David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 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 |
Pranith Kumar | 990428b | 2014-12-30 00:46:21 -0500 | [diff] [blame] | 14 | #include <linux/rcupdate.h> |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 15 | #include <linux/slab.h> |
David Howells | b2a4df2 | 2013-09-24 10:35:18 +0100 | [diff] [blame] | 16 | #include <linux/err.h> |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 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, |
Stephen Hemminger | 30b02c4b | 2014-01-23 13:24:09 +0000 | [diff] [blame] | 161 | }; |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 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 | } |
Jerome Marchand | 8d4a2ec | 2016-04-06 14:06:48 +0100 | [diff] [blame] | 527 | if (assoc_array_ptr_is_leaf(ptr) && |
| 528 | ops->compare_object(assoc_array_ptr_to_leaf(ptr), |
| 529 | index_key)) { |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 530 | pr_devel("replace in slot %d\n", i); |
| 531 | edit->leaf_p = &node->slots[i]; |
| 532 | edit->dead_leaf = node->slots[i]; |
| 533 | pr_devel("<--%s() = ok [replace]\n", __func__); |
| 534 | return true; |
| 535 | } |
| 536 | } |
| 537 | |
| 538 | /* If there is a free slot in this node then we can just insert the |
| 539 | * leaf here. |
| 540 | */ |
| 541 | if (free_slot >= 0) { |
| 542 | pr_devel("insert in free slot %d\n", free_slot); |
| 543 | edit->leaf_p = &node->slots[free_slot]; |
| 544 | edit->adjust_count_on = node; |
| 545 | pr_devel("<--%s() = ok [insert]\n", __func__); |
| 546 | return true; |
| 547 | } |
| 548 | |
| 549 | /* The node has no spare slots - so we're either going to have to split |
| 550 | * it or insert another node before it. |
| 551 | * |
| 552 | * Whatever, we're going to need at least two new nodes - so allocate |
| 553 | * those now. We may also need a new shortcut, but we deal with that |
| 554 | * when we need it. |
| 555 | */ |
| 556 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
| 557 | if (!new_n0) |
| 558 | return false; |
| 559 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); |
| 560 | new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
| 561 | if (!new_n1) |
| 562 | return false; |
| 563 | edit->new_meta[1] = assoc_array_node_to_ptr(new_n1); |
| 564 | |
| 565 | /* We need to find out how similar the leaves are. */ |
| 566 | pr_devel("no spare slots\n"); |
| 567 | have_meta = false; |
| 568 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 569 | ptr = node->slots[i]; |
| 570 | if (assoc_array_ptr_is_meta(ptr)) { |
| 571 | edit->segment_cache[i] = 0xff; |
| 572 | have_meta = true; |
| 573 | continue; |
| 574 | } |
| 575 | base_seg = ops->get_object_key_chunk( |
| 576 | assoc_array_ptr_to_leaf(ptr), level); |
| 577 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
| 578 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; |
| 579 | } |
| 580 | |
| 581 | if (have_meta) { |
| 582 | pr_devel("have meta\n"); |
| 583 | goto split_node; |
| 584 | } |
| 585 | |
| 586 | /* The node contains only leaves */ |
| 587 | dissimilarity = 0; |
| 588 | base_seg = edit->segment_cache[0]; |
| 589 | for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++) |
| 590 | dissimilarity |= edit->segment_cache[i] ^ base_seg; |
| 591 | |
| 592 | pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity); |
| 593 | |
| 594 | if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) { |
| 595 | /* The old leaves all cluster in the same slot. We will need |
| 596 | * to insert a shortcut if the new node wants to cluster with them. |
| 597 | */ |
| 598 | if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0) |
| 599 | goto all_leaves_cluster_together; |
| 600 | |
| 601 | /* Otherwise we can just insert a new node ahead of the old |
| 602 | * one. |
| 603 | */ |
| 604 | goto present_leaves_cluster_but_not_new_leaf; |
| 605 | } |
| 606 | |
| 607 | split_node: |
| 608 | pr_devel("split node\n"); |
| 609 | |
| 610 | /* We need to split the current node; we know that the node doesn't |
| 611 | * simply contain a full set of leaves that cluster together (it |
| 612 | * contains meta pointers and/or non-clustering leaves). |
| 613 | * |
| 614 | * We need to expel at least two leaves out of a set consisting of the |
| 615 | * leaves in the node and the new leaf. |
| 616 | * |
| 617 | * We need a new node (n0) to replace the current one and a new node to |
| 618 | * take the expelled nodes (n1). |
| 619 | */ |
| 620 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); |
| 621 | new_n0->back_pointer = node->back_pointer; |
| 622 | new_n0->parent_slot = node->parent_slot; |
| 623 | new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); |
| 624 | new_n1->parent_slot = -1; /* Need to calculate this */ |
| 625 | |
| 626 | do_split_node: |
| 627 | pr_devel("do_split_node\n"); |
| 628 | |
| 629 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; |
| 630 | new_n1->nr_leaves_on_branch = 0; |
| 631 | |
| 632 | /* Begin by finding two matching leaves. There have to be at least two |
| 633 | * that match - even if there are meta pointers - because any leaf that |
| 634 | * would match a slot with a meta pointer in it must be somewhere |
| 635 | * behind that meta pointer and cannot be here. Further, given N |
| 636 | * remaining leaf slots, we now have N+1 leaves to go in them. |
| 637 | */ |
| 638 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 639 | slot = edit->segment_cache[i]; |
| 640 | if (slot != 0xff) |
| 641 | for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++) |
| 642 | if (edit->segment_cache[j] == slot) |
| 643 | goto found_slot_for_multiple_occupancy; |
| 644 | } |
| 645 | found_slot_for_multiple_occupancy: |
| 646 | pr_devel("same slot: %x %x [%02x]\n", i, j, slot); |
| 647 | BUG_ON(i >= ASSOC_ARRAY_FAN_OUT); |
| 648 | BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1); |
| 649 | BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT); |
| 650 | |
| 651 | new_n1->parent_slot = slot; |
| 652 | |
| 653 | /* Metadata pointers cannot change slot */ |
| 654 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) |
| 655 | if (assoc_array_ptr_is_meta(node->slots[i])) |
| 656 | new_n0->slots[i] = node->slots[i]; |
| 657 | else |
