| 1 | /* |
| 2 | * Copyright (c) 2007 The DragonFly Project. All rights reserved. |
| 3 | * |
| 4 | * This code is derived from software contributed to The DragonFly Project |
| 5 | * by Matthew Dillon <dillon@backplane.com> |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms, with or without |
| 8 | * modification, are permitted provided that the following conditions |
| 9 | * are met: |
| 10 | * |
| 11 | * 1. Redistributions of source code must retain the above copyright |
| 12 | * notice, this list of conditions and the following disclaimer. |
| 13 | * 2. Redistributions in binary form must reproduce the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer in |
| 15 | * the documentation and/or other materials provided with the |
| 16 | * distribution. |
| 17 | * 3. Neither the name of The DragonFly Project nor the names of its |
| 18 | * contributors may be used to endorse or promote products derived |
| 19 | * from this software without specific, prior written permission. |
| 20 | * |
| 21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 22 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 23 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| 24 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| 25 | * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 26 | * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| 27 | * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| 28 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| 29 | * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| 30 | * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| 31 | * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 32 | * SUCH DAMAGE. |
| 33 | * |
| 34 | * $DragonFly: src/sys/vfs/hammer/hammer_btree.c,v 1.13 2007/12/30 08:49:20 dillon Exp $ |
| 35 | */ |
| 36 | |
| 37 | /* |
| 38 | * HAMMER B-Tree index |
| 39 | * |
| 40 | * HAMMER implements a modified B+Tree. In documentation this will |
| 41 | * simply be refered to as the HAMMER B-Tree. Basically a B-Tree |
| 42 | * looks like a B+Tree (A B-Tree which stores its records only at the leafs |
| 43 | * of the tree), but adds two additional boundary elements which describe |
| 44 | * the left-most and right-most element a node is able to represent. In |
| 45 | * otherwords, we have boundary elements at the two ends of a B-Tree node |
| 46 | * instead of sub-tree pointers. |
| 47 | * |
| 48 | * A B-Tree internal node looks like this: |
| 49 | * |
| 50 | * B N N N N N N B <-- boundary and internal elements |
| 51 | * S S S S S S S <-- subtree pointers |
| 52 | * |
| 53 | * A B-Tree leaf node basically looks like this: |
| 54 | * |
| 55 | * L L L L L L L L <-- leaf elemenets |
| 56 | * |
| 57 | * The radix for an internal node is 1 less then a leaf but we get a |
| 58 | * number of significant benefits for our troubles. |
| 59 | * |
| 60 | * The big benefit to using a B-Tree containing boundary information |
| 61 | * is that it is possible to cache pointers into the middle of the tree |
| 62 | * and not have to start searches, insertions, OR deletions at the root |
| 63 | * node. In particular, searches are able to progress in a definitive |
| 64 | * direction from any point in the tree without revisting nodes. This |
| 65 | * greatly improves the efficiency of many operations, most especially |
| 66 | * record appends. |
| 67 | * |
| 68 | * B-Trees also make the stacking of trees fairly straightforward. |
| 69 | * |
| 70 | * INTER-CLUSTER ELEMENTS: An element of an internal node may reference |
| 71 | * the root of another cluster rather then a node in the current cluster. |
| 72 | * This is known as an inter-cluster references. Only B-Tree searches |
| 73 | * will cross cluster boundaries. The rebalancing and collapse code does |
| 74 | * not attempt to move children between clusters. A major effect of this |
| 75 | * is that we have to relax minimum element count requirements and allow |
| 76 | * trees to become somewhat unabalanced. |
| 77 | * |
| 78 | * INSERTIONS AND DELETIONS: When inserting we split full nodes on our |
| 79 | * way down as an optimization. I originally experimented with rebalancing |
| 80 | * nodes on the way down for deletions but it created a huge mess due to |
| 81 | * the way inter-cluster linkages work. Instead, now I simply allow |
| 82 | * the tree to become unbalanced and allow leaf nodes to become empty. |
| 83 | * The delete code will try to clean things up from the bottom-up but |
| 84 | * will stop if related elements are not in-core or if it cannot get a node |
| 85 | * lock. |
| 86 | */ |
| 87 | #include "hammer.h" |
| 88 | #include <sys/buf.h> |
| 89 | #include <sys/buf2.h> |
| 90 | |
| 91 | static int btree_search(hammer_cursor_t cursor, int flags); |
| 92 | static int btree_split_internal(hammer_cursor_t cursor); |
| 93 | static int btree_split_leaf(hammer_cursor_t cursor); |
| 94 | static int btree_remove(hammer_cursor_t cursor); |
| 95 | static int btree_set_parent(hammer_node_t node, hammer_btree_elm_t elm); |
| 96 | #if 0 |
| 97 | static int btree_rebalance(hammer_cursor_t cursor); |
| 98 | static int btree_collapse(hammer_cursor_t cursor); |
| 99 | #endif |
| 100 | static int btree_node_is_full(hammer_node_ondisk_t node); |
| 101 | static void hammer_make_separator(hammer_base_elm_t key1, |
| 102 | hammer_base_elm_t key2, hammer_base_elm_t dest); |
| 103 | |
| 104 | /* |
| 105 | * Iterate records after a search. The cursor is iterated forwards past |
| 106 | * the current record until a record matching the key-range requirements |
| 107 | * is found. ENOENT is returned if the iteration goes past the ending |
| 108 | * key. |
| 109 | * |
| 110 | * The iteration is inclusive of key_beg and can be inclusive or exclusive |
| 111 | * of key_end depending on whether HAMMER_CURSOR_END_INCLUSIVE is set. |
| 112 | * |
| 113 | * cursor->key_beg may or may not be modified by this function during |
| 114 | * the iteration. XXX future - in case of an inverted lock we may have |
| 115 | * to reinitiate the lookup and set key_beg to properly pick up where we |
| 116 | * left off. |
| 117 | */ |
| 118 | int |
| 119 | hammer_btree_iterate(hammer_cursor_t cursor) |
| 120 | { |
| 121 | hammer_node_ondisk_t node; |
| 122 | hammer_btree_elm_t elm; |
| 123 | int error; |
| 124 | int r; |
| 125 | int s; |
| 126 | |
| 127 | /* |
| 128 | * Skip past the current record |
| 129 | */ |
| 130 | node = cursor->node->ondisk; |
| 131 | if (node == NULL) |
| 132 | return(ENOENT); |
| 133 | if (cursor->index < node->count && |
| 134 | (cursor->flags & HAMMER_CURSOR_ATEDISK)) { |
| 135 | ++cursor->index; |
| 136 | } |
| 137 | |
| 138 | /* |
| 139 | * Loop until an element is found or we are done. |
| 140 | */ |
| 141 | for (;;) { |
| 142 | /* |
| 143 | * We iterate up the tree and then index over one element |
| 144 | * while we are at the last element in the current node. |
| 145 | * |
| 146 | * NOTE: This can pop us up to another cluster. |
| 147 | * |
| 148 | * If we are at the root of the root cluster, cursor_up |
| 149 | * returns ENOENT. |
| 150 | * |
| 151 | * NOTE: hammer_cursor_up() will adjust cursor->key_beg |
| 152 | * when told to re-search for the cluster tag. |
| 153 | * |
| 154 | * XXX this could be optimized by storing the information in |
| 155 | * the parent reference. |
| 156 | * |
| 157 | * XXX we can lose the node lock temporarily, this could mess |
| 158 | * up our scan. |
| 159 | */ |
| 160 | if (cursor->index == node->count) { |
| 161 | error = hammer_cursor_up(cursor, 0); |
| 162 | if (error) |
| 163 | break; |
| 164 | node = cursor->node->ondisk; |
| 165 | KKASSERT(cursor->index != node->count); |
| 166 | ++cursor->index; |
| 167 | continue; |
| 168 | } |
| 169 | |
| 170 | /* |
| 171 | * Check internal or leaf element. Determine if the record |
| 172 | * at the cursor has gone beyond the end of our range. |
| 173 | * Remember that our key range is end-exclusive. |
| 174 | * |
| 175 | * Generally we recurse down through internal nodes. An |
| 176 | * internal node can only be returned if INCLUSTER is set |
| 177 | * and the node represents a cluster-push record. Internal |
| 178 | * elements do not contain create_tid/delete_tid information. |
| 179 | */ |
| 180 | if (node->type == HAMMER_BTREE_TYPE_INTERNAL) { |
| 181 | elm = &node->elms[cursor->index]; |
| 182 | r = hammer_btree_cmp(&cursor->key_end, &elm[0].base); |
| 183 | s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base); |
| 184 | if (r < 0) { |
| 185 | error = ENOENT; |
| 186 | break; |
| 187 | } |
| 188 | if (r == 0 && (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) { |
| 189 | error = ENOENT; |
| 190 | break; |
| 191 | } |
| 192 | KKASSERT(s <= 0); |
| 193 | if ((cursor->flags & HAMMER_CURSOR_INCLUSTER) == 0 || |
| 194 | elm->internal.rec_offset == 0) { |
| 195 | error = hammer_cursor_down(cursor); |
| 196 | if (error) |
| 197 | break; |
| 198 | KKASSERT(cursor->index == 0); |
| 199 | node = cursor->node->ondisk; |
| 200 | continue; |
| 201 | } |
| 202 | } else { |
| 203 | elm = &node->elms[cursor->index]; |
| 204 | r = hammer_btree_cmp(&cursor->key_end, &elm->base); |
| 205 | if (r < 0) { |
| 206 | error = ENOENT; |
| 207 | break; |
| 208 | } |
| 209 | if (r == 0 && (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) { |
| 210 | error = ENOENT; |
| 211 | break; |
| 212 | } |
| 213 | if ((cursor->flags & HAMMER_CURSOR_ALLHISTORY) == 0 && |
| 214 | hammer_btree_chkts(cursor->key_beg.create_tid, |
| 215 | &elm->base) != 0) { |
| 216 | ++cursor->index; |
| 217 | continue; |
| 218 | } |
| 219 | } |
| 220 | |
| 221 | /* |
| 222 | * Return entry |
| 223 | */ |
| 224 | return(0); |
| 225 | } |
| 226 | return(error); |
| 227 | } |
| 228 | |
| 229 | /* |
| 230 | * Lookup cursor->key_beg. 0 is returned on success, ENOENT if the entry |
| 231 | * could not be found, and a fatal error otherwise. |
| 232 | * |
| 233 | * The cursor is suitably positioned for a deletion on success, and suitably |
| 234 | * positioned for an insertion on ENOENT. |
