1 /* Generic associative array implementation.
3 * See Documentation/assoc_array.txt for information.
5 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public Licence
10 * as published by the Free Software Foundation; either version
11 * 2 of the Licence, or (at your option) any later version.
14 #include <linux/rcupdate.h>
15 #include <linux/slab.h>
16 #include <linux/err.h>
17 #include <linux/assoc_array_priv.h>
20 * Iterate over an associative array. The caller must hold the RCU read lock
23 static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
24 const struct assoc_array_ptr *stop,
25 int (*iterator)(const void *leaf,
29 const struct assoc_array_shortcut *shortcut;
30 const struct assoc_array_node *node;
31 const struct assoc_array_ptr *cursor, *ptr, *parent;
32 unsigned long has_meta;
38 if (assoc_array_ptr_is_shortcut(cursor)) {
39 /* Descend through a shortcut */
40 shortcut = assoc_array_ptr_to_shortcut(cursor);
41 smp_read_barrier_depends();
42 cursor = ACCESS_ONCE(shortcut->next_node);
45 node = assoc_array_ptr_to_node(cursor);
46 smp_read_barrier_depends();
49 /* We perform two passes of each node.
51 * The first pass does all the leaves in this node. This means we
52 * don't miss any leaves if the node is split up by insertion whilst
53 * we're iterating over the branches rooted here (we may, however, see
57 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
58 ptr = ACCESS_ONCE(node->slots[slot]);
59 has_meta |= (unsigned long)ptr;
60 if (ptr && assoc_array_ptr_is_leaf(ptr)) {
61 /* We need a barrier between the read of the pointer
62 * and dereferencing the pointer - but only if we are
63 * actually going to dereference it.
65 smp_read_barrier_depends();
67 /* Invoke the callback */
68 ret = iterator(assoc_array_ptr_to_leaf(ptr),
75 /* The second pass attends to all the metadata pointers. If we follow
76 * one of these we may find that we don't come back here, but rather go
77 * back to a replacement node with the leaves in a different layout.
79 * We are guaranteed to make progress, however, as the slot number for
80 * a particular portion of the key space cannot change - and we
81 * continue at the back pointer + 1.
83 if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))
88 node = assoc_array_ptr_to_node(cursor);
89 smp_read_barrier_depends();
91 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
92 ptr = ACCESS_ONCE(node->slots[slot]);
93 if (assoc_array_ptr_is_meta(ptr)) {
100 /* Move up to the parent (may need to skip back over a shortcut) */
101 parent = ACCESS_ONCE(node->back_pointer);
102 slot = node->parent_slot;
106 if (assoc_array_ptr_is_shortcut(parent)) {
107 shortcut = assoc_array_ptr_to_shortcut(parent);
108 smp_read_barrier_depends();
110 parent = ACCESS_ONCE(shortcut->back_pointer);
111 slot = shortcut->parent_slot;
116 /* Ascend to next slot in parent node */
123 * assoc_array_iterate - Pass all objects in the array to a callback
124 * @array: The array to iterate over.
125 * @iterator: The callback function.
126 * @iterator_data: Private data for the callback function.
128 * Iterate over all the objects in an associative array. Each one will be
129 * presented to the iterator function.
131 * If the array is being modified concurrently with the iteration then it is
132 * possible that some objects in the array will be passed to the iterator
133 * callback more than once - though every object should be passed at least
134 * once. If this is undesirable then the caller must lock against modification
135 * for the duration of this function.
137 * The function will return 0 if no objects were in the array or else it will
138 * return the result of the last iterator function called. Iteration stops
139 * immediately if any call to the iteration function results in a non-zero
142 * The caller should hold the RCU read lock or better if concurrent
143 * modification is possible.
145 int assoc_array_iterate(const struct assoc_array *array,
146 int (*iterator)(const void *object,
147 void *iterator_data),
150 struct assoc_array_ptr *root = ACCESS_ONCE(array->root);
154 return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data);
157 enum assoc_array_walk_status {
158 assoc_array_walk_tree_empty,
159 assoc_array_walk_found_terminal_node,
160 assoc_array_walk_found_wrong_shortcut,
163 struct assoc_array_walk_result {
165 struct assoc_array_node *node; /* Node in which leaf might be found */
170 struct assoc_array_shortcut *shortcut;
173 unsigned long sc_segments;
174 unsigned long dissimilarity;
179 * Navigate through the internal tree looking for the closest node to the key.
181 static enum assoc_array_walk_status
182 assoc_array_walk(const struct assoc_array *array,
183 const struct assoc_array_ops *ops,
184 const void *index_key,
185 struct assoc_array_walk_result *result)
187 struct assoc_array_shortcut *shortcut;
188 struct assoc_array_node *node;
189 struct assoc_array_ptr *cursor, *ptr;
190 unsigned long sc_segments, dissimilarity;
191 unsigned long segments;
192 int level, sc_level, next_sc_level;
195 pr_devel("-->%s()\n", __func__);
197 cursor = ACCESS_ONCE(array->root);
199 return assoc_array_walk_tree_empty;
203 /* Use segments from the key for the new leaf to navigate through the
204 * internal tree, skipping through nodes and shortcuts that are on
205 * route to the destination. Eventually we'll come to a slot that is
206 * either empty or contains a leaf at which point we've found a node in
207 * which the leaf we're looking for might be found or into which it
208 * should be inserted.
211 segments = ops->get_key_chunk(index_key, level);
212 pr_devel("segments[%d]: %lx\n", level, segments);
214 if (assoc_array_ptr_is_shortcut(cursor))
215 goto follow_shortcut;
218 node = assoc_array_ptr_to_node(cursor);
219 smp_read_barrier_depends();
221 slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
222 slot &= ASSOC_ARRAY_FAN_MASK;
223 ptr = ACCESS_ONCE(node->slots[slot]);
225 pr_devel("consider slot %x [ix=%d type=%lu]\n",
226 slot, level, (unsigned long)ptr & 3);
228 if (!assoc_array_ptr_is_meta(ptr)) {
229 /* The node doesn't have a node/shortcut pointer in the slot
230 * corresponding to the index key that we have to follow.
