blob: 3b46c5433b7acd853e5f9ca9381f6f6b30db6884
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/rcupdate.h> |
15 | #include <linux/slab.h> |
16 | #include <linux/err.h> |
17 | #include <linux/assoc_array_priv.h> |
18 | |
19 | /* |
20 | * Iterate over an associative array. The caller must hold the RCU read lock |
21 | * or better. |
22 | */ |
23 | static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root, |
24 | const struct assoc_array_ptr *stop, |
25 | int (*iterator)(const void *leaf, |
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 | |
37 | begin_node: |
38 | if (assoc_array_ptr_is_shortcut(cursor)) { |
39 | /* Descend through a shortcut */ |
40 | shortcut = assoc_array_ptr_to_shortcut(cursor); |
41 | smp_read_barrier_depends(); |
42 | cursor = ACCESS_ONCE(shortcut->next_node); |
43 | } |
44 | |
45 | node = assoc_array_ptr_to_node(cursor); |
46 | smp_read_barrier_depends(); |
47 | slot = 0; |
48 | |
49 | /* We perform two passes of each node. |
50 | * |
51 | * The first pass does all the leaves in this node. This means we |
52 | * don't miss any leaves if the node is split up by insertion whilst |
53 | * we're iterating over the branches rooted here (we may, however, see |
54 | * some leaves twice). |
55 | */ |
56 | has_meta = 0; |
57 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
58 | ptr = ACCESS_ONCE(node->slots[slot]); |
59 | has_meta |= (unsigned long)ptr; |
60 | if (ptr && assoc_array_ptr_is_leaf(ptr)) { |
61 | /* We need a barrier between the read of the pointer |
62 | * and dereferencing the pointer - but only if we are |
63 | * actually going to dereference it. |
64 | */ |
65 | smp_read_barrier_depends(); |
66 | |
67 | /* Invoke the callback */ |
68 | ret = iterator(assoc_array_ptr_to_leaf(ptr), |
69 | iterator_data); |
70 | if (ret) |
71 | return ret; |
72 | } |
73 | } |
74 | |
75 | /* The second pass attends to all the metadata pointers. If we follow |
76 | * one of these we may find that we don't come back here, but rather go |
77 | * back to a replacement node with the leaves in a different layout. |
78 | * |
79 | * We are guaranteed to make progress, however, as the slot number for |
80 | * a particular portion of the key space cannot change - and we |
81 | * continue at the back pointer + 1. |
82 | */ |
83 | if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE)) |
84 | goto finished_node; |
85 | slot = 0; |
86 | |
87 | continue_node: |
88 | node = assoc_array_ptr_to_node(cursor); |
89 | smp_read_barrier_depends(); |
90 | |
91 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
92 | ptr = ACCESS_ONCE(node->slots[slot]); |
93 | if (assoc_array_ptr_is_meta(ptr)) { |
94 | cursor = ptr; |
95 | goto begin_node; |
96 | } |
97 | } |
98 | |
99 | finished_node: |
100 | /* Move up to the parent (may need to skip back over a shortcut) */ |
101 | parent = ACCESS_ONCE(node->back_pointer); |
102 | slot = node->parent_slot; |
103 | if (parent == stop) |
104 | return 0; |
105 | |
106 | if (assoc_array_ptr_is_shortcut(parent)) { |
107 | shortcut = assoc_array_ptr_to_shortcut(parent); |
108 | smp_read_barrier_depends(); |
109 | cursor = parent; |
110 | parent = ACCESS_ONCE(shortcut->back_pointer); |
111 | slot = shortcut->parent_slot; |
112 | if (parent == stop) |
113 | return 0; |
114 | } |
115 | |
116 | /* Ascend to next slot in parent node */ |
117 | cursor = parent; |
118 | slot++; |
119 | goto continue_node; |
120 | } |
121 | |
122 | /** |
123 | * assoc_array_iterate - Pass all objects in the array to a callback |
124 | * @array: The array to iterate over. |
125 | * @iterator: The callback function. |
126 | * @iterator_data: Private data for the callback function. |
127 | * |
128 | * Iterate over all the objects in an associative array. Each one will be |
129 | * presented to the iterator function. |
130 | * |
131 | * If the array is being modified concurrently with the iteration then it is |
132 | * possible that some objects in the array will be passed to the iterator |
133 | * callback more than once - though every object should be passed at least |
134 | * once. If this is undesirable then the caller must lock against modification |
135 | * for the duration of this function. |
136 | * |
137 | * The function will return 0 if no objects were in the array or else it will |
138 | * return the result of the last iterator function called. Iteration stops |
139 | * immediately if any call to the iteration function results in a non-zero |
140 | * return. |
141 | * |
142 | * The caller should hold the RCU read lock or better if concurrent |
143 | * modification is possible. |
144 | */ |
145 | int assoc_array_iterate(const struct assoc_array *array, |
146 | int (*iterator)(const void *object, |
147 | void *iterator_data), |
148 | void *iterator_data) |
149 | { |
150 | struct assoc_array_ptr *root = ACCESS_ONCE(array->root); |
151 | |
152 | if (!root) |
153 | return 0; |
154 | return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data); |
155 | } |
156 | |
157 | enum assoc_array_walk_status { |
158 | assoc_array_walk_tree_empty, |
159 | assoc_array_walk_found_terminal_node, |
160 | assoc_array_walk_found_wrong_shortcut, |
161 | }; |
162 | |
163 | struct 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 | */ |
181 | static enum assoc_array_walk_status |
182 | assoc_array_walk(const struct assoc_array *array, |
183 | const struct assoc_array_ops *ops, |
184 | const void *index_key, |
185 | struct assoc_array_walk_result *result) |
186 | { |
187 | struct assoc_array_shortcut *shortcut; |
188 | struct assoc_array_node *node; |
189 | struct assoc_array_ptr *cursor, *ptr; |
190 | unsigned long sc_segments, dissimilarity; |
191 | unsigned long segments; |
192 | int level, sc_level, next_sc_level; |
193 | int slot; |
194 | |
195 | pr_devel("-->%s()\n", __func__); |
196 | |
197 | cursor = ACCESS_ONCE(array->root); |
198 | if (!cursor) |
199 | return assoc_array_walk_tree_empty; |
200 | |
201 | level = 0; |
202 | |
203 | /* Use segments from the key for the new leaf to navigate through the |
204 | * internal tree, skipping through nodes and shortcuts that are on |
205 | * route to the destination. Eventually we'll come to a slot that is |
206 | * either empty or contains a leaf at which point we've found a node in |
207 | * which the leaf we're looking for might be found or into which it |
208 | * should be inserted. |
209 | */ |
210 | jumped: |
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 | |
217 | consider_node: |
218 | node = assoc_array_ptr_to_node(cursor); |
219 | smp_read_barrier_depends(); |
220 | |
