1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* Generic associative array implementation. |
3 | * |
4 | * See Documentation/core-api/assoc_array.rst for information. |
5 | * |
6 | * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. |
7 | * Written by David Howells (dhowells@redhat.com) |
8 | */ |
9 | //#define DEBUG |
10 | #include <linux/rcupdate.h> |
11 | #include <linux/slab.h> |
12 | #include <linux/err.h> |
13 | #include <linux/assoc_array_priv.h> |
14 | |
15 | /* |
16 | * Iterate over an associative array. The caller must hold the RCU read lock |
17 | * or better. |
18 | */ |
19 | static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root, |
20 | const struct assoc_array_ptr *stop, |
21 | int (*iterator)(const void *leaf, |
22 | void *iterator_data), |
23 | void *iterator_data) |
24 | { |
25 | const struct assoc_array_shortcut *shortcut; |
26 | const struct assoc_array_node *node; |
27 | const struct assoc_array_ptr *cursor, *ptr, *parent; |
28 | unsigned long has_meta; |
29 | int slot, ret; |
30 | |
31 | cursor = root; |
32 | |
33 | begin_node: |
34 | if (assoc_array_ptr_is_shortcut(x: cursor)) { |
35 | /* Descend through a shortcut */ |
36 | shortcut = assoc_array_ptr_to_shortcut(x: cursor); |
37 | cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */ |
38 | } |
39 | |
40 | node = assoc_array_ptr_to_node(x: cursor); |
41 | slot = 0; |
42 | |
43 | /* We perform two passes of each node. |
44 | * |
45 | * The first pass does all the leaves in this node. This means we |
46 | * don't miss any leaves if the node is split up by insertion whilst |
47 | * we're iterating over the branches rooted here (we may, however, see |
48 | * some leaves twice). |
49 | */ |
50 | has_meta = 0; |
51 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
52 | ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */ |
53 | has_meta |= (unsigned long)ptr; |
54 | if (ptr && assoc_array_ptr_is_leaf(x: ptr)) { |
55 | /* We need a barrier between the read of the pointer, |
56 | * which is supplied by the above READ_ONCE(). |
57 | */ |
58 | /* Invoke the callback */ |
59 | ret = iterator(assoc_array_ptr_to_leaf(x: ptr), |
60 | iterator_data); |
61 | if (ret) |
62 | return ret; |
63 | } |
64 | } |
65 | |
66 | /* The second pass attends to all the metadata pointers. If we follow |
67 | * one of these we may find that we don't come back here, but rather go |
68 | * back to a replacement node with the leaves in a different layout. |
69 | * |
70 | * We are guaranteed to make progress, however, as the slot number for |
71 | * a particular portion of the key space cannot change - and we |
72 | * continue at the back pointer + 1. |
73 | */ |
74 | if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE)) |
75 | goto finished_node; |
76 | slot = 0; |
77 | |
78 | continue_node: |
79 | node = assoc_array_ptr_to_node(x: cursor); |
80 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
81 | ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */ |
82 | if (assoc_array_ptr_is_meta(x: ptr)) { |
83 | cursor = ptr; |
84 | goto begin_node; |
85 | } |
86 | } |
87 | |
88 | finished_node: |
89 | /* Move up to the parent (may need to skip back over a shortcut) */ |
90 | parent = READ_ONCE(node->back_pointer); /* Address dependency. */ |
91 | slot = node->parent_slot; |
92 | if (parent == stop) |
93 | return 0; |
94 | |
95 | if (assoc_array_ptr_is_shortcut(x: parent)) { |
96 | shortcut = assoc_array_ptr_to_shortcut(x: parent); |
97 | cursor = parent; |
98 | parent = READ_ONCE(shortcut->back_pointer); /* Address dependency. */ |
99 | slot = shortcut->parent_slot; |
100 | if (parent == stop) |
101 | return 0; |
102 | } |
103 | |
104 | /* Ascend to next slot in parent node */ |
105 | cursor = parent; |
106 | slot++; |
107 | goto continue_node; |
108 | } |
109 | |
110 | /** |
111 | * assoc_array_iterate - Pass all objects in the array to a callback |
112 | * @array: The array to iterate over. |
113 | * @iterator: The callback function. |
114 | * @iterator_data: Private data for the callback function. |
115 | * |
116 | * Iterate over all the objects in an associative array. Each one will be |
117 | * presented to the iterator function. |
118 | * |
119 | * If the array is being modified concurrently with the iteration then it is |
120 | * possible that some objects in the array will be passed to the iterator |
121 | * callback more than once - though every object should be passed at least |
122 | * once. If this is undesirable then the caller must lock against modification |
123 | * for the duration of this function. |
124 | * |
125 | * The function will return 0 if no objects were in the array or else it will |
126 | * return the result of the last iterator function called. Iteration stops |
127 | * immediately if any call to the iteration function results in a non-zero |
128 | * return. |
129 | * |
130 | * The caller should hold the RCU read lock or better if concurrent |
131 | * modification is possible. |
132 | */ |
133 | int assoc_array_iterate(const struct assoc_array *array, |
134 | int (*iterator)(const void *object, |
135 | void *iterator_data), |
136 | void *iterator_data) |
137 | { |
138 | struct assoc_array_ptr *root = READ_ONCE(array->root); /* Address dependency. */ |
139 | |
140 | if (!root) |
141 | return 0; |
142 | return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data); |
143 | } |
144 | |
145 | enum assoc_array_walk_status { |
146 | assoc_array_walk_tree_empty, |
147 | assoc_array_walk_found_terminal_node, |
148 | assoc_array_walk_found_wrong_shortcut, |
149 | }; |
150 | |
151 | struct assoc_array_walk_result { |
152 | struct { |
153 | struct assoc_array_node *node; /* Node in which leaf might be found */ |
154 | int level; |
155 | int slot; |
156 | } terminal_node; |
157 | struct { |
158 | struct assoc_array_shortcut *shortcut; |
159 | int level; |
160 | int sc_level; |
161 | unsigned long sc_segments; |
162 | unsigned long dissimilarity; |
163 | } wrong_shortcut; |
164 | }; |
165 | |
166 | /* |
167 | * Navigate through the internal tree looking for the closest node to the key. |
168 | */ |
169 | static enum assoc_array_walk_status |
170 | assoc_array_walk(const struct assoc_array *array, |
171 | const struct assoc_array_ops *ops, |
172 | const void *index_key, |
173 | struct assoc_array_walk_result *result) |
174 | { |
175 | struct assoc_array_shortcut *shortcut; |
176 | struct assoc_array_node *node; |
177 | struct assoc_array_ptr *cursor, *ptr; |
178 | unsigned long sc_segments, dissimilarity; |
179 | unsigned long segments; |
180 | int level, sc_level, next_sc_level; |
181 | int slot; |
182 | |
183 | pr_devel("-->%s()\n" , __func__); |
184 | |
185 | cursor = READ_ONCE(array->root); /* Address dependency. */ |
186 | if (!cursor) |
187 | return assoc_array_walk_tree_empty; |
188 | |
189 | level = 0; |
190 | |
191 | /* Use segments from the key for the new leaf to navigate through the |
192 | * internal tree, skipping through nodes and shortcuts that are on |
193 | * route to the destination. Eventually we'll come to a slot that is |
194 | * either empty or contains a leaf at which point we've found a node in |
195 | * which the leaf we're looking for might be found or into which it |
196 | * should be inserted. |
197 | */ |
198 | jumped: |
199 | segments = ops->get_key_chunk(index_key, level); |
200 | pr_devel("segments[%d]: %lx\n" , level, segments); |
201 | |
202 | if (assoc_array_ptr_is_shortcut(x: cursor)) |
203 | goto follow_shortcut; |
204 | |
205 | consider_node: |
206 | node = assoc_array_ptr_to_node(x: cursor); |
207 | slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK); |
208 | slot &= ASSOC_ARRAY_FAN_MASK; |
209 | ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */ |
210 | |
211 | pr_devel("consider slot %x [ix=%d type=%lu]\n" , |
212 | slot, level, (unsigned long)ptr & 3); |
213 | |
214 | if (!assoc_array_ptr_is_meta(x: ptr)) { |
215 | /* The node doesn't have a node/shortcut pointer in the slot |
216 | * corresponding to the index key that we have to follow. |
217 | */ |
218 | result->terminal_node.node = node; |
219 | result->terminal_node.level = level; |
220 | result->terminal_node.slot = slot; |
