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1// SPDX-License-Identifier: GPL-2.0-or-later2/* Generic associative array implementation.3 *4 * See Documentation/core-api/assoc_array.rst for information.5 *6 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.7 * Written by David Howells (dhowells@redhat.com)8 */9//#define DEBUG10#include <linux/rcupdate.h>11#include <linux/slab.h>12#include <linux/err.h>13#include <linux/assoc_array_priv.h>14 15/*16 * Iterate over an associative array. The caller must hold the RCU read lock17 * or better.18 */19static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,20 const struct assoc_array_ptr *stop,21 int (*iterator)(const void *leaf,22 void *iterator_data),23 void *iterator_data)24{25 const struct assoc_array_shortcut *shortcut;26 const struct assoc_array_node *node;27 const struct assoc_array_ptr *cursor, *ptr, *parent;28 unsigned long has_meta;29 int slot, ret;30 31 cursor = root;32 33begin_node:34 if (assoc_array_ptr_is_shortcut(cursor)) {35 /* Descend through a shortcut */36 shortcut = assoc_array_ptr_to_shortcut(cursor);37 cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */38 }39 40 node = assoc_array_ptr_to_node(cursor);41 slot = 0;42 43 /* We perform two passes of each node.44 *45 * The first pass does all the leaves in this node. This means we46 * don't miss any leaves if the node is split up by insertion whilst47 * we're iterating over the branches rooted here (we may, however, see48 * some leaves twice).49 */50 has_meta = 0;51 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {52 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */53 has_meta |= (unsigned long)ptr;54 if (ptr && assoc_array_ptr_is_leaf(ptr)) {55 /* We need a barrier between the read of the pointer,56 * which is supplied by the above READ_ONCE().57 */58 /* Invoke the callback */59 ret = iterator(assoc_array_ptr_to_leaf(ptr),60 iterator_data);61 if (ret)62 return ret;63 }64 }65 66 /* The second pass attends to all the metadata pointers. If we follow67 * one of these we may find that we don't come back here, but rather go68 * back to a replacement node with the leaves in a different layout.69 *70 * We are guaranteed to make progress, however, as the slot number for71 * a particular portion of the key space cannot change - and we72 * continue at the back pointer + 1.73 */74 if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))75 goto finished_node;76 slot = 0;77 78continue_node:79 node = assoc_array_ptr_to_node(cursor);80 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {81 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */82 if (assoc_array_ptr_is_meta(ptr)) {83 cursor = ptr;84 goto begin_node;85 }86 }87 88finished_node:89 /* Move up to the parent (may need to skip back over a shortcut) */90 parent = READ_ONCE(node->back_pointer); /* Address dependency. */91 slot = node->parent_slot;92 if (parent == stop)93 return 0;94 95 if (assoc_array_ptr_is_shortcut(parent)) {96 shortcut = assoc_array_ptr_to_shortcut(parent);97 cursor = parent;98 parent = READ_ONCE(shortcut->back_pointer); /* Address dependency. */99 slot = shortcut->parent_slot;100 if (parent == stop)101 return 0;102 }103 104 /* Ascend to next slot in parent node */105 cursor = parent;106 slot++;107 goto continue_node;108}109 110/**111 * assoc_array_iterate - Pass all objects in the array to a callback112 * @array: The array to iterate over.113 * @iterator: The callback function.114 * @iterator_data: Private data for the callback function.115 *116 * Iterate over all the objects in an associative array. Each one will be117 * presented to the iterator function.118 *119 * If the array is being modified concurrently with the iteration then it is120 * possible that some objects in the array will be passed to the iterator121 * callback more than once - though every object should be passed at least122 * once. If this is undesirable then the caller must lock against modification123 * for the duration of this function.124 *125 * The function will return 0 if no objects were in the array or else it will126 * return the result of the last iterator function called. Iteration stops127 * immediately if any call to the iteration function results in a non-zero128 * return.129 *130 * The caller should hold the RCU read lock or better if concurrent131 * modification is possible.132 */133int assoc_array_iterate(const struct assoc_array *array,134 int (*iterator)(const void *object,135 void *iterator_data),136 void *iterator_data)137{138 struct assoc_array_ptr *root = READ_ONCE(array->root); /* Address dependency. */139 140 if (!root)141 return 0;142 return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data);143}144 145enum assoc_array_walk_status {146 assoc_array_walk_tree_empty,147 assoc_array_walk_found_terminal_node,148 assoc_array_walk_found_wrong_shortcut,149};150 151struct assoc_array_walk_result {152 struct {153 struct assoc_array_node *node; /* Node in which leaf might be found */154 int level;155 int slot;156 } terminal_node;157 struct {158 struct assoc_array_shortcut *shortcut;159 int level;160 int sc_level;161 unsigned long sc_segments;162 unsigned long dissimilarity;163 } wrong_shortcut;164};165 166/*167 * Navigate through the internal tree looking for the closest node to the key.168 */169static enum assoc_array_walk_status170assoc_array_walk(const struct assoc_array *array,171 const struct assoc_array_ops *ops,172 const void *index_key,173 struct assoc_array_walk_result *result)174{175 struct assoc_array_shortcut *shortcut;176 struct assoc_array_node *node;177 struct assoc_array_ptr *cursor, *ptr;178 unsigned long sc_segments, dissimilarity;179 unsigned long segments;180 int level, sc_level, next_sc_level;181 int slot;182 183 pr_devel("-->%s()\n", __func__);184 185 cursor = READ_ONCE(array->root); /* Address dependency. */186 if (!cursor)187 return assoc_array_walk_tree_empty;188 189 level = 0;190 191 /* Use segments from the key for the new leaf to navigate through the192 * internal tree, skipping through nodes and shortcuts that are on193 * route to the destination. Eventually we'll come to a slot that is194 * either empty or contains a leaf at which point we've found a node in195 * which the leaf we're looking for might be found or into which it196 * should be inserted.197 */198jumped:199 segments = ops->get_key_chunk(index_key, level);200 pr_devel("segments[%d]: %lx\n", level, segments);201 202 if (assoc_array_ptr_is_shortcut(cursor))203 goto follow_shortcut;204 205consider_node:206 node = assoc_array_ptr_to_node(cursor);207 slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);208 slot &= ASSOC_ARRAY_FAN_MASK;209 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */210 211 pr_devel("consider slot %x [ix=%d type=%lu]\n",212 slot, level, (unsigned long)ptr & 3);213 214 if (!assoc_array_ptr_is_meta(ptr)) {215 /* The node doesn't have a node/shortcut pointer in the slot216 * corresponding to the index key that we have to follow.217 */218 result->terminal_node.node = node;219 result->terminal_node.level = level;220 result->terminal_node.slot = slot;221 pr_devel("<--%s() = terminal_node\n", __func__);222 return assoc_array_walk_found_terminal_node;223 }224 225 if (assoc_array_ptr_is_node(ptr)) {226 /* There is a pointer to a node in the slot corresponding to227 * this index key segment, so we need to follow it.228 */229 cursor = ptr;230 level += ASSOC_ARRAY_LEVEL_STEP;231 if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0)232 goto consider_node;233 goto jumped;234 }235 236 /* There is a shortcut in the slot corresponding to the index key237 * segment. We follow the shortcut if its partial index key matches238 * this leaf's. Otherwise we need to split the shortcut.239 */240 cursor = ptr;241follow_shortcut:242 shortcut = assoc_array_ptr_to_shortcut(cursor);243 pr_devel("shortcut to %d\n", shortcut->skip_to_level);244 sc_level = level + ASSOC_ARRAY_LEVEL_STEP;245 BUG_ON(sc_level > shortcut->skip_to_level);246 247 do {248 /* Check the leaf against the shortcut's index key a word at a249 * time, trimming the final word (the shortcut stores the index250 * key completely from the root to the shortcut's target).251 */252 if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0)253 segments = ops->get_key_chunk(index_key, sc_level);254 255 sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT];256 dissimilarity = segments ^ sc_segments;257 258 if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) {259 /* Trim segments that are beyond the shortcut */260 int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK;261 dissimilarity &= ~(ULONG_MAX << shift);262 next_sc_level = shortcut->skip_to_level;263 } else {264 next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE;265 next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);266 }267 268 if (dissimilarity != 0) {269 /* This shortcut points elsewhere */270 result->wrong_shortcut.shortcut = shortcut;271 result->wrong_shortcut.level = level;272 result->wrong_shortcut.sc_level = sc_level;273 result->wrong_shortcut.sc_segments = sc_segments;274 result->wrong_shortcut.dissimilarity = dissimilarity;275 return assoc_array_walk_found_wrong_shortcut;276 }277 278 sc_level = next_sc_level;279 } while (sc_level < shortcut->skip_to_level);280 281 /* The shortcut matches the leaf's index to this point. */282 cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */283 if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) {284 level = sc_level;285 goto jumped;286 } else {287 level = sc_level;288 goto consider_node;289 }290}291 292/**293 * assoc_array_find - Find an object by index key294 * @array: The associative array to search.295 * @ops: The operations to use.296 * @index_key: The key to the object.297 *298 * Find an object in an associative array by walking through the internal tree299 * to the node that should contain the object and then searching the leaves300 * there. NULL is returned if the requested object was not found in the array.301 *302 * The caller must hold the RCU read lock or better.303 */304void *assoc_array_find(const struct assoc_array *array,305 const struct assoc_array_ops *ops,306 const void *index_key)307{308 struct assoc_array_walk_result result;309 const struct assoc_array_node *node;310 const struct assoc_array_ptr *ptr;311 const void *leaf;312 int slot;313 314 if (assoc_array_walk(array, ops, index_key, &result) !=315 assoc_array_walk_found_terminal_node)316 return NULL;317 318 node = result.terminal_node.node;319 320 /* If the target key is available to us, it's has to be pointed to by321 * the terminal node.322 */323 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {324 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */325 if (ptr && assoc_array_ptr_is_leaf(ptr)) {326 /* We need a barrier between the read of the pointer327 * and dereferencing the pointer - but only if we are328 * actually going to dereference it.329 */330 leaf = assoc_array_ptr_to_leaf(ptr);331 if (ops->compare_object(leaf, index_key))332 return (void *)leaf;333 }334 }335 336 return NULL;337}338 339/*340 * Destructively iterate over an associative array. The caller must prevent341 * other simultaneous accesses.342 */343static void assoc_array_destroy_subtree(struct assoc_array_ptr *root,344 const struct assoc_array_ops *ops)345{346 struct assoc_array_shortcut *shortcut;347 struct assoc_array_node *node;348 struct assoc_array_ptr *cursor, *parent = NULL;349 int slot = -1;350 351 pr_devel("-->%s()\n", __func__);352 353 cursor = root;354 if (!cursor) {355 pr_devel("empty\n");356 return;357 }358 359move_to_meta:360 if (assoc_array_ptr_is_shortcut(cursor)) {361 /* Descend through a shortcut */362 pr_devel("[%d] shortcut\n", slot);363 BUG_ON(!assoc_array_ptr_is_shortcut(cursor));364 shortcut = assoc_array_ptr_to_shortcut(cursor);365 BUG_ON(shortcut->back_pointer != parent);366 BUG_ON(slot != -1 && shortcut->parent_slot != slot);367 parent = cursor;368 cursor = shortcut->next_node;369 slot = -1;370 BUG_ON(!assoc_array_ptr_is_node(cursor));371 }372 373 pr_devel("[%d] node\n", slot);374 node = assoc_array_ptr_to_node(cursor);375 BUG_ON(node->back_pointer != parent);376 BUG_ON(slot != -1 && node->parent_slot != slot);377 slot = 0;378 379continue_node:380 pr_devel("Node %p [back=%p]\n", node, node->back_pointer);381 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {382 struct assoc_array_ptr *ptr = node->slots[slot];383 if (!ptr)384 continue;385 if (assoc_array_ptr_is_meta(ptr)) {386 parent = cursor;387 cursor = ptr;388 goto move_to_meta;389 }390 391 if (ops) {392 pr_devel("[%d] free leaf\n", slot);393 ops->free_object(assoc_array_ptr_to_leaf(ptr));394 }395 }396 397 parent = node->back_pointer;398 slot = node->parent_slot;399 pr_devel("free node\n");400 kfree(node);401 if (!parent)402 return; /* Done */403 404 /* Move back up to the parent (may need to free a shortcut on405 * the way up) */406 if (assoc_array_ptr_is_shortcut(parent)) {407 shortcut = assoc_array_ptr_to_shortcut(parent);408 BUG_ON(shortcut->next_node != cursor);409 cursor = parent;410 parent = shortcut->back_pointer;411 slot = shortcut->parent_slot;412 pr_devel("free shortcut\n");413 kfree(shortcut);414 if (!parent)415 return;416 417 BUG_ON(!assoc_array_ptr_is_node(parent));418 }419 420 /* Ascend to next slot in parent node */421 pr_devel("ascend to %p[%d]\n", parent, slot);422 cursor = parent;423 node = assoc_array_ptr_to_node(cursor);424 slot++;425 goto continue_node;426}427 428/**429 * assoc_array_destroy - Destroy an associative array430 * @array: The array to destroy.431 * @ops: The operations to use.432 *433 * Discard all metadata and free all objects in an associative array. The434 * array will be empty and ready to use again upon completion. This function435 * cannot fail.436 *437 * The caller must prevent all other accesses whilst this takes place as no438 * attempt is made to adjust pointers gracefully to permit RCU readlock-holding439 * accesses to continue. On the other hand, no memory allocation