221 | slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK); |
222 | slot &= ASSOC_ARRAY_FAN_MASK; |
223 | ptr = ACCESS_ONCE(node->slots[slot]); |
224 | |
225 | pr_devel("consider slot %x [ix=%d type=%lu]\n", |
226 | slot, level, (unsigned long)ptr & 3); |
227 | |
228 | if (!assoc_array_ptr_is_meta(ptr)) { |
229 | /* The node doesn't have a node/shortcut pointer in the slot |
230 | * corresponding to the index key that we have to follow. |
231 | */ |
232 | result->terminal_node.node = node; |
233 | result->terminal_node.level = level; |
234 | result->terminal_node.slot = slot; |
235 | pr_devel("<--%s() = terminal_node\n", __func__); |
236 | return assoc_array_walk_found_terminal_node; |
237 | } |
238 | |
239 | if (assoc_array_ptr_is_node(ptr)) { |
240 | /* There is a pointer to a node in the slot corresponding to |
241 | * this index key segment, so we need to follow it. |
242 | */ |
243 | cursor = ptr; |
244 | level += ASSOC_ARRAY_LEVEL_STEP; |
245 | if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) |
246 | goto consider_node; |
247 | goto jumped; |
248 | } |
249 | |
250 | /* There is a shortcut in the slot corresponding to the index key |
251 | * segment. We follow the shortcut if its partial index key matches |
252 | * this leaf's. Otherwise we need to split the shortcut. |
253 | */ |
254 | cursor = ptr; |
255 | follow_shortcut: |
256 | shortcut = assoc_array_ptr_to_shortcut(cursor); |
257 | smp_read_barrier_depends(); |
258 | pr_devel("shortcut to %d\n", shortcut->skip_to_level); |
259 | sc_level = level + ASSOC_ARRAY_LEVEL_STEP; |
260 | BUG_ON(sc_level > shortcut->skip_to_level); |
261 | |
262 | do { |
263 | /* Check the leaf against the shortcut's index key a word at a |
264 | * time, trimming the final word (the shortcut stores the index |
265 | * key completely from the root to the shortcut's target). |
266 | */ |
267 | if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0) |
268 | segments = ops->get_key_chunk(index_key, sc_level); |
269 | |
270 | sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT]; |
271 | dissimilarity = segments ^ sc_segments; |
272 | |
273 | if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) { |
274 | /* Trim segments that are beyond the shortcut */ |
275 | int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
276 | dissimilarity &= ~(ULONG_MAX << shift); |
277 | next_sc_level = shortcut->skip_to_level; |
278 | } else { |
279 | next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE; |
280 | next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
281 | } |
282 | |
283 | if (dissimilarity != 0) { |
284 | /* This shortcut points elsewhere */ |
285 | result->wrong_shortcut.shortcut = shortcut; |
286 | result->wrong_shortcut.level = level; |
287 | result->wrong_shortcut.sc_level = sc_level; |
288 | result->wrong_shortcut.sc_segments = sc_segments; |
289 | result->wrong_shortcut.dissimilarity = dissimilarity; |
290 | return assoc_array_walk_found_wrong_shortcut; |
291 | } |
292 | |
293 | sc_level = next_sc_level; |
294 | } while (sc_level < shortcut->skip_to_level); |
295 | |
296 | /* The shortcut matches the leaf's index to this point. */ |
297 | cursor = ACCESS_ONCE(shortcut->next_node); |
298 | if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) { |
299 | level = sc_level; |
300 | goto jumped; |
301 | } else { |
302 | level = sc_level; |
303 | goto consider_node; |
304 | } |
305 | } |
306 | |
307 | /** |
308 | * assoc_array_find - Find an object by index key |
309 | * @array: The associative array to search. |
310 | * @ops: The operations to use. |
311 | * @index_key: The key to the object. |
312 | * |
313 | * Find an object in an associative array by walking through the internal tree |
314 | * to the node that should contain the object and then searching the leaves |
315 | * there. NULL is returned if the requested object was not found in the array. |
316 | * |
317 | * The caller must hold the RCU read lock or better. |
318 | */ |
319 | void *assoc_array_find(const struct assoc_array *array, |
320 | const struct assoc_array_ops *ops, |
321 | const void *index_key) |
322 | { |
323 | struct assoc_array_walk_result result; |
324 | const struct assoc_array_node *node; |
325 | const struct assoc_array_ptr *ptr; |
326 | const void *leaf; |
327 | int slot; |
328 | |
329 | if (assoc_array_walk(array, ops, index_key, &result) != |
330 | assoc_array_walk_found_terminal_node) |
331 | return NULL; |
332 | |
333 | node = result.terminal_node.node; |
334 | smp_read_barrier_depends(); |
335 | |
336 | /* If the target key is available to us, it's has to be pointed to by |
337 | * the terminal node. |
338 | */ |
339 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
340 | ptr = ACCESS_ONCE(node->slots[slot]); |
341 | if (ptr && assoc_array_ptr_is_leaf(ptr)) { |
342 | /* We need a barrier between the read of the pointer |
343 | * and dereferencing the pointer - but only if we are |
344 | * actually going to dereference it. |
345 | */ |
346 | leaf = assoc_array_ptr_to_leaf(ptr); |
347 | smp_read_barrier_depends(); |
348 | if (ops->compare_object(leaf, index_key)) |
349 | return (void *)leaf; |
350 | } |
351 | } |
352 | |
353 | return NULL; |
354 | } |
355 | |
356 | /* |
357 | * Destructively iterate over an associative array. The caller must prevent |
358 | * other simultaneous accesses. |
359 | */ |
360 | static 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 | |
376 | move_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 | |
396 | continue_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 | */ |
458 | void 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 | */ |
468 | static 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 | */ |
491 | static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit, |
492 | const struct assoc_array_ops *ops, |
493 | const void *index_key, |
494 | struct assoc_array_walk_result *result) |
495 | { |
496 | struct assoc_array_shortcut *shortcut, *new_s0; |
497 | struct assoc_array_node *node, *new_n0, *new_n1, *side; |
498 | struct assoc_array_ptr *ptr; |
499 | unsigned long dissimilarity, base_seg, blank; |
500 | size_t keylen; |
501 | bool have_meta; |
502 | int level, diff; |
503 | int slot, next_slot, free_slot, i, j; |
504 | |
505 | node = result->terminal_node.node; |
506 | level = result->terminal_node.level; |
507 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot; |
508 | |
509 | pr_devel("-->%s()\n", __func__); |
510 | |
511 | /* We arrived at a node which doesn't have an onward node or shortcut |
512 | * pointer that we have to follow. This means that (a) the leaf we |
