// 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 (dhowells@redhat.com)
*/ //#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.
*/ staticint assoc_array_subtree_iterate(conststruct assoc_array_ptr *root, conststruct assoc_array_ptr *stop, int (*iterator)(constvoid *leaf, void *iterator_data), void *iterator_data)
{ conststruct assoc_array_shortcut *shortcut; conststruct assoc_array_node *node; conststruct assoc_array_ptr *cursor, *ptr, *parent; unsignedlong 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 |= (unsignedlong)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;
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;
/* 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(conststruct assoc_array *array, int (*iterator)(constvoid *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);
}
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; unsignedlong sc_segments; unsignedlong dissimilarity;
} wrong_shortcut;
};
/* * Navigate through the internal tree looking for the closest node to the key.
*/ staticenum assoc_array_walk_status
assoc_array_walk(conststruct assoc_array *array, conststruct assoc_array_ops *ops, constvoid *index_key, struct assoc_array_walk_result *result)
{ struct assoc_array_shortcut *shortcut; struct assoc_array_node *node; struct assoc_array_ptr *cursor, *ptr; unsignedlong sc_segments, dissimilarity; unsignedlong segments; int level, sc_level, next_sc_level; int slot;
/* 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;
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_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(conststruct assoc_array *array, conststruct assoc_array_ops *ops, constvoid *index_key)
{ struct assoc_array_walk_result result; conststruct assoc_array_node *node; conststruct assoc_array_ptr *ptr; constvoid *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.
*/ staticvoid assoc_array_destroy_subtree(struct assoc_array_ptr *root, conststruct 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 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, conststruct assoc_array_ops *ops)
{
assoc_array_destroy_subtree(array->root, ops);
array->root = NULL;
}
/* * Handle insertion into an empty tree.
*/ staticbool 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) returnfalse;
/* 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__); returntrue;
}
}
/* 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__); returntrue;
}
/* 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) returnfalse;
edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n1) returnfalse;
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;
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 */
/* 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];
}
}
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);
/* 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;
}
/* 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);
/* 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) returnfalse;
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;
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;
/* 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;
/* 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__); returntrue;
}
/** * 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, conststruct assoc_array_ops *ops, constvoid *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));
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);
}
/** * 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, conststruct assoc_array_ops *ops, constvoid *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;
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;
}
/* 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;
}
}
/* 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;
}
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);
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, conststruct assoc_array_ops *ops)
{ struct assoc_array_edit *edit;
/* * Handle the deferred destruction after an applied edit.
*/ staticvoid 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]));
/** * 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;
/** * 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, conststruct 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; unsignedlong nr_leaves_on_tree; bool retained; int keylen, slot, nr_free, next_slot, i;
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;
}
/* 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++; elseif (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;
}
/* 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_shortcut(new_parent)) { /* We can discard any preceding shortcut also */ struct assoc_array_shortcut *s =
assoc_array_ptr_to_shortcut(new_parent);
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