| 658 | new_n0->slots[i] = NULL; |
| 659 | BUG_ON(new_n0->slots[slot] != NULL); |
| 660 | new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1); |
| 661 | |
| 662 | /* Filter the leaf pointers between the new nodes */ |
| 663 | free_slot = -1; |
| 664 | next_slot = 0; |
| 665 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 666 | if (assoc_array_ptr_is_meta(node->slots[i])) |
| 667 | continue; |
| 668 | if (edit->segment_cache[i] == slot) { |
| 669 | new_n1->slots[next_slot++] = node->slots[i]; |
| 670 | new_n1->nr_leaves_on_branch++; |
| 671 | } else { |
| 672 | do { |
| 673 | free_slot++; |
| 674 | } while (new_n0->slots[free_slot] != NULL); |
| 675 | new_n0->slots[free_slot] = node->slots[i]; |
| 676 | } |
| 677 | } |
| 678 | |
| 679 | pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot); |
| 680 | |
| 681 | if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) { |
| 682 | do { |
| 683 | free_slot++; |
| 684 | } while (new_n0->slots[free_slot] != NULL); |
| 685 | edit->leaf_p = &new_n0->slots[free_slot]; |
| 686 | edit->adjust_count_on = new_n0; |
| 687 | } else { |
| 688 | edit->leaf_p = &new_n1->slots[next_slot++]; |
| 689 | edit->adjust_count_on = new_n1; |
| 690 | } |
| 691 | |
| 692 | BUG_ON(next_slot <= 1); |
| 693 | |
| 694 | edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0); |
| 695 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 696 | if (edit->segment_cache[i] == 0xff) { |
| 697 | ptr = node->slots[i]; |
| 698 | BUG_ON(assoc_array_ptr_is_leaf(ptr)); |
| 699 | if (assoc_array_ptr_is_node(ptr)) { |
| 700 | side = assoc_array_ptr_to_node(ptr); |
| 701 | edit->set_backpointers[i] = &side->back_pointer; |
| 702 | } else { |
| 703 | shortcut = assoc_array_ptr_to_shortcut(ptr); |
| 704 | edit->set_backpointers[i] = &shortcut->back_pointer; |
| 705 | } |
| 706 | } |
| 707 | } |
| 708 | |
| 709 | ptr = node->back_pointer; |
| 710 | if (!ptr) |
| 711 | edit->set[0].ptr = &edit->array->root; |
| 712 | else if (assoc_array_ptr_is_node(ptr)) |
| 713 | edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot]; |
| 714 | else |
| 715 | edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node; |
| 716 | edit->excised_meta[0] = assoc_array_node_to_ptr(node); |
| 717 | pr_devel("<--%s() = ok [split node]\n", __func__); |
| 718 | return true; |
| 719 | |
| 720 | present_leaves_cluster_but_not_new_leaf: |
| 721 | /* All the old leaves cluster in the same slot, but the new leaf wants |
| 722 | * to go into a different slot, so we create a new node to hold the new |
| 723 | * leaf and a pointer to a new node holding all the old leaves. |
| 724 | */ |
| 725 | pr_devel("present leaves cluster but not new leaf\n"); |
| 726 | |
| 727 | new_n0->back_pointer = node->back_pointer; |
| 728 | new_n0->parent_slot = node->parent_slot; |
| 729 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; |
| 730 | new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); |
| 731 | new_n1->parent_slot = edit->segment_cache[0]; |
| 732 | new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch; |
| 733 | edit->adjust_count_on = new_n0; |
| 734 | |
| 735 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) |
| 736 | new_n1->slots[i] = node->slots[i]; |
| 737 | |
| 738 | new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0); |
| 739 | edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]]; |
| 740 | |
| 741 | edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot]; |
| 742 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); |
| 743 | edit->excised_meta[0] = assoc_array_node_to_ptr(node); |
| 744 | pr_devel("<--%s() = ok [insert node before]\n", __func__); |
| 745 | return true; |
| 746 | |
| 747 | all_leaves_cluster_together: |
| 748 | /* All the leaves, new and old, want to cluster together in this node |
| 749 | * in the same slot, so we have to replace this node with a shortcut to |
| 750 | * skip over the identical parts of the key and then place a pair of |
| 751 | * nodes, one inside the other, at the end of the shortcut and |
| 752 | * distribute the keys between them. |
| 753 | * |
| 754 | * Firstly we need to work out where the leaves start diverging as a |
| 755 | * bit position into their keys so that we know how big the shortcut |
| 756 | * needs to be. |
| 757 | * |
| 758 | * We only need to make a single pass of N of the N+1 leaves because if |
| 759 | * any keys differ between themselves at bit X then at least one of |
| 760 | * them must also differ with the base key at bit X or before. |
| 761 | */ |
| 762 | pr_devel("all leaves cluster together\n"); |
| 763 | diff = INT_MAX; |
| 764 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
David Howells | 23fd78d | 2013-12-02 11:24:18 +0000 | [diff] [blame] | 765 | int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]), |
| 766 | index_key); |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 767 | if (x < diff) { |
| 768 | BUG_ON(x < 0); |
| 769 | diff = x; |
| 770 | } |
| 771 | } |
| 772 | BUG_ON(diff == INT_MAX); |
| 773 | BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP); |
| 774 | |
| 775 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
| 776 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
| 777 | |
| 778 | new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + |
| 779 | keylen * sizeof(unsigned long), GFP_KERNEL); |
| 780 | if (!new_s0) |
| 781 | return false; |
| 782 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0); |
| 783 | |
| 784 | edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); |
| 785 | new_s0->back_pointer = node->back_pointer; |
| 786 | new_s0->parent_slot = node->parent_slot; |
| 787 | new_s0->next_node = assoc_array_node_to_ptr(new_n0); |
| 788 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); |
| 789 | new_n0->parent_slot = 0; |
| 790 | new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); |
| 791 | new_n1->parent_slot = -1; /* Need to calculate this */ |
| 792 | |
| 793 | new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK; |
| 794 | pr_devel("skip_to_level = %d [diff %d]\n", level, diff); |
| 795 | BUG_ON(level <= 0); |
| 796 | |
| 797 | for (i = 0; i < keylen; i++) |
| 798 | new_s0->index_key[i] = |
| 799 | ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE); |
| 800 | |
