1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* 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 DEBUG
10 #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 lock
17 * or better.
18 */
19 static 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
33 begin_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 we
46 * don't miss any leaves if the node is split up by insertion whilst
47 * we're iterating over the branches rooted here (we may, however, see
48 * 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 follow
67 * one of these we may find that we don't come back here, but rather go
68 * 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 for
71 * a particular portion of the key space cannot change - and we
72 * continue at the back pointer + 1.
73 */
74 if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))
75 goto finished_node;
76 slot = 0;
77
78 continue_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
88 finished_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 callback
112 * @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 be
117 * presented to the iterator function.
118 *
119 * If the array is being modified concurrently with the iteration then it is
120 * possible that some objects in the array will be passed to the iterator
121 * callback more than once - though every object should be passed at least
122 * once. If this is undesirable then the caller must lock against modification
123 * for the duration of this function.
124 *
125 * The function will return 0 if no objects were in the array or else it will
126 * return the result of the last iterator function called. Iteration stops
127 * immediately if any call to the iteration function results in a non-zero
128 * return.
129 *
130 * The caller should hold the RCU read lock or better if concurrent
131 * modification is possible.
132 */
133 int 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
145 enum 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
151 struct 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 */
169 static enum assoc_array_walk_status
170 assoc_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 the
192 * internal tree, skipping through nodes and shortcuts that are on
193 * route to the destination. Eventually we'll come to a slot that is
194 * either empty or contains a leaf at which point we've found a node in
195 * which the leaf we're looking for might be found or into which it
196 * should be inserted.
197 */
198 jumped:
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
205 consider_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 slot
216 * 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 to
227 * 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 key
237 * segment. We follow the shortcut if its partial index key matches
238 * this leaf's. Otherwise we need to split the shortcut.
239 */
240 cursor = ptr;
241 follow_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 a
249 * time, trimming the final word (the shortcut stores the index
250 * 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 key
294 * @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 tree
299 * to the node that should contain the object and then searching the leaves
300 * 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 */
304 void *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 by
321 * 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 pointer
327 * and dereferencing the pointer - but only if we are
328 * 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 prevent
341 * other simultaneous accesses.
342 */
343 static 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
359 move_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
379 continue_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 on
405 * 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 array
430 * @array: The array to destroy.
431 * @ops: The operations to use.
432 *
433 * Discard all metadata and free all objects in an associative array. The
434 * array will be empty and ready to use again upon completion. This function
435 * cannot fail.
436 *
437 * The caller must prevent all other accesses whilst this takes place as no
438 * attempt is made to adjust pointers gracefully to permit RCU readlock-holding
439 * accesses to continue. On the other hand, no memory allocation is required.
440 */
441 void 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 */
451 static 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 */
474 static 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 shortcut
495 * pointer that we have to follow. This means that (a) the leaf we
496 * want must go here (either by insertion or replacement) or (b) we
497 * 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's
502 * 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 the
522 * 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 split
533 * it or insert another node before it.
534 *
535 * Whatever, we're going to need at least two new nodes - so allocate
536 * those now. We may also need a new shortcut, but we deal with that
537 * 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 need
579 * 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, but
585 * the new leaf wants to go into a different slot - so we
586 * create a new node (n0) to hold the new leaf and a pointer to
587 * a new node (n1) holding all the old leaves.
588 *
589 * This can be done by falling through to the node splitting
590 * path.
591 */
592 pr_devel("present leaves cluster but not new leaf\n");
593 }
594
595 split_node:
596 pr_devel("split node\n");
597
598 /* We need to split the current node. The node must contain anything
599 * from a single leaf (in the one leaf case, this leaf will cluster
600 * with the new leaf) and the rest meta-pointers, to all leaves, some
601 * of which may cluster.
602 *
603 * It won't contain the case in which all the current leaves plus the
604 * 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 the
607 * leaves in the node and the new leaf. The current meta pointers can
608 * 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 to
611 * 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
619 do_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 two
626 * that match - even if there are meta pointers - because any leaf that
627 * would match a slot with a meta pointer in it must be somewhere
628 * behind that meta pointer and cannot be here. Further, given N
629 * 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 }
638 found_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 else
651 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 else
708 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
713 all_leaves_cluster_together:
714 /* All the leaves, new and old, want to cluster together in this node
715 * in the same slot, so we have to replace this node with a shortcut to
716 * skip over the identical parts of the key and then place a pair of
717 * nodes, one inside the other, at the end of the shortcut and
718 * distribute the keys between them.
