fs/btrfs/extent-tree.c

   1 #include <linux/module.h>
   2 #include "ctree.h"
   3 #include "disk-io.h"
   4 #include "print-tree.h"
   5 #include "transaction.h"
   6
   7 static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
   8                             *orig_root, u64 num_blocks, u64 search_start, u64
   9                             search_end, struct btrfs_key *ins);
  10 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
  11                                  btrfs_root *extent_root);
  12 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
  13                                btrfs_root *extent_root);
  14
  15 static int inc_block_ref(struct btrfs_trans_handle *trans, struct btrfs_root
  16                          *root, u64 blocknr, u64 num_blocks)
  17 {
  18         struct btrfs_path *path;
  19         int ret;
  20         struct btrfs_key key;
  21         struct btrfs_leaf *l;
  22         struct btrfs_extent_item *item;
  23         struct btrfs_key ins;
  24         u32 refs;
  25
  26         find_free_extent(trans, root->fs_info->extent_root, 0, 0, (u64)-1,
  27                          &ins);
  28         path = btrfs_alloc_path();
  29         BUG_ON(!path);
  30         btrfs_init_path(path);
  31         key.objectid = blocknr;
  32         key.flags = 0;
  33         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
  34         key.offset = num_blocks;
  35         ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key, path,
  36                                 0, 1);
  37         if (ret != 0)
  38                 BUG();
  39         BUG_ON(ret != 0);
  40         l = btrfs_buffer_leaf(path->nodes[0]);
  41         item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
  42         refs = btrfs_extent_refs(item);
  43         btrfs_set_extent_refs(item, refs + 1);
  44         btrfs_mark_buffer_dirty(path->nodes[0]);
  45
  46         btrfs_release_path(root->fs_info->extent_root, path);
  47         btrfs_free_path(path);
  48         finish_current_insert(trans, root->fs_info->extent_root);
  49         del_pending_extents(trans, root->fs_info->extent_root);
  50         return 0;
  51 }
  52
  53 static int lookup_block_ref(struct btrfs_trans_handle *trans, struct btrfs_root
  54                             *root, u64 blocknr, u64 num_blocks, u32 *refs)
  55 {
  56         struct btrfs_path *path;
  57         int ret;
  58         struct btrfs_key key;
  59         struct btrfs_leaf *l;
  60         struct btrfs_extent_item *item;
  61
  62         path = btrfs_alloc_path();
  63         btrfs_init_path(path);
  64         key.objectid = blocknr;
  65         key.offset = num_blocks;
  66         key.flags = 0;
  67         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
  68         ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key, path,
  69                                 0, 0);
  70         if (ret != 0)
  71                 BUG();
  72         l = btrfs_buffer_leaf(path->nodes[0]);
  73         item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
  74         *refs = btrfs_extent_refs(item);
  75         btrfs_release_path(root->fs_info->extent_root, path);
  76         btrfs_free_path(path);
  77         return 0;
  78 }
  79
  80 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  81                   struct buffer_head *buf)
  82 {
  83         u64 blocknr;
  84         struct btrfs_node *buf_node;
  85         struct btrfs_leaf *buf_leaf;
  86         struct btrfs_disk_key *key;
  87         struct btrfs_file_extent_item *fi;
  88         int i;
  89         int leaf;
  90         int ret;
  91
  92         if (!root->ref_cows)
  93                 return 0;
  94         buf_node = btrfs_buffer_node(buf);
  95         leaf = btrfs_is_leaf(buf_node);
  96         buf_leaf = btrfs_buffer_leaf(buf);
  97         for (i = 0; i < btrfs_header_nritems(&buf_node->header); i++) {
  98                 if (leaf) {
  99                         key = &buf_leaf->items[i].key;
 100                         if (btrfs_disk_key_type(key) != BTRFS_EXTENT_DATA_KEY)
 101                                 continue;
 102                         fi = btrfs_item_ptr(buf_leaf, i,
 103                                             struct btrfs_file_extent_item);
 104                         ret = inc_block_ref(trans, root,
 105                                     btrfs_file_extent_disk_blocknr(fi),
 106                                     btrfs_file_extent_disk_num_blocks(fi));
