git.oblomov.eu Git - linux-2.6/blob - 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         int i;
 134         struct btrfs_node *parent = NULL;
 135         struct btrfs_node *node = btrfs_buffer_node(path->nodes[level]);
 136         int parent_slot;
 137         u32 nritems = btrfs_header_nritems(&node->header);
 138
 139         if (path->nodes[level + 1])
 140                 parent = btrfs_buffer_node(path->nodes[level + 1]);
 141         parent_slot = path->slots[level + 1];
 142         BUG_ON(nritems == 0);
 143         if (parent) {
 144                 struct btrfs_disk_key *parent_key;
 145                 parent_key = &parent->ptrs[parent_slot].key;
 146                 BUG_ON(memcmp(parent_key, &node->ptrs[0].key,
 147                               sizeof(struct btrfs_disk_key)));
 148                 BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
 149                        btrfs_header_blocknr(&node->header));
 150         }
 151         BUG_ON(nritems > BTRFS_NODEPTRS_PER_BLOCK(root));
 152         for (i = 0; nritems > 1 && i < nritems - 2; i++) {
 153                 struct btrfs_key cpukey;
 154                 btrfs_disk_key_to_cpu(&cpukey, &node->ptrs[i + 1].key);
 155                 BUG_ON(comp_keys(&node->ptrs[i].key, &cpukey) >= 0);
 156         }
 157         return 0;
 158 }
 159
 160 static int check_leaf(struct btrfs_root *root, struct btrfs_path *path,
 161                       int level)
 162 {
 163         int i;
 164         struct btrfs_leaf *leaf = btrfs_buffer_leaf(path->nodes[level]);
 165         struct btrfs_node *parent = NULL;
 166         int parent_slot;
 167         u32 nritems = btrfs_header_nritems(&leaf->header);
 168
 169         if (path->nodes[level + 1])
 170                 parent = btrfs_buffer_node(path->nodes[level + 1]);
 171         parent_slot = path->slots[level + 1];
 172         BUG_ON(btrfs_leaf_free_space(root, leaf) < 0);
 173
 174         if (nritems == 0)
 175                 return 0;
 176
 177         if (parent) {
 178                 struct btrfs_disk_key *parent_key;
 179                 parent_key = &parent->ptrs[parent_slot].key;
 180                 BUG_ON(memcmp(parent_key, &leaf->items[0].key,
 181                        sizeof(struct btrfs_disk_key)));
 182                 BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
 183                        btrfs_header_blocknr(&leaf->header));
 184         }
 185         for (i = 0; nritems > 1 && i < nritems - 2; i++) {
 186                 struct btrfs_key cpukey;
 187                 btrfs_disk_key_to_cpu(&cpukey, &leaf->items[i + 1].key);
 188                 BUG_ON(comp_keys(&leaf->items[i].key,
 189                                  &cpukey) >= 0);
 190                 BUG_ON(btrfs_item_offset(leaf->items + i) !=
 191                         btrfs_item_end(leaf->items + i + 1));
 192                 if (i == 0) {
 193                         BUG_ON(btrfs_item_offset(leaf->items + i) +
 194                                btrfs_item_size(leaf->items + i) !=
 195                                BTRFS_LEAF_DATA_SIZE(root));
 196                 }
 197         }
 198         return 0;
 199 }
 200
 201 static int check_block(struct btrfs_root *root, struct btrfs_path *path,
 202                         int level)
 203 {
 204         struct btrfs_node *node = btrfs_buffer_node(path->nodes[level]);
 205         if (memcmp(node->header.fsid, root->fs_info->disk_super->fsid,
 206                    sizeof(node->header.fsid)))
 207                 BUG();
 208         if (level == 0)
 209                 return check_leaf(root, path, level);
 210         return check_node(root, path, level);
 211 }
 212
 213 /*
 214  * search for key in the array p.  items p are item_size apart
 215  * and there are 'max' items in p
 216  * the slot in the array is returned via slot, and it points to
 217  * the place where you would insert key if it is not found in
 218  * the array.
 219  *
 220  * slot may point to max if the key is bigger than all of the keys
 221  */
 222 static int generic_bin_search(char *p, int item_size, struct btrfs_key *key,
 223                        int max, int *slot)
 224 {
 225         int low = 0;
 226         int high = max;
 227         int mid;
 228         int ret;
 229         struct btrfs_disk_key *tmp;
 230
 231         while(low < high) {
 232                 mid = (low + high) / 2;
 233                 tmp = (struct btrfs_disk_key *)(p + mid * item_size);
 234                 ret = comp_keys(tmp, key);
 235
 236                 if (ret < 0)
 237                         low = mid + 1;
 238                 else if (ret > 0)
 239                         high = mid;
 240                 else {
 241                         *slot = mid;
 242                         return 0;
 243                 }
 244         }
 245         *slot = low;
 246         return 1;
 247 }
 248
 249 /*
 250  * simple bin_search frontend that does the right thing for
 251  * leaves vs nodes
 252  */
 253 static int bin_search(struct btrfs_node *c, struct btrfs_key *key, int *slot)
 254 {
 255         if (btrfs_is_leaf(c)) {
 256                 struct btrfs_leaf *l = (struct btrfs_leaf *)c;
 257                 return generic_bin_search((void *)l->items,
 258                                           sizeof(struct btrfs_item),
 259                                           key, btrfs_header_nritems(&c->header),
 260                                           slot);
 261         } else {
 262                 return generic_bin_search((void *)c->ptrs,
 263                                           sizeof(struct btrfs_key_ptr),
 264                                           key, btrfs_header_nritems(&c->header),
 265                                           slot);
 266         }
 267         return -1;
 268 }
 269
 270 static struct buffer_head *read_node_slot(struct btrfs_root *root,
 271                                    struct buffer_head *parent_buf,
 272                                    int slot)
 273 {
 274         struct btrfs_node *node = btrfs_buffer_node(parent_buf);
 275         if (slot < 0)
 276                 return NULL;
 277         if (slot >= btrfs_header_nritems(&node->header))
 278                 return NULL;
 279         return read_tree_block(root, btrfs_node_blockptr(node, slot));
 280 }
 281
 282 static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
 283                          *root, struct btrfs_path *path, int level)
 284 {
 285         struct buffer_head *right_buf;
 286         struct buffer_head *mid_buf;
 287         struct buffer_head *left_buf;
 288         struct buffer_head *parent_buf = NULL;
 289         struct btrfs_node *right = NULL;
 290         struct btrfs_node *mid;
 291         struct btrfs_node *left = NULL;
 292         struct btrfs_node *parent = NULL;
 293         int ret = 0;
 294         int wret;
 295         int pslot;
 296         int orig_slot = path->slots[level];
 297         u64 orig_ptr;
 298
 299         if (level == 0)
 300                 return 0;
 301
 302         mid_buf = path->nodes[level];
 303         mid = btrfs_buffer_node(mid_buf);
 304         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 305
 306         if (level < BTRFS_MAX_LEVEL - 1)
 307                 parent_buf = path->nodes[level + 1];
 308         pslot = path->slots[level + 1];
 309
 310         /*
 311          * deal with the case where there is only one pointer in the root
 312          * by promoting the node below to a root
 313          */
 314         if (!parent_buf) {
 315                 struct buffer_head *child;
 316                 u64 blocknr = bh_blocknr(mid_buf);
 317
 318                 if (btrfs_header_nritems(&mid->header) != 1)
 319                         return 0;
 320
 321                 /* promote the child to a root */
 322                 child = read_node_slot(root, mid_buf, 0);
 323                 BUG_ON(!child);
 324                 root->node = child;
 325                 path->nodes[level] = NULL;
 326                 clean_tree_block(trans, root, mid_buf);
 327                 wait_on_buffer(mid_buf);
 328                 /* once for the path */
 329                 btrfs_block_release(root, mid_buf);
 330                 /* once for the root ptr */
 331                 btrfs_block_release(root, mid_buf);
 332                 return btrfs_free_extent(trans, root, blocknr, 1, 1);
 333         }
 334         parent = btrfs_buffer_node(parent_buf);
 335
 336         if (btrfs_header_nritems(&mid->header) >
 337             BTRFS_NODEPTRS_PER_BLOCK(root) / 4)
 338                 return 0;
 339
 340         left_buf = read_node_slot(root, parent_buf, pslot - 1);
 341         right_buf = read_node_slot(root, parent_buf, pslot + 1);
 342
 343         /* first, try to make some room in the middle buffer */
 344         if (left_buf) {
 345                 btrfs_cow_block(trans, root, left_buf, parent_buf, pslot - 1,
 346                                 &left_buf);
 347                 left = btrfs_buffer_node(left_buf);
 348                 orig_slot += btrfs_header_nritems(&left->header);
 349                 wret = push_node_left(trans, root, left_buf, mid_buf);
 350                 if (wret < 0)
 351                         ret = wret;
 352         }
 353
 354         /*
 355          * then try to empty the right most buffer into the middle
 356          */
 357         if (right_buf) {
 358                 btrfs_cow_block(trans, root, right_buf, parent_buf, pslot + 1,
 359                                 &right_buf);
 360                 right = btrfs_buffer_node(right_buf);
 361                 wret = push_node_left(trans, root, mid_buf, right_buf);
 362                 if (wret < 0)
 363                         ret = wret;
 364                 if (btrfs_header_nritems(&right->header) == 0) {
 365                         u64 blocknr = bh_blocknr(right_buf);
 366                         clean_tree_block(trans, root, right_buf);
 367                         wait_on_buffer(right_buf);
 368                         btrfs_block_release(root, right_buf);
 369                         right_buf = NULL;
 370                         right = NULL;
 371                         wret = del_ptr(trans, root, path, level + 1, pslot +
 372                                        1);
 373                         if (wret)
 374                                 ret = wret;
 375                         wret = btrfs_free_extent(trans, root, blocknr, 1, 1);
 376                         if (wret)
 377                                 ret = wret;
 378                 } else {
 379                         btrfs_memcpy(root, parent,
 380                                      &parent->ptrs[pslot + 1].key,
 381                                      &right->ptrs[0].key,
 382                                      sizeof(struct btrfs_disk_key));
 383                         btrfs_mark_buffer_dirty(parent_buf);
 384                 }
 385         }
 386         if (btrfs_header_nritems(&mid->header) == 1) {
 387                 /*
 388                  * we're not allowed to leave a node with one item in the
 389                  * tree during a delete.  A deletion from lower in the tree
 390                  * could try to delete the only pointer in this node.