513 | * want must go here (either by insertion or replacement) or (b) we |
514 | * need to split this node and insert in one of the fragments. |
515 | */ |
516 | free_slot = -1; |
517 | |
518 | /* Firstly, we have to check the leaves in this node to see if there's |
519 | * a matching one we should replace in place. |
520 | */ |
521 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
522 | ptr = node->slots[i]; |
523 | if (!ptr) { |
524 | free_slot = i; |
525 | continue; |
526 | } |
527 | if (assoc_array_ptr_is_leaf(ptr) && |
528 | ops->compare_object(assoc_array_ptr_to_leaf(ptr), |
529 | index_key)) { |
530 | pr_devel("replace in slot %d\n", i); |
531 | edit->leaf_p = &node->slots[i]; |
532 | edit->dead_leaf = node->slots[i]; |
533 | pr_devel("<--%s() = ok [replace]\n", __func__); |
534 | return true; |
535 | } |
536 | } |
537 | |
538 | /* If there is a free slot in this node then we can just insert the |
539 | * leaf here. |
540 | */ |
541 | if (free_slot >= 0) { |
542 | pr_devel("insert in free slot %d\n", free_slot); |
543 | edit->leaf_p = &node->slots[free_slot]; |
544 | edit->adjust_count_on = node; |
545 | pr_devel("<--%s() = ok [insert]\n", __func__); |
546 | return true; |
547 | } |
548 | |
549 | /* The node has no spare slots - so we're either going to have to split |
550 | * it or insert another node before it. |
551 | * |
552 | * Whatever, we're going to need at least two new nodes - so allocate |
553 | * those now. We may also need a new shortcut, but we deal with that |
554 | * when we need it. |
555 | */ |
556 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
557 | if (!new_n0) |
558 | return false; |
559 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); |
560 | new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
561 | if (!new_n1) |
562 | return false; |
563 | edit->new_meta[1] = assoc_array_node_to_ptr(new_n1); |
564 | |
565 | /* We need to find out how similar the leaves are. */ |
566 | pr_devel("no spare slots\n"); |
567 | have_meta = false; |
568 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
569 | ptr = node->slots[i]; |
570 | if (assoc_array_ptr_is_meta(ptr)) { |
571 | edit->segment_cache[i] = 0xff; |
572 | have_meta = true; |
573 | continue; |
574 | } |
575 | base_seg = ops->get_object_key_chunk( |
576 | assoc_array_ptr_to_leaf(ptr), level); |
577 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
578 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; |
579 | } |
580 | |
581 | if (have_meta) { |
582 | pr_devel("have meta\n"); |
583 | goto split_node; |
584 | } |
585 | |
586 | /* The node contains only leaves */ |
587 | dissimilarity = 0; |
588 | base_seg = edit->segment_cache[0]; |
589 | for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++) |
590 | dissimilarity |= edit->segment_cache[i] ^ base_seg; |
591 | |
592 | pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity); |
593 | |
594 | if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) { |
595 | /* The old leaves all cluster in the same slot. We will need |
596 | * to insert a shortcut if the new node wants to cluster with them. |
597 | */ |
598 | if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0) |
599 | goto all_leaves_cluster_together; |
600 | |
601 | /* Otherwise 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. |
608 | */ |
609 | pr_devel("present leaves cluster but not new leaf\n"); |
610 | } |
611 | |
612 | split_node: |
613 | pr_devel("split node\n"); |
614 | |
615 | /* 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. |
622 | * |
623 | * We need to expel at least two leaves out of a set consisting of the |
624 | * 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. |
626 | * |
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 | |
636 | do_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 | } |
655 | found_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 | |
730 | all_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++) { |
748 | int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]), |
749 | index_key); |
750 | 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 | if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) { |
785 | blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); |
786 | pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); |
787 | new_s0->index_key[keylen - 1] &= ~blank; |
788 | } |
789 | |
790 | /* This now reduces to a node splitting exercise for which we'll need |
791 | * to regenerate the disparity table. |
792 | */ |
793 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
794 | ptr = node->slots[i]; |
795 | base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr), |
796 | level); |
797 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
798 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; |
799 | } |
800 | |
801 | base_seg = ops->get_key_chunk(index_key, level); |
802 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
803 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK; |
804 | goto do_split_node; |
805 | } |
806 | |
807 | /* |
808 | * Handle insertion into the middle of a shortcut. |
809 | */ |
810 | static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit, |
811 | const struct assoc_array_ops *ops, |
812 | struct assoc_array_walk_result *result) |
813 | { |
814 | struct assoc_array_shortcut *shortcut, *new_s0, *new_s1; |
815 | struct assoc_array_node *node, *new_n0, *side; |
816 | unsigned long sc_segments, dissimilarity, blank; |
817 | size_t keylen; |
818 | int level, sc_level, diff; |
819 | int sc_slot; |
820 | |
821 | shortcut = result->wrong_shortcut.shortcut; |
822 | level = result->wrong_shortcut.level; |
823 | sc_level = result->wrong_shortcut.sc_level; |
824 | sc_segments = result->wrong_shortcut.sc_segments; |
825 | dissimilarity = result->wrong_shortcut.dissimilarity; |
826 | |
827 | pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n", |
828 | __func__, level, dissimilarity, sc_level); |
829 | |
830 | /* We need to split a shortcut and insert a node between the two |
831 | * pieces. Zero-length pieces will be dispensed with entirely. |
832 | * |
833 | * First of all, we need to find out in which level the first |
834 | * difference was. |
835 | */ |
836 | diff = __ffs(dissimilarity); |
837 | diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK; |
838 | diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK; |
839 | pr_devel("diff=%d\n", diff); |
840 | |
841 | if (!shortcut->back_pointer) { |
842 | edit->set[0].ptr = &edit->array->root; |
843 | } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) { |
