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David Howells3cb98952013-09-24 10:35:17 +01001/* Generic associative array implementation.
2 *
Alexander Kuleshov48c40c22017-08-23 00:39:13 +06003 * See Documentation/core-api/assoc_array.rst for information.
David Howells3cb98952013-09-24 10:35:17 +01004 *
5 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
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
Pranith Kumar990428b2014-12-30 00:46:21 -050014#include <linux/rcupdate.h>
David Howells3cb98952013-09-24 10:35:17 +010015#include <linux/slab.h>
David Howellsb2a4df22013-09-24 10:35:18 +010016#include <linux/err.h>
David Howells3cb98952013-09-24 10:35:17 +010017#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();
Mark Rutland6aa7de02017-10-23 14:07:29 -070042 cursor = READ_ONCE(shortcut->next_node);
David Howells3cb98952013-09-24 10:35:17 +010043 }
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++) {
Mark Rutland6aa7de02017-10-23 14:07:29 -070058 ptr = READ_ONCE(node->slots[slot]);
David Howells3cb98952013-09-24 10:35:17 +010059 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++) {
Mark Rutland6aa7de02017-10-23 14:07:29 -070092 ptr = READ_ONCE(node->slots[slot]);
David Howells3cb98952013-09-24 10:35:17 +010093 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) */
Mark Rutland6aa7de02017-10-23 14:07:29 -0700101 parent = READ_ONCE(node->back_pointer);
David Howells3cb98952013-09-24 10:35:17 +0100102 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;
Mark Rutland6aa7de02017-10-23 14:07:29 -0700110 parent = READ_ONCE(shortcut->back_pointer);
David Howells3cb98952013-09-24 10:35:17 +0100111 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{
Mark Rutland6aa7de02017-10-23 14:07:29 -0700150 struct assoc_array_ptr *root = READ_ONCE(array->root);
David Howells3cb98952013-09-24 10:35:17 +0100151
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,
Stephen Hemminger30b02c42014-01-23 13:24:09 +0000161};
David Howells3cb98952013-09-24 10:35:17 +0100162
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
Mark Rutland6aa7de02017-10-23 14:07:29 -0700197 cursor = READ_ONCE(array->root);
David Howells3cb98952013-09-24 10:35:17 +0100198 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;
Mark Rutland6aa7de02017-10-23 14:07:29 -0700223 ptr = READ_ONCE(node->slots[slot]);
David Howells3cb98952013-09-24 10:35:17 +0100224
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. */
Mark Rutland6aa7de02017-10-23 14:07:29 -0700297 cursor = READ_ONCE(shortcut->next_node);
David Howells3cb98952013-09-24 10:35:17 +0100298 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++) {
Mark Rutland6aa7de02017-10-23 14:07:29 -0700340 ptr = READ_ONCE(node->slots[slot]);
David Howells3cb98952013-09-24 10:35:17 +0100341 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 }
Jerome Marchand8d4a2ec2016-04-06 14:06:48 +0100527 if (assoc_array_ptr_is_leaf(ptr) &&
528 ops->compare_object(assoc_array_ptr_to_leaf(ptr),
529 index_key)) {
David Howells3cb98952013-09-24 10:35:17 +0100530 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
David Howellsea678992017-10-11 23:32:27 +0100601 /* Otherwise all the old leaves cluster in the same slot, but
602 * the new leaf wants to go into a different slot - so we
603 * create a new node (n0) to hold the new leaf and a pointer to
604 * a new node (n1) holding all the old leaves.
605 *
606 * This can be done by falling through to the node splitting
607 * path.
David Howells3cb98952013-09-24 10:35:17 +0100608 */
David Howellsea678992017-10-11 23:32:27 +0100609 pr_devel("present leaves cluster but not new leaf\n");
David Howells3cb98952013-09-24 10:35:17 +0100610 }
611
612split_node:
613 pr_devel("split node\n");
614
David Howellsea678992017-10-11 23:32:27 +0100615 /* We need to split the current node. The node must contain anything
616 * from a single leaf (in the one leaf case, this leaf will cluster
617 * with the new leaf) and the rest meta-pointers, to all leaves, some
618 * of which may cluster.
619 *
620 * It won't contain the case in which all the current leaves plus the
621 * new leaves want to cluster in the same slot.
David Howells3cb98952013-09-24 10:35:17 +0100622 *
623 * We need to expel at least two leaves out of a set consisting of the
David Howellsea678992017-10-11 23:32:27 +0100624 * leaves in the node and the new leaf. The current meta pointers can
625 * just be copied as they shouldn't cluster with any of the leaves.
David Howells3cb98952013-09-24 10:35:17 +0100626 *
627 * We need a new node (n0) to replace the current one and a new node to
628 * take the expelled nodes (n1).
629 */
630 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
631 new_n0->back_pointer = node->back_pointer;
632 new_n0->parent_slot = node->parent_slot;
633 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
634 new_n1->parent_slot = -1; /* Need to calculate this */
635
636do_split_node:
637 pr_devel("do_split_node\n");
638
639 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
640 new_n1->nr_leaves_on_branch = 0;
641
642 /* Begin by finding two matching leaves. There have to be at least two
643 * that match - even if there are meta pointers - because any leaf that
644 * would match a slot with a meta pointer in it must be somewhere
645 * behind that meta pointer and cannot be here. Further, given N
646 * remaining leaf slots, we now have N+1 leaves to go in them.
