ctree.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include "kerncompat.h"
   4 #include "radix-tree.h"
   5 #include "ctree.h"
   6 #include "disk-io.h"
   7 #include "print-tree.h"
   8
   9 static int split_node(struct ctree_root *root, struct ctree_path *path,
  10                       int level);
  11 static int split_leaf(struct ctree_root *root, struct ctree_path *path,
  12                       int data_size);
  13 static int push_node_left(struct ctree_root *root, struct tree_buffer *dst,
  14                           struct tree_buffer *src);
  15 static int balance_node_right(struct ctree_root *root,
  16                               struct tree_buffer *dst_buf,
  17                               struct tree_buffer *src_buf);
  18 static int del_ptr(struct ctree_root *root, struct ctree_path *path, int level,
  19                    int slot);
  20
  21 inline void init_path(struct ctree_path *p)
  22 {
  23         memset(p, 0, sizeof(*p));
  24 }
  25
  26 void release_path(struct ctree_root *root, struct ctree_path *p)
  27 {
  28         int i;
  29         for (i = 0; i < MAX_LEVEL; i++) {
  30                 if (!p->nodes[i])
  31                         break;
  32                 tree_block_release(root, p->nodes[i]);
  33         }
  34         memset(p, 0, sizeof(*p));
  35 }
  36
  37 /*
  38  * The leaf data grows from end-to-front in the node.
  39  * this returns the address of the start of the last item,
  40  * which is the stop of the leaf data stack
  41  */
  42 static inline unsigned int leaf_data_end(struct leaf *leaf)
  43 {
  44         unsigned int nr = leaf->header.nritems;
  45         if (nr == 0)
  46                 return sizeof(leaf->data);
  47         return leaf->items[nr-1].offset;
  48 }
  49
  50 /*
  51  * The space between the end of the leaf items and
  52  * the start of the leaf data.  IOW, how much room
  53  * the leaf has left for both items and data
  54  */
  55 int leaf_free_space(struct leaf *leaf)
  56 {
  57         int data_end = leaf_data_end(leaf);
  58         int nritems = leaf->header.nritems;
  59         char *items_end = (char *)(leaf->items + nritems + 1);
  60         return (char *)(leaf->data + data_end) - (char *)items_end;
  61 }
  62
  63 /*
  64  * compare two keys in a memcmp fashion
  65  */
  66 int comp_keys(struct key *k1, struct key *k2)
  67 {
  68         if (k1->objectid > k2->objectid)
  69                 return 1;
  70         if (k1->objectid < k2->objectid)
  71                 return -1;
  72         if (k1->flags > k2->flags)
  73                 return 1;
  74         if (k1->flags < k2->flags)
  75                 return -1;
  76         if (k1->offset > k2->offset)
  77                 return 1;
  78         if (k1->offset < k2->offset)
  79                 return -1;
  80         return 0;
  81 }
  82
  83 int check_node(struct ctree_path *path, int level)
  84 {
  85         int i;
  86         struct node *parent = NULL;
  87         struct node *node = &path->nodes[level]->node;
  88         int parent_slot;
  89
  90         if (path->nodes[level + 1])
  91                 parent = &path->nodes[level + 1]->node;
  92         parent_slot = path->slots[level + 1];
  93         if (parent && node->header.nritems > 0) {
  94                 struct key *parent_key;
  95                 parent_key = &parent->keys[parent_slot];
  96                 BUG_ON(memcmp(parent_key, node->keys, sizeof(struct key)));
  97                 BUG_ON(parent->blockptrs[parent_slot] != node->header.blocknr);
  98         }
  99         BUG_ON(node->header.nritems > NODEPTRS_PER_BLOCK);
 100         for (i = 0; i < node->header.nritems - 2; i++) {
 101                 BUG_ON(comp_keys(&node->keys[i], &node->keys[i+1]) >= 0);
 102         }
 103         return 0;
 104 }
 105
 106 int check_leaf(struct ctree_path *path, int level)
 107 {
 108         int i;
 109         struct leaf *leaf = &path->nodes[level]->leaf;
 110         struct node *parent = NULL;
 111         int parent_slot;
 112
 113         if (path->nodes[level + 1])
 114                 parent = &path->nodes[level + 1]->node;
 115         parent_slot = path->slots[level + 1];
 116         if (parent && leaf->header.nritems > 0) {
 117                 struct key *parent_key;
 118                 parent_key = &parent->keys[parent_slot];
 119                 BUG_ON(memcmp(parent_key, &leaf->items[0].key,
 120                        sizeof(struct key)));
 121                 BUG_ON(parent->blockptrs[parent_slot] != leaf->header.blocknr);
 122         }
 123         for (i = 0; i < leaf->header.nritems - 2; i++) {
 124                 BUG_ON(comp_keys(&leaf->items[i].key,
 125                                  &leaf->items[i+1].key) >= 0);
 126                 BUG_ON(leaf->items[i].offset != leaf->items[i + 1].offset +
 127                     leaf->items[i + 1].size);
 128                 if (i == 0) {
 129                         BUG_ON(leaf->items[i].offset + leaf->items[i].size !=
 130                                 LEAF_DATA_SIZE);
 131                 }
 132         }
 133         BUG_ON(leaf_free_space(leaf) < 0);
 134         return 0;
 135 }
 136
 137 int check_block(struct ctree_path *path, int level)
 138 {
 139         if (level == 0)
 140                 return check_leaf(path, level);
 141         return check_node(path, level);
 142 }
 143
 144 /*
 145  * search for key in the array p.  items p are item_size apart
 146  * and there are 'max' items in p
 147  * the slot in the array is returned via slot, and it points to
 148  * the place where you would insert key if it is not found in
 149  * the array.