221 | pr_devel("<--%s() = terminal_node\n" , __func__); |
222 | return assoc_array_walk_found_terminal_node; |
223 | } |
224 | |
225 | if (assoc_array_ptr_is_node(x: ptr)) { |
226 | /* There is a pointer to a node in the slot corresponding to |
227 | * this index key segment, so we need to follow it. |
228 | */ |
229 | cursor = ptr; |
230 | level += ASSOC_ARRAY_LEVEL_STEP; |
231 | if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) |
232 | goto consider_node; |
233 | goto jumped; |
234 | } |
235 | |
236 | /* There is a shortcut in the slot corresponding to the index key |
237 | * segment. We follow the shortcut if its partial index key matches |
238 | * this leaf's. Otherwise we need to split the shortcut. |
239 | */ |
240 | cursor = ptr; |
241 | follow_shortcut: |
242 | shortcut = assoc_array_ptr_to_shortcut(x: cursor); |
243 | pr_devel("shortcut to %d\n" , shortcut->skip_to_level); |
244 | sc_level = level + ASSOC_ARRAY_LEVEL_STEP; |
245 | BUG_ON(sc_level > shortcut->skip_to_level); |
246 | |
247 | do { |
248 | /* Check the leaf against the shortcut's index key a word at a |
249 | * time, trimming the final word (the shortcut stores the index |
250 | * key completely from the root to the shortcut's target). |
251 | */ |
252 | if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0) |
253 | segments = ops->get_key_chunk(index_key, sc_level); |
254 | |
255 | sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT]; |
256 | dissimilarity = segments ^ sc_segments; |
257 | |
258 | if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) { |
259 | /* Trim segments that are beyond the shortcut */ |
260 | int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
261 | dissimilarity &= ~(ULONG_MAX << shift); |
262 | next_sc_level = shortcut->skip_to_level; |
263 | } else { |
264 | next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE; |
265 | next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
266 | } |
267 | |
268 | if (dissimilarity != 0) { |
269 | /* This shortcut points elsewhere */ |
270 | result->wrong_shortcut.shortcut = shortcut; |
271 | result->wrong_shortcut.level = level; |
272 | result->wrong_shortcut.sc_level = sc_level; |
273 | result->wrong_shortcut.sc_segments = sc_segments; |
274 | result->wrong_shortcut.dissimilarity = dissimilarity; |
275 | return assoc_array_walk_found_wrong_shortcut; |
276 | } |
277 | |
278 | sc_level = next_sc_level; |
279 | } while (sc_level < shortcut->skip_to_level); |
280 | |
281 | /* The shortcut matches the leaf's index to this point. */ |
282 | cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */ |
283 | if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) { |
284 | level = sc_level; |
285 | goto jumped; |
286 | } else { |
287 | level = sc_level; |
288 | goto consider_node; |
289 | } |
290 | } |
291 | |
292 | /** |
293 | * assoc_array_find - Find an object by index key |
294 | * @array: The associative array to search. |
295 | * @ops: The operations to use. |
296 | * @index_key: The key to the object. |
297 | * |
298 | * Find an object in an associative array by walking through the internal tree |
299 | * to the node that should contain the object and then searching the leaves |
300 | * there. NULL is returned if the requested object was not found in the array. |
301 | * |
302 | * The caller must hold the RCU read lock or better. |
303 | */ |
304 | void *assoc_array_find(const struct assoc_array *array, |
305 | const struct assoc_array_ops *ops, |
306 | const void *index_key) |
307 | { |
308 | struct assoc_array_walk_result result; |
309 | const struct assoc_array_node *node; |
310 | const struct assoc_array_ptr *ptr; |
311 | const void *leaf; |
312 | int slot; |
313 | |
314 | if (assoc_array_walk(array, ops, index_key, result: &result) != |
315 | assoc_array_walk_found_terminal_node) |
316 | return NULL; |
317 | |
318 | node = result.terminal_node.node; |
319 | |
320 | /* If the target key is available to us, it's has to be pointed to by |
321 | * the terminal node. |
322 | */ |
323 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
324 | ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */ |
325 | if (ptr && assoc_array_ptr_is_leaf(x: ptr)) { |
326 | /* We need a barrier between the read of the pointer |
327 | * and dereferencing the pointer - but only if we are |
328 | * actually going to dereference it. |
329 | */ |
330 | leaf = assoc_array_ptr_to_leaf(x: ptr); |
331 | if (ops->compare_object(leaf, index_key)) |
332 | return (void *)leaf; |
333 | } |
334 | } |
335 | |
336 | return NULL; |
337 | } |
338 | |
339 | /* |
340 | * Destructively iterate over an associative array. The caller must prevent |
341 | * other simultaneous accesses. |
342 | */ |
343 | static void assoc_array_destroy_subtree(struct assoc_array_ptr *root, |
344 | const struct assoc_array_ops *ops) |
345 | { |
346 | struct assoc_array_shortcut *shortcut; |
347 | struct assoc_array_node *node; |
348 | struct assoc_array_ptr *cursor, *parent = NULL; |
349 | int slot = -1; |
350 | |
351 | pr_devel("-->%s()\n" , __func__); |
352 | |
353 | cursor = root; |
354 | if (!cursor) { |
355 | pr_devel("empty\n" ); |
356 | return; |
357 | } |
358 | |
359 | move_to_meta: |
360 | if (assoc_array_ptr_is_shortcut(x: cursor)) { |
361 | /* Descend through a shortcut */ |
362 | pr_devel("[%d] shortcut\n" , slot); |
363 | BUG_ON(!assoc_array_ptr_is_shortcut(cursor)); |
364 | shortcut = assoc_array_ptr_to_shortcut(x: cursor); |
365 | BUG_ON(shortcut->back_pointer != parent); |
366 | BUG_ON(slot != -1 && shortcut->parent_slot != slot); |
367 | parent = cursor; |
368 | cursor = shortcut->next_node; |
369 | slot = -1; |
370 | BUG_ON(!assoc_array_ptr_is_node(cursor)); |
371 | } |
372 | |
373 | pr_devel("[%d] node\n" , slot); |
374 | node = assoc_array_ptr_to_node(x: cursor); |
375 | BUG_ON(node->back_pointer != parent); |
376 | BUG_ON(slot != -1 && node->parent_slot != slot); |
377 | slot = 0; |
378 | |
379 | continue_node: |
380 | pr_devel("Node %p [back=%p]\n" , node, node->back_pointer); |
381 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
382 | struct assoc_array_ptr *ptr = node->slots[slot]; |
383 | if (!ptr) |
384 | continue; |
385 | if (assoc_array_ptr_is_meta(x: ptr)) { |
386 | parent = cursor; |
387 | cursor = ptr; |
388 | goto move_to_meta; |
389 | } |
390 | |
391 | if (ops) { |
392 | pr_devel("[%d] free leaf\n" , slot); |
393 | ops->free_object(assoc_array_ptr_to_leaf(x: ptr)); |
394 | } |
395 | } |
396 | |
397 | parent = node->back_pointer; |
398 | slot = node->parent_slot; |
399 | pr_devel("free node\n" ); |
400 | kfree(objp: node); |
401 | if (!parent) |
402 | return; /* Done */ |
403 | |
404 | /* Move back up to the parent (may need to free a shortcut on |
405 | * the way up) */ |
406 | if (assoc_array_ptr_is_shortcut(x: parent)) { |
407 | shortcut = assoc_array_ptr_to_shortcut(x: parent); |
408 | BUG_ON(shortcut->next_node != cursor); |
409 | cursor = parent; |
410 | parent = shortcut->back_pointer; |
411 | slot = shortcut->parent_slot; |
412 | pr_devel("free shortcut\n" ); |
413 | kfree(objp: shortcut); |
414 | if (!parent) |
415 | return; |
416 | |
417 | BUG_ON(!assoc_array_ptr_is_node(parent)); |
418 | } |
419 | |
420 | /* Ascend to next slot in parent node */ |
421 | pr_devel("ascend to %p[%d]\n" , parent, slot); |
422 | cursor = parent; |
423 | node = assoc_array_ptr_to_node(x: cursor); |
424 | slot++; |
425 | goto continue_node; |
426 | } |
427 | |
428 | /** |
429 | * assoc_array_destroy - Destroy an associative array |
430 | * @array: The array to destroy. |
431 | * @ops: The operations to use. |
432 | * |
433 | * Discard all metadata and free all objects in an associative array. The |
434 | * array will be empty and ready to use again upon completion. This function |
435 | * cannot fail. |
436 | * |
437 | * The caller must prevent all other accesses whilst this takes place as no |
438 | * attempt is made to adjust pointers gracefully to permit RCU readlock-holding |
439 | * accesses to continue. On the other hand, no memory allocation is required. |
440 | */ |
441 | void assoc_array_destroy(struct assoc_array *array, |
442 | const struct assoc_array_ops *ops) |
