock against other modifications and must continue to hold
* the lock until assoc_array_apply_edit() has been called.
*
* Accesses to the tree may take place concurrently with this function,
* provided they hold the RCU read lock.
*/
struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
const struct assoc_array_ops *ops,
const void *index_key,
void *object)
{