 107                         BUG_ON(ret);
 108                 } else {
 109                         blocknr = btrfs_node_blockptr(buf_node, i);
 110                         ret = inc_block_ref(trans, root, blocknr, 1);
 111                         BUG_ON(ret);
 112                 }
 113         }
 114         return 0;
 115 }
 116
 117 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans, struct
 118                                btrfs_root *root)
 119 {
 120         unsigned long gang[8];
 121         u64 first = 0;
 122         int ret;
 123         int i;
 124         struct radix_tree_root *pinned_radix = &root->fs_info->pinned_radix;
 125
 126         while(1) {
 127                 ret = find_first_radix_bit(pinned_radix, gang,
 128                                            ARRAY_SIZE(gang));
 129                 if (!ret)
 130                         break;
 131                 if (!first)
 132                         first = gang[0];
 133                 for (i = 0; i < ret; i++) {
 134                         clear_radix_bit(pinned_radix, gang[i]);
 135                 }
 136         }
 137         if (root->fs_info->last_insert.objectid > first)
 138                 root->fs_info->last_insert.objectid = first;
 139         root->fs_info->last_insert.offset = 0;
 140         return 0;
 141 }
 142
 143 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
 144                                  btrfs_root *extent_root)
 145 {
 146         struct btrfs_key ins;
 147         struct btrfs_extent_item extent_item;
 148         int i;
 149         int ret;
 150         u64 super_blocks_used;
 151         struct btrfs_fs_info *info = extent_root->fs_info;
 152
 153         btrfs_set_extent_refs(&extent_item, 1);
 154         btrfs_set_extent_owner(&extent_item,
 155                 btrfs_header_parentid(btrfs_buffer_header(extent_root->node)));
 156         ins.offset = 1;
 157         ins.flags = 0;
 158         btrfs_set_key_type(&ins, BTRFS_EXTENT_ITEM_KEY);
 159
 160         for (i = 0; i < extent_root->fs_info->current_insert.flags; i++) {
 161                 ins.objectid = extent_root->fs_info->current_insert.objectid +
 162                                 i;
 163                 super_blocks_used = btrfs_super_blocks_used(info->disk_super);
 164                 btrfs_set_super_blocks_used(info->disk_super,
 165                                             super_blocks_used + 1);
 166                 ret = btrfs_insert_item(trans, extent_root, &ins, &extent_item,
 167                                         sizeof(extent_item));
 168                 BUG_ON(ret);
 169         }
 170         extent_root->fs_info->current_insert.offset = 0;
 171         return 0;
 172 }
 173
 174 static int pin_down_block(struct btrfs_root *root, u64 blocknr, int pending)
 175 {
 176         int err;
 177         struct btrfs_header *header;
 178         struct buffer_head *bh;
 179
 180         if (!pending) {
 181                 bh = btrfs_find_tree_block(root, blocknr);
 182                 if (bh) {
 183                         if (buffer_uptodate(bh)) {
 184                                 u64 transid =
 185                                     root->fs_info->running_transaction->transid;
 186                                 header = btrfs_buffer_header(bh);
 187                                 if (btrfs_header_generation(header) ==
 188                                     transid) {
 189                                         btrfs_block_release(root, bh);
 190                                         return 0;
 191                                 }
 192                         }
 193                         btrfs_block_release(root, bh);
 194                 }
 195                 err = set_radix_bit(&root->fs_info->pinned_radix, blocknr);
 196         } else {
 197                 err = set_radix_bit(&root->fs_info->pending_del_radix, blocknr);
 198         }
 199         BUG_ON(err);
 200         return 0;
 201 }
 202
 203 /*
 204  * remove an extent from the root, returns 0 on success
 205  */
 206 static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 207                          *root, u64 blocknr, u64 num_blocks, int pin)
 208 {
 209         struct btrfs_path *path;
 210         struct btrfs_key key;
 211         struct btrfs_fs_info *info = root->fs_info;
 212         struct btrfs_root *extent_root = info->extent_root;
 213         int ret;
 214         struct btrfs_extent_item *ei;
 215         struct btrfs_key ins;
