fs/btrfs/free-space-tree.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2015 Facebook.  All rights reserved.
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/sched/mm.h>
   8 #include "ctree.h"
   9 #include "disk-io.h"
  10 #include "locking.h"
  11 #include "free-space-tree.h"
  12 #include "transaction.h"
  13
  14 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
  15                                         struct btrfs_block_group_cache *block_group,
  16                                         struct btrfs_path *path);
  17
  18 void set_free_space_tree_thresholds(struct btrfs_block_group_cache *cache)
  19 {
  20         u32 bitmap_range;
  21         size_t bitmap_size;
  22         u64 num_bitmaps, total_bitmap_size;
  23
  24         /*
  25          * We convert to bitmaps when the disk space required for using extents
  26          * exceeds that required for using bitmaps.
  27          */
  28         bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
  29         num_bitmaps = div_u64(cache->key.offset + bitmap_range - 1,
  30                               bitmap_range);
  31         bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
  32         total_bitmap_size = num_bitmaps * bitmap_size;
  33         cache->bitmap_high_thresh = div_u64(total_bitmap_size,
  34                                             sizeof(struct btrfs_item));
  35
  36         /*
  37          * We allow for a small buffer between the high threshold and low
  38          * threshold to avoid thrashing back and forth between the two formats.
  39          */
  40         if (cache->bitmap_high_thresh > 100)
  41                 cache->bitmap_low_thresh = cache->bitmap_high_thresh - 100;
  42         else
  43                 cache->bitmap_low_thresh = 0;
  44 }
  45
  46 static int add_new_free_space_info(struct btrfs_trans_handle *trans,
  47                                    struct btrfs_block_group_cache *block_group,
  48                                    struct btrfs_path *path)
  49 {
  50         struct btrfs_root *root = trans->fs_info->free_space_root;
  51         struct btrfs_free_space_info *info;
  52         struct btrfs_key key;
  53         struct extent_buffer *leaf;
  54         int ret;
  55
  56         key.objectid = block_group->key.objectid;
  57         key.type = BTRFS_FREE_SPACE_INFO_KEY;
  58         key.offset = block_group->key.offset;
  59
  60         ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
  61         if (ret)
  62                 goto out;
  63
  64         leaf = path->nodes[0];
  65         info = btrfs_item_ptr(leaf, path->slots[0],
  66                               struct btrfs_free_space_info);
  67         btrfs_set_free_space_extent_count(leaf, info, 0);
  68         btrfs_set_free_space_flags(leaf, info, 0);
  69         btrfs_mark_buffer_dirty(leaf);
  70
  71         ret = 0;
  72 out:
  73         btrfs_release_path(path);
  74         return ret;
  75 }
  76
  77 struct btrfs_free_space_info *
  78 search_free_space_info(struct btrfs_trans_handle *trans,
  79                        struct btrfs_fs_info *fs_info,
  80                        struct btrfs_block_group_cache *block_group,
  81                        struct btrfs_path *path, int cow)
  82 {
  83         struct btrfs_root *root = fs_info->free_space_root;
  84         struct btrfs_key key;
  85         int ret;
  86
  87         key.objectid = block_group->key.objectid;
  88         key.type = BTRFS_FREE_SPACE_INFO_KEY;
  89         key.offset = block_group->key.offset;
  90
  91         ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
  92         if (ret < 0)
  93                 return ERR_PTR(ret);
  94         if (ret != 0) {
  95                 btrfs_warn(fs_info, "missing free space info for %llu",
  96                            block_group->key.objectid);
  97                 ASSERT(0);
  98                 return ERR_PTR(-ENOENT);
  99         }
 100
 101         return btrfs_item_ptr(path->nodes[0], path->slots[0],
 102                               struct btrfs_free_space_info);
 103 }
 104
 105 /*
 106  * btrfs_search_slot() but we're looking for the greatest key less than the
 107  * passed key.
 108  */
 109 static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
 110                                   struct btrfs_root *root,
 111                                   struct btrfs_key *key, struct btrfs_path *p,
 112                                   int ins_len, int cow)
 113 {
 114         int ret;
 115
 116         ret = btrfs_search_slot(trans, root, key, p, ins_len, cow);
 117         if (ret < 0)
 118                 return ret;
 119
 120         if (ret == 0) {
 121                 ASSERT(0);
 122                 return -EIO;
 123         }
 124
 125         if (p->slots[0] == 0) {
 126                 ASSERT(0);
 127                 return -EIO;
 128         }
 129         p->slots[0]--;
 130
 131         return 0;
 132 }
 133
 134 static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
 135 {
 136         return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
 137 }
 138
 139 static unsigned long *alloc_bitmap(u32 bitmap_size)
 140 {
 141         unsigned long *ret;
 142         unsigned int nofs_flag;
 143         u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));
 144
 145         /*
 146          * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
 147          * into the filesystem as the free space bitmap can be modified in the
 148          * critical section of a transaction commit.
 149          *
 150          * TODO: push the memalloc_nofs_{save,restore}() to the caller where we
 151          * know that recursion is unsafe.
