projects/linux·blob v4.13-rc4 · refs

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1/* Generic associative array implementation.
2 *
3 * See Documentation/assoc_array.txt for information.
4 *
5 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells ([email protected])
7 *
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.
12 */
13//#define DEBUG
14#include <linux/rcupdate.h>
15#include <linux/slab.h>
16#include <linux/err.h>
17#include <linux/assoc_array_priv.h>
18
19/*
20 * Iterate over an associative array. The caller must hold the RCU read lock
21 * or better.
22 */
23static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
24 const struct assoc_array_ptr *stop,
25 int (*iterator)(const void *leaf,
26 void *iterator_data),
27 void *iterator_data)
28{
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;
33 int slot, ret;
34
35 cursor = root;
36
37begin_node:
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);
43 }
44
45 node = assoc_array_ptr_to_node(cursor);
46 smp_read_barrier_depends();
47 slot = 0;
48
49 /* We perform two passes of each node.
50 *
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
54 * some leaves twice).
55 */
56 has_meta = 0;
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.
64 */
65 smp_read_barrier_depends();
66
67 /* Invoke the callback */
68 ret = iterator(assoc_array_ptr_to_leaf(ptr),
69 iterator_data);
70 if (ret)
71 return ret;
72 }
73 }
74
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.
78 *
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.
82 */
83 if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))
84 goto finished_node;
85 slot = 0;
86
87continue_node:
88 node = assoc_array_ptr_to_node(cursor);
89 smp_read_barrier_depends();
90
91 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
92 ptr = ACCESS_ONCE(node->slots[slot]);
93 if (assoc_array_ptr_is_meta(ptr)) {
94 cursor = ptr;
95 goto begin_node;
96 }
97 }
98
99finished_node:
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;
103 if (parent == stop)
104 return 0;
105
106 if (assoc_array_ptr_is_shortcut(parent)) {
107 shortcut = assoc_array_ptr_to_shortcut(parent);
108 smp_read_barrier_depends();
109 cursor = parent;
110 parent = ACCESS_ONCE(shortcut->back_pointer);
111 slot = shortcut->parent_slot;
112 if (parent == stop)
113 return 0;
114 }
115
116 /* Ascend to next slot in parent node */
117 cursor = parent;
118 slot++;
119 goto continue_node;
120}
121
122/**
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.
127 *
128 * Iterate over all the objects in an associative array. Each one will be
129 * presented to the iterator function.
130 *
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.
136 *
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
140 * return.
141 *
142 * The caller should hold the RCU read lock or better if concurrent
143 * modification is possible.
144 */
145int assoc_array_iterate(const struct assoc_array *array,
146 int (*iterator)(const void *object,
147 void *iterator_data),
148 void *iterator_data)
149{
150 struct assoc_array_ptr *root = ACCESS_ONCE(array->root);
151
152 if (!root)
153 return 0;
154 return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data);
155}
156
157enum assoc_array_walk_status {
158 assoc_array_walk_tree_empty,
159 assoc_array_walk_found_terminal_node,
160 assoc_array_walk_found_wrong_shortcut,
161};
162
163struct assoc_array_walk_result {
164 struct {
165 struct assoc_array_node *node; /* Node in which leaf might be found */
166 int level;
167 int slot;
168 } terminal_node;
169 struct {
170 struct assoc_array_shortcut *shortcut;
171 int level;
172 int sc_level;
173 unsigned long sc_segments;
174 unsigned long dissimilarity;
175 } wrong_shortcut;
176};
177
178/*
179 * Navigate through the internal tree looking for the closest node to the key.
180 */
181static enum assoc_array_walk_status
182assoc_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)
186{
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;
193 int slot;
194
195 pr_devel("-->%s()\n", __func__);
196
197 cursor = ACCESS_ONCE(array->root);
198 if (!cursor)
199 return assoc_array_walk_tree_empty;
200
201 level = 0;
202
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.
209 */
210jumped:
211 segments = ops->get_key_chunk(index_key, level);
212 pr_devel("segments[%d]: %lx\n", level, segments);
213
214 if (assoc_array_ptr_is_shortcut(cursor))
215 goto follow_shortcut;
216
217consider_node:
218 node = assoc_array_ptr_to_node(cursor);
219 smp_read_barrier_depends();
220
221 slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
222 slot &= ASSOC_ARRAY_FAN_MASK;
223 ptr = ACCESS_ONCE(node->slots[slot]);
224
225 pr_devel("consider slot %x [ix=%d type=%lu]\n",
226 slot, level, (unsigned long)ptr & 3);
227
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.
231 */
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;
237 }
238
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.
242 */
243 cursor = ptr;
244 level += ASSOC_ARRAY_LEVEL_STEP;
245 if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0)
246 goto consider_node;
247 goto jumped;
248 }
249
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.
253 */
254 cursor = ptr;
255follow_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);
261
262 do {
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).
266 */
267 if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0)
268 segments = ops->get_key_chunk(index_key, sc_level);
269
270 sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT];
271 dissimilarity = segments ^ sc_segments;
272
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;
278 } else {
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);
281 }
282
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;
291 }
292
293 sc_level = next_sc_level;
294 } while (sc_level < shortcut->skip_to_level);
295
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) {
299 level = sc_level;
300 goto jumped;
301 } else {
302 level = sc_level;
303 goto consider_node;
304 }
305}
306
307/**
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.
312 *
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.
316 *
317 * The caller must hold the RCU read lock or better.
318 */
319void *assoc_array_find(const struct assoc_array *array,
320 const struct assoc_array_ops *ops,
321 const void *index_key)
322{
323 struct assoc_array_walk_result result;
324 const struct assoc_array_node *node;
325 const struct assoc_array_ptr *ptr;
326 const void *leaf;
327 int slot;
328
329 if (assoc_array_walk(array, ops, index_key, &result) !=
330 assoc_array_walk_found_terminal_node)
331 return NULL;
332
333 node = result.terminal_node.node;
334 smp_read_barrier_depends();
335
336 /* If the target key is available to us, it's has to be pointed to by
337 * the terminal node.
338 */
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.
345 */
346 leaf = assoc_array_ptr_to_leaf(ptr);
347 smp_read_barrier_depends();
348 if (ops->compare_object(leaf, index_key))
349 return (void *)leaf;
350 }
351 }
352
353 return NULL;
354}
355
356/*
357 * Destructively iterate over an associative array. The caller must prevent
358 * other simultaneous accesses.
