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_cache *block_group,
  17                                         struct btrfs_path *path);
  18
  19 void set_free_space_tree_thresholds(struct btrfs_block_group_cache *cache)
  20 {
  21         u32 bitmap_range;
  22         size_t bitmap_size;
  23         u64 num_bitmaps, total_bitmap_size;
  24
  25         /*
  26          * We convert to bitmaps when the disk space required for using extents
  27          * exceeds that required for using bitmaps.
  28          */
  29         bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
  30         num_bitmaps = div_u64(cache->key.offset + bitmap_range - 1,
  31                               bitmap_range);
  32         bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
  33         total_bitmap_size = num_bitmaps * bitmap_size;
  34         cache->bitmap_high_thresh = div_u64(total_bitmap_size,
  35                                             sizeof(struct btrfs_item));
  36
  37         /*
  38          * We allow for a small buffer between the high threshold and low
  39          * threshold to avoid thrashing back and forth between the two formats.
  40          */
  41         if (cache->bitmap_high_thresh > 100)
  42                 cache->bitmap_low_thresh = cache->bitmap_high_thresh - 100;
  43         else
  44                 cache->bitmap_low_thresh = 0;
  45 }
  46
  47 static int add_new_free_space_info(struct btrfs_trans_handle *trans,
  48                                    struct btrfs_block_group_cache *block_group,
  49                                    struct btrfs_path *path)
  50 {
  51         struct btrfs_root *root = trans->fs_info->free_space_root;
  52         struct btrfs_free_space_info *info;
  53         struct btrfs_key key;
  54         struct extent_buffer *leaf;
  55         int ret;
  56
  57         key.objectid = block_group->key.objectid;
  58         key.type = BTRFS_FREE_SPACE_INFO_KEY;
  59         key.offset = block_group->key.offset;
  60
  61         ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
  62         if (ret)
  63                 goto out;
  64
  65         leaf = path->nodes[0];
  66         info = btrfs_item_ptr(leaf, path->slots[0],
  67                               struct btrfs_free_space_info);
  68         btrfs_set_free_space_extent_count(leaf, info, 0);
  69         btrfs_set_free_space_flags(leaf, info, 0);
  70         btrfs_mark_buffer_dirty(leaf);
  71
  72         ret = 0;
  73 out:
  74         btrfs_release_path(path);
  75         return ret;
  76 }
  77
  78 EXPORT_FOR_TESTS
  79 struct btrfs_free_space_info *search_free_space_info(
  80                 struct btrfs_trans_handle *trans,
  81                 struct btrfs_block_group_cache *block_group,
  82                 struct btrfs_path *path, int cow)
  83 {
  84         struct btrfs_fs_info *fs_info = block_group->fs_info;
  85         struct btrfs_root *root = fs_info->free_space_root;
  86         struct btrfs_key key;
  87         int ret;
  88
  89         key.objectid = block_group->key.objectid;
  90         key.type = BTRFS_FREE_SPACE_INFO_KEY;
  91         key.offset = block_group->key.offset;
  92
  93         ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
  94         if (ret < 0)
  95                 return ERR_PTR(ret);
  96         if (ret != 0) {
  97                 btrfs_warn(fs_info, "missing free space info for %llu",
  98                            block_group->key.objectid);
  99                 ASSERT(0);
 100                 return ERR_PTR(-ENOENT);
 101         }
 102
 103         return btrfs_item_ptr(path->nodes[0], path->slots[0],
 104                               struct btrfs_free_space_info);
 105 }
 106
 107 /*
 108  * btrfs_search_slot() but we're looking for the greatest key less than the
 109  * passed key.
 110  */
 111 static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
 112                                   struct btrfs_root *root,
 113                                   struct btrfs_key *key, struct btrfs_path *p,
 114                                   int ins_len, int cow)
 115 {
 116         int ret;
 117
 118         ret = btrfs_search_slot(trans, root, key, p, ins_len, cow);
 119         if (ret < 0)
 120                 return ret;
 121
 122         if (ret == 0) {
 123                 ASSERT(0);
 124                 return -EIO;
 125         }
 126
 127         if (p->slots[0] == 0) {
 128                 ASSERT(0);
 129                 return -EIO;
 130         }
 131         p->slots[0]--;
 132
 133         return 0;
 134 }
 135
 136 static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
 137 {
 138         return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
 139 }
 140
 141 static unsigned long *alloc_bitmap(u32 bitmap_size)
 142 {
 143         unsigned long *ret;
 144         unsigned int nofs_flag;
 145         u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));
 146
 147         /*
 148          * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
 149          * into the filesystem as the free space bitmap can be modified in the
 150          * critical section of a transaction commit.
 151          *
 152          * TODO: push the memalloc_nofs_{save,restore}() to the caller where we
 153          * know that recursion is unsafe.
