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3cb98950 DH |
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 (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 | |
14 | #include <linux/slab.h> | |
15 | #include <linux/assoc_array_priv.h> | |
16 | ||
17 | /* | |
18 | * Iterate over an associative array. The caller must hold the RCU read lock | |
19 | * or better. | |
20 | */ | |
21 | static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root, | |
22 | const struct assoc_array_ptr *stop, | |
23 | int (*iterator)(const void *leaf, | |
24 | void *iterator_data), | |
25 | void *iterator_data) | |
26 | { | |
27 | const struct assoc_array_shortcut *shortcut; | |
28 | const struct assoc_array_node *node; | |
29 | const struct assoc_array_ptr *cursor, *ptr, *parent; | |
30 | unsigned long has_meta; | |
31 | int slot, ret; | |
32 | ||
33 | cursor = root; | |
34 | ||
35 | begin_node: | |
36 | if (assoc_array_ptr_is_shortcut(cursor)) { | |
37 | /* Descend through a shortcut */ | |
38 | shortcut = assoc_array_ptr_to_shortcut(cursor); | |
39 | smp_read_barrier_depends(); | |
40 | cursor = ACCESS_ONCE(shortcut->next_node); | |
41 | } | |
42 | ||
43 | node = assoc_array_ptr_to_node(cursor); | |
44 | smp_read_barrier_depends(); | |
45 | slot = 0; | |
46 | ||
47 | /* We perform two passes of each node. | |
48 | * | |
49 | * The first pass does all the leaves in this node. This means we | |
50 | * don't miss any leaves if the node is split up by insertion whilst | |
51 | * we're iterating over the branches rooted here (we may, however, see | |
52 | * some leaves twice). | |
53 | */ | |
54 | has_meta = 0; | |
55 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
56 | ptr = ACCESS_ONCE(node->slots[slot]); | |
57 | has_meta |= (unsigned long)ptr; | |
58 | if (ptr && assoc_array_ptr_is_leaf(ptr)) { | |
59 | /* We need a barrier between the read of the pointer | |
60 | * and dereferencing the pointer - but only if we are | |
61 | * actually going to dereference it. | |
62 | */ | |
63 | smp_read_barrier_depends(); | |
64 | ||
65 | /* Invoke the callback */ | |
66 | ret = iterator(assoc_array_ptr_to_leaf(ptr), | |
67 | iterator_data); | |
68 | if (ret) | |
69 | return ret; | |
70 | } | |
71 | } | |
72 | ||
73 | /* The second pass attends to all the metadata pointers. If we follow | |
74 | * one of these we may find that we don't come back here, but rather go | |
75 | * back to a replacement node with the leaves in a different layout. | |
76 | * | |
77 | * We are guaranteed to make progress, however, as the slot number for | |
78 | * a particular portion of the key space cannot change - and we | |
79 | * continue at the back pointer + 1. | |
80 | */ | |
81 | if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE)) | |
82 | goto finished_node; | |
83 | slot = 0; | |
84 | ||
85 | continue_node: | |
86 | node = assoc_array_ptr_to_node(cursor); | |
87 | smp_read_barrier_depends(); | |
88 | ||
89 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
90 | ptr = ACCESS_ONCE(node->slots[slot]); | |
91 | if (assoc_array_ptr_is_meta(ptr)) { | |
92 | cursor = ptr; | |
93 | goto begin_node; | |
94 | } | |
95 | } | |
96 | ||
97 | finished_node: | |
98 | /* Move up to the parent (may need to skip back over a shortcut) */ | |
99 | parent = ACCESS_ONCE(node->back_pointer); | |
100 | slot = node->parent_slot; | |
101 | if (parent == stop) | |
102 | return 0; | |
103 | ||
104 | if (assoc_array_ptr_is_shortcut(parent)) { | |
105 | shortcut = assoc_array_ptr_to_shortcut(parent); | |
106 | smp_read_barrier_depends(); | |
107 | cursor = parent; | |
108 | parent = ACCESS_ONCE(shortcut->back_pointer); | |
109 | slot = shortcut->parent_slot; | |
110 | if (parent == stop) | |
111 | return 0; | |
112 | } | |
113 | ||
114 | /* Ascend to next slot in parent node */ | |
115 | cursor = parent; | |
116 | slot++; | |
117 | goto continue_node; | |
118 | } | |
119 | ||
120 | /** | |
121 | * assoc_array_iterate - Pass all objects in the array to a callback | |
122 | * @array: The array to iterate over. | |
123 | * @iterator: The callback function. | |
124 | * @iterator_data: Private data for the callback function. | |
125 | * | |
126 | * Iterate over all the objects in an associative array. Each one will be | |
127 | * presented to the iterator function. | |
128 | * | |
129 | * If the array is being modified concurrently with the iteration then it is | |
130 | * possible that some objects in the array will be passed to the iterator | |
131 | * callback more than once - though every object should be passed at least | |
132 | * once. If this is undesirable then the caller must lock against modification | |
133 | * for the duration of this function. | |
134 | * | |
135 | * The function will return 0 if no objects were in the array or else it will | |
136 | * return the result of the last iterator function called. Iteration stops | |
137 | * immediately if any call to the iteration function results in a non-zero | |
138 | * return. | |
139 | * | |
140 | * The caller should hold the RCU read lock or better if concurrent | |
141 | * modification is possible. | |
142 | */ | |
143 | int assoc_array_iterate(const struct assoc_array *array, | |
144 | int (*iterator)(const void *object, | |
145 | void *iterator_data), | |
146 | void *iterator_data) | |
147 | { | |
148 | struct assoc_array_ptr *root = ACCESS_ONCE(array->root); | |
149 | ||
150 | if (!root) | |
151 | return 0; | |
152 | return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data); | |
153 | } | |
154 | ||
155 | enum assoc_array_walk_status { | |
156 | assoc_array_walk_tree_empty, | |
157 | assoc_array_walk_found_terminal_node, | |
158 | assoc_array_walk_found_wrong_shortcut, | |
159 | } status; | |
160 | ||
161 | struct assoc_array_walk_result { | |
162 | struct { | |
163 | struct assoc_array_node *node; /* Node in which leaf might be found */ | |
164 | int level; | |
165 | int slot; | |
166 | } terminal_node; | |
167 | struct { | |
168 | struct assoc_array_shortcut *shortcut; | |
169 | int level; | |
170 | int sc_level; | |
171 | unsigned long sc_segments; | |
172 | unsigned long dissimilarity; | |
173 | } wrong_shortcut; | |
174 | }; | |
175 | ||
176 | /* | |
177 | * Navigate through the internal tree looking for the closest node to the key. | |
178 | */ | |
179 | static enum assoc_array_walk_status | |
180 | assoc_array_walk(const struct assoc_array *array, | |
181 | const struct assoc_array_ops *ops, | |
182 | const void *index_key, | |
183 | struct assoc_array_walk_result *result) | |
184 | { | |
185 | struct assoc_array_shortcut *shortcut; | |
186 | struct assoc_array_node *node; | |
187 | struct assoc_array_ptr *cursor, *ptr; | |
188 | unsigned long sc_segments, dissimilarity; | |
189 | unsigned long segments; | |
190 | int level, sc_level, next_sc_level; | |
191 | int slot; | |
192 | ||
193 | pr_devel("-->%s()\n", __func__); | |
194 | ||
195 | cursor = ACCESS_ONCE(array->root); | |
196 | if (!cursor) | |
197 | return assoc_array_walk_tree_empty; | |
198 | ||
199 | level = 0; | |
200 | ||
201 | /* Use segments from the key for the new leaf to navigate through the | |
202 | * internal tree, skipping through nodes and shortcuts that are on | |
203 | * route to the destination. Eventually we'll come to a slot that is | |
204 | * either empty or contains a leaf at which point we've found a node in | |
205 | * which the leaf we're looking for might be found or into which it | |
206 | * should be inserted. | |
207 | */ | |
208 | jumped: | |
209 | segments = ops->get_key_chunk(index_key, level); | |
210 | pr_devel("segments[%d]: %lx\n", level, segments); | |
211 | ||
212 | if (assoc_array_ptr_is_shortcut(cursor)) | |
213 | goto follow_shortcut; | |
214 | ||
215 | consider_node: | |
216 | node = assoc_array_ptr_to_node(cursor); | |
217 | smp_read_barrier_depends(); | |
218 | ||
219 | slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK); | |
220 | slot &= ASSOC_ARRAY_FAN_MASK; | |
221 | ptr = ACCESS_ONCE(node->slots[slot]); | |
222 | ||
223 | pr_devel("consider slot %x [ix=%d type=%lu]\n", | |
224 | slot, level, (unsigned long)ptr & 3); | |
225 | ||
226 | if (!assoc_array_ptr_is_meta(ptr)) { | |
227 | /* The node doesn't have a node/shortcut pointer in the slot | |
228 | * corresponding to the index key that we have to follow. | |
229 | */ | |
230 | result->terminal_node.node = node; | |
231 | result->terminal_node.level = level; | |
232 | result->terminal_node.slot = slot; | |
233 | pr_devel("<--%s() = terminal_node\n", __func__); | |