| 235 | * |
| 236 | * The cursor may begin anywhere, the search will traverse clusters in |
| 237 | * either direction to locate the requested element. |
| 238 | */ |
| 239 | int |
| 240 | hammer_btree_lookup(hammer_cursor_t cursor) |
| 241 | { |
| 242 | int error; |
| 243 | |
| 244 | error = btree_search(cursor, 0); |
| 245 | if (error == 0 && cursor->flags) |
| 246 | error = hammer_btree_extract(cursor, cursor->flags); |
| 247 | return(error); |
| 248 | } |
| 249 | |
| 250 | /* |
| 251 | * Execute the logic required to start an iteration. The first record |
| 252 | * located within the specified range is returned and iteration control |
| 253 | * flags are adjusted for successive hammer_btree_iterate() calls. |
| 254 | */ |
| 255 | int |
| 256 | hammer_btree_first(hammer_cursor_t cursor) |
| 257 | { |
| 258 | int error; |
| 259 | |
| 260 | error = hammer_btree_lookup(cursor); |
| 261 | if (error == ENOENT) { |
| 262 | cursor->flags &= ~HAMMER_CURSOR_ATEDISK; |
| 263 | error = hammer_btree_iterate(cursor); |
| 264 | } |
| 265 | cursor->flags |= HAMMER_CURSOR_ATEDISK; |
| 266 | return(error); |
| 267 | } |
| 268 | |
| 269 | /* |
| 270 | * Extract the record and/or data associated with the cursor's current |
| 271 | * position. Any prior record or data stored in the cursor is replaced. |
| 272 | * The cursor must be positioned at a leaf node. |
| 273 | * |
| 274 | * NOTE: Most extractions occur at the leaf of the B-Tree. The only |
| 275 | * extraction allowed at an internal element is at a cluster-push. |
| 276 | * Cluster-push elements have records but no data. |
| 277 | */ |
| 278 | int |
| 279 | hammer_btree_extract(hammer_cursor_t cursor, int flags) |
| 280 | { |
| 281 | hammer_node_ondisk_t node; |
| 282 | hammer_btree_elm_t elm; |
| 283 | hammer_cluster_t cluster; |
| 284 | u_int64_t buf_type; |
| 285 | int32_t cloff; |
| 286 | int32_t roff; |
| 287 | int error; |
| 288 | |
| 289 | /* |
| 290 | * A cluster record type has no data reference, the information |
| 291 | * is stored directly in the record and B-Tree element. |
| 292 | * |
| 293 | * The case where the data reference resolves to the same buffer |
| 294 | * as the record reference must be handled. |
| 295 | */ |
| 296 | node = cursor->node->ondisk; |
| 297 | elm = &node->elms[cursor->index]; |
| 298 | cluster = cursor->node->cluster; |
| 299 | cursor->flags &= ~HAMMER_CURSOR_DATA_EMBEDDED; |
| 300 | cursor->data = NULL; |
| 301 | error = 0; |
| 302 | |
| 303 | /* |
| 304 | * Internal elements can only be cluster pushes. A cluster push has |
| 305 | * no data reference. |
| 306 | */ |
| 307 | if (node->type == HAMMER_BTREE_TYPE_INTERNAL) { |
| 308 | cloff = elm->leaf.rec_offset; |
| 309 | KKASSERT(cloff != 0); |
| 310 | cursor->record = hammer_bread(cluster, cloff, |
| 311 | HAMMER_FSBUF_RECORDS, &error, |
| 312 | &cursor->record_buffer); |
| 313 | return(error); |
| 314 | } |
| 315 | |
| 316 | /* |
| 317 | * Leaf element. |
| 318 | */ |
| 319 | if ((flags & HAMMER_CURSOR_GET_RECORD) && error == 0) { |
| 320 | cloff = elm->leaf.rec_offset; |
| 321 | cursor->record = hammer_bread(cluster, cloff, |
| 322 | HAMMER_FSBUF_RECORDS, &error, |
| 323 | &cursor->record_buffer); |
| 324 | } else { |
| 325 | cloff = 0; |
| 326 | } |
| 327 | if ((flags & HAMMER_CURSOR_GET_DATA) && error == 0) { |
| 328 | if ((cloff ^ elm->leaf.data_offset) & ~HAMMER_BUFMASK) { |
| 329 | /* |
| 330 | * The data is not in the same buffer as the last |
| 331 | * record we cached, but it could still be embedded |
| 332 | * in a record. Note that we may not have loaded the |
| 333 | * record's buffer above, depending on flags. |
| 334 | */ |
| 335 | if ((elm->leaf.rec_offset ^ elm->leaf.data_offset) & |
| 336 | ~HAMMER_BUFMASK) { |
| 337 | if (elm->leaf.data_len & HAMMER_BUFMASK) |
| 338 | buf_type = HAMMER_FSBUF_DATA; |
| 339 | else |
| 340 | buf_type = 0; /* pure data buffer */ |
| 341 | } else { |
| 342 | buf_type = HAMMER_FSBUF_RECORDS; |
| 343 | } |
| 344 | cursor->data = hammer_bread(cluster, |
| 345 | elm->leaf.data_offset, |
| 346 | buf_type, &error, |
| 347 | &cursor->data_buffer); |
| 348 | } else { |
| 349 | /* |
| 350 | * Data in same buffer as record. Note that we |
| 351 | * leave any existing data_buffer intact, even |
| 352 | * though we don't use it in this case, in case |
| 353 | * other records extracted during an iteration |
| 354 | * go back to it. |
| 355 | * |
| 356 | * The data must be embedded in the record for this |
| 357 | * case to be hit. |
| 358 | * |
| 359 | * Just assume the buffer type is correct. |
| 360 | */ |
| 361 | cursor->data = (void *) |
| 362 | ((char *)cursor->record_buffer->ondisk + |
| 363 | (elm->leaf.data_offset & HAMMER_BUFMASK)); |
| 364 | roff = (char *)cursor->data - (char *)cursor->record; |
| 365 | KKASSERT (roff >= 0 && roff < HAMMER_RECORD_SIZE); |
| 366 | cursor->flags |= HAMMER_CURSOR_DATA_EMBEDDED; |
| 367 | } |
| 368 | } |
| 369 | return(error); |
| 370 | } |
| 371 | |
| 372 | |
| 373 | /* |
| 374 | * Insert a leaf element into the B-Tree at the current cursor position. |
| 375 | * The cursor is positioned such that the element at and beyond the cursor |
| 376 | * are shifted to make room for the new record. |
| 377 | * |
| 378 | * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT |
| 379 | * flag set and that call must return ENOENT before this function can be |
| 380 | * called. |
| 381 | * |
| 382 | * ENOSPC is returned if there is no room to insert a new record. |
| 383 | */ |
| 384 | int |
| 385 | hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_elm_t elm) |
| 386 | { |
| 387 | hammer_node_ondisk_t parent; |
| 388 | hammer_node_ondisk_t node; |
| 389 | int i; |
| 390 | |
| 391 | #if 0 |
| 392 | /* HANDLED BY CALLER */ |
| 393 | /* |
| 394 | * Issue a search to get our cursor at the right place. The search |
| 395 | * will get us to a leaf node. |
| 396 | * |
| 397 | * The search also does some setup for our insert, so there is always |
| 398 | * room in the leaf. |
| 399 | */ |
| 400 | error = btree_search(cursor, HAMMER_CURSOR_INSERT); |
| 401 | if (error != ENOENT) { |
| 402 | if (error == 0) |
| 403 | error = EEXIST; |
| 404 | return (error); |
| 405 | } |
| 406 | #endif |
| 407 | |
| 408 | /* |
| 409 | * Insert the element at the leaf node and update the count in the |
| 410 | * parent. It is possible for parent to be NULL, indicating that |
| 411 | * the root of the B-Tree in the cluster is a leaf. It is also |
| 412 | * possible for the leaf to be empty. |
| 413 | * |
| 414 | * Remember that the right-hand boundary is not included in the |
| 415 | * count. |
| 416 | */ |
| 417 | hammer_modify_node(cursor->node); |
| 418 | node = cursor->node->ondisk; |
| 419 | i = cursor->index; |
| 420 | KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF); |
| 421 | KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS); |
| 422 | if (i != node->count) { |
| 423 | bcopy(&node->elms[i], &node->elms[i+1], |
| 424 | (node->count - i) * sizeof(*elm)); |
| 425 | } |
| 426 | node->elms[i] = *elm; |
| 427 | ++node->count; |
| 428 | hammer_modify_node_done(cursor->node); |
| 429 | |
| 430 | /* |
| 431 | * Adjust the sub-tree count in the parent. note that the parent |
| 432 | * may be in a different cluster. |
| 433 | */ |
| 434 | if (cursor->parent) { |
| 435 | hammer_modify_node(cursor->parent); |
| 436 | parent = cursor->parent->ondisk; |
| 437 | i = cursor->parent_index; |
| 438 | ++parent->elms[i].internal.subtree_count; |
| 439 | hammer_modify_node_done(cursor->parent); |
| 440 | KKASSERT(parent->elms[i].internal.subtree_count <= node->count); |
| 441 | } |
| 442 | return(0); |
| 443 | } |
| 444 | |
| 445 | /* |
| 446 | * Delete a record from the B-Tree's at the current cursor position. |
| 447 | * The cursor is positioned such that the current element is the one |
| 448 | * to be deleted. |
| 449 | * |
| 450 | * On return the cursor will be positioned after the deleted element and |
| 451 | * MAY point to an internal node. It will be suitable for the continuation |
| 452 | * of an iteration but not for an insertion or deletion. |
| 453 | * |
| 454 | * Deletions will attempt to partially rebalance the B-Tree in an upward |
| 455 | * direction. It is possible to end up with empty leafs. An empty internal |
| 456 | * node is impossible (worst case: it has one element pointing to an empty |
| 457 | * leaf). |
| 458 | */ |
| 459 | int |
| 460 | hammer_btree_delete(hammer_cursor_t cursor) |
| 461 | { |
| 462 | hammer_node_ondisk_t ondisk; |
| 463 | hammer_node_t node; |
| 464 | hammer_node_t parent; |
| 465 | hammer_btree_elm_t elm; |
| 466 | int error; |
| 467 | int i; |
| 468 | |
| 469 | #if 0 |
| 470 | /* HANDLED BY CALLER */ |
| 471 | /* |
| 472 | * Locate the leaf element to delete. The search is also responsible |
| 473 | * for doing some of the rebalancing work on its way down. |
| 474 | */ |
| 475 | error = btree_search(cursor, HAMMER_CURSOR_DELETE); |
| 476 | if (error) |
| 477 | return (error); |
| 478 | #endif |
| 479 | |
| 480 | /* |
| 481 | * Delete the element from the leaf node. |
| 482 | * |
| 483 | * Remember that leaf nodes do not have boundaries. |
| 484 | */ |
| 485 | node = cursor->node; |
| 486 | ondisk = node->ondisk; |
| 487 | i = cursor->index; |
| 488 | |
| 489 | KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF); |
| 490 | hammer_modify_node(node); |
| 491 | if (i + 1 != ondisk->count) { |
| 492 | bcopy(&ondisk->elms[i+1], &ondisk->elms[i], |
| 493 | (ondisk->count - i - 1) * sizeof(ondisk->elms[0])); |
| 494 | } |
| 495 | --ondisk->count; |
| 496 | hammer_modify_node_done(node); |
| 497 | if (cursor->parent != NULL) { |
| 498 | /* |
| 499 | * Adjust parent's notion of the leaf's count. subtree_count |
| 500 | * is only approximate, it is allowed to be too small but |
| 501 | * never allowed to be too large. Make sure we don't drop |
| 502 | * the count below 0. |
| 503 | */ |
| 504 | parent = cursor->parent; |
| 505 | hammer_modify_node(parent); |