443 | { |
444 | assoc_array_destroy_subtree(root: array->root, ops); |
445 | array->root = NULL; |
446 | } |
447 | |
448 | /* |
449 | * Handle insertion into an empty tree. |
450 | */ |
451 | static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit) |
452 | { |
453 | struct assoc_array_node *new_n0; |
454 | |
455 | pr_devel("-->%s()\n" , __func__); |
456 | |
457 | new_n0 = kzalloc(size: sizeof(struct assoc_array_node), GFP_KERNEL); |
458 | if (!new_n0) |
459 | return false; |
460 | |
461 | edit->new_meta[0] = assoc_array_node_to_ptr(p: new_n0); |
462 | edit->leaf_p = &new_n0->slots[0]; |
463 | edit->adjust_count_on = new_n0; |
464 | edit->set[0].ptr = &edit->array->root; |
465 | edit->set[0].to = assoc_array_node_to_ptr(p: new_n0); |
466 | |
467 | pr_devel("<--%s() = ok [no root]\n" , __func__); |
468 | return true; |
469 | } |
470 | |
471 | /* |
472 | * Handle insertion into a terminal node. |
473 | */ |
474 | static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit, |
475 | const struct assoc_array_ops *ops, |
476 | const void *index_key, |
477 | struct assoc_array_walk_result *result) |
478 | { |
479 | struct assoc_array_shortcut *shortcut, *new_s0; |
480 | struct assoc_array_node *node, *new_n0, *new_n1, *side; |
481 | struct assoc_array_ptr *ptr; |
482 | unsigned long dissimilarity, base_seg, blank; |
483 | size_t keylen; |
484 | bool have_meta; |
485 | int level, diff; |
486 | int slot, next_slot, free_slot, i, j; |
487 | |
488 | node = result->terminal_node.node; |
489 | level = result->terminal_node.level; |
490 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot; |
491 | |
492 | pr_devel("-->%s()\n" , __func__); |
493 | |
494 | /* We arrived at a node which doesn't have an onward node or shortcut |
495 | * pointer that we have to follow. This means that (a) the leaf we |
496 | * want must go here (either by insertion or replacement) or (b) we |
497 | * need to split this node and insert in one of the fragments. |
498 | */ |
499 | free_slot = -1; |
500 | |
501 | /* Firstly, we have to check the leaves in this node to see if there's |
502 | * a matching one we should replace in place. |
503 | */ |
504 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
505 | ptr = node->slots[i]; |
506 | if (!ptr) { |
507 | free_slot = i; |
508 | continue; |
509 | } |
510 | if (assoc_array_ptr_is_leaf(x: ptr) && |
511 | ops->compare_object(assoc_array_ptr_to_leaf(x: ptr), |
512 | index_key)) { |
513 | pr_devel("replace in slot %d\n" , i); |
514 | edit->leaf_p = &node->slots[i]; |
515 | edit->dead_leaf = node->slots[i]; |
516 | pr_devel("<--%s() = ok [replace]\n" , __func__); |
517 | return true; |
518 | } |
519 | } |
520 | |
521 | /* If there is a free slot in this node then we can just insert the |
522 | * leaf here. |
523 | */ |
524 | if (free_slot >= 0) { |
525 | pr_devel("insert in free slot %d\n" , free_slot); |
526 | edit->leaf_p = &node->slots[free_slot]; |
527 | edit->adjust_count_on = node; |
528 | pr_devel("<--%s() = ok [insert]\n" , __func__); |
529 | return true; |
530 | } |
531 | |
532 | /* The node has no spare slots - so we're either going to have to split |
533 | * it or insert another node before it. |
534 | * |
535 | * Whatever, we're going to need at least two new nodes - so allocate |
536 | * those now. We may also need a new shortcut, but we deal with that |
537 | * when we need it. |
538 | */ |
539 | new_n0 = kzalloc(size: sizeof(struct assoc_array_node), GFP_KERNEL); |
540 | if (!new_n0) |
541 | return false; |
542 | edit->new_meta[0] = assoc_array_node_to_ptr(p: new_n0); |
543 | new_n1 = kzalloc(size: sizeof(struct assoc_array_node), GFP_KERNEL); |
544 | if (!new_n1) |
545 | return false; |
546 | edit->new_meta[1] = assoc_array_node_to_ptr(p: new_n1); |
547 | |
548 | /* We need to find out how similar the leaves are. */ |
549 | pr_devel("no spare slots\n" ); |
550 | have_meta = false; |
551 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
552 | ptr = node->slots[i]; |
553 | if (assoc_array_ptr_is_meta(x: ptr)) { |
554 | edit->segment_cache[i] = 0xff; |
555 | have_meta = true; |
556 | continue; |
557 | } |
558 | base_seg = ops->get_object_key_chunk( |
559 | assoc_array_ptr_to_leaf(x: ptr), level); |
560 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
561 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; |
562 | } |
563 | |
564 | if (have_meta) { |
565 | pr_devel("have meta\n" ); |
566 | goto split_node; |
567 | } |
568 | |
569 | /* The node contains only leaves */ |
570 | dissimilarity = 0; |
571 | base_seg = edit->segment_cache[0]; |
572 | for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++) |
573 | dissimilarity |= edit->segment_cache[i] ^ base_seg; |
574 | |
575 | pr_devel("only leaves; dissimilarity=%lx\n" , dissimilarity); |
576 | |
577 | if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) { |
578 | /* The old leaves all cluster in the same slot. We will need |
579 | * to insert a shortcut if the new node wants to cluster with them. |
580 | */ |
581 | if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0) |
582 | goto all_leaves_cluster_together; |
583 | |
584 | /* Otherwise all the old leaves cluster in the same slot, but |
585 | * the new leaf wants to go into a different slot - so we |
586 | * create a new node (n0) to hold the new leaf and a pointer to |
587 | * a new node (n1) holding all the old leaves. |
588 | * |
589 | * This can be done by falling through to the node splitting |
590 | * path. |
591 | */ |
592 | pr_devel("present leaves cluster but not new leaf\n" ); |
593 | } |
594 | |
595 | split_node: |
596 | pr_devel("split node\n" ); |
597 | |
598 | /* We need to split the current node. The node must contain anything |
599 | * from a single leaf (in the one leaf case, this leaf will cluster |
600 | * with the new leaf) and the rest meta-pointers, to all leaves, some |
601 | * of which may cluster. |
602 | * |
603 | * It won't contain the case in which all the current leaves plus the |
604 | * new leaves want to cluster in the same slot. |
605 | * |
606 | * We need to expel at least two leaves out of a set consisting of the |
607 | * leaves in the node and the new leaf. The current meta pointers can |
608 | * just be copied as they shouldn't cluster with any of the leaves. |
609 | * |
610 | * We need a new node (n0) to replace the current one and a new node to |
611 | * take the expelled nodes (n1). |
612 | */ |
613 | edit->set[0].to = assoc_array_node_to_ptr(p: new_n0); |
614 | new_n0->back_pointer = node->back_pointer; |
615 | new_n0->parent_slot = node->parent_slot; |
616 | new_n1->back_pointer = assoc_array_node_to_ptr(p: new_n0); |
617 | new_n1->parent_slot = -1; /* Need to calculate this */ |
618 | |
619 | do_split_node: |
620 | pr_devel("do_split_node\n" ); |
621 | |
622 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; |
623 | new_n1->nr_leaves_on_branch = 0; |
624 | |
625 | /* Begin by finding two matching leaves. There have to be at least two |
626 | * that match - even if there are meta pointers - because any leaf that |
627 | * would match a slot with a meta pointer in it must be somewhere |
628 | * behind that meta pointer and cannot be here. Further, given N |
629 | * remaining leaf slots, we now have N+1 leaves to go in them. |
630 | */ |
631 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
632 | slot = edit->segment_cache[i]; |
633 | if (slot != 0xff) |
634 | for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++) |
635 | if (edit->segment_cache[j] == slot) |
636 | goto found_slot_for_multiple_occupancy; |
637 | } |
638 | found_slot_for_multiple_occupancy: |
639 | pr_devel("same slot: %x %x [%02x]\n" , i, j, slot); |
640 | BUG_ON(i >= ASSOC_ARRAY_FAN_OUT); |
641 | BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1); |
642 | BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT); |
643 | |
644 | new_n1->parent_slot = slot; |
645 | |
646 | /* Metadata pointers cannot change slot */ |
647 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) |
648 | if (assoc_array_ptr_is_meta(x: node->slots[i])) |
649 | new_n0->slots[i] = node->slots[i]; |
650 | else |
651 | new_n0->slots[i] = NULL; |