is required.440 */441void assoc_array_destroy(struct assoc_array *array,442 const struct assoc_array_ops *ops)443{444 assoc_array_destroy_subtree(array->root, ops);445 array->root = NULL;446}447 448/*449 * Handle insertion into an empty tree.450 */451static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit)452{453 struct assoc_array_node *new_n0;454 455 pr_devel("-->%s()\n", __func__);456 457 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);458 if (!new_n0)459 return false;460 461 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);462 edit->leaf_p = &new_n0->slots[0];463 edit->adjust_count_on = new_n0;464 edit->set[0].ptr = &edit->array->root;465 edit->set[0].to = assoc_array_node_to_ptr(new_n0);466 467 pr_devel("<--%s() = ok [no root]\n", __func__);468 return true;469}470 471/*472 * Handle insertion into a terminal node.473 */474static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,475 const struct assoc_array_ops *ops,476 const void *index_key,477 struct assoc_array_walk_result *result)478{479 struct assoc_array_shortcut *shortcut, *new_s0;480 struct assoc_array_node *node, *new_n0, *new_n1, *side;481 struct assoc_array_ptr *ptr;482 unsigned long dissimilarity, base_seg, blank;483 size_t keylen;484 bool have_meta;485 int level, diff;486 int slot, next_slot, free_slot, i, j;487 488 node = result->terminal_node.node;489 level = result->terminal_node.level;490 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot;491 492 pr_devel("-->%s()\n", __func__);493 494 /* We arrived at a node which doesn't have an onward node or shortcut495 * pointer that we have to follow. This means that (a) the leaf we496 * want must go here (either by insertion or replacement) or (b) we497 * need to split this node and insert in one of the fragments.498 */499 free_slot = -1;500 501 /* Firstly, we have to check the leaves in this node to see if there's502 * a matching one we should replace in place.503 */504 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {505 ptr = node->slots[i];506 if (!ptr) {507 free_slot = i;508 continue;509 }510 if (assoc_array_ptr_is_leaf(ptr) &&511 ops->compare_object(assoc_array_ptr_to_leaf(ptr),512 index_key)) {513 pr_devel("replace in slot %d\n", i);514 edit->leaf_p = &node->slots[i];515 edit->dead_leaf = node->slots[i];516 pr_devel("<--%s() = ok [replace]\n", __func__);517 return true;518 }519 }520 521 /* If there is a free slot in this node then we can just insert the522 * leaf here.523 */524 if (free_slot >= 0) {525 pr_devel("insert in free slot %d\n", free_slot);526 edit->leaf_p = &node->slots[free_slot];527 edit->adjust_count_on = node;528 pr_devel("<--%s() = ok [insert]\n", __func__);529 return true;530 }531 532 /* The node has no spare slots - so we're either going to have to split533 * it or insert another node before it.534 *535 * Whatever, we're going to need at least two new nodes - so allocate536 * those now. We may also need a new shortcut, but we deal with that537 * when we need it.538 */539 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);540 if (!new_n0)541 return false;542 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);543 new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);544 if (!new_n1)545 return false;546 edit->new_meta[1] = assoc_array_node_to_ptr(new_n1);547 548 /* We need to find out how similar the leaves are. */549 pr_devel("no spare slots\n");550 have_meta = false;551 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {552 ptr = node->slots[i];553 if (assoc_array_ptr_is_meta(ptr)) {554 edit->segment_cache[i] = 0xff;555 have_meta = true;556 continue;557 }558 base_seg = ops->get_object_key_chunk(559 assoc_array_ptr_to_leaf(ptr), level);560 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;561 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;562 }563 564 if (have_meta) {565 pr_devel("have meta\n");566 goto split_node;567 }568 569 /* The node contains only leaves */570 dissimilarity = 0;571 base_seg = edit->segment_cache[0];572 for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++)573 dissimilarity |= edit->segment_cache[i] ^ base_seg;574 575 pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity);576 577 if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) {578 /* The old leaves all cluster in the same slot. We will need579 * to insert a shortcut if the new node wants to cluster with them.580 */581 if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0)582 goto all_leaves_cluster_together;583 584 /* Otherwise all the old leaves cluster in the same slot, but585 * the new leaf wants to go into a different slot - so we586 * create a new node (n0) to hold the new leaf and a pointer to587 * a new node (n1) holding all the old leaves.588 *589 * This can be done by falling through to the node splitting590 * path.591 */592 pr_devel("present leaves cluster but not new leaf\n");593 }594 595split_node:596 pr_devel("split node\n");597 598 /* We need to split the current node. The node must contain anything599 * from a single leaf (in the one leaf case, this leaf will cluster600 * with the new leaf) and the rest meta-pointers, to all leaves, some601 * of which may cluster.602 *603 * It won't contain the case in which all the current leaves plus the604 * new leaves want to cluster in the same slot.605 *606 * We need to expel at least two leaves out of a set consisting of the607 * leaves in the node and the new leaf. The current meta pointers can608 * just be copied as they shouldn't cluster with any of the leaves.609 *610 * We need a new node (n0) to replace the current one and a new node to611 * take the expelled nodes (n1).612 */613 edit->set[0].to = assoc_array_node_to_ptr(new_n0);614 new_n0->back_pointer = node->back_pointer;615 new_n0->parent_slot = node->parent_slot;616 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);617 new_n1->parent_slot = -1; /* Need to calculate this */618 619do_split_node:620 pr_devel("do_split_node\n");621 622 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;623 new_n1->nr_leaves_on_branch = 0;624 625 /* Begin by finding two matching leaves. There have to be at least two626 * that match - even if there are meta pointers - because any leaf that627 * would match a slot with a meta pointer in it must be somewhere628 * behind that meta pointer and cannot be here. Further, given N629 * remaining leaf slots, we now have N+1 leaves to go in them.630 */631 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {632 slot = edit->segment_cache[i];633 if (slot != 0xff)634 for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)635 if (edit->segment_cache[j] == slot)636 goto found_slot_for_multiple_occupancy;637 }638found_slot_for_multiple_occupancy:639 pr_devel("same slot: %x %x [%02x]\n", i, j, slot);640 BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);641 BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);642 BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);643 644 new_n1->parent_slot = slot;645 646 /* Metadata pointers cannot