fs/btrfs/ctree.c

   1 #include <linux/module.h>
   2 #include "ctree.h"
   3 #include "disk-io.h"
   4 #include "transaction.h"
   5
   6 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
   7                       *root, struct btrfs_path *path, int level);
   8 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
   9                       *root, struct btrfs_key *ins_key,
  10                       struct btrfs_path *path, int data_size);
  11 static int push_node_left(struct btrfs_trans_handle *trans, struct btrfs_root
  12                           *root, struct buffer_head *dst, struct buffer_head
  13                           *src);
  14 static int balance_node_right(struct btrfs_trans_handle *trans, struct
  15                               btrfs_root *root, struct buffer_head *dst_buf,
  16                               struct buffer_head *src_buf);
  17 static int del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  18                    struct btrfs_path *path, int level, int slot);
  19
  20 inline void btrfs_init_path(struct btrfs_path *p)
  21 {
  22         memset(p, 0, sizeof(*p));
  23 }
  24
  25 struct btrfs_path *btrfs_alloc_path(void)
  26 {
  27         struct btrfs_path *path;
  28         path = kmem_cache_alloc(btrfs_path_cachep, GFP_NOFS);
  29         if (path)
  30                 btrfs_init_path(path);
  31         return path;
  32 }
  33
  34 void btrfs_free_path(struct btrfs_path *p)
  35 {
  36         btrfs_release_path(NULL, p);
  37         kmem_cache_free(btrfs_path_cachep, p);
  38 }
  39
  40 void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
  41 {
  42         int i;
  43         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
  44                 if (!p->nodes[i])
  45                         break;
  46                 btrfs_block_release(root, p->nodes[i]);
  47         }
  48         memset(p, 0, sizeof(*p));
  49 }
  50
  51 static int btrfs_cow_block(struct btrfs_trans_handle *trans, struct btrfs_root
  52                            *root, struct buffer_head *buf, struct buffer_head
  53                            *parent, int parent_slot, struct buffer_head
  54                            **cow_ret)
  55 {
  56         struct buffer_head *cow;
  57         struct btrfs_node *cow_node;
  58
  59         if (btrfs_header_generation(btrfs_buffer_header(buf)) ==
  60                                     trans->transid) {
  61                 *cow_ret = buf;
  62                 return 0;
  63         }
  64         cow = btrfs_alloc_free_block(trans, root, buf->b_blocknr);
  65         cow_node = btrfs_buffer_node(cow);
  66         if (buf->b_size != root->blocksize || cow->b_size != root->blocksize)
  67                 WARN_ON(1);
  68         memcpy(cow_node, btrfs_buffer_node(buf), root->blocksize);
  69         btrfs_set_header_blocknr(&cow_node->header, bh_blocknr(cow));
  70         btrfs_set_header_generation(&cow_node->header, trans->transid);
  71         btrfs_set_header_owner(&cow_node->header, root->root_key.objectid);
  72         btrfs_inc_ref(trans, root, buf);
  73         if (buf == root->node) {
  74                 root->node = cow;
  75                 get_bh(cow);
  76                 if (buf != root->commit_root) {
  77                         btrfs_free_extent(trans, root, bh_blocknr(buf), 1, 1);
  78                 }
  79                 btrfs_block_release(root, buf);
  80         } else {
  81                 btrfs_set_node_blockptr(btrfs_buffer_node(parent), parent_slot,
  82                                         bh_blocknr(cow));
  83                 btrfs_mark_buffer_dirty(parent);
  84                 btrfs_free_extent(trans, root, bh_blocknr(buf), 1, 1);
  85         }
  86         btrfs_block_release(root, buf);
  87         mark_buffer_dirty(cow);
  88         *cow_ret = cow;
  89         return 0;
  90 }
  91
  92 /*
  93  * The leaf data grows from end-to-front in the node.
  94  * this returns the address of the start of the last item,
  95  * which is the stop of the leaf data stack
  96  */
  97 static inline unsigned int leaf_data_end(struct btrfs_root *root,
  98                                          struct btrfs_leaf *leaf)
  99 {
 100         u32 nr = btrfs_header_nritems(&leaf->header);
 101         if (nr == 0)
 102                 return BTRFS_LEAF_DATA_SIZE(root);
 103         return btrfs_item_offset(leaf->items + nr - 1);
 104 }
 105
 106 /*
 107  * compare two keys in a memcmp fashion
 108  */
 109 static int comp_keys(struct btrfs_disk_key *disk, struct btrfs_key *k2)
 110 {
 111         struct btrfs_key k1;
 112
 113         btrfs_disk_key_to_cpu(&k1, disk);
 114
 115         if (k1.objectid > k2->objectid)
 116                 return 1;
 117         if (k1.objectid < k2->objectid)
 118                 return -1;
 119         if (k1.flags > k2->flags)
 120                 return 1;
 121         if (k1.flags < k2->flags)
 122                 return -1;
 123         if (k1.offset > k2->offset)
 124                 return 1;
 125         if (k1.offset < k2->offset)
 126                 return -1;
 127         return 0;
 128 }
 129
 130 static int check_node(struct btrfs_root *root, struct btrfs_path *path,
 131                       int level)
 132 {
 133         struct btrfs_node *parent = NULL;
 134         struct btrfs_node *node = btrfs_buffer_node(path->nodes[level]);
 135         int parent_slot;
 136         int slot;
 137         struct btrfs_key cpukey;
 138         u32 nritems = btrfs_header_nritems(&node->header);
 139
 140         if (path->nodes[level + 1])
 141                 parent = btrfs_buffer_node(path->nodes[level + 1]);
 142         parent_slot = path->slots[level + 1];
 143         slot = path->slots[level];
 144         BUG_ON(nritems == 0);
 145         if (parent) {
 146                 struct btrfs_disk_key *parent_key;
 147                 parent_key = &parent->ptrs[parent_slot].key;
 148                 BUG_ON(memcmp(parent_key, &node->ptrs[0].key,
 149                               sizeof(struct btrfs_disk_key)));
 150                 BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
 151                        btrfs_header_blocknr(&node->header));
 152         }
 153         BUG_ON(nritems > BTRFS_NODEPTRS_PER_BLOCK(root));
 154         if (slot != 0) {
 155                 btrfs_disk_key_to_cpu(&cpukey, &node->ptrs[slot - 1].key);
 156                 BUG_ON(comp_keys(&node->ptrs[slot].key, &cpukey) <= 0);
 157         }
 158         if (slot < nritems - 1) {
 159                 btrfs_disk_key_to_cpu(&cpukey, &node->ptrs[slot + 1].key);
 160                 BUG_ON(comp_keys(&node->ptrs[slot].key, &cpukey) >= 0);
 161         }
 162         return 0;
 163 }
 164
 165 static int check_leaf(struct btrfs_root *root, struct btrfs_path *path,
 166                       int level)
 167 {
 168         struct btrfs_leaf *leaf = btrfs_buffer_leaf(path->nodes[level]);
 169         struct btrfs_node *parent = NULL;
 170         int parent_slot;
 171         int slot = path->slots[0];
 172         struct btrfs_key cpukey;
 173
 174         u32 nritems = btrfs_header_nritems(&leaf->header);
 175
 176         if (path->nodes[level + 1])
 177                 parent = btrfs_buffer_node(path->nodes[level + 1]);
 178         parent_slot = path->slots[level + 1];
 179         BUG_ON(btrfs_leaf_free_space(root, leaf) < 0);
 180
 181         if (nritems == 0)
 182                 return 0;
 183
 184         if (parent) {
 185                 struct btrfs_disk_key *parent_key;
 186                 parent_key = &parent->ptrs[parent_slot].key;
 187                 BUG_ON(memcmp(parent_key, &leaf->items[0].key,
 188                        sizeof(struct btrfs_disk_key)));
 189                 BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
 190                        btrfs_header_blocknr(&leaf->header));
 191         }
 192         if (slot != 0) {
 193                 btrfs_disk_key_to_cpu(&cpukey, &leaf->items[slot - 1].key);
 194                 BUG_ON(comp_keys(&leaf->items[slot].key, &cpukey) <= 0);
 195                 BUG_ON(btrfs_item_offset(leaf->items + slot - 1) !=
 196                         btrfs_item_end(leaf->items + slot));
 197         }
 198         if (slot < nritems - 1) {
 199                 btrfs_disk_key_to_cpu(&cpukey, &leaf->items[slot + 1].key);
 200                 BUG_ON(comp_keys(&leaf->items[slot].key, &cpukey) >= 0);
 201                 BUG_ON(btrfs_item_offset(leaf->items + slot) !=
 202                         btrfs_item_end(leaf->items + slot + 1));
 203         }
 204         BUG_ON(btrfs_item_offset(leaf->items) +
 205                btrfs_item_size(leaf->items) != BTRFS_LEAF_DATA_SIZE(root));
 206         return 0;
 207 }
 208
 209 static int check_block(struct btrfs_root *root, struct btrfs_path *path,
 210                         int level)
 211 {
 212         struct btrfs_node *node = btrfs_buffer_node(path->nodes[level]);
 213         if (memcmp(node->header.fsid, root->fs_info->disk_super->fsid,
 214                    sizeof(node->header.fsid)))
 215                 BUG();
 216         if (level == 0)
 217                 return check_leaf(root, path, level);
 218         return check_node(root, path, level);
 219 }
 220
 221 /*
 222  * search for key in the array p.  items p are item_size apart
 223  * and there are 'max' items in p
 224  * the slot in the array is returned via slot, and it points to
 225  * the place where you would insert key if it is not found in
 226  * the array.