232 result->terminal_node.node = node;
233 result->terminal_node.level = level;
234 result->terminal_node.slot = slot;
235 pr_devel("<--%s() = terminal_node\n", __func__);
236 return assoc_array_walk_found_terminal_node;
239 if (assoc_array_ptr_is_node(ptr)) {
240 /* There is a pointer to a node in the slot corresponding to
241 * this index key segment, so we need to follow it.
244 level += ASSOC_ARRAY_LEVEL_STEP;
245 if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0)
250 /* There is a shortcut in the slot corresponding to the index key
251 * segment. We follow the shortcut if its partial index key matches
252 * this leaf's. Otherwise we need to split the shortcut.
256 shortcut = assoc_array_ptr_to_shortcut(cursor);
257 smp_read_barrier_depends();
258 pr_devel("shortcut to %d\n", shortcut->skip_to_level);
259 sc_level = level + ASSOC_ARRAY_LEVEL_STEP;
260 BUG_ON(sc_level > shortcut->skip_to_level);
263 /* Check the leaf against the shortcut's index key a word at a
264 * time, trimming the final word (the shortcut stores the index
265 * key completely from the root to the shortcut's target).
267 if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0)
268 segments = ops->get_key_chunk(index_key, sc_level);
270 sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT];
271 dissimilarity = segments ^ sc_segments;
273 if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) {
274 /* Trim segments that are beyond the shortcut */
275 int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK;
276 dissimilarity &= ~(ULONG_MAX << shift);
277 next_sc_level = shortcut->skip_to_level;
279 next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE;
280 next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
283 if (dissimilarity != 0) {
284 /* This shortcut points elsewhere */
285 result->wrong_shortcut.shortcut = shortcut;
286 result->wrong_shortcut.level = level;
287 result->wrong_shortcut.sc_level = sc_level;
288 result->wrong_shortcut.sc_segments = sc_segments;
289 result->wrong_shortcut.dissimilarity = dissimilarity;
290 return assoc_array_walk_found_wrong_shortcut;
293 sc_level = next_sc_level;
294 } while (sc_level < shortcut->skip_to_level);
296 /* The shortcut matches the leaf's index to this point. */
297 cursor = ACCESS_ONCE(shortcut->next_node);
298 if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) {
308 * assoc_array_find - Find an object by index key
309 * @array: The associative array to search.
310 * @ops: The operations to use.
311 * @index_key: The key to the object.
313 * Find an object in an associative array by walking through the internal tree
314 * to the node that should contain the object and then searching the leaves
315 * there. NULL is returned if the requested object was not found in the array.
317 * The caller must hold the RCU read lock or better.
319 void *assoc_array_find(const struct assoc_array *array,
320 const struct assoc_array_ops *ops,
321 const void *index_key)
323 struct assoc_array_walk_result result;
324 const struct assoc_array_node *node;
325 const struct assoc_array_ptr *ptr;
329 if (assoc_array_walk(array, ops, index_key, &result) !=
330 assoc_array_walk_found_terminal_node)
333 node = result.terminal_node.node;
334 smp_read_barrier_depends();
336 /* If the target key is available to us, it's has to be pointed to by
339 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
340 ptr = ACCESS_ONCE(node->slots[slot]);
341 if (ptr && assoc_array_ptr_is_leaf(ptr)) {
342 /* We need a barrier between the read of the pointer
343 * and dereferencing the pointer - but only if we are
344 * actually going to dereference it.
346 leaf = assoc_array_ptr_to_leaf(ptr);
347 smp_read_barrier_depends();
348 if (ops->compare_object(leaf, index_key))
357 * Destructively iterate over an associative array. The caller must prevent
358 * other simultaneous accesses.
360 static void assoc_array_destroy_subtree(struct assoc_array_ptr *root,
361 const struct assoc_array_ops *ops)
363 struct assoc_array_shortcut *shortcut;
364 struct assoc_array_node *node;
365 struct assoc_array_ptr *cursor, *parent = NULL;
368 pr_devel("-->%s()\n", __func__);
377 if (assoc_array_ptr_is_shortcut(cursor)) {
378 /* Descend through a shortcut */
379 pr_devel("[%d] shortcut\n", slot);
380 BUG_ON(!assoc_array_ptr_is_shortcut(cursor));
381 shortcut = assoc_array_ptr_to_shortcut(cursor);
382 BUG_ON(shortcut->back_pointer != parent);
383 BUG_ON(slot != -1 && shortcut->parent_slot != slot);
385 cursor = shortcut->next_node;
387 BUG_ON(!assoc_array_ptr_is_node(cursor));
390 pr_devel("[%d] node\n", slot);
391 node = assoc_array_ptr_to_node(cursor);
392 BUG_ON(node->back_pointer != parent);
393 BUG_ON(slot != -1 && node->parent_slot != slot);
397 pr_devel("Node %p [back=%p]\n", node, node->back_pointer);
398 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
399 struct assoc_array_ptr *ptr = node->slots[slot];
402 if (assoc_array_ptr_is_meta(ptr)) {
409 pr_devel("[%d] free leaf\n", slot);
410 ops->free_object(assoc_array_ptr_to_leaf(ptr));
414 parent = node->back_pointer;
415 slot = node->parent_slot;
416 pr_devel("free node\n");
421 /* Move back up to the parent (may need to free a shortcut on
423 if (assoc_array_ptr_is_shortcut(parent)) {
424 shortcut = assoc_array_ptr_to_shortcut(parent);
425 BUG_ON(shortcut->next_node != cursor);
427 parent = shortcut->back_pointer;
428 slot = shortcut->parent_slot;
429 pr_devel("free shortcut\n");
434 BUG_ON(!assoc_array_ptr_is_node(parent));
437 /* Ascend to next slot in parent node */
438 pr_devel("ascend to %p[%d]\n", parent, slot);
440 node = assoc_array_ptr_to_node(cursor);
446 * assoc_array_destroy - Destroy an associative array
447 * @array: The array to destroy.