| 801 | blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); |
| 802 | pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); |
| 803 | new_s0->index_key[keylen - 1] &= ~blank; |
| 804 | |
| 805 | /* This now reduces to a node splitting exercise for which we'll need |
| 806 | * to regenerate the disparity table. |
| 807 | */ |
| 808 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 809 | ptr = node->slots[i]; |
| 810 | base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr), |
| 811 | level); |
| 812 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
| 813 | edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; |
| 814 | } |
| 815 | |
| 816 | base_seg = ops->get_key_chunk(index_key, level); |
| 817 | base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; |
| 818 | edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK; |
| 819 | goto do_split_node; |
| 820 | } |
| 821 | |
| 822 | /* |
| 823 | * Handle insertion into the middle of a shortcut. |
| 824 | */ |
| 825 | static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit, |
| 826 | const struct assoc_array_ops *ops, |
| 827 | struct assoc_array_walk_result *result) |
| 828 | { |
| 829 | struct assoc_array_shortcut *shortcut, *new_s0, *new_s1; |
| 830 | struct assoc_array_node *node, *new_n0, *side; |
| 831 | unsigned long sc_segments, dissimilarity, blank; |
| 832 | size_t keylen; |
| 833 | int level, sc_level, diff; |
| 834 | int sc_slot; |
| 835 | |
| 836 | shortcut = result->wrong_shortcut.shortcut; |
| 837 | level = result->wrong_shortcut.level; |
| 838 | sc_level = result->wrong_shortcut.sc_level; |
| 839 | sc_segments = result->wrong_shortcut.sc_segments; |
| 840 | dissimilarity = result->wrong_shortcut.dissimilarity; |
| 841 | |
| 842 | pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n", |
| 843 | __func__, level, dissimilarity, sc_level); |
| 844 | |
| 845 | /* We need to split a shortcut and insert a node between the two |
| 846 | * pieces. Zero-length pieces will be dispensed with entirely. |
| 847 | * |
| 848 | * First of all, we need to find out in which level the first |
| 849 | * difference was. |
| 850 | */ |
| 851 | diff = __ffs(dissimilarity); |
| 852 | diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK; |
| 853 | diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK; |
| 854 | pr_devel("diff=%d\n", diff); |
| 855 | |
| 856 | if (!shortcut->back_pointer) { |
| 857 | edit->set[0].ptr = &edit->array->root; |
| 858 | } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) { |
| 859 | node = assoc_array_ptr_to_node(shortcut->back_pointer); |
| 860 | edit->set[0].ptr = &node->slots[shortcut->parent_slot]; |
| 861 | } else { |
| 862 | BUG(); |
| 863 | } |
| 864 | |
| 865 | edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut); |
| 866 | |
| 867 | /* Create a new node now since we're going to need it anyway */ |
| 868 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
| 869 | if (!new_n0) |
| 870 | return false; |
| 871 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); |
| 872 | edit->adjust_count_on = new_n0; |
| 873 | |
| 874 | /* Insert a new shortcut before the new node if this segment isn't of |
| 875 | * zero length - otherwise we just connect the new node directly to the |
| 876 | * parent. |
| 877 | */ |
| 878 | level += ASSOC_ARRAY_LEVEL_STEP; |
| 879 | if (diff > level) { |
| 880 | pr_devel("pre-shortcut %d...%d\n", level, diff); |
| 881 | keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
| 882 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
| 883 | |
| 884 | new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + |
| 885 | keylen * sizeof(unsigned long), GFP_KERNEL); |
| 886 | if (!new_s0) |
| 887 | return false; |
| 888 | edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0); |
| 889 | edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); |
| 890 | new_s0->back_pointer = shortcut->back_pointer; |
| 891 | new_s0->parent_slot = shortcut->parent_slot; |
| 892 | new_s0->next_node = assoc_array_node_to_ptr(new_n0); |
| 893 | new_s0->skip_to_level = diff; |
| 894 | |
| 895 | new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); |
| 896 | new_n0->parent_slot = 0; |
| 897 | |
| 898 | memcpy(new_s0->index_key, shortcut->index_key, |
| 899 | keylen * sizeof(unsigned long)); |
| 900 | |
| 901 | blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); |
| 902 | pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank); |
| 903 | new_s0->index_key[keylen - 1] &= ~blank; |
| 904 | } else { |
| 905 | pr_devel("no pre-shortcut\n"); |
| 906 | edit->set[0].to = assoc_array_node_to_ptr(new_n0); |
| 907 | new_n0->back_pointer = shortcut->back_pointer; |
| 908 | new_n0->parent_slot = shortcut->parent_slot; |
| 909 | } |
| 910 | |
| 911 | side = assoc_array_ptr_to_node(shortcut->next_node); |
| 912 | new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch; |
| 913 | |
| 914 | /* We need to know which slot in the new node is going to take a |
| 915 | * metadata pointer. |
| 916 | */ |
| 917 | sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); |
| 918 | sc_slot &= ASSOC_ARRAY_FAN_MASK; |
| 919 | |
| 920 | pr_devel("new slot %lx >> %d -> %d\n", |
| 921 | sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot); |
| 922 | |
| 923 | /* Determine whether we need to follow the new node with a replacement |
| 924 | * for the current shortcut. We could in theory reuse the current |
| 925 | * shortcut if its parent slot number doesn't change - but that's a |
| 926 | * 1-in-16 chance so not worth expending the code upon. |
| 927 | */ |
| 928 | level = diff + ASSOC_ARRAY_LEVEL_STEP; |
| 929 | if (level < shortcut->skip_to_level) { |
| 930 | pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level); |
| 931 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
| 932 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
| 933 | |
| 934 | new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) + |
| 935 | keylen * sizeof(unsigned long), GFP_KERNEL); |
| 936 | if (!new_s1) |
| 937 | return false; |
| 938 | edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1); |
| 939 | |
| 940 | new_s1->back_pointer = assoc_array_node_to_ptr(new_n0); |
| 941 | new_s1->parent_slot = sc_slot; |
| 942 | new_s1->next_node = shortcut->next_node; |