 227  *
 228  * slot may point to max if the key is bigger than all of the keys
 229  */
 230 static int generic_bin_search(char *p, int item_size, struct btrfs_key *key,
 231                        int max, int *slot)
 232 {
 233         int low = 0;
 234         int high = max;
 235         int mid;
 236         int ret;
 237         struct btrfs_disk_key *tmp;
 238
 239         while(low < high) {
 240                 mid = (low + high) / 2;
 241                 tmp = (struct btrfs_disk_key *)(p + mid * item_size);
 242                 ret = comp_keys(tmp, key);
 243
 244                 if (ret < 0)
 245                         low = mid + 1;
 246                 else if (ret > 0)
 247                         high = mid;
 248                 else {
 249                         *slot = mid;
 250                         return 0;
 251                 }
 252         }
 253         *slot = low;
 254         return 1;
 255 }
 256
 257 /*
 258  * simple bin_search frontend that does the right thing for
 259  * leaves vs nodes
 260  */
 261 static int bin_search(struct btrfs_node *c, struct btrfs_key *key, int *slot)
 262 {
 263         if (btrfs_is_leaf(c)) {
 264                 struct btrfs_leaf *l = (struct btrfs_leaf *)c;
 265                 return generic_bin_search((void *)l->items,
 266                                           sizeof(struct btrfs_item),
 267                                           key, btrfs_header_nritems(&c->header),
 268                                           slot);
 269         } else {
 270                 return generic_bin_search((void *)c->ptrs,
 271                                           sizeof(struct btrfs_key_ptr),
 272                                           key, btrfs_header_nritems(&c->header),
 273                                           slot);
 274         }
 275         return -1;
 276 }
 277
 278 static struct buffer_head *read_node_slot(struct btrfs_root *root,
 279                                    struct buffer_head *parent_buf,
 280                                    int slot)
 281 {
 282         struct btrfs_node *node = btrfs_buffer_node(parent_buf);
 283         if (slot < 0)
 284                 return NULL;
 285         if (slot >= btrfs_header_nritems(&node->header))
 286                 return NULL;
 287         return read_tree_block(root, btrfs_node_blockptr(node, slot));
 288 }
 289
 290 static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
 291                          *root, struct btrfs_path *path, int level)
 292 {
 293         struct buffer_head *right_buf;
 294         struct buffer_head *mid_buf;
 295         struct buffer_head *left_buf;
 296         struct buffer_head *parent_buf = NULL;
 297         struct btrfs_node *right = NULL;
 298         struct btrfs_node *mid;
 299         struct btrfs_node *left = NULL;
 300         struct btrfs_node *parent = NULL;
 301         int ret = 0;
 302         int wret;
 303         int pslot;
 304         int orig_slot = path->slots[level];
 305         u64 orig_ptr;
 306
 307         if (level == 0)
 308                 return 0;
 309
 310         mid_buf = path->nodes[level];
 311         mid = btrfs_buffer_node(mid_buf);
 312         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 313
 314         if (level < BTRFS_MAX_LEVEL - 1)
 315                 parent_buf = path->nodes[level + 1];
 316         pslot = path->slots[level + 1];
 317
 318         /*
 319          * deal with the case where there is only one pointer in the root
 320          * by promoting the node below to a root
 321          */
 322         if (!parent_buf) {
 323                 struct buffer_head *child;
 324                 u64 blocknr = bh_blocknr(mid_buf);
 325
 326                 if (btrfs_header_nritems(&mid->header) != 1)
 327                         return 0;
 328
 329                 /* promote the child to a root */
 330                 child = read_node_slot(root, mid_buf, 0);
 331                 BUG_ON(!child);
 332                 root->node = child;
 333                 path->nodes[level] = NULL;
 334                 clean_tree_block(trans, root, mid_buf);
 335                 wait_on_buffer(mid_buf);
 336                 /* once for the path */
 337                 btrfs_block_release(root, mid_buf);
 338                 /* once for the root ptr */
 339                 btrfs_block_release(root, mid_buf);
 340                 return btrfs_free_extent(trans, root, blocknr, 1, 1);
 341         }
 342         parent = btrfs_buffer_node(parent_buf);
 343
 344         if (btrfs_header_nritems(&mid->header) >
 345             BTRFS_NODEPTRS_PER_BLOCK(root) / 4)
 346                 return 0;
 347
 348         left_buf = read_node_slot(root, parent_buf, pslot - 1);
 349         right_buf = read_node_slot(root, parent_buf, pslot + 1);
 350
 351         /* first, try to make some room in the middle buffer */
 352         if (left_buf) {
 353                 btrfs_cow_block(trans, root, left_buf, parent_buf, pslot - 1,
 354                                 &left_buf);
 355                 left = btrfs_buffer_node(left_buf);
 356                 orig_slot += btrfs_header_nritems(&left->header);
 357                 wret = push_node_left(trans, root, left_buf, mid_buf);
 358                 if (wret < 0)
 359                         ret = wret;
 360         }
 361
 362         /*
 363          * then try to empty the right most buffer into the middle
 364          */
 365         if (right_buf) {
 366                 btrfs_cow_block(trans, root, right_buf, parent_buf, pslot + 1,
 367                                 &right_buf);
 368                 right = btrfs_buffer_node(right_buf);
 369                 wret = push_node_left(trans, root, mid_buf, right_buf);
 370                 if (wret < 0)
 371                         ret = wret;
 372                 if (btrfs_header_nritems(&right->header) == 0) {
 373                         u64 blocknr = bh_blocknr(right_buf);
 374                         clean_tree_block(trans, root, right_buf);
 375                         wait_on_buffer(right_buf);
 376                         btrfs_block_release(root, right_buf);
 377                         right_buf = NULL;
 378                         right = NULL;
 379                         wret = del_ptr(trans, root, path, level + 1, pslot +
 380                                        1);
 381                         if (wret)
 382                                 ret = wret;
 383                         wret = btrfs_free_extent(trans, root, blocknr, 1, 1);
 384                         if (wret)
 385                                 ret = wret;
 386                 } else {
 387                         btrfs_memcpy(root, parent,
 388                                      &parent->ptrs[pslot + 1].key,
 389                                      &right->ptrs[0].key,
 390                                      sizeof(struct btrfs_disk_key));
 391                         btrfs_mark_buffer_dirty(parent_buf);
 392                 }
 393         }
 394         if (btrfs_header_nritems(&mid->header) == 1) {
 395                 /*
 396                  * we're not allowed to leave a node with one item in the
 397                  * tree during a delete.  A deletion from lower in the tree
 398                  * could try to delete the only pointer in this node.
 399                  * So, pull some keys from the left.