844 | node = assoc_array_ptr_to_node(shortcut->back_pointer); |
845 | edit->set[0].ptr = &node->slots[shortcut->parent_slot]; |
846 | } else { |
847 | BUG(); |
848 | } |
849 | |
850 | edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut); |
851 | |
852 | /* Create a new node now since we're going to need it anyway */ |
853 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
854 | if (!new_n0) |
855 | return false; |
856 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); |
857 | edit->adjust_count_on = new_n0; |
858 | |
859 | /* Insert a new shortcut before the new node if this segment isn't of |
860 | * zero length - otherwise we just connect the new node directly to the |
861 | * parent. |
862 | */ |
863 | level += ASSOC_ARRAY_LEVEL_STEP; |
864 | if (diff > level) { |
865 | pr_devel("pre-shortcut %d...%d\n", level, diff); |
866 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
867 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
868 | |
869 | new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + |
870 | keylen * sizeof(unsigned long), GFP_KERNEL); |
871 | if (!new_s0) |
872 | return false; |
873 | edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0); |
874 | edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); |
875 | new_s0->back_pointer = shortcut->back_pointer; |
876 | new_s0->parent_slot = shortcut->parent_slot; |
877 | new_s0->next_node = assoc_array_node_to_ptr(new_n0); |
878 | new_s0->skip_to_level = diff; |
879 | |
880 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); |
881 | new_n0->parent_slot = 0; |
882 | |
883 | memcpy(new_s0->index_key, shortcut->index_key, |
884 | keylen * sizeof(unsigned long)); |
885 | |
886 | blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); |
887 | pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank); |
888 | new_s0->index_key[keylen - 1] &= ~blank; |
889 | } else { |
890 | pr_devel("no pre-shortcut\n"); |
891 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); |
892 | new_n0->back_pointer = shortcut->back_pointer; |
893 | new_n0->parent_slot = shortcut->parent_slot; |
894 | } |
895 | |
896 | side = assoc_array_ptr_to_node(shortcut->next_node); |
897 | new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch; |
898 | |
899 | /* We need to know which slot in the new node is going to take a |
900 | * metadata pointer. |
901 | */ |
902 | sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); |
903 | sc_slot &= ASSOC_ARRAY_FAN_MASK; |
904 | |
905 | pr_devel("new slot %lx >> %d -> %d\n", |
906 | sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot); |
907 | |
908 | /* Determine whether we need to follow the new node with a replacement |
909 | * for the current shortcut. We could in theory reuse the current |
910 | * shortcut if its parent slot number doesn't change - but that's a |
911 | * 1-in-16 chance so not worth expending the code upon. |
912 | */ |
913 | level = diff + ASSOC_ARRAY_LEVEL_STEP; |
914 | if (level < shortcut->skip_to_level) { |
915 | pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level); |
916 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
917 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
918 | |
919 | new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) + |
920 | keylen * sizeof(unsigned long), GFP_KERNEL); |
921 | if (!new_s1) |
922 | return false; |
923 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1); |
924 | |
925 | new_s1->back_pointer = assoc_array_node_to_ptr(new_n0); |
926 | new_s1->parent_slot = sc_slot; |
927 | new_s1->next_node = shortcut->next_node; |
928 | new_s1->skip_to_level = shortcut->skip_to_level; |
929 | |
930 | new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1); |
931 | |
932 | memcpy(new_s1->index_key, shortcut->index_key, |
933 | keylen * sizeof(unsigned long)); |
934 | |
935 | edit->set[1].ptr = &side->back_pointer; |
936 | edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1); |
937 | } else { |
938 | pr_devel("no post-shortcut\n"); |
939 | |
940 | /* We don't have to replace the pointed-to node as long as we |
941 | * use memory barriers to make sure the parent slot number is |
942 | * changed before the back pointer (the parent slot number is |
943 | * irrelevant to the old parent shortcut). |
944 | */ |
945 | new_n0->slots[sc_slot] = shortcut->next_node; |
946 | edit->set_parent_slot[0].p = &side->parent_slot; |
947 | edit->set_parent_slot[0].to = sc_slot; |
948 | edit->set[1].ptr = &side->back_pointer; |
949 | edit->set[1].to = assoc_array_node_to_ptr(new_n0); |
950 | } |
951 | |
952 | /* Install the new leaf in a spare slot in the new node. */ |
953 | if (sc_slot == 0) |
954 | edit->leaf_p = &new_n0->slots[1]; |
955 | else |
956 | edit->leaf_p = &new_n0->slots[0]; |
957 | |
958 | pr_devel("<--%s() = ok [split shortcut]\n", __func__); |
959 | return edit; |
960 | } |
961 | |
962 | /** |
963 | * assoc_array_insert - Script insertion of an object into an associative array |
964 | * @array: The array to insert into. |
965 | * @ops: The operations to use. |
966 | * @index_key: The key to insert at. |
967 | * @object: The object to insert. |
968 | * |
969 | * Precalculate and preallocate a script for the insertion or replacement of an |
970 | * object in an associative array. This results in an edit script that can |
971 | * either be applied or cancelled. |
972 | * |
973 | * The function returns a pointer to an edit script or -ENOMEM. |
974 | * |
975 | * The caller should lock against other modifications and must continue to hold |
976 | * the lock until assoc_array_apply_edit() has been called. |
977 | * |
978 | * Accesses to the tree may take place concurrently with this function, |
979 | * provided they hold the RCU read lock. |
980 | */ |
981 | struct assoc_array_edit *assoc_array_insert(struct assoc_array *array, |
982 | const struct assoc_array_ops *ops, |
983 | const void *index_key, |
984 | void *object) |
985 | { |
986 | struct assoc_array_walk_result result; |
987 | struct assoc_array_edit *edit; |
988 | |
989 | pr_devel("-->%s()\n", __func__); |
990 | |
991 | /* The leaf pointer we're given must not have the bottom bit set as we |
992 | * use those for type-marking the pointer. NULL pointers are also not |
993 | * allowed as they indicate an empty slot but we have to allow them |
994 | * here as they can be updated later. |
995 | */ |
996 | BUG_ON(assoc_array_ptr_is_meta(object)); |
997 | |
998 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
999 | if (!edit) |
1000 | return ERR_PTR(-ENOMEM); |
1001 | edit->array = array; |
1002 | edit->ops = ops; |
