// SPDX-License-Identifier: GPL-2.0-or-later
/* Generic associative array implementation.
*
* See Documentation/core-api/assoc_array.rst for information.
*
* Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*/
//#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);
cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */
}
node = assoc_array_ptr_to_node(cursor);
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 = READ_ONCE(node->slots[slot]); /* Address dependency. */
has_meta |= (unsigned long)ptr;
if (ptr && assoc_array_ptr_is_leaf(ptr)) {
/* We need a barrier between the read of the pointer,
* which is supplied by the above READ_ONCE().
*/
/* 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);
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
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 = READ_ONCE(node->back_pointer); /* Address dependency. */
slot = node->parent_slot;
if (parent == stop)
return 0;
if (assoc_array_ptr_is_shortcut(parent)) {
shortcut = assoc_array_ptr_to_shortcut(parent);
cursor = parent;
parent = READ_ONCE(shortcut->back_pointer); /* Address dependency. */
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 = READ_ONCE(array->root); /* Address dependency. */
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 = READ_ONCE(array->root); /* Address dependency. */
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);
slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
slot &= ASSOC_ARRAY_FAN_MASK;
ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
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);
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 = READ_ONCE(shortcut->next_node); /* Address dependency. */
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;
/* 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 = READ_ONCE(node->slots[slot]); /* Address dependency. */
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);
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 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 (n0) to hold the new leaf and a pointer to
* a new node (n1) holding all the old leaves.
*
* This can be done by falling through to the node splitting
* path.
*/
pr_devel("present leaves cluster but not new leaf\n");
}
split_node:
pr_devel("split node\n");
/* We need to split the current node. The node must contain anything
* from a single leaf (in the one leaf case, this leaf will cluster
* with the new leaf) and the rest meta-pointers, to all leaves, some
* of which may cluster.
*
* It won't contain the case in which all the current leaves plus the
* new leaves want to cluster in the same slot.
*
* We need to expel at least two leaves out of a set consisting of the
* leaves in the node and the new leaf. The current meta pointers can
* just be copied as they shouldn't cluster with any of the leaves.
*
* 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;
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(struct_size(new_s0, index_key, keylen), 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);
if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) {
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(struct_size(new_s0, index_key, keylen),
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,
flex_array_size(new_s0, index_key, keylen));
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(struct_size(new_s1, index_key, keylen),
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,
flex_array_size(new_s1, index_key, keylen));
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 true;
}
/**
* 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)
{
struct assoc_array_walk_result result;
struct assoc_array_edit *edit;
pr_devel("-->%s()\n", __func__);
/* The leaf pointer we're given must not have the bottom bit set as we
* use those for type-marking the pointer. NULL pointers are also not
* allowed as they indicate an empty slot but we have to allow them
* here as they can be updated later.
*/
BUG_ON(assoc_array_ptr_is_meta(object));
edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
if (!edit)
return ERR_PTR(-ENOMEM);
edit->array = array;
edit->ops = ops;
edit->leaf = assoc_array_leaf_to_ptr(object);
edit->adjust_count_by = 1;
switch (assoc_array_walk(array, ops, index_key, &result)) {
case assoc_array_walk_tree_empty:
/* Allocate a root node if there isn't one yet */
if (!assoc_array_insert_in_empty_tree(edit))
goto enomem;
return edit;
case assoc_array_walk_found_terminal_node:
/* We found a node that doesn't have a node/shortcut pointer in
* the slot corresponding to the index key that we have to
* follow.
*/
if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,
&result))
goto enomem;
return edit;
case assoc_array_walk_found_wrong_shortcut:
/* We found a shortcut that didn't match our key in a slot we
* needed to follow.
*/
if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
goto enomem;
return edit;
}
enomem:
/* Clean up after an out of memory error */
pr_devel("enomem\n");
assoc_array_cancel_edit(edit);
return ERR_PTR(-ENOMEM);
}
/**
* assoc_array_insert_set_object - Set the new object pointer in an edit script
* @edit: The edit script to modify.
* @object: The object pointer to set.
*
* Change the object to be inserted in an edit script. The object pointed to
* by the old object is not freed. This must be done prior to applying the
* script.
*/
void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)
{
BUG_ON(!object);
edit->leaf = assoc_array_leaf_to_ptr(object);
}
struct assoc_array_delete_collapse_context {
struct assoc_array_node *node;
const void *skip_leaf;
int slot;
};
/*
* Subtree collapse to node iterator.