 400                  * There has to be a left pointer at this point because
 401                  * otherwise we would have pulled some pointers from the
 402                  * right
 403                  */
 404                 BUG_ON(!left_buf);
 405                 wret = balance_node_right(trans, root, mid_buf, left_buf);
 406                 if (wret < 0)
 407                         ret = wret;
 408                 BUG_ON(wret == 1);
 409         }
 410         if (btrfs_header_nritems(&mid->header) == 0) {
 411                 /* we've managed to empty the middle node, drop it */
 412                 u64 blocknr = bh_blocknr(mid_buf);
 413                 clean_tree_block(trans, root, mid_buf);
 414                 wait_on_buffer(mid_buf);
 415                 btrfs_block_release(root, mid_buf);
 416                 mid_buf = NULL;
 417                 mid = NULL;
 418                 wret = del_ptr(trans, root, path, level + 1, pslot);
 419                 if (wret)
 420                         ret = wret;
 421                 wret = btrfs_free_extent(trans, root, blocknr, 1, 1);
 422                 if (wret)
 423                         ret = wret;
 424         } else {
 425                 /* update the parent key to reflect our changes */
 426                 btrfs_memcpy(root, parent,
 427                              &parent->ptrs[pslot].key, &mid->ptrs[0].key,
 428                              sizeof(struct btrfs_disk_key));
 429                 btrfs_mark_buffer_dirty(parent_buf);
 430         }
 431
 432         /* update the path */
 433         if (left_buf) {
 434                 if (btrfs_header_nritems(&left->header) > orig_slot) {
 435                         get_bh(left_buf);
 436                         path->nodes[level] = left_buf;
 437                         path->slots[level + 1] -= 1;
 438                         path->slots[level] = orig_slot;
 439                         if (mid_buf)
 440                                 btrfs_block_release(root, mid_buf);
 441                 } else {
 442                         orig_slot -= btrfs_header_nritems(&left->header);
 443                         path->slots[level] = orig_slot;
 444                 }
 445         }
 446         /* double check we haven't messed things up */
 447         check_block(root, path, level);
 448         if (orig_ptr !=
 449             btrfs_node_blockptr(btrfs_buffer_node(path->nodes[level]),
 450                                 path->slots[level]))
 451                 BUG();
 452
 453         if (right_buf)
 454                 btrfs_block_release(root, right_buf);
 455         if (left_buf)
 456                 btrfs_block_release(root, left_buf);
 457         return ret;
 458 }
 459
 460 /* returns zero if the push worked, non-zero otherwise */
 461 static int push_nodes_for_insert(struct btrfs_trans_handle *trans,
 462                                 struct btrfs_root *root,
 463                                 struct btrfs_path *path, int level)
 464 {
 465         struct buffer_head *right_buf;
 466         struct buffer_head *mid_buf;
 467         struct buffer_head *left_buf;
 468         struct buffer_head *parent_buf = NULL;
 469         struct btrfs_node *right = NULL;
 470         struct btrfs_node *mid;
 471         struct btrfs_node *left = NULL;
 472         struct btrfs_node *parent = NULL;
 473         int ret = 0;
 474         int wret;
 475         int pslot;
 476         int orig_slot = path->slots[level];
 477         u64 orig_ptr;
 478
 479         if (level == 0)
 480                 return 1;
 481
 482         mid_buf = path->nodes[level];
 483         mid = btrfs_buffer_node(mid_buf);
 484         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 485
 486         if (level < BTRFS_MAX_LEVEL - 1)
 487                 parent_buf = path->nodes[level + 1];
 488         pslot = path->slots[level + 1];
 489
 490         if (!parent_buf)
 491                 return 1;
 492         parent = btrfs_buffer_node(parent_buf);
 493
 494         left_buf = read_node_slot(root, parent_buf, pslot - 1);
 495
 496         /* first, try to make some room in the middle buffer */
 497         if (left_buf) {
 498                 u32 left_nr;
 499                 left = btrfs_buffer_node(left_buf);
 500                 left_nr = btrfs_header_nritems(&left->header);
 501                 if (left_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
 502                         wret = 1;
 503                 } else {
 504                         btrfs_cow_block(trans, root, left_buf, parent_buf,
 505                                         pslot - 1, &left_buf);
 506                         left = btrfs_buffer_node(left_buf);
 507                         wret = push_node_left(trans, root, left_buf, mid_buf);
 508                 }
 509                 if (wret < 0)
 510                         ret = wret;
 511                 if (wret == 0) {
 512                         orig_slot += left_nr;
 513                         btrfs_memcpy(root, parent,
 514                                      &parent->ptrs[pslot].key,
 515                                      &mid->ptrs[0].key,
 516                                      sizeof(struct btrfs_disk_key));
 517                         btrfs_mark_buffer_dirty(parent_buf);
 518                         if (btrfs_header_nritems(&left->header) > orig_slot) {
 519                                 path->nodes[level] = left_buf;
 520                                 path->slots[level + 1] -= 1;
 521                                 path->slots[level] = orig_slot;
 522                                 btrfs_block_release(root, mid_buf);
 523                         } else {
 524                                 orig_slot -=
 525                                         btrfs_header_nritems(&left->header);
 526                                 path->slots[level] = orig_slot;
 527                                 btrfs_block_release(root, left_buf);
 528                         }
 529                         check_node(root, path, level);
 530                         return 0;
 531                 }
 532                 btrfs_block_release(root, left_buf);
 533         }
 534         right_buf = read_node_slot(root, parent_buf, pslot + 1);
 535
 536         /*
 537          * then try to empty the right most buffer into the middle
 538          */
 539         if (right_buf) {
 540                 u32 right_nr;
 541                 right = btrfs_buffer_node(right_buf);
 542                 right_nr = btrfs_header_nritems(&right->header);
 543                 if (right_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
 544                         wret = 1;
 545                 } else {
 546                         btrfs_cow_block(trans, root, right_buf,
 547                                         parent_buf, pslot + 1, &right_buf);
 548                         right = btrfs_buffer_node(right_buf);
 549                         wret = balance_node_right(trans, root,
 550                                                   right_buf, mid_buf);
 551                 }
 552                 if (wret < 0)
 553                         ret = wret;
 554                 if (wret == 0) {
 555                         btrfs_memcpy(root, parent,
 556                                      &parent->ptrs[pslot + 1].key,
 557                                      &right->ptrs[0].key,
 558                                      sizeof(struct btrfs_disk_key));
 559                         btrfs_mark_buffer_dirty(parent_buf);
 560                         if (btrfs_header_nritems(&mid->header) <= orig_slot) {
 561                                 path->nodes[level] = right_buf;
 562                                 path->slots[level + 1] += 1;
 563                                 path->slots[level] = orig_slot -
 564                                         btrfs_header_nritems(&mid->header);
 565                                 btrfs_block_release(root, mid_buf);
 566                         } else {
 567                                 btrfs_block_release(root, right_buf);
 568                         }
 569                         check_node(root, path, level);
 570                         return 0;
 571                 }
 572                 btrfs_block_release(root, right_buf);
 573         }
 574         check_node(root, path, level);
 575         return 1;
 576 }
 577
 578 /*
 579  * look for key in the tree.  path is filled in with nodes along the way
 580  * if key is found, we return zero and you can find the item in the leaf
 581  * level of the path (level 0)
 582  *
 583  * If the key isn't found, the path points to the slot where it should
 584  * be inserted, and 1 is returned.  If there are other errors during the
 585  * search a negative error number is returned.
 586  *
 587  * if ins_len > 0, nodes and leaves will be split as we walk down the
 588  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
 589  * possible)
 590  */
 591 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
 592                       *root, struct btrfs_key *key, struct btrfs_path *p, int
 593                       ins_len, int cow)
 594 {
 595         struct buffer_head *b;
 596         struct buffer_head *cow_buf;
 597         struct btrfs_node *c;
 598         int slot;
 599         int ret;
 600         int level;
 601
 602         WARN_ON(p->nodes[0] != NULL);
 603         WARN_ON(!mutex_is_locked(&root->fs_info->fs_mutex));
 604 again:
 605         b = root->node;
 606         get_bh(b);
 607         while (b) {
 608                 c = btrfs_buffer_node(b);
 609                 level = btrfs_header_level(&c->header);
 610                 if (cow) {
 611                         int wret;
 612                         wret = btrfs_cow_block(trans, root, b,
 613                                                p->nodes[level + 1],
 614                                                p->slots[level + 1],
 615                                                &cow_buf);
 616                         b = cow_buf;
 617                         c = btrfs_buffer_node(b);
 618                 }
 619                 BUG_ON(!cow && ins_len);
 620                 if (level != btrfs_header_level(&c->header))
 621                         WARN_ON(1);
 622                 level = btrfs_header_level(&c->header);
 623                 p->nodes[level] = b;
 624                 ret = check_block(root, p, level);
 625                 if (ret)
 626                         return -1;
 627                 ret = bin_search(c, key, &slot);
 628                 if (!btrfs_is_leaf(c)) {
 629                         if (ret && slot > 0)
 630                                 slot -= 1;
 631                         p->slots[level] = slot;
 632                         if (ins_len > 0 && btrfs_header_nritems(&c->header) >=
 633                             BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
 634                                 int sret = split_node(trans, root, p, level);
 635                                 BUG_ON(sret > 0);
 636                                 if (sret)
 637                                         return sret;
 638                                 b = p->nodes[level];
 639                                 c = btrfs_buffer_node(b);
 640                                 slot = p->slots[level];
 641                         } else if (ins_len < 0) {
 642                                 int sret = balance_level(trans, root, p,
 643                                                          level);
 644                                 if (sret)
 645                                         return sret;
 646                                 b = p->nodes[level];
 647                                 if (!b)
 648                                         goto again;
 649                                 c = btrfs_buffer_node(b);
 650                                 slot = p->slots[level];
 651                                 BUG_ON(btrfs_header_nritems(&c->header) == 1);
 652                         }
 653                         b = read_tree_block(root, btrfs_node_blockptr(c, slot));
 654                 } else {
 655                         struct btrfs_leaf *l = (struct btrfs_leaf *)c;
 656                         p->slots[level] = slot;
 657                         if (ins_len > 0 && btrfs_leaf_free_space(root, l) <
 658                             sizeof(struct btrfs_item) + ins_len) {
 659                                 int sret = split_leaf(trans, root, key,
 660                                                       p, ins_len);
 661                                 BUG_ON(sret > 0);
 662                                 if (sret)
 663                                         return sret;
 664                         }
 665                         return ret;
 666                 }
 667         }
 668         return 1;
 669 }
 670
 671 /*
 672  * adjust the pointers going up the tree, starting at level
 673  * making sure the right key of each node is points to 'key'.
 674  * This is used after shifting pointers to the left, so it stops
 675  * fixing up pointers when a given leaf/node is not in slot 0 of the
 676  * higher levels
 677  *
 678  * If this fails to write a tree block, it returns -1, but continues
 679  * fixing up the blocks in ram so the tree is consistent.
 680  */
 681 static int fixup_low_keys(struct btrfs_trans_handle *trans, struct btrfs_root
 682                           *root, struct btrfs_path *path, struct btrfs_disk_key
 683                           *key, int level)
 684 {
 685         int i;
 686         int ret = 0;
 687         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
 688                 struct btrfs_node *t;
 689                 int tslot = path->slots[i];
 690                 if (!path->nodes[i])
 691                         break;
 692                 t = btrfs_buffer_node(path->nodes[i]);
 693                 btrfs_memcpy(root, t, &t->ptrs[tslot].key, key, sizeof(*key));
 694                 btrfs_mark_buffer_dirty(path->nodes[i]);
 695                 if (tslot != 0)
 696                         break;
 697         }
 698         return ret;
 699 }
 700
 701 /*
 702  * try to push data from one node into the next node left in the
 703  * tree.