 154          */
 155         nofs_flag = memalloc_nofs_save();
 156         ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
 157         memalloc_nofs_restore(nofs_flag);
 158         return ret;
 159 }
 160
 161 static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
 162 {
 163         u8 *p = ((u8 *)map) + BIT_BYTE(start);
 164         const unsigned int size = start + len;
 165         int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
 166         u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
 167
 168         while (len - bits_to_set >= 0) {
 169                 *p |= mask_to_set;
 170                 len -= bits_to_set;
 171                 bits_to_set = BITS_PER_BYTE;
 172                 mask_to_set = ~0;
 173                 p++;
 174         }
 175         if (len) {
 176                 mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
 177                 *p |= mask_to_set;
 178         }
 179 }
 180
 181 EXPORT_FOR_TESTS
 182 int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 183                                   struct btrfs_block_group_cache *block_group,
 184                                   struct btrfs_path *path)
 185 {
 186         struct btrfs_fs_info *fs_info = trans->fs_info;
 187         struct btrfs_root *root = fs_info->free_space_root;
 188         struct btrfs_free_space_info *info;
 189         struct btrfs_key key, found_key;
 190         struct extent_buffer *leaf;
 191         unsigned long *bitmap;
 192         char *bitmap_cursor;
 193         u64 start, end;
 194         u64 bitmap_range, i;
 195         u32 bitmap_size, flags, expected_extent_count;
 196         u32 extent_count = 0;
 197         int done = 0, nr;
 198         int ret;
 199
 200         bitmap_size = free_space_bitmap_size(block_group->key.offset,
 201                                              fs_info->sectorsize);
 202         bitmap = alloc_bitmap(bitmap_size);
 203         if (!bitmap) {
 204                 ret = -ENOMEM;
 205                 goto out;
 206         }
 207
 208         start = block_group->key.objectid;
 209         end = block_group->key.objectid + block_group->key.offset;
 210
 211         key.objectid = end - 1;
 212         key.type = (u8)-1;
 213         key.offset = (u64)-1;
 214
 215         while (!done) {
 216                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 217                 if (ret)
 218                         goto out;
 219
 220                 leaf = path->nodes[0];
 221                 nr = 0;
 222                 path->slots[0]++;
 223                 while (path->slots[0] > 0) {
 224                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 225
 226                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
 227                                 ASSERT(found_key.objectid == block_group->key.objectid);
 228                                 ASSERT(found_key.offset == block_group->key.offset);
 229                                 done = 1;
 230                                 break;
 231                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY) {
 232                                 u64 first, last;
 233
 234                                 ASSERT(found_key.objectid >= start);
 235                                 ASSERT(found_key.objectid < end);
 236                                 ASSERT(found_key.objectid + found_key.offset <= end);
 237
 238                                 first = div_u64(found_key.objectid - start,
 239                                                 fs_info->sectorsize);
 240                                 last = div_u64(found_key.objectid + found_key.offset - start,
 241                                                fs_info->sectorsize);
 242                                 le_bitmap_set(bitmap, first, last - first);
 243
 244                                 extent_count++;
 245                                 nr++;
 246                                 path->slots[0]--;
 247                         } else {
 248                                 ASSERT(0);
 249                         }
 250                 }
 251
 252                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
 253                 if (ret)
 254                         goto out;
 255                 btrfs_release_path(path);
 256         }
 257
 258         info = search_free_space_info(trans, block_group, path, 1);
 259         if (IS_ERR(info)) {
 260                 ret = PTR_ERR(info);
 261                 goto out;
 262         }
 263         leaf = path->nodes[0];
 264         flags = btrfs_free_space_flags(leaf, info);
 265         flags |= BTRFS_FREE_SPACE_USING_BITMAPS;
 266         btrfs_set_free_space_flags(leaf, info, flags);
 267         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
 268         btrfs_mark_buffer_dirty(leaf);
 269         btrfs_release_path(path);
 270
 271         if (extent_count != expected_extent_count) {
 272                 btrfs_err(fs_info,
 273                           "incorrect extent count for %llu; counted %u, expected %u",
 274                           block_group->key.objectid, extent_count,
 275                           expected_extent_count);
 276                 ASSERT(0);
 277                 ret = -EIO;
 278                 goto out;
 279         }
 280
 281         bitmap_cursor = (char *)bitmap;
 282         bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
 283         i = start;
 284         while (i < end) {
 285                 unsigned long ptr;
 286                 u64 extent_size;
 287                 u32 data_size;
 288
 289                 extent_size = min(end - i, bitmap_range);
 290                 data_size = free_space_bitmap_size(extent_size,
 291                                                    fs_info->sectorsize);
 292
 293                 key.objectid = i;
 294                 key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
 295                 key.offset = extent_size;
 296
 297                 ret = btrfs_insert_empty_item(trans, root, path, &key,
 298                                               data_size);
 299                 if (ret)
 300                         goto out;
 301
 302                 leaf = path->nodes[0];
 303                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 304                 write_extent_buffer(leaf, bitmap_cursor, ptr,
 305                                     data_size);
 306                 btrfs_mark_buffer_dirty(leaf);
 307                 btrfs_release_path(path);
 308
 309                 i += extent_size;
 310                 bitmap_cursor += data_size;
 311         }
 312
 313         ret = 0;
 314 out:
 315         kvfree(bitmap);
 316         if (ret)
 317                 btrfs_abort_transaction(trans, ret);
 318         return ret;
 319 }
 320
 321 EXPORT_FOR_TESTS