234 | return assoc_array_walk_found_terminal_node; | |
235 | } | |
236 | ||
237 | if (assoc_array_ptr_is_node(ptr)) { | |
238 | /* There is a pointer to a node in the slot corresponding to | |
239 | * this index key segment, so we need to follow it. | |
240 | */ | |
241 | cursor = ptr; | |
242 | level += ASSOC_ARRAY_LEVEL_STEP; | |
243 | if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) | |
244 | goto consider_node; | |
245 | goto jumped; | |
246 | } | |
247 | ||
248 | /* There is a shortcut in the slot corresponding to the index key | |
249 | * segment. We follow the shortcut if its partial index key matches | |
250 | * this leaf's. Otherwise we need to split the shortcut. | |
251 | */ | |
252 | cursor = ptr; | |
253 | follow_shortcut: | |
254 | shortcut = assoc_array_ptr_to_shortcut(cursor); | |
255 | smp_read_barrier_depends(); | |
256 | pr_devel("shortcut to %d\n", shortcut->skip_to_level); | |
257 | sc_level = level + ASSOC_ARRAY_LEVEL_STEP; | |
258 | BUG_ON(sc_level > shortcut->skip_to_level); | |
259 | ||
260 | do { | |
261 | /* Check the leaf against the shortcut's index key a word at a | |
262 | * time, trimming the final word (the shortcut stores the index | |
263 | * key completely from the root to the shortcut's target). | |
264 | */ | |
265 | if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0) | |
266 | segments = ops->get_key_chunk(index_key, sc_level); | |
267 | ||
268 | sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT]; | |
269 | dissimilarity = segments ^ sc_segments; | |
270 | ||
271 | if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) { | |
272 | /* Trim segments that are beyond the shortcut */ | |
273 | int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK; | |
274 | dissimilarity &= ~(ULONG_MAX << shift); | |
275 | next_sc_level = shortcut->skip_to_level; | |
276 | } else { | |
277 | next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE; | |
278 | next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); | |
279 | } | |
280 | ||
281 | if (dissimilarity != 0) { | |
282 | /* This shortcut points elsewhere */ | |
283 | result->wrong_shortcut.shortcut = shortcut; | |
284 | result->wrong_shortcut.level = level; | |
285 | result->wrong_shortcut.sc_level = sc_level; | |
286 | result->wrong_shortcut.sc_segments = sc_segments; | |
287 | result->wrong_shortcut.dissimilarity = dissimilarity; | |
288 | return assoc_array_walk_found_wrong_shortcut; | |
289 | } | |
290 | ||
291 | sc_level = next_sc_level; | |
292 | } while (sc_level < shortcut->skip_to_level); | |
293 | ||
294 | /* The shortcut matches the leaf's index to this point. */ | |
295 | cursor = ACCESS_ONCE(shortcut->next_node); | |
296 | if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) { | |
297 | level = sc_level; | |
298 | goto jumped; | |
299 | } else { | |
300 | level = sc_level; | |
301 | goto consider_node; | |
302 | } | |
303 | } | |
304 | ||
305 | /** | |
306 | * assoc_array_find - Find an object by index key | |
307 | * @array: The associative array to search. | |
308 | * @ops: The operations to use. | |
309 | * @index_key: The key to the object. | |
310 | * | |
311 | * Find an object in an associative array by walking through the internal tree | |
312 | * to the node that should contain the object and then searching the leaves | |
313 | * there. NULL is returned if the requested object was not found in the array. | |
314 | * | |
315 | * The caller must hold the RCU read lock or better. | |
316 | */ | |
317 | void *assoc_array_find(const struct assoc_array *array, | |
318 | const struct assoc_array_ops *ops, | |
319 | const void *index_key) | |
320 | { | |
321 | struct assoc_array_walk_result result; | |
322 | const struct assoc_array_node *node; | |
323 | const struct assoc_array_ptr *ptr; | |
324 | const void *leaf; | |
325 | int slot; | |
326 | ||
327 | if (assoc_array_walk(array, ops, index_key, &result) != | |
328 | assoc_array_walk_found_terminal_node) | |
329 | return NULL; | |
330 | ||
331 | node = result.terminal_node.node; | |
332 | smp_read_barrier_depends(); | |
333 | ||
334 | /* If the target key is available to us, it's has to be pointed to by | |
335 | * the terminal node. | |
336 | */ | |
337 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
338 | ptr = ACCESS_ONCE(node->slots[slot]); | |
339 | if (ptr && assoc_array_ptr_is_leaf(ptr)) { | |
340 | /* We need a barrier between the read of the pointer | |
341 | * and dereferencing the pointer - but only if we are | |
342 | * actually going to dereference it. | |
343 | */ | |
344 | leaf = assoc_array_ptr_to_leaf(ptr); | |
345 | smp_read_barrier_depends(); | |
346 | if (ops->compare_object(leaf, index_key)) | |
347 | return (void *)leaf; | |
348 | } | |
349 | } | |
350 | ||
351 | return NULL; | |
352 | } | |
353 | ||
354 | /* | |
355 | * Destructively iterate over an associative array. The caller must prevent | |
356 | * other simultaneous accesses. | |
357 | */ | |
358 | static void assoc_array_destroy_subtree(struct assoc_array_ptr *root, | |
359 | const struct assoc_array_ops *ops) | |
360 | { | |
361 | struct assoc_array_shortcut *shortcut; | |
362 | struct assoc_array_node *node; | |
363 | struct assoc_array_ptr *cursor, *parent = NULL; | |
364 | int slot = -1; | |
365 | ||
366 | pr_devel("-->%s()\n", __func__); | |
367 | ||
368 | cursor = root; | |
369 | if (!cursor) { | |
370 | pr_devel("empty\n"); | |
371 | return; | |
372 | } | |
373 | ||
374 | move_to_meta: | |
375 | if (assoc_array_ptr_is_shortcut(cursor)) { | |
376 | /* Descend through a shortcut */ | |
377 | pr_devel("[%d] shortcut\n", slot); | |
378 | BUG_ON(!assoc_array_ptr_is_shortcut(cursor)); | |
379 | shortcut = assoc_array_ptr_to_shortcut(cursor); | |
380 | BUG_ON(shortcut->back_pointer != parent); | |
381 | BUG_ON(slot != -1 && shortcut->parent_slot != slot); | |
382 | parent = cursor; | |
383 | cursor = shortcut->next_node; | |
384 | slot = -1; | |
385 | BUG_ON(!assoc_array_ptr_is_node(cursor)); | |
386 | } | |
387 | ||
388 | pr_devel("[%d] node\n", slot); | |
389 | node = assoc_array_ptr_to_node(cursor); | |
390 | BUG_ON(node->back_pointer != parent); | |
391 | BUG_ON(slot != -1 && node->parent_slot != slot); | |
392 | slot = 0; | |
393 | ||
394 | continue_node: | |
395 | pr_devel("Node %p [back=%p]\n", node, node->back_pointer); | |
396 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
397 | struct assoc_array_ptr *ptr = node->slots[slot]; | |
398 | if (!ptr) | |
399 | continue; | |
400 | if (assoc_array_ptr_is_meta(ptr)) { | |
401 | parent = cursor; | |
402 | cursor = ptr; | |
403 | goto move_to_meta; | |
404 | } | |
405 | ||
406 | if (ops) { | |
407 | pr_devel("[%d] free leaf\n", slot); | |
408 | ops->free_object(assoc_array_ptr_to_leaf(ptr)); | |
409 | } | |
410 | } | |
411 | ||
412 | parent = node->back_pointer; | |
413 | slot = node->parent_slot; | |
414 | pr_devel("free node\n"); | |
415 | kfree(node); | |
416 | if (!parent) | |
417 | return; /* Done */ | |
418 | ||
419 | /* Move back up to the parent (may need to free a shortcut on | |
420 | * the way up) */ | |
421 | if (assoc_array_ptr_is_shortcut(parent)) { | |
422 | shortcut = assoc_array_ptr_to_shortcut(parent); | |
423 | BUG_ON(shortcut->next_node != cursor); | |
424 | cursor = parent; | |
425 | parent = shortcut->back_pointer; | |
426 | slot = shortcut->parent_slot; | |
427 | pr_devel("free shortcut\n"); | |
428 | kfree(shortcut); | |
429 | if (!parent) | |
430 | return; | |
431 | ||
432 | BUG_ON(!assoc_array_ptr_is_node(parent)); | |
433 | } | |
434 | ||
435 | /* Ascend to next slot in parent node */ | |
436 | pr_devel("ascend to %p[%d]\n", parent, slot); | |
437 | cursor = parent; | |
438 | node = assoc_array_ptr_to_node(cursor); | |
439 | slot++; | |
440 | goto continue_node; | |
441 | } | |
442 | ||
443 | /** | |
444 | * assoc_array_destroy - Destroy an associative array | |
445 | * @array: The array to destroy. | |
446 | * @ops: The operations to use. | |
447 | * | |
448 | * Discard all metadata and free all objects in an associative array. The | |
449 | * array will be empty and ready to use again upon completion. This function | |
450 | * cannot fail. | |
451 | * | |
452 | * The caller must prevent all other accesses whilst this takes place as no | |
453 | * attempt is made to adjust pointers gracefully to permit RCU readlock-holding | |
454 | * accesses to continue. On the other hand, no memory allocation is required. | |
455 | */ | |
456 | void assoc_array_destroy(struct assoc_array *array, | |