 704  *
 705  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
 706  * error, and > 0 if there was no room in the left hand block.
 707  */
 708 static int push_node_left(struct btrfs_trans_handle *trans, struct btrfs_root
 709                           *root, struct buffer_head *dst_buf, struct
 710                           buffer_head *src_buf)
 711 {
 712         struct btrfs_node *src = btrfs_buffer_node(src_buf);
 713         struct btrfs_node *dst = btrfs_buffer_node(dst_buf);
 714         int push_items = 0;
 715         int src_nritems;
 716         int dst_nritems;
 717         int ret = 0;
 718
 719         src_nritems = btrfs_header_nritems(&src->header);
 720         dst_nritems = btrfs_header_nritems(&dst->header);
 721         push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
 722         if (push_items <= 0) {
 723                 return 1;
 724         }
 725
 726         if (src_nritems < push_items)
 727                 push_items = src_nritems;
 728
 729         btrfs_memcpy(root, dst, dst->ptrs + dst_nritems, src->ptrs,
 730                      push_items * sizeof(struct btrfs_key_ptr));
 731         if (push_items < src_nritems) {
 732                 btrfs_memmove(root, src, src->ptrs, src->ptrs + push_items,
 733                         (src_nritems - push_items) *
 734                         sizeof(struct btrfs_key_ptr));
 735         }
 736         btrfs_set_header_nritems(&src->header, src_nritems - push_items);
 737         btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 738         btrfs_mark_buffer_dirty(src_buf);
 739         btrfs_mark_buffer_dirty(dst_buf);
 740         return ret;
 741 }
 742
 743 /*
 744  * try to push data from one node into the next node right in the
 745  * tree.
 746  *
 747  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
 748  * error, and > 0 if there was no room in the right hand block.
 749  *
 750  * this will  only push up to 1/2 the contents of the left node over
 751  */
 752 static int balance_node_right(struct btrfs_trans_handle *trans, struct
 753                               btrfs_root *root, struct buffer_head *dst_buf,
 754                               struct buffer_head *src_buf)
 755 {
 756         struct btrfs_node *src = btrfs_buffer_node(src_buf);
 757         struct btrfs_node *dst = btrfs_buffer_node(dst_buf);
 758         int push_items = 0;
 759         int max_push;
 760         int src_nritems;
 761         int dst_nritems;
 762         int ret = 0;
 763
 764         src_nritems = btrfs_header_nritems(&src->header);
 765         dst_nritems = btrfs_header_nritems(&dst->header);
 766         push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
 767         if (push_items <= 0) {
 768                 return 1;
 769         }
 770
 771         max_push = src_nritems / 2 + 1;
 772         /* don't try to empty the node */
 773         if (max_push > src_nritems)
 774                 return 1;
 775         if (max_push < push_items)
 776                 push_items = max_push;
 777
 778         btrfs_memmove(root, dst, dst->ptrs + push_items, dst->ptrs,
 779                       dst_nritems * sizeof(struct btrfs_key_ptr));
 780
 781         btrfs_memcpy(root, dst, dst->ptrs,
 782                      src->ptrs + src_nritems - push_items,
 783                      push_items * sizeof(struct btrfs_key_ptr));
 784
 785         btrfs_set_header_nritems(&src->header, src_nritems - push_items);
 786         btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 787
 788         btrfs_mark_buffer_dirty(src_buf);
 789         btrfs_mark_buffer_dirty(dst_buf);
 790         return ret;
 791 }
 792
 793 /*
 794  * helper function to insert a new root level in the tree.
 795  * A new node is allocated, and a single item is inserted to
 796  * point to the existing root
 797  *
 798  * returns zero on success or < 0 on failure.
 799  */
 800 static int insert_new_root(struct btrfs_trans_handle *trans, struct btrfs_root
 801                            *root, struct btrfs_path *path, int level)
 802 {
 803         struct buffer_head *t;
 804         struct btrfs_node *lower;
 805         struct btrfs_node *c;
 806         struct btrfs_disk_key *lower_key;
 807
 808         BUG_ON(path->nodes[level]);
 809         BUG_ON(path->nodes[level-1] != root->node);
 810
 811         t = btrfs_alloc_free_block(trans, root, root->node->b_blocknr);
 812         c = btrfs_buffer_node(t);
 813         memset(c, 0, root->blocksize);
 814         btrfs_set_header_nritems(&c->header, 1);
 815         btrfs_set_header_level(&c->header, level);
 816         btrfs_set_header_blocknr(&c->header, bh_blocknr(t));
 817         btrfs_set_header_generation(&c->header, trans->transid);
 818         btrfs_set_header_owner(&c->header, root->root_key.objectid);
 819         lower = btrfs_buffer_node(path->nodes[level-1]);
 820         memcpy(c->header.fsid, root->fs_info->disk_super->fsid,
 821                sizeof(c->header.fsid));
 822         if (btrfs_is_leaf(lower))
 823                 lower_key = &((struct btrfs_leaf *)lower)->items[0].key;
 824         else
 825                 lower_key = &lower->ptrs[0].key;
 826         btrfs_memcpy(root, c, &c->ptrs[0].key, lower_key,
 827                      sizeof(struct btrfs_disk_key));
 828         btrfs_set_node_blockptr(c, 0, bh_blocknr(path->nodes[level - 1]));
 829
 830         btrfs_mark_buffer_dirty(t);
 831
 832         /* the super has an extra ref to root->node */
 833         btrfs_block_release(root, root->node);
 834         root->node = t;
 835         get_bh(t);
 836         path->nodes[level] = t;
 837         path->slots[level] = 0;
 838         return 0;
 839 }
 840
 841 /*
 842  * worker function to insert a single pointer in a node.
 843  * the node should have enough room for the pointer already
 844  *
 845  * slot and level indicate where you want the key to go, and
 846  * blocknr is the block the key points to.
 847  *
 848  * returns zero on success and < 0 on any error
 849  */
 850 static int insert_ptr(struct btrfs_trans_handle *trans, struct btrfs_root
 851                       *root, struct btrfs_path *path, struct btrfs_disk_key
 852                       *key, u64 blocknr, int slot, int level)
 853 {
 854         struct btrfs_node *lower;
 855         int nritems;
 856
 857         BUG_ON(!path->nodes[level]);
 858         lower = btrfs_buffer_node(path->nodes[level]);
 859         nritems = btrfs_header_nritems(&lower->header);
 860         if (slot > nritems)
 861                 BUG();
 862         if (nritems == BTRFS_NODEPTRS_PER_BLOCK(root))
 863                 BUG();
 864         if (slot != nritems) {
 865                 btrfs_memmove(root, lower, lower->ptrs + slot + 1,
 866                               lower->ptrs + slot,
 867                               (nritems - slot) * sizeof(struct btrfs_key_ptr));
 868         }
 869         btrfs_memcpy(root, lower, &lower->ptrs[slot].key,
 870                      key, sizeof(struct btrfs_disk_key));
 871         btrfs_set_node_blockptr(lower, slot, blocknr);
 872         btrfs_set_header_nritems(&lower->header, nritems + 1);
 873         btrfs_mark_buffer_dirty(path->nodes[level]);
 874         check_node(root, path, level);
 875         return 0;
 876 }
 877
 878 /*
 879  * split the node at the specified level in path in two.
 880  * The path is corrected to point to the appropriate node after the split
 881  *
 882  * Before splitting this tries to make some room in the node by pushing
 883  * left and right, if either one works, it returns right away.