359 */
360static void assoc_array_destroy_subtree(struct assoc_array_ptr *root,
361 const struct assoc_array_ops *ops)
362{
363 struct assoc_array_shortcut *shortcut;
364 struct assoc_array_node *node;
365 struct assoc_array_ptr *cursor, *parent = NULL;
366 int slot = -1;
367
368 pr_devel("-->%s()\n", __func__);
369
370 cursor = root;
371 if (!cursor) {
372 pr_devel("empty\n");
373 return;
374 }
375
376move_to_meta:
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);
384 parent = cursor;
385 cursor = shortcut->next_node;
386 slot = -1;
387 BUG_ON(!assoc_array_ptr_is_node(cursor));
388 }
389
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);
394 slot = 0;
395
396continue_node:
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];
400 if (!ptr)
401 continue;
402 if (assoc_array_ptr_is_meta(ptr)) {
403 parent = cursor;
404 cursor = ptr;
405 goto move_to_meta;
406 }
407
408 if (ops) {
409 pr_devel("[%d] free leaf\n", slot);
410 ops->free_object(assoc_array_ptr_to_leaf(ptr));
411 }
412 }
413
414 parent = node->back_pointer;
415 slot = node->parent_slot;
416 pr_devel("free node\n");
417 kfree(node);
418 if (!parent)
419 return; /* Done */
420
421 /* Move back up to the parent (may need to free a shortcut on
422 * the way up) */
423 if (assoc_array_ptr_is_shortcut(parent)) {
424 shortcut = assoc_array_ptr_to_shortcut(parent);
425 BUG_ON(shortcut->next_node != cursor);
426 cursor = parent;
427 parent = shortcut->back_pointer;
428 slot = shortcut->parent_slot;
429 pr_devel("free shortcut\n");
430 kfree(shortcut);
431 if (!parent)
432 return;
433
434 BUG_ON(!assoc_array_ptr_is_node(parent));
435 }
436
437 /* Ascend to next slot in parent node */
438 pr_devel("ascend to %p[%d]\n", parent, slot);
439 cursor = parent;
440 node = assoc_array_ptr_to_node(cursor);
441 slot++;
442 goto continue_node;
443}
444
445/**
446 * assoc_array_destroy - Destroy an associative array
447 * @array: The array to destroy.
448 * @ops: The operations to use.
449 *
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
452 * cannot fail.
453 *
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.
457 */
458void assoc_array_destroy(struct assoc_array *array,
459 const struct assoc_array_ops *ops)
460{
461 assoc_array_destroy_subtree(array->root, ops);
462 array->root = NULL;
463}
464
465/*
466 * Handle insertion into an empty tree.
467 */
468static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit)
469{
470 struct assoc_array_node *new_n0;
471
472 pr_devel("-->%s()\n", __func__);
473
474 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
475 if (!new_n0)
476 return false;
477
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);
483
484 pr_devel("<--%s() = ok [no root]\n", __func__);
485 return true;
486}
487
488/*
489 * Handle insertion into a terminal node.
490 */
491static 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)
495{
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;
500 size_t keylen;
501 bool have_meta;
502 int level, diff;
503 int slot, next_slot, free_slot, i, j;
504
505 node = result->terminal_node.node;
506 level = result->terminal_node.level;
507 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot;
508
509 pr_devel("-->%s()\n", __func__);
510
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.
515 */
516 free_slot = -1;
517
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.
520 */
521 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
522 ptr = node->slots[i];
523 if (!ptr) {
524 free_slot = i;
525 continue;
526 }
527 if (assoc_array_ptr_is_leaf(ptr) &&
528 ops->compare_object(assoc_array_ptr_to_leaf(ptr),
529 index_key)) {
530 pr_devel("replace in slot %d\n", i);
531 edit->leaf_p = &node->slots[i];
532 edit->dead_leaf = node->slots[i];
533 pr_devel("<--%s() = ok [replace]\n", __func__);
534 return true;
535 }
536 }
537
538 /* If there is a free slot in this node then we can just insert the
539 * leaf here.
540 */
541 if (free_slot >= 0) {
542 pr_devel("insert in free slot %d\n", free_slot);
543 edit->leaf_p = &node->slots[free_slot];
544 edit->adjust_count_on = node;
545 pr_devel("<--%s() = ok [insert]\n", __func__);
546 return true;
547 }
548
549 /* The node has no spare slots - so we're either going to have to split
550 * it or insert another node before it.
551 *
552 * Whatever, we're going to need at least two new nodes - so allocate
553 * those now. We may also need a new shortcut, but we deal with that
554 * when we need it.
555 */
556 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
557 if (!new_n0)
558 return false;
559 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
560 new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
561 if (!new_n1)
562 return false;
563 edit->new_meta[1] = assoc_array_node_to_ptr(new_n1);
564
565 /* We need to find out how similar the leaves are. */
566 pr_devel("no spare slots\n");
567 have_meta = false;
568 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
569 ptr = node->slots[i];
570 if (assoc_array_ptr_is_meta(ptr)) {
571 edit->segment_cache[i] = 0xff;
572 have_meta = true;
573 continue;
574 }
575 base_seg = ops->get_object_key_chunk(
576 assoc_array_ptr_to_leaf(ptr), level);
577 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
578 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
579 }
580
581 if (have_meta) {
582 pr_devel("have meta\n");
583 goto split_node;
584 }
585
586 /* The node contains only leaves */
587 dissimilarity = 0;
588 base_seg = edit->segment_cache[0];
589 for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++)
590 dissimilarity |= edit->segment_cache[i] ^ base_seg;
591
592 pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity);
593
594 if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) {
595 /* The old leaves all cluster in the same slot. We will need
596 * to insert a shortcut if the new node wants to cluster with them.
597 */
598 if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0)
599 goto all_leaves_cluster_together;
600
601 /* Otherwise we can just insert a new node ahead of the old
602 * one.
603 */
604 goto present_leaves_cluster_but_not_new_leaf;
605 }
606
607split_node:
608 pr_devel("split node\n");
609
610 /* We need to split the current node; we know that the node doesn't
611 * simply contain a full set of leaves that cluster together (it
612 * contains meta pointers and/or non-clustering leaves).
613 *
614 * We need to expel at least two leaves out of a set consisting of the
615 * leaves in the node and the new leaf.