 216         u32 refs;
 217
 218         key.objectid = blocknr;
 219         key.flags = 0;
 220         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
 221         key.offset = num_blocks;
 222
 223         find_free_extent(trans, root, 0, 0, (u64)-1, &ins);
 224         path = btrfs_alloc_path();
 225         BUG_ON(!path);
 226         btrfs_init_path(path);
 227         ret = btrfs_search_slot(trans, extent_root, &key, path, -1, 1);
 228         if (ret) {
 229                 printk("failed to find %Lu\n", key.objectid);
 230                 btrfs_print_tree(extent_root, extent_root->node);
 231                 printk("failed to find %Lu\n", key.objectid);
 232                 BUG();
 233         }
 234         ei = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]), path->slots[0],
 235                             struct btrfs_extent_item);
 236         BUG_ON(ei->refs == 0);
 237         refs = btrfs_extent_refs(ei) - 1;
 238         btrfs_set_extent_refs(ei, refs);
 239         btrfs_mark_buffer_dirty(path->nodes[0]);
 240         if (refs == 0) {
 241                 u64 super_blocks_used;
 242
 243                 if (pin) {
 244                         ret = pin_down_block(root, blocknr, 0);
 245                         BUG_ON(ret);
 246                 }
 247
 248                 super_blocks_used = btrfs_super_blocks_used(info->disk_super);
 249                 btrfs_set_super_blocks_used(info->disk_super,
 250                                             super_blocks_used - num_blocks);
 251                 ret = btrfs_del_item(trans, extent_root, path);
 252                 if (extent_root->fs_info->last_insert.objectid > blocknr)
 253                         extent_root->fs_info->last_insert.objectid = blocknr;
 254                 if (ret)
 255                         BUG();
 256         }
 257         btrfs_release_path(extent_root, path);
 258         btrfs_free_path(path);
 259         finish_current_insert(trans, extent_root);
 260         return ret;
 261 }
 262
 263 /*
 264  * find all the blocks marked as pending in the radix tree and remove
 265  * them from the extent map
 266  */
 267 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
 268                                btrfs_root *extent_root)
 269 {
 270         int ret;
 271         int wret;
 272         int err = 0;
 273         unsigned long gang[4];
 274         int i;
 275         struct radix_tree_root *pending_radix;
 276         struct radix_tree_root *pinned_radix;
 277
 278         pending_radix = &extent_root->fs_info->pending_del_radix;
 279         pinned_radix = &extent_root->fs_info->pinned_radix;
 280
 281         while(1) {
 282                 ret = find_first_radix_bit(pending_radix, gang,
 283                                            ARRAY_SIZE(gang));
 284                 if (!ret)
 285                         break;
 286                 for (i = 0; i < ret; i++) {
 287                         wret = set_radix_bit(pinned_radix, gang[i]);
 288                         BUG_ON(wret);
 289                         wret = clear_radix_bit(pending_radix, gang[i]);
 290                         BUG_ON(wret);
 291                         wret = __free_extent(trans, extent_root,
 292                                              gang[i], 1, 0);
 293                         if (wret)
 294                                 err = wret;
 295                 }
 296         }
 297         return err;
 298 }
 299
 300 /*
 301  * remove an extent from the root, returns 0 on success
 302  */
 303 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 304                       *root, u64 blocknr, u64 num_blocks, int pin)
 305 {
 306         struct btrfs_root *extent_root = root->fs_info->extent_root;
 307         int pending_ret;
 308         int ret;
 309
 310         if (root == extent_root) {
 311                 pin_down_block(root, blocknr, 1);
 312                 return 0;
 313         }
 314         ret = __free_extent(trans, root, blocknr, num_blocks, pin);
 315         pending_ret = del_pending_extents(trans, root->fs_info->extent_root);
 316         return ret ? ret : pending_ret;
 317 }
 318
 319 /*
 320  * walks the btree of allocated extents and find a hole of a given size.
 321  * The key ins is changed to record the hole:
 322  * ins->objectid == block start
 323  * ins->flags = BTRFS_EXTENT_ITEM_KEY
 324  * ins->offset == number of blocks
 325  * Any available blocks before search_start are skipped.