 391                  * So, pull some keys from the left.
 392                  * There has to be a left pointer at this point because
 393                  * otherwise we would have pulled some pointers from the
 394                  * right
 395                  */
 396                 BUG_ON(!left_buf);
 397                 wret = balance_node_right(trans, root, mid_buf, left_buf);
 398                 if (wret < 0)
 399                         ret = wret;
 400                 BUG_ON(wret == 1);
 401         }
 402         if (btrfs_header_nritems(&mid->header) == 0) {
 403                 /* we've managed to empty the middle node, drop it */
 404                 u64 blocknr = bh_blocknr(mid_buf);
 405                 clean_tree_block(trans, root, mid_buf);
 406                 wait_on_buffer(mid_buf);
 407                 btrfs_block_release(root, mid_buf);
 408                 mid_buf = NULL;
 409                 mid = NULL;
 410                 wret = del_ptr(trans, root, path, level + 1, pslot);
 411                 if (wret)
 412                         ret = wret;
 413                 wret = btrfs_free_extent(trans, root, blocknr, 1, 1);
 414                 if (wret)
 415                         ret = wret;
 416         } else {
 417                 /* update the parent key to reflect our changes */
 418                 btrfs_memcpy(root, parent,
 419                              &parent->ptrs[pslot].key, &mid->ptrs[0].key,
 420                              sizeof(struct btrfs_disk_key));
 421                 btrfs_mark_buffer_dirty(parent_buf);
 422         }
 423
 424         /* update the path */
 425         if (left_buf) {
 426                 if (btrfs_header_nritems(&left->header) > orig_slot) {
 427                         get_bh(left_buf);
 428                         path->nodes[level] = left_buf;
 429                         path->slots[level + 1] -= 1;
 430                         path->slots[level] = orig_slot;
 431                         if (mid_buf)
 432                                 btrfs_block_release(root, mid_buf);
 433                 } else {
 434                         orig_slot -= btrfs_header_nritems(&left->header);
 435                         path->slots[level] = orig_slot;
 436                 }
 437         }
 438         /* double check we haven't messed things up */
 439         check_block(root, path, level);
 440         if (orig_ptr !=
 441             btrfs_node_blockptr(btrfs_buffer_node(path->nodes[level]),
 442                                 path->slots[level]))
 443                 BUG();
 444
 445         if (right_buf)
 446                 btrfs_block_release(root, right_buf);
 447         if (left_buf)
 448                 btrfs_block_release(root, left_buf);
 449         return ret;
 450 }
 451
 452 /* returns zero if the push worked, non-zero otherwise */
 453 static int push_nodes_for_insert(struct btrfs_trans_handle *trans,
 454                                 struct btrfs_root *root,
 455                                 struct btrfs_path *path, int level)
 456 {
 457         struct buffer_head *right_buf;
 458         struct buffer_head *mid_buf;
 459         struct buffer_head *left_buf;
 460         struct buffer_head *parent_buf = NULL;
 461         struct btrfs_node *right = NULL;
 462         struct btrfs_node *mid;
 463         struct btrfs_node *left = NULL;
 464         struct btrfs_node *parent = NULL;
 465         int ret = 0;
 466         int wret;
 467         int pslot;
 468         int orig_slot = path->slots[level];
 469         u64 orig_ptr;
 470
 471         if (level == 0)
 472                 return 1;
 473
 474         mid_buf = path->nodes[level];
 475         mid = btrfs_buffer_node(mid_buf);
 476         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 477
 478         if (level < BTRFS_MAX_LEVEL - 1)
 479                 parent_buf = path->nodes[level + 1];
 480         pslot = path->slots[level + 1];
 481
 482         if (!parent_buf)
 483                 return 1;
 484         parent = btrfs_buffer_node(parent_buf);
 485
 486         left_buf = read_node_slot(root, parent_buf, pslot - 1);
 487
 488         /* first, try to make some room in the middle buffer */
 489         if (left_buf) {
 490                 u32 left_nr;
 491                 left = btrfs_buffer_node(left_buf);
 492                 left_nr = btrfs_header_nritems(&left->header);
 493                 if (left_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
 494                         wret = 1;
 495                 } else {
 496                         btrfs_cow_block(trans, root, left_buf, parent_buf,
 497                                         pslot - 1, &left_buf);
 498                         left = btrfs_buffer_node(left_buf);
 499                         wret = push_node_left(trans, root, left_buf, mid_buf);
 500                 }
 501                 if (wret < 0)
 502                         ret = wret;
 503                 if (wret == 0) {
 504                         orig_slot += left_nr;
 505                         btrfs_memcpy(root, parent,
 506                                      &parent->ptrs[pslot].key,
 507                                      &mid->ptrs[0].key,
 508                                      sizeof(struct btrfs_disk_key));
 509                         btrfs_mark_buffer_dirty(parent_buf);
 510                         if (btrfs_header_nritems(&left->header) > orig_slot) {
 511                                 path->nodes[level] = left_buf;
 512                                 path->slots[level + 1] -= 1;
 513                                 path->slots[level] = orig_slot;
 514                                 btrfs_block_release(root, mid_buf);
 515                         } else {
 516                                 orig_slot -=
 517                                         btrfs_header_nritems(&left->header);
 518                                 path->slots[level] = orig_slot;
 519                                 btrfs_block_release(root, left_buf);
 520                         }
 521                         check_node(root, path, level);
 522                         return 0;
 523                 }
 524                 btrfs_block_release(root, left_buf);
 525         }
 526         right_buf = read_node_slot(root, parent_buf, pslot + 1);
 527
 528         /*
 529          * then try to empty the right most buffer into the middle
 530          */
 531         if (right_buf) {
 532                 u32 right_nr;
 533                 right = btrfs_buffer_node(right_buf);
 534                 right_nr = btrfs_header_nritems(&right->header);
 535                 if (right_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
 536                         wret = 1;
 537                 } else {
 538                         btrfs_cow_block(trans, root, right_buf,
 539                                         parent_buf, pslot + 1, &right_buf);
 540                         right = btrfs_buffer_node(right_buf);
 541                         wret = balance_node_right(trans, root,
 542                                                   right_buf, mid_buf);
 543                 }
 544                 if (wret < 0)
 545                         ret = wret;
 546                 if (wret == 0) {
 547                         btrfs_memcpy(root, parent,
 548                                      &parent->ptrs[pslot + 1].key,
 549                                      &right->ptrs[0].key,
 550                                      sizeof(struct btrfs_disk_key));
 551                         btrfs_mark_buffer_dirty(parent_buf);
 552                         if (btrfs_header_nritems(&mid->header) <= orig_slot) {
 553                                 path->nodes[level] = right_buf;
 554                                 path->slots[level + 1] += 1;
 555                                 path->slots[level] = orig_slot -
 556                                         btrfs_header_nritems(&mid->header);
 557                                 btrfs_block_release(root, mid_buf);
 558                         } else {
 559                                 btrfs_block_release(root, right_buf);
 560                         }
 561                         check_node(root, path, level);
 562                         return 0;
 563                 }
 564                 btrfs_block_release(root, right_buf);
 565         }
 566         check_node(root, path, level);
 567         return 1;
 568 }
 569
 570 /*
 571  * look for key in the tree.  path is filled in with nodes along the way
 572  * if key is found, we return zero and you can find the item in the leaf
 573  * level of the path (level 0)
 574  *
 575  * If the key isn't found, the path points to the slot where it should
 576  * be inserted, and 1 is returned.  If there are other errors during the
 577  * search a negative error number is returned.