616 *
617 * We need a new node (n0) to replace the current one and a new node to
618 * take the expelled nodes (n1).
619 */
620 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
621 new_n0->back_pointer = node->back_pointer;
622 new_n0->parent_slot = node->parent_slot;
623 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
624 new_n1->parent_slot = -1; /* Need to calculate this */
625
626do_split_node:
627 pr_devel("do_split_node\n");
628
629 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
630 new_n1->nr_leaves_on_branch = 0;
631
632 /* Begin by finding two matching leaves. There have to be at least two
633 * that match - even if there are meta pointers - because any leaf that
634 * would match a slot with a meta pointer in it must be somewhere
635 * behind that meta pointer and cannot be here. Further, given N
636 * remaining leaf slots, we now have N+1 leaves to go in them.
637 */
638 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
639 slot = edit->segment_cache[i];
640 if (slot != 0xff)
641 for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)
642 if (edit->segment_cache[j] == slot)
643 goto found_slot_for_multiple_occupancy;
644 }
645found_slot_for_multiple_occupancy:
646 pr_devel("same slot: %x %x [%02x]\n", i, j, slot);
647 BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);
648 BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);
649 BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);
650
651 new_n1->parent_slot = slot;
652
653 /* Metadata pointers cannot change slot */
654 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
655 if (assoc_array_ptr_is_meta(node->slots[i]))
656 new_n0->slots[i] = node->slots[i];
657 else
658 new_n0->slots[i] = NULL;
659 BUG_ON(new_n0->slots[slot] != NULL);
660 new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);
661
662 /* Filter the leaf pointers between the new nodes */
663 free_slot = -1;
664 next_slot = 0;
665 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
666 if (assoc_array_ptr_is_meta(node->slots[i]))
667 continue;
668 if (edit->segment_cache[i] == slot) {
669 new_n1->slots[next_slot++] = node->slots[i];
670 new_n1->nr_leaves_on_branch++;
671 } else {
672 do {
673 free_slot++;
674 } while (new_n0->slots[free_slot] != NULL);
675 new_n0->slots[free_slot] = node->slots[i];
676 }
677 }
678
679 pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);
680
681 if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {
682 do {
683 free_slot++;
684 } while (new_n0->slots[free_slot] != NULL);
685 edit->leaf_p = &new_n0->slots[free_slot];
686 edit->adjust_count_on = new_n0;
687 } else {
688 edit->leaf_p = &new_n1->slots[next_slot++];
689 edit->adjust_count_on = new_n1;
690 }
691
692 BUG_ON(next_slot <= 1);
693
694 edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);
695 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
696 if (edit->segment_cache[i] == 0xff) {
697 ptr = node->slots[i];
698 BUG_ON(assoc_array_ptr_is_leaf(ptr));
699 if (assoc_array_ptr_is_node(ptr)) {
700 side = assoc_array_ptr_to_node(ptr);
701 edit->set_backpointers[i] = &side->back_pointer;
702 } else {
703 shortcut = assoc_array_ptr_to_shortcut(ptr);
704 edit->set_backpointers[i] = &shortcut->back_pointer;
705 }
706 }
707 }
708
709 ptr = node->back_pointer;
710 if (!ptr)
711 edit->set[0].ptr = &edit->array->root;
712 else if (assoc_array_ptr_is_node(ptr))
713 edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];
714 else
715 edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;
716 edit->excised_meta[0] = assoc_array_node_to_ptr(node);
717 pr_devel("<--%s() = ok [split node]\n", __func__);
718 return true;
719
720present_leaves_cluster_but_not_new_leaf:
721 /* All the old leaves cluster in the same slot, but the new leaf wants
722 * to go into a different slot, so we create a new node to hold the new
723 * leaf and a pointer to a new node holding all the old leaves.
724 */
725 pr_devel("present leaves cluster but not new leaf\n");
726
727 new_n0->back_pointer = node->back_pointer;
728 new_n0->parent_slot = node->parent_slot;
729 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
730 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
731 new_n1->parent_slot = edit->segment_cache[0];
732 new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch;
733 edit->adjust_count_on = new_n0;
734
735 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
736 new_n1->slots[i] = node->slots[i];
737
738 new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0);
739 edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]];
740
741 edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot];
742 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
743 edit->excised_meta[0] = assoc_array_node_to_ptr(node);
744 pr_devel("<--%s() = ok [insert node before]\n", __func__);
745 return true;
746
747all_leaves_cluster_together:
748 /* All the leaves, new and old, want to cluster together in this node
749 * in the same slot, so we have to replace this node with a shortcut to
750 * skip over the identical parts of the key and then place a pair of
751 * nodes, one inside the other, at the end of the shortcut and
752 * distribute the keys between them.
753 *
754 * Firstly we need to work out where the leaves start diverging as a
755 * bit position into their keys so that we know how big the shortcut
756 * needs to be.
757 *
758 * We only need to make a single pass of N of the N+1 leaves because if
759 * any keys differ between themselves at bit X then at least one of
760 * them must also differ with the base key at bit X or before.
761 */
762 pr_devel("all leaves cluster together\n");
763 diff = INT_MAX;
764 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
765 int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]),
766 index_key);
767 if (x < diff) {
768 BUG_ON(x < 0);
769 diff = x;
770 }
771 }
772 BUG_ON(diff == INT_MAX);
773 BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);
774
775 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
776 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
777
778 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
779 keylen * sizeof(unsigned long), GFP_KERNEL);
780 if (!new_s0)
781 return false;
782 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
783
784 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
785 new_s0->back_pointer = node->back_pointer;
786 new_s0->parent_slot = node->parent_slot;
787 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
788 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
789 new_n0->parent_slot = 0;
790 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
791 new_n1->parent_slot = -1; /* Need to calculate this */
792
793 new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;
794 pr_devel("skip_to_level = %d [diff %d]\n", level, diff);
795 BUG_ON(level <= 0);
796
797 for (i = 0; i < keylen; i++)
798 new_s0->index_key[i] =
799 ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
800
801 blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
802 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
803 new_s0->index_key[keylen - 1] &= ~blank;
804
805 /* This now reduces to a node splitting exercise for which we'll need
806 * to regenerate the disparity table.
807 */
808 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
809 ptr = node->slots[i];
810 base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),
811 level);
812 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
813 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
814 }
815
816 base_seg = ops->get_key_chunk(index_key, level);
817 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
818 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;
819 goto do_split_node;
820}
821
822/*
823 * Handle insertion into the middle of a shortcut.