| 506 | elm = &parent->ondisk->elms[cursor->parent_index]; |
| 507 | if (elm->internal.subtree_count) |
| 508 | --elm->internal.subtree_count; |
| 509 | hammer_modify_node_done(parent); |
| 510 | KKASSERT(elm->internal.subtree_count <= ondisk->count); |
| 511 | } |
| 512 | |
| 513 | /* |
| 514 | * It is possible, but not desireable, to stop here. If the element |
| 515 | * count drops to 0 (which is allowed for a leaf), try recursively |
| 516 | * remove the B-Tree node. |
| 517 | * |
| 518 | * XXX rebalancing calls would go here too. |
| 519 | * |
| 520 | * This may reposition the cursor at one of the parent's of the |
| 521 | * current node. |
| 522 | */ |
| 523 | if (ondisk->count == 0) { |
| 524 | error = btree_remove(cursor); |
| 525 | if (error == EAGAIN) |
| 526 | error = 0; |
| 527 | } else { |
| 528 | error = 0; |
| 529 | } |
| 530 | return(error); |
| 531 | } |
| 532 | |
| 533 | /* |
| 534 | * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE |
| 535 | * |
| 536 | * Search a cluster's B-Tree for cursor->key_beg, return the matching node. |
| 537 | * |
| 538 | * The search can begin ANYWHERE in the B-Tree. As a first step the search |
| 539 | * iterates up the tree as necessary to properly position itself prior to |
| 540 | * actually doing the sarch. |
| 541 | * |
| 542 | * INSERTIONS: The search will split full nodes and leaves on its way down |
| 543 | * and guarentee that the leaf it ends up on is not full. If we run out |
| 544 | * of space the search continues to the leaf (to position the cursor for |
| 545 | * the spike), but ENOSPC is returned. |
| 546 | * |
| 547 | * DELETIONS: The search will rebalance the tree on its way down. XXX |
| 548 | * |
| 549 | * The search is only guarenteed to end up on a leaf if an error code of 0 |
| 550 | * is returned, or if inserting and an error code of ENOENT is returned. |
| 551 | * Otherwise it can stop at an internal node. On success a search returns |
| 552 | * a leaf node unless INCLUSTER is set and the search located a cluster push |
| 553 | * node (which is an internal node). |
| 554 | */ |
| 555 | static |
| 556 | int |
| 557 | btree_search(hammer_cursor_t cursor, int flags) |
| 558 | { |
| 559 | hammer_node_ondisk_t node; |
| 560 | hammer_cluster_t cluster; |
| 561 | int error; |
| 562 | int enospc = 0; |
| 563 | int i; |
| 564 | int r; |
| 565 | |
| 566 | flags |= cursor->flags; |
| 567 | |
| 568 | /* |
| 569 | * Move our cursor up the tree until we find a node whos range covers |
| 570 | * the key we are trying to locate. This may move us between |
| 571 | * clusters. |
| 572 | * |
| 573 | * The left bound is inclusive, the right bound is non-inclusive. |
| 574 | * It is ok to cursor up too far so when cursoring across a cluster |
| 575 | * boundary. |
| 576 | * |
| 577 | * First see if we can skip the whole cluster. hammer_cursor_up() |
| 578 | * handles both cases but this way we don't check the cluster |
| 579 | * bounds when going up the tree within a cluster. |
| 580 | * |
| 581 | * NOTE: If INCLUSTER is set and we are at the root of the cluster, |
| 582 | * hammer_cursor_up() will return ENOENT. |
| 583 | */ |
| 584 | cluster = cursor->node->cluster; |
| 585 | while ( |
| 586 | hammer_btree_cmp(&cursor->key_beg, &cluster->clu_btree_beg) < 0 || |
| 587 | hammer_btree_cmp(&cursor->key_beg, &cluster->clu_btree_end) >= 0) { |
| 588 | error = hammer_cursor_toroot(cursor); |
| 589 | if (error) |
| 590 | goto done; |
| 591 | error = hammer_cursor_up(cursor, 0); |
| 592 | if (error) |
| 593 | goto done; |
| 594 | cluster = cursor->node->cluster; |
| 595 | } |
| 596 | |
| 597 | /* |
| 598 | * Deal with normal cursoring within a cluster. The right bound |
| 599 | * is non-inclusive. That is, the bounds form a separator. |
| 600 | */ |
| 601 | while (hammer_btree_cmp(&cursor->key_beg, cursor->left_bound) < 0 || |
| 602 | hammer_btree_cmp(&cursor->key_beg, cursor->right_bound) >= 0) { |
| 603 | error = hammer_cursor_up(cursor, 0); |
| 604 | if (error) |
| 605 | goto done; |
| 606 | } |
| 607 | |
| 608 | /* |
| 609 | * We better have ended up with a node somewhere, and our second |
| 610 | * while loop had better not have traversed up a cluster. |
| 611 | */ |
| 612 | KKASSERT(cursor->node != NULL && cursor->node->cluster == cluster); |
| 613 | |
| 614 | /* |
| 615 | * If we are inserting we can't start at a full node if the parent |
| 616 | * is also full (because there is no way to split the node), |
| 617 | * continue running up the tree until we hit the root of the |
| 618 | * root cluster or until the requirement is satisfied. |
| 619 | * |
| 620 | * NOTE: These cursor-up's CAN continue to cross cluster boundaries. |
| 621 | * |
| 622 | * XXX as an optimization it should be possible to unbalance the tree |
| 623 | * and stop at the root of the current cluster. |
| 624 | */ |
| 625 | while (flags & HAMMER_CURSOR_INSERT) { |
| 626 | if (btree_node_is_full(cursor->node->ondisk) == 0) |
| 627 | break; |
| 628 | if (cursor->parent == NULL) |
| 629 | break; |
| 630 | if (cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) |
| 631 | break; |
| 632 | error = hammer_cursor_up(cursor, 0); |
| 633 | /* cluster and node are now may become stale */ |
| 634 | if (error) |
| 635 | goto done; |
| 636 | } |
| 637 | /* cluster = cursor->node->cluster; not needed until next cluster = */ |
| 638 | |
| 639 | #if 0 |
| 640 | /* |
| 641 | * If we are deleting we can't start at an internal node with only |
| 642 | * one element unless it is root, because all of our code assumes |
| 643 | * that internal nodes will never be empty. Just do this generally |
| 644 | * for both leaf and internal nodes to get better balance. |
| 645 | * |
| 646 | * This handles the case where the cursor is sitting at a leaf and |
| 647 | * either the leaf or parent contain an insufficient number of |
| 648 | * elements. |
| 649 | * |
| 650 | * NOTE: These cursor-up's CAN continue to cross cluster boundaries. |
| 651 | * |
| 652 | * XXX NOTE: Iterations may not set this flag anyway. |
| 653 | */ |
| 654 | while (flags & HAMMER_CURSOR_DELETE) { |
| 655 | if (cursor->node->ondisk->count > 1) |
| 656 | break; |
| 657 | if (cursor->parent == NULL) |
| 658 | break; |
| 659 | KKASSERT(cursor->node->ondisk->count != 0); |
| 660 | error = hammer_cursor_up(cursor, 0); |
| 661 | /* cluster and node are now may become stale */ |
| 662 | if (error) |
| 663 | goto done; |
| 664 | } |
| 665 | #endif |
| 666 | |
| 667 | /*new_cluster:*/ |
| 668 | /* |
| 669 | * Push down through internal nodes to locate the requested key. |
| 670 | */ |
| 671 | cluster = cursor->node->cluster; |
| 672 | node = cursor->node->ondisk; |
| 673 | while (node->type == HAMMER_BTREE_TYPE_INTERNAL) { |
| 674 | #if 0 |
| 675 | /* |
| 676 | * If we are a the root node and deleting, try to collapse |
| 677 | * all of the root's children into the root. This is the |
| 678 | * only point where tree depth is reduced. |
| 679 | * |
| 680 | * XXX NOTE: Iterations may not set this flag anyway. |
| 681 | */ |
| 682 | if ((flags & HAMMER_CURSOR_DELETE) && cursor->parent == NULL) { |
| 683 | error = btree_collapse(cursor); |
| 684 | /* node becomes stale after call */ |
| 685 | /* XXX ENOSPC */ |
| 686 | if (error) |
| 687 | goto done; |
| 688 | } |
| 689 | node = cursor->node->ondisk; |
| 690 | #endif |
| 691 | /* |
| 692 | * Scan the node to find the subtree index to push down into. |
| 693 | * We go one-past, then back-up. |
| 694 | */ |
| 695 | for (i = 0; i < node->count; ++i) { |
| 696 | r = hammer_btree_cmp(&cursor->key_beg, |
| 697 | &node->elms[i].base); |
| 698 | if (r < 0) |
| 699 | break; |
| 700 | } |
| 701 | |
| 702 | /* |
| 703 | * It is possible for the search to terminate at i == 0, |
| 704 | * which is to the LEFT of the LEFT boundary but the RIGHT |
| 705 | * of the parent's boundary on the left of the sub-tree |
| 706 | * element. This case can occur due to deletions (see |
| 707 | * btree_remove()). |
| 708 | * |
| 709 | * When this case occurs an ENOENT return is guarenteed but |
| 710 | * if inserting we must still terminate at a leaf. The |
| 711 | * solution is to make the node's left boundary inherit the |
| 712 | * boundary stored in the parent. |
| 713 | * |
| 714 | * When doing this inheritance some fields in 'base' are |
| 715 | * actually related to the internal element's child |
| 716 | * specification and not to the key. These have to be |
| 717 | * retained. |
| 718 | * |
| 719 | * If we terminate at i == count it is still possible to |
| 720 | * be to the RIGHT of the RIGHT boundary but still to the |
| 721 | * LEFT of the parent's RIGHT boundary. The solution is to |
| 722 | * adjust the RIGHT boundary to match the parent. This |
| 723 | * case can occur due to deletions (see btree_remove()). |
| 724 | */ |
| 725 | if (i == 0) { |
| 726 | u_int8_t save; |
| 727 | |
| 728 | if ((flags & HAMMER_CURSOR_INSERT) == 0) { |
| 729 | cursor->index = 0; |
| 730 | return(ENOENT); |
| 731 | } |
| 732 | hammer_modify_node(cursor->node); |
| 733 | save = node->elms[0].subtree_type; |
| 734 | node->elms[0].base = *cursor->left_bound; |
| 735 | node->elms[0].subtree_type = save; |
| 736 | hammer_modify_node_done(cursor->node); |
| 737 | } else if (i == node->count) { |
| 738 | /* |
| 739 | * Terminate early if not inserting and the key is |
| 740 | * beyond the uncorrected right hand boundary. The |
| 741 | * index must be PAST the last element to prevent an |
| 742 | * iteration from returning elements to the left of |
| 743 | * key_beg. |
| 744 | */ |
| 745 | if ((flags & HAMMER_CURSOR_INSERT) == 0 && |
| 746 | hammer_btree_cmp(&cursor->key_beg, |
| 747 | &node->elms[i].base) >= 0 |
| 748 | ) { |
| 749 | cursor->index = i; |
| 750 | return(ENOENT); |
| 751 | } |
| 752 | |
| 753 | /* |
| 754 | * Correct a right-hand boundary mismatch. The push |
| 755 | * index is the last element (i-1). |
| 756 | */ |
| 757 | if (hammer_btree_cmp(&node->elms[i].base, |
| 758 | cursor->right_bound) != 0) { |