647 */
648 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
649 slot = edit->segment_cache[i];
650 if (slot != 0xff)
651 for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)
652 if (edit->segment_cache[j] == slot)
653 goto found_slot_for_multiple_occupancy;
654 }
655found_slot_for_multiple_occupancy:
656 pr_devel("same slot: %x %x [%02x]\n", i, j, slot);
657 BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);
658 BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);
659 BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);
660
661 new_n1->parent_slot = slot;
662
663 /* Metadata pointers cannot change slot */
664 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
665 if (assoc_array_ptr_is_meta(node->slots[i]))
666 new_n0->slots[i] = node->slots[i];
667 else
668 new_n0->slots[i] = NULL;
669 BUG_ON(new_n0->slots[slot] != NULL);
670 new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);
671
672 /* Filter the leaf pointers between the new nodes */
673 free_slot = -1;
674 next_slot = 0;
675 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
676 if (assoc_array_ptr_is_meta(node->slots[i]))
677 continue;
678 if (edit->segment_cache[i] == slot) {
679 new_n1->slots[next_slot++] = node->slots[i];
680 new_n1->nr_leaves_on_branch++;
681 } else {
682 do {
683 free_slot++;
684 } while (new_n0->slots[free_slot] != NULL);
685 new_n0->slots[free_slot] = node->slots[i];
686 }
687 }
688
689 pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);
690
691 if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {
692 do {
693 free_slot++;
694 } while (new_n0->slots[free_slot] != NULL);
695 edit->leaf_p = &new_n0->slots[free_slot];
696 edit->adjust_count_on = new_n0;
697 } else {
698 edit->leaf_p = &new_n1->slots[next_slot++];
699 edit->adjust_count_on = new_n1;
700 }
701
702 BUG_ON(next_slot <= 1);
703
704 edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);
705 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
706 if (edit->segment_cache[i] == 0xff) {
707 ptr = node->slots[i];
708 BUG_ON(assoc_array_ptr_is_leaf(ptr));
709 if (assoc_array_ptr_is_node(ptr)) {
710 side = assoc_array_ptr_to_node(ptr);
711 edit->set_backpointers[i] = &side->back_pointer;
712 } else {
713 shortcut = assoc_array_ptr_to_shortcut(ptr);
714 edit->set_backpointers[i] = &shortcut->back_pointer;
715 }
716 }
717 }
718
719 ptr = node->back_pointer;
720 if (!ptr)
721 edit->set[0].ptr = &edit->array->root;
722 else if (assoc_array_ptr_is_node(ptr))
723 edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];
724 else
725 edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;
726 edit->excised_meta[0] = assoc_array_node_to_ptr(node);
727 pr_devel("<--%s() = ok [split node]\n", __func__);
728 return true;
729
David Howells3cb98952013-09-24 10:35:17 +0100730all_leaves_cluster_together:
731 /* All the leaves, new and old, want to cluster together in this node
732 * in the same slot, so we have to replace this node with a shortcut to
733 * skip over the identical parts of the key and then place a pair of
734 * nodes, one inside the other, at the end of the shortcut and
735 * distribute the keys between them.
736 *
737 * Firstly we need to work out where the leaves start diverging as a
738 * bit position into their keys so that we know how big the shortcut
739 * needs to be.
740 *
741 * We only need to make a single pass of N of the N+1 leaves because if
742 * any keys differ between themselves at bit X then at least one of
743 * them must also differ with the base key at bit X or before.
744 */
745 pr_devel("all leaves cluster together\n");
746 diff = INT_MAX;
747 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
David Howells23fd78d2013-12-02 11:24:18 +0000748 int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]),
749 index_key);
David Howells3cb98952013-09-24 10:35:17 +0100750 if (x < diff) {
751 BUG_ON(x < 0);
752 diff = x;
753 }
754 }
755 BUG_ON(diff == INT_MAX);
756 BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);
757
758 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
759 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
760
761 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
762 keylen * sizeof(unsigned long), GFP_KERNEL);
763 if (!new_s0)
764 return false;
765 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
766
767 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
768 new_s0->back_pointer = node->back_pointer;
769 new_s0->parent_slot = node->parent_slot;
770 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
771 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
772 new_n0->parent_slot = 0;
773 new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
774 new_n1->parent_slot = -1; /* Need to calculate this */
775
776 new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;
777 pr_devel("skip_to_level = %d [diff %d]\n", level, diff);
778 BUG_ON(level <= 0);
779
780 for (i = 0; i < keylen; i++)
781 new_s0->index_key[i] =
782 ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
783
784 blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
785 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
786 new_s0->index_key[keylen - 1] &= ~blank;
787
788 /* This now reduces to a node splitting exercise for which we'll need
789 * to regenerate the disparity table.
790 */
791 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
792 ptr = node->slots[i];
793 base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),
794 level);
795 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
796 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
797 }
798
799 base_seg = ops->get_key_chunk(index_key, level);
800 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
801 edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;
802 goto do_split_node;
803}
804
805/*
806 * Handle insertion into the middle of a shortcut.