 150  *
 151  * slot may point to max if the key is bigger than all of the keys
 152  */
 153 int generic_bin_search(char *p, int item_size, struct key *key,
 154                        int max, int *slot)
 155 {
 156         int low = 0;
 157         int high = max;
 158         int mid;
 159         int ret;
 160         struct key *tmp;
 161
 162         while(low < high) {
 163                 mid = (low + high) / 2;
 164                 tmp = (struct key *)(p + mid * item_size);
 165                 ret = comp_keys(tmp, key);
 166
 167                 if (ret < 0)
 168                         low = mid + 1;
 169                 else if (ret > 0)
 170                         high = mid;
 171                 else {
 172                         *slot = mid;
 173                         return 0;
 174                 }
 175         }
 176         *slot = low;
 177         return 1;
 178 }
 179
 180 /*
 181  * simple bin_search frontend that does the right thing for
 182  * leaves vs nodes
 183  */
 184 int bin_search(struct node *c, struct key *key, int *slot)
 185 {
 186         if (is_leaf(c->header.flags)) {
 187                 struct leaf *l = (struct leaf *)c;
 188                 return generic_bin_search((void *)l->items, sizeof(struct item),
 189                                           key, c->header.nritems, slot);
 190         } else {
 191                 return generic_bin_search((void *)c->keys, sizeof(struct key),
 192                                           key, c->header.nritems, slot);
 193         }
 194         return -1;
 195 }
 196
 197 struct tree_buffer *read_node_slot(struct ctree_root *root,
 198                                    struct tree_buffer *parent_buf,
 199                                    int slot)
 200 {
 201         struct node *node = &parent_buf->node;
 202         if (slot < 0)
 203                 return NULL;
 204         if (slot >= node->header.nritems)
 205                 return NULL;
 206         return read_tree_block(root, node->blockptrs[slot]);
 207 }
 208
 209 static int balance_level(struct ctree_root *root, struct ctree_path *path,
 210                         int level)
 211 {
 212         struct tree_buffer *right_buf;
 213         struct tree_buffer *mid_buf;
 214         struct tree_buffer *left_buf;
 215         struct tree_buffer *parent_buf = NULL;
 216         struct node *right = NULL;
 217         struct node *mid;
 218         struct node *left = NULL;
 219         struct node *parent = NULL;
 220         int ret = 0;
 221         int wret;
 222         int pslot;
 223         int orig_slot = path->slots[level];
 224         u64 orig_ptr;
 225
 226         if (level == 0)
 227                 return 0;
 228
 229         mid_buf = path->nodes[level];
 230         mid = &mid_buf->node;
 231         orig_ptr = mid->blockptrs[orig_slot];
 232
 233         if (level < MAX_LEVEL - 1)
 234                 parent_buf = path->nodes[level + 1];
 235         pslot = path->slots[level + 1];
 236
 237         if (!parent_buf) {
 238                 struct tree_buffer *child;
 239                 u64 blocknr = mid_buf->blocknr;
 240
 241                 if (mid->header.nritems != 1)
 242                         return 0;
 243
 244                 /* promote the child to a root */
 245                 child = read_node_slot(root, mid_buf, 0);
 246                 BUG_ON(!child);
 247                 root->node = child;
 248                 path->nodes[level] = NULL;
 249                 /* once for the path */
 250                 tree_block_release(root, mid_buf);
 251                 /* once for the root ptr */
 252                 tree_block_release(root, mid_buf);
 253                 return free_extent(root, blocknr, 1);
 254         }
 255         parent = &parent_buf->node;
 256
 257         if (mid->header.nritems > NODEPTRS_PER_BLOCK / 4)
 258                 return 0;
 259
 260         left_buf = read_node_slot(root, parent_buf, pslot - 1);
 261         right_buf = read_node_slot(root, parent_buf, pslot + 1);
 262
 263         /* first, try to make some room in the middle buffer */
 264         if (left_buf) {
 265                 left = &left_buf->node;
 266                 orig_slot += left->header.nritems;
 267                 wret = push_node_left(root, left_buf, mid_buf);
 268                 if (wret < 0)
 269                         ret = wret;
 270         }
 271
 272         /*
 273          * then try to empty the right most buffer into the middle
 274          */
 275         if (right_buf) {
 276                 right = &right_buf->node;
 277                 wret = push_node_left(root, mid_buf, right_buf);
 278                 if (wret < 0)
 279                         ret = wret;
 280                 if (right->header.nritems == 0) {
 281                         u64 blocknr = right_buf->blocknr;
 282                         tree_block_release(root, right_buf);
 283                         right_buf = NULL;
 284                         right = NULL;
 285                         wret = del_ptr(root, path, level + 1, pslot + 1);
 286                         if (wret)
 287                                 ret = wret;
 288                         wret = free_extent(root, blocknr, 1);
 289                         if (wret)
 290                                 ret = wret;
 291                 } else {
 292                         memcpy(parent->keys + pslot + 1, right->keys,
 293                                 sizeof(struct key));
 294                         wret = write_tree_block(root, parent_buf);
 295                         if (wret)
 296                                 ret = wret;
 297                 }
 298         }
 299         if (mid->header.nritems == 1) {
 300                 /*
 301                  * we're not allowed to leave a node with one item in the
 302                  * tree during a delete.  A deletion from lower in the tree
 303                  * could try to delete the only pointer in this node.
 304                  * So, pull some keys from the left.