 884  *
 885  * returns 0 on success and < 0 on failure
 886  */
 887 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
 888                       *root, struct btrfs_path *path, int level)
 889 {
 890         struct buffer_head *t;
 891         struct btrfs_node *c;
 892         struct buffer_head *split_buffer;
 893         struct btrfs_node *split;
 894         int mid;
 895         int ret;
 896         int wret;
 897         u32 c_nritems;
 898
 899         t = path->nodes[level];
 900         c = btrfs_buffer_node(t);
 901         if (t == root->node) {
 902                 /* trying to split the root, lets make a new one */
 903                 ret = insert_new_root(trans, root, path, level + 1);
 904                 if (ret)
 905                         return ret;
 906         } else {
 907                 ret = push_nodes_for_insert(trans, root, path, level);
 908                 t = path->nodes[level];
 909                 c = btrfs_buffer_node(t);
 910                 if (!ret &&
 911                     btrfs_header_nritems(&c->header) <
 912                     BTRFS_NODEPTRS_PER_BLOCK(root) - 1)
 913                         return 0;
 914         }
 915
 916         c_nritems = btrfs_header_nritems(&c->header);
 917         split_buffer = btrfs_alloc_free_block(trans, root, t->b_blocknr);
 918         split = btrfs_buffer_node(split_buffer);
 919         btrfs_set_header_flags(&split->header, btrfs_header_flags(&c->header));
 920         btrfs_set_header_level(&split->header, btrfs_header_level(&c->header));
 921         btrfs_set_header_blocknr(&split->header, bh_blocknr(split_buffer));
 922         btrfs_set_header_generation(&split->header, trans->transid);
 923         btrfs_set_header_owner(&split->header, root->root_key.objectid);
 924         memcpy(split->header.fsid, root->fs_info->disk_super->fsid,
 925                sizeof(split->header.fsid));
 926         mid = (c_nritems + 1) / 2;
 927         btrfs_memcpy(root, split, split->ptrs, c->ptrs + mid,
 928                      (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
 929         btrfs_set_header_nritems(&split->header, c_nritems - mid);
 930         btrfs_set_header_nritems(&c->header, mid);
 931         ret = 0;
 932
 933         btrfs_mark_buffer_dirty(t);
 934         btrfs_mark_buffer_dirty(split_buffer);
 935         wret = insert_ptr(trans, root, path, &split->ptrs[0].key,
 936                           bh_blocknr(split_buffer), path->slots[level + 1] + 1,
 937                           level + 1);
 938         if (wret)
 939                 ret = wret;
 940
 941         if (path->slots[level] >= mid) {
 942                 path->slots[level] -= mid;
 943                 btrfs_block_release(root, t);
 944                 path->nodes[level] = split_buffer;
 945                 path->slots[level + 1] += 1;
 946         } else {
 947                 btrfs_block_release(root, split_buffer);
 948         }
 949         return ret;
 950 }
 951
 952 /*
 953  * how many bytes are required to store the items in a leaf.  start
 954  * and nr indicate which items in the leaf to check.  This totals up the
 955  * space used both by the item structs and the item data
 956  */
 957 static int leaf_space_used(struct btrfs_leaf *l, int start, int nr)
 958 {
 959         int data_len;
 960         int nritems = btrfs_header_nritems(&l->header);
 961         int end = min(nritems, start + nr) - 1;
 962
 963         if (!nr)
 964                 return 0;
 965         data_len = btrfs_item_end(l->items + start);
 966         data_len = data_len - btrfs_item_offset(l->items + end);
 967         data_len += sizeof(struct btrfs_item) * nr;
 968         WARN_ON(data_len < 0);
 969         return data_len;
 970 }
 971
 972 /*
 973  * The space between the end of the leaf items and
 974  * the start of the leaf data.  IOW, how much room
 975  * the leaf has left for both items and data
 976  */
 977 int btrfs_leaf_free_space(struct btrfs_root *root, struct btrfs_leaf *leaf)
 978 {
 979         int nritems = btrfs_header_nritems(&leaf->header);
 980         return BTRFS_LEAF_DATA_SIZE(root) - leaf_space_used(leaf, 0, nritems);
 981 }
 982
 983 /*
 984  * push some data in the path leaf to the right, trying to free up at
 985  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 986  *
 987  * returns 1 if the push failed because the other node didn't have enough
 988  * room, 0 if everything worked out and < 0 if there were major errors.
 989  */
 990 static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 991                            *root, struct btrfs_path *path, int data_size)
 992 {
 993         struct buffer_head *left_buf = path->nodes[0];
 994         struct btrfs_leaf *left = btrfs_buffer_leaf(left_buf);
 995         struct btrfs_leaf *right;
 996         struct buffer_head *right_buf;
 997         struct buffer_head *upper;
 998         struct btrfs_node *upper_node;
 999         int slot;
1000         int i;
1001         int free_space;
1002         int push_space = 0;
1003         int push_items = 0;
1004         struct btrfs_item *item;
1005         u32 left_nritems;
1006         u32 right_nritems;
1007
1008         slot = path->slots[1];
1009         if (!path->nodes[1]) {
1010                 return 1;
1011         }
1012         upper = path->nodes[1];
1013         upper_node = btrfs_buffer_node(upper);
1014         if (slot >= btrfs_header_nritems(&upper_node->header) - 1) {
1015                 return 1;
1016         }
1017         right_buf = read_tree_block(root,
1018                     btrfs_node_blockptr(btrfs_buffer_node(upper), slot + 1));
1019         right = btrfs_buffer_leaf(right_buf);
1020         free_space = btrfs_leaf_free_space(root, right);
1021         if (free_space < data_size + sizeof(struct btrfs_item)) {
1022                 btrfs_block_release(root, right_buf);
1023                 return 1;
1024         }
1025         /* cow and double check */
1026         btrfs_cow_block(trans, root, right_buf, upper, slot + 1, &right_buf);
1027         right = btrfs_buffer_leaf(right_buf);
1028         free_space = btrfs_leaf_free_space(root, right);
1029         if (free_space < data_size + sizeof(struct btrfs_item)) {
1030                 btrfs_block_release(root, right_buf);
1031                 return 1;
1032         }
1033
1034         left_nritems = btrfs_header_nritems(&left->header);
1035         if (left_nritems == 0) {
1036                 btrfs_block_release(root, right_buf);
1037                 return 1;
1038         }
1039         for (i = left_nritems - 1; i >= 1; i--) {
1040                 item = left->items + i;
1041                 if (path->slots[0] == i)
1042                         push_space += data_size + sizeof(*item);
1043                 if (btrfs_item_size(item) + sizeof(*item) + push_space >
1044                     free_space)
1045                         break;
1046                 push_items++;
1047                 push_space += btrfs_item_size(item) + sizeof(*item);
1048         }
1049         if (push_items == 0) {
1050                 btrfs_block_release(root, right_buf);
1051                 return 1;
1052         }
1053         if (push_items == left_nritems)
1054                 WARN_ON(1);
1055         right_nritems = btrfs_header_nritems(&right->header);
1056         /* push left to right */
1057         push_space = btrfs_item_end(left->items + left_nritems - push_items);
1058         push_space -= leaf_data_end(root, left);
1059         /* make room in the right data area */
1060         btrfs_memmove(root, right, btrfs_leaf_data(right) +
1061                       leaf_data_end(root, right) - push_space,
1062                       btrfs_leaf_data(right) +
1063                       leaf_data_end(root, right), BTRFS_LEAF_DATA_SIZE(root) -
1064                       leaf_data_end(root, right));
1065         /* copy from the left data area */
1066         btrfs_memcpy(root, right, btrfs_leaf_data(right) +
1067                      BTRFS_LEAF_DATA_SIZE(root) - push_space,
1068                      btrfs_leaf_data(left) + leaf_data_end(root, left),
1069                      push_space);
1070         btrfs_memmove(root, right, right->items + push_items, right->items,
1071                 right_nritems * sizeof(struct btrfs_item));
1072         /* copy the items from left to right */
1073         btrfs_memcpy(root, right, right->items, left->items +
1074                      left_nritems - push_items,
1075                      push_items * sizeof(struct btrfs_item));
1076
1077         /* update the item pointers */
1078         right_nritems += push_items;
1079         btrfs_set_header_nritems(&right->header, right_nritems);
1080         push_space = BTRFS_LEAF_DATA_SIZE(root);
1081         for (i = 0; i < right_nritems; i++) {
1082                 btrfs_set_item_offset(right->items + i, push_space -
1083                                       btrfs_item_size(right->items + i));
1084                 push_space = btrfs_item_offset(right->items + i);
1085         }
1086         left_nritems -= push_items;
1087         btrfs_set_header_nritems(&left->header, left_nritems);
1088
1089         btrfs_mark_buffer_dirty(left_buf);
1090         btrfs_mark_buffer_dirty(right_buf);
1091
1092         btrfs_memcpy(root, upper_node, &upper_node->ptrs[slot + 1].key,
1093                 &right->items[0].key, sizeof(struct btrfs_disk_key));
1094         btrfs_mark_buffer_dirty(upper);
1095
1096         /* then fixup the leaf pointer in the path */
1097         if (path->slots[0] >= left_nritems) {
1098                 path->slots[0] -= left_nritems;
1099                 btrfs_block_release(root, path->nodes[0]);
1100                 path->nodes[0] = right_buf;
1101                 path->slots[1] += 1;
1102         } else {
1103                 btrfs_block_release(root, right_buf);
1104         }
1105         if (path->nodes[1])
1106                 check_node(root, path, 1);
1107         return 0;
1108 }
1109 /*
1110  * push some data in the path leaf to the left, trying to free up at
1111  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
1112  */
1113 static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
1114                           *root, struct btrfs_path *path, int data_size)
1115 {
1116         struct buffer_head *right_buf = path->nodes[0];
1117         struct btrfs_leaf *right = btrfs_buffer_leaf(right_buf);
1118         struct buffer_head *t;
1119         struct btrfs_leaf *left;
1120         int slot;
1121         int i;
1122         int free_space;
1123         int push_space = 0;
1124         int push_items = 0;
1125         struct btrfs_item *item;
1126         u32 old_left_nritems;
1127         int ret = 0;
1128         int wret;
1129
1130         slot = path->slots[1];