807 */
808static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
809 const struct assoc_array_ops *ops,
810 struct assoc_array_walk_result *result)
811{
812 struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;
813 struct assoc_array_node *node, *new_n0, *side;
814 unsigned long sc_segments, dissimilarity, blank;
815 size_t keylen;
816 int level, sc_level, diff;
817 int sc_slot;
818
819 shortcut = result->wrong_shortcut.shortcut;
820 level = result->wrong_shortcut.level;
821 sc_level = result->wrong_shortcut.sc_level;
822 sc_segments = result->wrong_shortcut.sc_segments;
823 dissimilarity = result->wrong_shortcut.dissimilarity;
824
825 pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",
826 __func__, level, dissimilarity, sc_level);
827
828 /* We need to split a shortcut and insert a node between the two
829 * pieces. Zero-length pieces will be dispensed with entirely.
830 *
831 * First of all, we need to find out in which level the first
832 * difference was.
833 */
834 diff = __ffs(dissimilarity);
835 diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;
836 diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;
837 pr_devel("diff=%d\n", diff);
838
839 if (!shortcut->back_pointer) {
840 edit->set[0].ptr = &edit->array->root;
841 } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {
842 node = assoc_array_ptr_to_node(shortcut->back_pointer);
843 edit->set[0].ptr = &node->slots[shortcut->parent_slot];
844 } else {
845 BUG();
846 }
847
848 edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);
849
850 /* Create a new node now since we're going to need it anyway */
851 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
852 if (!new_n0)
853 return false;
854 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
855 edit->adjust_count_on = new_n0;
856
857 /* Insert a new shortcut before the new node if this segment isn't of
858 * zero length - otherwise we just connect the new node directly to the
859 * parent.
860 */
861 level += ASSOC_ARRAY_LEVEL_STEP;
862 if (diff > level) {
863 pr_devel("pre-shortcut %d...%d\n", level, diff);
864 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
865 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
866
867 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
868 keylen * sizeof(unsigned long), GFP_KERNEL);
869 if (!new_s0)
870 return false;
871 edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
872 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
873 new_s0->back_pointer = shortcut->back_pointer;
874 new_s0->parent_slot = shortcut->parent_slot;
875 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
876 new_s0->skip_to_level = diff;
877
878 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
879 new_n0->parent_slot = 0;
880
881 memcpy(new_s0->index_key, shortcut->index_key,
882 keylen * sizeof(unsigned long));
883
884 blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
885 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
886 new_s0->index_key[keylen - 1] &= ~blank;
887 } else {
888 pr_devel("no pre-shortcut\n");
889 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
890 new_n0->back_pointer = shortcut->back_pointer;
891 new_n0->parent_slot = shortcut->parent_slot;
892 }
893
894 side = assoc_array_ptr_to_node(shortcut->next_node);
895 new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;
896
897 /* We need to know which slot in the new node is going to take a
898 * metadata pointer.
899 */
900 sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
901 sc_slot &= ASSOC_ARRAY_FAN_MASK;
902
903 pr_devel("new slot %lx >> %d -> %d\n",
904 sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);
905
906 /* Determine whether we need to follow the new node with a replacement
907 * for the current shortcut. We could in theory reuse the current
908 * shortcut if its parent slot number doesn't change - but that's a
909 * 1-in-16 chance so not worth expending the code upon.
910 */
911 level = diff + ASSOC_ARRAY_LEVEL_STEP;
912 if (level < shortcut->skip_to_level) {
913 pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);
914 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
915 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
916
917 new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
918 keylen * sizeof(unsigned long), GFP_KERNEL);
919 if (!new_s1)
920 return false;
921 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
922
923 new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);
924 new_s1->parent_slot = sc_slot;
925 new_s1->next_node = shortcut->next_node;
926 new_s1->skip_to_level = shortcut->skip_to_level;
927
928 new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
929
930 memcpy(new_s1->index_key, shortcut->index_key,
931 keylen * sizeof(unsigned long));
932
933 edit->set[1].ptr = &side->back_pointer;
934 edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
935 } else {
936 pr_devel("no post-shortcut\n");
937
938 /* We don't have to replace the pointed-to node as long as we
939 * use memory barriers to make sure the parent slot number is
940 * changed before the back pointer (the parent slot number is
941 * irrelevant to the old parent shortcut).
942 */
943 new_n0->slots[sc_slot] = shortcut->next_node;
944 edit->set_parent_slot[0].p = &side->parent_slot;
945 edit->set_parent_slot[0].to = sc_slot;
946 edit->set[1].ptr = &side->back_pointer;
947 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
948 }
949
950 /* Install the new leaf in a spare slot in the new node. */
951 if (sc_slot == 0)
952 edit->leaf_p = &new_n0->slots[1];
953 else
954 edit->leaf_p = &new_n0->slots[0];
955
956 pr_devel("<--%s() = ok [split shortcut]\n", __func__);
957 return edit;
958}
959
960/**
961 * assoc_array_insert - Script insertion of an object into an associative array
962 * @array: The array to insert into.
963 * @ops: The operations to use.
964 * @index_key: The key to insert at.
965 * @object: The object to insert.
966 *
967 * Precalculate and preallocate a script for the insertion or replacement of an
968 * object in an associative array. This results in an edit script that can
969 * either be applied or cancelled.
970 *
971 * The function returns a pointer to an edit script or -ENOMEM.