 578  *
 579  * if ins_len > 0, nodes and leaves will be split as we walk down the
 580  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
 581  * possible)
 582  */
 583 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
 584                       *root, struct btrfs_key *key, struct btrfs_path *p, int
 585                       ins_len, int cow)
 586 {
 587         struct buffer_head *b;
 588         struct buffer_head *cow_buf;
 589         struct btrfs_node *c;
 590         int slot;
 591         int ret;
 592         int level;
 593
 594         WARN_ON(p->nodes[0] != NULL);
 595         WARN_ON(!mutex_is_locked(&root->fs_info->fs_mutex));
 596 again:
 597         b = root->node;
 598         get_bh(b);
 599         while (b) {
 600                 c = btrfs_buffer_node(b);
 601                 level = btrfs_header_level(&c->header);
 602                 if (cow) {
 603                         int wret;
 604                         wret = btrfs_cow_block(trans, root, b,
 605                                                p->nodes[level + 1],
 606                                                p->slots[level + 1],
 607                                                &cow_buf);
 608                         b = cow_buf;
 609                         c = btrfs_buffer_node(b);
 610                 }
 611                 BUG_ON(!cow && ins_len);
 612                 if (level != btrfs_header_level(&c->header))
 613                         WARN_ON(1);
 614                 level = btrfs_header_level(&c->header);
 615                 p->nodes[level] = b;
 616                 ret = check_block(root, p, level);
 617                 if (ret)
 618                         return -1;
 619                 ret = bin_search(c, key, &slot);
 620                 if (!btrfs_is_leaf(c)) {
 621                         if (ret && slot > 0)
 622                                 slot -= 1;
 623                         p->slots[level] = slot;
 624                         if (ins_len > 0 && btrfs_header_nritems(&c->header) >=
 625                             BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
 626                                 int sret = split_node(trans, root, p, level);
 627                                 BUG_ON(sret > 0);
 628                                 if (sret)
 629                                         return sret;
 630                                 b = p->nodes[level];
 631                                 c = btrfs_buffer_node(b);
 632                                 slot = p->slots[level];
 633                         } else if (ins_len < 0) {
 634                                 int sret = balance_level(trans, root, p,
 635                                                          level);
 636                                 if (sret)
 637                                         return sret;
 638                                 b = p->nodes[level];
 639                                 if (!b)
 640                                         goto again;
 641                                 c = btrfs_buffer_node(b);
 642                                 slot = p->slots[level];
 643                                 BUG_ON(btrfs_header_nritems(&c->header) == 1);
 644                         }
 645                         b = read_tree_block(root, btrfs_node_blockptr(c, slot));
 646                 } else {
 647                         struct btrfs_leaf *l = (struct btrfs_leaf *)c;
 648                         p->slots[level] = slot;
 649                         if (ins_len > 0 && btrfs_leaf_free_space(root, l) <
 650                             sizeof(struct btrfs_item) + ins_len) {
 651                                 int sret = split_leaf(trans, root, key,
 652                                                       p, ins_len);
 653                                 BUG_ON(sret > 0);
 654                                 if (sret)
 655                                         return sret;
 656                         }
 657                         return ret;
 658                 }
 659         }
 660         return 1;
 661 }
 662
 663 /*
 664  * adjust the pointers going up the tree, starting at level
 665  * making sure the right key of each node is points to 'key'.
 666  * This is used after shifting pointers to the left, so it stops
 667  * fixing up pointers when a given leaf/node is not in slot 0 of the
 668  * higher levels
 669  *
 670  * If this fails to write a tree block, it returns -1, but continues
 671  * fixing up the blocks in ram so the tree is consistent.
 672  */
 673 static int fixup_low_keys(struct btrfs_trans_handle *trans, struct btrfs_root
 674                           *root, struct btrfs_path *path, struct btrfs_disk_key
 675                           *key, int level)
 676 {
 677         int i;
 678         int ret = 0;
 679         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
 680                 struct btrfs_node *t;
 681                 int tslot = path->slots[i];
 682                 if (!path->nodes[i])
 683                         break;
 684                 t = btrfs_buffer_node(path->nodes[i]);
 685                 btrfs_memcpy(root, t, &t->ptrs[tslot].key, key, sizeof(*key));
 686                 btrfs_mark_buffer_dirty(path->nodes[i]);
 687                 if (tslot != 0)
 688                         break;
 689         }
 690         return ret;
 691 }
 692
 693 /*
 694  * try to push data from one node into the next node left in the
 695  * tree.
 696  *
 697  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
 698  * error, and > 0 if there was no room in the left hand block.
 699  */
 700 static int push_node_left(struct btrfs_trans_handle *trans, struct btrfs_root
 701                           *root, struct buffer_head *dst_buf, struct
 702                           buffer_head *src_buf)
 703 {
 704         struct btrfs_node *src = btrfs_buffer_node(src_buf);
 705         struct btrfs_node *dst = btrfs_buffer_node(dst_buf);
 706         int push_items = 0;
 707         int src_nritems;
 708         int dst_nritems;
 709         int ret = 0;
 710
 711         src_nritems = btrfs_header_nritems(&src->header);
 712         dst_nritems = btrfs_header_nritems(&dst->header);
 713         push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
 714         if (push_items <= 0) {
 715                 return 1;
 716         }
 717
 718         if (src_nritems < push_items)
 719                 push_items = src_nritems;
 720
 721         btrfs_memcpy(root, dst, dst->ptrs + dst_nritems, src->ptrs,
 722                      push_items * sizeof(struct btrfs_key_ptr));
 723         if (push_items < src_nritems) {
 724                 btrfs_memmove(root, src, src->ptrs, src->ptrs + push_items,
 725                         (src_nritems - push_items) *
 726                         sizeof(struct btrfs_key_ptr));
 727         }
 728         btrfs_set_header_nritems(&src->header, src_nritems - push_items);
 729         btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 730         btrfs_mark_buffer_dirty(src_buf);
 731         btrfs_mark_buffer_dirty(dst_buf);
 732         return ret;
 733 }
 734
 735 /*
 736  * try to push data from one node into the next node right in the
 737  * tree.
 738  *
 739  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
 740  * error, and > 0 if there was no room in the right hand block.
 741  *
 742  * this will  only push up to 1/2 the contents of the left node over
 743  */
 744 static int balance_node_right(struct btrfs_trans_handle *trans, struct
 745                               btrfs_root *root, struct buffer_head *dst_buf,
 746                               struct buffer_head *src_buf)
 747 {
 748         struct btrfs_node *src = btrfs_buffer_node(src_buf);
 749         struct btrfs_node *dst = btrfs_buffer_node(dst_buf);
 750         int push_items = 0;
 751         int max_push;
 752         int src_nritems;
 753         int dst_nritems;
 754         int ret = 0;
 755
 756         src_nritems = btrfs_header_nritems(&src->header);
 757         dst_nritems = btrfs_header_nritems(&dst->header);
 758         push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
 759         if (push_items <= 0) {
 760                 return 1;
 761         }
 762
 763         max_push = src_nritems / 2 + 1;
 764         /* don't try to empty the node */
 765         if (max_push > src_nritems)
 766                 return 1;
 767         if (max_push < push_items)
 768                 push_items = max_push;
 769
 770         btrfs_memmove(root, dst, dst->ptrs + push_items, dst->ptrs,
 771                       dst_nritems * sizeof(struct btrfs_key_ptr));
 772
 773         btrfs_memcpy(root, dst, dst->ptrs,
 774                      src->ptrs + src_nritems - push_items,
 775                      push_items * sizeof(struct btrfs_key_ptr));
 776
 777         btrfs_set_header_nritems(&src->header, src_nritems - push_items);
 778         btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 779
 780         btrfs_mark_buffer_dirty(src_buf);
 781         btrfs_mark_buffer_dirty(dst_buf);
 782         return ret;
 783 }
 784
 785 /*
 786  * helper function to insert a new root level in the tree.