448 * @ops: The operations to use.
450 * Discard all metadata and free all objects in an associative array. The
451 * array will be empty and ready to use again upon completion. This function
454 * The caller must prevent all other accesses whilst this takes place as no
455 * attempt is made to adjust pointers gracefully to permit RCU readlock-holding
456 * accesses to continue. On the other hand, no memory allocation is required.
458 void assoc_array_destroy(struct assoc_array *array,
459 const struct assoc_array_ops *ops)
461 assoc_array_destroy_subtree(array->root, ops);
466 * Handle insertion into an empty tree.
468 static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit)
470 struct assoc_array_node *new_n0;
472 pr_devel("-->%s()\n", __func__);
474 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
478 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
479 edit->leaf_p = &new_n0->slots[0];
480 edit->adjust_count_on = new_n0;
481 edit->set[0].ptr = &edit->array->root;
482 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
484 pr_devel("<--%s() = ok [no root]\n", __func__);
489 * Handle insertion into a terminal node.
491 static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
492 const struct assoc_array_ops *ops,
493 const void *index_key,
494 struct assoc_array_walk_result *result)
496 struct assoc_array_shortcut *shortcut, *new_s0;
497 struct assoc_array_node *node, *new_n0, *new_n1, *side;
498 struct assoc_array_ptr *ptr;
499 unsigned long dissimilarity, base_seg, blank;
503 int slot, next_slot, free_slot, i, j;
505 node = result->terminal_node.node;
506 level = result->terminal_node.level;
507 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot;
509 pr_devel("-->%s()\n", __func__);
511 /* We arrived at a node which doesn't have an onward node or shortcut
512 * pointer that we have to follow. This means that (a) the leaf we
513 * want must go here (either by insertion or replacement) or (b) we
514 * need to split this node and insert in one of the fragments.
518 /* Firstly, we have to check the leaves in this node to see if there's
519 * a matching one we should replace in place.
521 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
522 ptr = node->slots[i];
527 if (ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) {
528 pr_devel("replace in slot %d\n", i);
529 edit->leaf_p = &node->slots[i];
530 edit->dead_leaf = node->slots[i];
531 pr_devel("<--%s() = ok [replace]\n", __func__);
536 /* If there is a free slot in this node then we can just insert the
539 if (free_slot >= 0) {
540 pr_devel("insert in free slot %d\n", free_slot);
541 edit->leaf_p = &node->slots[free_slot];
542 edit->adjust_count_on = node;
543 pr_devel("<--%s() = ok [insert]\n", __func__);
547 /* The node has no spare slots - so we're either going to have to split
548 * it or insert another node before it.
550 * Whatever, we're going to need at least two new nodes - so allocate
551 * those now. We may also need a new shortcut, but we deal with that
554 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
557 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
558 new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
561 edit->new_meta[1] = assoc_array_node_to_ptr(new_n1);
563 /* We need to find out how similar the leaves are. */
564 pr_devel("no spare slots\n");
566 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
567 ptr = node->slots[i];
568 if (assoc_array_ptr_is_meta(ptr)) {
569 edit->segment_cache[i] = 0xff;
573 base_seg = ops->get_object_key_chunk(
574 assoc_array_ptr_to_leaf(ptr), level);
575 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
576 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
580 pr_devel("have meta\n");
584 /* The node contains only leaves */
586 base_seg = edit->segment_cache[0];
587 for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++)
588 dissimilarity |= edit->segment_cache[i] ^ base_seg;
590 pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity);
592 if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) {
593 /* The old leaves all cluster in the same slot. We will need
594 * to insert a shortcut if the new node wants to cluster with them.
596 if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0)
597 goto all_leaves_cluster_together;
599 /* Otherwise we can just insert a new node ahead of the old
602 goto present_leaves_cluster_but_not_new_leaf;
606 pr_devel("split node\n");
608 /* We need to split the current node; we know that the node doesn't
609 * simply contain a full set of leaves that cluster together (it
610 * contains meta pointers and/or non-clustering leaves).
612 * We need to expel at least two leaves out of a set consisting of the
613 * leaves in the node and the new leaf.
615 * We need a new node (n0) to replace the current one and a new node to
616 * take the expelled nodes (n1).
618 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
619 new_n0->back_pointer = node->back_pointer;
620 new_n0->parent_slot = node->parent_slot;
621 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
622 new_n1->parent_slot = -1; /* Need to calculate this */
625 pr_devel("do_split_node\n");
627 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
628 new_n1->nr_leaves_on_branch = 0;
630 /* Begin by finding two matching leaves. There have to be at least two
631 * that match - even if there are meta pointers - because any leaf that
632 * would match a slot with a meta pointer in it must be somewhere
633 * behind that meta pointer and cannot be here. Further, given N
634 * remaining leaf slots, we now have N+1 leaves to go in them.