 322 int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
 323                                   struct btrfs_block_group_cache *block_group,
 324                                   struct btrfs_path *path)
 325 {
 326         struct btrfs_fs_info *fs_info = trans->fs_info;
 327         struct btrfs_root *root = fs_info->free_space_root;
 328         struct btrfs_free_space_info *info;
 329         struct btrfs_key key, found_key;
 330         struct extent_buffer *leaf;
 331         unsigned long *bitmap;
 332         u64 start, end;
 333         u32 bitmap_size, flags, expected_extent_count;
 334         unsigned long nrbits, start_bit, end_bit;
 335         u32 extent_count = 0;
 336         int done = 0, nr;
 337         int ret;
 338
 339         bitmap_size = free_space_bitmap_size(block_group->key.offset,
 340                                              fs_info->sectorsize);
 341         bitmap = alloc_bitmap(bitmap_size);
 342         if (!bitmap) {
 343                 ret = -ENOMEM;
 344                 goto out;
 345         }
 346
 347         start = block_group->key.objectid;
 348         end = block_group->key.objectid + block_group->key.offset;
 349
 350         key.objectid = end - 1;
 351         key.type = (u8)-1;
 352         key.offset = (u64)-1;
 353
 354         while (!done) {
 355                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 356                 if (ret)
 357                         goto out;
 358
 359                 leaf = path->nodes[0];
 360                 nr = 0;
 361                 path->slots[0]++;
 362                 while (path->slots[0] > 0) {
 363                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 364
 365                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
 366                                 ASSERT(found_key.objectid == block_group->key.objectid);
 367                                 ASSERT(found_key.offset == block_group->key.offset);
 368                                 done = 1;
 369                                 break;
 370                         } else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
 371                                 unsigned long ptr;
 372                                 char *bitmap_cursor;
 373                                 u32 bitmap_pos, data_size;
 374
 375                                 ASSERT(found_key.objectid >= start);
 376                                 ASSERT(found_key.objectid < end);
 377                                 ASSERT(found_key.objectid + found_key.offset <= end);
 378
 379                                 bitmap_pos = div_u64(found_key.objectid - start,
 380                                                      fs_info->sectorsize *
 381                                                      BITS_PER_BYTE);
 382                                 bitmap_cursor = ((char *)bitmap) + bitmap_pos;
 383                                 data_size = free_space_bitmap_size(found_key.offset,
 384                                                                    fs_info->sectorsize);
 385
 386                                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
 387                                 read_extent_buffer(leaf, bitmap_cursor, ptr,
 388                                                    data_size);
 389
 390                                 nr++;
 391                                 path->slots[0]--;
 392                         } else {
 393                                 ASSERT(0);
 394                         }
 395                 }
 396
 397                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
 398                 if (ret)
 399                         goto out;
 400                 btrfs_release_path(path);
 401         }
 402
 403         info = search_free_space_info(trans, block_group, path, 1);
 404         if (IS_ERR(info)) {
 405                 ret = PTR_ERR(info);
 406                 goto out;
 407         }
 408         leaf = path->nodes[0];
 409         flags = btrfs_free_space_flags(leaf, info);
 410         flags &= ~BTRFS_FREE_SPACE_USING_BITMAPS;
 411         btrfs_set_free_space_flags(leaf, info, flags);
 412         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
 413         btrfs_mark_buffer_dirty(leaf);
 414         btrfs_release_path(path);
 415
 416         nrbits = div_u64(block_group->key.offset, block_group->fs_info->sectorsize);
 417         start_bit = find_next_bit_le(bitmap, nrbits, 0);
 418
 419         while (start_bit < nrbits) {
 420                 end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
 421                 ASSERT(start_bit < end_bit);
 422
 423                 key.objectid = start + start_bit * block_group->fs_info->sectorsize;
 424                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 425                 key.offset = (end_bit - start_bit) * block_group->fs_info->sectorsize;
 426
 427                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 428                 if (ret)
 429                         goto out;
 430                 btrfs_release_path(path);
 431
 432                 extent_count++;
 433
 434                 start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
 435         }
 436
 437         if (extent_count != expected_extent_count) {
 438                 btrfs_err(fs_info,
 439                           "incorrect extent count for %llu; counted %u, expected %u",
 440                           block_group->key.objectid, extent_count,
 441                           expected_extent_count);
 442                 ASSERT(0);
 443                 ret = -EIO;
 444                 goto out;
 445         }
 446
 447         ret = 0;
 448 out:
 449         kvfree(bitmap);
 450         if (ret)
 451                 btrfs_abort_transaction(trans, ret);
 452         return ret;
 453 }
 454
 455 static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
 456                                           struct btrfs_block_group_cache *block_group,
 457                                           struct btrfs_path *path,
 458                                           int new_extents)
 459 {
 460         struct btrfs_free_space_info *info;
 461         u32 flags;
 462         u32 extent_count;
 463         int ret = 0;
 464
 465         if (new_extents == 0)
 466                 return 0;
 467
 468         info = search_free_space_info(trans, block_group, path, 1);
 469         if (IS_ERR(info)) {
 470                 ret = PTR_ERR(info);
 471                 goto out;
 472         }
 473         flags = btrfs_free_space_flags(path->nodes[0], info);
 474         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
 475
 476         extent_count += new_extents;
 477         btrfs_set_free_space_extent_count(path->nodes[0], info, extent_count);
 478         btrfs_mark_buffer_dirty(path->nodes[0]);
 479         btrfs_release_path(path);