972 *
973 * The caller should lock against other modifications and must continue to hold
974 * the lock until assoc_array_apply_edit() has been called.
975 *
976 * Accesses to the tree may take place concurrently with this function,
977 * provided they hold the RCU read lock.
978 */
979struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
980 const struct assoc_array_ops *ops,
981 const void *index_key,
982 void *object)
983{
984 struct assoc_array_walk_result result;
985 struct assoc_array_edit *edit;
986
987 pr_devel("-->%s()\n", __func__);
988
989 /* The leaf pointer we're given must not have the bottom bit set as we
990 * use those for type-marking the pointer. NULL pointers are also not
991 * allowed as they indicate an empty slot but we have to allow them
992 * here as they can be updated later.
993 */
994 BUG_ON(assoc_array_ptr_is_meta(object));
995
996 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
997 if (!edit)
998 return ERR_PTR(-ENOMEM);
999 edit->array = array;
1000 edit->ops = ops;
1001 edit->leaf = assoc_array_leaf_to_ptr(object);
1002 edit->adjust_count_by = 1;
1003
1004 switch (assoc_array_walk(array, ops, index_key, &result)) {
1005 case assoc_array_walk_tree_empty:
1006 /* Allocate a root node if there isn't one yet */
1007 if (!assoc_array_insert_in_empty_tree(edit))
1008 goto enomem;
1009 return edit;
1010
1011 case assoc_array_walk_found_terminal_node:
1012 /* We found a node that doesn't have a node/shortcut pointer in
1013 * the slot corresponding to the index key that we have to
1014 * follow.
1015 */
1016 if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,
1017 &result))
1018 goto enomem;
1019 return edit;
1020
1021 case assoc_array_walk_found_wrong_shortcut:
1022 /* We found a shortcut that didn't match our key in a slot we
1023 * needed to follow.
1024 */
1025 if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
1026 goto enomem;
1027 return edit;
1028 }
1029
1030enomem:
1031 /* Clean up after an out of memory error */
1032 pr_devel("enomem\n");
1033 assoc_array_cancel_edit(edit);
1034 return ERR_PTR(-ENOMEM);
1035}
1036
1037/**
1038 * assoc_array_insert_set_object - Set the new object pointer in an edit script
1039 * @edit: The edit script to modify.
1040 * @object: The object pointer to set.
1041 *
1042 * Change the object to be inserted in an edit script. The object pointed to
1043 * by the old object is not freed. This must be done prior to applying the
1044 * script.
1045 */
1046void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)
1047{
1048 BUG_ON(!object);
1049 edit->leaf = assoc_array_leaf_to_ptr(object);
1050}
1051
1052struct assoc_array_delete_collapse_context {
1053 struct assoc_array_node *node;
1054 const void *skip_leaf;
1055 int slot;
1056};
1057
1058/*
1059 * Subtree collapse to node iterator.
1060 */
1061static int assoc_array_delete_collapse_iterator(const void *leaf,
1062 void *iterator_data)
1063{
1064 struct assoc_array_delete_collapse_context *collapse = iterator_data;
1065
1066 if (leaf == collapse->skip_leaf)
1067 return 0;
1068
1069 BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);
1070
1071 collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);
1072 return 0;
1073}
1074
1075/**
1076 * assoc_array_delete - Script deletion of an object from an associative array
1077 * @array: The array to search.
1078 * @ops: The operations to use.
1079 * @index_key: The key to the object.
1080 *
1081 * Precalculate and preallocate a script for the deletion of an object from an
1082 * associative array. This results in an edit script that can either be
1083 * applied or cancelled.
1084 *
1085 * The function returns a pointer to an edit script if the object was found,
1086 * NULL if the object was not found or -ENOMEM.
1087 *
1088 * The caller should lock against other modifications and must continue to hold
1089 * the lock until assoc_array_apply_edit() has been called.
1090 *
1091 * Accesses to the tree may take place concurrently with this function,
1092 * provided they hold the RCU read lock.
1093 */
1094struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
1095 const struct assoc_array_ops *ops,
1096 const void *index_key)
1097{
1098 struct assoc_array_delete_collapse_context collapse;
1099 struct assoc_array_walk_result result;
1100 struct assoc_array_node *node, *new_n0;
1101 struct assoc_array_edit *edit;
1102 struct assoc_array_ptr *ptr;
1103 bool has_meta;
1104 int slot, i;
1105
1106 pr_devel("-->%s()\n", __func__);
1107
1108 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1109 if (!edit)
1110 return ERR_PTR(-ENOMEM);
1111 edit->array = array;
1112 edit->ops = ops;
1113 edit->adjust_count_by = -1;
1114
1115 switch (assoc_array_walk(array, ops, index_key, &result)) {
1116 case assoc_array_walk_found_terminal_node:
1117 /* We found a node that should contain the leaf we've been
1118 * asked to remove - *if* it's in the tree.
1119 */
1120 pr_devel("terminal_node\n");
1121 node = result.terminal_node.node;
1122
1123 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1124 ptr = node->slots[slot];
1125 if (ptr &&
1126 assoc_array_ptr_is_leaf(ptr) &&
1127 ops->compare_object(assoc_array_ptr_to_leaf(ptr),
1128 index_key))
1129 goto found_leaf;
1130 }
1131 case assoc_array_walk_tree_empty:
1132 case assoc_array_walk_found_wrong_shortcut:
1133 default:
1134 assoc_array_cancel_edit(edit);
1135 pr_devel("not found\n");
1136 return NULL;
1137 }
1138
1139found_leaf:
1140 BUG_ON(array->nr_leaves_on_tree <= 0);
1141
1142 /* In the simplest form of deletion we just clear the slot and release
1143 * the leaf after a suitable interval.