 326  */
 327 static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 328                             *orig_root, u64 num_blocks, u64 search_start, u64
 329                             search_end, struct btrfs_key *ins)
 330 {
 331         struct btrfs_path *path;
 332         struct btrfs_key key;
 333         int ret;
 334         u64 hole_size = 0;
 335         int slot = 0;
 336         u64 last_block = 0;
 337         u64 test_block;
 338         int start_found;
 339         struct btrfs_leaf *l;
 340         struct btrfs_root * root = orig_root->fs_info->extent_root;
 341         int total_needed = num_blocks;
 342         int level;
 343
 344         level = btrfs_header_level(btrfs_buffer_header(root->node));
 345         total_needed += (level + 1) * 3;
 346         if (root->fs_info->last_insert.objectid > search_start)
 347                 search_start = root->fs_info->last_insert.objectid;
 348
 349         ins->flags = 0;
 350         btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY);
 351         path = btrfs_alloc_path();
 352
 353 check_failed:
 354         btrfs_init_path(path);
 355         ins->objectid = search_start;
 356         ins->offset = 0;
 357         start_found = 0;
 358         ret = btrfs_search_slot(trans, root, ins, path, 0, 0);
 359         if (ret < 0)
 360                 goto error;
 361
 362         if (path->slots[0] > 0)
 363                 path->slots[0]--;
 364
 365         while (1) {
 366                 l = btrfs_buffer_leaf(path->nodes[0]);
 367                 slot = path->slots[0];
 368                 if (slot >= btrfs_header_nritems(&l->header)) {
 369                         ret = btrfs_next_leaf(root, path);
 370                         if (ret == 0)
 371                                 continue;
 372                         if (ret < 0)
 373                                 goto error;
 374                         if (!start_found) {
 375                                 ins->objectid = search_start;
 376                                 ins->offset = (u64)-1;
 377                                 start_found = 1;
 378                                 goto check_pending;
 379                         }
 380                         ins->objectid = last_block > search_start ?
 381                                         last_block : search_start;
 382                         ins->offset = (u64)-1;
 383                         goto check_pending;
 384                 }
 385                 btrfs_disk_key_to_cpu(&key, &l->items[slot].key);
 386                 if (key.objectid >= search_start) {
 387                         if (start_found) {
 388                                 if (last_block < search_start)
 389                                         last_block = search_start;
 390                                 hole_size = key.objectid - last_block;
 391                                 if (hole_size > total_needed) {
 392                                         ins->objectid = last_block;
 393                                         ins->offset = hole_size;
 394                                         goto check_pending;
 395                                 }
 396                         }
 397                 }
 398                 start_found = 1;
 399                 last_block = key.objectid + key.offset;
 400                 path->slots[0]++;
 401         }
 402         // FIXME -ENOSPC
 403 check_pending:
 404         /* we have to make sure we didn't find an extent that has already
 405          * been allocated by the map tree or the original allocation
 406          */
 407         btrfs_release_path(root, path);
 408         BUG_ON(ins->objectid < search_start);
 409         for (test_block = ins->objectid;
 410              test_block < ins->objectid + total_needed; test_block++) {
 411                 if (test_radix_bit(&root->fs_info->pinned_radix,
 412                                       test_block)) {
 413                         search_start = test_block + 1;
 414                         goto check_failed;
 415                 }
 416         }
 417         BUG_ON(root->fs_info->current_insert.offset);
 418         root->fs_info->current_insert.offset = total_needed - num_blocks;
 419         root->fs_info->current_insert.objectid = ins->objectid + num_blocks;
 420         root->fs_info->current_insert.flags = 0;
 421         root->fs_info->last_insert.objectid = ins->objectid;
 422         ins->offset = num_blocks;
 423         btrfs_free_path(path);
 424         return 0;
 425 error:
 426         btrfs_release_path(root, path);
 427         btrfs_free_path(path);
 428         return ret;
 429 }
 430
 431 /*
 432  * finds a free extent and does all the dirty work required for allocation
 433  * returns the key for the extent through ins, and a tree buffer for
 434  * the first block of the extent through buf.
 435  *
 436  * returns 0 if everything worked, non-zero otherwise.