1003 | edit->leaf = assoc_array_leaf_to_ptr(object); |
1004 | edit->adjust_count_by = 1; |
1005 | |
1006 | switch (assoc_array_walk(array, ops, index_key, &result)) { |
1007 | case assoc_array_walk_tree_empty: |
1008 | /* Allocate a root node if there isn't one yet */ |
1009 | if (!assoc_array_insert_in_empty_tree(edit)) |
1010 | goto enomem; |
1011 | return edit; |
1012 | |
1013 | case assoc_array_walk_found_terminal_node: |
1014 | /* We found a node that doesn't have a node/shortcut pointer in |
1015 | * the slot corresponding to the index key that we have to |
1016 | * follow. |
1017 | */ |
1018 | if (!assoc_array_insert_into_terminal_node(edit, ops, index_key, |
1019 | &result)) |
1020 | goto enomem; |
1021 | return edit; |
1022 | |
1023 | case assoc_array_walk_found_wrong_shortcut: |
1024 | /* We found a shortcut that didn't match our key in a slot we |
1025 | * needed to follow. |
1026 | */ |
1027 | if (!assoc_array_insert_mid_shortcut(edit, ops, &result)) |
1028 | goto enomem; |
1029 | return edit; |
1030 | } |
1031 | |
1032 | enomem: |
1033 | /* Clean up after an out of memory error */ |
1034 | pr_devel("enomem\n"); |
1035 | assoc_array_cancel_edit(edit); |
1036 | return ERR_PTR(-ENOMEM); |
1037 | } |
1038 | |
1039 | /** |
1040 | * assoc_array_insert_set_object - Set the new object pointer in an edit script |
1041 | * @edit: The edit script to modify. |
1042 | * @object: The object pointer to set. |
1043 | * |
1044 | * Change the object to be inserted in an edit script. The object pointed to |
1045 | * by the old object is not freed. This must be done prior to applying the |
1046 | * script. |
1047 | */ |
1048 | void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object) |
1049 | { |
1050 | BUG_ON(!object); |
1051 | edit->leaf = assoc_array_leaf_to_ptr(object); |
1052 | } |
1053 | |
1054 | struct assoc_array_delete_collapse_context { |
1055 | struct assoc_array_node *node; |
1056 | const void *skip_leaf; |
1057 | int slot; |
1058 | }; |
1059 | |
1060 | /* |
1061 | * Subtree collapse to node iterator. |
1062 | */ |
1063 | static int assoc_array_delete_collapse_iterator(const void *leaf, |
1064 | void *iterator_data) |
1065 | { |
1066 | struct assoc_array_delete_collapse_context *collapse = iterator_data; |
1067 | |
1068 | if (leaf == collapse->skip_leaf) |
1069 | return 0; |
1070 | |
1071 | BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT); |
1072 | |
1073 | collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf); |
1074 | return 0; |
1075 | } |
1076 | |
1077 | /** |
1078 | * assoc_array_delete - Script deletion of an object from an associative array |
1079 | * @array: The array to search. |
1080 | * @ops: The operations to use. |
1081 | * @index_key: The key to the object. |
1082 | * |
1083 | * Precalculate and preallocate a script for the deletion of an object from an |
1084 | * associative array. This results in an edit script that can either be |
1085 | * applied or cancelled. |
1086 | * |
1087 | * The function returns a pointer to an edit script if the object was found, |
1088 | * NULL if the object was not found or -ENOMEM. |
1089 | * |
1090 | * The caller should lock against other modifications and must continue to hold |
1091 | * the lock until assoc_array_apply_edit() has been called. |
1092 | * |
1093 | * Accesses to the tree may take place concurrently with this function, |
1094 | * provided they hold the RCU read lock. |
1095 | */ |
1096 | struct assoc_array_edit *assoc_array_delete(struct assoc_array *array, |
1097 | const struct assoc_array_ops *ops, |
1098 | const void *index_key) |
1099 | { |
1100 | struct assoc_array_delete_collapse_context collapse; |
1101 | struct assoc_array_walk_result result; |
1102 | struct assoc_array_node *node, *new_n0; |
1103 | struct assoc_array_edit *edit; |
1104 | struct assoc_array_ptr *ptr; |
1105 | bool has_meta; |
1106 | int slot, i; |
1107 | |
1108 | pr_devel("-->%s()\n", __func__); |
1109 | |
1110 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
1111 | if (!edit) |
1112 | return ERR_PTR(-ENOMEM); |
1113 | edit->array = array; |
1114 | edit->ops = ops; |
1115 | edit->adjust_count_by = -1; |
1116 | |
1117 | switch (assoc_array_walk(array, ops, index_key, &result)) { |
1118 | case assoc_array_walk_found_terminal_node: |
1119 | /* We found a node that should contain the leaf we've been |
1120 | * asked to remove - *if* it's in the tree. |
1121 | */ |
1122 | pr_devel("terminal_node\n"); |
1123 | node = result.terminal_node.node; |
1124 | |
1125 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1126 | ptr = node->slots[slot]; |
1127 | if (ptr && |
1128 | assoc_array_ptr_is_leaf(ptr) && |
1129 | ops->compare_object(assoc_array_ptr_to_leaf(ptr), |
1130 | index_key)) |
1131 | goto found_leaf; |
1132 | } |
1133 | case assoc_array_walk_tree_empty: |
1134 | case assoc_array_walk_found_wrong_shortcut: |
1135 | default: |
1136 | assoc_array_cancel_edit(edit); |
1137 | pr_devel("not found\n"); |
1138 | return NULL; |
1139 | } |
1140 | |
1141 | found_leaf: |
1142 | BUG_ON(array->nr_leaves_on_tree <= 0); |
1143 | |
1144 | /* In the simplest form of deletion we just clear the slot and release |
1145 | * the leaf after a suitable interval. |
1146 | */ |
1147 | edit->dead_leaf = node->slots[slot]; |
1148 | edit->set[0].ptr = &node->slots[slot]; |
1149 | edit->set[0].to = NULL; |
1150 | edit->adjust_count_on = node; |
1151 | |
1152 | /* If that concludes erasure of the last leaf, then delete the entire |
1153 | * internal array. |
1154 | */ |
1155 | if (array->nr_leaves_on_tree == 1) { |
1156 | edit->set[1].ptr = &array->root; |
1157 | edit->set[1].to = NULL; |
1158 | edit->adjust_count_on = NULL; |
1159 | edit->excised_subtree = array->root; |
1160 | pr_devel("all gone\n"); |
1161 | return edit; |
1162 | } |
1163 | |
1164 | /* However, we'd also like to clear up some metadata blocks if we |
1165 | * possibly can. |
1166 | * |
1167 | * We go for a simple algorithm of: if this node has FAN_OUT or fewer |
1168 | * leaves in it, then attempt to collapse it - and attempt to |
1169 | * recursively collapse up the tree. |
1170 | * |
1171 | * We could also try and collapse in partially filled subtrees to take |
1172 | * up space in this node. |
1173 | */ |
1174 | if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { |
1175 | struct assoc_array_node *parent, *grandparent; |
1176 | struct assoc_array_ptr *ptr; |
1177 | |
1178 | /* First of all, we need to know if this node has metadata so |
1179 | * that we don't try collapsing if all the leaves are already |
1180 | * here. |
1181 | */ |