1144 */
1145 edit->dead_leaf = node->slots[slot];
1146 edit->set[0].ptr = &node->slots[slot];
1147 edit->set[0].to = NULL;
1148 edit->adjust_count_on = node;
1149
1150 /* If that concludes erasure of the last leaf, then delete the entire
1151 * internal array.
1152 */
1153 if (array->nr_leaves_on_tree == 1) {
1154 edit->set[1].ptr = &array->root;
1155 edit->set[1].to = NULL;
1156 edit->adjust_count_on = NULL;
1157 edit->excised_subtree = array->root;
1158 pr_devel("all gone\n");
1159 return edit;
1160 }
1161
1162 /* However, we'd also like to clear up some metadata blocks if we
1163 * possibly can.
1164 *
1165 * We go for a simple algorithm of: if this node has FAN_OUT or fewer
1166 * leaves in it, then attempt to collapse it - and attempt to
1167 * recursively collapse up the tree.
1168 *
1169 * We could also try and collapse in partially filled subtrees to take
1170 * up space in this node.
1171 */
1172 if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
1173 struct assoc_array_node *parent, *grandparent;
1174 struct assoc_array_ptr *ptr;
1175
1176 /* First of all, we need to know if this node has metadata so
1177 * that we don't try collapsing if all the leaves are already
1178 * here.
1179 */
1180 has_meta = false;
1181 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
1182 ptr = node->slots[i];
1183 if (assoc_array_ptr_is_meta(ptr)) {
1184 has_meta = true;
1185 break;
1186 }
1187 }
1188
1189 pr_devel("leaves: %ld [m=%d]\n",
1190 node->nr_leaves_on_branch - 1, has_meta);
1191
1192 /* Look further up the tree to see if we can collapse this node
1193 * into a more proximal node too.
1194 */
1195 parent = node;
1196 collapse_up:
1197 pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);
1198
1199 ptr = parent->back_pointer;
1200 if (!ptr)
1201 goto do_collapse;
1202 if (assoc_array_ptr_is_shortcut(ptr)) {
1203 struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);
1204 ptr = s->back_pointer;
1205 if (!ptr)
1206 goto do_collapse;
1207 }
1208
1209 grandparent = assoc_array_ptr_to_node(ptr);
1210 if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
1211 parent = grandparent;
1212 goto collapse_up;
1213 }
1214
1215 do_collapse:
1216 /* There's no point collapsing if the original node has no meta
1217 * pointers to discard and if we didn't merge into one of that
1218 * node's ancestry.
1219 */
1220 if (has_meta || parent != node) {
1221 node = parent;
1222
1223 /* Create a new node to collapse into */
1224 new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
1225 if (!new_n0)
1226 goto enomem;
1227 edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
1228
1229 new_n0->back_pointer = node->back_pointer;
1230 new_n0->parent_slot = node->parent_slot;
1231 new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
1232 edit->adjust_count_on = new_n0;
1233
1234 collapse.node = new_n0;
1235 collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);
1236 collapse.slot = 0;
1237 assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),
1238 node->back_pointer,
1239 assoc_array_delete_collapse_iterator,
1240 &collapse);
1241 pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);
1242 BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);
1243
1244 if (!node->back_pointer) {
1245 edit->set[1].ptr = &array->root;
1246 } else if (assoc_array_ptr_is_leaf(node->back_pointer)) {
1247 BUG();
1248 } else if (assoc_array_ptr_is_node(node->back_pointer)) {
1249 struct assoc_array_node *p =
1250 assoc_array_ptr_to_node(node->back_pointer);
1251 edit->set[1].ptr = &p->slots[node->parent_slot];
1252 } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {
1253 struct assoc_array_shortcut *s =
1254 assoc_array_ptr_to_shortcut(node->back_pointer);
1255 edit->set[1].ptr = &s->next_node;
1256 }
1257 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
1258 edit->excised_subtree = assoc_array_node_to_ptr(node);
1259 }
1260 }
1261
1262 return edit;
1263
1264enomem:
1265 /* Clean up after an out of memory error */
1266 pr_devel("enomem\n");
1267 assoc_array_cancel_edit(edit);
1268 return ERR_PTR(-ENOMEM);
1269}
1270
1271/**
1272 * assoc_array_clear - Script deletion of all objects from an associative array
1273 * @array: The array to clear.
1274 * @ops: The operations to use.
1275 *
1276 * Precalculate and preallocate a script for the deletion of all the objects
1277 * from an associative array. This results in an edit script that can either
1278 * be applied or cancelled.
1279 *
1280 * The function returns a pointer to an edit script if there are objects to be
1281 * deleted, NULL if there are no objects in the array or -ENOMEM.
1282 *
1283 * The caller should lock against other modifications and must continue to hold
1284 * the lock until assoc_array_apply_edit() has been called.
1285 *
1286 * Accesses to the tree may take place concurrently with this function,
1287 * provided they hold the RCU read lock.