652 | BUG_ON(new_n0->slots[slot] != NULL); |
653 | new_n0->slots[slot] = assoc_array_node_to_ptr(p: new_n1); |
654 | |
655 | /* Filter the leaf pointers between the new nodes */ |
656 | free_slot = -1; |
657 | next_slot = 0; |
658 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
659 | if (assoc_array_ptr_is_meta(x: node->slots[i])) |
660 | continue; |
661 | if (edit->segment_cache[i] == slot) { |
662 | new_n1->slots[next_slot++] = node->slots[i]; |
663 | new_n1->nr_leaves_on_branch++; |
664 | } else { |
665 | do { |
666 | free_slot++; |
667 | } while (new_n0->slots[free_slot] != NULL); |
668 | new_n0->slots[free_slot] = node->slots[i]; |
669 | } |
670 | } |
671 | |
672 | pr_devel("filtered: f=%x n=%x\n" , free_slot, next_slot); |
673 | |
674 | if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) { |
675 | do { |
676 | free_slot++; |
677 | } while (new_n0->slots[free_slot] != NULL); |
678 | edit->leaf_p = &new_n0->slots[free_slot]; |
679 | edit->adjust_count_on = new_n0; |
680 | } else { |
681 | edit->leaf_p = &new_n1->slots[next_slot++]; |
682 | edit->adjust_count_on = new_n1; |
683 | } |
684 | |
685 | BUG_ON(next_slot <= 1); |
686 | |
687 | edit->set_backpointers_to = assoc_array_node_to_ptr(p: new_n0); |
688 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
689 | if (edit->segment_cache[i] == 0xff) { |
690 | ptr = node->slots[i]; |
691 | BUG_ON(assoc_array_ptr_is_leaf(ptr)); |
692 | if (assoc_array_ptr_is_node(x: ptr)) { |
693 | side = assoc_array_ptr_to_node(x: ptr); |
694 | edit->set_backpointers[i] = &side->back_pointer; |
695 | } else { |
696 | shortcut = assoc_array_ptr_to_shortcut(x: ptr); |
697 | edit->set_backpointers[i] = &shortcut->back_pointer; |
698 | } |
699 | } |
700 | } |
701 | |
702 | ptr = node->back_pointer; |
703 | if (!ptr) |
704 | edit->set[0].ptr = &edit->array->root; |
705 | else if (assoc_array_ptr_is_node(x: ptr)) |
706 | edit->set[0].ptr = &assoc_array_ptr_to_node(x: ptr)->slots[node->parent_slot]; |
707 | else |
708 | edit->set[0].ptr = &assoc_array_ptr_to_shortcut(x: ptr)->next_node; |
709 | edit->excised_meta[0] = assoc_array_node_to_ptr(p: node); |
710 | pr_devel("<--%s() = ok [split node]\n" , __func__); |
711 | return true; |
712 | |
713 | all_leaves_cluster_together: |
714 | /* All the leaves, new and old, want to cluster together in this node |
715 | * in the same slot, so we have to replace this node with a shortcut to |
716 | * skip over the identical parts of the key and then place a pair of |
717 | * nodes, one inside the other, at the end of the shortcut and |
718 | * distribute the keys between them. |
719 | * |
720 | * Firstly we need to work out where the leaves start diverging as a |
721 | * bit position into their keys so that we know how big the shortcut |
722 | * needs to be. |
723 | * |
724 | * We only need to make a single pass of N of the N+1 leaves because if |
725 | * any keys differ between themselves at bit X then at least one of |
726 | * them must also differ with the base key at bit X or before. |
727 | */ |
728 | pr_devel("all leaves cluster together\n" ); |
729 | diff = INT_MAX; |
730 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
731 | int x = ops->diff_objects(assoc_array_ptr_to_leaf(x: node->slots[i]), |
732 | index_key); |
733 | if (x < diff) { |
734 | BUG_ON(x < 0); |
735 | diff = x; |
736 | } |
737 | } |
738 | BUG_ON(diff == INT_MAX); |
739 | BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP); |
740 | |
741 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
742 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
743 | |
744 | new_s0 = kzalloc(struct_size(new_s0, index_key, keylen), GFP_KERNEL); |
745 | if (!new_s0) |
746 | return false; |
747 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(p: new_s0); |
748 | |
749 | edit->set[0].to = assoc_array_shortcut_to_ptr(p: new_s0); |
750 | new_s0->back_pointer = node->back_pointer; |
751 | new_s0->parent_slot = node->parent_slot; |
752 | new_s0->next_node = assoc_array_node_to_ptr(p: new_n0); |
753 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(p: new_s0); |
754 | new_n0->parent_slot = 0; |
755 | new_n1->back_pointer = assoc_array_node_to_ptr(p: new_n0); |
756 | new_n1->parent_slot = -1; /* Need to calculate this */ |
757 | |
758 | new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK; |
759 | pr_devel("skip_to_level = %d [diff %d]\n" , level, diff); |
760 | BUG_ON(level <= 0); |
761 | |
762 | for (i = 0; i < keylen; i++) |
763 | new_s0->index_key[i] = |
764 | ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE); |
765 | |
766 | if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) { |
767 | blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); |
768 | pr_devel("blank off [%zu] %d: %lx\n" , keylen - 1, level, blank); |
769 | new_s0->index_key[keylen - 1] &= ~blank; |
770 | } |
771 | |
772 | /* This now reduces to a node splitting exercise for which we'll need |
773 | * to regenerate the disparity table. |
774 | */ |
775 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
776 | ptr = node->slots[i]; |
777 | base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(x: ptr), |
778 | level); |
779 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
780 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; |
781 | } |
782 | |
783 | base_seg = ops->get_key_chunk(index_key, level); |
784 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
785 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK; |
786 | goto do_split_node; |
787 | } |
788 | |
789 | /* |
790 | * Handle insertion into the middle of a shortcut. |
791 | */ |
792 | static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit, |
793 | const struct assoc_array_ops *ops, |
794 | struct assoc_array_walk_result *result) |
795 | { |
796 | struct assoc_array_shortcut *shortcut, *new_s0, *new_s1; |
797 | struct assoc_array_node *node, *new_n0, *side; |
798 | unsigned long sc_segments, dissimilarity, blank; |
799 | size_t keylen; |
800 | int level, sc_level, diff; |
801 | int sc_slot; |
802 | |
803 | shortcut = result->wrong_shortcut.shortcut; |
804 | level = result->wrong_shortcut.level; |
805 | sc_level = result->wrong_shortcut.sc_level; |
806 | sc_segments = result->wrong_shortcut.sc_segments; |
807 | dissimilarity = result->wrong_shortcut.dissimilarity; |
808 | |
809 | pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n" , |
810 | __func__, level, dissimilarity, sc_level); |
811 | |
812 | /* We need to split a shortcut and insert a node between the two |
813 | * pieces. Zero-length pieces will be dispensed with entirely. |
814 | * |
815 | * First of all, we need to find out in which level the first |
816 | * difference was. |
817 | */ |
818 | diff = __ffs(dissimilarity); |
819 | diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK; |
820 | diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK; |
821 | pr_devel("diff=%d\n" , diff); |
822 | |
823 | if (!shortcut->back_pointer) { |
824 | edit->set[0].ptr = &edit->array->root; |
825 | } else if (assoc_array_ptr_is_node(x: shortcut->back_pointer)) { |
826 | node = assoc_array_ptr_to_node(x: shortcut->back_pointer); |
827 | edit->set[0].ptr = &node->slots[shortcut->parent_slot]; |
828 | } else { |
829 | BUG(); |
830 | } |
831 | |
832 | edit->excised_meta[0] = assoc_array_shortcut_to_ptr(p: shortcut); |
833 | |
834 | /* Create a new node now since we're going to need it anyway */ |
835 | new_n0 = kzalloc(size: sizeof(struct assoc_array_node), GFP_KERNEL); |
836 | if (!new_n0) |
837 | return false; |
838 | edit->new_meta[0] = assoc_array_node_to_ptr(p: new_n0); |
839 | edit->adjust_count_on = new_n0; |
840 | |
841 | /* Insert a new shortcut before the new node if this segment isn't of |
842 | * zero length - otherwise we just connect the new node directly to the |
843 | * parent. |
844 | */ |
845 | level += ASSOC_ARRAY_LEVEL_STEP; |
846 | if (diff > level) { |
847 | pr_devel("pre-shortcut %d...%d\n" , level, diff); |
848 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
849 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
850 | |
851 | new_s0 = kzalloc(struct_size(new_s0, index_key, keylen), |
852 | GFP_KERNEL); |