 305                  * There has to be a left pointer at this point because
 306                  * otherwise we would have pulled some pointers from the
 307                  * right
 308                  */
 309                 BUG_ON(!left_buf);
 310                 wret = balance_node_right(root, mid_buf, left_buf);
 311                 if (wret < 0)
 312                         ret = wret;
 313                 BUG_ON(wret == 1);
 314         }
 315         if (mid->header.nritems == 0) {
 316                 /* we've managed to empty the middle node, drop it */
 317                 u64 blocknr = mid_buf->blocknr;
 318                 tree_block_release(root, mid_buf);
 319                 mid_buf = NULL;
 320                 mid = NULL;
 321                 wret = del_ptr(root, path, level + 1, pslot);
 322                 if (wret)
 323                         ret = wret;
 324                 wret = free_extent(root, blocknr, 1);
 325                 if (wret)
 326                         ret = wret;
 327         } else {
 328                 /* update the parent key to reflect our changes */
 329                 memcpy(parent->keys + pslot, mid->keys, sizeof(struct key));
 330                 wret = write_tree_block(root, parent_buf);
 331                 if (wret)
 332                         ret = wret;
 333         }
 334
 335         /* update the path */
 336         if (left_buf) {
 337                 if (left->header.nritems > orig_slot) {
 338                         left_buf->count++; // released below
 339                         path->nodes[level] = left_buf;
 340                         path->slots[level + 1] -= 1;
 341                         path->slots[level] = orig_slot;
 342                         if (mid_buf)
 343                                 tree_block_release(root, mid_buf);
 344                 } else {
 345                         orig_slot -= left->header.nritems;
 346                         path->slots[level] = orig_slot;
 347                 }
 348         }
 349         /* double check we haven't messed things up */
 350         check_block(path, level);
 351         if (orig_ptr != path->nodes[level]->node.blockptrs[path->slots[level]])
 352                 BUG();
 353
 354         if (right_buf)
 355                 tree_block_release(root, right_buf);
 356         if (left_buf)
 357                 tree_block_release(root, left_buf);
 358         return ret;
 359 }
 360
 361 /*
 362  * look for key in the tree.  path is filled in with nodes along the way
 363  * if key is found, we return zero and you can find the item in the leaf
 364  * level of the path (level 0)
 365  *
 366  * If the key isn't found, the path points to the slot where it should
 367  * be inserted, and 1 is returned.  If there are other errors during the
 368  * search a negative error number is returned.
 369  *
 370  * if ins_len > 0, nodes and leaves will be split as we walk down the
 371  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
 372  * possible)
 373  */
 374 int search_slot(struct ctree_root *root, struct key *key,
 375                 struct ctree_path *p, int ins_len)
 376 {
 377         struct tree_buffer *b;
 378         struct node *c;
 379         int slot;
 380         int ret;
 381         int level;
 382
 383 again:
 384         b = root->node;
 385         b->count++;
 386         while (b) {
 387                 c = &b->node;
 388                 level = node_level(c->header.flags);
 389                 p->nodes[level] = b;
 390                 ret = check_block(p, level);
 391                 if (ret)
 392                         return -1;
 393                 ret = bin_search(c, key, &slot);
 394                 if (!is_leaf(c->header.flags)) {
 395                         if (ret && slot > 0)
 396                                 slot -= 1;
 397                         p->slots[level] = slot;
 398                         if (ins_len > 0 &&
 399                             c->header.nritems == NODEPTRS_PER_BLOCK) {
 400                                 int sret = split_node(root, p, level);
 401                                 BUG_ON(sret > 0);
 402                                 if (sret)
 403                                         return sret;
 404                                 b = p->nodes[level];
 405                                 c = &b->node;
 406                                 slot = p->slots[level];
 407                         } else if (ins_len < 0) {
 408                                 int sret = balance_level(root, p, level);
 409                                 if (sret)
 410                                         return sret;
 411                                 b = p->nodes[level];
 412                                 if (!b)
 413                                         goto again;
 414                                 c = &b->node;
 415                                 slot = p->slots[level];
 416                                 BUG_ON(c->header.nritems == 1);
 417                         }
 418                         b = read_tree_block(root, c->blockptrs[slot]);
 419                 } else {
 420                         struct leaf *l = (struct leaf *)c;
 421                         p->slots[level] = slot;
 422                         if (ins_len > 0 && leaf_free_space(l) <
 423                             sizeof(struct item) + ins_len) {
 424                                 int sret = split_leaf(root, p, ins_len);
 425                                 BUG_ON(sret > 0);
 426                                 if (sret)
 427                                         return sret;
 428                         }
 429                         BUG_ON(root->node->count == 1);
 430                         return ret;
 431                 }
 432         }
 433         BUG_ON(root->node->count == 1);
 434         return 1;
 435 }
 436
 437 /*
 438  * adjust the pointers going up the tree, starting at level
 439  * making sure the right key of each node is points to 'key'.
 440  * This is used after shifting pointers to the left, so it stops
 441  * fixing up pointers when a given leaf/node is not in slot 0 of the
 442  * higher levels
 443  *
 444  * If this fails to write a tree block, it returns -1, but continues
 445  * fixing up the blocks in ram so the tree is consistent.
 446  */
 447 static int fixup_low_keys(struct ctree_root *root,
 448                            struct ctree_path *path, struct key *key,
 449                            int level)
 450 {
 451         int i;
 452         int ret = 0;
 453         int wret;
 454         for (i = level; i < MAX_LEVEL; i++) {
 455                 struct node *t;
 456                 int tslot = path->slots[i];
 457                 if (!path->nodes[i])
 458                         break;
 459                 t = &path->nodes[i]->node;
 460                 memcpy(t->keys + tslot, key, sizeof(*key));
 461                 wret = write_tree_block(root, path->nodes[i]);
 462                 if (wret)
 463                         ret = wret;
 464                 if (tslot != 0)
 465                         break;
 466         }
 467         return ret;
 468 }
 469
 470 /*
 471  * try to push data from one node into the next node left in the
 472  * tree.
 473  *
 474  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
 475  * error, and > 0 if there was no room in the left hand block.