636 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
637 slot = edit->segment_cache[i];
639 for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)
640 if (edit->segment_cache[j] == slot)
641 goto found_slot_for_multiple_occupancy;
643 found_slot_for_multiple_occupancy:
644 pr_devel("same slot: %x %x [%02x]\n", i, j, slot);
645 BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);
646 BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);
647 BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);
649 new_n1->parent_slot = slot;
651 /* Metadata pointers cannot change slot */
652 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
653 if (assoc_array_ptr_is_meta(node->slots[i]))
654 new_n0->slots[i] = node->slots[i];
656 new_n0->slots[i] = NULL;
657 BUG_ON(new_n0->slots[slot] != NULL);
658 new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);
660 /* Filter the leaf pointers between the new nodes */
663 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
664 if (assoc_array_ptr_is_meta(node->slots[i]))
666 if (edit->segment_cache[i] == slot) {
667 new_n1->slots[next_slot++] = node->slots[i];
668 new_n1->nr_leaves_on_branch++;
672 } while (new_n0->slots[free_slot] != NULL);
673 new_n0->slots[free_slot] = node->slots[i];
677 pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);
679 if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {
682 } while (new_n0->slots[free_slot] != NULL);
683 edit->leaf_p = &new_n0->slots[free_slot];
684 edit->adjust_count_on = new_n0;
686 edit->leaf_p = &new_n1->slots[next_slot++];
687 edit->adjust_count_on = new_n1;
690 BUG_ON(next_slot <= 1);
692 edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);
693 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
694 if (edit->segment_cache[i] == 0xff) {
695 ptr = node->slots[i];
696 BUG_ON(assoc_array_ptr_is_leaf(ptr));
697 if (assoc_array_ptr_is_node(ptr)) {
698 side = assoc_array_ptr_to_node(ptr);
699 edit->set_backpointers[i] = &side->back_pointer;
701 shortcut = assoc_array_ptr_to_shortcut(ptr);
702 edit->set_backpointers[i] = &shortcut->back_pointer;
707 ptr = node->back_pointer;
709 edit->set[0].ptr = &edit->array->root;
710 else if (assoc_array_ptr_is_node(ptr))
711 edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];
713 edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;
714 edit->excised_meta[0] = assoc_array_node_to_ptr(node);
715 pr_devel("<--%s() = ok [split node]\n", __func__);
718 present_leaves_cluster_but_not_new_leaf:
719 /* All the old leaves cluster in the same slot, but the new leaf wants
720 * to go into a different slot, so we create a new node to hold the new
721 * leaf and a pointer to a new node holding all the old leaves.
723 pr_devel("present leaves cluster but not new leaf\n");
725 new_n0->back_pointer = node->back_pointer;
726 new_n0->parent_slot = node->parent_slot;
727 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
728 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
729 new_n1->parent_slot = edit->segment_cache[0];
730 new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch;
731 edit->adjust_count_on = new_n0;
733 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
734 new_n1->slots[i] = node->slots[i];
736 new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0);
737 edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]];
739 edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot];
740 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
741 edit->excised_meta[0] = assoc_array_node_to_ptr(node);
742 pr_devel("<--%s() = ok [insert node before]\n", __func__);
745 all_leaves_cluster_together:
746 /* All the leaves, new and old, want to cluster together in this node
747 * in the same slot, so we have to replace this node with a shortcut to
748 * skip over the identical parts of the key and then place a pair of
749 * nodes, one inside the other, at the end of the shortcut and
750 * distribute the keys between them.
752 * Firstly we need to work out where the leaves start diverging as a
753 * bit position into their keys so that we know how big the shortcut
756 * We only need to make a single pass of N of the N+1 leaves because if
757 * any keys differ between themselves at bit X then at least one of
758 * them must also differ with the base key at bit X or before.
760 pr_devel("all leaves cluster together\n");
762 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
763 int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]),
770 BUG_ON(diff == INT_MAX);
771 BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);
773 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
774 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
776 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
777 keylen * sizeof(unsigned long), GFP_KERNEL);
780 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
782 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
783 new_s0->back_pointer = node->back_pointer;
784 new_s0->parent_slot = node->parent_slot;
785 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
786 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
787 new_n0->parent_slot = 0;
788 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
789 new_n1->parent_slot = -1; /* Need to calculate this */
791 new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;
792 pr_devel("skip_to_level = %d [diff %d]\n", level, diff);
795 for (i = 0; i < keylen; i++)
796 new_s0->index_key[i] =
797 ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
799 blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
800 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
801 new_s0->index_key[keylen - 1] &= ~blank;
803 /* This now reduces to a node splitting exercise for which we'll need
804 * to regenerate the disparity table.
806 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
807 ptr = node->slots[i];
808 base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),
810 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
811 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
814 base_seg = ops->get_key_chunk(index_key, level);
815 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
816 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;
821 * Handle insertion into the middle of a shortcut.
823 static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
824 const struct assoc_array_ops *ops,
825 struct assoc_array_walk_result *result)
827 struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;
828 struct assoc_array_node *node, *new_n0, *side;
829 unsigned long sc_segments, dissimilarity, blank;
831 int level, sc_level, diff;
834 shortcut = result->wrong_shortcut.shortcut;
835 level = result->wrong_shortcut.level;
836 sc_level = result->wrong_shortcut.sc_level;
837 sc_segments = result->wrong_shortcut.sc_segments;
838 dissimilarity = result->wrong_shortcut.dissimilarity;
840 pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",
841 __func__, level, dissimilarity, sc_level);
843 /* We need to split a shortcut and insert a node between the two
844 * pieces. Zero-length pieces will be dispensed with entirely.
846 * First of all, we need to find out in which level the first
849 diff = __ffs(dissimilarity);
850 diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;
851 diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;
852 pr_devel("diff=%d\n", diff);
854 if (!shortcut->back_pointer) {
855 edit->set[0].ptr = &edit->array->root;
856 } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {
857 node = assoc_array_ptr_to_node(shortcut->back_pointer);
858 edit->set[0].ptr = &node->slots[shortcut->parent_slot];
863 edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);
865 /* Create a new node now since we're going to need it anyway */
866 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
869 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
870 edit->adjust_count_on = new_n0;
872 /* Insert a new shortcut before the new node if this segment isn't of
873 * zero length - otherwise we just connect the new node directly to the
876 level += ASSOC_ARRAY_LEVEL_STEP;
878 pr_devel("pre-shortcut %d...%d\n", level, diff);
879 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
880 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
882 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
883 keylen * sizeof(unsigned long), GFP_KERNEL);
886 edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
887 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
888 new_s0->back_pointer = shortcut->back_pointer;
889 new_s0->parent_slot = shortcut->parent_slot;
890 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
891 new_s0->skip_to_level = diff;
893 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
894 new_n0->parent_slot = 0;
896 memcpy(new_s0->index_key, shortcut->index_key,
897 keylen * sizeof(unsigned long));
899 blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
900 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
901 new_s0->index_key[keylen - 1] &= ~blank;
903 pr_devel("no pre-shortcut\n");
904 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
905 new_n0->back_pointer = shortcut->back_pointer;
906 new_n0->parent_slot = shortcut->parent_slot;
909 side = assoc_array_ptr_to_node(shortcut->next_node);
910 new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;
912 /* We need to know which slot in the new node is going to take a
915 sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
916 sc_slot &= ASSOC_ARRAY_FAN_MASK;
918 pr_devel("new slot %lx >> %d -> %d\n",
919 sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);
921 /* Determine whether we need to follow the new node with a replacement
922 * for the current shortcut. We could in theory reuse the current
923 * shortcut if its parent slot number doesn't change - but that's a
924 * 1-in-16 chance so not worth expending the code upon.