853 | if (!new_s0) |
854 | return false; |
855 | edit->new_meta[1] = assoc_array_shortcut_to_ptr(p: new_s0); |
856 | edit->set[0].to = assoc_array_shortcut_to_ptr(p: new_s0); |
857 | new_s0->back_pointer = shortcut->back_pointer; |
858 | new_s0->parent_slot = shortcut->parent_slot; |
859 | new_s0->next_node = assoc_array_node_to_ptr(p: new_n0); |
860 | new_s0->skip_to_level = diff; |
861 | |
862 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(p: new_s0); |
863 | new_n0->parent_slot = 0; |
864 | |
865 | memcpy(new_s0->index_key, shortcut->index_key, |
866 | flex_array_size(new_s0, index_key, keylen)); |
867 | |
868 | blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); |
869 | pr_devel("blank off [%zu] %d: %lx\n" , keylen - 1, diff, blank); |
870 | new_s0->index_key[keylen - 1] &= ~blank; |
871 | } else { |
872 | pr_devel("no pre-shortcut\n" ); |
873 | edit->set[0].to = assoc_array_node_to_ptr(p: new_n0); |
874 | new_n0->back_pointer = shortcut->back_pointer; |
875 | new_n0->parent_slot = shortcut->parent_slot; |
876 | } |
877 | |
878 | side = assoc_array_ptr_to_node(x: shortcut->next_node); |
879 | new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch; |
880 | |
881 | /* We need to know which slot in the new node is going to take a |
882 | * metadata pointer. |
883 | */ |
884 | sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); |
885 | sc_slot &= ASSOC_ARRAY_FAN_MASK; |
886 | |
887 | pr_devel("new slot %lx >> %d -> %d\n" , |
888 | sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot); |
889 | |
890 | /* Determine whether we need to follow the new node with a replacement |
891 | * for the current shortcut. We could in theory reuse the current |
892 | * shortcut if its parent slot number doesn't change - but that's a |
893 | * 1-in-16 chance so not worth expending the code upon. |
894 | */ |
895 | level = diff + ASSOC_ARRAY_LEVEL_STEP; |
896 | if (level < shortcut->skip_to_level) { |
897 | pr_devel("post-shortcut %d...%d\n" , level, shortcut->skip_to_level); |
898 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
899 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
900 | |
901 | new_s1 = kzalloc(struct_size(new_s1, index_key, keylen), |
902 | GFP_KERNEL); |
903 | if (!new_s1) |
904 | return false; |
905 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(p: new_s1); |
906 | |
907 | new_s1->back_pointer = assoc_array_node_to_ptr(p: new_n0); |
908 | new_s1->parent_slot = sc_slot; |
909 | new_s1->next_node = shortcut->next_node; |
910 | new_s1->skip_to_level = shortcut->skip_to_level; |
911 | |
912 | new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(p: new_s1); |
913 | |
914 | memcpy(new_s1->index_key, shortcut->index_key, |
915 | flex_array_size(new_s1, index_key, keylen)); |
916 | |
917 | edit->set[1].ptr = &side->back_pointer; |
918 | edit->set[1].to = assoc_array_shortcut_to_ptr(p: new_s1); |
919 | } else { |
920 | pr_devel("no post-shortcut\n" ); |
921 | |
922 | /* We don't have to replace the pointed-to node as long as we |
923 | * use memory barriers to make sure the parent slot number is |
924 | * changed before the back pointer (the parent slot number is |
925 | * irrelevant to the old parent shortcut). |
926 | */ |
927 | new_n0->slots[sc_slot] = shortcut->next_node; |
928 | edit->set_parent_slot[0].p = &side->parent_slot; |
929 | edit->set_parent_slot[0].to = sc_slot; |
930 | edit->set[1].ptr = &side->back_pointer; |
931 | edit->set[1].to = assoc_array_node_to_ptr(p: new_n0); |
932 | } |
933 | |
934 | /* Install the new leaf in a spare slot in the new node. */ |
935 | if (sc_slot == 0) |
936 | edit->leaf_p = &new_n0->slots[1]; |
937 | else |
938 | edit->leaf_p = &new_n0->slots[0]; |
939 | |
940 | pr_devel("<--%s() = ok [split shortcut]\n" , __func__); |
941 | return edit; |
942 | } |
943 | |
944 | /** |
945 | * assoc_array_insert - Script insertion of an object into an associative array |
946 | * @array: The array to insert into. |
947 | * @ops: The operations to use. |
948 | * @index_key: The key to insert at. |
949 | * @object: The object to insert. |
950 | * |
951 | * Precalculate and preallocate a script for the insertion or replacement of an |
952 | * object in an associative array. This results in an edit script that can |
953 | * either be applied or cancelled. |
954 | * |
955 | * The function returns a pointer to an edit script or -ENOMEM. |
956 | * |
957 | * The caller should lock against other modifications and must continue to hold |
958 | * the lock until assoc_array_apply_edit() has been called. |
959 | * |
960 | * Accesses to the tree may take place concurrently with this function, |
961 | * provided they hold the RCU read lock. |
962 | */ |
963 | struct assoc_array_edit *assoc_array_insert(struct assoc_array *array, |
964 | const struct assoc_array_ops *ops, |
965 | const void *index_key, |
966 | void *object) |
967 | { |
968 | struct assoc_array_walk_result result; |
969 | struct assoc_array_edit *edit; |
970 | |
971 | pr_devel("-->%s()\n" , __func__); |
972 | |
973 | /* The leaf pointer we're given must not have the bottom bit set as we |
974 | * use those for type-marking the pointer. NULL pointers are also not |
975 | * allowed as they indicate an empty slot but we have to allow them |
976 | * here as they can be updated later. |
977 | */ |
978 | BUG_ON(assoc_array_ptr_is_meta(object)); |
979 | |
980 | edit = kzalloc(size: sizeof(struct assoc_array_edit), GFP_KERNEL); |
981 | if (!edit) |
982 | return ERR_PTR(error: -ENOMEM); |
983 | edit->array = array; |
984 | edit->ops = ops; |
985 | edit->leaf = assoc_array_leaf_to_ptr(p: object); |
986 | edit->adjust_count_by = 1; |
987 | |
988 | switch (assoc_array_walk(array, ops, index_key, result: &result)) { |
989 | case assoc_array_walk_tree_empty: |
990 | /* Allocate a root node if there isn't one yet */ |
991 | if (!assoc_array_insert_in_empty_tree(edit)) |
992 | goto enomem; |
993 | return edit; |
994 | |
995 | case assoc_array_walk_found_terminal_node: |
996 | /* We found a node that doesn't have a node/shortcut pointer in |
997 | * the slot corresponding to the index key that we have to |
998 | * follow. |
999 | */ |
1000 | if (!assoc_array_insert_into_terminal_node(edit, ops, index_key, |
1001 | result: &result)) |
1002 | goto enomem; |
1003 | return edit; |
1004 | |
1005 | case assoc_array_walk_found_wrong_shortcut: |
1006 | /* We found a shortcut that didn't match our key in a slot we |
1007 | * needed to follow. |
1008 | */ |
1009 | if (!assoc_array_insert_mid_shortcut(edit, ops, result: &result)) |
1010 | goto enomem; |
1011 | return edit; |
1012 | } |
1013 | |
1014 | enomem: |
1015 | /* Clean up after an out of memory error */ |
1016 | pr_devel("enomem\n" ); |
1017 | assoc_array_cancel_edit(edit); |
1018 | return ERR_PTR(error: -ENOMEM); |
1019 | } |
1020 | |
1021 | /** |
1022 | * assoc_array_insert_set_object - Set the new object pointer in an edit script |
1023 | * @edit: The edit script to modify. |
1024 | * @object: The object pointer to set. |
1025 | * |
1026 | * Change the object to be inserted in an edit script. The object pointed to |
1027 | * by the old object is not freed. This must be done prior to applying the |
1028 | * script. |
1029 | */ |
1030 | void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object) |
1031 | { |
1032 | BUG_ON(!object); |
1033 | edit->leaf = assoc_array_leaf_to_ptr(p: object); |
1034 | } |
1035 | |
1036 | struct assoc_array_delete_collapse_context { |
1037 | struct assoc_array_node *node; |
1038 | const void *skip_leaf; |
1039 | int slot; |
1040 | }; |
1041 | |
1042 | /* |
1043 | * Subtree collapse to node iterator. |
1044 | */ |
1045 | static int assoc_array_delete_collapse_iterator(const void *leaf, |
1046 | void *iterator_data) |
1047 | { |
1048 | struct assoc_array_delete_collapse_context *collapse = iterator_data; |
1049 | |
1050 | if (leaf == collapse->skip_leaf) |
1051 | return 0; |
1052 | |
1053 | BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT); |
1054 | |
1055 | collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(p: leaf); |
1056 | return 0; |
1057 | } |
1058 | |
1059 | /** |
1060 | * assoc_array_delete - Script deletion of an object from an associative array |