*/
static int assoc_array_delete_collapse_iterator(const void *leaf,
void *iterator_data)
{
struct assoc_array_delete_collapse_context *collapse = iterator_data;
if (leaf == collapse->skip_leaf)
return 0;
BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);
collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);
return 0;
}
/**
* assoc_array_delete - Script deletion of an object from an associative array
* @array: The array to search.
* @ops: The operations to use.
* @index_key: The key to the object.
*
* Precalculate and preallocate a script for the deletion of an object from 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 if the object was found,
* NULL if the object was not found 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_delete(struct assoc_array *array,
const struct assoc_array_ops *ops,
const void *index_key)
{
struct assoc_array_delete_collapse_context collapse;
struct assoc_array_walk_result result;
struct assoc_array_node *node, *new_n0;
struct assoc_array_edit *edit;
struct assoc_array_ptr *ptr;
bool has_meta;
int slot, i;
pr_devel("-->%s()\n", __func__);
edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
if (!edit)
return ERR_PTR(-ENOMEM);
edit->array = array;
edit->ops = ops;
edit->adjust_count_by = -1;
switch (assoc_array_walk(array, ops, index_key, &result)) {
case assoc_array_walk_found_terminal_node:
/* We found a node that should contain the leaf we've been
* asked to remove - *if* it's in the tree.
*/
pr_devel("terminal_node\n");
node = result.terminal_node.node;
for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = node->slots[slot];
if (ptr &&
assoc_array_ptr_is_leaf(ptr) &&
ops->compare_object(assoc_array_ptr_to_leaf(ptr),
index_key))
goto found_leaf;
}
fallthrough;
case assoc_array_walk_tree_empty:
case assoc_array_walk_found_wrong_shortcut:
default:
assoc_array_cancel_edit(edit);
pr_devel("not found\n");
return NULL;
}
found_leaf:
BUG_ON(array->nr_leaves_on_tree <= 0);
/* In the simplest form of deletion we just clear the slot and release
* the leaf after a suitable interval.
*/
edit->dead_leaf = node->slots[slot];
edit->set[0].ptr = &node->slots[slot];
edit->set[0].to = NULL;
edit->adjust_count_on = node;
/* If that concludes erasure of the last leaf, then delete the entire
* internal array.
*/
if (array->nr_leaves_on_tree == 1) {
edit->set[1].ptr = &array->root;
edit->set[1].to = NULL;
edit->adjust_count_on = NULL;
edit->excised_subtree = array->root;
pr_devel("all gone\n");
return edit;
}
/* However, we'd also like to clear up some metadata blocks if we
* possibly can.
*
* We go for a simple algorithm of: if this node has FAN_OUT or fewer
* leaves in it, then attempt to collapse it - and attempt to
* recursively collapse up the tree.
*
* We could also try and collapse in partially filled subtrees to take
* up space in this node.
*/
if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
struct assoc_array_node *parent, *grandparent;
struct assoc_array_ptr *ptr;
/* First of all, we need to know if this node has metadata so
* that we don't try collapsing if all the leaves are already
* here.
*/
has_meta = false;
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
ptr = node->slots[i];
if (assoc_array_ptr_is_meta(ptr)) {
has_meta = true;
break;
}
}
pr_devel("leaves: %ld [m=%d]\n",
node->nr_leaves_on_branch - 1, has_meta);
/* Look further up the tree to see if we can collapse this node
* into a more proximal node too.
*/
parent = node;
collapse_up:
pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);
ptr = parent->back_pointer;
if (!ptr)
goto do_collapse;
if (assoc_array_ptr_is_shortcut(ptr)) {
struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);
ptr = s->back_pointer;
if (!ptr)
goto do_collapse;
}
grandparent = assoc_array_ptr_to_node(ptr);
if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
parent = grandparent;
goto collapse_up;
}
do_collapse:
/* There's no point collapsing if the original node has no meta
* pointers to discard and if we didn't merge into one of that
* node's ancestry.