719 *
720 * Firstly we need to work out where the leaves start diverging as a
721 * bit position into their keys so that we know how big the shortcut
722 * needs to be.
723 *
724 * We only need to make a single pass of N of the N+1 leaves because if
725 * any keys differ between themselves at bit X then at least one of
726 * 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 need
773 * 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 */
792 static 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 two
813 * pieces. Zero-length pieces will be dispensed with entirely.
814 *
815 * First of all, we need to find out in which level the first
816 * 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 of
842 * zero length - otherwise we just connect the new node directly to the
843 * 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 a
882 * 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 replacement
891 * for the current shortcut. We could in theory reuse the current
892 * shortcut if its parent slot number doesn't change - but that's a
893 * 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 we
923 * use memory barriers to make sure the parent slot number is
924 * changed before the back pointer (the parent slot number is
925 * 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 else
938 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 array
946 * @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 an
952 * object in an associative array. This results in an edit script that can
953 * 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 hold
958 * 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 */
963 struct 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 we
974 * use those for type-marking the pointer. NULL pointers are also not
975 * allowed as they indicate an empty slot but we have to allow them
976 * 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 in
997 * the slot corresponding to the index key that we have to
998 * 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 we
1007 * needed to follow.
1008 */
1009 if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
1010 goto enomem;
1011 return edit;
1012 }
1013
1014 enomem:
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 script
1023 * @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 to
1027 * by the old object is not freed. This must be done prior to applying the
1028 * script.
1029 */
1030 void 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
1036 struct 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 */
1045 static 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 array
1061 * @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 an
1066 * associative array. This results in an edit script that can either be
1067 * 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 hold
1073 * 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 */
1078 struct 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 been
1102 * 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
1124 found_leaf:
1125 BUG_ON(array->nr_leaves_on_tree <= 0);
1126
1127 /* In the simplest form of deletion we just clear the slot and release
1128 * 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 entire
1136 * 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 we
1148 * possibly can.
1149 *
1150 * We go for a simple algorithm of: if this node has FAN_OUT or fewer
1151 * leaves in it, then attempt to collapse it - and attempt to
1152 * recursively collapse up the tree.
1153 *
1154 * We could also try and collapse in partially filled subtrees to take
1155 * 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 so
1162 * that we don't try collapsing if all the leaves are already
1163 * 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 node
1178 * 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 meta
1202 * pointers to discard and if we didn't merge into one of that
1203 * 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
1249 enomem:
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 array
1258 * @array: The array to clear.
1259 * @ops: The operations to use.
1260 *
1261 * Precalculate and preallocate a script for the deletion of all the objects
1262 * from an associative array. This results in an edit script that can either
1263 * be applied or cancelled.
1264 *
1265 * The function returns a pointer to an edit script if there are objects to be
1266 * 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 hold
1269 * 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 */
1274 struct 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 */
1300 static 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 array
1334 * @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 for
1341 * destruction after an RCU grace period to permit those doing read-only
1342 * accesses on the array to continue to do so under the RCU read lock whilst
1343 * the edit is taking place.
1344 */
1345 void 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 making
1404 * 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 leaf
1407 * that was to be inserted. That is left to the caller.
1408 */
1409 void 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 else
1423 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 to
1437 * save memory.
1438 *
1439 * The iterator function is asked to pass judgement upon each object in the
1440 * 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's
1442 * 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 the
1445 * latter case, the array is not changed.
1446 *
1447 * The caller should lock against other modifications and must continue to hold
1448 * 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 */
1453 int 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
1485 descend:
1486 /* If this point is a shortcut, then we need to duplicate it and
1487 * 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
1518 continue_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 reference
1529 * 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
1540 retry_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 the
1544 * 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 shortcut
1584 * 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 that
1667 * 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
1698 ascend_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
1715 gc_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
1721 enomem:
1722 pr_devel("enomem\n");
1723 assoc_array_destroy_subtree(new_root, edit->ops);
1724 kfree(edit);
1725 return -ENOMEM;
1726 }
1727
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