| 943 | new_s1->skip_to_level = shortcut->skip_to_level; |
| 944 | |
| 945 | new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1); |
| 946 | |
| 947 | memcpy(new_s1->index_key, shortcut->index_key, |
| 948 | keylen * sizeof(unsigned long)); |
| 949 | |
| 950 | edit->set[1].ptr = &side->back_pointer; |
| 951 | edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1); |
| 952 | } else { |
| 953 | pr_devel("no post-shortcut\n"); |
| 954 | |
| 955 | /* We don't have to replace the pointed-to node as long as we |
| 956 | * use memory barriers to make sure the parent slot number is |
| 957 | * changed before the back pointer (the parent slot number is |
| 958 | * irrelevant to the old parent shortcut). |
| 959 | */ |
| 960 | new_n0->slots[sc_slot] = shortcut->next_node; |
| 961 | edit->set_parent_slot[0].p = &side->parent_slot; |
| 962 | edit->set_parent_slot[0].to = sc_slot; |
| 963 | edit->set[1].ptr = &side->back_pointer; |
| 964 | edit->set[1].to = assoc_array_node_to_ptr(new_n0); |
| 965 | } |
| 966 | |
| 967 | /* Install the new leaf in a spare slot in the new node. */ |
| 968 | if (sc_slot == 0) |
| 969 | edit->leaf_p = &new_n0->slots[1]; |
| 970 | else |
| 971 | edit->leaf_p = &new_n0->slots[0]; |
| 972 | |
| 973 | pr_devel("<--%s() = ok [split shortcut]\n", __func__); |
| 974 | return edit; |
| 975 | } |
| 976 | |
| 977 | /** |
| 978 | * assoc_array_insert - Script insertion of an object into an associative array |
| 979 | * @array: The array to insert into. |
| 980 | * @ops: The operations to use. |
| 981 | * @index_key: The key to insert at. |
| 982 | * @object: The object to insert. |
| 983 | * |
| 984 | * Precalculate and preallocate a script for the insertion or replacement of an |
| 985 | * object in an associative array. This results in an edit script that can |
| 986 | * either be applied or cancelled. |
| 987 | * |
| 988 | * The function returns a pointer to an edit script or -ENOMEM. |
| 989 | * |
| 990 | * The caller should lock against other modifications and must continue to hold |
| 991 | * the lock until assoc_array_apply_edit() has been called. |
| 992 | * |
| 993 | * Accesses to the tree may take place concurrently with this function, |
| 994 | * provided they hold the RCU read lock. |
| 995 | */ |
| 996 | struct assoc_array_edit *assoc_array_insert(struct assoc_array *array, |
| 997 | const struct assoc_array_ops *ops, |
| 998 | const void *index_key, |
| 999 | void *object) |
| 1000 | { |
| 1001 | struct assoc_array_walk_result result; |
| 1002 | struct assoc_array_edit *edit; |
| 1003 | |
| 1004 | pr_devel("-->%s()\n", __func__); |
| 1005 | |
| 1006 | /* The leaf pointer we're given must not have the bottom bit set as we |
| 1007 | * use those for type-marking the pointer. NULL pointers are also not |
| 1008 | * allowed as they indicate an empty slot but we have to allow them |
| 1009 | * here as they can be updated later. |
| 1010 | */ |
| 1011 | BUG_ON(assoc_array_ptr_is_meta(object)); |
| 1012 | |
| 1013 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
| 1014 | if (!edit) |
| 1015 | return ERR_PTR(-ENOMEM); |
| 1016 | edit->array = array; |
| 1017 | edit->ops = ops; |
| 1018 | edit->leaf = assoc_array_leaf_to_ptr(object); |
| 1019 | edit->adjust_count_by = 1; |
| 1020 | |
| 1021 | switch (assoc_array_walk(array, ops, index_key, &result)) { |
| 1022 | case assoc_array_walk_tree_empty: |
| 1023 | /* Allocate a root node if there isn't one yet */ |
| 1024 | if (!assoc_array_insert_in_empty_tree(edit)) |
| 1025 | goto enomem; |
| 1026 | return edit; |
| 1027 | |
| 1028 | case assoc_array_walk_found_terminal_node: |
| 1029 | /* We found a node that doesn't have a node/shortcut pointer in |
| 1030 | * the slot corresponding to the index key that we have to |
| 1031 | * follow. |
| 1032 | */ |
| 1033 | if (!assoc_array_insert_into_terminal_node(edit, ops, index_key, |
| 1034 | &result)) |
| 1035 | goto enomem; |
| 1036 | return edit; |
| 1037 | |
| 1038 | case assoc_array_walk_found_wrong_shortcut: |
| 1039 | /* We found a shortcut that didn't match our key in a slot we |
| 1040 | * needed to follow. |
| 1041 | */ |
| 1042 | if (!assoc_array_insert_mid_shortcut(edit, ops, &result)) |
| 1043 | goto enomem; |
| 1044 | return edit; |
| 1045 | } |
| 1046 | |
| 1047 | enomem: |
| 1048 | /* Clean up after an out of memory error */ |
| 1049 | pr_devel("enomem\n"); |
| 1050 | assoc_array_cancel_edit(edit); |
| 1051 | return ERR_PTR(-ENOMEM); |
| 1052 | } |
| 1053 | |
| 1054 | /** |
| 1055 | * assoc_array_insert_set_object - Set the new object pointer in an edit script |
| 1056 | * @edit: The edit script to modify. |
| 1057 | * @object: The object pointer to set. |
| 1058 | * |
| 1059 | * Change the object to be inserted in an edit script. The object pointed to |
| 1060 | * by the old object is not freed. This must be done prior to applying the |
| 1061 | * script. |
| 1062 | */ |
| 1063 | void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object) |
| 1064 | { |
| 1065 | BUG_ON(!object); |
| 1066 | edit->leaf = assoc_array_leaf_to_ptr(object); |
| 1067 | } |
| 1068 | |
| 1069 | struct assoc_array_delete_collapse_context { |
| 1070 | struct assoc_array_node *node; |
| 1071 | const void *skip_leaf; |
| 1072 | int slot; |
| 1073 | }; |
| 1074 | |
| 1075 | /* |
| 1076 | * Subtree collapse to node iterator. |
| 1077 | */ |
| 1078 | static int assoc_array_delete_collapse_iterator(const void *leaf, |
| 1079 | void *iterator_data) |
| 1080 | { |
| 1081 | struct assoc_array_delete_collapse_context *collapse = iterator_data; |
| 1082 | |
| 1083 | if (leaf == collapse->skip_leaf) |
| 1084 | return 0; |
| 1085 | |
| 1086 | BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT); |
| 1087 | |
| 1088 | collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf); |
| 1089 | return 0; |
| 1090 | } |
| 1091 | |
| 1092 | /** |
| 1093 | * assoc_array_delete - Script deletion of an object from an associative array |
| 1094 | * @array: The array to search. |
| 1095 | * @ops: The operations to use. |
| 1096 | * @index_key: The key to the object. |
| 1097 | * |
| 1098 | * Precalculate and preallocate a script for the deletion of an object from an |
| 1099 | * associative array. This results in an edit script that can either be |
| 1100 | * applied or cancelled. |