change slot */647 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)648 if (assoc_array_ptr_is_meta(node->slots[i]))649 new_n0->slots[i] = node->slots[i];650 else651 new_n0->slots[i] = NULL;652 BUG_ON(new_n0->slots[slot] != NULL);653 new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);654 655 /* Filter the leaf pointers between the new nodes */656 free_slot = -1;657 next_slot = 0;658 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {659 if (assoc_array_ptr_is_meta(node->slots[i]))660 continue;661 if (edit->segment_cache[i] == slot) {662 new_n1->slots[next_slot++] = node->slots[i];663 new_n1->nr_leaves_on_branch++;664 } else {665 do {666 free_slot++;667 } while (new_n0->slots[free_slot] != NULL);668 new_n0->slots[free_slot] = node->slots[i];669 }670 }671 672 pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);673 674 if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {675 do {676 free_slot++;677 } while (new_n0->slots[free_slot] != NULL);678 edit->leaf_p = &new_n0->slots[free_slot];679 edit->adjust_count_on = new_n0;680 } else {681 edit->leaf_p = &new_n1->slots[next_slot++];682 edit->adjust_count_on = new_n1;683 }684 685 BUG_ON(next_slot <= 1);686 687 edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);688 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {689 if (edit->segment_cache[i] == 0xff) {690 ptr = node->slots[i];691 BUG_ON(assoc_array_ptr_is_leaf(ptr));692 if (assoc_array_ptr_is_node(ptr)) {693 side = assoc_array_ptr_to_node(ptr);694 edit->set_backpointers[i] = &side->back_pointer;695 } else {696 shortcut = assoc_array_ptr_to_shortcut(ptr);697 edit->set_backpointers[i] = &shortcut->back_pointer;698 }699 }700 }701 702 ptr = node->back_pointer;703 if (!ptr)704 edit->set[0].ptr = &edit->array->root;705 else if (assoc_array_ptr_is_node(ptr))706 edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];707 else708 edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;709 edit->excised_meta[0] = assoc_array_node_to_ptr(node);710 pr_devel("<--%s() = ok [split node]\n", __func__);711 return true;712 713all_leaves_cluster_together:714 /* All the leaves, new and old, want to cluster together in this node715 * in the same slot, so we have to replace this node with a shortcut to716 * skip over the identical parts of the key and then place a pair of717 * nodes, one inside the other, at the end of the shortcut and718 * distribute the keys between them.719 *720 * Firstly we need to work out where the leaves start diverging as a721 * bit position into their keys so that we know how big the shortcut722 * needs to be.723 *724 * We only need to make a single pass of N of the N+1 leaves because if725 * any keys differ between themselves at bit X then at least one of726 * them must also differ with the base key at bit X or before.727 */728 pr_devel("all leaves cluster together\n");729 diff = INT_MAX;730 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {731 int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]),732 index_key);733 if (x < diff) {734 BUG_ON(x < 0);735 diff = x;736 }737 }738 BUG_ON(diff == INT_MAX);739 BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);740 741 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);742 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;743 744 new_s0 = kzalloc(struct_size(new_s0, index_key, keylen), GFP_KERNEL);745 if (!new_s0)746 return false;747 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);748 749 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);750 new_s0->back_pointer = node->back_pointer;751 new_s0->parent_slot = node->parent_slot;752 new_s0->next_node = assoc_array_node_to_ptr(new_n0);753 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);754 new_n0->parent_slot = 0;755 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);756 new_n1->parent_slot = -1; /* Need to calculate this */757 758 new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;759 pr_devel("skip_to_level = %d [diff %d]\n", level, diff);760 BUG_ON(level <= 0);761 762 for (i = 0; i < keylen; i++)763 new_s0->index_key[i] =764 ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);765 766 if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) {767 blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);768 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);769 new_s0->index_key[keylen - 1] &= ~blank;770 }771 772 /* This now reduces to a node splitting exercise for which we'll need773 * to regenerate the disparity table.774 */775 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {776 ptr = node->slots[i];777 base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),778 level);779 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;780 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;781 }782 783 base_seg = ops->get_key_chunk(index_key, level);784 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;785 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;786 goto do_split_node;787}788 789/*790 * Handle insertion into the middle of a shortcut.791 */792static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,793 const struct assoc_array_ops *ops,794 struct assoc_array_walk_result *result)795{796 struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;797 struct assoc_array_node *node, *new_n0, *side;798 unsigned long sc_segments, dissimilarity, blank;799 size_t keylen;800 int level, sc_level, diff;801 int sc_slot;802 803 shortcut = result->wrong_shortcut.shortcut;804 level = result->wrong_shortcut.level;805 sc_level = result->wrong_shortcut.sc_level;806 sc_segments = result->wrong_shortcut.sc_segments;807 dissimilarity = result->wrong_shortcut.dissimilarity;808 809 pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",810 __func__, level, dissimilarity, sc_level);811 812 /* We need to split a shortcut and insert a node between the two813 * pieces. Zero-length pieces will be dispensed with entirely.814 *815 * First of all, we need to find out in which level the first816 * difference was.817 */818 diff = __ffs(dissimilarity);819 diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;820 diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;821 pr_devel("diff=%d\n", diff);822 823 if (!shortcut->back_pointer) {824 edit->set[0].ptr = &edit->array->root;825 } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {826 node = assoc_array_ptr_to_node(shortcut->back_pointer);827 edit->set[0].ptr = &node->slots[shortcut->parent_slot];828 } else {829 BUG();830 }831 832 edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);833 834 /* Create a new node now since we're going to need it anyway */835 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);836 if (!new_n0)837 return false;838 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);839 edit->adjust_count_on = new_n0;840 841 /* Insert a new shortcut before the new node if this segment isn't of842 * zero length - otherwise we just connect the new node directly to the843 * parent.844 */845 level += ASSOC_ARRAY_LEVEL_STEP;846 if (diff > level) {847 pr_devel("pre-shortcut %d...