 437  */
 438 int btrfs_alloc_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 439                         *root, u64 num_blocks, u64 search_start, u64
 440                         search_end, u64 owner, struct btrfs_key *ins)
 441 {
 442         int ret;
 443         int pending_ret;
 444         u64 super_blocks_used;
 445         struct btrfs_fs_info *info = root->fs_info;
 446         struct btrfs_root *extent_root = info->extent_root;
 447         struct btrfs_extent_item extent_item;
 448
 449         btrfs_set_extent_refs(&extent_item, 1);
 450         btrfs_set_extent_owner(&extent_item, owner);
 451
 452         if (root == extent_root) {
 453                 BUG_ON(extent_root->fs_info->current_insert.offset == 0);
 454                 BUG_ON(num_blocks != 1);
 455                 BUG_ON(extent_root->fs_info->current_insert.flags ==
 456                        extent_root->fs_info->current_insert.offset);
 457                 ins->offset = 1;
 458                 ins->objectid = extent_root->fs_info->current_insert.objectid +
 459                                 extent_root->fs_info->current_insert.flags++;
 460                 return 0;
 461         }
 462         ret = find_free_extent(trans, root, num_blocks, search_start,
 463                                search_end, ins);
 464         if (ret)
 465                 return ret;
 466
 467         super_blocks_used = btrfs_super_blocks_used(info->disk_super);
 468         btrfs_set_super_blocks_used(info->disk_super, super_blocks_used +
 469                                     num_blocks);
 470         ret = btrfs_insert_item(trans, extent_root, ins, &extent_item,
 471                                 sizeof(extent_item));
 472
 473         finish_current_insert(trans, extent_root);
 474         pending_ret = del_pending_extents(trans, extent_root);
 475         if (ret)
 476                 return ret;
 477         if (pending_ret)
 478                 return pending_ret;
 479         return 0;
 480 }
 481
 482 /*
 483  * helper function to allocate a block for a given tree
 484  * returns the tree buffer or NULL.
 485  */
 486 struct buffer_head *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 487                                             struct btrfs_root *root)
 488 {
 489         struct btrfs_key ins;
 490         int ret;
 491         struct buffer_head *buf;
 492
 493         ret = btrfs_alloc_extent(trans, root, 1, 0, (unsigned long)-1,
 494                 btrfs_header_parentid(btrfs_buffer_header(root->node)), &ins);
 495         if (ret) {
 496                 BUG();
 497                 return NULL;
 498         }
 499         buf = btrfs_find_create_tree_block(root, ins.objectid);
 500         set_buffer_uptodate(buf);
 501         return buf;
 502 }
 503
 504 static int drop_leaf_ref(struct btrfs_trans_handle *trans,
 505                          struct btrfs_root *root, struct buffer_head *cur)
 506 {
 507         struct btrfs_disk_key *key;
 508         struct btrfs_leaf *leaf;
 509         struct btrfs_file_extent_item *fi;
 510         int i;
 511         int nritems;
 512         int ret;
 513
 514         BUG_ON(!btrfs_is_leaf(btrfs_buffer_node(cur)));
 515         leaf = btrfs_buffer_leaf(cur);
 516         nritems = btrfs_header_nritems(&leaf->header);
 517         for (i = 0; i < nritems; i++) {
 518                 key = &leaf->items[i].key;
 519                 if (btrfs_disk_key_type(key) != BTRFS_EXTENT_DATA_KEY)
 520                         continue;
 521                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
 522                 /*
 523                  * FIXME make sure to insert a trans record that
 524                  * repeats the snapshot del on crash
 525                  */
 526                 ret = btrfs_free_extent(trans, root,
 527                                         btrfs_file_extent_disk_blocknr(fi),
 528                                         btrfs_file_extent_disk_num_blocks(fi),
 529                                         0);
 530                 BUG_ON(ret);
 531         }
 532         return 0;
 533 }
 534
 535 /*
 536  * helper function for drop_snapshot, this walks down the tree dropping ref
 537  * counts as it goes.