926 level = diff + ASSOC_ARRAY_LEVEL_STEP;
927 if (level < shortcut->skip_to_level) {
928 pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);
929 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
930 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
932 new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
933 keylen * sizeof(unsigned long), GFP_KERNEL);
936 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
938 new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);
939 new_s1->parent_slot = sc_slot;
940 new_s1->next_node = shortcut->next_node;
941 new_s1->skip_to_level = shortcut->skip_to_level;
943 new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
945 memcpy(new_s1->index_key, shortcut->index_key,
946 keylen * sizeof(unsigned long));
948 edit->set[1].ptr = &side->back_pointer;
949 edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
951 pr_devel("no post-shortcut\n");
953 /* We don't have to replace the pointed-to node as long as we
954 * use memory barriers to make sure the parent slot number is
955 * changed before the back pointer (the parent slot number is
956 * irrelevant to the old parent shortcut).
958 new_n0->slots[sc_slot] = shortcut->next_node;
959 edit->set_parent_slot[0].p = &side->parent_slot;
960 edit->set_parent_slot[0].to = sc_slot;
961 edit->set[1].ptr = &side->back_pointer;
962 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
965 /* Install the new leaf in a spare slot in the new node. */
967 edit->leaf_p = &new_n0->slots[1];
969 edit->leaf_p = &new_n0->slots[0];
971 pr_devel("<--%s() = ok [split shortcut]\n", __func__);
976 * assoc_array_insert - Script insertion of an object into an associative array
977 * @array: The array to insert into.
978 * @ops: The operations to use.
979 * @index_key: The key to insert at.
980 * @object: The object to insert.
982 * Precalculate and preallocate a script for the insertion or replacement of an
983 * object in an associative array. This results in an edit script that can
984 * either be applied or cancelled.
986 * The function returns a pointer to an edit script or -ENOMEM.
988 * The caller should lock against other modifications and must continue to hold
989 * the lock until assoc_array_apply_edit() has been called.
991 * Accesses to the tree may take place concurrently with this function,
992 * provided they hold the RCU read lock.
994 struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
995 const struct assoc_array_ops *ops,
996 const void *index_key,
999 struct assoc_array_walk_result result;
1000 struct assoc_array_edit *edit;
1002 pr_devel("-->%s()\n", __func__);
1004 /* The leaf pointer we're given must not have the bottom bit set as we
1005 * use those for type-marking the pointer. NULL pointers are also not
1006 * allowed as they indicate an empty slot but we have to allow them
1007 * here as they can be updated later.
1009 BUG_ON(assoc_array_ptr_is_meta(object));
1011 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1013 return ERR_PTR(-ENOMEM);
1014 edit->array = array;
1016 edit->leaf = assoc_array_leaf_to_ptr(object);
1017 edit->adjust_count_by = 1;
1019 switch (assoc_array_walk(array, ops, index_key, &result)) {
1020 case assoc_array_walk_tree_empty:
1021 /* Allocate a root node if there isn't one yet */
1022 if (!assoc_array_insert_in_empty_tree(edit))
1026 case assoc_array_walk_found_terminal_node:
1027 /* We found a node that doesn't have a node/shortcut pointer in
1028 * the slot corresponding to the index key that we have to
1031 if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,
1036 case assoc_array_walk_found_wrong_shortcut:
1037 /* We found a shortcut that didn't match our key in a slot we
1040 if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
1046 /* Clean up after an out of memory error */
1047 pr_devel("enomem\n");
1048 assoc_array_cancel_edit(edit);
1049 return ERR_PTR(-ENOMEM);
1053 * assoc_array_insert_set_object - Set the new object pointer in an edit script
1054 * @edit: The edit script to modify.
1055 * @object: The object pointer to set.
1057 * Change the object to be inserted in an edit script. The object pointed to
1058 * by the old object is not freed. This must be done prior to applying the
1061 void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)
1064 edit->leaf = assoc_array_leaf_to_ptr(object);
1067 struct assoc_array_delete_collapse_context {
1068 struct assoc_array_node *node;
1069 const void *skip_leaf;
1074 * Subtree collapse to node iterator.
1076 static int assoc_array_delete_collapse_iterator(const void *leaf,
1077 void *iterator_data)
1079 struct assoc_array_delete_collapse_context *collapse = iterator_data;
1081 if (leaf == collapse->skip_leaf)
1084 BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);
1086 collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);
1091 * assoc_array_delete - Script deletion of an object from an associative array
1092 * @array: The array to search.
1093 * @ops: The operations to use.
1094 * @index_key: The key to the object.
1096 * Precalculate and preallocate a script for the deletion of an object from an
1097 * associative array. This results in an edit script that can either be
1098 * applied or cancelled.
1100 * The function returns a pointer to an edit script if the object was found,
1101 * NULL if the object was not found or -ENOMEM.
1103 * The caller should lock against other modifications and must continue to hold
1104 * the lock until assoc_array_apply_edit() has been called.