| 759 | hammer_modify_node(cursor->node); |
| 760 | node->elms[i].base = *cursor->right_bound; |
| 761 | hammer_modify_node_done(cursor->node); |
| 762 | } |
| 763 | --i; |
| 764 | } else { |
| 765 | /* |
| 766 | * The push-down index is now i - 1. |
| 767 | */ |
| 768 | --i; |
| 769 | } |
| 770 | cursor->index = i; |
| 771 | |
| 772 | /* |
| 773 | * Handle insertion and deletion requirements. |
| 774 | * |
| 775 | * If inserting split full nodes. The split code will |
| 776 | * adjust cursor->node and cursor->index if the current |
| 777 | * index winds up in the new node. |
| 778 | */ |
| 779 | if (flags & HAMMER_CURSOR_INSERT) { |
| 780 | if (node->count == HAMMER_BTREE_INT_ELMS) { |
| 781 | error = btree_split_internal(cursor); |
| 782 | if (error) { |
| 783 | if (error != ENOSPC) |
| 784 | goto done; |
| 785 | enospc = 1; |
| 786 | flags &= ~HAMMER_CURSOR_INSERT; |
| 787 | } |
| 788 | /* |
| 789 | * reload stale pointers |
| 790 | */ |
| 791 | i = cursor->index; |
| 792 | node = cursor->node->ondisk; |
| 793 | } |
| 794 | } |
| 795 | |
| 796 | #if 0 |
| 797 | /* |
| 798 | * If deleting rebalance - do not allow the child to have |
| 799 | * just one element or we will not be able to delete it. |
| 800 | * |
| 801 | * Neither internal or leaf nodes (except a root-leaf) are |
| 802 | * allowed to drop to 0 elements. (XXX - well, leaf nodes |
| 803 | * can at the moment). |
| 804 | * |
| 805 | * Our separators may have been reorganized after rebalancing, |
| 806 | * so we have to pop back up and rescan. |
| 807 | * |
| 808 | * XXX test for subtree_count < maxelms / 2, minus 1 or 2 |
| 809 | * for hysteresis? |
| 810 | * |
| 811 | * XXX NOTE: Iterations may not set this flag anyway. |
| 812 | */ |
| 813 | if (flags & HAMMER_CURSOR_DELETE) { |
| 814 | if (node->elms[i].internal.subtree_count <= 1) { |
| 815 | error = btree_rebalance(cursor); |
| 816 | if (error) |
| 817 | goto done; |
| 818 | /* cursor->index is invalid after call */ |
| 819 | goto new_cluster; |
| 820 | } |
| 821 | } |
| 822 | #endif |
| 823 | /* |
| 824 | * Cluster pushes are done with internal elements. If this |
| 825 | * is a cluster push (rec_offset != 0), and INCLUSTER is set, |
| 826 | * we stop here. |
| 827 | * |
| 828 | * However, because this is an internal node we have to |
| 829 | * determine whether key_beg is within its range and return |
| 830 | * 0 or ENOENT appropriately. |
| 831 | */ |
| 832 | if ((flags & HAMMER_CURSOR_INCLUSTER) && |
| 833 | node->elms[i].internal.rec_offset) { |
| 834 | r = hammer_btree_cmp(&cursor->key_beg, |
| 835 | &node->elms[i+1].base); |
| 836 | error = (r < 0) ? 0 : (enospc ? ENOSPC : ENOENT); |
| 837 | goto done; |
| 838 | } |
| 839 | |
| 840 | /* |
| 841 | * Push down (push into new node, existing node becomes |
| 842 | * the parent) and continue the search. |
| 843 | */ |
| 844 | error = hammer_cursor_down(cursor); |
| 845 | /* node and cluster become stale */ |
| 846 | if (error) |
| 847 | goto done; |
| 848 | node = cursor->node->ondisk; |
| 849 | cluster = cursor->node->cluster; |
| 850 | } |
| 851 | |
| 852 | /* |
| 853 | * We are at a leaf, do a linear search of the key array. |
| 854 | * |
| 855 | * On success the index is set to the matching element and 0 |
| 856 | * is returned. |
| 857 | * |
| 858 | * On failure the index is set to the insertion point and ENOENT |
| 859 | * is returned. |
| 860 | * |
| 861 | * Boundaries are not stored in leaf nodes, so the index can wind |
| 862 | * up to the left of element 0 (index == 0) or past the end of |
| 863 | * the array (index == node->count). |
| 864 | */ |
| 865 | KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS); |
| 866 | |
| 867 | for (i = 0; i < node->count; ++i) { |
| 868 | r = hammer_btree_cmp(&cursor->key_beg, &node->elms[i].base); |
| 869 | |
| 870 | /* |
| 871 | * Stop if we've flipped past key_beg |
| 872 | */ |
| 873 | if (r < 0) |
| 874 | break; |
| 875 | |
| 876 | /* |
| 877 | * Return an exact match |
| 878 | */ |
| 879 | if (r == 0) { |
| 880 | cursor->index = i; |
| 881 | error = 0; |
| 882 | goto done; |
| 883 | } |
| 884 | } |
| 885 | |
| 886 | /* |
| 887 | * No exact match was found, i is now at the insertion point. |
| 888 | * |
| 889 | * If inserting split a full leaf before returning. This |
| 890 | * may have the side effect of adjusting cursor->node and |
| 891 | * cursor->index. |
| 892 | */ |
| 893 | cursor->index = i; |
| 894 | if ((flags & HAMMER_CURSOR_INSERT) && |
| 895 | node->count == HAMMER_BTREE_LEAF_ELMS) { |
| 896 | error = btree_split_leaf(cursor); |
| 897 | if (error) { |
| 898 | if (error != ENOSPC) |
| 899 | goto done; |
| 900 | enospc = 1; |
| 901 | flags &= ~HAMMER_CURSOR_INSERT; |
| 902 | } |
| 903 | /* |
| 904 | * reload stale pointers |
| 905 | */ |
| 906 | /* NOT USED |
| 907 | i = cursor->index; |
| 908 | node = &cursor->node->internal; |
| 909 | */ |
| 910 | } |
| 911 | |
| 912 | /* |
| 913 | * We reached a leaf but did not find the key we were looking for. |
| 914 | * If this is an insert we will be properly positioned for an insert |
| 915 | * (ENOENT) or spike (ENOSPC) operation. |
| 916 | */ |
| 917 | error = enospc ? ENOSPC : ENOENT; |
| 918 | done: |
| 919 | return(error); |
| 920 | } |
| 921 | |
| 922 | |
| 923 | /************************************************************************ |
| 924 | * SPLITTING AND MERGING * |
| 925 | ************************************************************************ |
| 926 | * |
| 927 | * These routines do all the dirty work required to split and merge nodes. |
| 928 | */ |
| 929 | |
| 930 | /* |
| 931 | * Split an internal node into two nodes and move the separator at the split |
| 932 | * point to the parent. Note that the parent's parent's element pointing |
| 933 | * to our parent will have an incorrect subtree_count (we don't update it). |
| 934 | * It will be low, which is ok. |
| 935 | * |
| 936 | * (cursor->node, cursor->index) indicates the element the caller intends |
| 937 | * to push into. We will adjust node and index if that element winds |
| 938 | * up in the split node. |
| 939 | * |
| 940 | * If we are at the root of a cluster a new root must be created with two |
| 941 | * elements, one pointing to the original root and one pointing to the |
| 942 | * newly allocated split node. |
| 943 | * |
| 944 | * NOTE! Being at the root of a cluster is different from being at the |
| 945 | * root of the root cluster. cursor->parent will not be NULL and |
| 946 | * cursor->node->ondisk.parent must be tested against 0. Theoretically |
| 947 | * we could propogate the algorithm into the parent and deal with multiple |
| 948 | * 'roots' in the cluster header, but it's easier not to. |
| 949 | */ |
| 950 | static |
| 951 | int |
| 952 | btree_split_internal(hammer_cursor_t cursor) |
| 953 | { |
| 954 | hammer_node_ondisk_t ondisk; |
| 955 | hammer_node_t node; |
| 956 | hammer_node_t parent; |
| 957 | hammer_node_t new_node; |
| 958 | hammer_btree_elm_t elm; |
| 959 | hammer_btree_elm_t parent_elm; |
| 960 | int parent_index; |
| 961 | int made_root; |
| 962 | int split; |
| 963 | int error; |
| 964 | int i; |
| 965 | const int esize = sizeof(*elm); |
| 966 | |
| 967 | /* |
| 968 | * We are splitting but elms[split] will be promoted to the parent, |
| 969 | * leaving the right hand node with one less element. If the |
| 970 | * insertion point will be on the left-hand side adjust the split |
| 971 | * point to give the right hand side one additional node. |
| 972 | */ |
| 973 | node = cursor->node; |
| 974 | ondisk = node->ondisk; |
| 975 | split = (ondisk->count + 1) / 2; |
| 976 | if (cursor->index <= split) |
| 977 | --split; |
| 978 | error = 0; |
| 979 | |
| 980 | /* |
| 981 | * If we are at the root of the cluster, create a new root node with |
| 982 | * 1 element and split normally. Avoid making major modifications |
| 983 | * until we know the whole operation will work. |
| 984 | * |
| 985 | * The root of the cluster is different from the root of the root |
| 986 | * cluster. Use the node's on-disk structure's parent offset to |
| 987 | * detect the case. |
| 988 | */ |
| 989 | if (ondisk->parent == 0) { |
| 990 | parent = hammer_alloc_btree(node->cluster, &error); |
| 991 | if (parent == NULL) |
| 992 | return(error); |
| 993 | hammer_lock_ex(&parent->lock); |
| 994 | hammer_modify_node(parent); |
| 995 | ondisk = parent->ondisk; |
| 996 | ondisk->count = 1; |
| 997 | ondisk->parent = 0; |
| 998 | ondisk->type = HAMMER_BTREE_TYPE_INTERNAL; |
| 999 | ondisk->elms[0].base = node->cluster->clu_btree_beg; |
| 1000 | ondisk->elms[0].internal.subtree_type = node->ondisk->type; |
| 1001 | ondisk->elms[0].internal.subtree_offset = node->node_offset; |
| 1002 | ondisk->elms[1].base = node->cluster->clu_btree_end; |
| 1003 | made_root = 1; |
| 1004 | parent_index = 0; /* index of current node in parent */ |
| 1005 | hammer_modify_node_done(parent); |
| 1006 | } else { |
| 1007 | made_root = 0; |
| 1008 | parent = cursor->parent; |
| 1009 | parent_index = cursor->parent_index; |
| 1010 | KKASSERT(parent->cluster == node->cluster); |
| 1011 | } |
| 1012 | |
| 1013 | /* |
| 1014 | * Split node into new_node at the split point. |
| 1015 | * |
| 1016 | * B O O O P N N B <-- P = node->elms[split] |
| 1017 | * 0 1 2 3 4 5 6 <-- subtree indices |
| 1018 | * |
| 1019 | * x x P x x |
| 1020 | * s S S s |
| 1021 | * / \ |
| 1022 | * B O O O B B N N B <--- inner boundary points are 'P' |
| 1023 | * 0 1 2 3 4 5 6 |
| 1024 | * |
| 1025 | */ |
| 1026 | new_node = hammer_alloc_btree(node->cluster, &error); |
| 1027 | if (new_node == NULL) { |
| 1028 | if (made_root) { |
| 1029 | hammer_unlock(&parent->lock); |
| 1030 | hammer_free_btree(parent->cluster, parent->node_offset); |
| 1031 | hammer_rel_node(parent); |
| 1032 | } |
| 1033 | return(error); |
| 1034 | } |
| 1035 | hammer_lock_ex(&new_node->lock); |
| 1036 | |
| 1037 | /* |
| 1038 | * Create the new node. P becomes the left-hand boundary in the |
| 1039 | * new node. Copy the right-hand boundary as well. |