457 | const struct assoc_array_ops *ops) | |
458 | { | |
459 | assoc_array_destroy_subtree(array->root, ops); | |
460 | array->root = NULL; | |
461 | } | |
462 | ||
463 | /* | |
464 | * Handle insertion into an empty tree. | |
465 | */ | |
466 | static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit) | |
467 | { | |
468 | struct assoc_array_node *new_n0; | |
469 | ||
470 | pr_devel("-->%s()\n", __func__); | |
471 | ||
472 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); | |
473 | if (!new_n0) | |
474 | return false; | |
475 | ||
476 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); | |
477 | edit->leaf_p = &new_n0->slots[0]; | |
478 | edit->adjust_count_on = new_n0; | |
479 | edit->set[0].ptr = &edit->array->root; | |
480 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); | |
481 | ||
482 | pr_devel("<--%s() = ok [no root]\n", __func__); | |
483 | return true; | |
484 | } | |
485 | ||
486 | /* | |
487 | * Handle insertion into a terminal node. | |
488 | */ | |
489 | static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit, | |
490 | const struct assoc_array_ops *ops, | |
491 | const void *index_key, | |
492 | struct assoc_array_walk_result *result) | |
493 | { | |
494 | struct assoc_array_shortcut *shortcut, *new_s0; | |
495 | struct assoc_array_node *node, *new_n0, *new_n1, *side; | |
496 | struct assoc_array_ptr *ptr; | |
497 | unsigned long dissimilarity, base_seg, blank; | |
498 | size_t keylen; | |
499 | bool have_meta; | |
500 | int level, diff; | |
501 | int slot, next_slot, free_slot, i, j; | |
502 | ||
503 | node = result->terminal_node.node; | |
504 | level = result->terminal_node.level; | |
505 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot; | |
506 | ||
507 | pr_devel("-->%s()\n", __func__); | |
508 | ||
509 | /* We arrived at a node which doesn't have an onward node or shortcut | |
510 | * pointer that we have to follow. This means that (a) the leaf we | |
511 | * want must go here (either by insertion or replacement) or (b) we | |
512 | * need to split this node and insert in one of the fragments. | |
513 | */ | |
514 | free_slot = -1; | |
515 | ||
516 | /* Firstly, we have to check the leaves in this node to see if there's | |
517 | * a matching one we should replace in place. | |
518 | */ | |
519 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
520 | ptr = node->slots[i]; | |
521 | if (!ptr) { | |
522 | free_slot = i; | |
523 | continue; | |
524 | } | |
525 | if (ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) { | |
526 | pr_devel("replace in slot %d\n", i); | |
527 | edit->leaf_p = &node->slots[i]; | |
528 | edit->dead_leaf = node->slots[i]; | |
529 | pr_devel("<--%s() = ok [replace]\n", __func__); | |
530 | return true; | |
531 | } | |
532 | } | |
533 | ||
534 | /* If there is a free slot in this node then we can just insert the | |
535 | * leaf here. | |
536 | */ | |
537 | if (free_slot >= 0) { | |
538 | pr_devel("insert in free slot %d\n", free_slot); | |
539 | edit->leaf_p = &node->slots[free_slot]; | |
540 | edit->adjust_count_on = node; | |
541 | pr_devel("<--%s() = ok [insert]\n", __func__); | |
542 | return true; | |
543 | } | |
544 | ||
545 | /* The node has no spare slots - so we're either going to have to split | |
546 | * it or insert another node before it. | |
547 | * | |
548 | * Whatever, we're going to need at least two new nodes - so allocate | |
549 | * those now. We may also need a new shortcut, but we deal with that | |
550 | * when we need it. | |
551 | */ | |
552 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); | |
553 | if (!new_n0) | |
554 | return false; | |
555 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); | |
556 | new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); | |
557 | if (!new_n1) | |
558 | return false; | |
559 | edit->new_meta[1] = assoc_array_node_to_ptr(new_n1); | |
560 | ||
561 | /* We need to find out how similar the leaves are. */ | |
562 | pr_devel("no spare slots\n"); | |
563 | have_meta = false; | |
564 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
565 | ptr = node->slots[i]; | |
566 | if (assoc_array_ptr_is_meta(ptr)) { | |
567 | edit->segment_cache[i] = 0xff; | |
568 | have_meta = true; | |
569 | continue; | |
570 | } | |
571 | base_seg = ops->get_object_key_chunk( | |
572 | assoc_array_ptr_to_leaf(ptr), level); | |
573 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; | |
574 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; | |
575 | } | |
576 | ||
577 | if (have_meta) { | |
578 | pr_devel("have meta\n"); | |
579 | goto split_node; | |
580 | } | |
581 | ||
582 | /* The node contains only leaves */ | |
583 | dissimilarity = 0; | |
584 | base_seg = edit->segment_cache[0]; | |
585 | for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++) | |
586 | dissimilarity |= edit->segment_cache[i] ^ base_seg; | |
587 | ||
588 | pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity); | |
589 | ||
590 | if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) { | |
591 | /* The old leaves all cluster in the same slot. We will need | |
592 | * to insert a shortcut if the new node wants to cluster with them. | |
593 | */ | |
594 | if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0) | |
595 | goto all_leaves_cluster_together; | |
596 | ||
597 | /* Otherwise we can just insert a new node ahead of the old | |
598 | * one. | |
599 | */ | |
600 | goto present_leaves_cluster_but_not_new_leaf; | |
601 | } | |
602 | ||
603 | split_node: | |
604 | pr_devel("split node\n"); | |
605 | ||
606 | /* We need to split the current node; we know that the node doesn't | |
607 | * simply contain a full set of leaves that cluster together (it | |
608 | * contains meta pointers and/or non-clustering leaves). | |
609 | * | |
610 | * We need to expel at least two leaves out of a set consisting of the | |
611 | * leaves in the node and the new leaf. | |
612 | * | |
613 | * We need a new node (n0) to replace the current one and a new node to | |
614 | * take the expelled nodes (n1). | |
615 | */ | |
616 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); | |
617 | new_n0->back_pointer = node->back_pointer; | |
618 | new_n0->parent_slot = node->parent_slot; | |
619 | new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); | |
620 | new_n1->parent_slot = -1; /* Need to calculate this */ | |
621 | ||
622 | do_split_node: | |
623 | pr_devel("do_split_node\n"); | |
624 | ||
625 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; | |
626 | new_n1->nr_leaves_on_branch = 0; | |
627 | ||
628 | /* Begin by finding two matching leaves. There have to be at least two | |
629 | * that match - even if there are meta pointers - because any leaf that | |
630 | * would match a slot with a meta pointer in it must be somewhere | |
631 | * behind that meta pointer and cannot be here. Further, given N | |
632 | * remaining leaf slots, we now have N+1 leaves to go in them. | |
633 | */ | |
634 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
635 | slot = edit->segment_cache[i]; | |
636 | if (slot != 0xff) | |
637 | for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++) | |
638 | if (edit->segment_cache[j] == slot) | |
639 | goto found_slot_for_multiple_occupancy; | |
640 | } | |
641 | found_slot_for_multiple_occupancy: | |
642 | pr_devel("same slot: %x %x [%02x]\n", i, j, slot); | |
643 | BUG_ON(i >= ASSOC_ARRAY_FAN_OUT); | |
644 | BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1); | |
645 | BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT); | |
646 | ||
647 | new_n1->parent_slot = slot; | |
648 | ||
649 | /* Metadata pointers cannot change slot */ | |
650 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) | |
651 | if (assoc_array_ptr_is_meta(node->slots[i])) | |
652 | new_n0->slots[i] = node->slots[i]; | |
653 | else | |
654 | new_n0->slots[i] = NULL; | |
655 | BUG_ON(new_n0->slots[slot] != NULL); | |
656 | new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1); | |
657 | ||
658 | /* Filter the leaf pointers between the new nodes */ | |
659 | free_slot = -1; | |
660 | next_slot = 0; | |
661 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
662 | if (assoc_array_ptr_is_meta(node->slots[i])) | |
663 | continue; | |
664 | if (edit->segment_cache[i] == slot) { | |
665 | new_n1->slots[next_slot++] = node->slots[i]; | |
666 | new_n1->nr_leaves_on_branch++; | |
667 | } else { | |
668 | do { | |
669 | free_slot++; | |
670 | } while (new_n0->slots[free_slot] != NULL); | |
671 | new_n0->slots[free_slot] = node->slots[i]; | |