 480
 481         if (!(flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 482             extent_count > block_group->bitmap_high_thresh) {
 483                 ret = convert_free_space_to_bitmaps(trans, block_group, path);
 484         } else if ((flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 485                    extent_count < block_group->bitmap_low_thresh) {
 486                 ret = convert_free_space_to_extents(trans, block_group, path);
 487         }
 488
 489 out:
 490         return ret;
 491 }
 492
 493 EXPORT_FOR_TESTS
 494 int free_space_test_bit(struct btrfs_block_group_cache *block_group,
 495                         struct btrfs_path *path, u64 offset)
 496 {
 497         struct extent_buffer *leaf;
 498         struct btrfs_key key;
 499         u64 found_start, found_end;
 500         unsigned long ptr, i;
 501
 502         leaf = path->nodes[0];
 503         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 504         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 505
 506         found_start = key.objectid;
 507         found_end = key.objectid + key.offset;
 508         ASSERT(offset >= found_start && offset < found_end);
 509
 510         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 511         i = div_u64(offset - found_start,
 512                     block_group->fs_info->sectorsize);
 513         return !!extent_buffer_test_bit(leaf, ptr, i);
 514 }
 515
 516 static void free_space_set_bits(struct btrfs_block_group_cache *block_group,
 517                                 struct btrfs_path *path, u64 *start, u64 *size,
 518                                 int bit)
 519 {
 520         struct btrfs_fs_info *fs_info = block_group->fs_info;
 521         struct extent_buffer *leaf;
 522         struct btrfs_key key;
 523         u64 end = *start + *size;
 524         u64 found_start, found_end;
 525         unsigned long ptr, first, last;
 526
 527         leaf = path->nodes[0];
 528         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 529         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 530
 531         found_start = key.objectid;
 532         found_end = key.objectid + key.offset;
 533         ASSERT(*start >= found_start && *start < found_end);
 534         ASSERT(end > found_start);
 535
 536         if (end > found_end)
 537                 end = found_end;
 538
 539         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 540         first = div_u64(*start - found_start, fs_info->sectorsize);
 541         last = div_u64(end - found_start, fs_info->sectorsize);
 542         if (bit)
 543                 extent_buffer_bitmap_set(leaf, ptr, first, last - first);
 544         else
 545                 extent_buffer_bitmap_clear(leaf, ptr, first, last - first);
 546         btrfs_mark_buffer_dirty(leaf);
 547
 548         *size -= end - *start;
 549         *start = end;
 550 }
 551
 552 /*
 553  * We can't use btrfs_next_item() in modify_free_space_bitmap() because
 554  * btrfs_next_leaf() doesn't get the path for writing. We can forgo the fancy
 555  * tree walking in btrfs_next_leaf() anyways because we know exactly what we're
 556  * looking for.
 557  */
 558 static int free_space_next_bitmap(struct btrfs_trans_handle *trans,
 559                                   struct btrfs_root *root, struct btrfs_path *p)
 560 {
 561         struct btrfs_key key;
 562
 563         if (p->slots[0] + 1 < btrfs_header_nritems(p->nodes[0])) {
 564                 p->slots[0]++;
 565                 return 0;
 566         }
 567
 568         btrfs_item_key_to_cpu(p->nodes[0], &key, p->slots[0]);
 569         btrfs_release_path(p);
 570
 571         key.objectid += key.offset;
 572         key.type = (u8)-1;
 573         key.offset = (u64)-1;
 574
 575         return btrfs_search_prev_slot(trans, root, &key, p, 0, 1);
 576 }
 577
 578 /*
 579  * If remove is 1, then we are removing free space, thus clearing bits in the
 580  * bitmap. If remove is 0, then we are adding free space, thus setting bits in
 581  * the bitmap.
 582  */
 583 static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 584                                     struct btrfs_block_group_cache *block_group,
 585                                     struct btrfs_path *path,
 586                                     u64 start, u64 size, int remove)
 587 {
 588         struct btrfs_root *root = block_group->fs_info->free_space_root;
 589         struct btrfs_key key;
 590         u64 end = start + size;
 591         u64 cur_start, cur_size;
 592         int prev_bit, next_bit;
 593         int new_extents;
 594         int ret;
 595
 596         /*
 597          * Read the bit for the block immediately before the extent of space if
 598          * that block is within the block group.
 599          */
 600         if (start > block_group->key.objectid) {
 601                 u64 prev_block = start - block_group->fs_info->sectorsize;
 602
 603                 key.objectid = prev_block;
 604                 key.type = (u8)-1;
 605                 key.offset = (u64)-1;
 606
 607                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 608                 if (ret)
 609                         goto out;
 610
 611                 prev_bit = free_space_test_bit(block_group, path, prev_block);
 612
 613                 /* The previous block may have been in the previous bitmap. */
 614                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 615                 if (start >= key.objectid + key.offset) {
 616                         ret = free_space_next_bitmap(trans, root, path);
 617                         if (ret)
 618                                 goto out;
 619                 }
 620         } else {
 621                 key.objectid = start;
 622                 key.type = (u8)-1;
 623                 key.offset = (u64)-1;
 624
 625                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 626                 if (ret)
 627                         goto out;
 628
 629                 prev_bit = -1;
 630         }
 631
 632         /*
 633          * Iterate over all of the bitmaps overlapped by the extent of space,
 634          * clearing/setting bits as required.
 635          */
 636         cur_start = start;
 637         cur_size = size;
 638         while (1) {
 639                 free_space_set_bits(block_group, path, &cur_start, &cur_size,
 640                                     !remove);
 641                 if (cur_size == 0)
 642                         break;
 643                 ret = free_space_next_bitmap(trans, root, path);
 644                 if (ret)
 645                         goto out;
 646         }
 647
 648         /*
 649          * Read the bit for the block immediately after the extent of space if
 650          * that block is within the block group.