 787  * A new node is allocated, and a single item is inserted to
 788  * point to the existing root
 789  *
 790  * returns zero on success or < 0 on failure.
 791  */
 792 static int insert_new_root(struct btrfs_trans_handle *trans, struct btrfs_root
 793                            *root, struct btrfs_path *path, int level)
 794 {
 795         struct buffer_head *t;
 796         struct btrfs_node *lower;
 797         struct btrfs_node *c;
 798         struct btrfs_disk_key *lower_key;
 799
 800         BUG_ON(path->nodes[level]);
 801         BUG_ON(path->nodes[level-1] != root->node);
 802
 803         t = btrfs_alloc_free_block(trans, root, root->node->b_blocknr);
 804         c = btrfs_buffer_node(t);
 805         memset(c, 0, root->blocksize);
 806         btrfs_set_header_nritems(&c->header, 1);
 807         btrfs_set_header_level(&c->header, level);
 808         btrfs_set_header_blocknr(&c->header, bh_blocknr(t));
 809         btrfs_set_header_generation(&c->header, trans->transid);
 810         btrfs_set_header_owner(&c->header, root->root_key.objectid);
 811         lower = btrfs_buffer_node(path->nodes[level-1]);
 812         memcpy(c->header.fsid, root->fs_info->disk_super->fsid,
 813                sizeof(c->header.fsid));
 814         if (btrfs_is_leaf(lower))
 815                 lower_key = &((struct btrfs_leaf *)lower)->items[0].key;
 816         else
 817                 lower_key = &lower->ptrs[0].key;
 818         btrfs_memcpy(root, c, &c->ptrs[0].key, lower_key,
 819                      sizeof(struct btrfs_disk_key));
 820         btrfs_set_node_blockptr(c, 0, bh_blocknr(path->nodes[level - 1]));
 821
 822         btrfs_mark_buffer_dirty(t);
 823
 824         /* the super has an extra ref to root->node */
 825         btrfs_block_release(root, root->node);
 826         root->node = t;
 827         get_bh(t);
 828         path->nodes[level] = t;
 829         path->slots[level] = 0;
 830         return 0;
 831 }
 832
 833 /*
 834  * worker function to insert a single pointer in a node.
 835  * the node should have enough room for the pointer already
 836  *
 837  * slot and level indicate where you want the key to go, and
 838  * blocknr is the block the key points to.
 839  *
 840  * returns zero on success and < 0 on any error
 841  */
 842 static int insert_ptr(struct btrfs_trans_handle *trans, struct btrfs_root
 843                       *root, struct btrfs_path *path, struct btrfs_disk_key
 844                       *key, u64 blocknr, int slot, int level)
 845 {
 846         struct btrfs_node *lower;
 847         int nritems;
 848
 849         BUG_ON(!path->nodes[level]);
 850         lower = btrfs_buffer_node(path->nodes[level]);
 851         nritems = btrfs_header_nritems(&lower->header);
 852         if (slot > nritems)
 853                 BUG();
 854         if (nritems == BTRFS_NODEPTRS_PER_BLOCK(root))
 855                 BUG();
 856         if (slot != nritems) {
 857                 btrfs_memmove(root, lower, lower->ptrs + slot + 1,
 858                               lower->ptrs + slot,
 859                               (nritems - slot) * sizeof(struct btrfs_key_ptr));
 860         }
 861         btrfs_memcpy(root, lower, &lower->ptrs[slot].key,
 862                      key, sizeof(struct btrfs_disk_key));
 863         btrfs_set_node_blockptr(lower, slot, blocknr);
 864         btrfs_set_header_nritems(&lower->header, nritems + 1);
 865         btrfs_mark_buffer_dirty(path->nodes[level]);
 866         return 0;
 867 }
 868
 869 /*
 870  * split the node at the specified level in path in two.
 871  * The path is corrected to point to the appropriate node after the split
 872  *
 873  * Before splitting this tries to make some room in the node by pushing
 874  * left and right, if either one works, it returns right away.
 875  *
 876  * returns 0 on success and < 0 on failure
 877  */
 878 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
 879                       *root, struct btrfs_path *path, int level)
 880 {
 881         struct buffer_head *t;
 882         struct btrfs_node *c;
 883         struct buffer_head *split_buffer;
 884         struct btrfs_node *split;
 885         int mid;
 886         int ret;
 887         int wret;
 888         u32 c_nritems;
 889
 890         t = path->nodes[level];
 891         c = btrfs_buffer_node(t);
 892         if (t == root->node) {
 893                 /* trying to split the root, lets make a new one */
 894                 ret = insert_new_root(trans, root, path, level + 1);
 895                 if (ret)
 896                         return ret;
 897         } else {
 898                 ret = push_nodes_for_insert(trans, root, path, level);
 899                 t = path->nodes[level];
 900                 c = btrfs_buffer_node(t);
 901                 if (!ret &&
 902                     btrfs_header_nritems(&c->header) <
 903                     BTRFS_NODEPTRS_PER_BLOCK(root) - 1)
 904                         return 0;
 905         }
 906
 907         c_nritems = btrfs_header_nritems(&c->header);
 908         split_buffer = btrfs_alloc_free_block(trans, root, t->b_blocknr);
 909         split = btrfs_buffer_node(split_buffer);
 910         btrfs_set_header_flags(&split->header, btrfs_header_flags(&c->header));
 911         btrfs_set_header_level(&split->header, btrfs_header_level(&c->header));
 912         btrfs_set_header_blocknr(&split->header, bh_blocknr(split_buffer));
 913         btrfs_set_header_generation(&split->header, trans->transid);
 914         btrfs_set_header_owner(&split->header, root->root_key.objectid);
 915         memcpy(split->header.fsid, root->fs_info->disk_super->fsid,
 916                sizeof(split->header.fsid));
 917         mid = (c_nritems + 1) / 2;
 918         btrfs_memcpy(root, split, split->ptrs, c->ptrs + mid,
 919                      (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
 920         btrfs_set_header_nritems(&split->header, c_nritems - mid);
 921         btrfs_set_header_nritems(&c->header, mid);
 922         ret = 0;
 923
 924         btrfs_mark_buffer_dirty(t);
 925         btrfs_mark_buffer_dirty(split_buffer);
 926         wret = insert_ptr(trans, root, path, &split->ptrs[0].key,
 927                           bh_blocknr(split_buffer), path->slots[level + 1] + 1,
 928                           level + 1);
 929         if (wret)
 930                 ret = wret;
 931
 932         if (path->slots[level] >= mid) {
 933                 path->slots[level] -= mid;
 934                 btrfs_block_release(root, t);
 935                 path->nodes[level] = split_buffer;
 936                 path->slots[level + 1] += 1;
 937         } else {
 938                 btrfs_block_release(root, split_buffer);
 939         }
 940         return ret;
 941 }
 942
 943 /*
 944  * how many bytes are required to store the items in a leaf.  start
 945  * and nr indicate which items in the leaf to check.  This totals up the
 946  * space used both by the item structs and the item data
 947  */
 948 static int leaf_space_used(struct btrfs_leaf *l, int start, int nr)
 949 {
 950         int data_len;
 951         int nritems = btrfs_header_nritems(&l->header);
 952         int end = min(nritems, start + nr) - 1;
 953
 954         if (!nr)
 955                 return 0;
 956         data_len = btrfs_item_end(l->items + start);
 957         data_len = data_len - btrfs_item_offset(l->items + end);
 958         data_len += sizeof(struct btrfs_item) * nr;
 959         WARN_ON(data_len < 0);
 960         return data_len;
 961 }
 962
 963 /*
 964  * The space between the end of the leaf items and
 965  * the start of the leaf data.  IOW, how much room
 966  * the leaf has left for both items and data
 967  */
 968 int btrfs_leaf_free_space(struct btrfs_root *root, struct btrfs_leaf *leaf)
 969 {
 970         int nritems = btrfs_header_nritems(&leaf->header);
 971         return BTRFS_LEAF_DATA_SIZE(root) - leaf_space_used(leaf, 0, nritems);
 972 }
 973
 974 /*
 975  * push some data in the path leaf to the right, trying to free up at
 976  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 977  *
 978  * returns 1 if the push failed because the other node didn't have enough
 979  * room, 0 if everything worked out and < 0 if there were major errors.
