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