 651          */
 652         if (end < block_group->key.objectid + block_group->key.offset) {
 653                 /* The next block may be in the next bitmap. */
 654                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 655                 if (end >= key.objectid + key.offset) {
 656                         ret = free_space_next_bitmap(trans, root, path);
 657                         if (ret)
 658                                 goto out;
 659                 }
 660
 661                 next_bit = free_space_test_bit(block_group, path, end);
 662         } else {
 663                 next_bit = -1;
 664         }
 665
 666         if (remove) {
 667                 new_extents = -1;
 668                 if (prev_bit == 1) {
 669                         /* Leftover on the left. */
 670                         new_extents++;
 671                 }
 672                 if (next_bit == 1) {
 673                         /* Leftover on the right. */
 674                         new_extents++;
 675                 }
 676         } else {
 677                 new_extents = 1;
 678                 if (prev_bit == 1) {
 679                         /* Merging with neighbor on the left. */
 680                         new_extents--;
 681                 }
 682                 if (next_bit == 1) {
 683                         /* Merging with neighbor on the right. */
 684                         new_extents--;
 685                 }
 686         }
 687
 688         btrfs_release_path(path);
 689         ret = update_free_space_extent_count(trans, block_group, path,
 690                                              new_extents);
 691
 692 out:
 693         return ret;
 694 }
 695
 696 static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 697                                     struct btrfs_block_group_cache *block_group,
 698                                     struct btrfs_path *path,
 699                                     u64 start, u64 size)
 700 {
 701         struct btrfs_root *root = trans->fs_info->free_space_root;
 702         struct btrfs_key key;
 703         u64 found_start, found_end;
 704         u64 end = start + size;
 705         int new_extents = -1;
 706         int ret;
 707
 708         key.objectid = start;
 709         key.type = (u8)-1;
 710         key.offset = (u64)-1;
 711
 712         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 713         if (ret)
 714                 goto out;
 715
 716         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 717
 718         ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
 719
 720         found_start = key.objectid;
 721         found_end = key.objectid + key.offset;
 722         ASSERT(start >= found_start && end <= found_end);
 723
 724         /*
 725          * Okay, now that we've found the free space extent which contains the
 726          * free space that we are removing, there are four cases:
 727          *
 728          * 1. We're using the whole extent: delete the key we found and
 729          * decrement the free space extent count.
 730          * 2. We are using part of the extent starting at the beginning: delete
 731          * the key we found and insert a new key representing the leftover at
 732          * the end. There is no net change in the number of extents.
 733          * 3. We are using part of the extent ending at the end: delete the key
 734          * we found and insert a new key representing the leftover at the
 735          * beginning. There is no net change in the number of extents.
 736          * 4. We are using part of the extent in the middle: delete the key we
 737          * found and insert two new keys representing the leftovers on each
 738          * side. Where we used to have one extent, we now have two, so increment
 739          * the extent count. We may need to convert the block group to bitmaps
 740          * as a result.
 741          */
 742
 743         /* Delete the existing key (cases 1-4). */
 744         ret = btrfs_del_item(trans, root, path);
 745         if (ret)
 746                 goto out;
 747
 748         /* Add a key for leftovers at the beginning (cases 3 and 4). */
 749         if (start > found_start) {
 750                 key.objectid = found_start;
 751                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 752                 key.offset = start - found_start;
 753
 754                 btrfs_release_path(path);
 755                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 756                 if (ret)
 757                         goto out;
 758                 new_extents++;
 759         }
 760
 761         /* Add a key for leftovers at the end (cases 2 and 4). */
 762         if (end < found_end) {
 763                 key.objectid = end;
 764                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 765                 key.offset = found_end - end;
 766
 767                 btrfs_release_path(path);
 768                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 769                 if (ret)
 770                         goto out;
 771                 new_extents++;
 772         }
 773
 774         btrfs_release_path(path);
 775         ret = update_free_space_extent_count(trans, block_group, path,
 776                                              new_extents);
 777
 778 out:
 779         return ret;
 780 }
 781
 782 EXPORT_FOR_TESTS
 783 int __remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 784                                   struct btrfs_block_group_cache *block_group,
 785                                   struct btrfs_path *path, u64 start, u64 size)
 786 {
 787         struct btrfs_free_space_info *info;
 788         u32 flags;
 789         int ret;
 790
 791         if (block_group->needs_free_space) {
 792                 ret = __add_block_group_free_space(trans, block_group, path);
 793                 if (ret)
 794                         return ret;
 795         }
 796
 797         info = search_free_space_info(NULL, block_group, path, 0);
 798         if (IS_ERR(info))
 799                 return PTR_ERR(info);
 800         flags = btrfs_free_space_flags(path->nodes[0], info);
 801         btrfs_release_path(path);
 802
 803         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
 804                 return modify_free_space_bitmap(trans, block_group, path,
 805                                                 start, size, 1);
 806         } else {
 807                 return remove_free_space_extent(trans, block_group, path,
 808                                                 start, size);
 809         }
 810 }
 811
 812 int remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 813                                 u64 start, u64 size)
 814 {
 815         struct btrfs_block_group_cache *block_group;
 816         struct btrfs_path *path;
 817         int ret;
 818
 819         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
 820                 return 0;
 821
 822         path = btrfs_alloc_path();
 823         if (!path) {
 824                 ret = -ENOMEM;
 825                 goto out;
 826         }
 827
 828         block_group = btrfs_lookup_block_group(trans->fs_info, start);
 829         if (!block_group) {
 830                 ASSERT(0);
 831                 ret = -ENOENT;
 832                 goto out;
 833         }
 834
 835         mutex_lock(&block_group->free_space_lock);
 836         ret = __remove_from_free_space_tree(trans, block_group, path, start,
 837                                             size);
 838         mutex_unlock(&block_group->free_space_lock);
 839
 840         btrfs_put_block_group(block_group);
 841 out:
 842         btrfs_free_path(path);
 843         if (ret)
 844                 btrfs_abort_transaction(trans, ret);
 845         return ret;
 846 }
 847
 848 static int add_free_space_extent(struct btrfs_trans_handle *trans,
 849                                  struct btrfs_block_group_cache *block_group,
 850                                  struct btrfs_path *path,
 851                                  u64 start, u64 size)
 852 {
 853         struct btrfs_root *root = trans->fs_info->free_space_root;
 854         struct btrfs_key key, new_key;
 855         u64 found_start, found_end;
 856         u64 end = start + size;
 857         int new_extents = 1;
 858         int ret;
 859
 860         /*
 861          * We are adding a new extent of free space, but we need to merge
 862          * extents. There are four cases here:
 863          *
 864          * 1. The new extent does not have any immediate neighbors to merge
 865          * with: add the new key and increment the free space extent count. We
 866          * may need to convert the block group to bitmaps as a result.