 980  */
 981 static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 982                            *root, struct btrfs_path *path, int data_size)
 983 {
 984         struct buffer_head *left_buf = path->nodes[0];
 985         struct btrfs_leaf *left = btrfs_buffer_leaf(left_buf);
 986         struct btrfs_leaf *right;
 987         struct buffer_head *right_buf;
 988         struct buffer_head *upper;
 989         struct btrfs_node *upper_node;
 990         int slot;
 991         int i;
 992         int free_space;
 993         int push_space = 0;
 994         int push_items = 0;
 995         struct btrfs_item *item;
 996         u32 left_nritems;
 997         u32 right_nritems;
 998
 999         slot = path->slots[1];
1000         if (!path->nodes[1]) {
1001                 return 1;
1002         }
1003         upper = path->nodes[1];
1004         upper_node = btrfs_buffer_node(upper);
1005         if (slot >= btrfs_header_nritems(&upper_node->header) - 1) {
1006                 return 1;
1007         }
1008         right_buf = read_tree_block(root,
1009                     btrfs_node_blockptr(btrfs_buffer_node(upper), slot + 1));
1010         right = btrfs_buffer_leaf(right_buf);
1011         free_space = btrfs_leaf_free_space(root, right);
1012         if (free_space < data_size + sizeof(struct btrfs_item)) {
1013                 btrfs_block_release(root, right_buf);
1014                 return 1;
1015         }
1016         /* cow and double check */
1017         btrfs_cow_block(trans, root, right_buf, upper, slot + 1, &right_buf);
1018         right = btrfs_buffer_leaf(right_buf);
1019         free_space = btrfs_leaf_free_space(root, right);
1020         if (free_space < data_size + sizeof(struct btrfs_item)) {
1021                 btrfs_block_release(root, right_buf);
1022                 return 1;
1023         }
1024
1025         left_nritems = btrfs_header_nritems(&left->header);
1026         if (left_nritems == 0) {
1027                 btrfs_block_release(root, right_buf);
1028                 return 1;
1029         }
1030         for (i = left_nritems - 1; i >= 1; i--) {
1031                 item = left->items + i;
1032                 if (path->slots[0] == i)
1033                         push_space += data_size + sizeof(*item);
1034                 if (btrfs_item_size(item) + sizeof(*item) + push_space >
1035                     free_space)
1036                         break;
1037                 push_items++;
1038                 push_space += btrfs_item_size(item) + sizeof(*item);
1039         }
1040         if (push_items == 0) {
1041                 btrfs_block_release(root, right_buf);
1042                 return 1;
1043         }
1044         if (push_items == left_nritems)
1045                 WARN_ON(1);
1046         right_nritems = btrfs_header_nritems(&right->header);
1047         /* push left to right */
1048         push_space = btrfs_item_end(left->items + left_nritems - push_items);
1049         push_space -= leaf_data_end(root, left);
1050         /* make room in the right data area */
1051         btrfs_memmove(root, right, btrfs_leaf_data(right) +
1052                       leaf_data_end(root, right) - push_space,
1053                       btrfs_leaf_data(right) +
1054                       leaf_data_end(root, right), BTRFS_LEAF_DATA_SIZE(root) -
1055                       leaf_data_end(root, right));
1056         /* copy from the left data area */
1057         btrfs_memcpy(root, right, btrfs_leaf_data(right) +
1058                      BTRFS_LEAF_DATA_SIZE(root) - push_space,
1059                      btrfs_leaf_data(left) + leaf_data_end(root, left),
1060                      push_space);
1061         btrfs_memmove(root, right, right->items + push_items, right->items,
1062                 right_nritems * sizeof(struct btrfs_item));
1063         /* copy the items from left to right */
1064         btrfs_memcpy(root, right, right->items, left->items +
1065                      left_nritems - push_items,
1066                      push_items * sizeof(struct btrfs_item));
1067
1068         /* update the item pointers */
1069         right_nritems += push_items;
1070         btrfs_set_header_nritems(&right->header, right_nritems);
1071         push_space = BTRFS_LEAF_DATA_SIZE(root);
1072         for (i = 0; i < right_nritems; i++) {
1073                 btrfs_set_item_offset(right->items + i, push_space -
1074                                       btrfs_item_size(right->items + i));
1075                 push_space = btrfs_item_offset(right->items + i);
1076         }
1077         left_nritems -= push_items;
1078         btrfs_set_header_nritems(&left->header, left_nritems);
1079
1080         btrfs_mark_buffer_dirty(left_buf);
1081         btrfs_mark_buffer_dirty(right_buf);
1082
1083         btrfs_memcpy(root, upper_node, &upper_node->ptrs[slot + 1].key,
1084                 &right->items[0].key, sizeof(struct btrfs_disk_key));
1085         btrfs_mark_buffer_dirty(upper);
1086
1087         /* then fixup the leaf pointer in the path */
1088         if (path->slots[0] >= left_nritems) {
1089                 path->slots[0] -= left_nritems;
1090                 btrfs_block_release(root, path->nodes[0]);
1091                 path->nodes[0] = right_buf;
1092                 path->slots[1] += 1;
1093         } else {
1094                 btrfs_block_release(root, right_buf);
1095         }
1096         return 0;
1097 }
1098 /*
1099  * push some data in the path leaf to the left, trying to free up at
1100  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
1101  */
1102 static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
1103                           *root, struct btrfs_path *path, int data_size)
1104 {
1105         struct buffer_head *right_buf = path->nodes[0];
1106         struct btrfs_leaf *right = btrfs_buffer_leaf(right_buf);
1107         struct buffer_head *t;
1108         struct btrfs_leaf *left;
1109         int slot;
1110         int i;
1111         int free_space;
1112         int push_space = 0;
1113         int push_items = 0;
1114         struct btrfs_item *item;
1115         u32 old_left_nritems;
1116         int ret = 0;
1117         int wret;
1118
1119         slot = path->slots[1];
1120         if (slot == 0) {
1121                 return 1;
1122         }
1123         if (!path->nodes[1]) {
1124                 return 1;
1125         }
1126         t = read_tree_block(root,
1127             btrfs_node_blockptr(btrfs_buffer_node(path->nodes[1]), slot - 1));
1128         left = btrfs_buffer_leaf(t);
1129         free_space = btrfs_leaf_free_space(root, left);
1130         if (free_space < data_size + sizeof(struct btrfs_item)) {
1131                 btrfs_block_release(root, t);
1132                 return 1;
1133         }
1134
1135         /* cow and double check */
1136         btrfs_cow_block(trans, root, t, path->nodes[1], slot - 1, &t);
1137         left = btrfs_buffer_leaf(t);
1138         free_space = btrfs_leaf_free_space(root, left);
1139         if (free_space < data_size + sizeof(struct btrfs_item)) {
1140                 btrfs_block_release(root, t);
1141                 return 1;
1142         }
1143
1144         if (btrfs_header_nritems(&right->header) == 0) {
1145                 btrfs_block_release(root, t);
1146                 return 1;
1147         }
1148
1149         for (i = 0; i < btrfs_header_nritems(&right->header) - 1; i++) {
1150                 item = right->items + i;
1151                 if (path->slots[0] == i)
1152                         push_space += data_size + sizeof(*item);
1153                 if (btrfs_item_size(item) + sizeof(*item) + push_space >
1154                     free_space)
1155                         break;
1156                 push_items++;
1157                 push_space += btrfs_item_size(item) + sizeof(*item);
1158         }
1159         if (push_items == 0) {
1160                 btrfs_block_release(root, t);
1161                 return 1;
1162         }
1163         if (push_items == btrfs_header_nritems(&right->header))
1164                 WARN_ON(1);
1165         /* push data from right to left */
1166         btrfs_memcpy(root, left, left->items +
1167                      btrfs_header_nritems(&left->header),
1168                      right->items, push_items * sizeof(struct btrfs_item));
1169         push_space = BTRFS_LEAF_DATA_SIZE(root) -
1170                      btrfs_item_offset(right->items + push_items -1);
1171         btrfs_memcpy(root, left, btrfs_leaf_data(left) +
1172                      leaf_data_end(root, left) - push_space,
1173                      btrfs_leaf_data(right) +
1174                      btrfs_item_offset(right->items + push_items - 1),
1175                      push_space);
1176         old_left_nritems = btrfs_header_nritems(&left->header);
1177         BUG_ON(old_left_nritems < 0);
1178
1179         for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
1180                 u32 ioff = btrfs_item_offset(left->items + i);
1181                 btrfs_set_item_offset(left->items + i, ioff -
1182                                      (BTRFS_LEAF_DATA_SIZE(root) -
1183                                       btrfs_item_offset(left->items +
1184                                                         old_left_nritems - 1)));
1185         }
1186         btrfs_set_header_nritems(&left->header, old_left_nritems + push_items);
1187
1188         /* fixup right node */
1189         push_space = btrfs_item_offset(right->items + push_items - 1) -
1190                      leaf_data_end(root, right);
1191         btrfs_memmove(root, right, btrfs_leaf_data(right) +
1192                       BTRFS_LEAF_DATA_SIZE(root) - push_space,
1193                       btrfs_leaf_data(right) +
1194                       leaf_data_end(root, right), push_space);
1195         btrfs_memmove(root, right, right->items, right->items + push_items,
1196                 (btrfs_header_nritems(&right->header) - push_items) *
1197                 sizeof(struct btrfs_item));
1198         btrfs_set_header_nritems(&right->header,
1199                                  btrfs_header_nritems(&right->header) -
1200                                  push_items);
1201         push_space = BTRFS_LEAF_DATA_SIZE(root);
1202
1203         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
1204                 btrfs_set_item_offset(right->items + i, push_space -
1205                                       btrfs_item_size(right->items + i));
1206                 push_space = btrfs_item_offset(right->items + i);
1207         }
1208
1209         btrfs_mark_buffer_dirty(t);
1210         btrfs_mark_buffer_dirty(right_buf);
1211         wret = fixup_low_keys(trans, root, path, &right->items[0].key, 1);
1212         if (wret)
1213                 ret = wret;
1214
1215         /* then fixup the leaf pointer in the path */
1216         if (path->slots[0] < push_items) {
1217                 path->slots[0] += old_left_nritems;
1218                 btrfs_block_release(root, path->nodes[0]);
1219                 path->nodes[0] = t;
1220                 path->slots[1] -= 1;
1221         } else {
1222                 btrfs_block_release(root, t);
1223                 path->slots[0] -= push_items;
1224         }
1225         BUG_ON(path->slots[0] < 0);
1226         return ret;
1227 }
1228
1229 /*
1230  * split the path's leaf in two, making sure there is at least data_size
1231  * available for the resulting leaf level of the path.