1131         if (slot == 0) {
1132                 return 1;
1133         }
1134         if (!path->nodes[1]) {
1135                 return 1;
1136         }
1137         t = read_tree_block(root,
1138             btrfs_node_blockptr(btrfs_buffer_node(path->nodes[1]), slot - 1));
1139         left = btrfs_buffer_leaf(t);
1140         free_space = btrfs_leaf_free_space(root, left);
1141         if (free_space < data_size + sizeof(struct btrfs_item)) {
1142                 btrfs_block_release(root, t);
1143                 return 1;
1144         }
1145
1146         /* cow and double check */
1147         btrfs_cow_block(trans, root, t, path->nodes[1], slot - 1, &t);
1148         left = btrfs_buffer_leaf(t);
1149         free_space = btrfs_leaf_free_space(root, left);
1150         if (free_space < data_size + sizeof(struct btrfs_item)) {
1151                 btrfs_block_release(root, t);
1152                 return 1;
1153         }
1154
1155         if (btrfs_header_nritems(&right->header) == 0) {
1156                 btrfs_block_release(root, t);
1157                 return 1;
1158         }
1159
1160         for (i = 0; i < btrfs_header_nritems(&right->header) - 1; i++) {
1161                 item = right->items + i;
1162                 if (path->slots[0] == i)
1163                         push_space += data_size + sizeof(*item);
1164                 if (btrfs_item_size(item) + sizeof(*item) + push_space >
1165                     free_space)
1166                         break;
1167                 push_items++;
1168                 push_space += btrfs_item_size(item) + sizeof(*item);
1169         }
1170         if (push_items == 0) {
1171                 btrfs_block_release(root, t);
1172                 return 1;
1173         }
1174         if (push_items == btrfs_header_nritems(&right->header))
1175                 WARN_ON(1);
1176         /* push data from right to left */
1177         btrfs_memcpy(root, left, left->items +
1178                      btrfs_header_nritems(&left->header),
1179                      right->items, push_items * sizeof(struct btrfs_item));
1180         push_space = BTRFS_LEAF_DATA_SIZE(root) -
1181                      btrfs_item_offset(right->items + push_items -1);
1182         btrfs_memcpy(root, left, btrfs_leaf_data(left) +
1183                      leaf_data_end(root, left) - push_space,
1184                      btrfs_leaf_data(right) +
1185                      btrfs_item_offset(right->items + push_items - 1),
1186                      push_space);
1187         old_left_nritems = btrfs_header_nritems(&left->header);
1188         BUG_ON(old_left_nritems < 0);
1189
1190         for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
1191                 u32 ioff = btrfs_item_offset(left->items + i);
1192                 btrfs_set_item_offset(left->items + i, ioff -
1193                                      (BTRFS_LEAF_DATA_SIZE(root) -
1194                                       btrfs_item_offset(left->items +
1195                                                         old_left_nritems - 1)));
1196         }
1197         btrfs_set_header_nritems(&left->header, old_left_nritems + push_items);
1198
1199         /* fixup right node */
1200         push_space = btrfs_item_offset(right->items + push_items - 1) -
1201                      leaf_data_end(root, right);
1202         btrfs_memmove(root, right, btrfs_leaf_data(right) +
1203                       BTRFS_LEAF_DATA_SIZE(root) - push_space,
1204                       btrfs_leaf_data(right) +
1205                       leaf_data_end(root, right), push_space);
1206         btrfs_memmove(root, right, right->items, right->items + push_items,
1207                 (btrfs_header_nritems(&right->header) - push_items) *
1208                 sizeof(struct btrfs_item));
1209         btrfs_set_header_nritems(&right->header,
1210                                  btrfs_header_nritems(&right->header) -
1211                                  push_items);
1212         push_space = BTRFS_LEAF_DATA_SIZE(root);
1213
1214         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
1215                 btrfs_set_item_offset(right->items + i, push_space -
1216                                       btrfs_item_size(right->items + i));
1217                 push_space = btrfs_item_offset(right->items + i);
1218         }
1219
1220         btrfs_mark_buffer_dirty(t);
1221         btrfs_mark_buffer_dirty(right_buf);
1222
1223         wret = fixup_low_keys(trans, root, path, &right->items[0].key, 1);
1224         if (wret)
1225                 ret = wret;
1226
1227         /* then fixup the leaf pointer in the path */
1228         if (path->slots[0] < push_items) {
1229                 path->slots[0] += old_left_nritems;
1230                 btrfs_block_release(root, path->nodes[0]);
1231                 path->nodes[0] = t;
1232                 path->slots[1] -= 1;
1233         } else {
1234                 btrfs_block_release(root, t);
1235                 path->slots[0] -= push_items;
1236         }
1237         BUG_ON(path->slots[0] < 0);
1238         if (path->nodes[1])
1239                 check_node(root, path, 1);
1240         return ret;
1241 }
1242
1243 /*
1244  * split the path's leaf in two, making sure there is at least data_size
1245  * available for the resulting leaf level of the path.
1246  *
1247  * returns 0 if all went well and < 0 on failure.
1248  */
1249 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
1250                       *root, struct btrfs_key *ins_key,
1251                       struct btrfs_path *path, int data_size)
1252 {
1253         struct buffer_head *l_buf;
1254         struct btrfs_leaf *l;
1255         u32 nritems;
1256         int mid;
1257         int slot;
1258         struct btrfs_leaf *right;
1259         struct buffer_head *right_buffer;
1260         int space_needed = data_size + sizeof(struct btrfs_item);
1261         int data_copy_size;
1262         int rt_data_off;
1263         int i;
1264         int ret = 0;
1265         int wret;
1266         int double_split = 0;
1267         struct btrfs_disk_key disk_key;
1268
1269         /* first try to make some room by pushing left and right */
1270         wret = push_leaf_left(trans, root, path, data_size);
1271         if (wret < 0)
1272                 return wret;
1273         if (wret) {
1274                 wret = push_leaf_right(trans, root, path, data_size);
1275                 if (wret < 0)
1276                         return wret;
1277         }
1278         l_buf = path->nodes[0];
1279         l = btrfs_buffer_leaf(l_buf);
1280
1281         /* did the pushes work? */
1282         if (btrfs_leaf_free_space(root, l) >=
1283             sizeof(struct btrfs_item) + data_size)
1284                 return 0;
1285
1286         if (!path->nodes[1]) {
1287                 ret = insert_new_root(trans, root, path, 1);
1288                 if (ret)
1289                         return ret;
1290         }
1291         slot = path->slots[0];
1292         nritems = btrfs_header_nritems(&l->header);
1293         mid = (nritems + 1)/ 2;
1294         right_buffer = btrfs_alloc_free_block(trans, root, l_buf->b_blocknr);
1295         BUG_ON(!right_buffer);
1296         right = btrfs_buffer_leaf(right_buffer);
1297         memset(&right->header, 0, sizeof(right->header));
1298         btrfs_set_header_blocknr(&right->header, bh_blocknr(right_buffer));
1299         btrfs_set_header_generation(&right->header, trans->transid);
1300         btrfs_set_header_owner(&right->header, root->root_key.objectid);
1301         btrfs_set_header_level(&right->header, 0);
1302         memcpy(right->header.fsid, root->fs_info->disk_super->fsid,
1303                sizeof(right->header.fsid));
1304         if (mid <= slot) {
1305                 if (nritems == 1 ||
1306                     leaf_space_used(l, mid, nritems - mid) + space_needed >
1307                         BTRFS_LEAF_DATA_SIZE(root)) {
1308                         if (slot >= nritems) {
1309                                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
1310                                 btrfs_set_header_nritems(&right->header, 0);
1311                                 wret = insert_ptr(trans, root, path,
1312                                                   &disk_key,
1313                                                   bh_blocknr(right_buffer),
1314                                                   path->slots[1] + 1, 1);
1315                                 if (wret)
1316                                         ret = wret;
1317                                 btrfs_block_release(root, path->nodes[0]);
1318                                 path->nodes[0] = right_buffer;
1319                                 path->slots[0] = 0;
1320                                 path->slots[1] += 1;
1321                                 return ret;
1322                         }
1323                         mid = slot;
1324                         double_split = 1;
1325                 }
1326         } else {
1327                 if (leaf_space_used(l, 0, mid + 1) + space_needed >
1328                         BTRFS_LEAF_DATA_SIZE(root)) {
1329                         if (slot == 0) {
1330                                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
1331                                 btrfs_set_header_nritems(&right->header, 0);
1332                                 wret = insert_ptr(trans, root, path,
1333                                                   &disk_key,
1334                                                   bh_blocknr(right_buffer),
1335                                                   path->slots[1], 1);
1336                                 if (wret)
1337                                         ret = wret;
1338                                 btrfs_block_release(root, path->nodes[0]);
1339                                 path->nodes[0] = right_buffer;
1340                                 path->slots[0] = 0;
1341                                 if (path->slots[1] == 0) {
1342                                         wret = fixup_low_keys(trans, root,
1343                                                    path, &disk_key, 1);
1344                                         if (wret)
1345                                                 ret = wret;
1346                                 }
1347                                 return ret;
1348                         }
1349                         mid = slot;
1350                         double_split = 1;
1351                 }
1352         }
1353         btrfs_set_header_nritems(&right->header, nritems - mid);
1354         data_copy_size = btrfs_item_end(l->items + mid) -
1355                          leaf_data_end(root, l);