1061 | * @array: The array to search. |
1062 | * @ops: The operations to use. |
1063 | * @index_key: The key to the object. |
1064 | * |
1065 | * Precalculate and preallocate a script for the deletion of an object from an |
1066 | * associative array. This results in an edit script that can either be |
1067 | * applied or cancelled. |
1068 | * |
1069 | * The function returns a pointer to an edit script if the object was found, |
1070 | * NULL if the object was not found or -ENOMEM. |
1071 | * |
1072 | * The caller should lock against other modifications and must continue to hold |
1073 | * the lock until assoc_array_apply_edit() has been called. |
1074 | * |
1075 | * Accesses to the tree may take place concurrently with this function, |
1076 | * provided they hold the RCU read lock. |
1077 | */ |
1078 | struct assoc_array_edit *assoc_array_delete(struct assoc_array *array, |
1079 | const struct assoc_array_ops *ops, |
1080 | const void *index_key) |
1081 | { |
1082 | struct assoc_array_delete_collapse_context collapse; |
1083 | struct assoc_array_walk_result result; |
1084 | struct assoc_array_node *node, *new_n0; |
1085 | struct assoc_array_edit *edit; |
1086 | struct assoc_array_ptr *ptr; |
1087 | bool has_meta; |
1088 | int slot, i; |
1089 | |
1090 | pr_devel("-->%s()\n" , __func__); |
1091 | |
1092 | edit = kzalloc(size: sizeof(struct assoc_array_edit), GFP_KERNEL); |
1093 | if (!edit) |
1094 | return ERR_PTR(error: -ENOMEM); |
1095 | edit->array = array; |
1096 | edit->ops = ops; |
1097 | edit->adjust_count_by = -1; |
1098 | |
1099 | switch (assoc_array_walk(array, ops, index_key, result: &result)) { |
1100 | case assoc_array_walk_found_terminal_node: |
1101 | /* We found a node that should contain the leaf we've been |
1102 | * asked to remove - *if* it's in the tree. |
1103 | */ |
1104 | pr_devel("terminal_node\n" ); |
1105 | node = result.terminal_node.node; |
1106 | |
1107 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1108 | ptr = node->slots[slot]; |
1109 | if (ptr && |
1110 | assoc_array_ptr_is_leaf(x: ptr) && |
1111 | ops->compare_object(assoc_array_ptr_to_leaf(x: ptr), |
1112 | index_key)) |
1113 | goto found_leaf; |
1114 | } |
1115 | fallthrough; |
1116 | case assoc_array_walk_tree_empty: |
1117 | case assoc_array_walk_found_wrong_shortcut: |
1118 | default: |
1119 | assoc_array_cancel_edit(edit); |
1120 | pr_devel("not found\n" ); |
1121 | return NULL; |
1122 | } |
1123 | |
1124 | found_leaf: |
1125 | BUG_ON(array->nr_leaves_on_tree <= 0); |
1126 | |
1127 | /* In the simplest form of deletion we just clear the slot and release |
1128 | * the leaf after a suitable interval. |
1129 | */ |
1130 | edit->dead_leaf = node->slots[slot]; |
1131 | edit->set[0].ptr = &node->slots[slot]; |
1132 | edit->set[0].to = NULL; |
1133 | edit->adjust_count_on = node; |
1134 | |
1135 | /* If that concludes erasure of the last leaf, then delete the entire |
1136 | * internal array. |
1137 | */ |
1138 | if (array->nr_leaves_on_tree == 1) { |
1139 | edit->set[1].ptr = &array->root; |
1140 | edit->set[1].to = NULL; |
1141 | edit->adjust_count_on = NULL; |
1142 | edit->excised_subtree = array->root; |
1143 | pr_devel("all gone\n" ); |
1144 | return edit; |
1145 | } |
1146 | |
1147 | /* However, we'd also like to clear up some metadata blocks if we |
1148 | * possibly can. |
1149 | * |
1150 | * We go for a simple algorithm of: if this node has FAN_OUT or fewer |
1151 | * leaves in it, then attempt to collapse it - and attempt to |
1152 | * recursively collapse up the tree. |
1153 | * |
1154 | * We could also try and collapse in partially filled subtrees to take |
1155 | * up space in this node. |
1156 | */ |
1157 | if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { |
1158 | struct assoc_array_node *parent, *grandparent; |
1159 | struct assoc_array_ptr *ptr; |
1160 | |
1161 | /* First of all, we need to know if this node has metadata so |
1162 | * that we don't try collapsing if all the leaves are already |
1163 | * here. |
1164 | */ |
1165 | has_meta = false; |
1166 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
1167 | ptr = node->slots[i]; |
1168 | if (assoc_array_ptr_is_meta(x: ptr)) { |
1169 | has_meta = true; |
1170 | break; |
1171 | } |
1172 | } |
1173 | |
1174 | pr_devel("leaves: %ld [m=%d]\n" , |
1175 | node->nr_leaves_on_branch - 1, has_meta); |
1176 | |
1177 | /* Look further up the tree to see if we can collapse this node |
1178 | * into a more proximal node too. |
1179 | */ |
1180 | parent = node; |
1181 | collapse_up: |
1182 | pr_devel("collapse subtree: %ld\n" , parent->nr_leaves_on_branch); |
1183 | |
1184 | ptr = parent->back_pointer; |
1185 | if (!ptr) |
1186 | goto do_collapse; |
1187 | if (assoc_array_ptr_is_shortcut(x: ptr)) { |
1188 | struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(x: ptr); |
1189 | ptr = s->back_pointer; |
1190 | if (!ptr) |
1191 | goto do_collapse; |
1192 | } |
1193 | |
1194 | grandparent = assoc_array_ptr_to_node(x: ptr); |
1195 | if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { |
1196 | parent = grandparent; |
1197 | goto collapse_up; |
1198 | } |
1199 | |
1200 | do_collapse: |
1201 | /* There's no point collapsing if the original node has no meta |
1202 | * pointers to discard and if we didn't merge into one of that |
1203 | * node's ancestry. |
1204 | */ |
1205 | if (has_meta || parent != node) { |
1206 | node = parent; |
1207 | |
1208 | /* Create a new node to collapse into */ |
1209 | new_n0 = kzalloc(size: sizeof(struct assoc_array_node), GFP_KERNEL); |
1210 | if (!new_n0) |
1211 | goto enomem; |
1212 | edit->new_meta[0] = assoc_array_node_to_ptr(p: new_n0); |
1213 | |
1214 | new_n0->back_pointer = node->back_pointer; |
1215 | new_n0->parent_slot = node->parent_slot; |
1216 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; |
1217 | edit->adjust_count_on = new_n0; |
1218 | |
1219 | collapse.node = new_n0; |
1220 | collapse.skip_leaf = assoc_array_ptr_to_leaf(x: edit->dead_leaf); |
1221 | collapse.slot = 0; |
1222 | assoc_array_subtree_iterate(root: assoc_array_node_to_ptr(p: node), |
1223 | stop: node->back_pointer, |
1224 | iterator: assoc_array_delete_collapse_iterator, |
1225 | iterator_data: &collapse); |
1226 | pr_devel("collapsed %d,%lu\n" , collapse.slot, new_n0->nr_leaves_on_branch); |
1227 | BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1); |
1228 | |
1229 | if (!node->back_pointer) { |
1230 | edit->set[1].ptr = &array->root; |
1231 | } else if (assoc_array_ptr_is_leaf(x: node->back_pointer)) { |
1232 | BUG(); |
1233 | } else if (assoc_array_ptr_is_node(x: node->back_pointer)) { |
1234 | struct assoc_array_node *p = |
1235 | assoc_array_ptr_to_node(x: node->back_pointer); |
1236 | edit->set[1].ptr = &p->slots[node->parent_slot]; |
1237 | } else if (assoc_array_ptr_is_shortcut(x: node->back_pointer)) { |
1238 | struct assoc_array_shortcut *s = |
1239 | assoc_array_ptr_to_shortcut(x: node->back_pointer); |
1240 | edit->set[1].ptr = &s->next_node; |
1241 | } |
1242 | edit->set[1].to = assoc_array_node_to_ptr(p: new_n0); |
1243 | edit->excised_subtree = assoc_array_node_to_ptr(p: node); |
1244 | } |
1245 | } |
1246 | |
1247 | return edit; |
1248 | |
1249 | enomem: |
1250 | /* Clean up after an out of memory error */ |
1251 | pr_devel("enomem\n" ); |
1252 | assoc_array_cancel_edit(edit); |
1253 | return ERR_PTR(error: -ENOMEM); |
1254 | } |
1255 | |
1256 | /** |
1257 | * assoc_array_clear - Script deletion of all objects from an associative array |
1258 | * @array: The array to clear. |
1259 | * @ops: The operations to use. |
1260 | * |
1261 | * Precalculate and preallocate a script for the deletion of all the objects |
1262 | * from an associative array. This results in an edit script that can either |
1263 | * be applied or cancelled. |
1264 | * |
1265 | * The function returns a pointer to an edit script if there are objects to be |
1266 | * deleted, NULL if there are no objects in the array or -ENOMEM. |
1267 | * |
1268 | * The caller should lock against other modifications and must continue to hold |
1269 | * the lock until assoc_array_apply_edit() has been called. |
1270 | * |