1288 */
1289struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,
1290 const struct assoc_array_ops *ops)
1291{
1292 struct assoc_array_edit *edit;
1293
1294 pr_devel("-->%s()\n", __func__);
1295
1296 if (!array->root)
1297 return NULL;
1298
1299 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1300 if (!edit)
1301 return ERR_PTR(-ENOMEM);
1302 edit->array = array;
1303 edit->ops = ops;
1304 edit->set[1].ptr = &array->root;
1305 edit->set[1].to = NULL;
1306 edit->excised_subtree = array->root;
1307 edit->ops_for_excised_subtree = ops;
1308 pr_devel("all gone\n");
1309 return edit;
1310}
1311
1312/*
1313 * Handle the deferred destruction after an applied edit.
1314 */
1315static void assoc_array_rcu_cleanup(struct rcu_head *head)
1316{
1317 struct assoc_array_edit *edit =
1318 container_of(head, struct assoc_array_edit, rcu);
1319 int i;
1320
1321 pr_devel("-->%s()\n", __func__);
1322
1323 if (edit->dead_leaf)
1324 edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));
1325 for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)
1326 if (edit->excised_meta[i])
1327 kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));
1328
1329 if (edit->excised_subtree) {
1330 BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));
1331 if (assoc_array_ptr_is_node(edit->excised_subtree)) {
1332 struct assoc_array_node *n =
1333 assoc_array_ptr_to_node(edit->excised_subtree);
1334 n->back_pointer = NULL;
1335 } else {
1336 struct assoc_array_shortcut *s =
1337 assoc_array_ptr_to_shortcut(edit->excised_subtree);
1338 s->back_pointer = NULL;
1339 }
1340 assoc_array_destroy_subtree(edit->excised_subtree,
1341 edit->ops_for_excised_subtree);
1342 }
1343
1344 kfree(edit);
1345}
1346
1347/**
1348 * assoc_array_apply_edit - Apply an edit script to an associative array
1349 * @edit: The script to apply.
1350 *
1351 * Apply an edit script to an associative array to effect an insertion,
1352 * deletion or clearance. As the edit script includes preallocated memory,
1353 * this is guaranteed not to fail.
1354 *
1355 * The edit script, dead objects and dead metadata will be scheduled for
1356 * destruction after an RCU grace period to permit those doing read-only
1357 * accesses on the array to continue to do so under the RCU read lock whilst
1358 * the edit is taking place.
1359 */
1360void assoc_array_apply_edit(struct assoc_array_edit *edit)
1361{
1362 struct assoc_array_shortcut *shortcut;
1363 struct assoc_array_node *node;
1364 struct assoc_array_ptr *ptr;
1365 int i;
1366
1367 pr_devel("-->%s()\n", __func__);
1368
1369 smp_wmb();
1370 if (edit->leaf_p)
1371 *edit->leaf_p = edit->leaf;
1372
1373 smp_wmb();
1374 for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)
1375 if (edit->set_parent_slot[i].p)
1376 *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;
1377
1378 smp_wmb();
1379 for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)
1380 if (edit->set_backpointers[i])
1381 *edit->set_backpointers[i] = edit->set_backpointers_to;
1382
1383 smp_wmb();
1384 for (i = 0; i < ARRAY_SIZE(edit->set); i++)
1385 if (edit->set[i].ptr)
1386 *edit->set[i].ptr = edit->set[i].to;
1387
1388 if (edit->array->root == NULL) {
1389 edit->array->nr_leaves_on_tree = 0;
1390 } else if (edit->adjust_count_on) {
1391 node = edit->adjust_count_on;
1392 for (;;) {
1393 node->nr_leaves_on_branch += edit->adjust_count_by;
1394
1395 ptr = node->back_pointer;
1396 if (!ptr)
1397 break;
1398 if (assoc_array_ptr_is_shortcut(ptr)) {
1399 shortcut = assoc_array_ptr_to_shortcut(ptr);
1400 ptr = shortcut->back_pointer;
1401 if (!ptr)
1402 break;
1403 }
1404 BUG_ON(!assoc_array_ptr_is_node(ptr));
1405 node = assoc_array_ptr_to_node(ptr);
1406 }
1407
1408 edit->array->nr_leaves_on_tree += edit->adjust_count_by;
1409 }
1410
1411 call_rcu(&edit->rcu, assoc_array_rcu_cleanup);
1412}
1413
1414/**
1415 * assoc_array_cancel_edit - Discard an edit script.
1416 * @edit: The script to discard.
1417 *
1418 * Free an edit script and all the preallocated data it holds without making
1419 * any changes to the associative array it was intended for.
1420 *
1421 * NOTE! In the case of an insertion script, this does _not_ release the leaf
1422 * that was to be inserted. That is left to the caller.
1423 */
1424void assoc_array_cancel_edit(struct assoc_array_edit *edit)
1425{
1426 struct assoc_array_ptr *ptr;
1427 int i;
1428
1429 pr_devel("-->%s()\n", __func__);
1430
1431 /* Clean up after an out of memory error */
1432 for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {
1433 ptr = edit->new_meta[i];
1434 if (ptr) {
1435 if (assoc_array_ptr_is_node(ptr))
1436 kfree(assoc_array_ptr_to_node(ptr));
1437 else
1438 kfree(assoc_array_ptr_to_shortcut(ptr));
1439 }
1440 }
1441 kfree(edit);
1442}
1443
1444/**
1445 * assoc_array_gc - Garbage collect an associative array.