1356         btrfs_memcpy(root, right, right->items, l->items + mid,
1357                      (nritems - mid) * sizeof(struct btrfs_item));
1358         btrfs_memcpy(root, right,
1359                      btrfs_leaf_data(right) + BTRFS_LEAF_DATA_SIZE(root) -
1360                      data_copy_size, btrfs_leaf_data(l) +
1361                      leaf_data_end(root, l), data_copy_size);
1362         rt_data_off = BTRFS_LEAF_DATA_SIZE(root) -
1363                       btrfs_item_end(l->items + mid);
1364
1365         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
1366                 u32 ioff = btrfs_item_offset(right->items + i);
1367                 btrfs_set_item_offset(right->items + i, ioff + rt_data_off);
1368         }
1369
1370         btrfs_set_header_nritems(&l->header, mid);
1371         ret = 0;
1372         wret = insert_ptr(trans, root, path, &right->items[0].key,
1373                           bh_blocknr(right_buffer), path->slots[1] + 1, 1);
1374         if (wret)
1375                 ret = wret;
1376         btrfs_mark_buffer_dirty(right_buffer);
1377         btrfs_mark_buffer_dirty(l_buf);
1378         BUG_ON(path->slots[0] != slot);
1379         if (mid <= slot) {
1380                 btrfs_block_release(root, path->nodes[0]);
1381                 path->nodes[0] = right_buffer;
1382                 path->slots[0] -= mid;
1383                 path->slots[1] += 1;
1384         } else
1385                 btrfs_block_release(root, right_buffer);
1386         BUG_ON(path->slots[0] < 0);
1387         check_node(root, path, 1);
1388
1389         if (!double_split)
1390                 return ret;
1391         right_buffer = btrfs_alloc_free_block(trans, root, l_buf->b_blocknr);
1392         BUG_ON(!right_buffer);
1393         right = btrfs_buffer_leaf(right_buffer);
1394         memset(&right->header, 0, sizeof(right->header));
1395         btrfs_set_header_blocknr(&right->header, bh_blocknr(right_buffer));
1396         btrfs_set_header_generation(&right->header, trans->transid);
1397         btrfs_set_header_owner(&right->header, root->root_key.objectid);
1398         btrfs_set_header_level(&right->header, 0);
1399         memcpy(right->header.fsid, root->fs_info->disk_super->fsid,
1400                sizeof(right->header.fsid));
1401         btrfs_cpu_key_to_disk(&disk_key, ins_key);
1402         btrfs_set_header_nritems(&right->header, 0);
1403         wret = insert_ptr(trans, root, path,
1404                           &disk_key,
1405                           bh_blocknr(right_buffer),
1406                           path->slots[1], 1);
1407         if (wret)
1408                 ret = wret;
1409         if (path->slots[1] == 0) {
1410                 wret = fixup_low_keys(trans, root, path, &disk_key, 1);
1411                 if (wret)
1412                         ret = wret;
1413         }
1414         btrfs_block_release(root, path->nodes[0]);
1415         path->nodes[0] = right_buffer;
1416         path->slots[0] = 0;
1417         check_node(root, path, 1);
1418         check_leaf(root, path, 0);
1419         return ret;
1420 }
1421
1422 int btrfs_truncate_item(struct btrfs_trans_handle *trans,
1423                         struct btrfs_root *root,
1424                         struct btrfs_path *path,
1425                         u32 new_size)
1426 {
1427         int ret = 0;
1428         int slot;
1429         int slot_orig;
1430         struct btrfs_leaf *leaf;
1431         struct buffer_head *leaf_buf;
1432         u32 nritems;
1433         unsigned int data_end;
1434         unsigned int old_data_start;
1435         unsigned int old_size;
1436         unsigned int size_diff;
1437         int i;
1438
1439         slot_orig = path->slots[0];
1440         leaf_buf = path->nodes[0];
1441         leaf = btrfs_buffer_leaf(leaf_buf);
1442
1443         nritems = btrfs_header_nritems(&leaf->header);
1444         data_end = leaf_data_end(root, leaf);
1445
1446         slot = path->slots[0];
1447         old_data_start = btrfs_item_offset(leaf->items + slot);
1448         old_size = btrfs_item_size(leaf->items + slot);
1449         BUG_ON(old_size <= new_size);
1450         size_diff = old_size - new_size;
1451
1452         BUG_ON(slot < 0);
1453         BUG_ON(slot >= nritems);
1454
1455         /*
1456          * item0..itemN ... dataN.offset..dataN.size .. data0.size
1457          */
1458         /* first correct the data pointers */
1459         for (i = slot; i < nritems; i++) {
1460                 u32 ioff = btrfs_item_offset(leaf->items + i);
1461                 btrfs_set_item_offset(leaf->items + i,
1462                                       ioff + size_diff);
1463         }
1464         /* shift the data */
1465         btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1466                       data_end + size_diff, btrfs_leaf_data(leaf) +
1467                       data_end, old_data_start + new_size - data_end);
1468         btrfs_set_item_size(leaf->items + slot, new_size);
1469         btrfs_mark_buffer_dirty(leaf_buf);
1470
1471         ret = 0;
1472         if (btrfs_leaf_free_space(root, leaf) < 0)
1473                 BUG();
1474         check_leaf(root, path, 0);
1475         return ret;
1476 }
1477
1478 int btrfs_extend_item(struct btrfs_trans_handle *trans, struct btrfs_root
1479                       *root, struct btrfs_path *path, u32 data_size)
1480 {
1481         int ret = 0;
1482         int slot;
1483         int slot_orig;
1484         struct btrfs_leaf *leaf;
1485         struct buffer_head *leaf_buf;
1486         u32 nritems;
1487         unsigned int data_end;
1488         unsigned int old_data;
1489         unsigned int old_size;
1490         int i;
1491
1492         slot_orig = path->slots[0];
1493         leaf_buf = path->nodes[0];
1494         leaf = btrfs_buffer_leaf(leaf_buf);
1495
1496         nritems = btrfs_header_nritems(&leaf->header);
1497         data_end = leaf_data_end(root, leaf);
1498
1499         if (btrfs_leaf_free_space(root, leaf) < data_size)
1500                 BUG();
1501         slot = path->slots[0];
1502         old_data = btrfs_item_end(leaf->items + slot);
1503
1504         BUG_ON(slot < 0);
1505         BUG_ON(slot >= nritems);
1506
1507         /*
1508          * item0..itemN ... dataN.offset..dataN.size .. data0.size
1509          */
1510         /* first correct the data pointers */
1511         for (i = slot; i < nritems; i++) {
1512                 u32 ioff = btrfs_item_offset(leaf->items + i);
1513                 btrfs_set_item_offset(leaf->items + i,
1514                                       ioff - data_size);
1515         }
1516         /* shift the data */
1517         btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1518                       data_end - data_size, btrfs_leaf_data(leaf) +
1519                       data_end, old_data - data_end);
1520         data_end = old_data;
1521         old_size = btrfs_item_size(leaf->items + slot);
1522         btrfs_set_item_size(leaf->items + slot, old_size + data_size);
1523         btrfs_mark_buffer_dirty(leaf_buf);
1524
1525         ret = 0;
1526         if (btrfs_leaf_free_space(root, leaf) < 0)
1527                 BUG();
1528         check_leaf(root, path, 0);
1529         return ret;
1530 }
1531
1532 /*
1533  * Given a key and some data, insert an item into the tree.
1534  * This does all the path init required, making room in the tree if needed.
1535  */
1536 int btrfs_insert_empty_item(struct btrfs_trans_handle *trans, struct btrfs_root
1537                             *root, struct btrfs_path *path, struct btrfs_key
1538                             *cpu_key, u32 data_size)
1539 {
1540         int ret = 0;
1541         int slot;
1542         int slot_orig;
1543         struct btrfs_leaf *leaf;
1544         struct buffer_head *leaf_buf;
1545         u32 nritems;
1546         unsigned int data_end;
1547         struct btrfs_disk_key disk_key;
1548
1549         btrfs_cpu_key_to_disk(&disk_key, cpu_key);
1550
1551         /* create a root if there isn't one */
1552         if (!root->node)
1553                 BUG();
1554         ret = btrfs_search_slot(trans, root, cpu_key, path, data_size, 1);
1555         if (ret == 0) {
1556                 return -EEXIST;
1557         }
1558         if (ret < 0)
1559                 goto out;
1560
1561         slot_orig = path->slots[0];
1562         leaf_buf = path->nodes[0];
1563         leaf = btrfs_buffer_leaf(leaf_buf);
1564
1565         nritems = btrfs_header_nritems(&leaf->header);
1566         data_end = leaf_data_end(root, leaf);
1567
1568         if (btrfs_leaf_free_space(root, leaf) <
1569             sizeof(struct btrfs_item) + data_size) {
1570                 BUG();
1571         }
1572         slot = path->slots[0];
1573         BUG_ON(slot < 0);
1574         if (slot != nritems) {
1575                 int i;
1576                 unsigned int old_data = btrfs_item_end(leaf->items + slot);
1577
1578                 /*
1579                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
1580                  */
1581                 /* first correct the data pointers */
1582                 for (i = slot; i < nritems; i++) {
1583                         u32 ioff = btrfs_item_offset(leaf->items + i);
1584                         btrfs_set_item_offset(leaf->items + i,
1585                                               ioff - data_size);
1586                 }
1587
1588                 /* shift the items */
1589                 btrfs_memmove(root, leaf, leaf->items + slot + 1,
1590                               leaf->items + slot,
1591                               (nritems - slot) * sizeof(struct btrfs_item));
1592
1593                 /* shift the data */
1594                 btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1595                               data_end - data_size, btrfs_leaf_data(leaf) +
1596                               data_end, old_data - data_end);
1597                 data_end = old_data;
1598         }
1599         /* setup the item for the new data */
1600         btrfs_memcpy(root, leaf, &leaf->items[slot].key, &disk_key,
1601                      sizeof(struct btrfs_disk_key));
1602         btrfs_set_item_offset(leaf->items + slot, data_end - data_size);
1603         btrfs_set_item_size(leaf->items + slot, data_size);
1604         btrfs_set_header_nritems(&leaf->header, nritems + 1);
1605         btrfs_mark_buffer_dirty(leaf_buf);
1606
1607         ret = 0;
1608         if (slot == 0)
1609                 ret = fixup_low_keys(trans, root, path, &disk_key, 1);
1610
1611         if (btrfs_leaf_free_space(root, leaf) < 0)
1612                 BUG();
1613         check_leaf(root, path, 0);
1614 out:
1615         return ret;
1616 }
1617
1618 /*
1619  * Given a key and some data, insert an item into the tree.