 538  */
 539 static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
 540                           *root, struct btrfs_path *path, int *level)
 541 {
 542         struct buffer_head *next;
 543         struct buffer_head *cur;
 544         u64 blocknr;
 545         int ret;
 546         u32 refs;
 547
 548         WARN_ON(*level < 0);
 549         WARN_ON(*level >= BTRFS_MAX_LEVEL);
 550         ret = lookup_block_ref(trans, root, path->nodes[*level]->b_blocknr,
 551                                1, &refs);
 552         BUG_ON(ret);
 553         if (refs > 1)
 554                 goto out;
 555         /*
 556          * walk down to the last node level and free all the leaves
 557          */
 558         while(*level >= 0) {
 559                 WARN_ON(*level < 0);
 560                 WARN_ON(*level >= BTRFS_MAX_LEVEL);
 561                 cur = path->nodes[*level];
 562                 if (btrfs_header_level(btrfs_buffer_header(cur)) != *level)
 563                         WARN_ON(1);
 564                 if (path->slots[*level] >=
 565                     btrfs_header_nritems(btrfs_buffer_header(cur)))
 566                         break;
 567                 if (*level == 0) {
 568                         ret = drop_leaf_ref(trans, root, cur);
 569                         BUG_ON(ret);
 570                         break;
 571                 }
 572                 blocknr = btrfs_node_blockptr(btrfs_buffer_node(cur),
 573                                               path->slots[*level]);
 574                 ret = lookup_block_ref(trans, root, blocknr, 1, &refs);
 575                 BUG_ON(ret);
 576                 if (refs != 1) {
 577                         path->slots[*level]++;
 578                         ret = btrfs_free_extent(trans, root, blocknr, 1, 1);
 579                         BUG_ON(ret);
 580                         continue;
 581                 }
 582                 next = read_tree_block(root, blocknr);
 583                 WARN_ON(*level <= 0);
 584                 if (path->nodes[*level-1])
 585                         btrfs_block_release(root, path->nodes[*level-1]);
 586                 path->nodes[*level-1] = next;
 587                 *level = btrfs_header_level(btrfs_buffer_header(next));
 588                 path->slots[*level] = 0;
 589         }
 590 out:
 591         WARN_ON(*level < 0);
 592         WARN_ON(*level >= BTRFS_MAX_LEVEL);
 593         ret = btrfs_free_extent(trans, root,
 594                                 path->nodes[*level]->b_blocknr, 1, 1);
 595         btrfs_block_release(root, path->nodes[*level]);
 596         path->nodes[*level] = NULL;
 597         *level += 1;
 598         BUG_ON(ret);
 599         return 0;
 600 }
 601
 602 /*
 603  * helper for dropping snapshots.  This walks back up the tree in the path
 604  * to find the first node higher up where we haven't yet gone through
 605  * all the slots
 606  */
 607 static int walk_up_tree(struct btrfs_trans_handle *trans, struct btrfs_root
 608                         *root, struct btrfs_path *path, int *level)
 609 {
 610         int i;
 611         int slot;
 612         int ret;
 613         for(i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
 614                 slot = path->slots[i];
 615                 if (slot < btrfs_header_nritems(
 616                     btrfs_buffer_header(path->nodes[i])) - 1) {
 617                         path->slots[i]++;
 618                         *level = i;
 619                         return 0;
 620                 } else {
 621                         ret = btrfs_free_extent(trans, root,
 622                                                 path->nodes[*level]->b_blocknr,
 623                                                 1, 1);
 624                         BUG_ON(ret);
 625                         btrfs_block_release(root, path->nodes[*level]);
 626                         path->nodes[*level] = NULL;
 627                         *level = i + 1;
 628                 }
 629         }
 630         return 1;
 631 }
 632
 633 /*
 634  * drop the reference count on the tree rooted at 'snap'.  This traverses
 635  * the tree freeing any blocks that have a ref count of zero after being
 636  * decremented.
 637  */
 638 int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
 639                         *root, struct buffer_head *snap)
 640 {
 641         int ret = 0;
 642         int wret;
 643         int level;
 644         struct btrfs_path *path;
 645         int i;
 646         int orig_level;
 647
 648         path = btrfs_alloc_path();
 649         BUG_ON(!path);
 650         btrfs_init_path(path);
 651
 652         level = btrfs_header_level(btrfs_buffer_header(snap));
 653         orig_level = level;
 654         path->nodes[level] = snap;
 655         path->slots[level] = 0;
 656         while(1) {
 657                 wret = walk_down_tree(trans, root, path, &level);
 658                 if (wret > 0)
 659                         break;
 660                 if (wret < 0)
 661                         ret = wret;
 662
 663                 wret = walk_up_tree(trans, root, path, &level);
 664                 if (wret > 0)
 665                         break;
 666                 if (wret < 0)
 667                         ret = wret;
 668         }
 669         for (i = 0; i <= orig_level; i++) {
 670                 if (path->nodes[i]) {
 671                         btrfs_block_release(root, path->nodes[i]);
 672                 }
 673         }
 674         btrfs_free_path(path);
 675         return ret;
 676 }