 152          */
 153         nofs_flag = memalloc_nofs_save();
 154         ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
 155         memalloc_nofs_restore(nofs_flag);
 156         return ret;
 157 }
 158
 159 static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
 160 {
 161         u8 *p = ((u8 *)map) + BIT_BYTE(start);
 162         const unsigned int size = start + len;
 163         int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
 164         u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
 165
 166         while (len - bits_to_set >= 0) {
 167                 *p |= mask_to_set;
 168                 len -= bits_to_set;
 169                 bits_to_set = BITS_PER_BYTE;
 170                 mask_to_set = ~0;
 171                 p++;
 172         }
 173         if (len) {
 174                 mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
 175                 *p |= mask_to_set;
 176         }
 177 }
 178
 179 int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 180                                   struct btrfs_block_group_cache *block_group,
 181                                   struct btrfs_path *path)
 182 {
 183         struct btrfs_fs_info *fs_info = trans->fs_info;
 184         struct btrfs_root *root = fs_info->free_space_root;
 185         struct btrfs_free_space_info *info;
 186         struct btrfs_key key, found_key;
 187         struct extent_buffer *leaf;
 188         unsigned long *bitmap;
 189         char *bitmap_cursor;
 190         u64 start, end;
 191         u64 bitmap_range, i;
 192         u32 bitmap_size, flags, expected_extent_count;
 193         u32 extent_count = 0;
 194         int done = 0, nr;
 195         int ret;
 196
 197         bitmap_size = free_space_bitmap_size(block_group->key.offset,
 198                                              fs_info->sectorsize);
 199         bitmap = alloc_bitmap(bitmap_size);
 200         if (!bitmap) {
 201                 ret = -ENOMEM;
 202                 goto out;
 203         }
 204
 205         start = block_group->key.objectid;
 206         end = block_group->key.objectid + block_group->key.offset;
 207
 208         key.objectid = end - 1;
 209         key.type = (u8)-1;
 210         key.offset = (u64)-1;
 211
 212         while (!done) {
 213                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 214                 if (ret)
 215                         goto out;
 216
 217                 leaf = path->nodes[0];
 218                 nr = 0;
 219                 path->slots[0]++;
 220                 while (path->slots[0] > 0) {
 221                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 222
 223                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
 224                                 ASSERT(found_key.objectid == block_group->key.objectid);
 225                                 ASSERT(found_key.offset == block_group->key.offset);
 226                                 done = 1;
 227                                 break;
 228                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY) {
 229                                 u64 first, last;
 230
 231                                 ASSERT(found_key.objectid >= start);
 232                                 ASSERT(found_key.objectid < end);
 233                                 ASSERT(found_key.objectid + found_key.offset <= end);
 234
 235                                 first = div_u64(found_key.objectid - start,
 236                                                 fs_info->sectorsize);
 237                                 last = div_u64(found_key.objectid + found_key.offset - start,
 238                                                fs_info->sectorsize);
 239                                 le_bitmap_set(bitmap, first, last - first);
 240
 241                                 extent_count++;
 242                                 nr++;
 243                                 path->slots[0]--;
 244                         } else {
 245                                 ASSERT(0);
 246                         }
 247                 }
 248
 249                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
 250                 if (ret)
 251                         goto out;
 252                 btrfs_release_path(path);
 253         }
 254
 255         info = search_free_space_info(trans, fs_info, block_group, path, 1);
 256         if (IS_ERR(info)) {
 257                 ret = PTR_ERR(info);
 258                 goto out;
 259         }
 260         leaf = path->nodes[0];
 261         flags = btrfs_free_space_flags(leaf, info);
 262         flags |= BTRFS_FREE_SPACE_USING_BITMAPS;
 263         btrfs_set_free_space_flags(leaf, info, flags);
 264         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
 265         btrfs_mark_buffer_dirty(leaf);
 266         btrfs_release_path(path);
 267
 268         if (extent_count != expected_extent_count) {
 269                 btrfs_err(fs_info,
 270                           "incorrect extent count for %llu; counted %u, expected %u",
 271                           block_group->key.objectid, extent_count,
 272                           expected_extent_count);
 273                 ASSERT(0);
 274                 ret = -EIO;
 275                 goto out;
 276         }
 277
 278         bitmap_cursor = (char *)bitmap;
 279         bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
 280         i = start;
 281         while (i < end) {
 282                 unsigned long ptr;
 283                 u64 extent_size;
 284                 u32 data_size;
 285
 286                 extent_size = min(end - i, bitmap_range);
 287                 data_size = free_space_bitmap_size(extent_size,
 288                                                    fs_info->sectorsize);
 289
 290                 key.objectid = i;
 291                 key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
 292                 key.offset = extent_size;
 293
 294                 ret = btrfs_insert_empty_item(trans, root, path, &key,
 295                                               data_size);
 296                 if (ret)
 297                         goto out;
 298
 299                 leaf = path->nodes[0];
 300                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 301                 write_extent_buffer(leaf, bitmap_cursor, ptr,
 302                                     data_size);
 303                 btrfs_mark_buffer_dirty(leaf);
 304                 btrfs_release_path(path);
 305
 306                 i += extent_size;
 307                 bitmap_cursor += data_size;
 308         }
 309
 310         ret = 0;
 311 out:
 312         kvfree(bitmap);
 313         if (ret)
 314                 btrfs_abort_transaction(trans, ret);
 315         return ret;
 316 }
 317
 318 int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
 319                                   struct btrfs_block_group_cache *block_group,
 320                                   struct btrfs_path *path)
 321 {
 322         struct btrfs_fs_info *fs_info = trans->fs_info;
 323         struct btrfs_root *root = fs_info->free_space_root;
 324         struct btrfs_free_space_info *info;
 325         struct btrfs_key key, found_key;
 326         struct extent_buffer *leaf;
 327         unsigned long *bitmap;
 328         u64 start, end;
 329         u32 bitmap_size, flags, expected_extent_count;
 330         unsigned long nrbits, start_bit, end_bit;
 331         u32 extent_count = 0;
 332         int done = 0, nr;
 333         int ret;
 334
 335         bitmap_size = free_space_bitmap_size(block_group->key.offset,
 336                                              fs_info->sectorsize);
 337         bitmap = alloc_bitmap(bitmap_size);
 338         if (!bitmap) {
 339                 ret = -ENOMEM;
 340                 goto out;
 341         }
 342
 343         start = block_group->key.objectid;
 344         end = block_group->key.objectid + block_group->key.offset;
 345
 346         key.objectid = end - 1;
 347         key.type = (u8)-1;
 348         key.offset = (u64)-1;
 349
 350         while (!done) {
 351                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 352                 if (ret)
 353                         goto out;
 354
 355                 leaf = path->nodes[0];
 356                 nr = 0;
 357                 path->slots[0]++;
 358                 while (path->slots[0] > 0) {
 359                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 360
 361                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
 362                                 ASSERT(found_key.objectid == block_group->key.objectid);
 363                                 ASSERT(found_key.offset == block_group->key.offset);
 364                                 done = 1;
 365                                 break;
 366                         } else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