*/
if (has_meta || parent != node) {
node = parent;
/* Create a new node to collapse into */
new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
if (!new_n0)
goto enomem;
edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
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;
edit->adjust_count_on = new_n0;
collapse.node = new_n0;
collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);
collapse.slot = 0;
assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),
node->back_pointer,
assoc_array_delete_collapse_iterator,
&collapse);
pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);
BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);
if (!node->back_pointer) {
edit->set[1].ptr = &array->root;
} else if (assoc_array_ptr_is_leaf(node->back_pointer)) {
BUG();
} else if (assoc_array_ptr_is_node(node->back_pointer)) {
struct assoc_array_node *p =
assoc_array_ptr_to_node(node->back_pointer);
edit->set[1].ptr = &p->slots[node->parent_slot];
} else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {
struct assoc_array_shortcut *s =
assoc_array_ptr_to_shortcut(node->back_pointer);
edit->set[1].ptr = &s->next_node;
}
edit->set[1].to = assoc_array_node_to_ptr(new_n0);
edit->excised_subtree = assoc_array_node_to_ptr(node);
}
}
return edit;
enomem:
/* Clean up after an out of memory error */
pr_devel("enomem\n");
assoc_array_cancel_edit(edit);
return ERR_PTR(-ENOMEM);
}
/**
* assoc_array_clear - Script deletion of all objects from an associative array
* @array: The array to clear.
* @ops: The operations to use.
*
* Precalculate and preallocate a script for the deletion of all the objects
* from 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 if there are objects to be
* deleted, NULL if there are no objects in the array 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_clear(struct assoc_array *array,
const struct assoc_array_ops *ops)
{
struct assoc_array_edit *edit;
pr_devel("-->%s()\n", __func__);
if (!array->root)
return NULL;
edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
if (!edit)
return ERR_PTR(-ENOMEM);
edit->array = array;
edit->ops = ops;
edit->set[1].ptr = &array->root;
edit->set[1].to = NULL;
edit->excised_subtree = array->root;
edit->ops_for_excised_subtree = ops;
pr_devel("all gone\n");
return edit;
}
/*
* Handle the deferred destruction after an applied edit.
*/
static void assoc_array_rcu_cleanup(struct rcu_head *head)
{
struct assoc_array_edit *edit =
container_of(head, struct assoc_array_edit, rcu);
int i;
pr_devel("-->%s()\n", __func__);
if (edit->dead_leaf)
edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));
for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)
if (edit->excised_meta[i])
kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));
if (edit->excised_subtree) {
BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));
if (assoc_array_ptr_is_node(edit->excised_subtree)) {
struct assoc_array_node *n =
assoc_array_ptr_to_node(edit->excised_subtree);
n->back_pointer = NULL;
} else {
struct assoc_array_shortcut *s =
assoc_array_ptr_to_shortcut(edit->excised_subtree);
s->back_pointer = NULL;
}
assoc_array_destroy_subtree(edit->excised_subtree,
edit->ops_for_excised_subtree);
}
kfree(edit);
}
/**
* assoc_array_apply_edit - Apply an edit script to an associative array
* @edit: The script to apply.
*
* Apply an edit script to an associative array to effect an insertion,
* deletion or clearance. As the edit script includes preallocated memory,
* this is guaranteed not to fail.
*
* The edit script, dead objects and dead metadata will be scheduled for
* destruction after an RCU grace period to permit those doing read-only
* accesses on the array to continue to do so under the RCU read lock whilst
* the edit is taking place.
*/
void assoc_array_apply_edit(struct assoc_array_edit *edit)
{
struct assoc_array_shortcut *shortcut;
struct assoc_array_node *node;
struct assoc_array_ptr *ptr;
int i;
pr_devel("-->%s()\n", __func__);
smp_wmb();
if (edit->leaf_p)
*edit->leaf_p = edit->leaf;
smp_wmb();
for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)
if (edit->set_parent_slot[i].p)
*edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;
smp_wmb();
for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)
if (edit->set_backpointers[i])
*edit->set_backpointers[i] = edit->set_backpointers_to;
smp_wmb();
for (i = 0; i < ARRAY_SIZE(edit->set); i++)
if (edit->set[i].ptr)
*edit->set[i].ptr = edit->set[i].to;
if (edit->array->root == NULL) {
edit->array->nr_leaves_on_tree = 0;
} else if (edit->adjust_count_on) {
node = edit->adjust_count_on;
for (;;) {
node->nr_leaves_on_branch += edit->adjust_count_by;
ptr = node->back_pointer;
if (!ptr)
break;
if (assoc_array_ptr_is_shortcut(ptr)) {
shortcut = assoc_array_ptr_to_shortcut(ptr);
ptr = shortcut->back_pointer;
if (!ptr)
break;
}
BUG_ON(!assoc_array_ptr_is_node(ptr));
node = assoc_array_ptr_to_node(ptr);
}
edit->array->nr_leaves_on_tree += edit->adjust_count_by;
}
call_rcu(&edit->rcu, assoc_array_rcu_cleanup);
}
/**
* assoc_array_cancel_edit - Discard an edit script.