1232  *
1233  * returns 0 if all went well and < 0 on failure.
1234  */
1235 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
1236                       *root, struct btrfs_key *ins_key,
1237                       struct btrfs_path *path, int data_size)
1238 {
1239         struct buffer_head *l_buf;
1240         struct btrfs_leaf *l;
1241         u32 nritems;
1242         int mid;
1243         int slot;
1244         struct btrfs_leaf *right;
1245         struct buffer_head *right_buffer;
1246         int space_needed = data_size + sizeof(struct btrfs_item);
1247         int data_copy_size;
1248         int rt_data_off;
1249         int i;
1250         int ret = 0;
1251         int wret;
1252         int double_split = 0;
1253         struct btrfs_disk_key disk_key;
1254
1255         /* first try to make some room by pushing left and right */
1256         wret = push_leaf_left(trans, root, path, data_size);
1257         if (wret < 0)
1258                 return wret;
1259         if (wret) {
1260                 wret = push_leaf_right(trans, root, path, data_size);
1261                 if (wret < 0)
1262                         return wret;
1263         }
1264         l_buf = path->nodes[0];
1265         l = btrfs_buffer_leaf(l_buf);
1266
1267         /* did the pushes work? */
1268         if (btrfs_leaf_free_space(root, l) >=
1269             sizeof(struct btrfs_item) + data_size)
1270                 return 0;
1271
1272         if (!path->nodes[1]) {
1273                 ret = insert_new_root(trans, root, path, 1);
1274                 if (ret)
1275                         return ret;
1276         }
1277         slot = path->slots[0];
1278         nritems = btrfs_header_nritems(&l->header);
1279         mid = (nritems + 1)/ 2;
1280         right_buffer = btrfs_alloc_free_block(trans, root, l_buf->b_blocknr);
1281         BUG_ON(!right_buffer);
1282         right = btrfs_buffer_leaf(right_buffer);
1283         memset(&right->header, 0, sizeof(right->header));
1284         btrfs_set_header_blocknr(&right->header, bh_blocknr(right_buffer));
1285         btrfs_set_header_generation(&right->header, trans->transid);
1286         btrfs_set_header_owner(&right->header, root->root_key.objectid);
1287         btrfs_set_header_level(&right->header, 0);
1288         memcpy(right->header.fsid, root->fs_info->disk_super->fsid,
1289                sizeof(right->header.fsid));
1290         if (mid <= slot) {
1291                 if (nritems == 1 ||
1292                     leaf_space_used(l, mid, nritems - mid) + space_needed >
1293                         BTRFS_LEAF_DATA_SIZE(root)) {
1294                         if (slot >= nritems) {
1295                                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
1296                                 btrfs_set_header_nritems(&right->header, 0);
1297                                 wret = insert_ptr(trans, root, path,
1298                                                   &disk_key,
1299                                                   bh_blocknr(right_buffer),
1300                                                   path->slots[1] + 1, 1);
1301                                 if (wret)
1302                                         ret = wret;
1303                                 btrfs_block_release(root, path->nodes[0]);
1304                                 path->nodes[0] = right_buffer;
1305                                 path->slots[0] = 0;
1306                                 path->slots[1] += 1;
1307                                 return ret;
1308                         }
1309                         mid = slot;
1310                         double_split = 1;
1311                 }
1312         } else {
1313                 if (leaf_space_used(l, 0, mid + 1) + space_needed >
1314                         BTRFS_LEAF_DATA_SIZE(root)) {
1315                         if (slot == 0) {
1316                                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
1317                                 btrfs_set_header_nritems(&right->header, 0);
1318                                 wret = insert_ptr(trans, root, path,
1319                                                   &disk_key,
1320                                                   bh_blocknr(right_buffer),
1321                                                   path->slots[1] - 1, 1);
1322                                 if (wret)
1323                                         ret = wret;
1324                                 btrfs_block_release(root, path->nodes[0]);
1325                                 path->nodes[0] = right_buffer;
1326                                 path->slots[0] = 0;
1327                                 path->slots[1] -= 1;
1328                                 if (path->slots[1] == 0) {
1329                                         wret = fixup_low_keys(trans, root,
1330                                                    path, &disk_key, 1);
1331                                         if (wret)
1332                                                 ret = wret;
1333                                 }
1334                                 return ret;
1335                         }
1336                         mid = slot;
1337                         double_split = 1;
1338                 }
1339         }
1340         btrfs_set_header_nritems(&right->header, nritems - mid);
1341         data_copy_size = btrfs_item_end(l->items + mid) -
1342                          leaf_data_end(root, l);
1343         btrfs_memcpy(root, right, right->items, l->items + mid,
1344                      (nritems - mid) * sizeof(struct btrfs_item));
1345         btrfs_memcpy(root, right,
1346                      btrfs_leaf_data(right) + BTRFS_LEAF_DATA_SIZE(root) -
1347                      data_copy_size, btrfs_leaf_data(l) +
1348                      leaf_data_end(root, l), data_copy_size);
1349         rt_data_off = BTRFS_LEAF_DATA_SIZE(root) -
1350                       btrfs_item_end(l->items + mid);
1351
1352         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
1353                 u32 ioff = btrfs_item_offset(right->items + i);
1354                 btrfs_set_item_offset(right->items + i, ioff + rt_data_off);
1355         }
1356
1357         btrfs_set_header_nritems(&l->header, mid);
1358         ret = 0;
1359         wret = insert_ptr(trans, root, path, &right->items[0].key,
1360                           bh_blocknr(right_buffer), path->slots[1] + 1, 1);
1361         if (wret)
1362                 ret = wret;
1363         btrfs_mark_buffer_dirty(right_buffer);
1364         btrfs_mark_buffer_dirty(l_buf);
1365         BUG_ON(path->slots[0] != slot);
1366         if (mid <= slot) {
1367                 btrfs_block_release(root, path->nodes[0]);
1368                 path->nodes[0] = right_buffer;
1369                 path->slots[0] -= mid;
1370                 path->slots[1] += 1;
1371         } else
1372                 btrfs_block_release(root, right_buffer);
1373         BUG_ON(path->slots[0] < 0);
1374
1375         if (!double_split)
1376                 return ret;
1377         right_buffer = btrfs_alloc_free_block(trans, root, l_buf->b_blocknr);
1378         BUG_ON(!right_buffer);
1379         right = btrfs_buffer_leaf(right_buffer);
1380         memset(&right->header, 0, sizeof(right->header));
1381         btrfs_set_header_blocknr(&right->header, bh_blocknr(right_buffer));
1382         btrfs_set_header_generation(&right->header, trans->transid);
1383         btrfs_set_header_owner(&right->header, root->root_key.objectid);
1384         btrfs_set_header_level(&right->header, 0);
1385         memcpy(right->header.fsid, root->fs_info->disk_super->fsid,
1386                sizeof(right->header.fsid));
1387         btrfs_cpu_key_to_disk(&disk_key, ins_key);
1388         btrfs_set_header_nritems(&right->header, 0);
1389         wret = insert_ptr(trans, root, path,
1390                           &disk_key,
1391                           bh_blocknr(right_buffer),
1392                           path->slots[1], 1);
1393         if (wret)
1394                 ret = wret;
1395         if (path->slots[1] == 0) {