1106 * Accesses to the tree may take place concurrently with this function,
1107 * provided they hold the RCU read lock.
1109 struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
1110 const struct assoc_array_ops *ops,
1111 const void *index_key)
1113 struct assoc_array_delete_collapse_context collapse;
1114 struct assoc_array_walk_result result;
1115 struct assoc_array_node *node, *new_n0;
1116 struct assoc_array_edit *edit;
1117 struct assoc_array_ptr *ptr;
1121 pr_devel("-->%s()\n", __func__);
1123 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1125 return ERR_PTR(-ENOMEM);
1126 edit->array = array;
1128 edit->adjust_count_by = -1;
1130 switch (assoc_array_walk(array, ops, index_key, &result)) {
1131 case assoc_array_walk_found_terminal_node:
1132 /* We found a node that should contain the leaf we've been
1133 * asked to remove - *if* it's in the tree.
1135 pr_devel("terminal_node\n");
1136 node = result.terminal_node.node;
1138 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1139 ptr = node->slots[slot];
1141 assoc_array_ptr_is_leaf(ptr) &&
1142 ops->compare_object(assoc_array_ptr_to_leaf(ptr),
1146 case assoc_array_walk_tree_empty:
1147 case assoc_array_walk_found_wrong_shortcut:
1149 assoc_array_cancel_edit(edit);
1150 pr_devel("not found\n");
1155 BUG_ON(array->nr_leaves_on_tree <= 0);
1157 /* In the simplest form of deletion we just clear the slot and release
1158 * the leaf after a suitable interval.
1160 edit->dead_leaf = node->slots[slot];
1161 edit->set[0].ptr = &node->slots[slot];
1162 edit->set[0].to = NULL;
1163 edit->adjust_count_on = node;
1165 /* If that concludes erasure of the last leaf, then delete the entire
1168 if (array->nr_leaves_on_tree == 1) {
1169 edit->set[1].ptr = &array->root;
1170 edit->set[1].to = NULL;
1171 edit->adjust_count_on = NULL;
1172 edit->excised_subtree = array->root;
1173 pr_devel("all gone\n");
1177 /* However, we'd also like to clear up some metadata blocks if we
1180 * We go for a simple algorithm of: if this node has FAN_OUT or fewer
1181 * leaves in it, then attempt to collapse it - and attempt to
1182 * recursively collapse up the tree.
1184 * We could also try and collapse in partially filled subtrees to take
1185 * up space in this node.
1187 if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
1188 struct assoc_array_node *parent, *grandparent;
1189 struct assoc_array_ptr *ptr;
1191 /* First of all, we need to know if this node has metadata so
1192 * that we don't try collapsing if all the leaves are already
1196 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
1197 ptr = node->slots[i];
1198 if (assoc_array_ptr_is_meta(ptr)) {
1204 pr_devel("leaves: %ld [m=%d]\n",
1205 node->nr_leaves_on_branch - 1, has_meta);
1207 /* Look further up the tree to see if we can collapse this node
1208 * into a more proximal node too.
1212 pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);
1214 ptr = parent->back_pointer;
1217 if (assoc_array_ptr_is_shortcut(ptr)) {
1218 struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);
1219 ptr = s->back_pointer;
1224 grandparent = assoc_array_ptr_to_node(ptr);
1225 if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
1226 parent = grandparent;
1231 /* There's no point collapsing if the original node has no meta
1232 * pointers to discard and if we didn't merge into one of that
1235 if (has_meta || parent != node) {
1238 /* Create a new node to collapse into */
1239 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
1242 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
1244 new_n0->back_pointer = node->back_pointer;
1245 new_n0->parent_slot = node->parent_slot;
1246 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
1247 edit->adjust_count_on = new_n0;
1249 collapse.node = new_n0;
1250 collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);
1252 assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),
1254 assoc_array_delete_collapse_iterator,
1256 pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);
1257 BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);
1259 if (!node->back_pointer) {
1260 edit->set[1].ptr = &array->root;
1261 } else if (assoc_array_ptr_is_leaf(node->back_pointer)) {
1263 } else if (assoc_array_ptr_is_node(node->back_pointer)) {
1264 struct assoc_array_node *p =
1265 assoc_array_ptr_to_node(node->back_pointer);
1266 edit->set[1].ptr = &p->slots[node->parent_slot];
1267 } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {
1268 struct assoc_array_shortcut *s =
1269 assoc_array_ptr_to_shortcut(node->back_pointer);
1270 edit->set[1].ptr = &s->next_node;
1272 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
1273 edit->excised_subtree = assoc_array_node_to_ptr(node);
1280 /* Clean up after an out of memory error */
1281 pr_devel("enomem\n");
1282 assoc_array_cancel_edit(edit);
1283 return ERR_PTR(-ENOMEM);
1287 * assoc_array_clear - Script deletion of all objects from an associative array
1288 * @array: The array to clear.
1289 * @ops: The operations to use.
1291 * Precalculate and preallocate a script for the deletion of all the objects
1292 * from an associative array. This results in an edit script that can either
1293 * be applied or cancelled.
1295 * The function returns a pointer to an edit script if there are objects to be
1296 * deleted, NULL if there are no objects in the array or -ENOMEM.
1298 * The caller should lock against other modifications and must continue to hold
1299 * the lock until assoc_array_apply_edit() has been called.
1301 * Accesses to the tree may take place concurrently with this function,
1302 * provided they hold the RCU read lock.
1304 struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,
1305 const struct assoc_array_ops *ops)
1307 struct assoc_array_edit *edit;
1309 pr_devel("-->%s()\n", __func__);
1314 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1316 return ERR_PTR(-ENOMEM);
1317 edit->array = array;
1319 edit->set[1].ptr = &array->root;
1320 edit->set[1].to = NULL;
1321 edit->excised_subtree = array->root;
1322 edit->ops_for_excised_subtree = ops;
1323 pr_devel("all gone\n");
1328 * Handle the deferred destruction after an applied edit.
