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