| 1040 | * |
| 1041 | * elm is the new separator. |
| 1042 | */ |
| 1043 | hammer_modify_node(new_node); |
| 1044 | hammer_modify_node(node); |
| 1045 | ondisk = node->ondisk; |
| 1046 | elm = &ondisk->elms[split]; |
| 1047 | bcopy(elm, &new_node->ondisk->elms[0], |
| 1048 | (ondisk->count - split + 1) * esize); |
| 1049 | new_node->ondisk->count = ondisk->count - split; |
| 1050 | new_node->ondisk->parent = parent->node_offset; |
| 1051 | new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL; |
| 1052 | KKASSERT(ondisk->type == new_node->ondisk->type); |
| 1053 | |
| 1054 | /* |
| 1055 | * Cleanup the original node. P becomes the new boundary, its |
| 1056 | * subtree_offset was moved to the new node. If we had created |
| 1057 | * a new root its parent pointer may have changed. |
| 1058 | */ |
| 1059 | elm->internal.subtree_offset = 0; |
| 1060 | elm->internal.rec_offset = 0; |
| 1061 | ondisk->count = split; |
| 1062 | |
| 1063 | /* |
| 1064 | * Insert the separator into the parent, fixup the parent's |
| 1065 | * reference to the original node, and reference the new node. |
| 1066 | * The separator is P. |
| 1067 | * |
| 1068 | * Remember that base.count does not include the right-hand boundary. |
| 1069 | */ |
| 1070 | hammer_modify_node(parent); |
| 1071 | ondisk = parent->ondisk; |
| 1072 | KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS); |
| 1073 | ondisk->elms[parent_index].internal.subtree_count = split; |
| 1074 | parent_elm = &ondisk->elms[parent_index+1]; |
| 1075 | bcopy(parent_elm, parent_elm + 1, |
| 1076 | (ondisk->count - parent_index) * esize); |
| 1077 | parent_elm->internal.base = elm->base; /* separator P */ |
| 1078 | parent_elm->internal.subtree_offset = new_node->node_offset; |
| 1079 | parent_elm->internal.subtree_count = new_node->ondisk->count; |
| 1080 | parent_elm->internal.subtree_type = new_node->ondisk->type; |
| 1081 | parent_elm->internal.subtree_vol_no = 0; |
| 1082 | parent_elm->internal.rec_offset = 0; |
| 1083 | ++ondisk->count; |
| 1084 | hammer_modify_node_done(parent); |
| 1085 | |
| 1086 | /* |
| 1087 | * The children of new_node need their parent pointer set to new_node. |
| 1088 | */ |
| 1089 | for (i = 0; i < new_node->ondisk->count; ++i) { |
| 1090 | elm = &new_node->ondisk->elms[i]; |
| 1091 | error = btree_set_parent(new_node, elm); |
| 1092 | if (error) { |
| 1093 | panic("btree_split_internal: btree-fixup problem"); |
| 1094 | } |
| 1095 | } |
| 1096 | |
| 1097 | /* |
| 1098 | * The cluster's root pointer may have to be updated. |
| 1099 | */ |
| 1100 | if (made_root) { |
| 1101 | hammer_modify_cluster(node->cluster); |
| 1102 | node->cluster->ondisk->clu_btree_root = parent->node_offset; |
| 1103 | hammer_modify_cluster_done(node->cluster); |
| 1104 | node->ondisk->parent = parent->node_offset; |
| 1105 | if (cursor->parent) { |
| 1106 | hammer_unlock(&cursor->parent->lock); |
| 1107 | hammer_rel_node(cursor->parent); |
| 1108 | } |
| 1109 | cursor->parent = parent; /* lock'd and ref'd */ |
| 1110 | } |
| 1111 | hammer_modify_node_done(new_node); |
| 1112 | hammer_modify_node_done(node); |
| 1113 | |
| 1114 | |
| 1115 | /* |
| 1116 | * Ok, now adjust the cursor depending on which element the original |
| 1117 | * index was pointing at. If we are >= the split point the push node |
| 1118 | * is now in the new node. |
| 1119 | * |
| 1120 | * NOTE: If we are at the split point itself we cannot stay with the |
| 1121 | * original node because the push index will point at the right-hand |
| 1122 | * boundary, which is illegal. |
| 1123 | * |
| 1124 | * NOTE: The cursor's parent or parent_index must be adjusted for |
| 1125 | * the case where a new parent (new root) was created, and the case |
| 1126 | * where the cursor is now pointing at the split node. |
| 1127 | */ |
| 1128 | if (cursor->index >= split) { |
| 1129 | cursor->parent_index = parent_index + 1; |
| 1130 | cursor->index -= split; |
| 1131 | hammer_unlock(&cursor->node->lock); |
| 1132 | hammer_rel_node(cursor->node); |
| 1133 | cursor->node = new_node; /* locked and ref'd */ |
| 1134 | } else { |
| 1135 | cursor->parent_index = parent_index; |
| 1136 | hammer_unlock(&new_node->lock); |
| 1137 | hammer_rel_node(new_node); |
| 1138 | } |
| 1139 | |
| 1140 | /* |
| 1141 | * Fixup left and right bounds |
| 1142 | */ |
| 1143 | parent_elm = &parent->ondisk->elms[cursor->parent_index]; |
| 1144 | cursor->left_bound = &parent_elm[0].internal.base; |
| 1145 | cursor->right_bound = &parent_elm[1].internal.base; |
| 1146 | |
| 1147 | return (0); |
| 1148 | } |
| 1149 | |
| 1150 | /* |
| 1151 | * Same as the above, but splits a full leaf node. |
| 1152 | */ |
| 1153 | static |
| 1154 | int |
| 1155 | btree_split_leaf(hammer_cursor_t cursor) |
| 1156 | { |
| 1157 | hammer_node_ondisk_t ondisk; |
| 1158 | hammer_node_t parent; |
| 1159 | hammer_node_t leaf; |
| 1160 | hammer_node_t new_leaf; |
| 1161 | hammer_btree_elm_t elm; |
| 1162 | hammer_btree_elm_t parent_elm; |
| 1163 | int parent_index; |
| 1164 | int made_root; |
| 1165 | int split; |
| 1166 | int error; |
| 1167 | const size_t esize = sizeof(*elm); |
| 1168 | |
| 1169 | /* |
| 1170 | * Calculate the split point. If the insertion point will be on |
| 1171 | * the left-hand side adjust the split point to give the right |
| 1172 | * hand side one additional node. |
| 1173 | */ |
| 1174 | leaf = cursor->node; |
| 1175 | ondisk = leaf->ondisk; |
| 1176 | split = (ondisk->count + 1) / 2; |
| 1177 | if (cursor->index <= split) |
| 1178 | --split; |
| 1179 | error = 0; |
| 1180 | |
| 1181 | /* |
| 1182 | * If we are at the root of the tree, create a new root node with |
| 1183 | * 1 element and split normally. Avoid making major modifications |
| 1184 | * until we know the whole operation will work. |
| 1185 | */ |
| 1186 | if (ondisk->parent == 0) { |
| 1187 | parent = hammer_alloc_btree(leaf->cluster, &error); |
| 1188 | if (parent == NULL) |
| 1189 | return(error); |
| 1190 | hammer_lock_ex(&parent->lock); |
| 1191 | hammer_modify_node(parent); |
| 1192 | ondisk = parent->ondisk; |
| 1193 | ondisk->count = 1; |
| 1194 | ondisk->parent = 0; |
| 1195 | ondisk->type = HAMMER_BTREE_TYPE_INTERNAL; |
| 1196 | ondisk->elms[0].base = leaf->cluster->clu_btree_beg; |
| 1197 | ondisk->elms[0].internal.subtree_type = leaf->ondisk->type; |
| 1198 | ondisk->elms[0].internal.subtree_offset = leaf->node_offset; |
| 1199 | ondisk->elms[1].base = leaf->cluster->clu_btree_end; |
| 1200 | hammer_modify_node_done(parent); |
| 1201 | made_root = 1; |
| 1202 | parent_index = 0; /* insertion point in parent */ |
| 1203 | } else { |
| 1204 | made_root = 0; |
| 1205 | parent = cursor->parent; |
| 1206 | parent_index = cursor->parent_index; |
| 1207 | KKASSERT(parent->cluster == leaf->cluster); |
| 1208 | } |
| 1209 | |
| 1210 | /* |
| 1211 | * Split leaf into new_leaf at the split point. Select a separator |
| 1212 | * value in-between the two leafs but with a bent towards the right |
| 1213 | * leaf since comparisons use an 'elm >= separator' inequality. |
| 1214 | * |
| 1215 | * L L L L L L L L |
| 1216 | * |
| 1217 | * x x P x x |
| 1218 | * s S S s |
| 1219 | * / \ |
| 1220 | * L L L L L L L L |
| 1221 | */ |
| 1222 | new_leaf = hammer_alloc_btree(leaf->cluster, &error); |
| 1223 | if (new_leaf == NULL) { |
| 1224 | if (made_root) { |
| 1225 | hammer_unlock(&parent->lock); |
| 1226 | hammer_free_btree(parent->cluster, parent->node_offset); |
| 1227 | hammer_rel_node(parent); |
| 1228 | } |
| 1229 | return(error); |
| 1230 | } |
| 1231 | hammer_lock_ex(&new_leaf->lock); |
| 1232 | |
| 1233 | /* |
| 1234 | * Create the new node. P become the left-hand boundary in the |
| 1235 | * new node. Copy the right-hand boundary as well. |
| 1236 | */ |
| 1237 | hammer_modify_node(leaf); |
| 1238 | hammer_modify_node(new_leaf); |
| 1239 | ondisk = leaf->ondisk; |
| 1240 | elm = &ondisk->elms[split]; |
| 1241 | bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize); |
| 1242 | new_leaf->ondisk->count = ondisk->count - split; |
| 1243 | new_leaf->ondisk->parent = parent->node_offset; |
| 1244 | new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF; |
| 1245 | KKASSERT(ondisk->type == new_leaf->ondisk->type); |
| 1246 | |
| 1247 | /* |
| 1248 | * Cleanup the original node. Because this is a leaf node and |
| 1249 | * leaf nodes do not have a right-hand boundary, there |
| 1250 | * aren't any special edge cases to clean up. We just fixup the |
| 1251 | * count. |
| 1252 | */ |
| 1253 | ondisk->count = split; |
| 1254 | |
| 1255 | /* |
| 1256 | * Insert the separator into the parent, fixup the parent's |
| 1257 | * reference to the original node, and reference the new node. |
| 1258 | * The separator is P. |
| 1259 | * |
| 1260 | * Remember that base.count does not include the right-hand boundary. |
| 1261 | * We are copying parent_index+1 to parent_index+2, not +0 to +1. |
| 1262 | */ |
| 1263 | hammer_modify_node(parent); |
| 1264 | ondisk = parent->ondisk; |
| 1265 | KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS); |
| 1266 | ondisk->elms[parent_index].internal.subtree_count = split; |
| 1267 | parent_elm = &ondisk->elms[parent_index+1]; |
| 1268 | bcopy(parent_elm, parent_elm + 1, |
| 1269 | (ondisk->count - parent_index) * esize); |
| 1270 | hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base); |
| 1271 | parent_elm->internal.subtree_offset = new_leaf->node_offset; |
| 1272 | parent_elm->internal.subtree_count = new_leaf->ondisk->count; |
| 1273 | parent_elm->internal.subtree_type = new_leaf->ondisk->type; |
| 1274 | parent_elm->internal.subtree_vol_no = 0; |
| 1275 | parent_elm->internal.rec_offset = 0; |
| 1276 | ++ondisk->count; |
| 1277 | hammer_modify_node_done(parent); |
| 1278 | |
| 1279 | /* |
| 1280 | * The cluster's root pointer may have to be updated. |
| 1281 | */ |
| 1282 | if (made_root) { |
| 1283 | hammer_modify_cluster(leaf->cluster); |
| 1284 | leaf->cluster->ondisk->clu_btree_root = parent->node_offset; |