1330 static void assoc_array_rcu_cleanup(struct rcu_head *head)
1332 struct assoc_array_edit *edit =
1333 container_of(head, struct assoc_array_edit, rcu);
1336 pr_devel("-->%s()\n", __func__);
1338 if (edit->dead_leaf)
1339 edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));
1340 for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)
1341 if (edit->excised_meta[i])
1342 kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));
1344 if (edit->excised_subtree) {
1345 BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));
1346 if (assoc_array_ptr_is_node(edit->excised_subtree)) {
1347 struct assoc_array_node *n =
1348 assoc_array_ptr_to_node(edit->excised_subtree);
1349 n->back_pointer = NULL;
1351 struct assoc_array_shortcut *s =
1352 assoc_array_ptr_to_shortcut(edit->excised_subtree);
1353 s->back_pointer = NULL;
1355 assoc_array_destroy_subtree(edit->excised_subtree,
1356 edit->ops_for_excised_subtree);
1363 * assoc_array_apply_edit - Apply an edit script to an associative array
1364 * @edit: The script to apply.
1366 * Apply an edit script to an associative array to effect an insertion,
1367 * deletion or clearance. As the edit script includes preallocated memory,
1368 * this is guaranteed not to fail.
1370 * The edit script, dead objects and dead metadata will be scheduled for
1371 * destruction after an RCU grace period to permit those doing read-only
1372 * accesses on the array to continue to do so under the RCU read lock whilst
1373 * the edit is taking place.
1375 void assoc_array_apply_edit(struct assoc_array_edit *edit)
1377 struct assoc_array_shortcut *shortcut;
1378 struct assoc_array_node *node;
1379 struct assoc_array_ptr *ptr;
1382 pr_devel("-->%s()\n", __func__);
1386 *edit->leaf_p = edit->leaf;
1389 for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)
1390 if (edit->set_parent_slot[i].p)
1391 *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;
1394 for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)
1395 if (edit->set_backpointers[i])
1396 *edit->set_backpointers[i] = edit->set_backpointers_to;
1399 for (i = 0; i < ARRAY_SIZE(edit->set); i++)
1400 if (edit->set[i].ptr)
1401 *edit->set[i].ptr = edit->set[i].to;
1403 if (edit->array->root == NULL) {
1404 edit->array->nr_leaves_on_tree = 0;
1405 } else if (edit->adjust_count_on) {
1406 node = edit->adjust_count_on;
1408 node->nr_leaves_on_branch += edit->adjust_count_by;
1410 ptr = node->back_pointer;
1413 if (assoc_array_ptr_is_shortcut(ptr)) {
1414 shortcut = assoc_array_ptr_to_shortcut(ptr);
1415 ptr = shortcut->back_pointer;
1419 BUG_ON(!assoc_array_ptr_is_node(ptr));
1420 node = assoc_array_ptr_to_node(ptr);
1423 edit->array->nr_leaves_on_tree += edit->adjust_count_by;
1426 call_rcu(&edit->rcu, assoc_array_rcu_cleanup);
1430 * assoc_array_cancel_edit - Discard an edit script.
1431 * @edit: The script to discard.
1433 * Free an edit script and all the preallocated data it holds without making
1434 * any changes to the associative array it was intended for.
1436 * NOTE! In the case of an insertion script, this does _not_ release the leaf
1437 * that was to be inserted. That is left to the caller.
1439 void assoc_array_cancel_edit(struct assoc_array_edit *edit)
1441 struct assoc_array_ptr *ptr;
1444 pr_devel("-->%s()\n", __func__);
1446 /* Clean up after an out of memory error */
1447 for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {
1448 ptr = edit->new_meta[i];
1450 if (assoc_array_ptr_is_node(ptr))
1451 kfree(assoc_array_ptr_to_node(ptr));
1453 kfree(assoc_array_ptr_to_shortcut(ptr));
1460 * assoc_array_gc - Garbage collect an associative array.
1461 * @array: The array to clean.
1462 * @ops: The operations to use.
1463 * @iterator: A callback function to pass judgement on each object.
1464 * @iterator_data: Private data for the callback function.
1466 * Collect garbage from an associative array and pack down the internal tree to
1469 * The iterator function is asked to pass judgement upon each object in the
1470 * array. If it returns false, the object is discard and if it returns true,
1471 * the object is kept. If it returns true, it must increment the object's
1472 * usage count (or whatever it needs to do to retain it) before returning.
1474 * This function returns 0 if successful or -ENOMEM if out of memory. In the
1475 * latter case, the array is not changed.
1477 * The caller should lock against other modifications and must continue to hold
1478 * the lock until assoc_array_apply_edit() has been called.
1480 * Accesses to the tree may take place concurrently with this function,
1481 * provided they hold the RCU read lock.
1483 int assoc_array_gc(struct assoc_array *array,
1484 const struct assoc_array_ops *ops,
1485 bool (*iterator)(void *object, void *iterator_data),
1486 void *iterator_data)
1488 struct assoc_array_shortcut *shortcut, *new_s;
1489 struct assoc_array_node *node, *new_n;
1490 struct assoc_array_edit *edit;
1491 struct assoc_array_ptr *cursor, *ptr;
1492 struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;
1493 unsigned long nr_leaves_on_tree;
1494 int keylen, slot, nr_free, next_slot, i;
1496 pr_devel("-->%s()\n", __func__);
1501 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1504 edit->array = array;
1506 edit->ops_for_excised_subtree = ops;
1507 edit->set[0].ptr = &array->root;
1508 edit->excised_subtree = array->root;
1510 new_root = new_parent = NULL;
1511 new_ptr_pp = &new_root;
1512 cursor = array->root;
1515 /* If this point is a shortcut, then we need to duplicate it and
1516 * advance the target cursor.