672 | } | |
673 | } | |
674 | ||
675 | pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot); | |
676 | ||
677 | if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) { | |
678 | do { | |
679 | free_slot++; | |
680 | } while (new_n0->slots[free_slot] != NULL); | |
681 | edit->leaf_p = &new_n0->slots[free_slot]; | |
682 | edit->adjust_count_on = new_n0; | |
683 | } else { | |
684 | edit->leaf_p = &new_n1->slots[next_slot++]; | |
685 | edit->adjust_count_on = new_n1; | |
686 | } | |
687 | ||
688 | BUG_ON(next_slot <= 1); | |
689 | ||
690 | edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0); | |
691 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
692 | if (edit->segment_cache[i] == 0xff) { | |
693 | ptr = node->slots[i]; | |
694 | BUG_ON(assoc_array_ptr_is_leaf(ptr)); | |
695 | if (assoc_array_ptr_is_node(ptr)) { | |
696 | side = assoc_array_ptr_to_node(ptr); | |
697 | edit->set_backpointers[i] = &side->back_pointer; | |
698 | } else { | |
699 | shortcut = assoc_array_ptr_to_shortcut(ptr); | |
700 | edit->set_backpointers[i] = &shortcut->back_pointer; | |
701 | } | |
702 | } | |
703 | } | |
704 | ||
705 | ptr = node->back_pointer; | |
706 | if (!ptr) | |
707 | edit->set[0].ptr = &edit->array->root; | |
708 | else if (assoc_array_ptr_is_node(ptr)) | |
709 | edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot]; | |
710 | else | |
711 | edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node; | |
712 | edit->excised_meta[0] = assoc_array_node_to_ptr(node); | |
713 | pr_devel("<--%s() = ok [split node]\n", __func__); | |
714 | return true; | |
715 | ||
716 | present_leaves_cluster_but_not_new_leaf: | |
717 | /* All the old leaves cluster in the same slot, but the new leaf wants | |
718 | * to go into a different slot, so we create a new node to hold the new | |
719 | * leaf and a pointer to a new node holding all the old leaves. | |
720 | */ | |
721 | pr_devel("present leaves cluster but not new leaf\n"); | |
722 | ||
723 | new_n0->back_pointer = node->back_pointer; | |
724 | new_n0->parent_slot = node->parent_slot; | |
725 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; | |
726 | new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); | |
727 | new_n1->parent_slot = edit->segment_cache[0]; | |
728 | new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch; | |
729 | edit->adjust_count_on = new_n0; | |
730 | ||
731 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) | |
732 | new_n1->slots[i] = node->slots[i]; | |
733 | ||
734 | new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0); | |
735 | edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]]; | |
736 | ||
737 | edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot]; | |
738 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); | |
739 | edit->excised_meta[0] = assoc_array_node_to_ptr(node); | |
740 | pr_devel("<--%s() = ok [insert node before]\n", __func__); | |
741 | return true; | |
742 | ||
743 | all_leaves_cluster_together: | |
744 | /* All the leaves, new and old, want to cluster together in this node | |
745 | * in the same slot, so we have to replace this node with a shortcut to | |
746 | * skip over the identical parts of the key and then place a pair of | |
747 | * nodes, one inside the other, at the end of the shortcut and | |
748 | * distribute the keys between them. | |
749 | * | |
750 | * Firstly we need to work out where the leaves start diverging as a | |
751 | * bit position into their keys so that we know how big the shortcut | |
752 | * needs to be. | |
753 | * | |
754 | * We only need to make a single pass of N of the N+1 leaves because if | |
755 | * any keys differ between themselves at bit X then at least one of | |
756 | * them must also differ with the base key at bit X or before. | |
757 | */ | |
758 | pr_devel("all leaves cluster together\n"); | |
759 | diff = INT_MAX; | |
760 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
761 | int x = ops->diff_objects(assoc_array_ptr_to_leaf(edit->leaf), | |
762 | assoc_array_ptr_to_leaf(node->slots[i])); | |
763 | if (x < diff) { | |
764 | BUG_ON(x < 0); | |
765 | diff = x; | |
766 | } | |
767 | } | |
768 | BUG_ON(diff == INT_MAX); | |
769 | BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP); | |
770 | ||
771 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); | |
772 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; | |
773 | ||
774 | new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + | |
775 | keylen * sizeof(unsigned long), GFP_KERNEL); | |
776 | if (!new_s0) | |
777 | return false; | |
778 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0); | |
779 | ||
780 | edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); | |
781 | new_s0->back_pointer = node->back_pointer; | |
782 | new_s0->parent_slot = node->parent_slot; | |
783 | new_s0->next_node = assoc_array_node_to_ptr(new_n0); | |
784 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); | |
785 | new_n0->parent_slot = 0; | |
786 | new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); | |
787 | new_n1->parent_slot = -1; /* Need to calculate this */ | |
788 | ||
789 | new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK; | |
790 | pr_devel("skip_to_level = %d [diff %d]\n", level, diff); | |
791 | BUG_ON(level <= 0); | |
792 | ||
793 | for (i = 0; i < keylen; i++) | |
794 | new_s0->index_key[i] = | |
795 | ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE); | |
796 | ||
797 | blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); | |
798 | pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); | |
799 | new_s0->index_key[keylen - 1] &= ~blank; | |
800 | ||
801 | /* This now reduces to a node splitting exercise for which we'll need | |
802 | * to regenerate the disparity table. | |
803 | */ | |
804 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
805 | ptr = node->slots[i]; | |
806 | base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr), | |
807 | level); | |
808 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; | |
809 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; | |
810 | } | |
811 | ||
812 | base_seg = ops->get_key_chunk(index_key, level); | |
813 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; | |
814 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK; | |
815 | goto do_split_node; | |
816 | } | |
817 | ||
818 | /* | |
819 | * Handle insertion into the middle of a shortcut. | |
820 | */ | |
821 | static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit, | |
822 | const struct assoc_array_ops *ops, | |
823 | struct assoc_array_walk_result *result) | |
824 | { | |
825 | struct assoc_array_shortcut *shortcut, *new_s0, *new_s1; | |
826 | struct assoc_array_node *node, *new_n0, *side; | |
827 | unsigned long sc_segments, dissimilarity, blank; | |
828 | size_t keylen; | |
829 | int level, sc_level, diff; | |
830 | int sc_slot; | |
831 | ||
832 | shortcut = result->wrong_shortcut.shortcut; | |
833 | level = result->wrong_shortcut.level; | |
834 | sc_level = result->wrong_shortcut.sc_level; | |
835 | sc_segments = result->wrong_shortcut.sc_segments; | |
836 | dissimilarity = result->wrong_shortcut.dissimilarity; | |
837 | ||
838 | pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n", | |
839 | __func__, level, dissimilarity, sc_level); | |
840 | ||
841 | /* We need to split a shortcut and insert a node between the two | |
842 | * pieces. Zero-length pieces will be dispensed with entirely. | |
843 | * | |
844 | * First of all, we need to find out in which level the first | |
845 | * difference was. | |
846 | */ | |
847 | diff = __ffs(dissimilarity); | |
848 | diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK; | |
849 | diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK; | |
850 | pr_devel("diff=%d\n", diff); | |
851 | ||
852 | if (!shortcut->back_pointer) { | |
853 | edit->set[0].ptr = &edit->array->root; | |
854 | } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) { | |
855 | node = assoc_array_ptr_to_node(shortcut->back_pointer); | |
856 | edit->set[0].ptr = &node->slots[shortcut->parent_slot]; | |
857 | } else { | |
858 | BUG(); | |
859 | } | |
860 | ||
861 | edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut); | |
862 | ||
863 | /* Create a new node now since we're going to need it anyway */ | |
864 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); | |
865 | if (!new_n0) | |
866 | return false; | |
867 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); | |