| 1285 | hammer_modify_cluster_done(leaf->cluster); |
| 1286 | leaf->ondisk->parent = parent->node_offset; |
| 1287 | if (cursor->parent) { |
| 1288 | hammer_unlock(&cursor->parent->lock); |
| 1289 | hammer_rel_node(cursor->parent); |
| 1290 | } |
| 1291 | cursor->parent = parent; /* lock'd and ref'd */ |
| 1292 | } |
| 1293 | hammer_modify_node_done(leaf); |
| 1294 | hammer_modify_node_done(new_leaf); |
| 1295 | |
| 1296 | /* |
| 1297 | * Ok, now adjust the cursor depending on which element the original |
| 1298 | * index was pointing at. If we are >= the split point the push node |
| 1299 | * is now in the new node. |
| 1300 | * |
| 1301 | * NOTE: If we are at the split point itself we cannot stay with the |
| 1302 | * original node because the push index will point at the right-hand |
| 1303 | * boundary, which is illegal. |
| 1304 | */ |
| 1305 | if (cursor->index >= split) { |
| 1306 | cursor->parent_index = parent_index + 1; |
| 1307 | cursor->index -= split; |
| 1308 | hammer_unlock(&cursor->node->lock); |
| 1309 | hammer_rel_node(cursor->node); |
| 1310 | cursor->node = new_leaf; |
| 1311 | } else { |
| 1312 | cursor->parent_index = parent_index; |
| 1313 | hammer_unlock(&new_leaf->lock); |
| 1314 | hammer_rel_node(new_leaf); |
| 1315 | } |
| 1316 | |
| 1317 | /* |
| 1318 | * Fixup left and right bounds |
| 1319 | */ |
| 1320 | parent_elm = &parent->ondisk->elms[cursor->parent_index]; |
| 1321 | cursor->left_bound = &parent_elm[0].internal.base; |
| 1322 | cursor->right_bound = &parent_elm[1].internal.base; |
| 1323 | |
| 1324 | return (0); |
| 1325 | } |
| 1326 | |
| 1327 | /* |
| 1328 | * Attempt to remove the empty B-Tree node at (cursor->node). Returns 0 |
| 1329 | * on success, EAGAIN if we could not acquire the necessary locks, or some |
| 1330 | * other error. |
| 1331 | * |
| 1332 | * On return the cursor may end up pointing at an internal node, suitable |
| 1333 | * for further iteration but not for insertion or deletion. |
| 1334 | * |
| 1335 | * cursor->node may be an internal node or a leaf node. |
| 1336 | */ |
| 1337 | int |
| 1338 | btree_remove(hammer_cursor_t cursor) |
| 1339 | { |
| 1340 | hammer_node_ondisk_t ondisk; |
| 1341 | hammer_btree_elm_t elm; |
| 1342 | hammer_node_t save; |
| 1343 | hammer_node_t node; |
| 1344 | hammer_node_t parent; |
| 1345 | int error; |
| 1346 | int i; |
| 1347 | |
| 1348 | /* |
| 1349 | * If we are at the root of the root cluster there is nothing to |
| 1350 | * remove, but an internal node at the root of a cluster is not |
| 1351 | * allowed to be empty so convert it to a leaf node. |
| 1352 | */ |
| 1353 | if (cursor->parent == NULL) { |
| 1354 | hammer_modify_node(cursor->node); |
| 1355 | ondisk = cursor->node->ondisk; |
| 1356 | KKASSERT(ondisk->parent == 0); |
| 1357 | ondisk->type = HAMMER_BTREE_TYPE_LEAF; |
| 1358 | ondisk->count = 0; |
| 1359 | hammer_modify_node_done(cursor->node); |
| 1360 | kprintf("EMPTY ROOT OF ROOT CLUSTER -> LEAF\n"); |
| 1361 | return(0); |
| 1362 | } |
| 1363 | |
| 1364 | /* |
| 1365 | * Retain a reference to cursor->node, ex-lock again (2 locks now) |
| 1366 | * so we do not lose the lock when we cursor around. |
| 1367 | */ |
| 1368 | save = cursor->node; |
| 1369 | hammer_ref_node(save); |
| 1370 | hammer_lock_ex(&save->lock); |
| 1371 | |
| 1372 | /* |
| 1373 | * We need to be able to lock the parent of the parent. Do this |
| 1374 | * non-blocking and return EAGAIN if the lock cannot be acquired. |
| 1375 | * non-blocking is required in order to avoid a deadlock. |
| 1376 | * |
| 1377 | * After we cursor up, parent is moved to node and the new parent |
| 1378 | * is the parent of the parent. |
| 1379 | */ |
| 1380 | error = hammer_cursor_up(cursor, 1); |
| 1381 | if (error) { |
| 1382 | kprintf("BTREE_REMOVE: Cannot lock parent\n"); |
| 1383 | hammer_unlock(&save->lock); |
| 1384 | hammer_rel_node(save); |
| 1385 | return(error); |
| 1386 | } |
| 1387 | |
| 1388 | /* |
| 1389 | * At this point we want to remove the element at (node, index), |
| 1390 | * which is now the (original) parent pointing to the saved node. |
| 1391 | * Removing the element allows us to then free the node it was |
| 1392 | * pointing to. |
| 1393 | * |
| 1394 | * However, an internal node is not allowed to have 0 elements, so |
| 1395 | * if the count would drop to 0 we have to recurse. It is possible |
| 1396 | * for the recursion to fail. |
| 1397 | * |
| 1398 | * NOTE: The cursor is in an indeterminant position after recursing, |
| 1399 | * but will still be suitable for an iteration. |
| 1400 | */ |
| 1401 | node = cursor->node; |
| 1402 | KKASSERT(node->ondisk->count > 0); |
| 1403 | if (node->ondisk->count == 1) { |
| 1404 | error = btree_remove(cursor); |
| 1405 | if (error == 0) { |
| 1406 | kprintf("BTREE_REMOVE: Successful!\n"); |
| 1407 | hammer_flush_node(save); |
| 1408 | hammer_free_btree(save->cluster, save->node_offset); |
| 1409 | } else { |
| 1410 | kprintf("BTREE_REMOVE: Recursion failed %d\n", error); |
| 1411 | } |
| 1412 | hammer_unlock(&save->lock); |
| 1413 | hammer_rel_node(save); |
| 1414 | return(error); |
| 1415 | } |
| 1416 | |
| 1417 | /* |
| 1418 | * Remove the element at (node, index) and adjust the parent's |
| 1419 | * subtree_count. |
| 1420 | * |
| 1421 | * NOTE! If removing element 0 an internal node's left-hand boundary |
| 1422 | * will no longer match its parent. If removing a mid-element the |
| 1423 | * boundary will no longer match a child's left hand or right hand |
| 1424 | * boundary. |
| 1425 | * |
| 1426 | * BxBxBxB remove a (x[0]): internal node's left-hand |
| 1427 | * | | | boundary no longer matches |
| 1428 | * a b c parent. |
| 1429 | * |
| 1430 | * remove b (x[1]): a's right hand boundary no |
| 1431 | * longer matches parent. |
| 1432 | * |
| 1433 | * remove c (x[2]): b's right hand boundary no |
| 1434 | * longer matches parent. |
| 1435 | * |
| 1436 | * These cases are corrected in btree_search(). |
| 1437 | */ |
| 1438 | #if 0 |
| 1439 | kprintf("BTREE_REMOVE: Removing element %d\n", cursor->index); |
| 1440 | #endif |
| 1441 | hammer_modify_node(node); |
| 1442 | ondisk = node->ondisk; |
| 1443 | i = cursor->index; |
| 1444 | bcopy(&ondisk->elms[i+1], &ondisk->elms[i], |
| 1445 | (ondisk->count - i) * sizeof(ondisk->elms[0])); |
| 1446 | --ondisk->count; |
| 1447 | hammer_modify_node_done(node); |
| 1448 | |
| 1449 | /* |
| 1450 | * Adjust the parent-parent's (now parent) reference to the parent |
| 1451 | * (now node). |
| 1452 | */ |
| 1453 | if ((parent = cursor->parent) != NULL) { |
| 1454 | elm = &parent->ondisk->elms[cursor->parent_index]; |
| 1455 | if (elm->internal.subtree_count != ondisk->count) { |
| 1456 | hammer_modify_node(parent); |
| 1457 | elm->internal.subtree_count = ondisk->count; |
| 1458 | hammer_modify_node_done(parent); |
| 1459 | } |
| 1460 | if (elm->subtree_type != HAMMER_BTREE_TYPE_CLUSTER && |
| 1461 | elm->subtree_type != ondisk->type) { |
| 1462 | hammer_modify_node(parent); |
| 1463 | elm->subtree_type = ondisk->type; |
| 1464 | hammer_modify_node_done(parent); |
| 1465 | } |
| 1466 | } |
| 1467 | |
| 1468 | /* |
| 1469 | * Free the saved node. |
| 1470 | */ |
| 1471 | hammer_flush_node(save); |
| 1472 | hammer_free_btree(save->cluster, save->node_offset); |
| 1473 | hammer_unlock(&save->lock); |
| 1474 | hammer_rel_node(save); |
| 1475 | return(0); |
| 1476 | } |
| 1477 | |
| 1478 | /* |
| 1479 | * The child represented by the element in internal node node needs |
| 1480 | * to have its parent pointer adjusted. |
| 1481 | */ |
| 1482 | static |
| 1483 | int |
| 1484 | btree_set_parent(hammer_node_t node, hammer_btree_elm_t elm) |
| 1485 | { |
| 1486 | hammer_volume_t volume; |
| 1487 | hammer_cluster_t cluster; |
| 1488 | hammer_node_t child; |
| 1489 | int error; |
| 1490 | |
| 1491 | error = 0; |
| 1492 | |
| 1493 | switch(elm->internal.subtree_type) { |
| 1494 | case HAMMER_BTREE_TYPE_LEAF: |
| 1495 | case HAMMER_BTREE_TYPE_INTERNAL: |
| 1496 | child = hammer_get_node(node->cluster, |
| 1497 | elm->internal.subtree_offset, &error); |
| 1498 | if (error == 0) { |
| 1499 | hammer_modify_node(child); |
| 1500 | hammer_lock_ex(&child->lock); |
| 1501 | child->ondisk->parent = node->node_offset; |
| 1502 | hammer_unlock(&child->lock); |
| 1503 | hammer_modify_node_done(child); |
| 1504 | hammer_rel_node(child); |
| 1505 | } |
| 1506 | break; |
| 1507 | case HAMMER_BTREE_TYPE_CLUSTER: |
| 1508 | volume = hammer_get_volume(node->cluster->volume->hmp, |
| 1509 | elm->internal.subtree_vol_no, &error); |
| 1510 | if (error) |
| 1511 | break; |
| 1512 | cluster = hammer_get_cluster(volume, |
| 1513 | elm->internal.subtree_clu_no, |
| 1514 | &error, 0); |
| 1515 | hammer_rel_volume(volume, 0); |
| 1516 | if (error) |
| 1517 | break; |
| 1518 | hammer_modify_cluster(cluster); |
| 1519 | hammer_lock_ex(&cluster->io.lock); |
| 1520 | cluster->ondisk->clu_btree_parent_offset = node->node_offset; |
| 1521 | hammer_unlock(&cluster->io.lock); |
| 1522 | hammer_modify_cluster_done(cluster); |
| 1523 | KKASSERT(cluster->ondisk->clu_btree_parent_clu_no == |
| 1524 | node->cluster->clu_no); |
| 1525 | KKASSERT(cluster->ondisk->clu_btree_parent_vol_no == |
| 1526 | node->cluster->volume->vol_no); |
| 1527 | hammer_rel_cluster(cluster, 0); |
| 1528 | break; |
| 1529 | default: |
| 1530 | hammer_print_btree_elm(elm, HAMMER_BTREE_TYPE_INTERNAL, -1); |
| 1531 | panic("btree_set_parent: bad subtree_type"); |
| 1532 | break; /* NOT REACHED */ |
| 1533 | } |
| 1534 | return(error); |
| 1535 | } |
| 1536 | |
| 1537 | #if 0 |
| 1538 | |
| 1539 | /* |
| 1540 | * This routine is called on the internal node (node) prior to recursing down |
| 1541 | * through (node, index) when the node referenced by (node, index) MIGHT |
| 1542 | * have too few elements for the caller to perform a deletion. |
| 1543 | * |
| 1544 | * cursor->index is invalid on return because the separators may have gotten |
| 1545 | * adjusted, the caller must rescan the node's elements. The caller may set |