1620  * This does all the path init required, making room in the tree if needed.
1621  */
1622 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root
1623                       *root, struct btrfs_key *cpu_key, void *data, u32
1624                       data_size)
1625 {
1626         int ret = 0;
1627         struct btrfs_path *path;
1628         u8 *ptr;
1629
1630         path = btrfs_alloc_path();
1631         BUG_ON(!path);
1632         btrfs_init_path(path);
1633         ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
1634         if (!ret) {
1635                 ptr = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]),
1636                                      path->slots[0], u8);
1637                 btrfs_memcpy(root, path->nodes[0]->b_data,
1638                              ptr, data, data_size);
1639                 btrfs_mark_buffer_dirty(path->nodes[0]);
1640         }
1641         btrfs_release_path(root, path);
1642         btrfs_free_path(path);
1643         return ret;
1644 }
1645
1646 /*
1647  * delete the pointer from a given node.
1648  *
1649  * If the delete empties a node, the node is removed from the tree,
1650  * continuing all the way the root if required.  The root is converted into
1651  * a leaf if all the nodes are emptied.
1652  */
1653 static int del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
1654                    struct btrfs_path *path, int level, int slot)
1655 {
1656         struct btrfs_node *node;
1657         struct buffer_head *parent = path->nodes[level];
1658         u32 nritems;
1659         int ret = 0;
1660         int wret;
1661
1662         node = btrfs_buffer_node(parent);
1663         nritems = btrfs_header_nritems(&node->header);
1664         if (slot != nritems -1) {
1665                 btrfs_memmove(root, node, node->ptrs + slot,
1666                               node->ptrs + slot + 1,
1667                               sizeof(struct btrfs_key_ptr) *
1668                               (nritems - slot - 1));
1669         }
1670         nritems--;
1671         btrfs_set_header_nritems(&node->header, nritems);
1672         if (nritems == 0 && parent == root->node) {
1673                 struct btrfs_header *header = btrfs_buffer_header(root->node);
1674                 BUG_ON(btrfs_header_level(header) != 1);
1675                 /* just turn the root into a leaf and break */
1676                 btrfs_set_header_level(header, 0);
1677         } else if (slot == 0) {
1678                 wret = fixup_low_keys(trans, root, path, &node->ptrs[0].key,
1679                                       level + 1);
1680                 if (wret)
1681                         ret = wret;
1682         }
1683         btrfs_mark_buffer_dirty(parent);
1684         return ret;
1685 }
1686
1687 /*
1688  * delete the item at the leaf level in path.  If that empties
1689  * the leaf, remove it from the tree
1690  */
1691 int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
1692                    struct btrfs_path *path)
1693 {
1694         int slot;
1695         struct btrfs_leaf *leaf;
1696         struct buffer_head *leaf_buf;
1697         int doff;
1698         int dsize;
1699         int ret = 0;
1700         int wret;
1701         u32 nritems;
1702
1703         leaf_buf = path->nodes[0];
1704         leaf = btrfs_buffer_leaf(leaf_buf);
1705         slot = path->slots[0];
1706         doff = btrfs_item_offset(leaf->items + slot);
1707         dsize = btrfs_item_size(leaf->items + slot);
1708         nritems = btrfs_header_nritems(&leaf->header);
1709
1710         if (slot != nritems - 1) {
1711                 int i;
1712                 int data_end = leaf_data_end(root, leaf);
1713                 btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1714                               data_end + dsize,
1715                               btrfs_leaf_data(leaf) + data_end,
1716                               doff - data_end);
1717                 for (i = slot + 1; i < nritems; i++) {
1718                         u32 ioff = btrfs_item_offset(leaf->items + i);
1719                         btrfs_set_item_offset(leaf->items + i, ioff + dsize);
1720                 }
1721                 btrfs_memmove(root, leaf, leaf->items + slot,
1722                               leaf->items + slot + 1,
1723                               sizeof(struct btrfs_item) *
1724                               (nritems - slot - 1));
1725         }
1726         btrfs_set_header_nritems(&leaf->header, nritems - 1);
1727         nritems--;
1728         /* delete the leaf if we've emptied it */
1729         if (nritems == 0) {
1730                 if (leaf_buf == root->node) {
1731                         btrfs_set_header_level(&leaf->header, 0);
1732                 } else {
1733                         clean_tree_block(trans, root, leaf_buf);
1734                         wait_on_buffer(leaf_buf);
1735                         wret = del_ptr(trans, root, path, 1, path->slots[1]);
1736                         if (wret)
1737                                 ret = wret;
1738                         wret = btrfs_free_extent(trans, root,
1739                                                  bh_blocknr(leaf_buf), 1, 1);
1740                         if (wret)
1741                                 ret = wret;
1742                 }
1743         } else {
1744                 int used = leaf_space_used(leaf, 0, nritems);
1745                 if (slot == 0) {
1746                         wret = fixup_low_keys(trans, root, path,
1747                                               &leaf->items[0].key, 1);
1748                         if (wret)
1749                                 ret = wret;
1750                 }
1751
1752                 /* delete the leaf if it is mostly empty */
1753                 if (used < BTRFS_LEAF_DATA_SIZE(root) / 3) {
1754                         /* push_leaf_left fixes the path.
1755                          * make sure the path still points to our leaf
1756                          * for possible call to del_ptr below
1757                          */
1758                         slot = path->slots[1];
1759                         get_bh(leaf_buf);
1760                         wret = push_leaf_left(trans, root, path, 1);
1761                         if (wret < 0)
1762                                 ret = wret;
1763                         if (path->nodes[0] == leaf_buf &&
1764                             btrfs_header_nritems(&leaf->header)) {
1765                                 wret = push_leaf_right(trans, root, path, 1);
1766                                 if (wret < 0)
1767                                         ret = wret;
1768                         }
1769                         if (btrfs_header_nritems(&leaf->header) == 0) {
1770                                 u64 blocknr = bh_blocknr(leaf_buf);
1771                                 clean_tree_block(trans, root, leaf_buf);
1772                                 wait_on_buffer(leaf_buf);
1773                                 wret = del_ptr(trans, root, path, 1, slot);
1774                                 if (wret)
1775                                         ret = wret;
1776                                 btrfs_block_release(root, leaf_buf);
1777                                 wret = btrfs_free_extent(trans, root, blocknr,
1778                                                          1, 1);
1779                                 if (wret)
1780                                         ret = wret;
1781                         } else {
1782                                 btrfs_mark_buffer_dirty(leaf_buf);
1783                                 btrfs_block_release(root, leaf_buf);
1784                         }
1785                 } else {
1786                         btrfs_mark_buffer_dirty(leaf_buf);
1787                 }
1788         }
1789         return ret;
1790 }
1791
1792 /*
1793  * walk up the tree as far as required to find the next leaf.
1794  * returns 0 if it found something or 1 if there are no greater leaves.
1795  * returns < 0 on io errors.
1796  */
1797 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
1798 {
1799         int slot;
1800         int level = 1;
1801         u64 blocknr;
1802         struct buffer_head *c;
1803         struct btrfs_node *c_node;
1804         struct buffer_head *next = NULL;
1805
1806         while(level < BTRFS_MAX_LEVEL) {
1807                 if (!path->nodes[level])
1808                         return 1;
1809                 slot = path->slots[level] + 1;
1810                 c = path->nodes[level];
1811                 c_node = btrfs_buffer_node(c);
1812                 if (slot >= btrfs_header_nritems(&c_node->header)) {
1813                         level++;
1814                         continue;
1815                 }
1816                 blocknr = btrfs_node_blockptr(c_node, slot);
1817                 if (next)
1818                         btrfs_block_release(root, next);
1819                 next = read_tree_block(root, blocknr);
1820                 break;
1821         }
1822         path->slots[level] = slot;
1823         while(1) {
1824                 level--;
1825                 c = path->nodes[level];
1826                 btrfs_block_release(root, c);
1827                 path->nodes[level] = next;
1828                 path->slots[level] = 0;
1829                 if (!level)
1830                         break;
1831                 next = read_tree_block(root,
1832                        btrfs_node_blockptr(btrfs_buffer_node(next), 0));
1833         }
1834         return 0;
1835 }