| 1101 | * |
| 1102 | * The function returns a pointer to an edit script if the object was found, |
| 1103 | * NULL if the object was not found or -ENOMEM. |
| 1104 | * |
| 1105 | * The caller should lock against other modifications and must continue to hold |
| 1106 | * the lock until assoc_array_apply_edit() has been called. |
| 1107 | * |
| 1108 | * Accesses to the tree may take place concurrently with this function, |
| 1109 | * provided they hold the RCU read lock. |
| 1110 | */ |
| 1111 | struct assoc_array_edit *assoc_array_delete(struct assoc_array *array, |
| 1112 | const struct assoc_array_ops *ops, |
| 1113 | const void *index_key) |
| 1114 | { |
| 1115 | struct assoc_array_delete_collapse_context collapse; |
| 1116 | struct assoc_array_walk_result result; |
| 1117 | struct assoc_array_node *node, *new_n0; |
| 1118 | struct assoc_array_edit *edit; |
| 1119 | struct assoc_array_ptr *ptr; |
| 1120 | bool has_meta; |
| 1121 | int slot, i; |
| 1122 | |
| 1123 | pr_devel("-->%s()\n", __func__); |
| 1124 | |
| 1125 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
| 1126 | if (!edit) |
| 1127 | return ERR_PTR(-ENOMEM); |
| 1128 | edit->array = array; |
| 1129 | edit->ops = ops; |
| 1130 | edit->adjust_count_by = -1; |
| 1131 | |
| 1132 | switch (assoc_array_walk(array, ops, index_key, &result)) { |
| 1133 | case assoc_array_walk_found_terminal_node: |
| 1134 | /* We found a node that should contain the leaf we've been |
| 1135 | * asked to remove - *if* it's in the tree. |
| 1136 | */ |
| 1137 | pr_devel("terminal_node\n"); |
| 1138 | node = result.terminal_node.node; |
| 1139 | |
| 1140 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
| 1141 | ptr = node->slots[slot]; |
| 1142 | if (ptr && |
| 1143 | assoc_array_ptr_is_leaf(ptr) && |
| 1144 | ops->compare_object(assoc_array_ptr_to_leaf(ptr), |
| 1145 | index_key)) |
| 1146 | goto found_leaf; |
| 1147 | } |
| 1148 | case assoc_array_walk_tree_empty: |
| 1149 | case assoc_array_walk_found_wrong_shortcut: |
| 1150 | default: |
| 1151 | assoc_array_cancel_edit(edit); |
| 1152 | pr_devel("not found\n"); |
| 1153 | return NULL; |
| 1154 | } |
| 1155 | |
| 1156 | found_leaf: |
| 1157 | BUG_ON(array->nr_leaves_on_tree <= 0); |
| 1158 | |
| 1159 | /* In the simplest form of deletion we just clear the slot and release |
| 1160 | * the leaf after a suitable interval. |
| 1161 | */ |
| 1162 | edit->dead_leaf = node->slots[slot]; |
| 1163 | edit->set[0].ptr = &node->slots[slot]; |
| 1164 | edit->set[0].to = NULL; |
| 1165 | edit->adjust_count_on = node; |
| 1166 | |
| 1167 | /* If that concludes erasure of the last leaf, then delete the entire |
| 1168 | * internal array. |
| 1169 | */ |
| 1170 | if (array->nr_leaves_on_tree == 1) { |
| 1171 | edit->set[1].ptr = &array->root; |
| 1172 | edit->set[1].to = NULL; |
| 1173 | edit->adjust_count_on = NULL; |
| 1174 | edit->excised_subtree = array->root; |
| 1175 | pr_devel("all gone\n"); |
| 1176 | return edit; |
| 1177 | } |
| 1178 | |
| 1179 | /* However, we'd also like to clear up some metadata blocks if we |
| 1180 | * possibly can. |
| 1181 | * |
| 1182 | * We go for a simple algorithm of: if this node has FAN_OUT or fewer |
| 1183 | * leaves in it, then attempt to collapse it - and attempt to |
| 1184 | * recursively collapse up the tree. |
| 1185 | * |
| 1186 | * We could also try and collapse in partially filled subtrees to take |
| 1187 | * up space in this node. |
| 1188 | */ |
| 1189 | if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { |
| 1190 | struct assoc_array_node *parent, *grandparent; |
| 1191 | struct assoc_array_ptr *ptr; |
| 1192 | |
| 1193 | /* First of all, we need to know if this node has metadata so |
| 1194 | * that we don't try collapsing if all the leaves are already |
| 1195 | * here. |
| 1196 | */ |
| 1197 | has_meta = false; |
| 1198 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 1199 | ptr = node->slots[i]; |
| 1200 | if (assoc_array_ptr_is_meta(ptr)) { |
| 1201 | has_meta = true; |
| 1202 | break; |
| 1203 | } |
| 1204 | } |
| 1205 | |
| 1206 | pr_devel("leaves: %ld [m=%d]\n", |
| 1207 | node->nr_leaves_on_branch - 1, has_meta); |
| 1208 | |
| 1209 | /* Look further up the tree to see if we can collapse this node |
| 1210 | * into a more proximal node too. |
| 1211 | */ |
| 1212 | parent = node; |
| 1213 | collapse_up: |
| 1214 | pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch); |
| 1215 | |
| 1216 | ptr = parent->back_pointer; |
| 1217 | if (!ptr) |
| 1218 | goto do_collapse; |
| 1219 | if (assoc_array_ptr_is_shortcut(ptr)) { |
| 1220 | struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr); |
| 1221 | ptr = s->back_pointer; |
| 1222 | if (!ptr) |
| 1223 | goto do_collapse; |
| 1224 | } |
| 1225 | |
| 1226 | grandparent = assoc_array_ptr_to_node(ptr); |
| 1227 | if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { |
| 1228 | parent = grandparent; |
| 1229 | goto collapse_up; |
| 1230 | } |
| 1231 | |
| 1232 | do_collapse: |
| 1233 | /* There's no point collapsing if the original node has no meta |
| 1234 | * pointers to discard and if we didn't merge into one of that |
| 1235 | * node's ancestry. |
| 1236 | */ |
| 1237 | if (has_meta || parent != node) { |
| 1238 | node = parent; |
| 1239 | |
| 1240 | /* Create a new node to collapse into */ |
| 1241 | new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
| 1242 | if (!new_n0) |
| 1243 | goto enomem; |
| 1244 | edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); |
| 1245 | |
| 1246 | new_n0->back_pointer = node->back_pointer; |
| 1247 | new_n0->parent_slot = node->parent_slot; |
| 1248 | new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; |
| 1249 | edit->adjust_count_on = new_n0; |
| 1250 | |
| 1251 | collapse.node = new_n0; |
| 1252 | collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf); |
| 1253 | collapse.slot = 0; |
| 1254 | assoc_array_subtree_iterate(assoc_array_node_to_ptr(node), |
| 1255 | node->back_pointer, |
| 1256 | assoc_array_delete_collapse_iterator, |
| 1257 | &collapse); |
| 1258 | pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch); |
| 1259 | BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1); |
| 1260 | |
| 1261 | if (!node->back_pointer) { |
| 1262 | edit->set[1].ptr = &array->root; |