868 | edit->adjust_count_on = new_n0; | |
869 | ||
870 | /* Insert a new shortcut before the new node if this segment isn't of | |
871 | * zero length - otherwise we just connect the new node directly to the | |
872 | * parent. | |
873 | */ | |
874 | level += ASSOC_ARRAY_LEVEL_STEP; | |
875 | if (diff > level) { | |
876 | pr_devel("pre-shortcut %d...%d\n", level, diff); | |
877 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); | |
878 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; | |
879 | ||
880 | new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + | |
881 | keylen * sizeof(unsigned long), GFP_KERNEL); | |
882 | if (!new_s0) | |
883 | return false; | |
884 | edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0); | |
885 | edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); | |
886 | new_s0->back_pointer = shortcut->back_pointer; | |
887 | new_s0->parent_slot = shortcut->parent_slot; | |
888 | new_s0->next_node = assoc_array_node_to_ptr(new_n0); | |
889 | new_s0->skip_to_level = diff; | |
890 | ||
891 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); | |
892 | new_n0->parent_slot = 0; | |
893 | ||
894 | memcpy(new_s0->index_key, shortcut->index_key, | |
895 | keylen * sizeof(unsigned long)); | |
896 | ||
897 | blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); | |
898 | pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank); | |
899 | new_s0->index_key[keylen - 1] &= ~blank; | |
900 | } else { | |
901 | pr_devel("no pre-shortcut\n"); | |
902 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); | |
903 | new_n0->back_pointer = shortcut->back_pointer; | |
904 | new_n0->parent_slot = shortcut->parent_slot; | |
905 | } | |
906 | ||
907 | side = assoc_array_ptr_to_node(shortcut->next_node); | |
908 | new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch; | |
909 | ||
910 | /* We need to know which slot in the new node is going to take a | |
911 | * metadata pointer. | |
912 | */ | |
913 | sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); | |
914 | sc_slot &= ASSOC_ARRAY_FAN_MASK; | |
915 | ||
916 | pr_devel("new slot %lx >> %d -> %d\n", | |
917 | sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot); | |
918 | ||
919 | /* Determine whether we need to follow the new node with a replacement | |
920 | * for the current shortcut. We could in theory reuse the current | |
921 | * shortcut if its parent slot number doesn't change - but that's a | |
922 | * 1-in-16 chance so not worth expending the code upon. | |
923 | */ | |
924 | level = diff + ASSOC_ARRAY_LEVEL_STEP; | |
925 | if (level < shortcut->skip_to_level) { | |
926 | pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level); | |
927 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); | |
928 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; | |
929 | ||
930 | new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) + | |
931 | keylen * sizeof(unsigned long), GFP_KERNEL); | |
932 | if (!new_s1) | |
933 | return false; | |
934 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1); | |
935 | ||
936 | new_s1->back_pointer = assoc_array_node_to_ptr(new_n0); | |
937 | new_s1->parent_slot = sc_slot; | |
938 | new_s1->next_node = shortcut->next_node; | |
939 | new_s1->skip_to_level = shortcut->skip_to_level; | |
940 | ||
941 | new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1); | |
942 | ||
943 | memcpy(new_s1->index_key, shortcut->index_key, | |
944 | keylen * sizeof(unsigned long)); | |
945 | ||
946 | edit->set[1].ptr = &side->back_pointer; | |
947 | edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1); | |
948 | } else { | |
949 | pr_devel("no post-shortcut\n"); | |
950 | ||
951 | /* We don't have to replace the pointed-to node as long as we | |
952 | * use memory barriers to make sure the parent slot number is | |
953 | * changed before the back pointer (the parent slot number is | |
954 | * irrelevant to the old parent shortcut). | |
955 | */ | |
956 | new_n0->slots[sc_slot] = shortcut->next_node; | |
957 | edit->set_parent_slot[0].p = &side->parent_slot; | |
958 | edit->set_parent_slot[0].to = sc_slot; | |
959 | edit->set[1].ptr = &side->back_pointer; | |
960 | edit->set[1].to = assoc_array_node_to_ptr(new_n0); | |
961 | } | |
962 | ||
963 | /* Install the new leaf in a spare slot in the new node. */ | |
964 | if (sc_slot == 0) | |
965 | edit->leaf_p = &new_n0->slots[1]; | |
966 | else | |
967 | edit->leaf_p = &new_n0->slots[0]; | |
968 | ||
969 | pr_devel("<--%s() = ok [split shortcut]\n", __func__); | |
970 | return edit; | |
971 | } | |
972 | ||
973 | /** | |
974 | * assoc_array_insert - Script insertion of an object into an associative array | |
975 | * @array: The array to insert into. | |
976 | * @ops: The operations to use. | |
977 | * @index_key: The key to insert at. | |
978 | * @object: The object to insert. | |
979 | * | |
980 | * Precalculate and preallocate a script for the insertion or replacement of an | |
981 | * object in an associative array. This results in an edit script that can | |
982 | * either be applied or cancelled. | |
983 | * | |
984 | * The function returns a pointer to an edit script or -ENOMEM. | |
985 | * | |
986 | * The caller should lock against other modifications and must continue to hold | |
987 | * the lock until assoc_array_apply_edit() has been called. | |
988 | * | |
989 | * Accesses to the tree may take place concurrently with this function, | |
990 | * provided they hold the RCU read lock. | |
991 | */ | |
992 | struct assoc_array_edit *assoc_array_insert(struct assoc_array *array, | |
993 | const struct assoc_array_ops *ops, | |
994 | const void *index_key, | |
995 | void *object) | |
996 | { | |
997 | struct assoc_array_walk_result result; | |
998 | struct assoc_array_edit *edit; | |
999 | ||
1000 | pr_devel("-->%s()\n", __func__); | |
1001 | ||
1002 | /* The leaf pointer we're given must not have the bottom bit set as we | |
1003 | * use those for type-marking the pointer. NULL pointers are also not | |
1004 | * allowed as they indicate an empty slot but we have to allow them | |
1005 | * here as they can be updated later. | |
1006 | */ | |
1007 | BUG_ON(assoc_array_ptr_is_meta(object)); | |
1008 | ||
1009 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); | |
1010 | if (!edit) | |
1011 | return ERR_PTR(-ENOMEM); | |
1012 | edit->array = array; | |
1013 | edit->ops = ops; | |
1014 | edit->leaf = assoc_array_leaf_to_ptr(object); | |
1015 | edit->adjust_count_by = 1; | |
1016 | ||
1017 | switch (assoc_array_walk(array, ops, index_key, &result)) { | |
1018 | case assoc_array_walk_tree_empty: | |
1019 | /* Allocate a root node if there isn't one yet */ | |
1020 | if (!assoc_array_insert_in_empty_tree(edit)) | |
1021 | goto enomem; | |
1022 | return edit; | |
1023 | ||
1024 | case assoc_array_walk_found_terminal_node: | |
1025 | /* We found a node that doesn't have a node/shortcut pointer in | |
1026 | * the slot corresponding to the index key that we have to | |
1027 | * follow. | |
1028 | */ | |
1029 | if (!assoc_array_insert_into_terminal_node(edit, ops, index_key, | |
1030 | &result)) | |
1031 | goto enomem; | |
1032 | return edit; | |
1033 | ||
1034 | case assoc_array_walk_found_wrong_shortcut: | |
1035 | /* We found a shortcut that didn't match our key in a slot we | |
1036 | * needed to follow. | |
1037 | */ | |
1038 | if (!assoc_array_insert_mid_shortcut(edit, ops, &result)) | |
1039 | goto enomem; | |
1040 | return edit; | |
1041 | } | |
1042 | ||
1043 | enomem: | |
1044 | /* Clean up after an out of memory error */ | |
1045 | pr_devel("enomem\n"); | |
1046 | assoc_array_cancel_edit(edit); | |
1047 | return ERR_PTR(-ENOMEM); | |
1048 | } | |
1049 | ||
1050 | /** | |
1051 | * assoc_array_insert_set_object - Set the new object pointer in an edit script | |
1052 | * @edit: The edit script to modify. | |
1053 | * @object: The object pointer to set. | |
1054 | * | |
1055 | * Change the object to be inserted in an edit script. The object pointed to | |
1056 | * by the old object is not freed. This must be done prior to applying the | |
1057 | * script. | |
1058 | */ | |
1059 | void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object) | |
1060 | { | |
1061 | BUG_ON(!object); | |
1062 | edit->leaf = assoc_array_leaf_to_ptr(object); | |
1063 | } | |
1064 | ||
1065 | struct assoc_array_delete_collapse_context { | |
1066 | struct assoc_array_node *node; | |
1067 | const void *skip_leaf; | |
1068 | int slot; | |
1069 | }; | |
1070 | ||
1071 | /* | |
1072 | * Subtree collapse to node iterator. | |