1446 * @array: The array to clean.
1447 * @ops: The operations to use.
1448 * @iterator: A callback function to pass judgement on each object.
1449 * @iterator_data: Private data for the callback function.
1450 *
1451 * Collect garbage from an associative array and pack down the internal tree to
1452 * save memory.
1453 *
1454 * The iterator function is asked to pass judgement upon each object in the
1455 * array. If it returns false, the object is discard and if it returns true,
1456 * the object is kept. If it returns true, it must increment the object's
1457 * usage count (or whatever it needs to do to retain it) before returning.
1458 *
1459 * This function returns 0 if successful or -ENOMEM if out of memory. In the
1460 * latter case, the array is not changed.
1461 *
1462 * The caller should lock against other modifications and must continue to hold
1463 * the lock until assoc_array_apply_edit() has been called.
1464 *
1465 * Accesses to the tree may take place concurrently with this function,
1466 * provided they hold the RCU read lock.
1467 */
1468int assoc_array_gc(struct assoc_array *array,
1469 const struct assoc_array_ops *ops,
1470 bool (*iterator)(void *object, void *iterator_data),
1471 void *iterator_data)
1472{
1473 struct assoc_array_shortcut *shortcut, *new_s;
1474 struct assoc_array_node *node, *new_n;
1475 struct assoc_array_edit *edit;
1476 struct assoc_array_ptr *cursor, *ptr;
1477 struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;
1478 unsigned long nr_leaves_on_tree;
1479 int keylen, slot, nr_free, next_slot, i;
1480
1481 pr_devel("-->%s()\n", __func__);
1482
1483 if (!array->root)
1484 return 0;
1485
1486 edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
1487 if (!edit)
1488 return -ENOMEM;
1489 edit->array = array;
1490 edit->ops = ops;
1491 edit->ops_for_excised_subtree = ops;
1492 edit->set[0].ptr = &array->root;
1493 edit->excised_subtree = array->root;
1494
1495 new_root = new_parent = NULL;
1496 new_ptr_pp = &new_root;
1497 cursor = array->root;
1498
1499descend:
1500 /* If this point is a shortcut, then we need to duplicate it and
1501 * advance the target cursor.
1502 */
1503 if (assoc_array_ptr_is_shortcut(cursor)) {
1504 shortcut = assoc_array_ptr_to_shortcut(cursor);
1505 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
1506 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
1507 new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
1508 keylen * sizeof(unsigned long), GFP_KERNEL);
1509 if (!new_s)
1510 goto enomem;
1511 pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
1512 memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
1513 keylen * sizeof(unsigned long)));
1514 new_s->back_pointer = new_parent;
1515 new_s->parent_slot = shortcut->parent_slot;
1516 *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
1517 new_ptr_pp = &new_s->next_node;
1518 cursor = shortcut->next_node;
1519 }
1520
1521 /* Duplicate the node at this position */
1522 node = assoc_array_ptr_to_node(cursor);
1523 new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
1524 if (!new_n)
1525 goto enomem;
1526 pr_devel("dup node %p -> %p\n", node, new_n);
1527 new_n->back_pointer = new_parent;
1528 new_n->parent_slot = node->parent_slot;
1529 *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);
1530 new_ptr_pp = NULL;
1531 slot = 0;
1532
1533continue_node:
1534 /* Filter across any leaves and gc any subtrees */
1535 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1536 ptr = node->slots[slot];
1537 if (!ptr)
1538 continue;
1539
1540 if (assoc_array_ptr_is_leaf(ptr)) {
1541 if (iterator(assoc_array_ptr_to_leaf(ptr),
1542 iterator_data))
1543 /* The iterator will have done any reference
1544 * counting on the object for us.
1545 */
1546 new_n->slots[slot] = ptr;
1547 continue;
1548 }
1549
1550 new_ptr_pp = &new_n->slots[slot];
1551 cursor = ptr;
1552 goto descend;
1553 }
1554
1555 pr_devel("-- compress node %p --\n", new_n);
1556
1557 /* Count up the number of empty slots in this node and work out the
1558 * subtree leaf count.
1559 */
1560 new_n->nr_leaves_on_branch = 0;
1561 nr_free = 0;
1562 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1563 ptr = new_n->slots[slot];
1564 if (!ptr)
1565 nr_free++;
1566 else if (assoc_array_ptr_is_leaf(ptr))
1567 new_n->nr_leaves_on_branch++;
1568 }
1569 pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);
1570
1571 /* See what we can fold in */
1572 next_slot = 0;
1573 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
1574 struct assoc_array_shortcut *s;
1575 struct assoc_array_node *child;
1576
1577 ptr = new_n->slots[slot];
1578 if (!ptr || assoc_array_ptr_is_leaf(ptr))
1579 continue;
1580
1581 s = NULL;
1582 if (assoc_array_ptr_is_shortcut(ptr)) {
1583 s = assoc_array_ptr_to_shortcut(ptr);
1584 ptr = s->next_node;
1585 }
1586
1587 child = assoc_array_ptr_to_node(ptr);
1588 new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;
1589
1590 if (child->nr_leaves_on_branch <= nr_free + 1) {
1591 /* Fold the child node into this one */
1592 pr_devel("[%d] fold node %lu/%d [nx %d]\n",
1593 slot, child->nr_leaves_on_branch, nr_free + 1,
1594 next_slot);
1595
1596 /* We would already have reaped an intervening shortcut
1597 * on the way back up the tree.