 476  */
 477 static int push_node_left(struct ctree_root *root, struct tree_buffer *dst_buf,
 478                           struct tree_buffer *src_buf)
 479 {
 480         struct node *src = &src_buf->node;
 481         struct node *dst = &dst_buf->node;
 482         int push_items = 0;
 483         int src_nritems;
 484         int dst_nritems;
 485         int ret = 0;
 486         int wret;
 487
 488         src_nritems = src->header.nritems;
 489         dst_nritems = dst->header.nritems;
 490         push_items = NODEPTRS_PER_BLOCK - dst_nritems;
 491         if (push_items <= 0) {
 492                 return 1;
 493         }
 494
 495         if (src_nritems < push_items)
 496                 push_items = src_nritems;
 497
 498         memcpy(dst->keys + dst_nritems, src->keys,
 499                 push_items * sizeof(struct key));
 500         memcpy(dst->blockptrs + dst_nritems, src->blockptrs,
 501                 push_items * sizeof(u64));
 502         if (push_items < src_nritems) {
 503                 memmove(src->keys, src->keys + push_items,
 504                         (src_nritems - push_items) * sizeof(struct key));
 505                 memmove(src->blockptrs, src->blockptrs + push_items,
 506                         (src_nritems - push_items) * sizeof(u64));
 507         }
 508         src->header.nritems -= push_items;
 509         dst->header.nritems += push_items;
 510
 511         wret = write_tree_block(root, src_buf);
 512         if (wret < 0)
 513                 ret = wret;
 514
 515         wret = write_tree_block(root, dst_buf);
 516         if (wret < 0)
 517                 ret = wret;
 518         return ret;
 519 }
 520
 521 /*
 522  * try to push data from one node into the next node right in the
 523  * tree.
 524  *
 525  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
 526  * error, and > 0 if there was no room in the right hand block.
 527  *
 528  * this will  only push up to 1/2 the contents of the left node over
 529  */
 530 static int balance_node_right(struct ctree_root *root,
 531                               struct tree_buffer *dst_buf,
 532                               struct tree_buffer *src_buf)
 533 {
 534         struct node *src = &src_buf->node;
 535         struct node *dst = &dst_buf->node;
 536         int push_items = 0;
 537         int max_push;
 538         int src_nritems;
 539         int dst_nritems;
 540         int ret = 0;
 541         int wret;
 542
 543         src_nritems = src->header.nritems;
 544         dst_nritems = dst->header.nritems;
 545         push_items = NODEPTRS_PER_BLOCK - dst_nritems;
 546         if (push_items <= 0) {
 547                 return 1;
 548         }
 549
 550         max_push = src_nritems / 2 + 1;
 551         /* don't try to empty the node */
 552         if (max_push > src_nritems)
 553                 return 1;
 554         if (max_push < push_items)
 555                 push_items = max_push;
 556
 557         memmove(dst->keys + push_items, dst->keys,
 558                 dst_nritems * sizeof(struct key));
 559         memmove(dst->blockptrs + push_items, dst->blockptrs,
 560                 dst_nritems * sizeof(u64));
 561         memcpy(dst->keys, src->keys + src_nritems - push_items,
 562                 push_items * sizeof(struct key));
 563         memcpy(dst->blockptrs, src->blockptrs + src_nritems - push_items,
 564                 push_items * sizeof(u64));
 565
 566         src->header.nritems -= push_items;
 567         dst->header.nritems += push_items;
 568
 569         wret = write_tree_block(root, src_buf);
 570         if (wret < 0)
 571                 ret = wret;
 572
 573         wret = write_tree_block(root, dst_buf);
 574         if (wret < 0)
 575                 ret = wret;
 576         return ret;
 577 }
 578
 579 /*
 580  * helper function to insert a new root level in the tree.
 581  * A new node is allocated, and a single item is inserted to
 582  * point to the existing root
 583  *
 584  * returns zero on success or < 0 on failure.
 585  */
 586 static int insert_new_root(struct ctree_root *root,
 587                            struct ctree_path *path, int level)
 588 {
 589         struct tree_buffer *t;
 590         struct node *lower;
 591         struct node *c;
 592         struct key *lower_key;
 593
 594         BUG_ON(path->nodes[level]);
 595         BUG_ON(path->nodes[level-1] != root->node);
 596
 597         t = alloc_free_block(root);
 598         c = &t->node;
 599         memset(c, 0, sizeof(c));
 600         c->header.nritems = 1;
 601         c->header.flags = node_level(level);
 602         c->header.blocknr = t->blocknr;
 603         c->header.parentid = root->node->node.header.parentid;
 604         lower = &path->nodes[level-1]->node;
 605         if (is_leaf(lower->header.flags))
 606                 lower_key = &((struct leaf *)lower)->items[0].key;
 607         else
 608                 lower_key = lower->keys;
 609         memcpy(c->keys, lower_key, sizeof(struct key));
 610         c->blockptrs[0] = path->nodes[level-1]->blocknr;
 611         /* the super has an extra ref to root->node */
 612         tree_block_release(root, root->node);
 613         root->node = t;
 614         t->count++;
 615         write_tree_block(root, t);
 616         path->nodes[level] = t;
 617         path->slots[level] = 0;
 618         return 0;
 619 }
 620
 621 /*
 622  * worker function to insert a single pointer in a node.
 623  * the node should have enough room for the pointer already
 624  *
 625  * slot and level indicate where you want the key to go, and
 626  * blocknr is the block the key points to.
 627  *
 628  * returns zero on success and < 0 on any error
 629  */
 630 static int insert_ptr(struct ctree_root *root,
 631                 struct ctree_path *path, struct key *key,
 632                 u64 blocknr, int slot, int level)
 633 {
 634         struct node *lower;
 635         int nritems;
 636
 637         BUG_ON(!path->nodes[level]);
 638         lower = &path->nodes[level]->node;
 639         nritems = lower->header.nritems;
 640         if (slot > nritems)
 641                 BUG();
 642         if (nritems == NODEPTRS_PER_BLOCK)
 643                 BUG();
 644         if (slot != nritems) {
 645                 memmove(lower->keys + slot + 1, lower->keys + slot,
 646                         (nritems - slot) * sizeof(struct key));
 647                 memmove(lower->blockptrs + slot + 1, lower->blockptrs + slot,
 648                         (nritems - slot) * sizeof(u64));
 649         }
 650         memcpy(lower->keys + slot, key, sizeof(struct key));
 651         lower->blockptrs[slot] = blocknr;
 652         lower->header.nritems++;
 653         if (lower->keys[1].objectid == 0)
 654                         BUG();
 655         write_tree_block(root, path->nodes[level]);
 656         return 0;
 657 }
 658
 659 /*
 660  * split the node at the specified level in path in two.