824 */
825static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
826 const struct assoc_array_ops *ops,
827 struct assoc_array_walk_result *result)
828{
829 struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;
830 struct assoc_array_node *node, *new_n0, *side;
831 unsigned long sc_segments, dissimilarity, blank;
832 size_t keylen;
833 int level, sc_level, diff;
834 int sc_slot;
835
836 shortcut = result->wrong_shortcut.shortcut;
837 level = result->wrong_shortcut.level;
838 sc_level = result->wrong_shortcut.sc_level;
839 sc_segments = result->wrong_shortcut.sc_segments;
840 dissimilarity = result->wrong_shortcut.dissimilarity;
841
842 pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",
843 __func__, level, dissimilarity, sc_level);
844
845 /* We need to split a shortcut and insert a node between the two
846 * pieces. Zero-length pieces will be dispensed with entirely.
847 *
848 * First of all, we need to find out in which level the first
849 * difference was.
850 */
851 diff = __ffs(dissimilarity);
852 diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;
853 diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;
854 pr_devel("diff=%d\n", diff);
855
856 if (!shortcut->back_pointer) {
857 edit->set[0].ptr = &edit->array->root;
858 } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {
859 node = assoc_array_ptr_to_node(shortcut->back_pointer);
860 edit->set[0].ptr = &node->slots[shortcut->parent_slot];
861 } else {
862 BUG();
863 }
864
865 edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);
866
867 /* Create a new node now since we're going to need it anyway */
868 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
869 if (!new_n0)
870 return false;
871 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
872 edit->adjust_count_on = new_n0;
873
874 /* Insert a new shortcut before the new node if this segment isn't of
875 * zero length - otherwise we just connect the new node directly to the
876 * parent.
877 */
878 level += ASSOC_ARRAY_LEVEL_STEP;
879 if (diff > level) {
880 pr_devel("pre-shortcut %d...%d\n", level, diff);
881 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
882 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
883
884 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
885 keylen * sizeof(unsigned long), GFP_KERNEL);
886 if (!new_s0)
887 return false;
888 edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
889 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
890 new_s0->back_pointer = shortcut->back_pointer;
891 new_s0->parent_slot = shortcut->parent_slot;
892 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
893 new_s0->skip_to_level = diff;
894
895 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
896 new_n0->parent_slot = 0;
897
898 memcpy(new_s0->index_key, shortcut->index_key,
899 keylen * sizeof(unsigned long));
900
901 blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
902 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
903 new_s0->index_key[keylen - 1] &= ~blank;
904 } else {
905 pr_devel("no pre-shortcut\n");
906 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
907 new_n0->back_pointer = shortcut->back_pointer;
908 new_n0->parent_slot = shortcut->parent_slot;
909 }
910
911 side = assoc_array_ptr_to_node(shortcut->next_node);
912 new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;
913
914 /* We need to know which slot in the new node is going to take a
915 * metadata pointer.
916 */
917 sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
918 sc_slot &= ASSOC_ARRAY_FAN_MASK;
919
920 pr_devel("new slot %lx >> %d -> %d\n",
921 sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);
922
923 /* Determine whether we need to follow the new node with a replacement
924 * for the current shortcut. We could in theory reuse the current
925 * shortcut if its parent slot number doesn't change - but that's a
926 * 1-in-16 chance so not worth expending the code upon.
927 */
928 level = diff + ASSOC_ARRAY_LEVEL_STEP;
929 if (level < shortcut->skip_to_level) {
930 pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);
931 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
932 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
933
934 new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
935 keylen * sizeof(unsigned long), GFP_KERNEL);
936 if (!new_s1)
937 return false;
938 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
939
940 new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);
941 new_s1->parent_slot = sc_slot;
942 new_s1->next_node = shortcut->next_node;
943 new_s1->skip_to_level = shortcut->skip_to_level;
944
945 new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
946
947 memcpy(new_s1->index_key, shortcut->index_key,
948 keylen * sizeof(unsigned long));
949
950 edit->set[1].ptr = &side->back_pointer;
951 edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
952 } else {
953 pr_devel("no post-shortcut\n");
954
955 /* We don't have to replace the pointed-to node as long as we
956 * use memory barriers to make sure the parent slot number is
957 * changed before the back pointer (the parent slot number is
958 * irrelevant to the old parent shortcut).
959 */
960 new_n0->slots[sc_slot] = shortcut->next_node;
961 edit->set_parent_slot[0].p = &side->parent_slot;
962 edit->set_parent_slot[0].to = sc_slot;
963 edit->set[1].ptr = &side->back_pointer;
964 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
965 }
966
967 /* Install the new leaf in a spare slot in the new node. */
968 if (sc_slot == 0)
969 edit->leaf_p = &new_n0->slots[1];
970 else
971 edit->leaf_p = &new_n0->slots[0];
972
973 pr_devel("<--%s() = ok [split shortcut]\n", __func__);
974 return edit;
975}
976
977/**
978 * assoc_array_insert - Script insertion of an object into an associative array
979 * @array: The array to insert into.
980 * @ops: The operations to use.
981 * @index_key: The key to insert at.
982 * @object: The object to insert.
983 *
984 * Precalculate and preallocate a script for the insertion or replacement of an
985 * object in an associative array. This results in an edit script that can
986 * either be applied or cancelled.
987 *
988 * The function returns a pointer to an edit script or -ENOMEM.
989 *
990 * The caller should lock against other modifications and must continue to hold
991 * the lock until assoc_array_apply_edit() has been called.
992 *
993 * Accesses to the tree may take place concurrently with this function,
994 * provided they hold the RCU read lock.
995 */
996struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
997 const struct assoc_array_ops *ops,
998 const void *index_key,
999 void *object)
1000{
1001 struct assoc_array_walk_result result;
1002 struct assoc_array_edit *edit;
1003
1004 pr_devel("-->%s()\n", __func__);
1005
1006 /* The leaf pointer we're given must not have the bottom bit set as we
1007 * use those for type-marking the pointer. NULL pointers are also not
1008 * allowed as they indicate an empty slot but we have to allow them
1009 * here as they can be updated later.