1598 */
1599 BUG_ON(s);
1600
1601 new_n->slots[slot] = NULL;
1602 nr_free++;
1603 if (slot < next_slot)
1604 next_slot = slot;
1605 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
1606 struct assoc_array_ptr *p = child->slots[i];
1607 if (!p)
1608 continue;
1609 BUG_ON(assoc_array_ptr_is_meta(p));
1610 while (new_n->slots[next_slot])
1611 next_slot++;
1612 BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);
1613 new_n->slots[next_slot++] = p;
1614 nr_free--;
1615 }
1616 kfree(child);
1617 } else {
1618 pr_devel("[%d] retain node %lu/%d [nx %d]\n",
1619 slot, child->nr_leaves_on_branch, nr_free + 1,
1620 next_slot);
1621 }
1622 }
1623
1624 pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);
1625
1626 nr_leaves_on_tree = new_n->nr_leaves_on_branch;
1627
1628 /* Excise this node if it is singly occupied by a shortcut */
1629 if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {
1630 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)
1631 if ((ptr = new_n->slots[slot]))
1632 break;
1633
1634 if (assoc_array_ptr_is_meta(ptr) &&
1635 assoc_array_ptr_is_shortcut(ptr)) {
1636 pr_devel("excise node %p with 1 shortcut\n", new_n);
1637 new_s = assoc_array_ptr_to_shortcut(ptr);
1638 new_parent = new_n->back_pointer;
1639 slot = new_n->parent_slot;
1640 kfree(new_n);
1641 if (!new_parent) {
1642 new_s->back_pointer = NULL;
1643 new_s->parent_slot = 0;
1644 new_root = ptr;
1645 goto gc_complete;
1646 }
1647
1648 if (assoc_array_ptr_is_shortcut(new_parent)) {
1649 /* We can discard any preceding shortcut also */
1650 struct assoc_array_shortcut *s =
1651 assoc_array_ptr_to_shortcut(new_parent);
1652
1653 pr_devel("excise preceding shortcut\n");
1654
1655 new_parent = new_s->back_pointer = s->back_pointer;
1656 slot = new_s->parent_slot = s->parent_slot;
1657 kfree(s);
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
1666 new_s->back_pointer = new_parent;
1667 new_s->parent_slot = slot;
1668 new_n = assoc_array_ptr_to_node(new_parent);
1669 new_n->slots[slot] = ptr;
1670 goto ascend_old_tree;
1671 }
1672 }
1673
1674 /* Excise any shortcuts we might encounter that point to nodes that
1675 * only contain leaves.
1676 */
1677 ptr = new_n->back_pointer;
1678 if (!ptr)
1679 goto gc_complete;
1680
1681 if (assoc_array_ptr_is_shortcut(ptr)) {
1682 new_s = assoc_array_ptr_to_shortcut(ptr);
1683 new_parent = new_s->back_pointer;
1684 slot = new_s->parent_slot;
1685
1686 if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
1687 struct assoc_array_node *n;
1688
1689 pr_devel("excise shortcut\n");
1690 new_n->back_pointer = new_parent;
1691 new_n->parent_slot = slot;
1692 kfree(new_s);
1693 if (!new_parent) {
1694 new_root = assoc_array_node_to_ptr(new_n);
1695 goto gc_complete;
1696 }
1697
1698 n = assoc_array_ptr_to_node(new_parent);
1699 n->slots[slot] = assoc_array_node_to_ptr(new_n);
1700 }
1701 } else {
1702 new_parent = ptr;
1703 }
1704 new_n = assoc_array_ptr_to_node(new_parent);
1705
1706ascend_old_tree:
1707 ptr = node->back_pointer;
1708 if (assoc_array_ptr_is_shortcut(ptr)) {
1709 shortcut = assoc_array_ptr_to_shortcut(ptr);
1710 slot = shortcut->parent_slot;
1711 cursor = shortcut->back_pointer;
David Howells95389b02014-09-10 22:22:00 +01001712 if (!cursor)
1713 goto gc_complete;
David Howells3cb98952013-09-24 10:35:17 +01001714 } else {
1715 slot = node->parent_slot;
1716 cursor = ptr;
1717 }
David Howells95389b02014-09-10 22:22:00 +01001718 BUG_ON(!cursor);
David Howells3cb98952013-09-24 10:35:17 +01001719 node = assoc_array_ptr_to_node(cursor);
1720 slot++;
1721 goto continue_node;
1722
1723gc_complete:
1724 edit->set[0].to = new_root;
1725 assoc_array_apply_edit(edit);
David Howells27419602014-09-02 13:52:20 +01001726 array->nr_leaves_on_tree = nr_leaves_on_tree;
David Howells3cb98952013-09-24 10:35:17 +01001727 return 0;
1728
1729enomem:
1730 pr_devel("enomem\n");
1731 assoc_array_destroy_subtree(new_root, edit->ops);
1732 kfree(edit);
1733 return -ENOMEM;
1734}