 661  * The path is corrected to point to the appropriate node after the split
 662  *
 663  * Before splitting this tries to make some room in the node by pushing
 664  * left and right, if either one works, it returns right away.
 665  *
 666  * returns 0 on success and < 0 on failure
 667  */
 668 static int split_node(struct ctree_root *root, struct ctree_path *path,
 669                       int level)
 670 {
 671         struct tree_buffer *t;
 672         struct node *c;
 673         struct tree_buffer *split_buffer;
 674         struct node *split;
 675         int mid;
 676         int ret;
 677         int wret;
 678
 679         t = path->nodes[level];
 680         c = &t->node;
 681         if (t == root->node) {
 682                 /* trying to split the root, lets make a new one */
 683                 ret = insert_new_root(root, path, level + 1);
 684                 if (ret)
 685                         return ret;
 686         }
 687         split_buffer = alloc_free_block(root);
 688         split = &split_buffer->node;
 689         split->header.flags = c->header.flags;
 690         split->header.blocknr = split_buffer->blocknr;
 691         split->header.parentid = root->node->node.header.parentid;
 692         mid = (c->header.nritems + 1) / 2;
 693         memcpy(split->keys, c->keys + mid,
 694                 (c->header.nritems - mid) * sizeof(struct key));
 695         memcpy(split->blockptrs, c->blockptrs + mid,
 696                 (c->header.nritems - mid) * sizeof(u64));
 697         split->header.nritems = c->header.nritems - mid;
 698         c->header.nritems = mid;
 699         ret = 0;
 700
 701         wret = write_tree_block(root, t);
 702         if (wret)
 703                 ret = wret;
 704         wret = write_tree_block(root, split_buffer);
 705         if (wret)
 706                 ret = wret;
 707         wret = insert_ptr(root, path, split->keys, split_buffer->blocknr,
 708                           path->slots[level + 1] + 1, level + 1);
 709         if (wret)
 710                 ret = wret;
 711
 712         if (path->slots[level] >= mid) {
 713                 path->slots[level] -= mid;
 714                 tree_block_release(root, t);
 715                 path->nodes[level] = split_buffer;
 716                 path->slots[level + 1] += 1;
 717         } else {
 718                 tree_block_release(root, split_buffer);
 719         }
 720         return ret;
 721 }
 722
 723 /*
 724  * how many bytes are required to store the items in a leaf.  start
 725  * and nr indicate which items in the leaf to check.  This totals up the
 726  * space used both by the item structs and the item data
 727  */
 728 static int leaf_space_used(struct leaf *l, int start, int nr)
 729 {
 730         int data_len;
 731         int end = start + nr - 1;
 732
 733         if (!nr)
 734                 return 0;
 735         data_len = l->items[start].offset + l->items[start].size;
 736         data_len = data_len - l->items[end].offset;
 737         data_len += sizeof(struct item) * nr;
 738         return data_len;
 739 }
 740
 741 /*
 742  * push some data in the path leaf to the right, trying to free up at
 743  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 744  *
 745  * returns 1 if the push failed because the other node didn't have enough
 746  * room, 0 if everything worked out and < 0 if there were major errors.
 747  */
 748 static int push_leaf_right(struct ctree_root *root, struct ctree_path *path,
 749                            int data_size)
 750 {
 751         struct tree_buffer *left_buf = path->nodes[0];
 752         struct leaf *left = &left_buf->leaf;
 753         struct leaf *right;
 754         struct tree_buffer *right_buf;
 755         struct tree_buffer *upper;
 756         int slot;
 757         int i;
 758         int free_space;
 759         int push_space = 0;
 760         int push_items = 0;
 761         struct item *item;
 762
 763         slot = path->slots[1];
 764         if (!path->nodes[1]) {
 765                 return 1;
 766         }
 767         upper = path->nodes[1];
 768         if (slot >= upper->node.header.nritems - 1) {
 769                 return 1;
 770         }
 771         right_buf = read_tree_block(root, upper->node.blockptrs[slot + 1]);
 772         right = &right_buf->leaf;
 773         free_space = leaf_free_space(right);
 774         if (free_space < data_size + sizeof(struct item)) {
 775                 tree_block_release(root, right_buf);
 776                 return 1;
 777         }
 778         for (i = left->header.nritems - 1; i >= 0; i--) {
 779                 item = left->items + i;
 780                 if (path->slots[0] == i)
 781                         push_space += data_size + sizeof(*item);
 782                 if (item->size + sizeof(*item) + push_space > free_space)
 783                         break;
 784                 push_items++;
 785                 push_space += item->size + sizeof(*item);
 786         }
 787         if (push_items == 0) {
 788                 tree_block_release(root, right_buf);
 789                 return 1;
 790         }
 791         /* push left to right */
 792         push_space = left->items[left->header.nritems - push_items].offset +
 793                      left->items[left->header.nritems - push_items].size;
 794         push_space -= leaf_data_end(left);
 795         /* make room in the right data area */
 796         memmove(right->data + leaf_data_end(right) - push_space,
 797                 right->data + leaf_data_end(right),
 798                 LEAF_DATA_SIZE - leaf_data_end(right));
 799         /* copy from the left data area */
 800         memcpy(right->data + LEAF_DATA_SIZE - push_space,
 801                 left->data + leaf_data_end(left),
 802                 push_space);