1010 */
1011 BUG_ON(assoc_array_ptr_is_meta(object));
1012
1013 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1014 if (!edit)
1015 return ERR_PTR(-ENOMEM);
1016 edit->array = array;
1017 edit->ops = ops;
1018 edit->leaf = assoc_array_leaf_to_ptr(object);
1019 edit->adjust_count_by = 1;
1020
1021 switch (assoc_array_walk(array, ops, index_key, &result)) {
1022 case assoc_array_walk_tree_empty:
1023 /* Allocate a root node if there isn't one yet */
1024 if (!assoc_array_insert_in_empty_tree(edit))
1025 goto enomem;
1026 return edit;
1027
1028 case assoc_array_walk_found_terminal_node:
1029 /* We found a node that doesn't have a node/shortcut pointer in
1030 * the slot corresponding to the index key that we have to
1031 * follow.
1032 */
1033 if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,
1034 &result))
1035 goto enomem;
1036 return edit;
1037
1038 case assoc_array_walk_found_wrong_shortcut:
1039 /* We found a shortcut that didn't match our key in a slot we
1040 * needed to follow.
1041 */
1042 if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
1043 goto enomem;
1044 return edit;
1045 }
1046
1047enomem:
1048 /* Clean up after an out of memory error */
1049 pr_devel("enomem\n");
1050 assoc_array_cancel_edit(edit);
1051 return ERR_PTR(-ENOMEM);
1052}
1053
1054/**
1055 * assoc_array_insert_set_object - Set the new object pointer in an edit script
1056 * @edit: The edit script to modify.
1057 * @object: The object pointer to set.
1058 *
1059 * Change the object to be inserted in an edit script. The object pointed to
1060 * by the old object is not freed. This must be done prior to applying the
1061 * script.
1062 */
1063void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)
1064{
1065 BUG_ON(!object);
1066 edit->leaf = assoc_array_leaf_to_ptr(object);
1067}
1068
1069struct assoc_array_delete_collapse_context {
1070 struct assoc_array_node *node;
1071 const void *skip_leaf;
1072 int slot;
1073};
1074
1075/*
1076 * Subtree collapse to node iterator.
1077 */
1078static int assoc_array_delete_collapse_iterator(const void *leaf,
1079 void *iterator_data)
1080{
1081 struct assoc_array_delete_collapse_context *collapse = iterator_data;
1082
1083 if (leaf == collapse->skip_leaf)
1084 return 0;
1085
1086 BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);
1087
1088 collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);
1089 return 0;
1090}
1091
1092/**
1093 * assoc_array_delete - Script deletion of an object from an associative array
1094 * @array: The array to search.
1095 * @ops: The operations to use.
1096 * @index_key: The key to the object.
1097 *
1098 * Precalculate and preallocate a script for the deletion of an object from an
1099 * associative array. This results in an edit script that can either be
1100 * applied or cancelled.
1101 *
1102 * The function returns a pointer to an edit script if the object was found,
1103 * NULL if the object was not found or -ENOMEM.
1104 *
1105 * The caller should lock against other modifications and must continue to hold
1106 * the lock until assoc_array_apply_edit() has been called.
1107 *
1108 * Accesses to the tree may take place concurrently with this function,
1109 * provided they hold the RCU read lock.
1110 */
1111struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
1112 const struct assoc_array_ops *ops,
1113 const void *index_key)
1114{
1115 struct assoc_array_delete_collapse_context collapse;
1116 struct assoc_array_walk_result result;
1117 struct assoc_array_node *node, *new_n0;
1118 struct assoc_array_edit *edit;
1119 struct assoc_array_ptr *ptr;
1120 bool has_meta;
1121 int slot, i;
1122
1123 pr_devel("-->%s()\n", __func__);
1124
1125 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1126 if (!edit)
1127 return ERR_PTR(-ENOMEM);
1128 edit->array = array;
1129 edit->ops = ops;
1130 edit->adjust_count_by = -1;
1131
1132 switch (assoc_array_walk(array, ops, index_key, &result)) {
1133 case assoc_array_walk_found_terminal_node:
1134 /* We found a node that should contain the leaf we've been
1135 * asked to remove - *if* it's in the tree.
1136 */
1137 pr_devel("terminal_node\n");
1138 node = result.terminal_node.node;
1139
1140 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1141 ptr = node->slots[slot];
1142 if (ptr &&
1143 assoc_array_ptr_is_leaf(ptr) &&
1144 ops->compare_object(assoc_array_ptr_to_leaf(ptr),
1145 index_key))
1146 goto found_leaf;
1147 }
1148 case assoc_array_walk_tree_empty:
1149 case assoc_array_walk_found_wrong_shortcut:
1150 default:
1151 assoc_array_cancel_edit(edit);
1152 pr_devel("not found\n");
1153 return NULL;
1154 }
1155
1156found_leaf:
1157 BUG_ON(array->nr_leaves_on_tree <= 0);
1158
1159 /* In the simplest form of deletion we just clear the slot and release
1160 * the leaf after a suitable interval.
1161 */
1162 edit->dead_leaf = node->slots[slot];
1163 edit->set[0].ptr = &node->slots[slot];
1164 edit->set[0].to = NULL;
1165 edit->adjust_count_on = node;
1166
1167 /* If that concludes erasure of the last leaf, then delete the entire
1168 * internal array.
1169 */
1170 if (array->nr_leaves_on_tree == 1) {
1171 edit->set[1].ptr = &array->root;
1172 edit->set[1].to = NULL;
1173 edit->adjust_count_on = NULL;
1174 edit->excised_subtree = array->root;
1175 pr_devel("all gone\n");
1176 return edit;
1177 }
1178
1179 /* However, we'd also like to clear up some metadata blocks if we
1180 * possibly can.
1181 *
1182 * We go for a simple algorithm of: if this node has FAN_OUT or fewer
1183 * leaves in it, then attempt to collapse it - and attempt to
1184 * recursively collapse up the tree.
1185 *
1186 * We could also try and collapse in partially filled subtrees to take
1187 * up space in this node.
1188 */
1189 if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
1190 struct assoc_array_node *parent, *grandparent;
1191 struct assoc_array_ptr *ptr;
1192
1193 /* First of all, we need to know if this node has metadata so
1194 * that we don't try collapsing if all the leaves are already
1195 * here.