 867          * 2. The new extent has an immediate neighbor before it: remove the
 868          * previous key and insert a new key combining both of them. There is no
 869          * net change in the number of extents.
 870          * 3. The new extent has an immediate neighbor after it: remove the next
 871          * key and insert a new key combining both of them. There is no net
 872          * change in the number of extents.
 873          * 4. The new extent has immediate neighbors on both sides: remove both
 874          * of the keys and insert a new key combining all of them. Where we used
 875          * to have two extents, we now have one, so decrement the extent count.
 876          */
 877
 878         new_key.objectid = start;
 879         new_key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 880         new_key.offset = size;
 881
 882         /* Search for a neighbor on the left. */
 883         if (start == block_group->key.objectid)
 884                 goto right;
 885         key.objectid = start - 1;
 886         key.type = (u8)-1;
 887         key.offset = (u64)-1;
 888
 889         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 890         if (ret)
 891                 goto out;
 892
 893         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 894
 895         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
 896                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
 897                 btrfs_release_path(path);
 898                 goto right;
 899         }
 900
 901         found_start = key.objectid;
 902         found_end = key.objectid + key.offset;
 903         ASSERT(found_start >= block_group->key.objectid &&
 904                found_end > block_group->key.objectid);
 905         ASSERT(found_start < start && found_end <= start);
 906
 907         /*
 908          * Delete the neighbor on the left and absorb it into the new key (cases
 909          * 2 and 4).
 910          */
 911         if (found_end == start) {
 912                 ret = btrfs_del_item(trans, root, path);
 913                 if (ret)
 914                         goto out;
 915                 new_key.objectid = found_start;
 916                 new_key.offset += key.offset;
 917                 new_extents--;
 918         }
 919         btrfs_release_path(path);
 920
 921 right:
 922         /* Search for a neighbor on the right. */
 923         if (end == block_group->key.objectid + block_group->key.offset)
 924                 goto insert;
 925         key.objectid = end;
 926         key.type = (u8)-1;
 927         key.offset = (u64)-1;
 928
 929         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 930         if (ret)
 931                 goto out;
 932
 933         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 934
 935         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
 936                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
 937                 btrfs_release_path(path);
 938                 goto insert;
 939         }
 940
 941         found_start = key.objectid;
 942         found_end = key.objectid + key.offset;
 943         ASSERT(found_start >= block_group->key.objectid &&
 944                found_end > block_group->key.objectid);
 945         ASSERT((found_start < start && found_end <= start) ||
 946                (found_start >= end && found_end > end));
 947
 948         /*
 949          * Delete the neighbor on the right and absorb it into the new key
 950          * (cases 3 and 4).
 951          */
 952         if (found_start == end) {
 953                 ret = btrfs_del_item(trans, root, path);
 954                 if (ret)
 955                         goto out;
 956                 new_key.offset += key.offset;
 957                 new_extents--;
 958         }
 959         btrfs_release_path(path);
 960
 961 insert:
 962         /* Insert the new key (cases 1-4). */
 963         ret = btrfs_insert_empty_item(trans, root, path, &new_key, 0);
 964         if (ret)
 965                 goto out;
 966
 967         btrfs_release_path(path);
 968         ret = update_free_space_extent_count(trans, block_group, path,
 969                                              new_extents);
 970
 971 out:
 972         return ret;
 973 }
 974
 975 EXPORT_FOR_TESTS
 976 int __add_to_free_space_tree(struct btrfs_trans_handle *trans,
 977                              struct btrfs_block_group_cache *block_group,
 978                              struct btrfs_path *path, u64 start, u64 size)
 979 {
 980         struct btrfs_free_space_info *info;
 981         u32 flags;
 982         int ret;
 983
 984         if (block_group->needs_free_space) {
 985                 ret = __add_block_group_free_space(trans, block_group, path);
 986                 if (ret)
 987                         return ret;
 988         }
 989
 990         info = search_free_space_info(NULL, block_group, path, 0);
 991         if (IS_ERR(info))
 992                 return PTR_ERR(info);
 993         flags = btrfs_free_space_flags(path->nodes[0], info);
 994         btrfs_release_path(path);
 995
 996         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
 997                 return modify_free_space_bitmap(trans, block_group, path,
 998                                                 start, size, 0);
 999         } else {
1000                 return add_free_space_extent(trans, block_group, path, start,
1001                                              size);
1002         }
1003 }
1004
1005 int add_to_free_space_tree(struct btrfs_trans_handle *trans,
1006                            u64 start, u64 size)
1007 {
1008         struct btrfs_block_group_cache *block_group;
1009         struct btrfs_path *path;
1010         int ret;
1011
1012         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1013                 return 0;
1014
1015         path = btrfs_alloc_path();
1016         if (!path) {
1017                 ret = -ENOMEM;
1018                 goto out;
1019         }
1020
1021         block_group = btrfs_lookup_block_group(trans->fs_info, start);
1022         if (!block_group) {
1023                 ASSERT(0);
1024                 ret = -ENOENT;
1025                 goto out;
1026         }
1027
1028         mutex_lock(&block_group->free_space_lock);
1029         ret = __add_to_free_space_tree(trans, block_group, path, start, size);
1030         mutex_unlock(&block_group->free_space_lock);
1031
1032         btrfs_put_block_group(block_group);
1033 out:
1034         btrfs_free_path(path);
1035         if (ret)
1036                 btrfs_abort_transaction(trans, ret);
1037         return ret;
1038 }
1039
1040 /*
1041  * Populate the free space tree by walking the extent tree. Operations on the
1042  * extent tree that happen as a result of writes to the free space tree will go
1043  * through the normal add/remove hooks.