* @edit: The script to discard.
*
* Free an edit script and all the preallocated data it holds without making
* any changes to the associative array it was intended for.
*
* NOTE! In the case of an insertion script, this does _not_ release the leaf
* that was to be inserted. That is left to the caller.
*/
void assoc_array_cancel_edit(struct assoc_array_edit *edit)
{
struct assoc_array_ptr *ptr;
int i;
pr_devel("-->%s()\n", __func__);
/* Clean up after an out of memory error */
for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {
ptr = edit->new_meta[i];
if (ptr) {
if (assoc_array_ptr_is_node(ptr))
kfree(assoc_array_ptr_to_node(ptr));
else
kfree(assoc_array_ptr_to_shortcut(ptr));
}
}
kfree(edit);
}
/**
* assoc_array_gc - Garbage collect an associative array.
* @array: The array to clean.
* @ops: The operations to use.
* @iterator: A callback function to pass judgement on each object.
* @iterator_data: Private data for the callback function.
*
* Collect garbage from an associative array and pack down the internal tree to
* save memory.
*
* The iterator function is asked to pass judgement upon each object in the
* array. If it returns false, the object is discard and if it returns true,
* the object is kept. If it returns true, it must increment the object's
* usage count (or whatever it needs to do to retain it) before returning.
*
* This function returns 0 if successful or -ENOMEM if out of memory. In the
* latter case, the array is not changed.
*
* 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.
*/
int assoc_array_gc(struct assoc_array *array,
const struct assoc_array_ops *ops,
bool (*iterator)(void *object, void *iterator_data),
void *iterator_data)
{
struct assoc_array_shortcut *shortcut, *new_s;
struct assoc_array_node *node, *new_n;
struct assoc_array_edit *edit;
struct assoc_array_ptr *cursor, *ptr;
struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;
unsigned long nr_leaves_on_tree;
bool retained;
int keylen, slot, nr_free, next_slot, i;
pr_devel("-->%s()\n", __func__);
if (!array->root)
return 0;
edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
if (!edit)
return -ENOMEM;
edit->array = array;
edit->ops = ops;
edit->ops_for_excised_subtree = ops;
edit->set[0].ptr = &array->root;
edit->excised_subtree = array->root;
new_root = new_parent = NULL;
new_ptr_pp = &new_root;
cursor = array->root;
descend:
/* If this point is a shortcut, then we need to duplicate it and
* advance the target cursor.
*/
if (assoc_array_ptr_is_shortcut(cursor)) {
shortcut = assoc_array_ptr_to_shortcut(cursor);
keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
new_s = kmalloc(struct_size(new_s, index_key, keylen),
GFP_KERNEL);
if (!new_s)
goto enomem;
pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
memcpy(new_s, shortcut, struct_size(new_s, index_key, keylen));
new_s->back_pointer = new_parent;
new_s->parent_slot = shortcut->parent_slot;
*new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
new_ptr_pp = &new_s->next_node;
cursor = shortcut->next_node;
}
/* Duplicate the node at this position */
node = assoc_array_ptr_to_node(cursor);
new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
if (!new_n)
goto enomem;
pr_devel("dup node %p -> %p\n", node, new_n);
new_n->back_pointer = new_parent;
new_n->parent_slot = node->parent_slot;
*new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);
new_ptr_pp = NULL;
slot = 0;
continue_node:
/* Filter across any leaves and gc any subtrees */
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = node->slots[slot];
if (!ptr)
continue;
if (assoc_array_ptr_is_leaf(ptr)) {
if (iterator(assoc_array_ptr_to_leaf(ptr),
iterator_data))
/* The iterator will have done any reference
* counting on the object for us.
*/
new_n->slots[slot] = ptr;
continue;
}
new_ptr_pp = &new_n->slots[slot];
cursor = ptr;
goto descend;
}
retry_compress:
pr_devel("-- compress node %p --\n", new_n);
/* Count up the number of empty slots in this node and work out the
* subtree leaf count.