 803         memmove(right->items + push_items, right->items,
 804                 right->header.nritems * sizeof(struct item));
 805         /* copy the items from left to right */
 806         memcpy(right->items, left->items + left->header.nritems - push_items,
 807                 push_items * sizeof(struct item));
 808
 809         /* update the item pointers */
 810         right->header.nritems += push_items;
 811         push_space = LEAF_DATA_SIZE;
 812         for (i = 0; i < right->header.nritems; i++) {
 813                 right->items[i].offset = push_space - right->items[i].size;
 814                 push_space = right->items[i].offset;
 815         }
 816         left->header.nritems -= push_items;
 817
 818         write_tree_block(root, left_buf);
 819         write_tree_block(root, right_buf);
 820         memcpy(upper->node.keys + slot + 1,
 821                 &right->items[0].key, sizeof(struct key));
 822         write_tree_block(root, upper);
 823         /* then fixup the leaf pointer in the path */
 824         if (path->slots[0] >= left->header.nritems) {
 825                 path->slots[0] -= left->header.nritems;
 826                 tree_block_release(root, path->nodes[0]);
 827                 path->nodes[0] = right_buf;
 828                 path->slots[1] += 1;
 829         } else {
 830                 tree_block_release(root, right_buf);
 831         }
 832         return 0;
 833 }
 834 /*
 835  * push some data in the path leaf to the left, trying to free up at
 836  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 837  */
 838 static int push_leaf_left(struct ctree_root *root, struct ctree_path *path,
 839                           int data_size)
 840 {
 841         struct tree_buffer *right_buf = path->nodes[0];
 842         struct leaf *right = &right_buf->leaf;
 843         struct tree_buffer *t;
 844         struct leaf *left;
 845         int slot;
 846         int i;
 847         int free_space;
 848         int push_space = 0;
 849         int push_items = 0;
 850         struct item *item;
 851         int old_left_nritems;
 852         int ret = 0;
 853         int wret;
 854
 855         slot = path->slots[1];
 856         if (slot == 0) {
 857                 return 1;
 858         }
 859         if (!path->nodes[1]) {
 860                 return 1;
 861         }
 862         t = read_tree_block(root, path->nodes[1]->node.blockptrs[slot - 1]);
 863         left = &t->leaf;
 864         free_space = leaf_free_space(left);
 865         if (free_space < data_size + sizeof(struct item)) {
 866                 tree_block_release(root, t);
 867                 return 1;
 868         }
 869         for (i = 0; i < right->header.nritems; i++) {
 870                 item = right->items + i;
 871                 if (path->slots[0] == i)
 872                         push_space += data_size + sizeof(*item);
 873                 if (item->size + sizeof(*item) + push_space > free_space)
 874                         break;
 875                 push_items++;
 876                 push_space += item->size + sizeof(*item);
 877         }
 878         if (push_items == 0) {
 879                 tree_block_release(root, t);
 880                 return 1;
 881         }
 882         /* push data from right to left */
 883         memcpy(left->items + left->header.nritems,
 884                 right->items, push_items * sizeof(struct item));
 885         push_space = LEAF_DATA_SIZE - right->items[push_items -1].offset;
 886         memcpy(left->data + leaf_data_end(left) - push_space,
 887                 right->data + right->items[push_items - 1].offset,
 888                 push_space);
 889         old_left_nritems = left->header.nritems;
 890         BUG_ON(old_left_nritems < 0);
 891
 892         for(i = old_left_nritems; i < old_left_nritems + push_items; i++) {
 893                 left->items[i].offset -= LEAF_DATA_SIZE -
 894                         left->items[old_left_nritems -1].offset;
 895         }
 896         left->header.nritems += push_items;
 897
 898         /* fixup right node */
 899         push_space = right->items[push_items-1].offset - leaf_data_end(right);
 900         memmove(right->data + LEAF_DATA_SIZE - push_space, right->data +
 901                 leaf_data_end(right), push_space);
 902         memmove(right->items, right->items + push_items,
 903                 (right->header.nritems - push_items) * sizeof(struct item));
 904         right->header.nritems -= push_items;
 905         push_space = LEAF_DATA_SIZE;
 906
 907         for (i = 0; i < right->header.nritems; i++) {
 908                 right->items[i].offset = push_space - right->items[i].size;
 909                 push_space = right->items[i].offset;
 910         }
 911
 912         wret = write_tree_block(root, t);
 913         if (wret)
 914                 ret = wret;
 915         wret = write_tree_block(root, right_buf);
 916         if (wret)
 917                 ret = wret;
 918
 919         wret = fixup_low_keys(root, path, &right->items[0].key, 1);
 920         if (wret)
 921                 ret = wret;
 922
 923         /* then fixup the leaf pointer in the path */
 924         if (path->slots[0] < push_items) {
 925                 path->slots[0] += old_left_nritems;
 926                 tree_block_release(root, path->nodes[0]);
 927                 path->nodes[0] = t;
 928                 path->slots[1] -= 1;
 929         } else {
 930                 tree_block_release(root, t);
 931                 path->slots[0] -= push_items;
 932         }
 933         BUG_ON(path->slots[0] < 0);
 934         return ret;
 935 }
 936
 937 /*
 938  * split the path's leaf in two, making sure there is at least data_size
 939  * available for the resulting leaf level of the path.
 940  *
 941  * returns 0 if all went well and < 0 on failure.