1196 */
1197 has_meta = false;
1198 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
1199 ptr = node->slots[i];
1200 if (assoc_array_ptr_is_meta(ptr)) {
1201 has_meta = true;
1202 break;
1203 }
1204 }
1205
1206 pr_devel("leaves: %ld [m=%d]\n",
1207 node->nr_leaves_on_branch - 1, has_meta);
1208
1209 /* Look further up the tree to see if we can collapse this node
1210 * into a more proximal node too.
1211 */
1212 parent = node;
1213 collapse_up:
1214 pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);
1215
1216 ptr = parent->back_pointer;
1217 if (!ptr)
1218 goto do_collapse;
1219 if (assoc_array_ptr_is_shortcut(ptr)) {
1220 struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);
1221 ptr = s->back_pointer;
1222 if (!ptr)
1223 goto do_collapse;
1224 }
1225
1226 grandparent = assoc_array_ptr_to_node(ptr);
1227 if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
1228 parent = grandparent;
1229 goto collapse_up;
1230 }
1231
1232 do_collapse:
1233 /* There's no point collapsing if the original node has no meta
1234 * pointers to discard and if we didn't merge into one of that
1235 * node's ancestry.
1236 */
1237 if (has_meta || parent != node) {
1238 node = parent;
1239
1240 /* Create a new node to collapse into */
1241 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
1242 if (!new_n0)
1243 goto enomem;
1244 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
1245
1246 new_n0->back_pointer = node->back_pointer;
1247 new_n0->parent_slot = node->parent_slot;
1248 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
1249 edit->adjust_count_on = new_n0;
1250
1251 collapse.node = new_n0;
1252 collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);
1253 collapse.slot = 0;
1254 assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),
1255 node->back_pointer,
1256 assoc_array_delete_collapse_iterator,
1257 &collapse);
1258 pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);
1259 BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);
1260
1261 if (!node->back_pointer) {
1262 edit->set[1].ptr = &array->root;
1263 } else if (assoc_array_ptr_is_leaf(node->back_pointer)) {
1264 BUG();
1265 } else if (assoc_array_ptr_is_node(node->back_pointer)) {
1266 struct assoc_array_node *p =
1267 assoc_array_ptr_to_node(node->back_pointer);
1268 edit->set[1].ptr = &p->slots[node->parent_slot];
1269 } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {
1270 struct assoc_array_shortcut *s =
1271 assoc_array_ptr_to_shortcut(node->back_pointer);
1272 edit->set[1].ptr = &s->next_node;
1273 }
1274 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
1275 edit->excised_subtree = assoc_array_node_to_ptr(node);
1276 }
1277 }
1278
1279 return edit;
1280
1281enomem:
1282 /* Clean up after an out of memory error */
1283 pr_devel("enomem\n");
1284 assoc_array_cancel_edit(edit);
1285 return ERR_PTR(-ENOMEM);
1286}
1287
1288/**
1289 * assoc_array_clear - Script deletion of all objects from an associative array
1290 * @array: The array to clear.
1291 * @ops: The operations to use.
1292 *
1293 * Precalculate and preallocate a script for the deletion of all the objects
1294 * from an associative array. This results in an edit script that can either
1295 * be applied or cancelled.
1296 *
1297 * The function returns a pointer to an edit script if there are objects to be
1298 * deleted, NULL if there are no objects in the array or -ENOMEM.
1299 *
1300 * The caller should lock against other modifications and must continue to hold
1301 * the lock until assoc_array_apply_edit() has been called.
1302 *
1303 * Accesses to the tree may take place concurrently with this function,
1304 * provided they hold the RCU read lock.
1305 */
1306struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,
1307 const struct assoc_array_ops *ops)
1308{
1309 struct assoc_array_edit *edit;
1310
1311 pr_devel("-->%s()\n", __func__);
1312
1313 if (!array->root)
1314 return NULL;
1315
1316 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1317 if (!edit)
1318 return ERR_PTR(-ENOMEM);
1319 edit->array = array;
1320 edit->ops = ops;
1321 edit->set[1].ptr = &array->root;
1322 edit->set[1].to = NULL;
1323 edit->excised_subtree = array->root;
1324 edit->ops_for_excised_subtree = ops;
1325 pr_devel("all gone\n");
1326 return edit;
1327}
1328
1329/*
1330 * Handle the deferred destruction after an applied edit.
1331 */
1332static void assoc_array_rcu_cleanup(struct rcu_head *head)
1333{
1334 struct assoc_array_edit *edit =
1335 container_of(head, struct assoc_array_edit, rcu);
1336 int i;
1337
1338 pr_devel("-->%s()\n", __func__);
1339
1340 if (edit->dead_leaf)
1341 edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));
1342 for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)
1343 if (edit->excised_meta[i])
1344 kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));
1345
1346 if (edit->excised_subtree) {
1347 BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));
1348 if (assoc_array_ptr_is_node(edit->excised_subtree)) {
1349 struct assoc_array_node *n =
1350 assoc_array_ptr_to_node(edit->excised_subtree);
1351 n->back_pointer = NULL;
1352 } else {
1353 struct assoc_array_shortcut *s =
1354 assoc_array_ptr_to_shortcut(edit->excised_subtree);
1355 s->back_pointer = NULL;
1356 }
1357 assoc_array_destroy_subtree(edit->excised_subtree,
1358 edit->ops_for_excised_subtree);
1359 }
1360
1361 kfree(edit);
1362}
1363
1364/**
1365 * assoc_array_apply_edit - Apply an edit script to an associative array
1366 * @edit: The script to apply.
1367 *
1368 * Apply an edit script to an associative array to effect an insertion,
1369 * deletion or clearance. As the edit script includes preallocated memory,
1370 * this is guaranteed not to fail.
1371 *
1372 * The edit script, dead objects and dead metadata will be scheduled for
1373 * destruction after an RCU grace period to permit those doing read-only
1374 * accesses on the array to continue to do so under the RCU read lock whilst
1375 * the edit is taking place.