1396                 wret = fixup_low_keys(trans, root, path, &disk_key, 1);
1397                 if (wret)
1398                         ret = wret;
1399         }
1400         btrfs_block_release(root, path->nodes[0]);
1401         path->nodes[0] = right_buffer;
1402         path->slots[0] = 0;
1403         check_node(root, path, 1);
1404         check_leaf(root, path, 0);
1405         return ret;
1406 }
1407
1408 int btrfs_truncate_item(struct btrfs_trans_handle *trans,
1409                         struct btrfs_root *root,
1410                         struct btrfs_path *path,
1411                         u32 new_size)
1412 {
1413         int ret = 0;
1414         int slot;
1415         int slot_orig;
1416         struct btrfs_leaf *leaf;
1417         struct buffer_head *leaf_buf;
1418         u32 nritems;
1419         unsigned int data_end;
1420         unsigned int old_data_start;
1421         unsigned int old_size;
1422         unsigned int size_diff;
1423         int i;
1424
1425         slot_orig = path->slots[0];
1426         leaf_buf = path->nodes[0];
1427         leaf = btrfs_buffer_leaf(leaf_buf);
1428
1429         nritems = btrfs_header_nritems(&leaf->header);
1430         data_end = leaf_data_end(root, leaf);
1431
1432         slot = path->slots[0];
1433         old_data_start = btrfs_item_offset(leaf->items + slot);
1434         old_size = btrfs_item_size(leaf->items + slot);
1435         BUG_ON(old_size <= new_size);
1436         size_diff = old_size - new_size;
1437
1438         BUG_ON(slot < 0);
1439         BUG_ON(slot >= nritems);
1440
1441         /*
1442          * item0..itemN ... dataN.offset..dataN.size .. data0.size
1443          */
1444         /* first correct the data pointers */
1445         for (i = slot; i < nritems; i++) {
1446                 u32 ioff = btrfs_item_offset(leaf->items + i);
1447                 btrfs_set_item_offset(leaf->items + i,
1448                                       ioff + size_diff);
1449         }
1450         /* shift the data */
1451         btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1452                       data_end + size_diff, btrfs_leaf_data(leaf) +
1453                       data_end, old_data_start + new_size - data_end);
1454         btrfs_set_item_size(leaf->items + slot, new_size);
1455         btrfs_mark_buffer_dirty(leaf_buf);
1456
1457         ret = 0;
1458         if (btrfs_leaf_free_space(root, leaf) < 0)
1459                 BUG();
1460         check_leaf(root, path, 0);
1461         return ret;
1462 }
1463
1464 int btrfs_extend_item(struct btrfs_trans_handle *trans, struct btrfs_root
1465                       *root, struct btrfs_path *path, u32 data_size)
1466 {
1467         int ret = 0;
1468         int slot;
1469         int slot_orig;
1470         struct btrfs_leaf *leaf;
1471         struct buffer_head *leaf_buf;
1472         u32 nritems;
1473         unsigned int data_end;
1474         unsigned int old_data;
1475         unsigned int old_size;
1476         int i;
1477
1478         slot_orig = path->slots[0];
1479         leaf_buf = path->nodes[0];
1480         leaf = btrfs_buffer_leaf(leaf_buf);
1481
1482         nritems = btrfs_header_nritems(&leaf->header);
1483         data_end = leaf_data_end(root, leaf);
1484
1485         if (btrfs_leaf_free_space(root, leaf) < data_size)
1486                 BUG();
1487         slot = path->slots[0];
1488         old_data = btrfs_item_end(leaf->items + slot);
1489
1490         BUG_ON(slot < 0);
1491         BUG_ON(slot >= nritems);
1492
1493         /*
1494          * item0..itemN ... dataN.offset..dataN.size .. data0.size
1495          */
1496         /* first correct the data pointers */
1497         for (i = slot; i < nritems; i++) {
1498                 u32 ioff = btrfs_item_offset(leaf->items + i);
1499                 btrfs_set_item_offset(leaf->items + i,
1500                                       ioff - data_size);
1501         }
1502         /* shift the data */
1503         btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1504                       data_end - data_size, btrfs_leaf_data(leaf) +
1505                       data_end, old_data - data_end);
1506         data_end = old_data;
1507         old_size = btrfs_item_size(leaf->items + slot);
1508         btrfs_set_item_size(leaf->items + slot, old_size + data_size);
1509         btrfs_mark_buffer_dirty(leaf_buf);
1510
1511         ret = 0;
1512         if (btrfs_leaf_free_space(root, leaf) < 0)
1513                 BUG();
1514         check_leaf(root, path, 0);
1515         return ret;
1516 }
1517
1518 /*
1519  * Given a key and some data, insert an item into the tree.
1520  * This does all the path init required, making room in the tree if needed.
1521  */
1522 int btrfs_insert_empty_item(struct btrfs_trans_handle *trans, struct btrfs_root
1523                             *root, struct btrfs_path *path, struct btrfs_key
1524                             *cpu_key, u32 data_size)
1525 {
1526         int ret = 0;
1527         int slot;
1528         int slot_orig;
1529         struct btrfs_leaf *leaf;
1530         struct buffer_head *leaf_buf;
1531         u32 nritems;
1532         unsigned int data_end;
1533         struct btrfs_disk_key disk_key;
1534
1535         btrfs_cpu_key_to_disk(&disk_key, cpu_key);
1536
1537         /* create a root if there isn't one */
1538         if (!root->node)
1539                 BUG();
1540         ret = btrfs_search_slot(trans, root, cpu_key, path, data_size, 1);
1541         if (ret == 0) {
1542                 return -EEXIST;
1543         }
1544         if (ret < 0)
1545                 goto out;
1546
1547         slot_orig = path->slots[0];
1548         leaf_buf = path->nodes[0];
1549         leaf = btrfs_buffer_leaf(leaf_buf);
1550
1551         nritems = btrfs_header_nritems(&leaf->header);
1552         data_end = leaf_data_end(root, leaf);
1553
1554         if (btrfs_leaf_free_space(root, leaf) <
1555             sizeof(struct btrfs_item) + data_size) {
1556                 BUG();
1557         }
1558         slot = path->slots[0];
1559         BUG_ON(slot < 0);
1560         if (slot != nritems) {
1561                 int i;
1562                 unsigned int old_data = btrfs_item_end(leaf->items + slot);
1563
1564                 /*
1565                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
1566                  */
1567                 /* first correct the data pointers */
1568                 for (i = slot; i < nritems; i++) {
1569                         u32 ioff = btrfs_item_offset(leaf->items + i);
1570                         btrfs_set_item_offset(leaf->items + i,
1571                                               ioff - data_size);
1572                 }
1573
1574                 /* shift the items */
1575                 btrfs_memmove(root, leaf, leaf->items + slot + 1,
1576                               leaf->items + slot,
1577                               (nritems - slot) * sizeof(struct btrfs_item));
1578
1579                 /* shift the data */
1580                 btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1581                               data_end - data_size, btrfs_leaf_data(leaf) +
1582                               data_end, old_data - data_end);
1583                 data_end = old_data;
1584         }
1585         /* setup the item for the new data */
1586         btrfs_memcpy(root, leaf, &leaf->items[slot].key, &disk_key,
1587                      sizeof(struct btrfs_disk_key));
1588         btrfs_set_item_offset(leaf->items + slot, data_end - data_size);
1589         btrfs_set_item_size(leaf->items + slot, data_size);
1590         btrfs_set_header_nritems(&leaf->header, nritems + 1);
1591         btrfs_mark_buffer_dirty(leaf_buf);
1592
1593         ret = 0;
1594         if (slot == 0)
1595                 ret = fixup_low_keys(trans, root, path, &disk_key, 1);
1596
1597         if (btrfs_leaf_free_space(root, leaf) < 0)
1598                 BUG();
1599         check_leaf(root, path, 0);
1600 out:
1601         return ret;
1602 }
1603
1604 /*
1605  * Given a key and some data, insert an item into the tree.