 942  */
 943 static int split_leaf(struct ctree_root *root, struct ctree_path *path,
 944                       int data_size)
 945 {
 946         struct tree_buffer *l_buf;
 947         struct leaf *l;
 948         int nritems;
 949         int mid;
 950         int slot;
 951         struct leaf *right;
 952         struct tree_buffer *right_buffer;
 953         int space_needed = data_size + sizeof(struct item);
 954         int data_copy_size;
 955         int rt_data_off;
 956         int i;
 957         int ret;
 958         int wret;
 959
 960         wret = push_leaf_left(root, path, data_size);
 961         if (wret < 0)
 962                 return wret;
 963         if (wret) {
 964                 wret = push_leaf_right(root, path, data_size);
 965                 if (wret < 0)
 966                         return wret;
 967         }
 968         l_buf = path->nodes[0];
 969         l = &l_buf->leaf;
 970
 971         /* did the pushes work? */
 972         if (leaf_free_space(l) >= sizeof(struct item) + data_size)
 973                 return 0;
 974
 975         if (!path->nodes[1]) {
 976                 ret = insert_new_root(root, path, 1);
 977                 if (ret)
 978                         return ret;
 979         }
 980         slot = path->slots[0];
 981         nritems = l->header.nritems;
 982         mid = (nritems + 1)/ 2;
 983
 984         right_buffer = alloc_free_block(root);
 985         BUG_ON(!right_buffer);
 986         BUG_ON(mid == nritems);
 987         right = &right_buffer->leaf;
 988         memset(right, 0, sizeof(*right));
 989         if (mid <= slot) {
 990                 /* FIXME, just alloc a new leaf here */
 991                 if (leaf_space_used(l, mid, nritems - mid) + space_needed >
 992                         LEAF_DATA_SIZE)
 993                         BUG();
 994         } else {
 995                 /* FIXME, just alloc a new leaf here */
 996                 if (leaf_space_used(l, 0, mid + 1) + space_needed >
 997                         LEAF_DATA_SIZE)
 998                         BUG();
 999         }
1000         right->header.nritems = nritems - mid;
1001         right->header.blocknr = right_buffer->blocknr;
1002         right->header.flags = node_level(0);
1003         right->header.parentid = root->node->node.header.parentid;
1004         data_copy_size = l->items[mid].offset + l->items[mid].size -
1005                          leaf_data_end(l);
1006         memcpy(right->items, l->items + mid,
1007                (nritems - mid) * sizeof(struct item));
1008         memcpy(right->data + LEAF_DATA_SIZE - data_copy_size,
1009                l->data + leaf_data_end(l), data_copy_size);
1010         rt_data_off = LEAF_DATA_SIZE -
1011                      (l->items[mid].offset + l->items[mid].size);
1012
1013         for (i = 0; i < right->header.nritems; i++)
1014                 right->items[i].offset += rt_data_off;
1015
1016         l->header.nritems = mid;
1017         ret = 0;
1018         wret = insert_ptr(root, path, &right->items[0].key,
1019                           right_buffer->blocknr, path->slots[1] + 1, 1);
1020         if (wret)
1021                 ret = wret;
1022         wret = write_tree_block(root, right_buffer);
1023         if (wret)
1024                 ret = wret;
1025         wret = write_tree_block(root, l_buf);
1026         if (wret)
1027                 ret = wret;
1028
1029         BUG_ON(path->slots[0] != slot);
1030         if (mid <= slot) {
1031                 tree_block_release(root, path->nodes[0]);
1032                 path->nodes[0] = right_buffer;
1033                 path->slots[0] -= mid;
1034                 path->slots[1] += 1;
1035         } else
1036                 tree_block_release(root, right_buffer);
1037         BUG_ON(path->slots[0] < 0);
1038         return ret;
1039 }
1040
1041 /*
1042  * Given a key and some data, insert an item into the tree.
1043  * This does all the path init required, making room in the tree if needed.
1044  */
1045 int insert_item(struct ctree_root *root, struct key *key,
1046                           void *data, int data_size)
1047 {
1048         int ret = 0;
1049         int wret;
1050         int slot;
1051         int slot_orig;
1052         struct leaf *leaf;
1053         struct tree_buffer *leaf_buf;
1054         unsigned int nritems;
1055         unsigned int data_end;
1056         struct ctree_path path;
1057
1058         /* create a root if there isn't one */
1059         if (!root->node)
1060                 BUG();
1061         init_path(&path);
1062         ret = search_slot(root, key, &path, data_size);
1063         if (ret == 0) {
1064                 release_path(root, &path);
1065                 return -EEXIST;
1066         }
1067         if (ret < 0) {
1068                 release_path(root, &path);
1069                 return ret;
1070         }
1071
1072         slot_orig = path.slots[0];
1073         leaf_buf = path.nodes[0];
1074         leaf = &leaf_buf->leaf;
1075
1076         nritems = leaf->header.nritems;
1077         data_end = leaf_data_end(leaf);
1078
1079         if (leaf_free_space(leaf) <  sizeof(struct item) + data_size)
1080                 BUG();
1081
1082         slot = path.slots[0];
1083         BUG_ON(slot < 0);
1084         if (slot != nritems) {
1085                 int i;
1086                 unsigned int old_data = leaf->items[slot].offset +
1087                                         leaf->items[slot].size;
1088
1089                 /*
1090                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
1091                  */
1092                 /* first correct the data pointers */
1093                 for (i = slot; i < nritems; i++)
1094                         leaf->items[i].offset -= data_size;
1095
1096                 /* shift the items */
1097                 memmove(leaf->items + slot + 1, leaf->items + slot,
1098                         (nritems - slot) * sizeof(struct item));
1099
1100                 /* shift the data */
1101                 memmove(leaf->data + data_end - data_size, leaf->data +
1102                         data_end, old_data - data_end);
1103                 data_end = old_data;
1104         }
1105         /* copy the new data in */
1106         memcpy(&leaf->items[slot].key, key, sizeof(struct key));
1107         leaf->items[slot].offset = data_end - data_size;
1108         leaf->items[slot].size = data_size;
1109         memcpy(leaf->data + data_end - data_size, data, data_size);
1110         leaf->header.nritems += 1;
1111
1112         ret = 0;
1113         if (slot == 0)
1114                 ret = fixup_low_keys(root, &path, key, 1);
1115
1116         wret = write_tree_block(root, leaf_buf);
1117         if (wret)
1118                 ret = wret;
1119
1120         if (leaf_free_space(leaf) < 0)
1121                 BUG();
1122         check_leaf(&path, 0);
1123         release_path(root, &path);
1124         return ret;
1125 }
1126
1127 /*
1128  * delete the pointer from a given node.
1129  *
1130  * If the delete empties a node, the node is removed from the tree,
1131  * continuing all the way the root if required.  The root is converted into
1132  * a leaf if all the nodes are emptied.