%d\n", level, diff);848 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);849 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;850 851 new_s0 = kzalloc(struct_size(new_s0, index_key, keylen),852 GFP_KERNEL);853 if (!new_s0)854 return false;855 edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);856 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);857 new_s0->back_pointer = shortcut->back_pointer;858 new_s0->parent_slot = shortcut->parent_slot;859 new_s0->next_node = assoc_array_node_to_ptr(new_n0);860 new_s0->skip_to_level = diff;861 862 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);863 new_n0->parent_slot = 0;864 865 memcpy(new_s0->index_key, shortcut->index_key,866 flex_array_size(new_s0, index_key, keylen));867 868 blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);869 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);870 new_s0->index_key[keylen - 1] &= ~blank;871 } else {872 pr_devel("no pre-shortcut\n");873 edit->set[0].to = assoc_array_node_to_ptr(new_n0);874 new_n0->back_pointer = shortcut->back_pointer;875 new_n0->parent_slot = shortcut->parent_slot;876 }877 878 side = assoc_array_ptr_to_node(shortcut->next_node);879 new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;880 881 /* We need to know which slot in the new node is going to take a882 * metadata pointer.883 */884 sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);885 sc_slot &= ASSOC_ARRAY_FAN_MASK;886 887 pr_devel("new slot %lx >> %d -> %d\n",888 sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);889 890 /* Determine whether we need to follow the new node with a replacement891 * for the current shortcut. We could in theory reuse the current892 * shortcut if its parent slot number doesn't change - but that's a893 * 1-in-16 chance so not worth expending the code upon.894 */895 level = diff + ASSOC_ARRAY_LEVEL_STEP;896 if (level < shortcut->skip_to_level) {897 pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);898 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);899 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;900 901 new_s1 = kzalloc(struct_size(new_s1, index_key, keylen),902 GFP_KERNEL);903 if (!new_s1)904 return false;905 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);906 907 new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);908 new_s1->parent_slot = sc_slot;909 new_s1->next_node = shortcut->next_node;910 new_s1->skip_to_level = shortcut->skip_to_level;911 912 new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);913 914 memcpy(new_s1->index_key, shortcut->index_key,915 flex_array_size(new_s1, index_key, keylen));916 917 edit->set[1].ptr = &side->back_pointer;918 edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);919 } else {920 pr_devel("no post-shortcut\n");921 922 /* We don't have to replace the pointed-to node as long as we923 * use memory barriers to make sure the parent slot number is924 * changed before the back pointer (the parent slot number is925 * irrelevant to the old parent shortcut).926 */927 new_n0->slots[sc_slot] = shortcut->next_node;928 edit->set_parent_slot[0].p = &side->parent_slot;929 edit->set_parent_slot[0].to = sc_slot;930 edit->set[1].ptr = &side->back_pointer;931 edit->set[1].to = assoc_array_node_to_ptr(new_n0);932 }933 934 /* Install the new leaf in a spare slot in the new node. */935 if (sc_slot == 0)936 edit->leaf_p = &new_n0->slots[1];937 else938 edit->leaf_p = &new_n0->slots[0];939 940 pr_devel("<--%s() = ok [split shortcut]\n", __func__);941 return true;942}943 944/**945 * assoc_array_insert - Script insertion of an object into an associative array946 * @array: The array to insert into.947 * @ops: The operations to use.948 * @index_key: The key to insert at.949 * @object: The object to insert.950 *951 * Precalculate and preallocate a script for the insertion or replacement of an952 * object in an associative array. This results in an edit script that can953 * either be applied or cancelled.954 *955 * The function returns a pointer to an edit script or -ENOMEM.956 *957 * The caller should lock against other modifications and must continue to hold958 * the lock until assoc_array_apply_edit() has been called.959 *960 * Accesses to the tree may take place concurrently with this function,961 * provided they hold the RCU read lock.962 */963struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,964 const struct assoc_array_ops *ops,965 const void *index_key,966 void *object)967{968 struct assoc_array_walk_result result;969 struct assoc_array_edit *edit;970 971 pr_devel("-->%s()\n", __func__);972 973 /* The leaf pointer we're given must not have the bottom bit set as we974 * use those for type-marking the pointer. NULL pointers are also not975 * allowed as they indicate an empty slot but we have to allow them976 * here as they can be updated later.977 */978 BUG_ON(assoc_array_ptr_is_meta(object));979 980 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);981 if (!edit)982 return ERR_PTR(-ENOMEM);983 edit->array = array;984 edit->ops = ops;985 edit->leaf = assoc_array_leaf_to_ptr(object);986 edit->adjust_count_by = 1;987 988 switch (assoc_array_walk(array, ops, index_key, &result)) {989 case assoc_array_walk_tree_empty:990 /* Allocate a root node if there isn't one yet */991 if (!assoc_array_insert_in_empty_tree(edit))992 goto enomem;993 return edit;994 995 case assoc_array_walk_found_terminal_node:996 /* We found a node that doesn't have a node/shortcut pointer in997 * the slot corresponding to the index key that we have to998 * follow.999 */1000 if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,1001 &result))1002 goto enomem;1003 return edit;1004 1005 case assoc_array_walk_found_wrong_shortcut:1006 /* We found a shortcut that didn't match our key in a slot we1007 * needed to follow.1008 */1009 if (!assoc_array_insert_mid_shortcut(edit, ops, &result))1010 goto enomem;1011 return edit;1012 }1013 1014enomem:1015 /* Clean up after an out of memory error */1016 pr_devel("enomem\n");1017 assoc_array_cancel_edit(edit);1018 return ERR_PTR(-ENOMEM);1019}1020 1021/**1022 * assoc_array_insert_set_object - Set the new object pointer in an edit script1023 * @edit: The edit script to modify.1024 * @object: The object pointer to set.1025 *1026 * Change the object to be inserted in an edit script. The object pointed to1027 * by the old object is not freed. This must be done prior to applying the1028 * script.1029 */1030void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)1031{1032 BUG_ON(!object);1033 edit->leaf = assoc_array_leaf_to_ptr(object);1034}1035 1036struct assoc_array_delete_collapse_context {1037 struct assoc_array_node *node;1038 const void *skip_leaf;1039 int slot;1040};1041 1042/*1043 * Subtree collapse to node iterator.1044 */1045static int assoc_array_delete_collapse_iterator(const void *leaf,1046 void *iterator_data)1047{1048 struct assoc_array_delete_collapse_context *collapse = iterator_data;1049 1050 