 367                                 unsigned long ptr;
 368                                 char *bitmap_cursor;
 369                                 u32 bitmap_pos, data_size;
 370
 371                                 ASSERT(found_key.objectid >= start);
 372                                 ASSERT(found_key.objectid < end);
 373                                 ASSERT(found_key.objectid + found_key.offset <= end);
 374
 375                                 bitmap_pos = div_u64(found_key.objectid - start,
 376                                                      fs_info->sectorsize *
 377                                                      BITS_PER_BYTE);
 378                                 bitmap_cursor = ((char *)bitmap) + bitmap_pos;
 379                                 data_size = free_space_bitmap_size(found_key.offset,
 380                                                                    fs_info->sectorsize);
 381
 382                                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
 383                                 read_extent_buffer(leaf, bitmap_cursor, ptr,
 384                                                    data_size);
 385
 386                                 nr++;
 387                                 path->slots[0]--;
 388                         } else {
 389                                 ASSERT(0);
 390                         }
 391                 }
 392
 393                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
 394                 if (ret)
 395                         goto out;
 396                 btrfs_release_path(path);
 397         }
 398
 399         info = search_free_space_info(trans, fs_info, block_group, path, 1);
 400         if (IS_ERR(info)) {
 401                 ret = PTR_ERR(info);
 402                 goto out;
 403         }
 404         leaf = path->nodes[0];
 405         flags = btrfs_free_space_flags(leaf, info);
 406         flags &= ~BTRFS_FREE_SPACE_USING_BITMAPS;
 407         btrfs_set_free_space_flags(leaf, info, flags);
 408         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
 409         btrfs_mark_buffer_dirty(leaf);
 410         btrfs_release_path(path);
 411
 412         nrbits = div_u64(block_group->key.offset, block_group->fs_info->sectorsize);
 413         start_bit = find_next_bit_le(bitmap, nrbits, 0);
 414
 415         while (start_bit < nrbits) {
 416                 end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
 417                 ASSERT(start_bit < end_bit);
 418
 419                 key.objectid = start + start_bit * block_group->fs_info->sectorsize;
 420                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 421                 key.offset = (end_bit - start_bit) * block_group->fs_info->sectorsize;
 422
 423                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 424                 if (ret)
 425                         goto out;
 426                 btrfs_release_path(path);
 427
 428                 extent_count++;
 429
 430                 start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
 431         }
 432
 433         if (extent_count != expected_extent_count) {
 434                 btrfs_err(fs_info,
 435                           "incorrect extent count for %llu; counted %u, expected %u",
 436                           block_group->key.objectid, extent_count,
 437                           expected_extent_count);
 438                 ASSERT(0);
 439                 ret = -EIO;
 440                 goto out;
 441         }
 442
 443         ret = 0;
 444 out:
 445         kvfree(bitmap);
 446         if (ret)
 447                 btrfs_abort_transaction(trans, ret);
 448         return ret;
 449 }
 450
 451 static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
 452                                           struct btrfs_block_group_cache *block_group,
 453                                           struct btrfs_path *path,
 454                                           int new_extents)
 455 {
 456         struct btrfs_free_space_info *info;
 457         u32 flags;
 458         u32 extent_count;
 459         int ret = 0;
 460
 461         if (new_extents == 0)
 462                 return 0;
 463
 464         info = search_free_space_info(trans, trans->fs_info, block_group, path,
 465                                       1);
 466         if (IS_ERR(info)) {
 467                 ret = PTR_ERR(info);
 468                 goto out;
 469         }
 470         flags = btrfs_free_space_flags(path->nodes[0], info);
 471         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
 472
 473         extent_count += new_extents;
 474         btrfs_set_free_space_extent_count(path->nodes[0], info, extent_count);
 475         btrfs_mark_buffer_dirty(path->nodes[0]);
 476         btrfs_release_path(path);
 477
 478         if (!(flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 479             extent_count > block_group->bitmap_high_thresh) {
 480                 ret = convert_free_space_to_bitmaps(trans, block_group, path);
 481         } else if ((flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 482                    extent_count < block_group->bitmap_low_thresh) {
 483                 ret = convert_free_space_to_extents(trans, block_group, path);
 484         }
 485
 486 out:
 487         return ret;
 488 }
 489
 490 int free_space_test_bit(struct btrfs_block_group_cache *block_group,
 491                         struct btrfs_path *path, u64 offset)
 492 {
 493         struct extent_buffer *leaf;
 494         struct btrfs_key key;
 495         u64 found_start, found_end;
 496         unsigned long ptr, i;
 497
 498         leaf = path->nodes[0];
 499         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 500         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 501
 502         found_start = key.objectid;
 503         found_end = key.objectid + key.offset;
 504         ASSERT(offset >= found_start && offset < found_end);
 505
 506         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 507         i = div_u64(offset - found_start,
 508                     block_group->fs_info->sectorsize);
 509         return !!extent_buffer_test_bit(leaf, ptr, i);
 510 }
 511
 512 static void free_space_set_bits(struct btrfs_block_group_cache *block_group,
 513                                 struct btrfs_path *path, u64 *start, u64 *size,
 514                                 int bit)
 515 {
 516         struct btrfs_fs_info *fs_info = block_group->fs_info;
 517         struct extent_buffer *leaf;
 518         struct btrfs_key key;
 519         u64 end = *start + *size;
 520         u64 found_start, found_end;
 521         unsigned long ptr, first, last;
 522
 523         leaf = path->nodes[0];
 524         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 525         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 526
 527         found_start = key.objectid;
 528         found_end = key.objectid + key.offset;
 529         ASSERT(*start >= found_start && *start < found_end);
 530         ASSERT(end > found_start);
 531
 532         if (end > found_end)
 533                 end = found_end;
 534
 535         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 536         first = div_u64(*start - found_start, fs_info->sectorsize);
 537         last = div_u64(end - found_start, fs_info->sectorsize);
 538         if (bit)
 539                 extent_buffer_bitmap_set(leaf, ptr, first, last - first);
 540         else
 541                 extent_buffer_bitmap_clear(leaf, ptr, first, last - first);
 542         btrfs_mark_buffer_dirty(leaf);
 543
 544         *size -= end - *start;
 545         *start = end;
 546 }
 547
 548 /*
 549  * We can't use btrfs_next_item() in modify_free_space_bitmap() because
 550  * btrfs_next_leaf() doesn't get the path for writing. We can forgo the fancy
 551  * tree walking in btrfs_next_leaf() anyways because we know exactly what we're
 552  * looking for.
 553  */
 554 static int free_space_next_bitmap(struct btrfs_trans_handle *trans,
 555                                   struct btrfs_root *root, struct btrfs_path *p)
 556 {
 557         struct btrfs_key key;
 558
 559         if (p->slots[0] + 1 < btrfs_header_nritems(p->nodes[0])) {
 560                 p->slots[0]++;
 561                 return 0;
 562         }
 563
 564         btrfs_item_key_to_cpu(p->nodes[0], &key, p->slots[0]);
 565         btrfs_release_path(p);
 566
 567         key.objectid += key.offset;
 568         key.type = (u8)-1;
 569         key.offset = (u64)-1;
 570
 571         return btrfs_search_prev_slot(trans, root, &key, p, 0, 1);
 572 }
 573
 574 /*
 575  * If remove is 1, then we are removing free space, thus clearing bits in the
 576  * bitmap. If remove is 0, then we are adding free space, thus setting bits in
 577  * the bitmap.