| 1546 | * cursor->index to -1 if it wants us to do a general rebalancing. |
| 1547 | * |
| 1548 | * This routine rebalances the children of the (node), collapsing children |
| 1549 | * together if possible. On return each child will have at least L/2-1 |
| 1550 | * elements unless the node only has one child. |
| 1551 | * |
| 1552 | * NOTE: Because we do not update the parent's parent in the split code, |
| 1553 | * the subtree_count used by the caller may be incorrect. We correct it |
| 1554 | * here. Also note that we cannot change the depth of the tree's leaf |
| 1555 | * nodes here (see btree_collapse()). |
| 1556 | * |
| 1557 | * NOTE: We make no attempt to rebalance inter-cluster elements. |
| 1558 | */ |
| 1559 | static |
| 1560 | int |
| 1561 | btree_rebalance(hammer_cursor_t cursor) |
| 1562 | { |
| 1563 | hammer_node_ondisk_t ondisk; |
| 1564 | hammer_node_t node; |
| 1565 | hammer_node_t children[HAMMER_BTREE_INT_ELMS]; |
| 1566 | hammer_node_t child; |
| 1567 | hammer_btree_elm_t elm; |
| 1568 | hammer_btree_elm_t elms; |
| 1569 | int i, j, n, nelms, goal; |
| 1570 | int maxelms, halfelms; |
| 1571 | int error; |
| 1572 | |
| 1573 | /* |
| 1574 | * If the elm being recursed through is an inter-cluster reference, |
| 1575 | * don't worry about it. |
| 1576 | */ |
| 1577 | ondisk = cursor->node->ondisk; |
| 1578 | elm = &ondisk->elms[cursor->index]; |
| 1579 | if (elm->internal.subtree_type == HAMMER_BTREE_TYPE_CLUSTER) |
| 1580 | return(0); |
| 1581 | |
| 1582 | KKASSERT(elm->internal.subtree_offset != 0); |
| 1583 | error = 0; |
| 1584 | |
| 1585 | /* |
| 1586 | * Load the children of node and do any necessary corrections |
| 1587 | * to subtree_count. subtree_count may be too low due to the |
| 1588 | * way insertions split nodes. Get a count of the total number |
| 1589 | * of actual elements held by our children. |
| 1590 | */ |
| 1591 | error = 0; |
| 1592 | |
| 1593 | for (i = n = 0; i < node->base.count; ++i) { |
| 1594 | struct hammer_btree_internal_elm *elm; |
| 1595 | |
| 1596 | elm = &node->elms[i]; |
| 1597 | children[i] = NULL; |
| 1598 | child_buffer[i] = NULL; /* must be preinitialized for bread */ |
| 1599 | if (elm->subtree_offset == 0) |
| 1600 | continue; |
| 1601 | child = hammer_bread(cursor->cluster, elm->subtree_offset, |
| 1602 | HAMMER_FSBUF_BTREE, &error, |
| 1603 | &child_buffer[i], XXX); |
| 1604 | children[i] = child; |
| 1605 | if (child == NULL) |
| 1606 | continue; |
| 1607 | XXX |
| 1608 | KKASSERT(node->base.subtype == child->base.type); |
| 1609 | |
| 1610 | /* |
| 1611 | * Accumulate n for a good child, update the node's count |
| 1612 | * if it was wrong. |
| 1613 | */ |
| 1614 | if (node->elms[i].subtree_count != child->base.count) { |
| 1615 | node->elms[i].subtree_count = child->base.count; |
| 1616 | } |
| 1617 | n += node->elms[i].subtree_count; |
| 1618 | } |
| 1619 | if (error) |
| 1620 | goto failed; |
| 1621 | |
| 1622 | /* |
| 1623 | * Collect all the children's elements together |
| 1624 | */ |
| 1625 | nelms = n; |
| 1626 | elms = kmalloc(sizeof(*elms) * (nelms + 1), M_HAMMER, M_WAITOK|M_ZERO); |
| 1627 | for (i = n = 0; i < node->base.count; ++i) { |
| 1628 | child = children[i]; |
| 1629 | for (j = 0; j < child->base.count; ++j) { |
| 1630 | elms[n].owner = child; |
| 1631 | if (node->base.subtype == HAMMER_BTREE_TYPE_LEAF) |
| 1632 | elms[n].u.leaf = child->leaf.elms[j]; |
| 1633 | else |
| 1634 | elms[n].u.internal = child->internal.elms[j]; |
| 1635 | ++n; |
| 1636 | } |
| 1637 | } |
| 1638 | KKASSERT(n == nelms); |
| 1639 | |
| 1640 | /* |
| 1641 | * Store a boundary in the elms array to ease the code below. This |
| 1642 | * is only used if the children are internal nodes. |
| 1643 | */ |
| 1644 | elms[n].u.internal = node->elms[i]; |
| 1645 | |
| 1646 | /* |
| 1647 | * Calculate the number of elements each child should have (goal) by |
| 1648 | * reducing the number of elements until we achieve at least |
| 1649 | * halfelms - 1 per child, unless we are a degenerate case. |
| 1650 | */ |
| 1651 | maxelms = btree_max_elements(node->base.subtype); |
| 1652 | halfelms = maxelms / 2; |
| 1653 | |
| 1654 | goal = halfelms - 1; |
| 1655 | while (i && n / i < goal) |
| 1656 | --i; |
| 1657 | |
| 1658 | /* |
| 1659 | * Now rebalance using the specified goal |
| 1660 | */ |
| 1661 | for (i = n = 0; i < node->base.count; ++i) { |
| 1662 | struct hammer_buffer *subchild_buffer = NULL; |
| 1663 | struct hammer_btree_internal_node *subchild; |
| 1664 | |
| 1665 | child = children[i]; |
| 1666 | for (j = 0; j < goal && n < nelms; ++j) { |
| 1667 | if (node->base.subtype == HAMMER_BTREE_TYPE_LEAF) { |
| 1668 | child->leaf.elms[j] = elms[n].u.leaf; |
| 1669 | } else { |
| 1670 | child->internal.elms[j] = elms[n].u.internal; |
| 1671 | } |
| 1672 | |
| 1673 | /* |
| 1674 | * If the element's parent has changed we have to |
| 1675 | * update the parent pointer. This is somewhat |
| 1676 | * expensive. |
| 1677 | */ |
| 1678 | if (elms[n].owner != child && |
| 1679 | node->base.subtype == HAMMER_BTREE_TYPE_INTERNAL) { |
| 1680 | subchild = hammer_bread(cursor->cluster, |
| 1681 | elms[n].u.internal.subtree_offset, |
| 1682 | HAMMER_FSBUF_BTREE, |
| 1683 | &error, |
| 1684 | &subchild_buffer, XXX); |
| 1685 | if (subchild) { |
| 1686 | hammer_modify_buffer(subchild_buffer); |
| 1687 | subchild->base.parent = |
| 1688 | hammer_bclu_offset(child_buffer[i], |
| 1689 | child); |
| 1690 | hammer_modify_buffer_done(subchild_buffer); |
| 1691 | } |
| 1692 | /* XXX error */ |
| 1693 | } |
| 1694 | ++n; |
| 1695 | } |
| 1696 | /* |
| 1697 | * Set right boundary if the children are internal nodes. |
| 1698 | */ |
| 1699 | if (node->base.subtype == HAMMER_BTREE_TYPE_INTERNAL) |
| 1700 | child->internal.elms[j] = elms[n].u.internal; |
| 1701 | child->base.count = j; |
| 1702 | hammer_modify_buffer(child_buffer[i]); |
| 1703 | if (subchild_buffer) |
| 1704 | hammer_put_buffer(subchild_buffer, 0); |
| 1705 | |
| 1706 | /* |
| 1707 | * If we have run out of elements, break out |
| 1708 | */ |
| 1709 | if (n == nelms) |
| 1710 | break; |
| 1711 | } |
| 1712 | |
| 1713 | /* |
| 1714 | * Physically destroy any left-over children. These children's |
| 1715 | * elements have been packed into prior children. The node's |
| 1716 | * right hand boundary and count gets shifted to index i. |
| 1717 | * |
| 1718 | * The subtree count in the node's parent MUST be updated because |
| 1719 | * we are removing elements. The subtree_count field is allowed to |
| 1720 | * be too small, but not too large! |
| 1721 | */ |
| 1722 | if (i != node->base.count) { |
| 1723 | n = i; |
| 1724 | node->elms[n] = node->elms[node->base.count]; |
| 1725 | while (i < node->base.count) { |
| 1726 | hammer_free_btree_ptr(child_buffer[i], children[i]); |
| 1727 | hammer_put_buffer(child_buffer[i], 0); |
| 1728 | ++i; |
| 1729 | } |
| 1730 | node->base.count = n; |
| 1731 | if (cursor->parent) { |
| 1732 | cursor->parent->elms[cursor->parent_index].subtree_count = n; |
| 1733 | hammer_modify_buffer(cursor->parent_buffer); |
| 1734 | } |
| 1735 | } |
| 1736 | |
| 1737 | kfree(elms, M_HAMMER); |
| 1738 | failed: |
| 1739 | hammer_modify_buffer(cursor->node_buffer); |
| 1740 | for (i = 0; i < node->base.count; ++i) { |
| 1741 | if (child_buffer[i]) |
| 1742 | hammer_put_buffer(child_buffer[i], 0); |
| 1743 | } |
| 1744 | return (error); |
| 1745 | } |
| 1746 | |
| 1747 | /* |
| 1748 | * This routine is only called if the cursor is at the root node and the |
| 1749 | * root node is an internal node. We attempt to collapse the root node |
| 1750 | * by replacing it with all of its children, reducing tree depth by one. |
| 1751 | * |
| 1752 | * This is the only way to reduce tree depth in a HAMMER filesystem. |
| 1753 | * Note that all leaf nodes are at the same depth. |
| 1754 | * |
| 1755 | * This is a fairly expensive operation because we not only have to load |
| 1756 | * the root's children, we also have to scan each child and adjust the |
| 1757 | * parent offset for each element in each child. Nasty all around. |
| 1758 | */ |
| 1759 | static |
| 1760 | int |
| 1761 | btree_collapse(hammer_cursor_t cursor) |
| 1762 | { |
| 1763 | hammer_btree_node_ondisk_t root, child; |
| 1764 | hammer_btree_node_ondisk_t children[HAMMER_BTREE_INT_ELMS]; |
| 1765 | struct hammer_buffer *child_buffer[HAMMER_BTREE_INT_ELMS]; |
| 1766 | int count; |
| 1767 | int i, j, n; |
| 1768 | int root_modified; |
| 1769 | int error; |
| 1770 | int32_t root_offset; |
| 1771 | u_int8_t subsubtype; |
| 1772 | |
| 1773 | root = cursor->node; |
| 1774 | count = root->base.count; |
| 1775 | root_offset = hammer_bclu_offset(cursor->node_buffer, root); |
| 1776 | |
| 1777 | /* |
| 1778 | * Sum up the number of children each element has. This value is |
| 1779 | * only approximate due to the way the insertion node works. It |
| 1780 | * may be too small but it will never be too large. |
| 1781 | * |
| 1782 | * Quickly terminate the collapse if the elements have too many |
| 1783 | * children. |
| 1784 | */ |
| 1785 | KKASSERT(root->base.parent == 0); /* must be root node */ |
| 1786 | KKASSERT(root->base.type == HAMMER_BTREE_TYPE_INTERNAL); |
| 1787 | KKASSERT(count <= HAMMER_BTREE_INT_ELMS); |
| 1788 | |
| 1789 | for (i = n = 0; i < count; ++i) { |
| 1790 | n += root->internal.elms[i].subtree_count; |
| 1791 | } |
| 1792 | if (n > btree_max_elements(root->base.subtype)) |
| 1793 | return(0); |
| 1794 | |
| 1795 | /* |
| 1796 | * Iterate through the elements again and correct the subtree_count. |
| 1797 | * Terminate the collapse if we wind up with too many. |
| 1798 | */ |
| 1799 | error = 0; |
| 1800 | root_modified = 0; |
| 1801 | |
| 1802 | for (i = n = 0; i < count; ++i) { |
| 1803 | struct hammer_btree_internal_elm *elm; |
| 1804 | |
| 1805 | elm = &root->internal.elms[i]; |
| 1806 | child_buffer[i] = NULL; |
| 1807 | children[i] = NULL; |
| 1808 | if (elm->subtree_offset == 0) |
| 1809 | continue; |
| 1810 | child = hammer_bread(cursor->cluster, elm->subtree_offset, |
