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