 578  */
 579 static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 580                                     struct btrfs_fs_info *fs_info,
 581                                     struct btrfs_block_group_cache *block_group,
 582                                     struct btrfs_path *path,
 583                                     u64 start, u64 size, int remove)
 584 {
 585         struct btrfs_root *root = fs_info->free_space_root;
 586         struct btrfs_key key;
 587         u64 end = start + size;
 588         u64 cur_start, cur_size;
 589         int prev_bit, next_bit;
 590         int new_extents;
 591         int ret;
 592
 593         /*
 594          * Read the bit for the block immediately before the extent of space if
 595          * that block is within the block group.
 596          */
 597         if (start > block_group->key.objectid) {
 598                 u64 prev_block = start - block_group->fs_info->sectorsize;
 599
 600                 key.objectid = prev_block;
 601                 key.type = (u8)-1;
 602                 key.offset = (u64)-1;
 603
 604                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 605                 if (ret)
 606                         goto out;
 607
 608                 prev_bit = free_space_test_bit(block_group, path, prev_block);
 609
 610                 /* The previous block may have been in the previous bitmap. */
 611                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 612                 if (start >= key.objectid + key.offset) {
 613                         ret = free_space_next_bitmap(trans, root, path);
 614                         if (ret)
 615                                 goto out;
 616                 }
 617         } else {
 618                 key.objectid = start;
 619                 key.type = (u8)-1;
 620                 key.offset = (u64)-1;
 621
 622                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 623                 if (ret)
 624                         goto out;
 625
 626                 prev_bit = -1;
 627         }
 628
 629         /*
 630          * Iterate over all of the bitmaps overlapped by the extent of space,
 631          * clearing/setting bits as required.
 632          */
 633         cur_start = start;
 634         cur_size = size;
 635         while (1) {
 636                 free_space_set_bits(block_group, path, &cur_start, &cur_size,
 637                                     !remove);
 638                 if (cur_size == 0)
 639                         break;
 640                 ret = free_space_next_bitmap(trans, root, path);
 641                 if (ret)
 642                         goto out;
 643         }
 644
 645         /*
 646          * Read the bit for the block immediately after the extent of space if
 647          * that block is within the block group.
 648          */
 649         if (end < block_group->key.objectid + block_group->key.offset) {
 650                 /* The next block may be in the next bitmap. */
 651                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 652                 if (end >= key.objectid + key.offset) {
 653                         ret = free_space_next_bitmap(trans, root, path);
 654                         if (ret)
 655                                 goto out;
 656                 }
 657
 658                 next_bit = free_space_test_bit(block_group, path, end);
 659         } else {
 660                 next_bit = -1;
 661         }
 662
 663         if (remove) {
 664                 new_extents = -1;
 665                 if (prev_bit == 1) {
 666                         /* Leftover on the left. */
 667                         new_extents++;
 668                 }
 669                 if (next_bit == 1) {
 670                         /* Leftover on the right. */
 671                         new_extents++;
 672                 }
 673         } else {
 674                 new_extents = 1;
 675                 if (prev_bit == 1) {
 676                         /* Merging with neighbor on the left. */
 677                         new_extents--;
 678                 }
 679                 if (next_bit == 1) {
 680                         /* Merging with neighbor on the right. */
 681                         new_extents--;
 682                 }
 683         }
 684
 685         btrfs_release_path(path);
 686         ret = update_free_space_extent_count(trans, block_group, path,
 687                                              new_extents);
 688
 689 out:
 690         return ret;
 691 }
 692
 693 static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 694                                     struct btrfs_fs_info *fs_info,
 695                                     struct btrfs_block_group_cache *block_group,
 696                                     struct btrfs_path *path,
 697                                     u64 start, u64 size)
 698 {
 699         struct btrfs_root *root = fs_info->free_space_root;
 700         struct btrfs_key key;
 701         u64 found_start, found_end;
 702         u64 end = start + size;
 703         int new_extents = -1;
 704         int ret;
 705
 706         key.objectid = start;
 707         key.type = (u8)-1;
 708         key.offset = (u64)-1;
 709
 710         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 711         if (ret)
 712                 goto out;
 713
 714         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 715
 716         ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
 717
 718         found_start = key.objectid;
 719         found_end = key.objectid + key.offset;
 720         ASSERT(start >= found_start && end <= found_end);
 721
 722         /*
 723          * Okay, now that we've found the free space extent which contains the
 724          * free space that we are removing, there are four cases:
 725          *
 726          * 1. We're using the whole extent: delete the key we found and
 727          * decrement the free space extent count.
 728          * 2. We are using part of the extent starting at the beginning: delete
 729          * the key we found and insert a new key representing the leftover at
 730          * the end. There is no net change in the number of extents.
 731          * 3. We are using part of the extent ending at the end: delete the key
 732          * we found and insert a new key representing the leftover at the
 733          * beginning. There is no net change in the number of extents.
 734          * 4. We are using part of the extent in the middle: delete the key we
 735          * found and insert two new keys representing the leftovers on each
 736          * side. Where we used to have one extent, we now have two, so increment
 737          * the extent count. We may need to convert the block group to bitmaps
 738          * as a result.