1044  */
1045 static int populate_free_space_tree(struct btrfs_trans_handle *trans,
1046                                     struct btrfs_block_group_cache *block_group)
1047 {
1048         struct btrfs_root *extent_root = trans->fs_info->extent_root;
1049         struct btrfs_path *path, *path2;
1050         struct btrfs_key key;
1051         u64 start, end;
1052         int ret;
1053
1054         path = btrfs_alloc_path();
1055         if (!path)
1056                 return -ENOMEM;
1057         path->reada = READA_FORWARD;
1058
1059         path2 = btrfs_alloc_path();
1060         if (!path2) {
1061                 btrfs_free_path(path);
1062                 return -ENOMEM;
1063         }
1064
1065         ret = add_new_free_space_info(trans, block_group, path2);
1066         if (ret)
1067                 goto out;
1068
1069         mutex_lock(&block_group->free_space_lock);
1070
1071         /*
1072          * Iterate through all of the extent and metadata items in this block
1073          * group, adding the free space between them and the free space at the
1074          * end. Note that EXTENT_ITEM and METADATA_ITEM are less than
1075          * BLOCK_GROUP_ITEM, so an extent may precede the block group that it's
1076          * contained in.
1077          */
1078         key.objectid = block_group->key.objectid;
1079         key.type = BTRFS_EXTENT_ITEM_KEY;
1080         key.offset = 0;
1081
1082         ret = btrfs_search_slot_for_read(extent_root, &key, path, 1, 0);
1083         if (ret < 0)
1084                 goto out_locked;
1085         ASSERT(ret == 0);
1086
1087         start = block_group->key.objectid;
1088         end = block_group->key.objectid + block_group->key.offset;
1089         while (1) {
1090                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1091
1092                 if (key.type == BTRFS_EXTENT_ITEM_KEY ||
1093                     key.type == BTRFS_METADATA_ITEM_KEY) {
1094                         if (key.objectid >= end)
1095                                 break;
1096
1097                         if (start < key.objectid) {
1098                                 ret = __add_to_free_space_tree(trans,
1099                                                                block_group,
1100                                                                path2, start,
1101                                                                key.objectid -
1102                                                                start);
1103                                 if (ret)
1104                                         goto out_locked;
1105                         }
1106                         start = key.objectid;
1107                         if (key.type == BTRFS_METADATA_ITEM_KEY)
1108                                 start += trans->fs_info->nodesize;
1109                         else
1110                                 start += key.offset;
1111                 } else if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
1112                         if (key.objectid != block_group->key.objectid)
1113                                 break;
1114                 }
1115
1116                 ret = btrfs_next_item(extent_root, path);
1117                 if (ret < 0)
1118                         goto out_locked;
1119                 if (ret)
1120                         break;
1121         }
1122         if (start < end) {
1123                 ret = __add_to_free_space_tree(trans, block_group, path2,
1124                                                start, end - start);
1125                 if (ret)
1126                         goto out_locked;
1127         }
1128
1129         ret = 0;
1130 out_locked:
1131         mutex_unlock(&block_group->free_space_lock);
1132 out:
1133         btrfs_free_path(path2);
1134         btrfs_free_path(path);
1135         return ret;
1136 }
1137
1138 int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
1139 {
1140         struct btrfs_trans_handle *trans;
1141         struct btrfs_root *tree_root = fs_info->tree_root;
1142         struct btrfs_root *free_space_root;
1143         struct btrfs_block_group_cache *block_group;
1144         struct rb_node *node;
1145         int ret;
1146
1147         trans = btrfs_start_transaction(tree_root, 0);
1148         if (IS_ERR(trans))
1149                 return PTR_ERR(trans);
1150
1151         set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1152         set_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &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_cache,
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         ret = btrfs_commit_transaction(trans);
1175
1176         /*
1177          * Now that we've committed the transaction any reading of our commit
1178          * root will be safe, so we can cache from the free space tree now.