if (leaf == collapse->skip_leaf)1051 return 0;1052 1053 BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);1054 1055 collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);1056 return 0;1057}1058 1059/**1060 * assoc_array_delete - Script deletion of an object from an associative array1061 * @array: The array to search.1062 * @ops: The operations to use.1063 * @index_key: The key to the object.1064 *1065 * Precalculate and preallocate a script for the deletion of an object from an1066 * associative array. This results in an edit script that can either be1067 * applied or cancelled.1068 *1069 * The function returns a pointer to an edit script if the object was found,1070 * NULL if the object was not found or -ENOMEM.1071 *1072 * The caller should lock against other modifications and must continue to hold1073 * the lock until assoc_array_apply_edit() has been called.1074 *1075 * Accesses to the tree may take place concurrently with this function,1076 * provided they hold the RCU read lock.1077 */1078struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,1079 const struct assoc_array_ops *ops,1080 const void *index_key)1081{1082 struct assoc_array_delete_collapse_context collapse;1083 struct assoc_array_walk_result result;1084 struct assoc_array_node *node, *new_n0;1085 struct assoc_array_edit *edit;1086 struct assoc_array_ptr *ptr;1087 bool has_meta;1088 int slot, i;1089 1090 pr_devel("-->%s()\n", __func__);1091 1092 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);1093 if (!edit)1094 return ERR_PTR(-ENOMEM);1095 edit->array = array;1096 edit->ops = ops;1097 edit->adjust_count_by = -1;1098 1099 switch (assoc_array_walk(array, ops, index_key, &result)) {1100 case assoc_array_walk_found_terminal_node:1101 /* We found a node that should contain the leaf we've been1102 * asked to remove - *if* it's in the tree.1103 */1104 pr_devel("terminal_node\n");1105 node = result.terminal_node.node;1106 1107 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {1108 ptr = node->slots[slot];1109 if (ptr &&1110 assoc_array_ptr_is_leaf(ptr) &&1111 ops->compare_object(assoc_array_ptr_to_leaf(ptr),1112 index_key))1113 goto found_leaf;1114 }1115 fallthrough;1116 case assoc_array_walk_tree_empty:1117 case assoc_array_walk_found_wrong_shortcut:1118 default:1119 assoc_array_cancel_edit(edit);1120 pr_devel("not found\n");1121 return NULL;1122 }1123 1124found_leaf:1125 BUG_ON(array->nr_leaves_on_tree <= 0);1126 1127 /* In the simplest form of deletion we just clear the slot and release1128 * the leaf after a suitable interval.1129 */1130 edit->dead_leaf = node->slots[slot];1131 edit->set[0].ptr = &node->slots[slot];1132 edit->set[0].to = NULL;1133 edit->adjust_count_on = node;1134 1135 /* If that concludes erasure of the last leaf, then delete the entire1136 * internal array.1137 */1138 if (array->nr_leaves_on_tree == 1) {1139 edit->set[1].ptr = &array->root;1140 edit->set[1].to = NULL;1141 edit->adjust_count_on = NULL;1142 edit->excised_subtree = array->root;1143 pr_devel("all gone\n");1144 return edit;1145 }1146 1147 /* However, we'd also like to clear up some metadata blocks if we1148 * possibly can.1149 *1150 * We go for a simple algorithm of: if this node has FAN_OUT or fewer1151 * leaves in it, then attempt to collapse it - and attempt to1152 * recursively collapse up the tree.1153 *1154 * We could also try and collapse in partially filled subtrees to take1155 * up space in this node.1156 */1157 if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {1158 struct assoc_array_node *parent, *grandparent;1159 struct assoc_array_ptr *ptr;1160 1161 /* First of all, we need to know if this node has metadata so1162 * that we don't try collapsing if all the leaves are already1163 * here.1164 */1165 has_meta = false;1166 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {1167 ptr = node->slots[i];1168 if (assoc_array_ptr_is_meta(ptr)) {1169 has_meta = true;1170 break;1171 }1172 }1173 1174 pr_devel("leaves: %ld [m=%d]\n",1175 node->nr_leaves_on_branch - 1, has_meta);1176 1177 /* Look further up the tree to see if we can collapse this node1178 * into a more proximal node too.1179 */1180 parent = node;1181 collapse_up:1182 pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);1183 1184 ptr = parent->back_pointer;1185 if (!ptr)1186 goto do_collapse;1187 if (assoc_array_ptr_is_shortcut(ptr)) {1188 struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);1189 ptr = s->back_pointer;1190 if (!ptr)1191 goto do_collapse;1192 }1193 1194 grandparent = assoc_array_ptr_to_node(ptr);1195 if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {1196 parent = grandparent;1197 goto collapse_up;1198 }1199 1200 do_collapse:1201 /* There's no point collapsing if the original node has no meta1202 * pointers to discard and if we didn't merge into one of that1203 * node's ancestry.1204 */1205 if (has_meta || parent != node) {1206 node = parent;1207 1208 /* Create a new node to collapse into */1209 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);1210 if (!new_n0)1211 goto enomem;1212 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);1213 1214 new_n0->back_pointer = node->back_pointer;1215 new_n0->parent_slot = node->parent_slot;1216 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;1217 edit->adjust_count_on = new_n0;1218 1219 collapse.node = new_n0;1220 collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);1221 collapse.slot = 0;1222 assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),1223 node->back_pointer,1224 assoc_array_delete_collapse_iterator,1225 &collapse);1226 pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);1227 BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);1228 1229 if (!node->back_pointer) {1230 edit->set[1].ptr = &array->root;1231 } else if (assoc_array_ptr_is_leaf(node->back_pointer)) {1232 BUG();1233 } else if (assoc_array_ptr_is_node(node->back_pointer)) {1234 struct assoc_array_node *p =1235 assoc_array_ptr_to_node(node->back_pointer);1236 edit->set[1].ptr = &p->slots[node->parent_slot];1237 } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {1238 struct assoc_array_shortcut *s =1239 assoc_array_ptr_to_shortcut(node->back_pointer);1240 edit->set[1].ptr = &s->next_node;1241 }1242 edit->set[1].to = assoc_array_node_to_ptr(new_n0);1243 edit->excised_subtree = assoc_array_node_to_ptr(node);1244 }1245 }1246 1247 return edit;1248 1249enomem:1250 /* Clean up after an out of memory error */1251 pr_devel("enomem\n");1252 assoc_array_cancel_edit(edit);1253 return ERR_PTR(-ENOMEM);1254}1255 1256/**1257 * assoc_array_clear - Script deletion of all objects from an associative array1258 * @array: The array to clear.1259 * @ops: The operations to use.1260 *1261 * Precalculate and preallocate a script for the deletion of all the objects1262 * from an associative array. This results in an edit script that can either1263 * be applied or cancelled.1264 *1265 * The function returns a pointer to an edit script if there are objects to be1266 * deleted, NULL