 739          */
 740
 741         /* Delete the existing key (cases 1-4). */
 742         ret = btrfs_del_item(trans, root, path);
 743         if (ret)
 744                 goto out;
 745
 746         /* Add a key for leftovers at the beginning (cases 3 and 4). */
 747         if (start > found_start) {
 748                 key.objectid = found_start;
 749                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 750                 key.offset = start - found_start;
 751
 752                 btrfs_release_path(path);
 753                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 754                 if (ret)
 755                         goto out;
 756                 new_extents++;
 757         }
 758
 759         /* Add a key for leftovers at the end (cases 2 and 4). */
 760         if (end < found_end) {
 761                 key.objectid = end;
 762                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 763                 key.offset = found_end - end;
 764
 765                 btrfs_release_path(path);
 766                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 767                 if (ret)
 768                         goto out;
 769                 new_extents++;
 770         }
 771
 772         btrfs_release_path(path);
 773         ret = update_free_space_extent_count(trans, block_group, path,
 774                                              new_extents);
 775
 776 out:
 777         return ret;
 778 }
 779
 780 int __remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 781                                   struct btrfs_fs_info *fs_info,
 782                                   struct btrfs_block_group_cache *block_group,
 783                                   struct btrfs_path *path, u64 start, u64 size)
 784 {
 785         struct btrfs_free_space_info *info;
 786         u32 flags;
 787         int ret;
 788
 789         if (block_group->needs_free_space) {
 790                 ret = __add_block_group_free_space(trans, block_group, path);
 791                 if (ret)
 792                         return ret;
 793         }
 794
 795         info = search_free_space_info(NULL, fs_info, block_group, path, 0);
 796         if (IS_ERR(info))
 797                 return PTR_ERR(info);
 798         flags = btrfs_free_space_flags(path->nodes[0], info);
 799         btrfs_release_path(path);
 800
 801         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
 802                 return modify_free_space_bitmap(trans, fs_info, block_group,
 803                                                 path, start, size, 1);
 804         } else {
 805                 return remove_free_space_extent(trans, fs_info, block_group,
 806                                                 path, start, size);
 807         }
 808 }
 809
 810 int remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 811                                 struct btrfs_fs_info *fs_info,
 812                                 u64 start, u64 size)
 813 {
 814         struct btrfs_block_group_cache *block_group;
 815         struct btrfs_path *path;
 816         int ret;
 817
 818         if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
 819                 return 0;
 820
 821         path = btrfs_alloc_path();
 822         if (!path) {
 823                 ret = -ENOMEM;
 824                 goto out;
 825         }
 826
 827         block_group = btrfs_lookup_block_group(fs_info, start);
 828         if (!block_group) {
 829                 ASSERT(0);
 830                 ret = -ENOENT;
 831                 goto out;
 832         }
 833
 834         mutex_lock(&block_group->free_space_lock);
 835         ret = __remove_from_free_space_tree(trans, fs_info, block_group, path,
 836                                             start, size);
 837         mutex_unlock(&block_group->free_space_lock);
 838
 839         btrfs_put_block_group(block_group);
 840 out:
 841         btrfs_free_path(path);
 842         if (ret)
 843                 btrfs_abort_transaction(trans, ret);
 844         return ret;
 845 }
 846
 847 static int add_free_space_extent(struct btrfs_trans_handle *trans,
 848                                  struct btrfs_fs_info *fs_info,
 849                                  struct btrfs_block_group_cache *block_group,
 850                                  struct btrfs_path *path,
 851                                  u64 start, u64 size)
 852 {
 853         struct btrfs_root *root = fs_info->free_space_root;
 854         struct btrfs_key key, new_key;
 855         u64 found_start, found_end;
 856         u64 end = start + size;
 857         int new_extents = 1;
 858         int ret;
 859
 860         /*
 861          * We are adding a new extent of free space, but we need to merge
 862          * extents. There are four cases here:
 863          *
 864          * 1. The new extent does not have any immediate neighbors to merge
 865          * with: add the new key and increment the free space extent count. We
 866          * may need to convert the block group to bitmaps as a result.
 867          * 2. The new extent has an immediate neighbor before it: remove the
 868          * previous key and insert a new key combining both of them. There is no
 869          * net change in the number of extents.
 870          * 3. The new extent has an immediate neighbor after it: remove the next
 871          * key and insert a new key combining both of them. There is no net
 872          * change in the number of extents.
 873          * 4. The new extent has immediate neighbors on both sides: remove both
 874          * of the keys and insert a new key combining all of them. Where we used
 875          * to have two extents, we now have one, so decrement the extent count.
 876          */
 877
 878         new_key.objectid = start;
 879         new_key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 880         new_key.offset = size;
 881
 882         /* Search for a neighbor on the left. */
 883         if (start == block_group->key.objectid)
 884                 goto right;
 885         key.objectid = start - 1;
 886         key.type = (u8)-1;
 887         key.offset = (u64)-1;
 888
 889         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 890         if (ret)
 891                 goto out;
 892
 893         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 894
 895         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
 896                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
 897                 btrfs_release_path(path);
 898                 goto right;
 899         }
 900
 901         found_start = key.objectid;
 902         found_end = key.objectid + key.offset;
 903         ASSERT(found_start >= block_group->key.objectid &&
 904                found_end > block_group->key.objectid);
 905         ASSERT(found_start < start && found_end <= start);
 906
 907         /*
 908          * Delete the neighbor on the left and absorb it into the new key (cases
 909          * 2 and 4).
 910          */
 911         if (found_end == start) {
 912                 ret = btrfs_del_item(trans, root, path);
 913                 if (ret)
 914                         goto out;
 915                 new_key.objectid = found_start;
 916                 new_key.offset += key.offset;
 917                 new_extents--;
 918         }
 919         btrfs_release_path(path);
 920
 921 right:
 922         /* Search for a neighbor on the right. */
 923         if (end == block_group->key.objectid + block_group->key.offset)
 924                 goto insert;
 925         key.objectid = end;
 926         key.type = (u8)-1;
 927         key.offset = (u64)-1;
 928
 929         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 930         if (ret)
 931                 goto out;
 932
 933         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 934
 935         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
 936                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
 937                 btrfs_release_path(path);
 938                 goto insert;
 939         }
 940
 941         found_start = key.objectid;
 942         found_end = key.objectid + key.offset;
 943         ASSERT(found_start >= block_group->key.objectid &&
 944                found_end > block_group->key.objectid);
 945         ASSERT((found_start < start && found_end <= start) ||
 946                (found_start >= end && found_end > end));
 947
 948         /*
 949          * Delete the neighbor on the right and absorb it into the new key
 950          * (cases 3 and 4).