1182 | has_meta = false; |
1183 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
1184 | ptr = node->slots[i]; |
1185 | if (assoc_array_ptr_is_meta(ptr)) { |
1186 | has_meta = true; |
1187 | break; |
1188 | } |
1189 | } |
1190 | |
1191 | pr_devel("leaves: %ld [m=%d]\n", |
1192 | node->nr_leaves_on_branch - 1, has_meta); |
1193 | |
1194 | /* Look further up the tree to see if we can collapse this node |
1195 | * into a more proximal node too. |
1196 | */ |
1197 | parent = node; |
1198 | collapse_up: |
1199 | pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch); |
1200 | |
1201 | ptr = parent->back_pointer; |
1202 | if (!ptr) |
1203 | goto do_collapse; |
1204 | if (assoc_array_ptr_is_shortcut(ptr)) { |
1205 | struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr); |
1206 | ptr = s->back_pointer; |
1207 | if (!ptr) |
1208 | goto do_collapse; |
1209 | } |
1210 | |
1211 | grandparent = assoc_array_ptr_to_node(ptr); |
1212 | if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { |
1213 | parent = grandparent; |
1214 | goto collapse_up; |
1215 | } |
1216 | |
1217 | do_collapse: |
1218 | /* There's no point collapsing if the original node has no meta |
1219 | * pointers to discard and if we didn't merge into one of that |
1220 | * node's ancestry. |
1221 | */ |
1222 | if (has_meta || parent != node) { |
1223 | node = parent; |
1224 | |
1225 | /* Create a new node to collapse into */ |
1226 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
1227 | if (!new_n0) |
1228 | goto enomem; |
1229 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); |
1230 | |
1231 | new_n0->back_pointer = node->back_pointer; |
1232 | new_n0->parent_slot = node->parent_slot; |
1233 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; |
1234 | edit->adjust_count_on = new_n0; |
1235 | |
1236 | collapse.node = new_n0; |
1237 | collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf); |
1238 | collapse.slot = 0; |
1239 | assoc_array_subtree_iterate(assoc_array_node_to_ptr(node), |
1240 | node->back_pointer, |
1241 | assoc_array_delete_collapse_iterator, |
1242 | &collapse); |
1243 | pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch); |
1244 | BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1); |
1245 | |
1246 | if (!node->back_pointer) { |
1247 | edit->set[1].ptr = &array->root; |
1248 | } else if (assoc_array_ptr_is_leaf(node->back_pointer)) { |
1249 | BUG(); |
1250 | } else if (assoc_array_ptr_is_node(node->back_pointer)) { |
1251 | struct assoc_array_node *p = |
1252 | assoc_array_ptr_to_node(node->back_pointer); |
1253 | edit->set[1].ptr = &p->slots[node->parent_slot]; |
1254 | } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) { |
1255 | struct assoc_array_shortcut *s = |
1256 | assoc_array_ptr_to_shortcut(node->back_pointer); |
1257 | edit->set[1].ptr = &s->next_node; |
1258 | } |
1259 | edit->set[1].to = assoc_array_node_to_ptr(new_n0); |
1260 | edit->excised_subtree = assoc_array_node_to_ptr(node); |
1261 | } |
1262 | } |
1263 | |
1264 | return edit; |
1265 | |
1266 | enomem: |
1267 | /* Clean up after an out of memory error */ |
1268 | pr_devel("enomem\n"); |
1269 | assoc_array_cancel_edit(edit); |
1270 | return ERR_PTR(-ENOMEM); |
1271 | } |
1272 | |
1273 | /** |
1274 | * assoc_array_clear - Script deletion of all objects from an associative array |
1275 | * @array: The array to clear. |
1276 | * @ops: The operations to use. |
1277 | * |
1278 | * Precalculate and preallocate a script for the deletion of all the objects |
1279 | * from an associative array. This results in an edit script that can either |
1280 | * be applied or cancelled. |
1281 | * |
1282 | * The function returns a pointer to an edit script if there are objects to be |
1283 | * deleted, NULL if there are no objects in the array or -ENOMEM. |
1284 | * |
1285 | * The caller should lock against other modifications and must continue to hold |
1286 | * the lock until assoc_array_apply_edit() has been called. |
1287 | * |
1288 | * Accesses to the tree may take place concurrently with this function, |
1289 | * provided they hold the RCU read lock. |
1290 | */ |
1291 | struct assoc_array_edit *assoc_array_clear(struct assoc_array *array, |
1292 | const struct assoc_array_ops *ops) |
1293 | { |
1294 | struct assoc_array_edit *edit; |
1295 | |
1296 | pr_devel("-->%s()\n", __func__); |
1297 | |
1298 | if (!array->root) |
1299 | return NULL; |
1300 | |
1301 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
1302 | if (!edit) |
1303 | return ERR_PTR(-ENOMEM); |
1304 | edit->array = array; |
1305 | edit->ops = ops; |
1306 | edit->set[1].ptr = &array->root; |
1307 | edit->set[1].to = NULL; |
1308 | edit->excised_subtree = array->root; |
1309 | edit->ops_for_excised_subtree = ops; |
1310 | pr_devel("all gone\n"); |
1311 | return edit; |
1312 | } |
1313 | |
1314 | /* |
1315 | * Handle the deferred destruction after an applied edit. |
1316 | */ |
1317 | static void assoc_array_rcu_cleanup(struct rcu_head *head) |
1318 | { |
1319 | struct assoc_array_edit *edit = |
1320 | container_of(head, struct assoc_array_edit, rcu); |
1321 | int i; |
1322 | |
1323 | pr_devel("-->%s()\n", __func__); |
1324 | |
1325 | if (edit->dead_leaf) |
1326 | edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf)); |
1327 | for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++) |
1328 | if (edit->excised_meta[i]) |
1329 | kfree(assoc_array_ptr_to_node(edit->excised_meta[i])); |
1330 | |
1331 | if (edit->excised_subtree) { |
1332 | BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree)); |
1333 | if (assoc_array_ptr_is_node(edit->excised_subtree)) { |
1334 | struct assoc_array_node *n = |
1335 | assoc_array_ptr_to_node(edit->excised_subtree); |
1336 | n->back_pointer = NULL; |
1337 | } else { |
1338 | struct assoc_array_shortcut *s = |
1339 | assoc_array_ptr_to_shortcut(edit->excised_subtree); |
1340 | s->back_pointer = NULL; |
1341 | } |
1342 | assoc_array_destroy_subtree(edit->excised_subtree, |
1343 | edit->ops_for_excised_subtree); |
1344 | } |
1345 | |
1346 | kfree(edit); |
1347 | } |
1348 | |
1349 | /** |
1350 | * assoc_array_apply_edit - Apply an edit script to an associative array |
1351 | * @edit: The script to apply. |
1352 | * |
1353 | * Apply an edit script to an associative array to effect an insertion, |
1354 | * deletion or clearance. As the edit script includes preallocated memory, |
1355 | * this is guaranteed not to fail. |
1356 | * |
1357 | * The edit script, dead objects and dead metadata will be scheduled for |
1358 | * destruction after an RCU grace period to permit those doing read-only |