1518 if (assoc_array_ptr_is_shortcut(cursor)) {
1519 shortcut = assoc_array_ptr_to_shortcut(cursor);
1520 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
1521 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
1522 new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
1523 keylen * sizeof(unsigned long), GFP_KERNEL);
1526 pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
1527 memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
1528 keylen * sizeof(unsigned long)));
1529 new_s->back_pointer = new_parent;
1530 new_s->parent_slot = shortcut->parent_slot;
1531 *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
1532 new_ptr_pp = &new_s->next_node;
1533 cursor = shortcut->next_node;
1536 /* Duplicate the node at this position */
1537 node = assoc_array_ptr_to_node(cursor);
1538 new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
1541 pr_devel("dup node %p -> %p\n", node, new_n);
1542 new_n->back_pointer = new_parent;
1543 new_n->parent_slot = node->parent_slot;
1544 *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);
1549 /* Filter across any leaves and gc any subtrees */
1550 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1551 ptr = node->slots[slot];
1555 if (assoc_array_ptr_is_leaf(ptr)) {
1556 if (iterator(assoc_array_ptr_to_leaf(ptr),
1558 /* The iterator will have done any reference
1559 * counting on the object for us.
1561 new_n->slots[slot] = ptr;
1565 new_ptr_pp = &new_n->slots[slot];
1570 pr_devel("-- compress node %p --\n", new_n);
1572 /* Count up the number of empty slots in this node and work out the
1573 * subtree leaf count.
1575 new_n->nr_leaves_on_branch = 0;
1577 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1578 ptr = new_n->slots[slot];
1581 else if (assoc_array_ptr_is_leaf(ptr))
1582 new_n->nr_leaves_on_branch++;
1584 pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);
1586 /* See what we can fold in */
1588 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1589 struct assoc_array_shortcut *s;
1590 struct assoc_array_node *child;
1592 ptr = new_n->slots[slot];
1593 if (!ptr || assoc_array_ptr_is_leaf(ptr))
1597 if (assoc_array_ptr_is_shortcut(ptr)) {
1598 s = assoc_array_ptr_to_shortcut(ptr);
1602 child = assoc_array_ptr_to_node(ptr);
1603 new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;
1605 if (child->nr_leaves_on_branch <= nr_free + 1) {
1606 /* Fold the child node into this one */
1607 pr_devel("[%d] fold node %lu/%d [nx %d]\n",
1608 slot, child->nr_leaves_on_branch, nr_free + 1,
1611 /* We would already have reaped an intervening shortcut
1612 * on the way back up the tree.
1616 new_n->slots[slot] = NULL;
1618 if (slot < next_slot)
1620 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
1621 struct assoc_array_ptr *p = child->slots[i];
1624 BUG_ON(assoc_array_ptr_is_meta(p));
1625 while (new_n->slots[next_slot])
1627 BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);
1628 new_n->slots[next_slot++] = p;
1633 pr_devel("[%d] retain node %lu/%d [nx %d]\n",
1634 slot, child->nr_leaves_on_branch, nr_free + 1,
1639 pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);
1641 nr_leaves_on_tree = new_n->nr_leaves_on_branch;
1643 /* Excise this node if it is singly occupied by a shortcut */
1644 if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {
1645 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)
1646 if ((ptr = new_n->slots[slot]))
1649 if (assoc_array_ptr_is_meta(ptr) &&
1650 assoc_array_ptr_is_shortcut(ptr)) {
1651 pr_devel("excise node %p with 1 shortcut\n", new_n);
1652 new_s = assoc_array_ptr_to_shortcut(ptr);
1653 new_parent = new_n->back_pointer;
1654 slot = new_n->parent_slot;
1657 new_s->back_pointer = NULL;
1658 new_s->parent_slot = 0;
1663 if (assoc_array_ptr_is_shortcut(new_parent)) {
1664 /* We can discard any preceding shortcut also */
1665 struct assoc_array_shortcut *s =
1666 assoc_array_ptr_to_shortcut(new_parent);
1668 pr_devel("excise preceding shortcut\n");
1670 new_parent = new_s->back_pointer = s->back_pointer;
1671 slot = new_s->parent_slot = s->parent_slot;
1674 new_s->back_pointer = NULL;
1675 new_s->parent_slot = 0;
1681 new_s->back_pointer = new_parent;
1682 new_s->parent_slot = slot;
1683 new_n = assoc_array_ptr_to_node(new_parent);
1684 new_n->slots[slot] = ptr;
1685 goto ascend_old_tree;
1689 /* Excise any shortcuts we might encounter that point to nodes that
1690 * only contain leaves.
1692 ptr = new_n->back_pointer;
1696 if (assoc_array_ptr_is_shortcut(ptr)) {
1697 new_s = assoc_array_ptr_to_shortcut(ptr);
1698 new_parent = new_s->back_pointer;
1699 slot = new_s->parent_slot;
1701 if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
1702 struct assoc_array_node *n;
1704 pr_devel("excise shortcut\n");
1705 new_n->back_pointer = new_parent;
1706 new_n->parent_slot = slot;
1709 new_root = assoc_array_node_to_ptr(new_n);
1713 n = assoc_array_ptr_to_node(new_parent);
1714 n->slots[slot] = assoc_array_node_to_ptr(new_n);
1719 new_n = assoc_array_ptr_to_node(new_parent);
1722 ptr = node->back_pointer;
1723 if (assoc_array_ptr_is_shortcut(ptr)) {
1724 shortcut = assoc_array_ptr_to_shortcut(ptr);
1725 slot = shortcut->parent_slot;
1726 cursor = shortcut->back_pointer;
1730 slot = node->parent_slot;
1734 node = assoc_array_ptr_to_node(cursor);
1739 edit->set[0].to = new_root;
1740 assoc_array_apply_edit(edit);
1741 array->nr_leaves_on_tree = nr_leaves_on_tree;
1745 pr_devel("enomem\n");
1746 assoc_array_destroy_subtree(new_root, edit->ops);