1073 | */ | |
1074 | static int assoc_array_delete_collapse_iterator(const void *leaf, | |
1075 | void *iterator_data) | |
1076 | { | |
1077 | struct assoc_array_delete_collapse_context *collapse = iterator_data; | |
1078 | ||
1079 | if (leaf == collapse->skip_leaf) | |
1080 | return 0; | |
1081 | ||
1082 | BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT); | |
1083 | ||
1084 | collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf); | |
1085 | return 0; | |
1086 | } | |
1087 | ||
1088 | /** | |
1089 | * assoc_array_delete - Script deletion of an object from an associative array | |
1090 | * @array: The array to search. | |
1091 | * @ops: The operations to use. | |
1092 | * @index_key: The key to the object. | |
1093 | * | |
1094 | * Precalculate and preallocate a script for the deletion of an object from an | |
1095 | * associative array. This results in an edit script that can either be | |
1096 | * applied or cancelled. | |
1097 | * | |
1098 | * The function returns a pointer to an edit script if the object was found, | |
1099 | * NULL if the object was not found or -ENOMEM. | |
1100 | * | |
1101 | * The caller should lock against other modifications and must continue to hold | |
1102 | * the lock until assoc_array_apply_edit() has been called. | |
1103 | * | |
1104 | * Accesses to the tree may take place concurrently with this function, | |
1105 | * provided they hold the RCU read lock. | |
1106 | */ | |
1107 | struct assoc_array_edit *assoc_array_delete(struct assoc_array *array, | |
1108 | const struct assoc_array_ops *ops, | |
1109 | const void *index_key) | |
1110 | { | |
1111 | struct assoc_array_delete_collapse_context collapse; | |
1112 | struct assoc_array_walk_result result; | |
1113 | struct assoc_array_node *node, *new_n0; | |
1114 | struct assoc_array_edit *edit; | |
1115 | struct assoc_array_ptr *ptr; | |
1116 | bool has_meta; | |
1117 | int slot, i; | |
1118 | ||
1119 | pr_devel("-->%s()\n", __func__); | |
1120 | ||
1121 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); | |
1122 | if (!edit) | |
1123 | return ERR_PTR(-ENOMEM); | |
1124 | edit->array = array; | |
1125 | edit->ops = ops; | |
1126 | edit->adjust_count_by = -1; | |
1127 | ||
1128 | switch (assoc_array_walk(array, ops, index_key, &result)) { | |
1129 | case assoc_array_walk_found_terminal_node: | |
1130 | /* We found a node that should contain the leaf we've been | |
1131 | * asked to remove - *if* it's in the tree. | |
1132 | */ | |
1133 | pr_devel("terminal_node\n"); | |
1134 | node = result.terminal_node.node; | |
1135 | ||
1136 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
1137 | ptr = node->slots[slot]; | |
1138 | if (ptr && | |
1139 | assoc_array_ptr_is_leaf(ptr) && | |
1140 | ops->compare_object(assoc_array_ptr_to_leaf(ptr), | |
1141 | index_key)) | |
1142 | goto found_leaf; | |
1143 | } | |
1144 | case assoc_array_walk_tree_empty: | |
1145 | case assoc_array_walk_found_wrong_shortcut: | |
1146 | default: | |
1147 | assoc_array_cancel_edit(edit); | |
1148 | pr_devel("not found\n"); | |
1149 | return NULL; | |
1150 | } | |
1151 | ||
1152 | found_leaf: | |
1153 | BUG_ON(array->nr_leaves_on_tree <= 0); | |
1154 | ||
1155 | /* In the simplest form of deletion we just clear the slot and release | |
1156 | * the leaf after a suitable interval. | |
1157 | */ | |
1158 | edit->dead_leaf = node->slots[slot]; | |
1159 | edit->set[0].ptr = &node->slots[slot]; | |
1160 | edit->set[0].to = NULL; | |
1161 | edit->adjust_count_on = node; | |
1162 | ||
1163 | /* If that concludes erasure of the last leaf, then delete the entire | |
1164 | * internal array. | |
1165 | */ | |
1166 | if (array->nr_leaves_on_tree == 1) { | |
1167 | edit->set[1].ptr = &array->root; | |
1168 | edit->set[1].to = NULL; | |
1169 | edit->adjust_count_on = NULL; | |
1170 | edit->excised_subtree = array->root; | |
1171 | pr_devel("all gone\n"); | |
1172 | return edit; | |
1173 | } | |
1174 | ||
1175 | /* However, we'd also like to clear up some metadata blocks if we | |
1176 | * possibly can. | |
1177 | * | |
1178 | * We go for a simple algorithm of: if this node has FAN_OUT or fewer | |
1179 | * leaves in it, then attempt to collapse it - and attempt to | |
1180 | * recursively collapse up the tree. | |
1181 | * | |
1182 | * We could also try and collapse in partially filled subtrees to take | |
1183 | * up space in this node. | |
1184 | */ | |
1185 | if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { | |
1186 | struct assoc_array_node *parent, *grandparent; | |
1187 | struct assoc_array_ptr *ptr; | |
1188 | ||
1189 | /* First of all, we need to know if this node has metadata so | |
1190 | * that we don't try collapsing if all the leaves are already | |
1191 | * here. | |
1192 | */ | |
1193 | has_meta = false; | |
1194 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
1195 | ptr = node->slots[i]; | |
1196 | if (assoc_array_ptr_is_meta(ptr)) { | |
1197 | has_meta = true; | |
1198 | break; | |
1199 | } | |
1200 | } | |
1201 | ||
1202 | pr_devel("leaves: %ld [m=%d]\n", | |
1203 | node->nr_leaves_on_branch - 1, has_meta); | |
1204 | ||
1205 | /* Look further up the tree to see if we can collapse this node | |
1206 | * into a more proximal node too. | |
1207 | */ | |
1208 | parent = node; | |
1209 | collapse_up: | |
1210 | pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch); | |
1211 | ||
1212 | ptr = parent->back_pointer; | |
1213 | if (!ptr) | |
1214 | goto do_collapse; | |
1215 | if (assoc_array_ptr_is_shortcut(ptr)) { | |
1216 | struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr); | |
1217 | ptr = s->back_pointer; | |
1218 | if (!ptr) | |
1219 | goto do_collapse; | |
1220 | } | |
1221 | ||
1222 | grandparent = assoc_array_ptr_to_node(ptr); | |
1223 | if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { | |
1224 | parent = grandparent; | |
1225 | goto collapse_up; | |
1226 | } | |
1227 | ||
1228 | do_collapse: | |
1229 | /* There's no point collapsing if the original node has no meta | |
1230 | * pointers to discard and if we didn't merge into one of that | |
1231 | * node's ancestry. | |
1232 | */ | |
1233 | if (has_meta || parent != node) { | |
1234 | node = parent; | |
1235 | ||
1236 | /* Create a new node to collapse into */ | |
1237 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); | |
1238 | if (!new_n0) | |
1239 | goto enomem; | |
1240 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); | |
1241 | ||
1242 | new_n0->back_pointer = node->back_pointer; | |
1243 | new_n0->parent_slot = node->parent_slot; | |
1244 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; | |
1245 | edit->adjust_count_on = new_n0; | |
1246 | ||
1247 | collapse.node = new_n0; | |
1248 | collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf); | |
1249 | collapse.slot = 0; | |
1250 | assoc_array_subtree_iterate(assoc_array_node_to_ptr(node), | |
1251 | node->back_pointer, | |
1252 | assoc_array_delete_collapse_iterator, | |
1253 | &collapse); | |
1254 | pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch); | |
1255 | BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1); | |
1256 | ||
1257 | if (!node->back_pointer) { | |
1258 | edit->set[1].ptr = &array->root; | |
1259 | } else if (assoc_array_ptr_is_leaf(node->back_pointer)) { | |
1260 | BUG(); | |
1261 | } else if (assoc_array_ptr_is_node(node->back_pointer)) { | |
1262 | struct assoc_array_node *p = | |
1263 | assoc_array_ptr_to_node(node->back_pointer); | |
1264 | edit->set[1].ptr = &p->slots[node->parent_slot]; | |
1265 | } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) { | |
1266 | struct assoc_array_shortcut *s = | |
1267 | assoc_array_ptr_to_shortcut(node->back_pointer); | |
1268 | edit->set[1].ptr = &s->next_node; | |
1269 | } | |
1270 | edit->set[1].to = assoc_array_node_to_ptr(new_n0); | |
1271 | edit->excised_subtree = assoc_array_node_to_ptr(node); | |
1272 | } | |
1273 | } | |
1274 | ||
1275 | return edit; | |
1276 | ||
1277 | enomem: | |
1278 | /* Clean up after an out of memory error */ | |
1279 | pr_devel("enomem\n"); | |
1280 | assoc_array_cancel_edit(edit); | |
1281 | return ERR_PTR(-ENOMEM); | |
1282 | } | |
1283 | ||
1284 | /** | |
1285 | * assoc_array_clear - Script deletion of all objects from an associative array | |
1286 | * @array: The array to clear. | |
1287 | * @ops: The operations to use. | |
1288 | * | |
1289 | * Precalculate and preallocate a script for the deletion of all the objects | |
1290 | * from an associative array. This results in an edit script that can either | |