1359 | * accesses on the array to continue to do so under the RCU read lock whilst |
1360 | * the edit is taking place. |
1361 | */ |
1362 | void assoc_array_apply_edit(struct assoc_array_edit *edit) |
1363 | { |
1364 | struct assoc_array_shortcut *shortcut; |
1365 | struct assoc_array_node *node; |
1366 | struct assoc_array_ptr *ptr; |
1367 | int i; |
1368 | |
1369 | pr_devel("-->%s()\n", __func__); |
1370 | |
1371 | smp_wmb(); |
1372 | if (edit->leaf_p) |
1373 | *edit->leaf_p = edit->leaf; |
1374 | |
1375 | smp_wmb(); |
1376 | for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++) |
1377 | if (edit->set_parent_slot[i].p) |
1378 | *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to; |
1379 | |
1380 | smp_wmb(); |
1381 | for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++) |
1382 | if (edit->set_backpointers[i]) |
1383 | *edit->set_backpointers[i] = edit->set_backpointers_to; |
1384 | |
1385 | smp_wmb(); |
1386 | for (i = 0; i < ARRAY_SIZE(edit->set); i++) |
1387 | if (edit->set[i].ptr) |
1388 | *edit->set[i].ptr = edit->set[i].to; |
1389 | |
1390 | if (edit->array->root == NULL) { |
1391 | edit->array->nr_leaves_on_tree = 0; |
1392 | } else if (edit->adjust_count_on) { |
1393 | node = edit->adjust_count_on; |
1394 | for (;;) { |
1395 | node->nr_leaves_on_branch += edit->adjust_count_by; |
1396 | |
1397 | ptr = node->back_pointer; |
1398 | if (!ptr) |
1399 | break; |
1400 | if (assoc_array_ptr_is_shortcut(ptr)) { |
1401 | shortcut = assoc_array_ptr_to_shortcut(ptr); |
1402 | ptr = shortcut->back_pointer; |
1403 | if (!ptr) |
1404 | break; |
1405 | } |
1406 | BUG_ON(!assoc_array_ptr_is_node(ptr)); |
1407 | node = assoc_array_ptr_to_node(ptr); |
1408 | } |
1409 | |
1410 | edit->array->nr_leaves_on_tree += edit->adjust_count_by; |
1411 | } |
1412 | |
1413 | call_rcu(&edit->rcu, assoc_array_rcu_cleanup); |
1414 | } |
1415 | |
1416 | /** |
1417 | * assoc_array_cancel_edit - Discard an edit script. |
1418 | * @edit: The script to discard. |
1419 | * |
1420 | * Free an edit script and all the preallocated data it holds without making |
1421 | * any changes to the associative array it was intended for. |
1422 | * |
1423 | * NOTE! In the case of an insertion script, this does _not_ release the leaf |
1424 | * that was to be inserted. That is left to the caller. |
1425 | */ |
1426 | void assoc_array_cancel_edit(struct assoc_array_edit *edit) |
1427 | { |
1428 | struct assoc_array_ptr *ptr; |
1429 | int i; |
1430 | |
1431 | pr_devel("-->%s()\n", __func__); |
1432 | |
1433 | /* Clean up after an out of memory error */ |
1434 | for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) { |
1435 | ptr = edit->new_meta[i]; |
1436 | if (ptr) { |
1437 | if (assoc_array_ptr_is_node(ptr)) |
1438 | kfree(assoc_array_ptr_to_node(ptr)); |
1439 | else |
1440 | kfree(assoc_array_ptr_to_shortcut(ptr)); |
1441 | } |
1442 | } |
1443 | kfree(edit); |
1444 | } |
1445 | |
1446 | /** |
1447 | * assoc_array_gc - Garbage collect an associative array. |
1448 | * @array: The array to clean. |
1449 | * @ops: The operations to use. |
1450 | * @iterator: A callback function to pass judgement on each object. |
1451 | * @iterator_data: Private data for the callback function. |
1452 | * |
1453 | * Collect garbage from an associative array and pack down the internal tree to |
1454 | * save memory. |
1455 | * |
1456 | * The iterator function is asked to pass judgement upon each object in the |
1457 | * array. If it returns false, the object is discard and if it returns true, |
1458 | * the object is kept. If it returns true, it must increment the object's |
1459 | * usage count (or whatever it needs to do to retain it) before returning. |
1460 | * |
1461 | * This function returns 0 if successful or -ENOMEM if out of memory. In the |
1462 | * latter case, the array is not changed. |
1463 | * |
1464 | * The caller should lock against other modifications and must continue to hold |
1465 | * the lock until assoc_array_apply_edit() has been called. |
1466 | * |
1467 | * Accesses to the tree may take place concurrently with this function, |
1468 | * provided they hold the RCU read lock. |
1469 | */ |
1470 | int assoc_array_gc(struct assoc_array *array, |
1471 | const struct assoc_array_ops *ops, |
1472 | bool (*iterator)(void *object, void *iterator_data), |
1473 | void *iterator_data) |
1474 | { |
1475 | struct assoc_array_shortcut *shortcut, *new_s; |
1476 | struct assoc_array_node *node, *new_n; |
1477 | struct assoc_array_edit *edit; |
1478 | struct assoc_array_ptr *cursor, *ptr; |
1479 | struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp; |
1480 | unsigned long nr_leaves_on_tree; |
1481 | int keylen, slot, nr_free, next_slot, i; |
1482 | |
1483 | pr_devel("-->%s()\n", __func__); |
1484 | |
1485 | if (!array->root) |
1486 | return 0; |
1487 | |
1488 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
1489 | if (!edit) |
1490 | return -ENOMEM; |
1491 | edit->array = array; |
1492 | edit->ops = ops; |
1493 | edit->ops_for_excised_subtree = ops; |
1494 | edit->set[0].ptr = &array->root; |
1495 | edit->excised_subtree = array->root; |
1496 | |
1497 | new_root = new_parent = NULL; |
1498 | new_ptr_pp = &new_root; |
1499 | cursor = array->root; |
1500 | |
1501 | descend: |
1502 | /* If this point is a shortcut, then we need to duplicate it and |
1503 | * advance the target cursor. |
1504 | */ |
1505 | if (assoc_array_ptr_is_shortcut(cursor)) { |
1506 | shortcut = assoc_array_ptr_to_shortcut(cursor); |
1507 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
1508 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
1509 | new_s = kmalloc(sizeof(struct assoc_array_shortcut) + |
1510 | keylen * sizeof(unsigned long), GFP_KERNEL); |
1511 | if (!new_s) |
1512 | goto enomem; |
1513 | pr_devel("dup shortcut %p -> %p\n", shortcut, new_s); |
1514 | memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) + |
1515 | keylen * sizeof(unsigned long))); |
1516 | new_s->back_pointer = new_parent; |
1517 | new_s->parent_slot = shortcut->parent_slot; |
1518 | *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s); |
1519 | new_ptr_pp = &new_s->next_node; |
1520 | cursor = shortcut->next_node; |
1521 | } |
1522 | |
1523 | /* Duplicate the node at this position */ |
1524 | node = assoc_array_ptr_to_node(cursor); |
1525 | new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
1526 | if (!new_n) |
1527 | goto enomem; |
1528 | pr_devel("dup node %p -> %p\n", node, new_n); |
1529 | new_n->back_pointer = new_parent; |
1530 | new_n->parent_slot = node->parent_slot; |