*/
new_n->nr_leaves_on_branch = 0;
nr_free = 0;
for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = new_n->slots[slot];
if (!ptr)
nr_free++;
else if (assoc_array_ptr_is_leaf(ptr))
new_n->nr_leaves_on_branch++;
}
pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);
/* See what we can fold in */
retained = false;
next_slot = 0;
for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
struct assoc_array_shortcut *s;
struct assoc_array_node *child;
ptr = new_n->slots[slot];
if (!ptr || assoc_array_ptr_is_leaf(ptr))
continue;
s = NULL;
if (assoc_array_ptr_is_shortcut(ptr)) {
s = assoc_array_ptr_to_shortcut(ptr);
ptr = s->next_node;
}
child = assoc_array_ptr_to_node(ptr);
new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;
if (child->nr_leaves_on_branch <= nr_free + 1) {
/* Fold the child node into this one */
pr_devel("[%d] fold node %lu/%d [nx %d]\n",
slot, child->nr_leaves_on_branch, nr_free + 1,
next_slot);
/* We would already have reaped an intervening shortcut
* on the way back up the tree.
*/
BUG_ON(s);
new_n->slots[slot] = NULL;
nr_free++;
if (slot < next_slot)
next_slot = slot;
for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
struct assoc_array_ptr *p = child->slots[i];
if (!p)
continue;
BUG_ON(assoc_array_ptr_is_meta(p));
while (new_n->slots[next_slot])
next_slot++;
BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);
new_n->slots[next_slot++] = p;
nr_free--;
}
kfree(child);
} else {
pr_devel("[%d] retain node %lu/%d [nx %d]\n",
slot, child->nr_leaves_on_branch, nr_free + 1,
next_slot);
retained = true;
}
}
if (retained && new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
pr_devel("internal nodes remain despite enough space, retrying\n");
goto retry_compress;
}
pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);
nr_leaves_on_tree = new_n->nr_leaves_on_branch;
/* Excise this node if it is singly occupied by a shortcut */
if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {
for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)
if ((ptr = new_n->slots[slot]))
break;
if (assoc_array_ptr_is_meta(ptr) &&
assoc_array_ptr_is_shortcut(ptr)) {
pr_devel("excise node %p with 1 shortcut\n", new_n);
new_s = assoc_array_ptr_to_shortcut(ptr);
new_parent = new_n->back_pointer;
slot = new_n->parent_slot;
kfree(new_n);
if (!new_parent) {
new_s->back_pointer = NULL;
new_s->parent_slot = 0;
new_root = ptr;
goto gc_complete;
}
if (assoc_array_ptr_is_shortcut(new_parent)) {
/* We can discard any preceding shortcut also */
struct assoc_array_shortcut *s =
assoc_array_ptr_to_shortcut(new_parent);
pr_devel("excise preceding shortcut\n");
new_parent = new_s->back_pointer = s->back_pointer;
slot = new_s->parent_slot = s->parent_slot;
kfree(s);
if (!new_parent) {
new_s->back_pointer = NULL;
new_s->parent_slot = 0;
new_root = ptr;
goto gc_complete;
}
}
new_s->back_pointer = new_parent;
new_s->parent_slot = slot;
new_n = assoc_array_ptr_to_node(new_parent);
new_n->slots[slot] = ptr;
goto ascend_old_tree;
}
}
/* Excise any shortcuts we might encounter that point to nodes that
* only contain leaves.
*/
ptr = new_n->back_pointer;
if (!ptr)
goto gc_complete;
if (assoc_array_ptr_is_shortcut(ptr)) {
new_s = assoc_array_ptr_to_shortcut(ptr);
new_parent = new_s->back_pointer;
slot = new_s->parent_slot;
if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
struct assoc_array_node *n;
pr_devel("excise shortcut\n");
new_n->back_pointer = new_parent;
new_n->parent_slot = slot;
kfree(new_s);
if (!new_parent) {
new_root = assoc_array_node_to_ptr(new_n);
goto gc_complete;
}
n = assoc_array_ptr_to_node(new_parent);
n->slots[slot] = assoc_array_node_to_ptr(new_n);
}
} else {
new_parent = ptr;
}
new_n = assoc_array_ptr_to_node(new_parent);
ascend_old_tree:
ptr = node->back_pointer;
if (assoc_array_ptr_is_shortcut(ptr)) {
shortcut = assoc_array_ptr_to_shortcut(ptr);
slot = shortcut->parent_slot;
cursor = shortcut->back_pointer;
if (!cursor)
goto gc_complete;
} else {
slot = node->parent_slot;
cursor = ptr;
}
BUG_ON(!cursor);
node = assoc_array_ptr_to_node(cursor);
slot++;
goto continue_node;
gc_complete:
edit->set[0].to = new_root;
assoc_array_apply_edit(edit);
array->nr_leaves_on_tree = nr_leaves_on_tree;
return 0;
enomem:
pr_devel("enomem\n");
assoc_array_destroy_subtree(new_root, edit->ops);
kfree(edit);
return -ENOMEM;
}
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