| 1263 | } else if (assoc_array_ptr_is_leaf(node->back_pointer)) { |
| 1264 | BUG(); |
| 1265 | } else if (assoc_array_ptr_is_node(node->back_pointer)) { |
| 1266 | struct assoc_array_node *p = |
| 1267 | assoc_array_ptr_to_node(node->back_pointer); |
| 1268 | edit->set[1].ptr = &p->slots[node->parent_slot]; |
| 1269 | } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) { |
| 1270 | struct assoc_array_shortcut *s = |
| 1271 | assoc_array_ptr_to_shortcut(node->back_pointer); |
| 1272 | edit->set[1].ptr = &s->next_node; |
| 1273 | } |
| 1274 | edit->set[1].to = assoc_array_node_to_ptr(new_n0); |
| 1275 | edit->excised_subtree = assoc_array_node_to_ptr(node); |
| 1276 | } |
| 1277 | } |
| 1278 | |
| 1279 | return edit; |
| 1280 | |
| 1281 | enomem: |
| 1282 | /* Clean up after an out of memory error */ |
| 1283 | pr_devel("enomem\n"); |
| 1284 | assoc_array_cancel_edit(edit); |
| 1285 | return ERR_PTR(-ENOMEM); |
| 1286 | } |
| 1287 | |
| 1288 | /** |
| 1289 | * assoc_array_clear - Script deletion of all objects from an associative array |
| 1290 | * @array: The array to clear. |
| 1291 | * @ops: The operations to use. |
| 1292 | * |
| 1293 | * Precalculate and preallocate a script for the deletion of all the objects |
| 1294 | * from an associative array. This results in an edit script that can either |
| 1295 | * be applied or cancelled. |
| 1296 | * |
| 1297 | * The function returns a pointer to an edit script if there are objects to be |
| 1298 | * deleted, NULL if there are no objects in the array or -ENOMEM. |
| 1299 | * |
| 1300 | * The caller should lock against other modifications and must continue to hold |
| 1301 | * the lock until assoc_array_apply_edit() has been called. |
| 1302 | * |
| 1303 | * Accesses to the tree may take place concurrently with this function, |
| 1304 | * provided they hold the RCU read lock. |
| 1305 | */ |
| 1306 | struct assoc_array_edit *assoc_array_clear(struct assoc_array *array, |
| 1307 | const struct assoc_array_ops *ops) |
| 1308 | { |
| 1309 | struct assoc_array_edit *edit; |
| 1310 | |
| 1311 | pr_devel("-->%s()\n", __func__); |
| 1312 | |
| 1313 | if (!array->root) |
| 1314 | return NULL; |
| 1315 | |
| 1316 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
| 1317 | if (!edit) |
| 1318 | return ERR_PTR(-ENOMEM); |
| 1319 | edit->array = array; |
| 1320 | edit->ops = ops; |
| 1321 | edit->set[1].ptr = &array->root; |
| 1322 | edit->set[1].to = NULL; |
| 1323 | edit->excised_subtree = array->root; |
| 1324 | edit->ops_for_excised_subtree = ops; |
| 1325 | pr_devel("all gone\n"); |
| 1326 | return edit; |
| 1327 | } |
| 1328 | |
| 1329 | /* |
| 1330 | * Handle the deferred destruction after an applied edit. |
| 1331 | */ |
| 1332 | static void assoc_array_rcu_cleanup(struct rcu_head *head) |
| 1333 | { |
| 1334 | struct assoc_array_edit *edit = |
| 1335 | container_of(head, struct assoc_array_edit, rcu); |
| 1336 | int i; |
| 1337 | |
| 1338 | pr_devel("-->%s()\n", __func__); |
| 1339 | |
| 1340 | if (edit->dead_leaf) |
| 1341 | edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf)); |
| 1342 | for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++) |
| 1343 | if (edit->excised_meta[i]) |
| 1344 | kfree(assoc_array_ptr_to_node(edit->excised_meta[i])); |
| 1345 | |
| 1346 | if (edit->excised_subtree) { |
| 1347 | BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree)); |
| 1348 | if (assoc_array_ptr_is_node(edit->excised_subtree)) { |
| 1349 | struct assoc_array_node *n = |
| 1350 | assoc_array_ptr_to_node(edit->excised_subtree); |
| 1351 | n->back_pointer = NULL; |
| 1352 | } else { |
| 1353 | struct assoc_array_shortcut *s = |
| 1354 | assoc_array_ptr_to_shortcut(edit->excised_subtree); |
| 1355 | s->back_pointer = NULL; |
| 1356 | } |
| 1357 | assoc_array_destroy_subtree(edit->excised_subtree, |
| 1358 | edit->ops_for_excised_subtree); |
| 1359 | } |
| 1360 | |
| 1361 | kfree(edit); |
| 1362 | } |
| 1363 | |
| 1364 | /** |
| 1365 | * assoc_array_apply_edit - Apply an edit script to an associative array |
| 1366 | * @edit: The script to apply. |
| 1367 | * |
| 1368 | * Apply an edit script to an associative array to effect an insertion, |
| 1369 | * deletion or clearance. As the edit script includes preallocated memory, |
| 1370 | * this is guaranteed not to fail. |
| 1371 | * |
| 1372 | * The edit script, dead objects and dead metadata will be scheduled for |
| 1373 | * destruction after an RCU grace period to permit those doing read-only |
| 1374 | * accesses on the array to continue to do so under the RCU read lock whilst |
| 1375 | * the edit is taking place. |
| 1376 | */ |
| 1377 | void assoc_array_apply_edit(struct assoc_array_edit *edit) |
| 1378 | { |
| 1379 | struct assoc_array_shortcut *shortcut; |
| 1380 | struct assoc_array_node *node; |
| 1381 | struct assoc_array_ptr *ptr; |
| 1382 | int i; |
| 1383 | |
| 1384 | pr_devel("-->%s()\n", __func__); |
| 1385 | |
| 1386 | smp_wmb(); |
| 1387 | if (edit->leaf_p) |
| 1388 | *edit->leaf_p = edit->leaf; |
| 1389 | |
| 1390 | smp_wmb(); |
| 1391 | for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++) |
| 1392 | if (edit->set_parent_slot[i].p) |
| 1393 | *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to; |
| 1394 | |
| 1395 | smp_wmb(); |
| 1396 | for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++) |
| 1397 | if (edit->set_backpointers[i]) |
| 1398 | *edit->set_backpointers[i] = edit->set_backpointers_to; |
| 1399 | |
| 1400 | smp_wmb(); |
| 1401 | for (i = 0; i < ARRAY_SIZE(edit->set); i++) |
| 1402 | if (edit->set[i].ptr) |
| 1403 | *edit->set[i].ptr = edit->set[i].to; |
| 1404 | |
| 1405 | if (edit->array->root == NULL) { |
| 1406 | edit->array->nr_leaves_on_tree = 0; |
| 1407 | } else if (edit->adjust_count_on) { |
| 1408 | node = edit->adjust_count_on; |
| 1409 | for (;;) { |
| 1410 | node->nr_leaves_on_branch += edit->adjust_count_by; |
| 1411 | |
| 1412 | ptr = node->back_pointer; |
| 1413 | if (!ptr) |
| 1414 | break; |
| 1415 | if (assoc_array_ptr_is_shortcut(ptr)) { |
| 1416 | shortcut = assoc_array_ptr_to_shortcut(ptr); |
| 1417 | ptr = shortcut->back_pointer; |
| 1418 | if (!ptr) |
| 1419 | break; |
| 1420 | } |
| 1421 | BUG_ON(!assoc_array_ptr_is_node(ptr)); |
| 1422 | node = assoc_array_ptr_to_node(ptr); |