 951          */
 952         if (found_start == end) {
 953                 ret = btrfs_del_item(trans, root, path);
 954                 if (ret)
 955                         goto out;
 956                 new_key.offset += key.offset;
 957                 new_extents--;
 958         }
 959         btrfs_release_path(path);
 960
 961 insert:
 962         /* Insert the new key (cases 1-4). */
 963         ret = btrfs_insert_empty_item(trans, root, path, &new_key, 0);
 964         if (ret)
 965                 goto out;
 966
 967         btrfs_release_path(path);
 968         ret = update_free_space_extent_count(trans, block_group, path,
 969                                              new_extents);
 970
 971 out:
 972         return ret;
 973 }
 974
 975 int __add_to_free_space_tree(struct btrfs_trans_handle *trans,
 976                              struct btrfs_block_group_cache *block_group,
 977                              struct btrfs_path *path, u64 start, u64 size)
 978 {
 979         struct btrfs_fs_info *fs_info = trans->fs_info;
 980         struct btrfs_free_space_info *info;
 981         u32 flags;
 982         int ret;
 983
 984         if (block_group->needs_free_space) {
 985                 ret = __add_block_group_free_space(trans, block_group, path);
 986                 if (ret)
 987                         return ret;
 988         }
 989
 990         info = search_free_space_info(NULL, fs_info, block_group, path, 0);
 991         if (IS_ERR(info))
 992                 return PTR_ERR(info);
 993         flags = btrfs_free_space_flags(path->nodes[0], info);
 994         btrfs_release_path(path);
 995
 996         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
 997                 return modify_free_space_bitmap(trans, fs_info, block_group,
 998                                                 path, start, size, 0);
 999         } else {
1000                 return add_free_space_extent(trans, fs_info, block_group, path,
1001                                              start, size);
1002         }
1003 }
1004
1005 int add_to_free_space_tree(struct btrfs_trans_handle *trans,
1006                            struct btrfs_fs_info *fs_info,
1007                            u64 start, u64 size)
1008 {
1009         struct btrfs_block_group_cache *block_group;
1010         struct btrfs_path *path;
1011         int ret;
1012
1013         if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
1014                 return 0;
1015
1016         path = btrfs_alloc_path();
1017         if (!path) {
1018                 ret = -ENOMEM;
1019                 goto out;
1020         }
1021
1022         block_group = btrfs_lookup_block_group(fs_info, start);
1023         if (!block_group) {
1024                 ASSERT(0);
1025                 ret = -ENOENT;
1026                 goto out;
1027         }
1028
1029         mutex_lock(&block_group->free_space_lock);
1030         ret = __add_to_free_space_tree(trans, block_group, path, start, size);
1031         mutex_unlock(&block_group->free_space_lock);
1032
1033         btrfs_put_block_group(block_group);
1034 out:
1035         btrfs_free_path(path);
1036         if (ret)
1037                 btrfs_abort_transaction(trans, ret);
1038         return ret;
1039 }
1040
1041 /*
1042  * Populate the free space tree by walking the extent tree. Operations on the
1043  * extent tree that happen as a result of writes to the free space tree will go
1044  * through the normal add/remove hooks.
1045  */
1046 static int populate_free_space_tree(struct btrfs_trans_handle *trans,
1047                                     struct btrfs_fs_info *fs_info,
1048                                     struct btrfs_block_group_cache *block_group)
1049 {
1050         struct btrfs_root *extent_root = fs_info->extent_root;
1051         struct btrfs_path *path, *path2;
1052         struct btrfs_key key;
1053         u64 start, end;
1054         int ret;
1055
1056         path = btrfs_alloc_path();
1057         if (!path)
1058                 return -ENOMEM;
1059         path->reada = READA_FORWARD;
1060
1061         path2 = btrfs_alloc_path();
1062         if (!path2) {
1063                 btrfs_free_path(path);
1064                 return -ENOMEM;
1065         }
1066
1067         ret = add_new_free_space_info(trans, block_group, path2);
1068         if (ret)
1069                 goto out;
1070
1071         mutex_lock(&block_group->free_space_lock);
1072
1073         /*
1074          * Iterate through all of the extent and metadata items in this block
1075          * group, adding the free space between them and the free space at the
1076          * end. Note that EXTENT_ITEM and METADATA_ITEM are less than
1077          * BLOCK_GROUP_ITEM, so an extent may precede the block group that it's
1078          * contained in.
1079          */
1080         key.objectid = block_group->key.objectid;
1081         key.type = BTRFS_EXTENT_ITEM_KEY;
1082         key.offset = 0;
1083
1084         ret = btrfs_search_slot_for_read(extent_root, &key, path, 1, 0);
1085         if (ret < 0)
1086                 goto out_locked;
1087         ASSERT(ret == 0);
1088
1089         start = block_group->key.objectid;
1090         end = block_group->key.objectid + block_group->key.offset;
1091         while (1) {
1092                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1093
1094                 if (key.type == BTRFS_EXTENT_ITEM_KEY ||
1095                     key.type == BTRFS_METADATA_ITEM_KEY) {
1096                         if (key.objectid >= end)
1097                                 break;
1098
1099                         if (start < key.objectid) {
1100                                 ret = __add_to_free_space_tree(trans,
1101                                                                block_group,
1102                                                                path2, start,
1103                                                                key.objectid -
1104                                                                start);
1105                                 if (ret)
1106                                         goto out_locked;
1107                         }
1108                         start = key.objectid;
1109                         if (key.type == BTRFS_METADATA_ITEM_KEY)
1110                                 start += fs_info->nodesize;
1111                         else
1112                                 start += key.offset;
1113                 } else if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
1114                         if (key.objectid != block_group->key.objectid)
1115                                 break;
1116                 }
1117
1118                 ret = btrfs_next_item(extent_root, path);
1119                 if (ret < 0)
1120                         goto out_locked;
1121                 if (ret)
1122                         break;
1123         }
1124         if (start < end) {
1125                 ret = __add_to_free_space_tree(trans, block_group, path2,
1126                                                start, end - start);
1127                 if (ret)
1128                         goto out_locked;
1129         }
1130
1131         ret = 0;
1132 out_locked:
1133         mutex_unlock(&block_group->free_space_lock);
1134 out:
1135         btrfs_free_path(path2);
1136         btrfs_free_path(path);
1137         return ret;
1138 }
1139
1140 int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
1141 {
1142         struct btrfs_trans_handle *trans;
1143         struct btrfs_root *tree_root = fs_info->tree_root;
1144         struct btrfs_root *free_space_root;
1145         struct btrfs_block_group_cache *block_group;
1146         struct rb_node *node;
1147         int ret;
1148
1149         trans = btrfs_start_transaction(tree_root, 0);
1150         if (IS_ERR(trans))
1151                 return PTR_ERR(trans);
1152
1153         set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1154         free_space_root = btrfs_create_tree(trans, fs_info,