1376 */
1377void assoc_array_apply_edit(struct assoc_array_edit *edit)
1378{
1379 struct assoc_array_shortcut *shortcut;
1380 struct assoc_array_node *node;
1381 struct assoc_array_ptr *ptr;
1382 int i;
1383
1384 pr_devel("-->%s()\n", __func__);
1385
1386 smp_wmb();
1387 if (edit->leaf_p)
1388 *edit->leaf_p = edit->leaf;
1389
1390 smp_wmb();
1391 for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)
1392 if (edit->set_parent_slot[i].p)
1393 *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;
1394
1395 smp_wmb();
1396 for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)
1397 if (edit->set_backpointers[i])
1398 *edit->set_backpointers[i] = edit->set_backpointers_to;
1399
1400 smp_wmb();
1401 for (i = 0; i < ARRAY_SIZE(edit->set); i++)
1402 if (edit->set[i].ptr)
1403 *edit->set[i].ptr = edit->set[i].to;
1404
1405 if (edit->array->root == NULL) {
1406 edit->array->nr_leaves_on_tree = 0;
1407 } else if (edit->adjust_count_on) {
1408 node = edit->adjust_count_on;
1409 for (;;) {
1410 node->nr_leaves_on_branch += edit->adjust_count_by;
1411
1412 ptr = node->back_pointer;
1413 if (!ptr)
1414 break;
1415 if (assoc_array_ptr_is_shortcut(ptr)) {
1416 shortcut = assoc_array_ptr_to_shortcut(ptr);
1417 ptr = shortcut->back_pointer;
1418 if (!ptr)
1419 break;
1420 }
1421 BUG_ON(!assoc_array_ptr_is_node(ptr));
1422 node = assoc_array_ptr_to_node(ptr);
1423 }
1424
1425 edit->array->nr_leaves_on_tree += edit->adjust_count_by;
1426 }
1427
1428 call_rcu(&edit->rcu, assoc_array_rcu_cleanup);
1429}
1430
1431/**
1432 * assoc_array_cancel_edit - Discard an edit script.
1433 * @edit: The script to discard.
1434 *
1435 * Free an edit script and all the preallocated data it holds without making
1436 * any changes to the associative array it was intended for.
1437 *
1438 * NOTE! In the case of an insertion script, this does _not_ release the leaf
1439 * that was to be inserted. That is left to the caller.
1440 */
1441void assoc_array_cancel_edit(struct assoc_array_edit *edit)
1442{
1443 struct assoc_array_ptr *ptr;
1444 int i;
1445
1446 pr_devel("-->%s()\n", __func__);
1447
1448 /* Clean up after an out of memory error */
1449 for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {
1450 ptr = edit->new_meta[i];
1451 if (ptr) {
1452 if (assoc_array_ptr_is_node(ptr))
1453 kfree(assoc_array_ptr_to_node(ptr));
1454 else
1455 kfree(assoc_array_ptr_to_shortcut(ptr));
1456 }
1457 }
1458 kfree(edit);
1459}
1460
1461/**
1462 * assoc_array_gc - Garbage collect an associative array.
1463 * @array: The array to clean.
1464 * @ops: The operations to use.
1465 * @iterator: A callback function to pass judgement on each object.
1466 * @iterator_data: Private data for the callback function.
1467 *
1468 * Collect garbage from an associative array and pack down the internal tree to
1469 * save memory.
1470 *
1471 * The iterator function is asked to pass judgement upon each object in the
1472 * array. If it returns false, the object is discard and if it returns true,
1473 * the object is kept. If it returns true, it must increment the object's
1474 * usage count (or whatever it needs to do to retain it) before returning.
1475 *
1476 * This function returns 0 if successful or -ENOMEM if out of memory. In the
1477 * latter case, the array is not changed.
1478 *
1479 * The caller should lock against other modifications and must continue to hold
1480 * the lock until assoc_array_apply_edit() has been called.
1481 *
1482 * Accesses to the tree may take place concurrently with this function,
1483 * provided they hold the RCU read lock.
1484 */
1485int assoc_array_gc(struct assoc_array *array,
1486 const struct assoc_array_ops *ops,
1487 bool (*iterator)(void *object, void *iterator_data),
1488 void *iterator_data)
1489{
1490 struct assoc_array_shortcut *shortcut, *new_s;
1491 struct assoc_array_node *node, *new_n;
1492 struct assoc_array_edit *edit;
1493 struct assoc_array_ptr *cursor, *ptr;
1494 struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;
1495 unsigned long nr_leaves_on_tree;
1496 int keylen, slot, nr_free, next_slot, i;
1497
1498 pr_devel("-->%s()\n", __func__);
1499
1500 if (!array->root)
1501 return 0;
1502
1503 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1504 if (!edit)
1505 return -ENOMEM;
1506 edit->array = array;
1507 edit->ops = ops;
1508 edit->ops_for_excised_subtree = ops;
1509 edit->set[0].ptr = &array->root;
1510 edit->excised_subtree = array->root;
1511
1512 new_root = new_parent = NULL;
1513 new_ptr_pp = &new_root;
1514 cursor = array->root;
1515
1516descend:
1517 /* If this point is a shortcut, then we need to duplicate it and
1518 * advance the target cursor.
1519 */
1520 if (assoc_array_ptr_is_shortcut(cursor)) {
1521 shortcut = assoc_array_ptr_to_shortcut(cursor);
1522 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
1523 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
1524 new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
1525 keylen * sizeof(unsigned long), GFP_KERNEL);
1526 if (!new_s)
1527 goto enomem;
1528 pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
1529 memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
1530 keylen * sizeof(unsigned long)));
1531 new_s->back_pointer = new_parent;
1532 new_s->parent_slot = shortcut->parent_slot;
1533 *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
1534 new_ptr_pp = &new_s->next_node;
1535 cursor = shortcut->next_node;
1536 }
1537
1538 /* Duplicate the node at this position */
1539 node = assoc_array_ptr_to_node(cursor);
1540 new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
1541 if (!new_n)
1542 goto enomem;
1543 pr_devel("dup node %p -> %p\n", node, new_n);
1544 new_n->back_pointer = new_parent;
1545 new_n->parent_slot = node->parent_slot;
1546 *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);
1547 new_ptr_pp = NULL;
1548 slot = 0;
1549
1550continue_node:
1551 /* Filter across any leaves and gc any subtrees */
1552 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1553 ptr = node->slots[slot];
1554 if (!ptr)
1555 continue;
1556
1557 if (assoc_array_ptr_is_leaf(ptr)) {
1558 if (iterator(assoc_array_ptr_to_leaf(ptr),
1559 iterator_data))
1560 /* The iterator will have done any reference
1561 * counting on the object for us.