1291 | * be applied or cancelled. | |
1292 | * | |
1293 | * The function returns a pointer to an edit script if there are objects to be | |
1294 | * deleted, NULL if there are no objects in the array or -ENOMEM. | |
1295 | * | |
1296 | * The caller should lock against other modifications and must continue to hold | |
1297 | * the lock until assoc_array_apply_edit() has been called. | |
1298 | * | |
1299 | * Accesses to the tree may take place concurrently with this function, | |
1300 | * provided they hold the RCU read lock. | |
1301 | */ | |
1302 | struct assoc_array_edit *assoc_array_clear(struct assoc_array *array, | |
1303 | const struct assoc_array_ops *ops) | |
1304 | { | |
1305 | struct assoc_array_edit *edit; | |
1306 | ||
1307 | pr_devel("-->%s()\n", __func__); | |
1308 | ||
1309 | if (!array->root) | |
1310 | return NULL; | |
1311 | ||
1312 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); | |
1313 | if (!edit) | |
1314 | return ERR_PTR(-ENOMEM); | |
1315 | edit->array = array; | |
1316 | edit->ops = ops; | |
1317 | edit->set[1].ptr = &array->root; | |
1318 | edit->set[1].to = NULL; | |
1319 | edit->excised_subtree = array->root; | |
1320 | edit->ops_for_excised_subtree = ops; | |
1321 | pr_devel("all gone\n"); | |
1322 | return edit; | |
1323 | } | |
1324 | ||
1325 | /* | |
1326 | * Handle the deferred destruction after an applied edit. | |
1327 | */ | |
1328 | static void assoc_array_rcu_cleanup(struct rcu_head *head) | |
1329 | { | |
1330 | struct assoc_array_edit *edit = | |
1331 | container_of(head, struct assoc_array_edit, rcu); | |
1332 | int i; | |
1333 | ||
1334 | pr_devel("-->%s()\n", __func__); | |
1335 | ||
1336 | if (edit->dead_leaf) | |
1337 | edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf)); | |
1338 | for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++) | |
1339 | if (edit->excised_meta[i]) | |
1340 | kfree(assoc_array_ptr_to_node(edit->excised_meta[i])); | |
1341 | ||
1342 | if (edit->excised_subtree) { | |
1343 | BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree)); | |
1344 | if (assoc_array_ptr_is_node(edit->excised_subtree)) { | |
1345 | struct assoc_array_node *n = | |
1346 | assoc_array_ptr_to_node(edit->excised_subtree); | |
1347 | n->back_pointer = NULL; | |
1348 | } else { | |
1349 | struct assoc_array_shortcut *s = | |
1350 | assoc_array_ptr_to_shortcut(edit->excised_subtree); | |
1351 | s->back_pointer = NULL; | |
1352 | } | |
1353 | assoc_array_destroy_subtree(edit->excised_subtree, | |
1354 | edit->ops_for_excised_subtree); | |
1355 | } | |
1356 | ||
1357 | kfree(edit); | |
1358 | } | |
1359 | ||
1360 | /** | |
1361 | * assoc_array_apply_edit - Apply an edit script to an associative array | |
1362 | * @edit: The script to apply. | |
1363 | * | |
1364 | * Apply an edit script to an associative array to effect an insertion, | |
1365 | * deletion or clearance. As the edit script includes preallocated memory, | |
1366 | * this is guaranteed not to fail. | |
1367 | * | |
1368 | * The edit script, dead objects and dead metadata will be scheduled for | |
1369 | * destruction after an RCU grace period to permit those doing read-only | |
1370 | * accesses on the array to continue to do so under the RCU read lock whilst | |
1371 | * the edit is taking place. | |
1372 | */ | |
1373 | void assoc_array_apply_edit(struct assoc_array_edit *edit) | |
1374 | { | |
1375 | struct assoc_array_shortcut *shortcut; | |
1376 | struct assoc_array_node *node; | |
1377 | struct assoc_array_ptr *ptr; | |
1378 | int i; | |
1379 | ||
1380 | pr_devel("-->%s()\n", __func__); | |
1381 | ||
1382 | smp_wmb(); | |
1383 | if (edit->leaf_p) | |
1384 | *edit->leaf_p = edit->leaf; | |
1385 | ||
1386 | smp_wmb(); | |
1387 | for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++) | |
1388 | if (edit->set_parent_slot[i].p) | |
1389 | *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to; | |
1390 | ||
1391 | smp_wmb(); | |
1392 | for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++) | |
1393 | if (edit->set_backpointers[i]) | |
1394 | *edit->set_backpointers[i] = edit->set_backpointers_to; | |
1395 | ||
1396 | smp_wmb(); | |
1397 | for (i = 0; i < ARRAY_SIZE(edit->set); i++) | |
1398 | if (edit->set[i].ptr) | |
1399 | *edit->set[i].ptr = edit->set[i].to; | |
1400 | ||
1401 | if (edit->array->root == NULL) { | |
1402 | edit->array->nr_leaves_on_tree = 0; | |
1403 | } else if (edit->adjust_count_on) { | |
1404 | node = edit->adjust_count_on; | |
1405 | for (;;) { | |
1406 | node->nr_leaves_on_branch += edit->adjust_count_by; | |
1407 | ||
1408 | ptr = node->back_pointer; | |
1409 | if (!ptr) | |
1410 | break; | |
1411 | if (assoc_array_ptr_is_shortcut(ptr)) { | |
1412 | shortcut = assoc_array_ptr_to_shortcut(ptr); | |
1413 | ptr = shortcut->back_pointer; | |
1414 | if (!ptr) | |
1415 | break; | |
1416 | } | |
1417 | BUG_ON(!assoc_array_ptr_is_node(ptr)); | |
1418 | node = assoc_array_ptr_to_node(ptr); | |
1419 | } | |
1420 | ||
1421 | edit->array->nr_leaves_on_tree += edit->adjust_count_by; | |
1422 | } | |
1423 | ||
1424 | call_rcu(&edit->rcu, assoc_array_rcu_cleanup); | |
1425 | } | |
1426 | ||
1427 | /** | |
1428 | * assoc_array_cancel_edit - Discard an edit script. | |
1429 | * @edit: The script to discard. | |
1430 | * | |
1431 | * Free an edit script and all the preallocated data it holds without making | |
1432 | * any changes to the associative array it was intended for. | |
1433 | * | |
1434 | * NOTE! In the case of an insertion script, this does _not_ release the leaf | |
1435 | * that was to be inserted. That is left to the caller. | |
1436 | */ | |
1437 | void assoc_array_cancel_edit(struct assoc_array_edit *edit) | |
1438 | { | |
1439 | struct assoc_array_ptr *ptr; | |
1440 | int i; | |
1441 | ||
1442 | pr_devel("-->%s()\n", __func__); | |
1443 | ||
1444 | /* Clean up after an out of memory error */ | |
1445 | for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) { | |
1446 | ptr = edit->new_meta[i]; | |
1447 | if (ptr) { | |
1448 | if (assoc_array_ptr_is_node(ptr)) | |
1449 | kfree(assoc_array_ptr_to_node(ptr)); | |
1450 | else | |
1451 | kfree(assoc_array_ptr_to_shortcut(ptr)); | |
1452 | } | |
1453 | } | |
1454 | kfree(edit); | |
1455 | } | |
1456 | ||
1457 | /** | |
1458 | * assoc_array_gc - Garbage collect an associative array. | |
1459 | * @array: The array to clean. | |
1460 | * @ops: The operations to use. | |
1461 | * @iterator: A callback function to pass judgement on each object. | |
1462 | * @iterator_data: Private data for the callback function. | |
1463 | * | |
1464 | * Collect garbage from an associative array and pack down the internal tree to | |
1465 | * save memory. | |
1466 | * | |
1467 | * The iterator function is asked to pass judgement upon each object in the | |
1468 | * array. If it returns false, the object is discard and if it returns true, | |
1469 | * the object is kept. If it returns true, it must increment the object's | |
1470 | * usage count (or whatever it needs to do to retain it) before returning. | |
1471 | * | |
1472 | * This function returns 0 if successful or -ENOMEM if out of memory. In the | |
1473 | * latter case, the array is not changed. | |
1474 | * | |
1475 | * The caller should lock against other modifications and must continue to hold | |
1476 | * the lock until assoc_array_apply_edit() has been called. | |
1477 | * | |
1478 | * Accesses to the tree may take place concurrently with this function, | |
1479 | * provided they hold the RCU read lock. | |
1480 | */ | |
1481 | int assoc_array_gc(struct assoc_array *array, | |
1482 | const struct assoc_array_ops *ops, | |
1483 | bool (*iterator)(void *object, void *iterator_data), | |
1484 | void *iterator_data) | |
1485 | { | |
1486 | struct assoc_array_shortcut *shortcut, *new_s; | |
1487 | struct assoc_array_node *node, *new_n; | |
1488 | struct assoc_array_edit *edit; | |
1489 | struct assoc_array_ptr *cursor, *ptr; | |
1490 | struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp; | |
1491 | unsigned long nr_leaves_on_tree; | |
1492 | int keylen, slot, nr_free, next_slot, i; | |
1493 | ||
1494 | pr_devel("-->%s()\n", __func__); | |
1495 | ||
1496 | if (!array->root) | |
1497 | return 0; | |
1498 | ||
1499 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); | |
1500 | if (!edit) | |
1501 | return -ENOMEM; | |
1502 | edit->array = array; | |
1503 | edit->ops = ops; | |
1504 | edit->ops_for_excised_subtree = ops; | |
1505 | edit->set[0].ptr = &array->root; | |