1271 | * Accesses to the tree may take place concurrently with this function, |
1272 | * provided they hold the RCU read lock. |
1273 | */ |
1274 | struct assoc_array_edit *assoc_array_clear(struct assoc_array *array, |
1275 | const struct assoc_array_ops *ops) |
1276 | { |
1277 | struct assoc_array_edit *edit; |
1278 | |
1279 | pr_devel("-->%s()\n" , __func__); |
1280 | |
1281 | if (!array->root) |
1282 | return NULL; |
1283 | |
1284 | edit = kzalloc(size: sizeof(struct assoc_array_edit), GFP_KERNEL); |
1285 | if (!edit) |
1286 | return ERR_PTR(error: -ENOMEM); |
1287 | edit->array = array; |
1288 | edit->ops = ops; |
1289 | edit->set[1].ptr = &array->root; |
1290 | edit->set[1].to = NULL; |
1291 | edit->excised_subtree = array->root; |
1292 | edit->ops_for_excised_subtree = ops; |
1293 | pr_devel("all gone\n" ); |
1294 | return edit; |
1295 | } |
1296 | |
1297 | /* |
1298 | * Handle the deferred destruction after an applied edit. |
1299 | */ |
1300 | static void assoc_array_rcu_cleanup(struct rcu_head *head) |
1301 | { |
1302 | struct assoc_array_edit *edit = |
1303 | container_of(head, struct assoc_array_edit, rcu); |
1304 | int i; |
1305 | |
1306 | pr_devel("-->%s()\n" , __func__); |
1307 | |
1308 | if (edit->dead_leaf) |
1309 | edit->ops->free_object(assoc_array_ptr_to_leaf(x: edit->dead_leaf)); |
1310 | for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++) |
1311 | if (edit->excised_meta[i]) |
1312 | kfree(objp: assoc_array_ptr_to_node(x: edit->excised_meta[i])); |
1313 | |
1314 | if (edit->excised_subtree) { |
1315 | BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree)); |
1316 | if (assoc_array_ptr_is_node(x: edit->excised_subtree)) { |
1317 | struct assoc_array_node *n = |
1318 | assoc_array_ptr_to_node(x: edit->excised_subtree); |
1319 | n->back_pointer = NULL; |
1320 | } else { |
1321 | struct assoc_array_shortcut *s = |
1322 | assoc_array_ptr_to_shortcut(x: edit->excised_subtree); |
1323 | s->back_pointer = NULL; |
1324 | } |
1325 | assoc_array_destroy_subtree(root: edit->excised_subtree, |
1326 | ops: edit->ops_for_excised_subtree); |
1327 | } |
1328 | |
1329 | kfree(objp: edit); |
1330 | } |
1331 | |
1332 | /** |
1333 | * assoc_array_apply_edit - Apply an edit script to an associative array |
1334 | * @edit: The script to apply. |
1335 | * |
1336 | * Apply an edit script to an associative array to effect an insertion, |
1337 | * deletion or clearance. As the edit script includes preallocated memory, |
1338 | * this is guaranteed not to fail. |
1339 | * |
1340 | * The edit script, dead objects and dead metadata will be scheduled for |
1341 | * destruction after an RCU grace period to permit those doing read-only |
1342 | * accesses on the array to continue to do so under the RCU read lock whilst |
1343 | * the edit is taking place. |
1344 | */ |
1345 | void assoc_array_apply_edit(struct assoc_array_edit *edit) |
1346 | { |
1347 | struct assoc_array_shortcut *shortcut; |
1348 | struct assoc_array_node *node; |
1349 | struct assoc_array_ptr *ptr; |
1350 | int i; |
1351 | |
1352 | pr_devel("-->%s()\n" , __func__); |
1353 | |
1354 | smp_wmb(); |
1355 | if (edit->leaf_p) |
1356 | *edit->leaf_p = edit->leaf; |
1357 | |
1358 | smp_wmb(); |
1359 | for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++) |
1360 | if (edit->set_parent_slot[i].p) |
1361 | *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to; |
1362 | |
1363 | smp_wmb(); |
1364 | for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++) |
1365 | if (edit->set_backpointers[i]) |
1366 | *edit->set_backpointers[i] = edit->set_backpointers_to; |
1367 | |
1368 | smp_wmb(); |
1369 | for (i = 0; i < ARRAY_SIZE(edit->set); i++) |
1370 | if (edit->set[i].ptr) |
1371 | *edit->set[i].ptr = edit->set[i].to; |
1372 | |
1373 | if (edit->array->root == NULL) { |
1374 | edit->array->nr_leaves_on_tree = 0; |
1375 | } else if (edit->adjust_count_on) { |
1376 | node = edit->adjust_count_on; |
1377 | for (;;) { |
1378 | node->nr_leaves_on_branch += edit->adjust_count_by; |
1379 | |
1380 | ptr = node->back_pointer; |
1381 | if (!ptr) |
1382 | break; |
1383 | if (assoc_array_ptr_is_shortcut(x: ptr)) { |
1384 | shortcut = assoc_array_ptr_to_shortcut(x: ptr); |
1385 | ptr = shortcut->back_pointer; |
1386 | if (!ptr) |
1387 | break; |
1388 | } |
1389 | BUG_ON(!assoc_array_ptr_is_node(ptr)); |
1390 | node = assoc_array_ptr_to_node(x: ptr); |
1391 | } |
1392 | |
1393 | edit->array->nr_leaves_on_tree += edit->adjust_count_by; |
1394 | } |
1395 | |
1396 | call_rcu(head: &edit->rcu, func: assoc_array_rcu_cleanup); |
1397 | } |
1398 | |
1399 | /** |
1400 | * assoc_array_cancel_edit - Discard an edit script. |
1401 | * @edit: The script to discard. |
1402 | * |
1403 | * Free an edit script and all the preallocated data it holds without making |
1404 | * any changes to the associative array it was intended for. |
1405 | * |
1406 | * NOTE! In the case of an insertion script, this does _not_ release the leaf |
1407 | * that was to be inserted. That is left to the caller. |
1408 | */ |
1409 | void assoc_array_cancel_edit(struct assoc_array_edit *edit) |
1410 | { |
1411 | struct assoc_array_ptr *ptr; |
1412 | int i; |
1413 | |
1414 | pr_devel("-->%s()\n" , __func__); |
1415 | |
1416 | /* Clean up after an out of memory error */ |
1417 | for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) { |
1418 | ptr = edit->new_meta[i]; |
1419 | if (ptr) { |
1420 | if (assoc_array_ptr_is_node(x: ptr)) |
1421 | kfree(objp: assoc_array_ptr_to_node(x: ptr)); |
1422 | else |
1423 | kfree(objp: assoc_array_ptr_to_shortcut(x: ptr)); |
1424 | } |
1425 | } |
1426 | kfree(objp: edit); |
1427 | } |
1428 | |
1429 | /** |
1430 | * assoc_array_gc - Garbage collect an associative array. |
1431 | * @array: The array to clean. |
1432 | * @ops: The operations to use. |
1433 | * @iterator: A callback function to pass judgement on each object. |
1434 | * @iterator_data: Private data for the callback function. |
1435 | * |
1436 | * Collect garbage from an associative array and pack down the internal tree to |
1437 | * save memory. |
1438 | * |
1439 | * The iterator function is asked to pass judgement upon each object in the |
1440 | * array. If it returns false, the object is discard and if it returns true, |
1441 | * the object is kept. If it returns true, it must increment the object's |
1442 | * usage count (or whatever it needs to do to retain it) before returning. |
1443 | * |
1444 | * This function returns 0 if successful or -ENOMEM if out of memory. In the |
1445 | * latter case, the array is not changed. |
1446 | * |
1447 | * The caller should lock against other modifications and must continue to hold |
1448 | * the lock until assoc_array_apply_edit() has been called. |
1449 | * |
1450 | * Accesses to the tree may take place concurrently with this function, |
1451 | * provided they hold the RCU read lock. |
1452 | */ |
1453 | int assoc_array_gc(struct assoc_array *array, |
1454 | const struct assoc_array_ops *ops, |
1455 | bool (*iterator)(void *object, void *iterator_data), |
1456 | void *iterator_data) |
1457 | { |
1458 | struct assoc_array_shortcut *shortcut, *new_s; |
1459 | struct assoc_array_node *node, *new_n; |
1460 | struct assoc_array_edit *edit; |
1461 | struct assoc_array_ptr *cursor, *ptr; |
1462 | struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp; |
1463 | unsigned long nr_leaves_on_tree; |
1464 | bool retained; |
1465 | int keylen, slot, nr_free, next_slot, i; |
1466 | |
1467 | pr_devel("-->%s()\n" , __func__); |
1468 | |
1469 | if (!array->root) |
1470 | return 0; |
1471 | |
1472 | edit = kzalloc(size: sizeof(struct assoc_array_edit), GFP_KERNEL); |
1473 | if (!edit) |
1474 | return -ENOMEM; |
1475 | edit->array = array; |
1476 | edit->ops = ops; |
1477 | edit->ops_for_excised_subtree = ops; |
1478 | edit->set[0].ptr = &array->root; |
1479 | edit->excised_subtree = array->root; |
1480 | |
1481 | new_root = new_parent = NULL; |
1482 | new_ptr_pp = &new_root; |
1483 | cursor = array->root; |
1484 | |
1485 | descend: |
1486 | /* If this point is a shortcut, then we need to duplicate it and |
1487 | * advance the target cursor. |
1488 | */ |