if there are no objects in the array or -ENOMEM.1267 *1268 * The caller should lock against other modifications and must continue to hold1269 * the lock until assoc_array_apply_edit() has been called.1270 *1271 * Accesses to the tree may take place concurrently with this function,1272 * provided they hold the RCU read lock.1273 */1274struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,1275 const struct assoc_array_ops *ops)1276{1277 struct assoc_array_edit *edit;1278 1279 pr_devel("-->%s()\n", __func__);1280 1281 if (!array->root)1282 return NULL;1283 1284 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);1285 if (!edit)1286 return ERR_PTR(-ENOMEM);1287 edit->array = array;1288 edit->ops = ops;1289 edit->set[1].ptr = &array->root;1290 edit->set[1].to = NULL;1291 edit->excised_subtree = array->root;1292 edit->ops_for_excised_subtree = ops;1293 pr_devel("all gone\n");1294 return edit;1295}1296 1297/*1298 * Handle the deferred destruction after an applied edit.1299 */1300static void assoc_array_rcu_cleanup(struct rcu_head *head)1301{1302 struct assoc_array_edit *edit =1303 container_of(head, struct assoc_array_edit, rcu);1304 int i;1305 1306 pr_devel("-->%s()\n", __func__);1307 1308 if (edit->dead_leaf)1309 edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));1310 for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)1311 if (edit->excised_meta[i])1312 kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));1313 1314 if (edit->excised_subtree) {1315 BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));1316 if (assoc_array_ptr_is_node(edit->excised_subtree)) {1317 struct assoc_array_node *n =1318 assoc_array_ptr_to_node(edit->excised_subtree);1319 n->back_pointer = NULL;1320 } else {1321 struct assoc_array_shortcut *s =1322 assoc_array_ptr_to_shortcut(edit->excised_subtree);1323 s->back_pointer = NULL;1324 }1325 assoc_array_destroy_subtree(edit->excised_subtree,1326 edit->ops_for_excised_subtree);1327 }1328 1329 kfree(edit);1330}1331 1332/**1333 * assoc_array_apply_edit - Apply an edit script to an associative array1334 * @edit: The script to apply.1335 *1336 * Apply an edit script to an associative array to effect an insertion,1337 * deletion or clearance. As the edit script includes preallocated memory,1338 * this is guaranteed not to fail.1339 *1340 * The edit script, dead objects and dead metadata will be scheduled for1341 * destruction after an RCU grace period to permit those doing read-only1342 * accesses on the array to continue to do so under the RCU read lock whilst1343 * the edit is taking place.1344 */1345void assoc_array_apply_edit(struct assoc_array_edit *edit)1346{1347 struct assoc_array_shortcut *shortcut;1348 struct assoc_array_node *node;1349 struct assoc_array_ptr *ptr;1350 int i;1351 1352 pr_devel("-->%s()\n", __func__);1353 1354 smp_wmb();1355 if (edit->leaf_p)1356 *edit->leaf_p = edit->leaf;1357 1358 smp_wmb();1359 for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)1360 if (edit->set_parent_slot[i].p)1361 *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;1362 1363 smp_wmb();1364 for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)1365 if (edit->set_backpointers[i])1366 *edit->set_backpointers[i] = edit->set_backpointers_to;1367 1368 smp_wmb();1369 for (i = 0; i < ARRAY_SIZE(edit->set); i++)1370 if (edit->set[i].ptr)1371 *edit->set[i].ptr = edit->set[i].to;1372 1373 if (edit->array->root == NULL) {1374 edit->array->nr_leaves_on_tree = 0;1375 } else if (edit->adjust_count_on) {1376 node = edit->adjust_count_on;1377 for (;;) {1378 node->nr_leaves_on_branch += edit->adjust_count_by;1379 1380 ptr = node->back_pointer;1381 if (!ptr)1382 break;1383 if (assoc_array_ptr_is_shortcut(ptr)) {1384 shortcut = assoc_array_ptr_to_shortcut(ptr);1385 ptr = shortcut->back_pointer;1386 if (!ptr)1387 break;1388 }1389 BUG_ON(!assoc_array_ptr_is_node(ptr));1390 node = assoc_array_ptr_to_node(ptr);1391 }1392 1393 edit->array->nr_leaves_on_tree += edit->adjust_count_by;1394 }1395 1396 call_rcu(&edit->rcu, assoc_array_rcu_cleanup);1397}1398 1399/**1400 * assoc_array_cancel_edit - Discard an edit script.1401 * @edit: The script to discard.1402 *1403 * Free an edit script and all the preallocated data it holds without making1404 * any changes to the associative array it was intended for.1405 *1406 * NOTE! In the case of an insertion script, this does _not_ release the leaf1407 * that was to be inserted. That is left to the caller.1408 */1409void assoc_array_cancel_edit(struct assoc_array_edit *edit)1410{1411 struct assoc_array_ptr *ptr;1412 int i;1413 1414 pr_devel("-->%s()\n", __func__);1415 1416 /* Clean up after an out of memory error */1417 for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {1418 ptr = edit->new_meta[i];1419 if (ptr) {1420 if (assoc_array_ptr_is_node(ptr))1421 kfree(assoc_array_ptr_to_node(ptr));1422 else1423 kfree(assoc_array_ptr_to_shortcut(ptr));1424 }1425 }1426 kfree(edit);1427}1428 1429/**1430 * assoc_array_gc - Garbage collect an associative array.1431 * @array: The array to clean.1432 * @ops: The operations to use.1433 * @iterator: A callback function to pass judgement on each object.1434 * @iterator_data: Private data for the callback function.1435 *1436 * Collect garbage from an associative array and pack down the internal tree to1437 * save memory.1438 *1439 * The iterator function is asked to pass judgement upon each object in the1440 * array. If it returns false, the object is discard and if it returns true,1441 * the object is kept. If it returns true, it must increment the object's1442 * usage count (or whatever it needs to do to retain it) before returning.1443 *1444 * This function returns 0 if successful or -ENOMEM if out of memory. In the1445 * latter case, the array is not changed.1446 *1447 * The caller should lock against other modifications and must continue to hold1448 * the lock until assoc_array_apply_edit() has been called.1449 *1450 * Accesses to the tree may take place concurrently with this function,1451 * provided they hold the RCU read lock.1452 */1453int assoc_array_gc(struct assoc_array *array,1454 const struct assoc_array_ops *ops,1455 bool (*iterator)(void *object, void *iterator_data),1456 void *iterator_data)1457{1458 struct assoc_array_shortcut *shortcut, *new_s;1459 struct assoc_array_node *node, *new_n;1460 struct assoc_array_edit *edit;1461 struct assoc_array_ptr *cursor, *ptr;1462 struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;1463 unsigned long nr_leaves_on_tree;1464 bool retained;1465 int keylen, slot, nr_free, next_slot, i;1466 1467 pr_devel("-->%s()\n", __func__);1468 1469 if (!array->root)1470 return 0;1471 1472 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);1473 if (!edit)1474 return -ENOMEM;1475 edit->array = array;1476 edit->ops = ops;1477 edit->ops_for_excised_subtree = ops;1478 edit->set[0].ptr = &array->root;1479 edit->excised_subtree = array->root;1480 1481 new_root = new_parent = NULL;1482 new_ptr_pp = &new_root;1483 cursor = array->root;1484 