1133  */
1134 static int del_ptr(struct ctree_root *root, struct ctree_path *path, int level,
1135                    int slot)
1136 {
1137         struct node *node;
1138         struct tree_buffer *parent = path->nodes[level];
1139         int nritems;
1140         int ret = 0;
1141         int wret;
1142
1143         node = &parent->node;
1144         nritems = node->header.nritems;
1145
1146         if (slot != nritems -1) {
1147                 memmove(node->keys + slot, node->keys + slot + 1,
1148                         sizeof(struct key) * (nritems - slot - 1));
1149                 memmove(node->blockptrs + slot,
1150                         node->blockptrs + slot + 1,
1151                         sizeof(u64) * (nritems - slot - 1));
1152         }
1153         node->header.nritems--;
1154         if (node->header.nritems == 0 && parent == root->node) {
1155                 BUG_ON(node_level(root->node->node.header.flags) != 1);
1156                 /* just turn the root into a leaf and break */
1157                 root->node->node.header.flags = node_level(0);
1158         } else if (slot == 0) {
1159                 wret = fixup_low_keys(root, path, node->keys, level + 1);
1160                 if (wret)
1161                         ret = wret;
1162         }
1163         wret = write_tree_block(root, parent);
1164         if (wret)
1165                 ret = wret;
1166         return ret;
1167 }
1168
1169 /*
1170  * delete the item at the leaf level in path.  If that empties
1171  * the leaf, remove it from the tree
1172  */
1173 int del_item(struct ctree_root *root, struct ctree_path *path)
1174 {
1175         int slot;
1176         struct leaf *leaf;
1177         struct tree_buffer *leaf_buf;
1178         int doff;
1179         int dsize;
1180         int ret = 0;
1181         int wret;
1182
1183         leaf_buf = path->nodes[0];
1184         leaf = &leaf_buf->leaf;
1185         slot = path->slots[0];
1186         doff = leaf->items[slot].offset;
1187         dsize = leaf->items[slot].size;
1188
1189         if (slot != leaf->header.nritems - 1) {
1190                 int i;
1191                 int data_end = leaf_data_end(leaf);
1192                 memmove(leaf->data + data_end + dsize,
1193                         leaf->data + data_end,
1194                         doff - data_end);
1195                 for (i = slot + 1; i < leaf->header.nritems; i++)
1196                         leaf->items[i].offset += dsize;
1197                 memmove(leaf->items + slot, leaf->items + slot + 1,
1198                         sizeof(struct item) *
1199                         (leaf->header.nritems - slot - 1));
1200         }
1201         leaf->header.nritems -= 1;
1202         /* delete the leaf if we've emptied it */
1203         if (leaf->header.nritems == 0) {
1204                 if (leaf_buf == root->node) {
1205                         leaf->header.flags = node_level(0);
1206                         write_tree_block(root, leaf_buf);
1207                 } else {
1208                         wret = del_ptr(root, path, 1, path->slots[1]);
1209                         if (wret)
1210                                 ret = wret;
1211                         wret = free_extent(root, leaf_buf->blocknr, 1);
1212                         if (wret)
1213                                 ret = wret;
1214                 }
1215         } else {
1216                 int used = leaf_space_used(leaf, 0, leaf->header.nritems);
1217                 if (slot == 0) {
1218                         wret = fixup_low_keys(root, path,
1219                                                    &leaf->items[0].key, 1);
1220                         if (wret)
1221                                 ret = wret;
1222                 }
1223                 wret = write_tree_block(root, leaf_buf);
1224                 if (wret)
1225                         ret = wret;
1226
1227                 /* delete the leaf if it is mostly empty */
1228                 if (used < LEAF_DATA_SIZE / 3) {
1229                         /* push_leaf_left fixes the path.
1230                          * make sure the path still points to our leaf
1231                          * for possible call to del_ptr below
1232                          */
1233                         slot = path->slots[1];
1234                         leaf_buf->count++;
1235                         wret = push_leaf_left(root, path, 1);
1236                         if (wret < 0)
1237                                 ret = wret;
1238                         if (leaf->header.nritems) {
1239                                 wret = push_leaf_right(root, path, 1);
1240                                 if (wret < 0)
1241                                         ret = wret;
1242                         }
1243                         if (leaf->header.nritems == 0) {
1244                                 u64 blocknr = leaf_buf->blocknr;
1245                                 wret = del_ptr(root, path, 1, slot);
1246                                 if (wret)
1247                                         ret = wret;
1248                                 tree_block_release(root, leaf_buf);
1249                                 wret = free_extent(root, blocknr, 1);
1250                                 if (wret)
1251                                         ret = wret;
1252                         } else {
1253                                 tree_block_release(root, leaf_buf);
1254                         }
1255                 }
1256         }
1257         return ret;
1258 }
1259
1260 /*
1261  * walk up the tree as far as required to find the next leaf.
1262  * returns 0 if it found something or 1 if there are no greater leaves.
1263  * returns < 0 on io errors.
1264  */
1265 int next_leaf(struct ctree_root *root, struct ctree_path *path)
1266 {
1267         int slot;
1268         int level = 1;
1269         u64 blocknr;
1270         struct tree_buffer *c;
1271         struct tree_buffer *next = NULL;
1272
1273         while(level < MAX_LEVEL) {
1274                 if (!path->nodes[level])
1275                         return 1;
1276                 slot = path->slots[level] + 1;
1277                 c = path->nodes[level];
1278                 if (slot >= c->node.header.nritems) {
1279                         level++;
1280                         continue;
1281                 }
1282                 blocknr = c->node.blockptrs[slot];
1283                 if (next)
1284                         tree_block_release(root, next);
1285                 next = read_tree_block(root, blocknr);
1286                 break;
1287         }
1288         path->slots[level] = slot;
1289         while(1) {
1290                 level--;
1291                 c = path->nodes[level];
1292                 tree_block_release(root, c);
1293                 path->nodes[level] = next;
1294                 path->slots[level] = 0;
1295                 if (!level)
1296                         break;
1297                 next = read_tree_block(root, next->node.blockptrs[0]);
1298         }
1299         return 0;
1300 }
1301