1562 */
1563 new_n->slots[slot] = ptr;
1564 continue;
1565 }
1566
1567 new_ptr_pp = &new_n->slots[slot];
1568 cursor = ptr;
1569 goto descend;
1570 }
1571
1572 pr_devel("-- compress node %p --\n", new_n);
1573
1574 /* Count up the number of empty slots in this node and work out the
1575 * subtree leaf count.
1576 */
1577 new_n->nr_leaves_on_branch = 0;
1578 nr_free = 0;
1579 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1580 ptr = new_n->slots[slot];
1581 if (!ptr)
1582 nr_free++;
1583 else if (assoc_array_ptr_is_leaf(ptr))
1584 new_n->nr_leaves_on_branch++;
1585 }
1586 pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);
1587
1588 /* See what we can fold in */
1589 next_slot = 0;
1590 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1591 struct assoc_array_shortcut *s;
1592 struct assoc_array_node *child;
1593
1594 ptr = new_n->slots[slot];
1595 if (!ptr || assoc_array_ptr_is_leaf(ptr))
1596 continue;
1597
1598 s = NULL;
1599 if (assoc_array_ptr_is_shortcut(ptr)) {
1600 s = assoc_array_ptr_to_shortcut(ptr);
1601 ptr = s->next_node;
1602 }
1603
1604 child = assoc_array_ptr_to_node(ptr);
1605 new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;
1606
1607 if (child->nr_leaves_on_branch <= nr_free + 1) {
1608 /* Fold the child node into this one */
1609 pr_devel("[%d] fold node %lu/%d [nx %d]\n",
1610 slot, child->nr_leaves_on_branch, nr_free + 1,
1611 next_slot);
1612
1613 /* We would already have reaped an intervening shortcut
1614 * on the way back up the tree.
1615 */
1616 BUG_ON(s);
1617
1618 new_n->slots[slot] = NULL;
1619 nr_free++;
1620 if (slot < next_slot)
1621 next_slot = slot;
1622 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
1623 struct assoc_array_ptr *p = child->slots[i];
1624 if (!p)
1625 continue;
1626 BUG_ON(assoc_array_ptr_is_meta(p));
1627 while (new_n->slots[next_slot])
1628 next_slot++;
1629 BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);
1630 new_n->slots[next_slot++] = p;
1631 nr_free--;
1632 }
1633 kfree(child);
1634 } else {
1635 pr_devel("[%d] retain node %lu/%d [nx %d]\n",
1636 slot, child->nr_leaves_on_branch, nr_free + 1,
1637 next_slot);
1638 }
1639 }
1640
1641 pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);
1642
1643 nr_leaves_on_tree = new_n->nr_leaves_on_branch;
1644
1645 /* Excise this node if it is singly occupied by a shortcut */
1646 if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {
1647 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)
1648 if ((ptr = new_n->slots[slot]))
1649 break;
1650
1651 if (assoc_array_ptr_is_meta(ptr) &&
1652 assoc_array_ptr_is_shortcut(ptr)) {
1653 pr_devel("excise node %p with 1 shortcut\n", new_n);
1654 new_s = assoc_array_ptr_to_shortcut(ptr);
1655 new_parent = new_n->back_pointer;
1656 slot = new_n->parent_slot;
1657 kfree(new_n);
1658 if (!new_parent) {
1659 new_s->back_pointer = NULL;
1660 new_s->parent_slot = 0;
1661 new_root = ptr;
1662 goto gc_complete;
1663 }
1664
1665 if (assoc_array_ptr_is_shortcut(new_parent)) {
1666 /* We can discard any preceding shortcut also */
1667 struct assoc_array_shortcut *s =
1668 assoc_array_ptr_to_shortcut(new_parent);
1669
1670 pr_devel("excise preceding shortcut\n");
1671
1672 new_parent = new_s->back_pointer = s->back_pointer;
1673 slot = new_s->parent_slot = s->parent_slot;
1674 kfree(s);
1675 if (!new_parent) {
1676 new_s->back_pointer = NULL;
1677 new_s->parent_slot = 0;
1678 new_root = ptr;
1679 goto gc_complete;
1680 }
1681 }
1682
1683 new_s->back_pointer = new_parent;
1684 new_s->parent_slot = slot;
1685 new_n = assoc_array_ptr_to_node(new_parent);
1686 new_n->slots[slot] = ptr;
1687 goto ascend_old_tree;
1688 }
1689 }
1690
1691 /* Excise any shortcuts we might encounter that point to nodes that
1692 * only contain leaves.
1693 */
1694 ptr = new_n->back_pointer;
1695 if (!ptr)
1696 goto gc_complete;
1697
1698 if (assoc_array_ptr_is_shortcut(ptr)) {
1699 new_s = assoc_array_ptr_to_shortcut(ptr);
1700 new_parent = new_s->back_pointer;
1701 slot = new_s->parent_slot;
1702
1703 if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
1704 struct assoc_array_node *n;
1705
1706 pr_devel("excise shortcut\n");
1707 new_n->back_pointer = new_parent;
1708 new_n->parent_slot = slot;
1709 kfree(new_s);
1710 if (!new_parent) {
1711 new_root = assoc_array_node_to_ptr(new_n);
1712 goto gc_complete;
1713 }
1714
1715 n = assoc_array_ptr_to_node(new_parent);
1716 n->slots[slot] = assoc_array_node_to_ptr(new_n);
1717 }
1718 } else {
1719 new_parent = ptr;
1720 }
1721 new_n = assoc_array_ptr_to_node(new_parent);
1722
1723ascend_old_tree:
1724 ptr = node->back_pointer;
1725 if (assoc_array_ptr_is_shortcut(ptr)) {
1726 shortcut = assoc_array_ptr_to_shortcut(ptr);
1727 slot = shortcut->parent_slot;
1728 cursor = shortcut->back_pointer;
1729 if (!cursor)
1730 goto gc_complete;
1731 } else {
1732 slot = node->parent_slot;
1733 cursor = ptr;
1734 }
1735 BUG_ON(!cursor);
1736 node = assoc_array_ptr_to_node(cursor);
1737 slot++;
1738 goto continue_node;
1739
1740gc_complete:
1741 edit->set[0].to = new_root;
1742 assoc_array_apply_edit(edit);
1743 array->nr_leaves_on_tree = nr_leaves_on_tree;
1744 return 0;
1745
1746enomem:
1747 pr_devel("enomem\n");
1748 assoc_array_destroy_subtree(new_root, edit->ops);
1749 kfree(edit);
1750 return -ENOMEM;
1751}