1485descend:1486 /* If this point is a shortcut, then we need to duplicate it and1487 * advance the target cursor.1488 */1489 if (assoc_array_ptr_is_shortcut(cursor)) {1490 shortcut = assoc_array_ptr_to_shortcut(cursor);1491 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);1492 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;1493 new_s = kmalloc(struct_size(new_s, index_key, keylen),1494 GFP_KERNEL);1495 if (!new_s)1496 goto enomem;1497 pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);1498 memcpy(new_s, shortcut, struct_size(new_s, index_key, keylen));1499 new_s->back_pointer = new_parent;1500 new_s->parent_slot = shortcut->parent_slot;1501 *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);1502 new_ptr_pp = &new_s->next_node;1503 cursor = shortcut->next_node;1504 }1505 1506 /* Duplicate the node at this position */1507 node = assoc_array_ptr_to_node(cursor);1508 new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);1509 if (!new_n)1510 goto enomem;1511 pr_devel("dup node %p -> %p\n", node, new_n);1512 new_n->back_pointer = new_parent;1513 new_n->parent_slot = node->parent_slot;1514 *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);1515 new_ptr_pp = NULL;1516 slot = 0;1517 1518continue_node:1519 /* Filter across any leaves and gc any subtrees */1520 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {1521 ptr = node->slots[slot];1522 if (!ptr)1523 continue;1524 1525 if (assoc_array_ptr_is_leaf(ptr)) {1526 if (iterator(assoc_array_ptr_to_leaf(ptr),1527 iterator_data))1528 /* The iterator will have done any reference1529 * counting on the object for us.1530 */1531 new_n->slots[slot] = ptr;1532 continue;1533 }1534 1535 new_ptr_pp = &new_n->slots[slot];1536 cursor = ptr;1537 goto descend;1538 }1539 1540retry_compress:1541 pr_devel("-- compress node %p --\n", new_n);1542 1543 /* Count up the number of empty slots in this node and work out the1544 * subtree leaf count.1545 */1546 new_n->nr_leaves_on_branch = 0;1547 nr_free = 0;1548 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {1549 ptr = new_n->slots[slot];1550 if (!ptr)1551 nr_free++;1552 else if (assoc_array_ptr_is_leaf(ptr))1553 new_n->nr_leaves_on_branch++;1554 }1555 pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);1556 1557 /* See what we can fold in */1558 retained = false;1559 next_slot = 0;1560 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {1561 struct assoc_array_shortcut *s;1562 struct assoc_array_node *child;1563 1564 ptr = new_n->slots[slot];1565 if (!ptr || assoc_array_ptr_is_leaf(ptr))1566 continue;1567 1568 s = NULL;1569 if (assoc_array_ptr_is_shortcut(ptr)) {1570 s = assoc_array_ptr_to_shortcut(ptr);1571 ptr = s->next_node;1572 }1573 1574 child = assoc_array_ptr_to_node(ptr);1575 new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;1576 1577 if (child->nr_leaves_on_branch <= nr_free + 1) {1578 /* Fold the child node into this one */1579 pr_devel("[%d] fold node %lu/%d [nx %d]\n",1580 slot, child->nr_leaves_on_branch, nr_free + 1,1581 next_slot);1582 1583 /* We would already have reaped an intervening shortcut1584 * on the way back up the tree.1585 */1586 BUG_ON(s);1587 1588 new_n->slots[slot] = NULL;1589 nr_free++;1590 if (slot < next_slot)1591 next_slot = slot;1592 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {1593 struct assoc_array_ptr *p = child->slots[i];1594 if (!p)1595 continue;1596 BUG_ON(assoc_array_ptr_is_meta(p));1597 while (new_n->slots[next_slot])1598 next_slot++;1599 BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);1600 new_n->slots[next_slot++] = p;1601 nr_free--;1602 }1603 kfree(child);1604 } else {1605 pr_devel("[%d] retain node %lu/%d [nx %d]\n",1606 slot, child->nr_leaves_on_branch, nr_free + 1,1607 next_slot);1608 retained = true;1609 }1610 }1611 1612 if (retained && new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {1613 pr_devel("internal nodes remain despite enough space, retrying\n");1614 goto retry_compress;1615 }1616 pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);1617 1618 nr_leaves_on_tree = new_n->nr_leaves_on_branch;1619 1620 /* Excise this node if it is singly occupied by a shortcut */1621 if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {1622 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)1623 if ((ptr = new_n->slots[slot]))1624 break;1625 1626 if (assoc_array_ptr_is_meta(ptr) &&1627 assoc_array_ptr_is_shortcut(ptr)) {1628 pr_devel("excise node %p with 1 shortcut\n", new_n);1629 new_s = assoc_array_ptr_to_shortcut(ptr);1630 new_parent = new_n->back_pointer;1631 slot = new_n->parent_slot;1632 kfree(new_n);1633 if (!new_parent) {1634 new_s->back_pointer = NULL;1635 new_s->parent_slot = 0;1636 new_root = ptr;1637 goto gc_complete;1638 }1639 1640 if (assoc_array_ptr_is_shortcut(new_parent)) {1641 /* We can discard any preceding shortcut also */1642 struct assoc_array_shortcut *s =1643 assoc_array_ptr_to_shortcut(new_parent);1644 1645 pr_devel("excise preceding shortcut\n");1646 1647 new_parent = new_s->back_pointer = s->back_pointer;1648 slot = new_s->parent_slot = s->parent_slot;1649 kfree(s);1650 if (!new_parent) {1651 new_s->back_pointer = NULL;1652 new_s->parent_slot = 0;1653 new_root = ptr;1654 goto gc_complete;1655 }1656 }1657 1658 new_s->back_pointer = new_parent;1659 new_s->parent_slot = slot;1660 new_n = assoc_array_ptr_to_node(new_parent);1661 new_n->slots[slot] = ptr;1662 goto ascend_old_tree;1663 }1664 }1665 1666 /* Excise any shortcuts we might encounter that point to nodes that1667 * only contain leaves.1668 */1669 ptr = new_n->back_pointer;1670 if (!ptr)1671 goto gc_complete;1672 1673 if (assoc_array_ptr_is_shortcut(ptr)) {1674 new_s = assoc_array_ptr_to_shortcut(ptr);1675 new_parent = new_s->back_pointer;1676 slot = new_s->parent_slot;1677 1678 if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {1679 struct assoc_array_node *n;1680 1681 pr_devel("excise shortcut\n");1682 new_n->back_pointer = new_parent;1683 new_n->parent_slot = slot;1684 kfree(new_s);1685 if (!new_parent) {1686 new_root = assoc_array_node_to_ptr(new_n);1687 goto gc_complete;1688 }1689 1690 n = assoc_array_ptr_to_node(new_parent);1691 n->slots[slot] = assoc_array_node_to_ptr(new_n);1692 }1693 } else {1694 new_parent = ptr;1695 }1696 new_n = assoc_array_ptr_to_node(new_parent);1697 1698ascend_old_tree:1699 ptr = node->back_pointer;1700 if (assoc_array_ptr_is_shortcut(ptr)) {1701 shortcut = assoc_array_ptr_to_shortcut(ptr);1702 slot = shortcut->parent_slot;1703 cursor = shortcut->back_pointer;1704 if (!cursor)1705 goto gc_complete;1706 } else {1707 slot = node->parent_slot;1708 cursor = ptr;1709 }1710 BUG_ON(!cursor);1711 node = assoc_array_ptr_to_node(cursor);1712 slot++;1713 goto continue_node;1714 1715gc_complete:1716 edit->set[0].to = new_root;1717 assoc_array_apply_edit(edit);1718 array->nr_leaves_on_tree = nr_leaves_on_tree;1719 return 0;1720 1721enomem:1722 pr_devel("enomem\n");1723 assoc_array_destroy_subtree(new_root, edit->ops);1724 kfree(edit);1725 return -ENOMEM;1726}1727