1489 | if (assoc_array_ptr_is_shortcut(x: cursor)) { |
1490 | shortcut = assoc_array_ptr_to_shortcut(x: cursor); |
1491 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
1492 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
1493 | new_s = kmalloc(struct_size(new_s, index_key, keylen), |
1494 | GFP_KERNEL); |
1495 | if (!new_s) |
1496 | goto enomem; |
1497 | pr_devel("dup shortcut %p -> %p\n" , shortcut, new_s); |
1498 | memcpy(new_s, shortcut, struct_size(new_s, index_key, keylen)); |
1499 | new_s->back_pointer = new_parent; |
1500 | new_s->parent_slot = shortcut->parent_slot; |
1501 | *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(p: new_s); |
1502 | new_ptr_pp = &new_s->next_node; |
1503 | cursor = shortcut->next_node; |
1504 | } |
1505 | |
1506 | /* Duplicate the node at this position */ |
1507 | node = assoc_array_ptr_to_node(x: cursor); |
1508 | new_n = kzalloc(size: sizeof(struct assoc_array_node), GFP_KERNEL); |
1509 | if (!new_n) |
1510 | goto enomem; |
1511 | pr_devel("dup node %p -> %p\n" , node, new_n); |
1512 | new_n->back_pointer = new_parent; |
1513 | new_n->parent_slot = node->parent_slot; |
1514 | *new_ptr_pp = new_parent = assoc_array_node_to_ptr(p: new_n); |
1515 | new_ptr_pp = NULL; |
1516 | slot = 0; |
1517 | |
1518 | continue_node: |
1519 | /* Filter across any leaves and gc any subtrees */ |
1520 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1521 | ptr = node->slots[slot]; |
1522 | if (!ptr) |
1523 | continue; |
1524 | |
1525 | if (assoc_array_ptr_is_leaf(x: ptr)) { |
1526 | if (iterator(assoc_array_ptr_to_leaf(x: ptr), |
1527 | iterator_data)) |
1528 | /* The iterator will have done any reference |
1529 | * counting on the object for us. |
1530 | */ |
1531 | new_n->slots[slot] = ptr; |
1532 | continue; |
1533 | } |
1534 | |
1535 | new_ptr_pp = &new_n->slots[slot]; |
1536 | cursor = ptr; |
1537 | goto descend; |
1538 | } |
1539 | |
1540 | retry_compress: |
1541 | pr_devel("-- compress node %p --\n" , new_n); |
1542 | |
1543 | /* Count up the number of empty slots in this node and work out the |
1544 | * subtree leaf count. |
1545 | */ |
1546 | new_n->nr_leaves_on_branch = 0; |
1547 | nr_free = 0; |
1548 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1549 | ptr = new_n->slots[slot]; |
1550 | if (!ptr) |
1551 | nr_free++; |
1552 | else if (assoc_array_ptr_is_leaf(x: ptr)) |
1553 | new_n->nr_leaves_on_branch++; |
1554 | } |
1555 | pr_devel("free=%d, leaves=%lu\n" , nr_free, new_n->nr_leaves_on_branch); |
1556 | |
1557 | /* See what we can fold in */ |
1558 | retained = false; |
1559 | next_slot = 0; |
1560 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
1561 | struct assoc_array_shortcut *s; |
1562 | struct assoc_array_node *child; |
1563 | |
1564 | ptr = new_n->slots[slot]; |
1565 | if (!ptr || assoc_array_ptr_is_leaf(x: ptr)) |
1566 | continue; |
1567 | |
1568 | s = NULL; |
1569 | if (assoc_array_ptr_is_shortcut(x: ptr)) { |
1570 | s = assoc_array_ptr_to_shortcut(x: ptr); |
1571 | ptr = s->next_node; |
1572 | } |
1573 | |
1574 | child = assoc_array_ptr_to_node(x: ptr); |
1575 | new_n->nr_leaves_on_branch += child->nr_leaves_on_branch; |
1576 | |
1577 | if (child->nr_leaves_on_branch <= nr_free + 1) { |
1578 | /* Fold the child node into this one */ |
1579 | pr_devel("[%d] fold node %lu/%d [nx %d]\n" , |
1580 | slot, child->nr_leaves_on_branch, nr_free + 1, |
1581 | next_slot); |
1582 | |
1583 | /* We would already have reaped an intervening shortcut |
1584 | * on the way back up the tree. |
1585 | */ |
1586 | BUG_ON(s); |
1587 | |
1588 | new_n->slots[slot] = NULL; |
1589 | nr_free++; |
1590 | if (slot < next_slot) |
1591 | next_slot = slot; |
1592 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
1593 | struct assoc_array_ptr *p = child->slots[i]; |
1594 | if (!p) |
1595 | continue; |
1596 | BUG_ON(assoc_array_ptr_is_meta(p)); |
1597 | while (new_n->slots[next_slot]) |
1598 | next_slot++; |
1599 | BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT); |
1600 | new_n->slots[next_slot++] = p; |
1601 | nr_free--; |
1602 | } |
1603 | kfree(objp: child); |
1604 | } else { |
1605 | pr_devel("[%d] retain node %lu/%d [nx %d]\n" , |
1606 | slot, child->nr_leaves_on_branch, nr_free + 1, |
1607 | next_slot); |
1608 | retained = true; |
1609 | } |
1610 | } |
1611 | |
1612 | if (retained && new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { |
1613 | pr_devel("internal nodes remain despite enough space, retrying\n" ); |
1614 | goto retry_compress; |
1615 | } |
1616 | pr_devel("after: %lu\n" , new_n->nr_leaves_on_branch); |
1617 | |
1618 | nr_leaves_on_tree = new_n->nr_leaves_on_branch; |
1619 | |
1620 | /* Excise this node if it is singly occupied by a shortcut */ |
1621 | if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) { |
1622 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) |
1623 | if ((ptr = new_n->slots[slot])) |
1624 | break; |
1625 | |
1626 | if (assoc_array_ptr_is_meta(x: ptr) && |
1627 | assoc_array_ptr_is_shortcut(x: ptr)) { |
1628 | pr_devel("excise node %p with 1 shortcut\n" , new_n); |
1629 | new_s = assoc_array_ptr_to_shortcut(x: ptr); |
1630 | new_parent = new_n->back_pointer; |
1631 | slot = new_n->parent_slot; |
1632 | kfree(objp: new_n); |
1633 | if (!new_parent) { |
1634 | new_s->back_pointer = NULL; |
1635 | new_s->parent_slot = 0; |
1636 | new_root = ptr; |
1637 | goto gc_complete; |
1638 | } |
1639 | |
1640 | if (assoc_array_ptr_is_shortcut(x: new_parent)) { |
1641 | /* We can discard any preceding shortcut also */ |
1642 | struct assoc_array_shortcut *s = |
1643 | assoc_array_ptr_to_shortcut(x: new_parent); |
1644 | |
1645 | pr_devel("excise preceding shortcut\n" ); |
1646 | |
1647 | new_parent = new_s->back_pointer = s->back_pointer; |
1648 | slot = new_s->parent_slot = s->parent_slot; |
1649 | kfree(objp: s); |
1650 | if (!new_parent) { |
1651 | new_s->back_pointer = NULL; |
1652 | new_s->parent_slot = 0; |
1653 | new_root = ptr; |
1654 | goto gc_complete; |
1655 | } |
1656 | } |
1657 | |
1658 | new_s->back_pointer = new_parent; |
1659 | new_s->parent_slot = slot; |
1660 | new_n = assoc_array_ptr_to_node(x: new_parent); |
1661 | new_n->slots[slot] = ptr; |
1662 | goto ascend_old_tree; |
1663 | } |
1664 | } |
1665 | |
1666 | /* Excise any shortcuts we might encounter that point to nodes that |
1667 | * only contain leaves. |
1668 | */ |
1669 | ptr = new_n->back_pointer; |
1670 | if (!ptr) |
1671 | goto gc_complete; |
1672 | |
1673 | if (assoc_array_ptr_is_shortcut(x: ptr)) { |
1674 | new_s = assoc_array_ptr_to_shortcut(x: ptr); |
1675 | new_parent = new_s->back_pointer; |
1676 | slot = new_s->parent_slot; |
1677 | |
1678 | if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { |
1679 | struct assoc_array_node *n; |
1680 | |
1681 | pr_devel("excise shortcut\n" ); |
1682 | new_n->back_pointer = new_parent; |
1683 | new_n->parent_slot = slot; |
1684 | kfree(objp: new_s); |
1685 | if (!new_parent) { |
1686 | new_root = assoc_array_node_to_ptr(p: new_n); |
1687 | goto gc_complete; |
1688 | } |
1689 | |
1690 | n = assoc_array_ptr_to_node(x: new_parent); |
1691 | n->slots[slot] = assoc_array_node_to_ptr(p: new_n); |
1692 | } |
1693 | } else { |
1694 | new_parent = ptr; |
1695 | } |
1696 | new_n = assoc_array_ptr_to_node(x: new_parent); |
1697 | |
1698 | ascend_old_tree: |
1699 | ptr = node->back_pointer; |
1700 | if (assoc_array_ptr_is_shortcut(x: ptr)) { |
1701 | shortcut = assoc_array_ptr_to_shortcut(x: ptr); |
1702 | slot = shortcut->parent_slot; |
1703 | cursor = shortcut->back_pointer; |
1704 | if (!cursor) |
1705 | goto gc_complete; |
1706 | } else { |
1707 | slot = node->parent_slot; |
1708 | cursor = ptr; |
1709 | } |
1710 | BUG_ON(!cursor); |
1711 | node = assoc_array_ptr_to_node(x: cursor); |
1712 | slot++; |
1713 | goto continue_node; |
1714 | |
1715 | gc_complete: |
1716 | edit->set[0].to = new_root; |
1717 | assoc_array_apply_edit(edit); |
1718 | array->nr_leaves_on_tree = nr_leaves_on_tree; |
1719 | return 0; |
1720 | |
1721 | enomem: |
1722 | pr_devel("enomem\n" ); |
1723 | assoc_array_destroy_subtree(root: new_root, ops: edit->ops); |
1724 | kfree(objp: edit); |
1725 | return -ENOMEM; |
1726 | } |
1727 | |