1155                                             BTRFS_FREE_SPACE_TREE_OBJECTID);
1156         if (IS_ERR(free_space_root)) {
1157                 ret = PTR_ERR(free_space_root);
1158                 goto abort;
1159         }
1160         fs_info->free_space_root = free_space_root;
1161
1162         node = rb_first(&fs_info->block_group_cache_tree);
1163         while (node) {
1164                 block_group = rb_entry(node, struct btrfs_block_group_cache,
1165                                        cache_node);
1166                 ret = populate_free_space_tree(trans, fs_info, block_group);
1167                 if (ret)
1168                         goto abort;
1169                 node = rb_next(node);
1170         }
1171
1172         btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1173         btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1174         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1175
1176         return btrfs_commit_transaction(trans);
1177
1178 abort:
1179         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1180         btrfs_abort_transaction(trans, ret);
1181         btrfs_end_transaction(trans);
1182         return ret;
1183 }
1184
1185 static int clear_free_space_tree(struct btrfs_trans_handle *trans,
1186                                  struct btrfs_root *root)
1187 {
1188         struct btrfs_path *path;
1189         struct btrfs_key key;
1190         int nr;
1191         int ret;
1192
1193         path = btrfs_alloc_path();
1194         if (!path)
1195                 return -ENOMEM;
1196
1197         path->leave_spinning = 1;
1198
1199         key.objectid = 0;
1200         key.type = 0;
1201         key.offset = 0;
1202
1203         while (1) {
1204                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
1205                 if (ret < 0)
1206                         goto out;
1207
1208                 nr = btrfs_header_nritems(path->nodes[0]);
1209                 if (!nr)
1210                         break;
1211
1212                 path->slots[0] = 0;
1213                 ret = btrfs_del_items(trans, root, path, 0, nr);
1214                 if (ret)
1215                         goto out;
1216
1217                 btrfs_release_path(path);
1218         }
1219
1220         ret = 0;
1221 out:
1222         btrfs_free_path(path);
1223         return ret;
1224 }
1225
1226 int btrfs_clear_free_space_tree(struct btrfs_fs_info *fs_info)
1227 {
1228         struct btrfs_trans_handle *trans;
1229         struct btrfs_root *tree_root = fs_info->tree_root;
1230         struct btrfs_root *free_space_root = fs_info->free_space_root;
1231         int ret;
1232
1233         trans = btrfs_start_transaction(tree_root, 0);
1234         if (IS_ERR(trans))
1235                 return PTR_ERR(trans);
1236
1237         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1238         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1239         fs_info->free_space_root = NULL;
1240
1241         ret = clear_free_space_tree(trans, free_space_root);
1242         if (ret)
1243                 goto abort;
1244
1245         ret = btrfs_del_root(trans, fs_info, &free_space_root->root_key);
1246         if (ret)
1247                 goto abort;
1248
1249         list_del(&free_space_root->dirty_list);
1250
1251         btrfs_tree_lock(free_space_root->node);
1252         clean_tree_block(fs_info, free_space_root->node);
1253         btrfs_tree_unlock(free_space_root->node);
1254         btrfs_free_tree_block(trans, free_space_root, free_space_root->node,
1255                               0, 1);
1256
1257         free_extent_buffer(free_space_root->node);
1258         free_extent_buffer(free_space_root->commit_root);
1259         kfree(free_space_root);
1260
1261         return btrfs_commit_transaction(trans);
1262
1263 abort:
1264         btrfs_abort_transaction(trans, ret);
1265         btrfs_end_transaction(trans);
1266         return ret;
1267 }
1268
1269 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
1270                                         struct btrfs_block_group_cache *block_group,
1271                                         struct btrfs_path *path)
1272 {
1273         int ret;
1274
1275         block_group->needs_free_space = 0;
1276
1277         ret = add_new_free_space_info(trans, block_group, path);
1278         if (ret)
1279                 return ret;
1280
1281         return __add_to_free_space_tree(trans, block_group, path,
1282                                         block_group->key.objectid,
1283                                         block_group->key.offset);
1284 }
1285
1286 int add_block_group_free_space(struct btrfs_trans_handle *trans,
1287                                struct btrfs_block_group_cache *block_group)
1288 {
1289         struct btrfs_fs_info *fs_info = trans->fs_info;
1290         struct btrfs_path *path = NULL;
1291         int ret = 0;
1292
1293         if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
1294                 return 0;
1295
1296         mutex_lock(&block_group->free_space_lock);
1297         if (!block_group->needs_free_space)
1298                 goto out;
1299
1300         path = btrfs_alloc_path();
1301         if (!path) {
1302                 ret = -ENOMEM;
1303                 goto out;
1304         }
1305
1306         ret = __add_block_group_free_space(trans, block_group, path);
1307
1308 out:
1309         btrfs_free_path(path);
1310         mutex_unlock(&block_group->free_space_lock);
1311         if (ret)
1312                 btrfs_abort_transaction(trans, ret);
1313         return ret;
1314 }
1315
1316 int remove_block_group_free_space(struct btrfs_trans_handle *trans,
1317                                   struct btrfs_block_group_cache *block_group)
1318 {
1319         struct btrfs_root *root = trans->fs_info->free_space_root;
1320         struct btrfs_path *path;
1321         struct btrfs_key key, found_key;
1322         struct extent_buffer *leaf;
1323         u64 start, end;
1324         int done = 0, nr;
1325         int ret;
1326
1327         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1328                 return 0;
1329
1330         if (block_group->needs_free_space) {
1331                 /* We never added this block group to the free space tree. */
1332                 return 0;
1333         }
1334
1335         path = btrfs_alloc_path();
1336         if (!path) {
1337                 ret = -ENOMEM;
1338                 goto out;
1339         }
1340
1341         start = block_group->key.objectid;
1342         end = block_group->key.objectid + block_group->key.offset;
1343
1344         key.objectid = end - 1;
1345         key.type = (u8)-1;
1346         key.offset = (u64)-1;
1347
1348         while (!done) {
1349                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
1350                 if (ret)
1351                         goto out;
1352
1353                 leaf = path->nodes[0];
1354                 nr = 0;
1355                 path->slots[0]++;
1356                 while (path->slots[0] > 0) {
1357                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
1358
1359                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
1360                                 ASSERT(found_key.objectid == block_group->key.objectid);
1361                                 ASSERT(found_key.offset == block_group->key.offset);
1362                                 done = 1;
1363                                 nr++;
1364                                 path->slots[0]--;
1365                                 break;
1366                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY ||
1367                                    found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
1368                                 ASSERT(found_key.objectid >= start);
1369                                 ASSERT(found_key.objectid < end);
1370                                 ASSERT(found_key.objectid + found_key.offset <= end);