| 1423 | } |
| 1424 | |
| 1425 | edit->array->nr_leaves_on_tree += edit->adjust_count_by; |
| 1426 | } |
| 1427 | |
| 1428 | call_rcu(&edit->rcu, assoc_array_rcu_cleanup); |
| 1429 | } |
| 1430 | |
| 1431 | /** |
| 1432 | * assoc_array_cancel_edit - Discard an edit script. |
| 1433 | * @edit: The script to discard. |
| 1434 | * |
| 1435 | * Free an edit script and all the preallocated data it holds without making |
| 1436 | * any changes to the associative array it was intended for. |
| 1437 | * |
| 1438 | * NOTE! In the case of an insertion script, this does _not_ release the leaf |
| 1439 | * that was to be inserted. That is left to the caller. |
| 1440 | */ |
| 1441 | void assoc_array_cancel_edit(struct assoc_array_edit *edit) |
| 1442 | { |
| 1443 | struct assoc_array_ptr *ptr; |
| 1444 | int i; |
| 1445 | |
| 1446 | pr_devel("-->%s()\n", __func__); |
| 1447 | |
| 1448 | /* Clean up after an out of memory error */ |
| 1449 | for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) { |
| 1450 | ptr = edit->new_meta[i]; |
| 1451 | if (ptr) { |
| 1452 | if (assoc_array_ptr_is_node(ptr)) |
| 1453 | kfree(assoc_array_ptr_to_node(ptr)); |
| 1454 | else |
| 1455 | kfree(assoc_array_ptr_to_shortcut(ptr)); |
| 1456 | } |
| 1457 | } |
| 1458 | kfree(edit); |
| 1459 | } |
| 1460 | |
| 1461 | /** |
| 1462 | * assoc_array_gc - Garbage collect an associative array. |
| 1463 | * @array: The array to clean. |
| 1464 | * @ops: The operations to use. |
| 1465 | * @iterator: A callback function to pass judgement on each object. |
| 1466 | * @iterator_data: Private data for the callback function. |
| 1467 | * |
| 1468 | * Collect garbage from an associative array and pack down the internal tree to |
| 1469 | * save memory. |
| 1470 | * |
| 1471 | * The iterator function is asked to pass judgement upon each object in the |
| 1472 | * array. If it returns false, the object is discard and if it returns true, |
| 1473 | * the object is kept. If it returns true, it must increment the object's |
| 1474 | * usage count (or whatever it needs to do to retain it) before returning. |
| 1475 | * |
| 1476 | * This function returns 0 if successful or -ENOMEM if out of memory. In the |
| 1477 | * latter case, the array is not changed. |
| 1478 | * |
| 1479 | * The caller should lock against other modifications and must continue to hold |
| 1480 | * the lock until assoc_array_apply_edit() has been called. |
| 1481 | * |
| 1482 | * Accesses to the tree may take place concurrently with this function, |
| 1483 | * provided they hold the RCU read lock. |
| 1484 | */ |
| 1485 | int assoc_array_gc(struct assoc_array *array, |
| 1486 | const struct assoc_array_ops *ops, |
| 1487 | bool (*iterator)(void *object, void *iterator_data), |
| 1488 | void *iterator_data) |
| 1489 | { |
| 1490 | struct assoc_array_shortcut *shortcut, *new_s; |
| 1491 | struct assoc_array_node *node, *new_n; |
| 1492 | struct assoc_array_edit *edit; |
| 1493 | struct assoc_array_ptr *cursor, *ptr; |
| 1494 | struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp; |
| 1495 | unsigned long nr_leaves_on_tree; |
| 1496 | int keylen, slot, nr_free, next_slot, i; |
| 1497 | |
| 1498 | pr_devel("-->%s()\n", __func__); |
| 1499 | |
| 1500 | if (!array->root) |
| 1501 | return 0; |
| 1502 | |
| 1503 | edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); |
| 1504 | if (!edit) |
| 1505 | return -ENOMEM; |
| 1506 | edit->array = array; |
| 1507 | edit->ops = ops; |
| 1508 | edit->ops_for_excised_subtree = ops; |
| 1509 | edit->set[0].ptr = &array->root; |
| 1510 | edit->excised_subtree = array->root; |
| 1511 | |
| 1512 | new_root = new_parent = NULL; |
| 1513 | new_ptr_pp = &new_root; |
| 1514 | cursor = array->root; |
| 1515 | |
| 1516 | descend: |
| 1517 | /* If this point is a shortcut, then we need to duplicate it and |
| 1518 | * advance the target cursor. |
| 1519 | */ |
| 1520 | if (assoc_array_ptr_is_shortcut(cursor)) { |
| 1521 | shortcut = assoc_array_ptr_to_shortcut(cursor); |
| 1522 | keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); |
| 1523 | keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; |
| 1524 | new_s = kmalloc(sizeof(struct assoc_array_shortcut) + |
| 1525 | keylen * sizeof(unsigned long), GFP_KERNEL); |
| 1526 | if (!new_s) |
| 1527 | goto enomem; |
| 1528 | pr_devel("dup shortcut %p -> %p\n", shortcut, new_s); |
| 1529 | memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) + |
| 1530 | keylen * sizeof(unsigned long))); |
| 1531 | new_s->back_pointer = new_parent; |
| 1532 | new_s->parent_slot = shortcut->parent_slot; |
| 1533 | *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s); |
| 1534 | new_ptr_pp = &new_s->next_node; |
| 1535 | cursor = shortcut->next_node; |
| 1536 | } |
| 1537 | |
| 1538 | /* Duplicate the node at this position */ |
| 1539 | node = assoc_array_ptr_to_node(cursor); |
| 1540 | new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); |
| 1541 | if (!new_n) |
| 1542 | goto enomem; |
| 1543 | pr_devel("dup node %p -> %p\n", node, new_n); |
| 1544 | new_n->back_pointer = new_parent; |
| 1545 | new_n->parent_slot = node->parent_slot; |
| 1546 | *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n); |
| 1547 | new_ptr_pp = NULL; |
| 1548 | slot = 0; |
| 1549 | |
| 1550 | continue_node: |
| 1551 | /* Filter across any leaves and gc any subtrees */ |
| 1552 | for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
| 1553 | ptr = node->slots[slot]; |
| 1554 | if (!ptr) |
| 1555 | continue; |
| 1556 | |
| 1557 | if (assoc_array_ptr_is_leaf(ptr)) { |
| 1558 | if (iterator(assoc_array_ptr_to_leaf(ptr), |
| 1559 | iterator_data)) |
| 1560 | /* The iterator will have done any reference |
| 1561 | * counting on the object for us. |
| 1562 | */ |
| 1563 | new_n->slots[slot] = ptr; |
| 1564 | continue; |
| 1565 | } |
| 1566 | |
| 1567 | new_ptr_pp = &new_n->slots[slot]; |
| 1568 | cursor = ptr; |
| 1569 | goto descend; |
| 1570 | } |
| 1571 | |
| 1572 | pr_devel("-- compress node %p --\n", new_n); |
| 1573 | |
| 1574 | /* Count up the number of empty slots in this node and work out the |
| 1575 | * subtree leaf count. |
| 1576 | */ |
| 1577 | new_n->nr_leaves_on_branch = 0; |
| 1578 | nr_free = 0; |
| 1579 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