1606  * This does all the path init required, making room in the tree if needed.
1607  */
1608 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root
1609                       *root, struct btrfs_key *cpu_key, void *data, u32
1610                       data_size)
1611 {
1612         int ret = 0;
1613         struct btrfs_path *path;
1614         u8 *ptr;
1615
1616         path = btrfs_alloc_path();
1617         BUG_ON(!path);
1618         btrfs_init_path(path);
1619         ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
1620         if (!ret) {
1621                 ptr = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]),
1622                                      path->slots[0], u8);
1623                 btrfs_memcpy(root, path->nodes[0]->b_data,
1624                              ptr, data, data_size);
1625                 btrfs_mark_buffer_dirty(path->nodes[0]);
1626         }
1627         btrfs_release_path(root, path);
1628         btrfs_free_path(path);
1629         return ret;
1630 }
1631
1632 /*
1633  * delete the pointer from a given node.
1634  *
1635  * If the delete empties a node, the node is removed from the tree,
1636  * continuing all the way the root if required.  The root is converted into
1637  * a leaf if all the nodes are emptied.
1638  */
1639 static int del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
1640                    struct btrfs_path *path, int level, int slot)
1641 {
1642         struct btrfs_node *node;
1643         struct buffer_head *parent = path->nodes[level];
1644         u32 nritems;
1645         int ret = 0;
1646         int wret;
1647
1648         node = btrfs_buffer_node(parent);
1649         nritems = btrfs_header_nritems(&node->header);
1650         if (slot != nritems -1) {
1651                 btrfs_memmove(root, node, node->ptrs + slot,
1652                               node->ptrs + slot + 1,
1653                               sizeof(struct btrfs_key_ptr) *
1654                               (nritems - slot - 1));
1655         }
1656         nritems--;
1657         btrfs_set_header_nritems(&node->header, nritems);
1658         if (nritems == 0 && parent == root->node) {
1659                 struct btrfs_header *header = btrfs_buffer_header(root->node);
1660                 BUG_ON(btrfs_header_level(header) != 1);
1661                 /* just turn the root into a leaf and break */
1662                 btrfs_set_header_level(header, 0);
1663         } else if (slot == 0) {
1664                 wret = fixup_low_keys(trans, root, path, &node->ptrs[0].key,
1665                                       level + 1);
1666                 if (wret)
1667                         ret = wret;
1668         }
1669         btrfs_mark_buffer_dirty(parent);
1670         return ret;
1671 }
1672
1673 /*
1674  * delete the item at the leaf level in path.  If that empties
1675  * the leaf, remove it from the tree
1676  */
1677 int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
1678                    struct btrfs_path *path)
1679 {
1680         int slot;
1681         struct btrfs_leaf *leaf;
1682         struct buffer_head *leaf_buf;
1683         int doff;
1684         int dsize;
1685         int ret = 0;
1686         int wret;
1687         u32 nritems;
1688
1689         leaf_buf = path->nodes[0];
1690         leaf = btrfs_buffer_leaf(leaf_buf);
1691         slot = path->slots[0];
1692         doff = btrfs_item_offset(leaf->items + slot);
1693         dsize = btrfs_item_size(leaf->items + slot);
1694         nritems = btrfs_header_nritems(&leaf->header);
1695
1696         if (slot != nritems - 1) {
1697                 int i;
1698                 int data_end = leaf_data_end(root, leaf);
1699                 btrfs_memmove(root, leaf, btrfs_leaf_data(leaf) +
1700                               data_end + dsize,
1701                               btrfs_leaf_data(leaf) + data_end,
1702                               doff - data_end);
1703                 for (i = slot + 1; i < nritems; i++) {
1704                         u32 ioff = btrfs_item_offset(leaf->items + i);
1705                         btrfs_set_item_offset(leaf->items + i, ioff + dsize);
1706                 }
1707                 btrfs_memmove(root, leaf, leaf->items + slot,
1708                               leaf->items + slot + 1,
1709                               sizeof(struct btrfs_item) *
1710                               (nritems - slot - 1));
1711         }
1712         btrfs_set_header_nritems(&leaf->header, nritems - 1);
1713         nritems--;
1714         /* delete the leaf if we've emptied it */
1715         if (nritems == 0) {
1716                 if (leaf_buf == root->node) {
1717                         btrfs_set_header_level(&leaf->header, 0);
1718                 } else {
1719                         clean_tree_block(trans, root, leaf_buf);
1720                         wait_on_buffer(leaf_buf);
1721                         wret = del_ptr(trans, root, path, 1, path->slots[1]);
1722                         if (wret)
1723                                 ret = wret;
1724                         wret = btrfs_free_extent(trans, root,
1725                                                  bh_blocknr(leaf_buf), 1, 1);
1726                         if (wret)
1727                                 ret = wret;
1728                 }
1729         } else {
1730                 int used = leaf_space_used(leaf, 0, nritems);
1731                 if (slot == 0) {
1732                         wret = fixup_low_keys(trans, root, path,
1733                                               &leaf->items[0].key, 1);
1734                         if (wret)
1735                                 ret = wret;
1736                 }
1737
1738                 /* delete the leaf if it is mostly empty */
1739                 if (used < BTRFS_LEAF_DATA_SIZE(root) / 3) {
1740                         /* push_leaf_left fixes the path.
1741                          * make sure the path still points to our leaf
1742                          * for possible call to del_ptr below
1743                          */
1744                         slot = path->slots[1];
1745                         get_bh(leaf_buf);
1746                         wret = push_leaf_left(trans, root, path, 1);
1747                         if (wret < 0)
1748                                 ret = wret;
1749                         if (path->nodes[0] == leaf_buf &&
1750                             btrfs_header_nritems(&leaf->header)) {
1751                                 wret = push_leaf_right(trans, root, path, 1);
1752                                 if (wret < 0)
1753                                         ret = wret;
1754                         }
1755                         if (btrfs_header_nritems(&leaf->header) == 0) {
1756                                 u64 blocknr = bh_blocknr(leaf_buf);
1757                                 clean_tree_block(trans, root, leaf_buf);
1758                                 wait_on_buffer(leaf_buf);
1759                                 wret = del_ptr(trans, root, path, 1, slot);
1760                                 if (wret)
1761                                         ret = wret;
1762                                 btrfs_block_release(root, leaf_buf);
1763                                 wret = btrfs_free_extent(trans, root, blocknr,
1764                                                          1, 1);
1765                                 if (wret)
1766                                         ret = wret;
1767                         } else {
1768                                 btrfs_mark_buffer_dirty(leaf_buf);
1769                                 btrfs_block_release(root, leaf_buf);
1770                         }
1771                 } else {
1772                         btrfs_mark_buffer_dirty(leaf_buf);
1773                 }
1774         }
1775         return ret;
1776 }
1777
1778 /*
1779  * walk up the tree as far as required to find the next leaf.
1780  * returns 0 if it found something or 1 if there are no greater leaves.
1781  * returns < 0 on io errors.
1782  */
1783 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
1784 {
1785         int slot;
1786         int level = 1;
1787         u64 blocknr;
1788         struct buffer_head *c;
1789         struct btrfs_node *c_node;
1790         struct buffer_head *next = NULL;
1791
1792         while(level < BTRFS_MAX_LEVEL) {
1793                 if (!path->nodes[level])
1794                         return 1;
1795                 slot = path->slots[level] + 1;
1796                 c = path->nodes[level];
1797                 c_node = btrfs_buffer_node(c);
1798                 if (slot >= btrfs_header_nritems(&c_node->header)) {
1799                         level++;
1800                         continue;
1801                 }
1802                 blocknr = btrfs_node_blockptr(c_node, slot);
1803                 if (next)
1804                         btrfs_block_release(root, next);
1805                 next = read_tree_block(root, blocknr);
1806                 break;
1807         }
1808         path->slots[level] = slot;
1809         while(1) {
1810                 level--;
1811                 c = path->nodes[level];
1812                 btrfs_block_release(root, c);
1813                 path->nodes[level] = next;
1814                 path->slots[level] = 0;
1815                 if (!level)
1816                         break;
1817                 next = read_tree_block(root,
1818                        btrfs_node_blockptr(btrfs_buffer_node(next), 0));
1819         }
1820         return 0;
1821 }