1531 | *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n); |
1532 | new_ptr_pp = NULL; |
1533 | slot = 0; |
1534 | |
1535 | continue_node: |
1536 | /* Filter across any leaves and gc any subtrees */ |
1537 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1538 | ptr = node->slots[slot]; |
1539 | if (!ptr) |
1540 | continue; |
1541 | |
1542 | if (assoc_array_ptr_is_leaf(ptr)) { |
1543 | if (iterator(assoc_array_ptr_to_leaf(ptr), |
1544 | iterator_data)) |
1545 | /* The iterator will have done any reference |
1546 | * counting on the object for us. |
1547 | */ |
1548 | new_n->slots[slot] = ptr; |
1549 | continue; |
1550 | } |
1551 | |
1552 | new_ptr_pp = &new_n->slots[slot]; |
1553 | cursor = ptr; |
1554 | goto descend; |
1555 | } |
1556 | |
1557 | pr_devel("-- compress node %p --\n", new_n); |
1558 | |
1559 | /* Count up the number of empty slots in this node and work out the |
1560 | * subtree leaf count. |
1561 | */ |
1562 | new_n->nr_leaves_on_branch = 0; |
1563 | nr_free = 0; |
1564 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1565 | ptr = new_n->slots[slot]; |
1566 | if (!ptr) |
1567 | nr_free++; |
1568 | else if (assoc_array_ptr_is_leaf(ptr)) |
1569 | new_n->nr_leaves_on_branch++; |
1570 | } |
1571 | pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch); |
1572 | |
1573 | /* See what we can fold in */ |
1574 | next_slot = 0; |
1575 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1576 | struct assoc_array_shortcut *s; |
1577 | struct assoc_array_node *child; |
1578 | |
1579 | ptr = new_n->slots[slot]; |
1580 | if (!ptr || assoc_array_ptr_is_leaf(ptr)) |
1581 | continue; |
1582 | |
1583 | s = NULL; |
1584 | if (assoc_array_ptr_is_shortcut(ptr)) { |
1585 | s = assoc_array_ptr_to_shortcut(ptr); |
1586 | ptr = s->next_node; |
1587 | } |
1588 | |
1589 | child = assoc_array_ptr_to_node(ptr); |
1590 | new_n->nr_leaves_on_branch += child->nr_leaves_on_branch; |
1591 | |
1592 | if (child->nr_leaves_on_branch <= nr_free + 1) { |
1593 | /* Fold the child node into this one */ |
1594 | pr_devel("[%d] fold node %lu/%d [nx %d]\n", |
1595 | slot, child->nr_leaves_on_branch, nr_free + 1, |
1596 | next_slot); |
1597 | |
1598 | /* We would already have reaped an intervening shortcut |
1599 | * on the way back up the tree. |
1600 | */ |
1601 | BUG_ON(s); |
1602 | |
1603 | new_n->slots[slot] = NULL; |
1604 | nr_free++; |
1605 | if (slot < next_slot) |
1606 | next_slot = slot; |
1607 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
1608 | struct assoc_array_ptr *p = child->slots[i]; |
1609 | if (!p) |
1610 | continue; |
1611 | BUG_ON(assoc_array_ptr_is_meta(p)); |
1612 | while (new_n->slots[next_slot]) |
1613 | next_slot++; |
1614 | BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT); |
1615 | new_n->slots[next_slot++] = p; |
1616 | nr_free--; |
1617 | } |
1618 | kfree(child); |
1619 | } else { |
1620 | pr_devel("[%d] retain node %lu/%d [nx %d]\n", |
1621 | slot, child->nr_leaves_on_branch, nr_free + 1, |
1622 | next_slot); |
1623 | } |
1624 | } |
1625 | |
1626 | pr_devel("after: %lu\n", new_n->nr_leaves_on_branch); |
1627 | |
1628 | nr_leaves_on_tree = new_n->nr_leaves_on_branch; |
1629 | |
1630 | /* Excise this node if it is singly occupied by a shortcut */ |
1631 | if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) { |
1632 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) |
1633 | if ((ptr = new_n->slots[slot])) |
1634 | break; |
1635 | |
1636 | if (assoc_array_ptr_is_meta(ptr) && |
1637 | assoc_array_ptr_is_shortcut(ptr)) { |
1638 | pr_devel("excise node %p with 1 shortcut\n", new_n); |
1639 | new_s = assoc_array_ptr_to_shortcut(ptr); |
1640 | new_parent = new_n->back_pointer; |
1641 | slot = new_n->parent_slot; |
1642 | kfree(new_n); |
1643 | if (!new_parent) { |
1644 | new_s->back_pointer = NULL; |
1645 | new_s->parent_slot = 0; |
1646 | new_root = ptr; |
1647 | goto gc_complete; |
1648 | } |
1649 | |
1650 | if (assoc_array_ptr_is_shortcut(new_parent)) { |
1651 | /* We can discard any preceding shortcut also */ |
1652 | struct assoc_array_shortcut *s = |
1653 | assoc_array_ptr_to_shortcut(new_parent); |
1654 | |
1655 | pr_devel("excise preceding shortcut\n"); |
1656 | |
1657 | new_parent = new_s->back_pointer = s->back_pointer; |
1658 | slot = new_s->parent_slot = s->parent_slot; |
1659 | kfree(s); |
1660 | if (!new_parent) { |
1661 | new_s->back_pointer = NULL; |
1662 | new_s->parent_slot = 0; |
1663 | new_root = ptr; |
1664 | goto gc_complete; |
1665 | } |
1666 | } |
1667 | |
1668 | new_s->back_pointer = new_parent; |
1669 | new_s->parent_slot = slot; |
1670 | new_n = assoc_array_ptr_to_node(new_parent); |
1671 | new_n->slots[slot] = ptr; |
1672 | goto ascend_old_tree; |
1673 | } |
1674 | } |
1675 | |
1676 | /* Excise any shortcuts we might encounter that point to nodes that |
1677 | * only contain leaves. |
1678 | */ |
1679 | ptr = new_n->back_pointer; |
1680 | if (!ptr) |
1681 | goto gc_complete; |
1682 | |
1683 | if (assoc_array_ptr_is_shortcut(ptr)) { |
1684 | new_s = assoc_array_ptr_to_shortcut(ptr); |
1685 | new_parent = new_s->back_pointer; |
1686 | slot = new_s->parent_slot; |
1687 | |
1688 | if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { |
1689 | struct assoc_array_node *n; |
1690 | |
1691 | pr_devel("excise shortcut\n"); |
1692 | new_n->back_pointer = new_parent; |
1693 | new_n->parent_slot = slot; |
1694 | kfree(new_s); |
1695 | if (!new_parent) { |
1696 | new_root = assoc_array_node_to_ptr(new_n); |
1697 | goto gc_complete; |
1698 | } |
1699 | |
1700 | n = assoc_array_ptr_to_node(new_parent); |
1701 | n->slots[slot] = assoc_array_node_to_ptr(new_n); |
1702 | } |
1703 | } else { |
1704 | new_parent = ptr; |
1705 | } |
1706 | new_n = assoc_array_ptr_to_node(new_parent); |
1707 | |
1708 | ascend_old_tree: |
1709 | ptr = node->back_pointer; |
1710 | if (assoc_array_ptr_is_shortcut(ptr)) { |
1711 | shortcut = assoc_array_ptr_to_shortcut(ptr); |
1712 | slot = shortcut->parent_slot; |
1713 | cursor = shortcut->back_pointer; |
1714 | if (!cursor) |
1715 | goto gc_complete; |
1716 | } else { |
1717 | slot = node->parent_slot; |
1718 | cursor = ptr; |
1719 | } |
1720 | BUG_ON(!cursor); |
1721 | node = assoc_array_ptr_to_node(cursor); |
1722 | slot++; |
1723 | goto continue_node; |
1724 | |
1725 | gc_complete: |
1726 | edit->set[0].to = new_root; |
1727 | assoc_array_apply_edit(edit); |
1728 | array->nr_leaves_on_tree = nr_leaves_on_tree; |
1729 | return 0; |
1730 | |
1731 | enomem: |
1732 | pr_devel("enomem\n"); |
1733 | assoc_array_destroy_subtree(new_root, edit->ops); |
1734 | kfree(edit); |
1735 | return -ENOMEM; |
1736 | } |
1737 |