1371                                 nr++;
1372                                 path->slots[0]--;
1373                         } else {
1374                                 ASSERT(0);
1375                         }
1376                 }
1377
1378                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
1379                 if (ret)
1380                         goto out;
1381                 btrfs_release_path(path);
1382         }
1383
1384         ret = 0;
1385 out:
1386         btrfs_free_path(path);
1387         if (ret)
1388                 btrfs_abort_transaction(trans, ret);
1389         return ret;
1390 }
1391
1392 static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
1393                                    struct btrfs_path *path,
1394                                    u32 expected_extent_count)
1395 {
1396         struct btrfs_block_group_cache *block_group;
1397         struct btrfs_fs_info *fs_info;
1398         struct btrfs_root *root;
1399         struct btrfs_key key;
1400         int prev_bit = 0, bit;
1401         /* Initialize to silence GCC. */
1402         u64 extent_start = 0;
1403         u64 end, offset;
1404         u64 total_found = 0;
1405         u32 extent_count = 0;
1406         int ret;
1407
1408         block_group = caching_ctl->block_group;
1409         fs_info = block_group->fs_info;
1410         root = fs_info->free_space_root;
1411
1412         end = block_group->key.objectid + block_group->key.offset;
1413
1414         while (1) {
1415                 ret = btrfs_next_item(root, path);
1416                 if (ret < 0)
1417                         goto out;
1418                 if (ret)
1419                         break;
1420
1421                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1422
1423                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1424                         break;
1425
1426                 ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
1427                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1428
1429                 caching_ctl->progress = key.objectid;
1430
1431                 offset = key.objectid;
1432                 while (offset < key.objectid + key.offset) {
1433                         bit = free_space_test_bit(block_group, path, offset);
1434                         if (prev_bit == 0 && bit == 1) {
1435                                 extent_start = offset;
1436                         } else if (prev_bit == 1 && bit == 0) {
1437                                 total_found += add_new_free_space(block_group,
1438                                                                   extent_start,
1439                                                                   offset);
1440                                 if (total_found > CACHING_CTL_WAKE_UP) {
1441                                         total_found = 0;
1442                                         wake_up(&caching_ctl->wait);
1443                                 }
1444                                 extent_count++;
1445                         }
1446                         prev_bit = bit;
1447                         offset += fs_info->sectorsize;
1448                 }
1449         }
1450         if (prev_bit == 1) {
1451                 total_found += add_new_free_space(block_group, extent_start,
1452                                                   end);
1453                 extent_count++;
1454         }
1455
1456         if (extent_count != expected_extent_count) {
1457                 btrfs_err(fs_info,
1458                           "incorrect extent count for %llu; counted %u, expected %u",
1459                           block_group->key.objectid, extent_count,
1460                           expected_extent_count);
1461                 ASSERT(0);
1462                 ret = -EIO;
1463                 goto out;
1464         }
1465
1466         caching_ctl->progress = (u64)-1;
1467
1468         ret = 0;
1469 out:
1470         return ret;
1471 }
1472
1473 static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
1474                                    struct btrfs_path *path,
1475                                    u32 expected_extent_count)
1476 {
1477         struct btrfs_block_group_cache *block_group;
1478         struct btrfs_fs_info *fs_info;
1479         struct btrfs_root *root;
1480         struct btrfs_key key;
1481         u64 end;
1482         u64 total_found = 0;
1483         u32 extent_count = 0;
1484         int ret;
1485
1486         block_group = caching_ctl->block_group;
1487         fs_info = block_group->fs_info;
1488         root = fs_info->free_space_root;
1489
1490         end = block_group->key.objectid + block_group->key.offset;
1491
1492         while (1) {
1493                 ret = btrfs_next_item(root, path);
1494                 if (ret < 0)
1495                         goto out;
1496                 if (ret)
1497                         break;
1498
1499                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1500
1501                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1502                         break;
1503
1504                 ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
1505                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1506
1507                 caching_ctl->progress = key.objectid;
1508
1509                 total_found += add_new_free_space(block_group, key.objectid,
1510                                                   key.objectid + key.offset);
1511                 if (total_found > CACHING_CTL_WAKE_UP) {
1512                         total_found = 0;
1513                         wake_up(&caching_ctl->wait);
1514                 }
1515                 extent_count++;
1516         }
1517
1518         if (extent_count != expected_extent_count) {
1519                 btrfs_err(fs_info,
1520                           "incorrect extent count for %llu; counted %u, expected %u",
1521                           block_group->key.objectid, extent_count,
1522                           expected_extent_count);
1523                 ASSERT(0);
1524                 ret = -EIO;
1525                 goto out;
1526         }
1527
1528         caching_ctl->progress = (u64)-1;
1529
1530         ret = 0;
1531 out:
1532         return ret;
1533 }
1534
1535 int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
1536 {
1537         struct btrfs_block_group_cache *block_group;
1538         struct btrfs_fs_info *fs_info;
1539         struct btrfs_free_space_info *info;
1540         struct btrfs_path *path;
1541         u32 extent_count, flags;
1542         int ret;
1543
1544         block_group = caching_ctl->block_group;
1545         fs_info = block_group->fs_info;
1546
1547         path = btrfs_alloc_path();
1548         if (!path)
1549                 return -ENOMEM;
1550
1551         /*
1552          * Just like caching_thread() doesn't want to deadlock on the extent
1553          * tree, we don't want to deadlock on the free space tree.
1554          */
1555         path->skip_locking = 1;
1556         path->search_commit_root = 1;
1557         path->reada = READA_FORWARD;
1558
1559         info = search_free_space_info(NULL, fs_info, block_group, path, 0);
1560         if (IS_ERR(info)) {
1561                 ret = PTR_ERR(info);
1562                 goto out;
1563         }
1564         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
1565         flags = btrfs_free_space_flags(path->nodes[0], info);
1566
1567         /*
1568          * We left path pointing to the free space info item, so now
1569          * load_free_space_foo can just iterate through the free space tree from
1570          * there.
1571          */
1572         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS)
1573                 ret = load_free_space_bitmaps(caching_ctl, path, extent_count);
1574         else
1575                 ret = load_free_space_extents(caching_ctl, path, extent_count);
1576
1577 out:
1578         btrfs_free_path(path);
1579         return ret;
1580 }