| 1811 | HAMMER_FSBUF_BTREE, &error, |
| 1812 | &child_buffer[i], XXX); |
| 1813 | children[i] = child; |
| 1814 | if (child == NULL) |
| 1815 | continue; |
| 1816 | KKASSERT(root->base.subtype == child->base.type); |
| 1817 | |
| 1818 | /* |
| 1819 | * Accumulate n for a good child, update the root's count |
| 1820 | * if it was wrong. |
| 1821 | */ |
| 1822 | if (root->internal.elms[i].subtree_count != child->base.count) { |
| 1823 | root->internal.elms[i].subtree_count = child->base.count; |
| 1824 | root_modified = 1; |
| 1825 | } |
| 1826 | n += root->internal.elms[i].subtree_count; |
| 1827 | } |
| 1828 | if (error || n > btree_max_elements(root->base.subtype)) |
| 1829 | goto done; |
| 1830 | |
| 1831 | /* |
| 1832 | * Ok, we can collapse the root. If the root's children are leafs |
| 1833 | * the collapse is really simple. If they are internal nodes the |
| 1834 | * collapse is not so simple because we have to fixup the parent |
| 1835 | * pointers for the root's children's children. |
| 1836 | * |
| 1837 | * When collapsing an internal node the far left and far right |
| 1838 | * element's boundaries should match the root's left and right |
| 1839 | * boundaries. |
| 1840 | */ |
| 1841 | if (root->base.subtype == HAMMER_BTREE_TYPE_LEAF) { |
| 1842 | for (i = n = 0; i < count; ++i) { |
| 1843 | child = children[i]; |
| 1844 | for (j = 0; j < child->base.count; ++j) { |
| 1845 | root->leaf.elms[n] = child->leaf.elms[j]; |
| 1846 | ++n; |
| 1847 | } |
| 1848 | } |
| 1849 | root->base.type = root->base.subtype; |
| 1850 | root->base.subtype = 0; |
| 1851 | root->base.count = n; |
| 1852 | root->leaf.link_left = 0; |
| 1853 | root->leaf.link_right = 0; |
| 1854 | } else { |
| 1855 | struct hammer_btree_internal_elm *elm; |
| 1856 | struct hammer_btree_internal_node *subchild; |
| 1857 | struct hammer_buffer *subchild_buffer = NULL; |
| 1858 | |
| 1859 | if (count) { |
| 1860 | child = children[0]; |
| 1861 | subsubtype = child->base.subtype; |
| 1862 | KKASSERT(child->base.count > 0); |
| 1863 | KKASSERT(root->internal.elms[0].base.key == |
| 1864 | child->internal.elms[0].base.key); |
| 1865 | child = children[count-1]; |
| 1866 | KKASSERT(child->base.count > 0); |
| 1867 | KKASSERT(root->internal.elms[count].base.key == |
| 1868 | child->internal.elms[child->base.count].base.key); |
| 1869 | } else { |
| 1870 | subsubtype = 0; |
| 1871 | } |
| 1872 | for (i = n = 0; i < count; ++i) { |
| 1873 | child = children[i]; |
| 1874 | KKASSERT(child->base.subtype == subsubtype); |
| 1875 | for (j = 0; j < child->base.count; ++j) { |
| 1876 | elm = &child->internal.elms[j]; |
| 1877 | |
| 1878 | root->internal.elms[n] = *elm; |
| 1879 | subchild = hammer_bread(cursor->cluster, |
| 1880 | elm->subtree_offset, |
| 1881 | HAMMER_FSBUF_BTREE, |
| 1882 | &error, |
| 1883 | &subchild_buffer, |
| 1884 | XXX); |
| 1885 | if (subchild) { |
| 1886 | subchild->base.parent = root_offset; |
| 1887 | hammer_modify_buffer(subchild_buffer); |
| 1888 | } |
| 1889 | ++n; |
| 1890 | } |
| 1891 | /* make sure the right boundary is correct */ |
| 1892 | /* (this gets overwritten when the loop continues) */ |
| 1893 | /* XXX generate a new separator? */ |
| 1894 | root->internal.elms[n] = child->internal.elms[j]; |
| 1895 | } |
| 1896 | root->base.type = HAMMER_BTREE_TYPE_INTERNAL; |
| 1897 | root->base.subtype = subsubtype; |
| 1898 | if (subchild_buffer) |
| 1899 | hammer_put_buffer(subchild_buffer, 0); |
| 1900 | } |
| 1901 | root_modified = 1; |
| 1902 | |
| 1903 | /* |
| 1904 | * Cleanup |
| 1905 | */ |
| 1906 | done: |
| 1907 | if (root_modified) |
| 1908 | hammer_modify_buffer(cursor->node_buffer); |
| 1909 | for (i = 0; i < count; ++i) { |
| 1910 | if (child_buffer[i]) |
| 1911 | hammer_put_buffer(child_buffer[i], 0); |
| 1912 | } |
| 1913 | return(error); |
| 1914 | } |
| 1915 | |
| 1916 | #endif |
| 1917 | |
| 1918 | /************************************************************************ |
| 1919 | * MISCELLANIOUS SUPPORT * |
| 1920 | ************************************************************************/ |
| 1921 | |
| 1922 | /* |
| 1923 | * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp). |
| 1924 | * |
| 1925 | * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c. |
| 1926 | */ |
| 1927 | int |
| 1928 | hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2) |
| 1929 | { |
| 1930 | if (key1->obj_id < key2->obj_id) |
| 1931 | return(-4); |
| 1932 | if (key1->obj_id > key2->obj_id) |
| 1933 | return(4); |
| 1934 | |
| 1935 | if (key1->rec_type < key2->rec_type) |
| 1936 | return(-3); |
| 1937 | if (key1->rec_type > key2->rec_type) |
| 1938 | return(3); |
| 1939 | |
| 1940 | if (key1->key < key2->key) |
| 1941 | return(-2); |
| 1942 | if (key1->key > key2->key) |
| 1943 | return(2); |
| 1944 | return(0); |
| 1945 | } |
| 1946 | |
| 1947 | /* |
| 1948 | * Test a non-zero timestamp against an element to determine whether the |
| 1949 | * element is visible. |
| 1950 | */ |
| 1951 | int |
| 1952 | hammer_btree_chkts(hammer_tid_t create_tid, hammer_base_elm_t base) |
| 1953 | { |
| 1954 | if (create_tid < base->create_tid) |
| 1955 | return(-1); |
| 1956 | if (base->delete_tid && create_tid >= base->delete_tid) |
| 1957 | return(1); |
| 1958 | return(0); |
| 1959 | } |
| 1960 | |
| 1961 | /* |
| 1962 | * Create a separator half way inbetween key1 and key2. For fields just |
| 1963 | * one unit apart, the separator will match key2. |
| 1964 | * |
| 1965 | * The handling of delete_tid is a little confusing. It is only possible |
| 1966 | * to have one record in the B-Tree where all fields match except delete_tid. |
| 1967 | * This means, worse case, two adjacent elements may have a create_tid that |
| 1968 | * is one-apart and cause the separator to choose the right-hand element's |
| 1969 | * create_tid. e.g. (create,delete): (1,x)(2,x) -> separator is (2,x). |
| 1970 | * |
| 1971 | * So all we have to do is set delete_tid to the right-hand element to |
| 1972 | * guarentee that the separator is properly between the two elements. |
| 1973 | */ |
| 1974 | #define MAKE_SEPARATOR(key1, key2, dest, field) \ |
| 1975 | dest->field = key1->field + ((key2->field - key1->field + 1) >> 1); |
| 1976 | |
| 1977 | static void |
| 1978 | hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2, |
| 1979 | hammer_base_elm_t dest) |
| 1980 | { |
| 1981 | bzero(dest, sizeof(*dest)); |
| 1982 | MAKE_SEPARATOR(key1, key2, dest, obj_id); |
| 1983 | MAKE_SEPARATOR(key1, key2, dest, rec_type); |
| 1984 | MAKE_SEPARATOR(key1, key2, dest, key); |
| 1985 | MAKE_SEPARATOR(key1, key2, dest, create_tid); |
| 1986 | dest->delete_tid = key2->delete_tid; |
| 1987 | } |
| 1988 | |
| 1989 | #undef MAKE_SEPARATOR |
| 1990 | |
| 1991 | /* |
| 1992 | * Return whether a generic internal or leaf node is full |
| 1993 | */ |
| 1994 | static int |
| 1995 | btree_node_is_full(hammer_node_ondisk_t node) |
| 1996 | { |
| 1997 | switch(node->type) { |
| 1998 | case HAMMER_BTREE_TYPE_INTERNAL: |
| 1999 | if (node->count == HAMMER_BTREE_INT_ELMS) |
| 2000 | return(1); |
| 2001 | break; |
| 2002 | case HAMMER_BTREE_TYPE_LEAF: |
| 2003 | if (node->count == HAMMER_BTREE_LEAF_ELMS) |
| 2004 | return(1); |
| 2005 | break; |
| 2006 | default: |
| 2007 | panic("illegal btree subtype"); |
| 2008 | } |
| 2009 | return(0); |
| 2010 | } |
| 2011 | |
| 2012 | #if 0 |
| 2013 | static int |
| 2014 | btree_max_elements(u_int8_t type) |
| 2015 | { |
| 2016 | if (type == HAMMER_BTREE_TYPE_LEAF) |
| 2017 | return(HAMMER_BTREE_LEAF_ELMS); |
| 2018 | if (type == HAMMER_BTREE_TYPE_INTERNAL) |
| 2019 | return(HAMMER_BTREE_INT_ELMS); |
| 2020 | panic("btree_max_elements: bad type %d\n", type); |
| 2021 | } |
| 2022 | #endif |
| 2023 | |
| 2024 | void |
| 2025 | hammer_print_btree_node(hammer_node_ondisk_t ondisk) |
| 2026 | { |
| 2027 | hammer_btree_elm_t elm; |
| 2028 | int i; |
| 2029 | |
| 2030 | kprintf("node %p count=%d parent=%d type=%c\n", |
| 2031 | ondisk, ondisk->count, ondisk->parent, ondisk->type); |
| 2032 | |
| 2033 | /* |
| 2034 | * Dump both boundary elements if an internal node |
| 2035 | */ |
| 2036 | if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) { |
| 2037 | for (i = 0; i <= ondisk->count; ++i) { |
| 2038 | elm = &ondisk->elms[i]; |
| 2039 | hammer_print_btree_elm(elm, ondisk->type, i); |
| 2040 | } |
| 2041 | } else { |
| 2042 | for (i = 0; i < ondisk->count; ++i) { |
| 2043 | elm = &ondisk->elms[i]; |
| 2044 | hammer_print_btree_elm(elm, ondisk->type, i); |
| 2045 | } |
| 2046 | } |
| 2047 | } |
| 2048 | |
| 2049 | void |
| 2050 | hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i) |
| 2051 | { |
| 2052 | kprintf(" %2d", i); |
| 2053 | kprintf("\tobjid = %016llx\n", elm->base.obj_id); |
| 2054 | kprintf("\tkey = %016llx\n", elm->base.key); |
| 2055 | kprintf("\tcreate_tid = %016llx\n", elm->base.create_tid); |
| 2056 | kprintf("\tdelete_tid = %016llx\n", elm->base.delete_tid); |
| 2057 | kprintf("\trec_type = %04x\n", elm->base.rec_type); |
| 2058 | kprintf("\tobj_type = %02x\n", elm->base.obj_type); |
| 2059 | kprintf("\tsubtree_type = %02x\n", elm->subtree_type); |
| 2060 | |
| 2061 | if (type == HAMMER_BTREE_TYPE_INTERNAL) { |
| 2062 | if (elm->internal.rec_offset) { |
| 2063 | kprintf("\tcluster_rec = %08x\n", |
| 2064 | elm->internal.rec_offset); |
| 2065 | kprintf("\tcluster_id = %08x\n", |
| 2066 | elm->internal.subtree_clu_no); |
| 2067 | kprintf("\tvolno = %08x\n", |
| 2068 | elm->internal.subtree_vol_no); |
| 2069 | } else { |
| 2070 | kprintf("\tsubtree_off = %08x\n", |
| 2071 | elm->internal.subtree_offset); |
| 2072 | } |
| 2073 | kprintf("\tsubtree_count= %d\n", elm->internal.subtree_count); |
| 2074 | } else { |
| 2075 | kprintf("\trec_offset = %08x\n", elm->leaf.rec_offset); |
| 2076 | kprintf("\tdata_offset = %08x\n", elm->leaf.data_offset); |
| 2077 | kprintf("\tdata_len = %08x\n", elm->leaf.data_len); |
| 2078 | kprintf("\tdata_crc = %08x\n", elm->leaf.data_crc); |
| 2079 | } |
| 2080 | } |