1506 | edit->excised_subtree = array->root; | |
1507 | ||
1508 | new_root = new_parent = NULL; | |
1509 | new_ptr_pp = &new_root; | |
1510 | cursor = array->root; | |
1511 | ||
1512 | descend: | |
1513 | /* If this point is a shortcut, then we need to duplicate it and | |
1514 | * advance the target cursor. | |
1515 | */ | |
1516 | if (assoc_array_ptr_is_shortcut(cursor)) { | |
1517 | shortcut = assoc_array_ptr_to_shortcut(cursor); | |
1518 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); | |
1519 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; | |
1520 | new_s = kmalloc(sizeof(struct assoc_array_shortcut) + | |
1521 | keylen * sizeof(unsigned long), GFP_KERNEL); | |
1522 | if (!new_s) | |
1523 | goto enomem; | |
1524 | pr_devel("dup shortcut %p -> %p\n", shortcut, new_s); | |
1525 | memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) + | |
1526 | keylen * sizeof(unsigned long))); | |
1527 | new_s->back_pointer = new_parent; | |
1528 | new_s->parent_slot = shortcut->parent_slot; | |
1529 | *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s); | |
1530 | new_ptr_pp = &new_s->next_node; | |
1531 | cursor = shortcut->next_node; | |
1532 | } | |
1533 | ||
1534 | /* Duplicate the node at this position */ | |
1535 | node = assoc_array_ptr_to_node(cursor); | |
1536 | new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); | |
1537 | if (!new_n) | |
1538 | goto enomem; | |
1539 | pr_devel("dup node %p -> %p\n", node, new_n); | |
1540 | new_n->back_pointer = new_parent; | |
1541 | new_n->parent_slot = node->parent_slot; | |
1542 | *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n); | |
1543 | new_ptr_pp = NULL; | |
1544 | slot = 0; | |
1545 | ||
1546 | continue_node: | |
1547 | /* Filter across any leaves and gc any subtrees */ | |
1548 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
1549 | ptr = node->slots[slot]; | |
1550 | if (!ptr) | |
1551 | continue; | |
1552 | ||
1553 | if (assoc_array_ptr_is_leaf(ptr)) { | |
1554 | if (iterator(assoc_array_ptr_to_leaf(ptr), | |
1555 | iterator_data)) | |
1556 | /* The iterator will have done any reference | |
1557 | * counting on the object for us. | |
1558 | */ | |
1559 | new_n->slots[slot] = ptr; | |
1560 | continue; | |
1561 | } | |
1562 | ||
1563 | new_ptr_pp = &new_n->slots[slot]; | |
1564 | cursor = ptr; | |
1565 | goto descend; | |
1566 | } | |
1567 | ||
1568 | pr_devel("-- compress node %p --\n", new_n); | |
1569 | ||
1570 | /* Count up the number of empty slots in this node and work out the | |
1571 | * subtree leaf count. | |
1572 | */ | |
1573 | new_n->nr_leaves_on_branch = 0; | |
1574 | nr_free = 0; | |
1575 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
1576 | ptr = new_n->slots[slot]; | |
1577 | if (!ptr) | |
1578 | nr_free++; | |
1579 | else if (assoc_array_ptr_is_leaf(ptr)) | |
1580 | new_n->nr_leaves_on_branch++; | |
1581 | } | |
1582 | pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch); | |
1583 | ||
1584 | /* See what we can fold in */ | |
1585 | next_slot = 0; | |
1586 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { | |
1587 | struct assoc_array_shortcut *s; | |
1588 | struct assoc_array_node *child; | |
1589 | ||
1590 | ptr = new_n->slots[slot]; | |
1591 | if (!ptr || assoc_array_ptr_is_leaf(ptr)) | |
1592 | continue; | |
1593 | ||
1594 | s = NULL; | |
1595 | if (assoc_array_ptr_is_shortcut(ptr)) { | |
1596 | s = assoc_array_ptr_to_shortcut(ptr); | |
1597 | ptr = s->next_node; | |
1598 | } | |
1599 | ||
1600 | child = assoc_array_ptr_to_node(ptr); | |
1601 | new_n->nr_leaves_on_branch += child->nr_leaves_on_branch; | |
1602 | ||
1603 | if (child->nr_leaves_on_branch <= nr_free + 1) { | |
1604 | /* Fold the child node into this one */ | |
1605 | pr_devel("[%d] fold node %lu/%d [nx %d]\n", | |
1606 | slot, child->nr_leaves_on_branch, nr_free + 1, | |
1607 | next_slot); | |
1608 | ||
1609 | /* We would already have reaped an intervening shortcut | |
1610 | * on the way back up the tree. | |
1611 | */ | |
1612 | BUG_ON(s); | |
1613 | ||
1614 | new_n->slots[slot] = NULL; | |
1615 | nr_free++; | |
1616 | if (slot < next_slot) | |
1617 | next_slot = slot; | |
1618 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { | |
1619 | struct assoc_array_ptr *p = child->slots[i]; | |
1620 | if (!p) | |
1621 | continue; | |
1622 | BUG_ON(assoc_array_ptr_is_meta(p)); | |
1623 | while (new_n->slots[next_slot]) | |
1624 | next_slot++; | |
1625 | BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT); | |
1626 | new_n->slots[next_slot++] = p; | |
1627 | nr_free--; | |
1628 | } | |
1629 | kfree(child); | |
1630 | } else { | |
1631 | pr_devel("[%d] retain node %lu/%d [nx %d]\n", | |
1632 | slot, child->nr_leaves_on_branch, nr_free + 1, | |
1633 | next_slot); | |
1634 | } | |
1635 | } | |
1636 | ||
1637 | pr_devel("after: %lu\n", new_n->nr_leaves_on_branch); | |
1638 | ||
1639 | nr_leaves_on_tree = new_n->nr_leaves_on_branch; | |
1640 | ||
1641 | /* Excise this node if it is singly occupied by a shortcut */ | |
1642 | if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) { | |
1643 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) | |
1644 | if ((ptr = new_n->slots[slot])) | |
1645 | break; | |
1646 | ||
1647 | if (assoc_array_ptr_is_meta(ptr) && | |
1648 | assoc_array_ptr_is_shortcut(ptr)) { | |
1649 | pr_devel("excise node %p with 1 shortcut\n", new_n); | |
1650 | new_s = assoc_array_ptr_to_shortcut(ptr); | |
1651 | new_parent = new_n->back_pointer; | |
1652 | slot = new_n->parent_slot; | |
1653 | kfree(new_n); | |
1654 | if (!new_parent) { | |
1655 | new_s->back_pointer = NULL; | |
1656 | new_s->parent_slot = 0; | |
1657 | new_root = ptr; | |
1658 | goto gc_complete; | |
1659 | } | |
1660 | ||
1661 | if (assoc_array_ptr_is_shortcut(new_parent)) { | |
1662 | /* We can discard any preceding shortcut also */ | |
1663 | struct assoc_array_shortcut *s = | |
1664 | assoc_array_ptr_to_shortcut(new_parent); | |
1665 | ||
1666 | pr_devel("excise preceding shortcut\n"); | |
1667 | ||
1668 | new_parent = new_s->back_pointer = s->back_pointer; | |
1669 | slot = new_s->parent_slot = s->parent_slot; | |
1670 | kfree(s); | |
1671 | if (!new_parent) { | |
1672 | new_s->back_pointer = NULL; | |
1673 | new_s->parent_slot = 0; | |
1674 | new_root = ptr; | |
1675 | goto gc_complete; | |
1676 | } | |
1677 | } | |
1678 | ||
1679 | new_s->back_pointer = new_parent; | |
1680 | new_s->parent_slot = slot; | |
1681 | new_n = assoc_array_ptr_to_node(new_parent); | |
1682 | new_n->slots[slot] = ptr; | |
1683 | goto ascend_old_tree; | |
1684 | } | |
1685 | } | |
1686 | ||
1687 | /* Excise any shortcuts we might encounter that point to nodes that | |
1688 | * only contain leaves. | |
1689 | */ | |
1690 | ptr = new_n->back_pointer; | |
1691 | if (!ptr) | |
1692 | goto gc_complete; | |
1693 | ||
1694 | if (assoc_array_ptr_is_shortcut(ptr)) { | |
1695 | new_s = assoc_array_ptr_to_shortcut(ptr); | |
1696 | new_parent = new_s->back_pointer; | |
1697 | slot = new_s->parent_slot; | |
1698 | ||
1699 | if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { | |
1700 | struct assoc_array_node *n; | |
1701 | ||
1702 | pr_devel("excise shortcut\n"); | |
1703 | new_n->back_pointer = new_parent; | |
1704 | new_n->parent_slot = slot; | |
1705 | kfree(new_s); | |
1706 | if (!new_parent) { | |
1707 | new_root = assoc_array_node_to_ptr(new_n); | |
1708 | goto gc_complete; | |
1709 | } | |
1710 | ||
1711 | n = assoc_array_ptr_to_node(new_parent); | |
1712 | n->slots[slot] = assoc_array_node_to_ptr(new_n); | |
1713 | } | |
1714 | } else { | |
1715 | new_parent = ptr; | |
1716 | } | |
1717 | new_n = assoc_array_ptr_to_node(new_parent); | |
1718 | ||
1719 | ascend_old_tree: | |
1720 | ptr = node->back_pointer; | |
1721 | if (assoc_array_ptr_is_shortcut(ptr)) { | |
1722 | shortcut = assoc_array_ptr_to_shortcut(ptr); | |
1723 | slot = shortcut->parent_slot; | |
1724 | cursor = shortcut->back_pointer; | |
1725 | } else { | |
1726 | slot = node->parent_slot; | |
1727 | cursor = ptr; | |
1728 | } | |
1729 | BUG_ON(!ptr); | |
1730 | node = assoc_array_ptr_to_node(cursor); | |
1731 | slot++; | |
1732 | goto continue_node; | |
1733 | ||
1734 | gc_complete: | |
1735 | edit->set[0].to = new_root; | |
1736 | assoc_array_apply_edit(edit); | |
1737 | edit->array->nr_leaves_on_tree = nr_leaves_on_tree; | |
1738 | return 0; | |
1739 | ||
1740 | enomem: | |
1741 | pr_devel("enomem\n"); | |
1742 | assoc_array_destroy_subtree(new_root, edit->ops); | |
1743 | kfree(edit); | |
1744 | return -ENOMEM; | |
1745 | } |