| 1580 | ptr = new_n->slots[slot]; |
| 1581 | if (!ptr) |
| 1582 | nr_free++; |
| 1583 | else if (assoc_array_ptr_is_leaf(ptr)) |
| 1584 | new_n->nr_leaves_on_branch++; |
| 1585 | } |
| 1586 | pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch); |
| 1587 | |
| 1588 | /* See what we can fold in */ |
| 1589 | next_slot = 0; |
| 1590 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { |
| 1591 | struct assoc_array_shortcut *s; |
| 1592 | struct assoc_array_node *child; |
| 1593 | |
| 1594 | ptr = new_n->slots[slot]; |
| 1595 | if (!ptr || assoc_array_ptr_is_leaf(ptr)) |
| 1596 | continue; |
| 1597 | |
| 1598 | s = NULL; |
| 1599 | if (assoc_array_ptr_is_shortcut(ptr)) { |
| 1600 | s = assoc_array_ptr_to_shortcut(ptr); |
| 1601 | ptr = s->next_node; |
| 1602 | } |
| 1603 | |
| 1604 | child = assoc_array_ptr_to_node(ptr); |
| 1605 | new_n->nr_leaves_on_branch += child->nr_leaves_on_branch; |
| 1606 | |
| 1607 | if (child->nr_leaves_on_branch <= nr_free + 1) { |
| 1608 | /* Fold the child node into this one */ |
| 1609 | pr_devel("[%d] fold node %lu/%d [nx %d]\n", |
| 1610 | slot, child->nr_leaves_on_branch, nr_free + 1, |
| 1611 | next_slot); |
| 1612 | |
| 1613 | /* We would already have reaped an intervening shortcut |
| 1614 | * on the way back up the tree. |
| 1615 | */ |
| 1616 | BUG_ON(s); |
| 1617 | |
| 1618 | new_n->slots[slot] = NULL; |
| 1619 | nr_free++; |
| 1620 | if (slot < next_slot) |
| 1621 | next_slot = slot; |
| 1622 | for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { |
| 1623 | struct assoc_array_ptr *p = child->slots[i]; |
| 1624 | if (!p) |
| 1625 | continue; |
| 1626 | BUG_ON(assoc_array_ptr_is_meta(p)); |
| 1627 | while (new_n->slots[next_slot]) |
| 1628 | next_slot++; |
| 1629 | BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT); |
| 1630 | new_n->slots[next_slot++] = p; |
| 1631 | nr_free--; |
| 1632 | } |
| 1633 | kfree(child); |
| 1634 | } else { |
| 1635 | pr_devel("[%d] retain node %lu/%d [nx %d]\n", |
| 1636 | slot, child->nr_leaves_on_branch, nr_free + 1, |
| 1637 | next_slot); |
| 1638 | } |
| 1639 | } |
| 1640 | |
| 1641 | pr_devel("after: %lu\n", new_n->nr_leaves_on_branch); |
| 1642 | |
| 1643 | nr_leaves_on_tree = new_n->nr_leaves_on_branch; |
| 1644 | |
| 1645 | /* Excise this node if it is singly occupied by a shortcut */ |
| 1646 | if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) { |
| 1647 | for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) |
| 1648 | if ((ptr = new_n->slots[slot])) |
| 1649 | break; |
| 1650 | |
| 1651 | if (assoc_array_ptr_is_meta(ptr) && |
| 1652 | assoc_array_ptr_is_shortcut(ptr)) { |
| 1653 | pr_devel("excise node %p with 1 shortcut\n", new_n); |
| 1654 | new_s = assoc_array_ptr_to_shortcut(ptr); |
| 1655 | new_parent = new_n->back_pointer; |
| 1656 | slot = new_n->parent_slot; |
| 1657 | kfree(new_n); |
| 1658 | if (!new_parent) { |
| 1659 | new_s->back_pointer = NULL; |
| 1660 | new_s->parent_slot = 0; |
| 1661 | new_root = ptr; |
| 1662 | goto gc_complete; |
| 1663 | } |
| 1664 | |
| 1665 | if (assoc_array_ptr_is_shortcut(new_parent)) { |
| 1666 | /* We can discard any preceding shortcut also */ |
| 1667 | struct assoc_array_shortcut *s = |
| 1668 | assoc_array_ptr_to_shortcut(new_parent); |
| 1669 | |
| 1670 | pr_devel("excise preceding shortcut\n"); |
| 1671 | |
| 1672 | new_parent = new_s->back_pointer = s->back_pointer; |
| 1673 | slot = new_s->parent_slot = s->parent_slot; |
| 1674 | kfree(s); |
| 1675 | if (!new_parent) { |
| 1676 | new_s->back_pointer = NULL; |
| 1677 | new_s->parent_slot = 0; |
| 1678 | new_root = ptr; |
| 1679 | goto gc_complete; |
| 1680 | } |
| 1681 | } |
| 1682 | |
| 1683 | new_s->back_pointer = new_parent; |
| 1684 | new_s->parent_slot = slot; |
| 1685 | new_n = assoc_array_ptr_to_node(new_parent); |
| 1686 | new_n->slots[slot] = ptr; |
| 1687 | goto ascend_old_tree; |
| 1688 | } |
| 1689 | } |
| 1690 | |
| 1691 | /* Excise any shortcuts we might encounter that point to nodes that |
| 1692 | * only contain leaves. |
| 1693 | */ |
| 1694 | ptr = new_n->back_pointer; |
| 1695 | if (!ptr) |
| 1696 | goto gc_complete; |
| 1697 | |
| 1698 | if (assoc_array_ptr_is_shortcut(ptr)) { |
| 1699 | new_s = assoc_array_ptr_to_shortcut(ptr); |
| 1700 | new_parent = new_s->back_pointer; |
| 1701 | slot = new_s->parent_slot; |
| 1702 | |
| 1703 | if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { |
| 1704 | struct assoc_array_node *n; |
| 1705 | |
| 1706 | pr_devel("excise shortcut\n"); |
| 1707 | new_n->back_pointer = new_parent; |
| 1708 | new_n->parent_slot = slot; |
| 1709 | kfree(new_s); |
| 1710 | if (!new_parent) { |
| 1711 | new_root = assoc_array_node_to_ptr(new_n); |
| 1712 | goto gc_complete; |
| 1713 | } |
| 1714 | |
| 1715 | n = assoc_array_ptr_to_node(new_parent); |
| 1716 | n->slots[slot] = assoc_array_node_to_ptr(new_n); |
| 1717 | } |
| 1718 | } else { |
| 1719 | new_parent = ptr; |
| 1720 | } |
| 1721 | new_n = assoc_array_ptr_to_node(new_parent); |
| 1722 | |
| 1723 | ascend_old_tree: |
| 1724 | ptr = node->back_pointer; |
| 1725 | if (assoc_array_ptr_is_shortcut(ptr)) { |
| 1726 | shortcut = assoc_array_ptr_to_shortcut(ptr); |
| 1727 | slot = shortcut->parent_slot; |
| 1728 | cursor = shortcut->back_pointer; |
David Howells | 95389b0 | 2014-09-10 22:22:00 +0100 | [diff] [blame] | 1729 | if (!cursor) |
| 1730 | goto gc_complete; |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 1731 | } else { |
| 1732 | slot = node->parent_slot; |
| 1733 | cursor = ptr; |
| 1734 | } |
David Howells | 95389b0 | 2014-09-10 22:22:00 +0100 | [diff] [blame] | 1735 | BUG_ON(!cursor); |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 1736 | node = assoc_array_ptr_to_node(cursor); |
| 1737 | slot++; |
| 1738 | goto continue_node; |
| 1739 | |
| 1740 | gc_complete: |
| 1741 | edit->set[0].to = new_root; |
| 1742 | assoc_array_apply_edit(edit); |
David Howells | 2741960 | 2014-09-02 13:52:20 +0100 | [diff] [blame] | 1743 | array->nr_leaves_on_tree = nr_leaves_on_tree; |
David Howells | 3cb9895 | 2013-09-24 10:35:17 +0100 | [diff] [blame] | 1744 | return 0; |
| 1745 | |
| 1746 | enomem: |
| 1747 | pr_devel("enomem\n"); |
| 1748 | assoc_array_destroy_subtree(new_root, edit->ops); |
| 1749 | kfree(edit); |
| 1750 | return -ENOMEM; |
| 1751 | } |