1179          */
1180         clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
1181         return ret;
1182
1183 abort:
1184         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1185         clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
1186         btrfs_abort_transaction(trans, ret);
1187         btrfs_end_transaction(trans);
1188         return ret;
1189 }
1190
1191 static int clear_free_space_tree(struct btrfs_trans_handle *trans,
1192                                  struct btrfs_root *root)
1193 {
1194         struct btrfs_path *path;
1195         struct btrfs_key key;
1196         int nr;
1197         int ret;
1198
1199         path = btrfs_alloc_path();
1200         if (!path)
1201                 return -ENOMEM;
1202
1203         path->leave_spinning = 1;
1204
1205         key.objectid = 0;
1206         key.type = 0;
1207         key.offset = 0;
1208
1209         while (1) {
1210                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
1211                 if (ret < 0)
1212                         goto out;
1213
1214                 nr = btrfs_header_nritems(path->nodes[0]);
1215                 if (!nr)
1216                         break;
1217
1218                 path->slots[0] = 0;
1219                 ret = btrfs_del_items(trans, root, path, 0, nr);
1220                 if (ret)
1221                         goto out;
1222
1223                 btrfs_release_path(path);
1224         }
1225
1226         ret = 0;
1227 out:
1228         btrfs_free_path(path);
1229         return ret;
1230 }
1231
1232 int btrfs_clear_free_space_tree(struct btrfs_fs_info *fs_info)
1233 {
1234         struct btrfs_trans_handle *trans;
1235         struct btrfs_root *tree_root = fs_info->tree_root;
1236         struct btrfs_root *free_space_root = fs_info->free_space_root;
1237         int ret;
1238
1239         trans = btrfs_start_transaction(tree_root, 0);
1240         if (IS_ERR(trans))
1241                 return PTR_ERR(trans);
1242
1243         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1244         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1245         fs_info->free_space_root = NULL;
1246
1247         ret = clear_free_space_tree(trans, free_space_root);
1248         if (ret)
1249                 goto abort;
1250
1251         ret = btrfs_del_root(trans, &free_space_root->root_key);
1252         if (ret)
1253                 goto abort;
1254
1255         list_del(&free_space_root->dirty_list);
1256
1257         btrfs_tree_lock(free_space_root->node);
1258         btrfs_clean_tree_block(free_space_root->node);
1259         btrfs_tree_unlock(free_space_root->node);
1260         btrfs_free_tree_block(trans, free_space_root, free_space_root->node,
1261                               0, 1);
1262
1263         free_extent_buffer(free_space_root->node);
1264         free_extent_buffer(free_space_root->commit_root);
1265         kfree(free_space_root);
1266
1267         return btrfs_commit_transaction(trans);
1268
1269 abort:
1270         btrfs_abort_transaction(trans, ret);
1271         btrfs_end_transaction(trans);
1272         return ret;
1273 }
1274
1275 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
1276                                         struct btrfs_block_group_cache *block_group,
1277                                         struct btrfs_path *path)
1278 {
1279         int ret;
1280
1281         block_group->needs_free_space = 0;
1282
1283         ret = add_new_free_space_info(trans, block_group, path);
1284         if (ret)
1285                 return ret;
1286
1287         return __add_to_free_space_tree(trans, block_group, path,
1288                                         block_group->key.objectid,
1289                                         block_group->key.offset);
1290 }
1291
1292 int add_block_group_free_space(struct btrfs_trans_handle *trans,
1293                                struct btrfs_block_group_cache *block_group)
1294 {
1295         struct btrfs_fs_info *fs_info = trans->fs_info;
1296         struct btrfs_path *path = NULL;
1297         int ret = 0;
1298
1299         if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
1300                 return 0;
1301
1302         mutex_lock(&block_group->free_space_lock);
1303         if (!block_group->needs_free_space)
1304                 goto out;
1305
1306         path = btrfs_alloc_path();
1307         if (!path) {
1308                 ret = -ENOMEM;
1309                 goto out;
1310         }
1311
1312         ret = __add_block_group_free_space(trans, block_group, path);
1313
1314 out:
1315         btrfs_free_path(path);
1316         mutex_unlock(&block_group->free_space_lock);
1317         if (ret)
1318                 btrfs_abort_transaction(trans, ret);
1319         return ret;
1320 }
1321
1322 int remove_block_group_free_space(struct btrfs_trans_handle *trans,
1323                                   struct btrfs_block_group_cache *block_group)
1324 {
1325         struct btrfs_root *root = trans->fs_info->free_space_root;
1326         struct btrfs_path *path;
1327         struct btrfs_key key, found_key;
1328         struct extent_buffer *leaf;
1329         u64 start, end;
1330         int done = 0, nr;
1331         int ret;
1332
1333         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1334                 return 0;
1335
1336         if (block_group->needs_free_space) {
1337                 /* We never added this block group to the free space tree. */
1338                 return 0;
1339         }
1340
1341         path = btrfs_alloc_path();
1342         if (!path) {
1343                 ret = -ENOMEM;
1344                 goto out;
1345         }
1346
1347         start = block_group->key.objectid;
1348         end = block_group->key.objectid + block_group->key.offset;
1349
1350         key.objectid = end - 1;
1351         key.type = (u8)-1;
1352         key.offset = (u64)-1;
1353
1354         while (!done) {
1355                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
1356                 if (ret)
1357                         goto out;
1358
1359                 leaf = path->nodes[0];
1360                 nr = 0;
1361                 path->slots[0]++;
1362                 while (path->slots[0] > 0) {
1363                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
1364
1365                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
1366                                 ASSERT(found_key.objectid == block_group->key.objectid);
1367                                 ASSERT(found_key.offset == block_group->key.offset);
1368                                 done = 1;
1369                                 nr++;
1370                                 path->slots[0]--;
1371                                 break;
1372                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY ||
1373                                    found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
1374                                 ASSERT(found_key.objectid >= start);
1375                                 ASSERT(found_key.objectid < end);
1376                                 ASSERT(found_key.objectid + found_key.offset <= end);
1377                                 nr++;
1378                                 path->slots[0]--;
1379                         } else {
1380                                 ASSERT(0);
1381                         }
1382                 }
1383
1384                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
1385                 if (ret)
1386                         goto out;
1387                 btrfs_release_path(path);
1388         }
1389
1390         ret = 0;
1391 out:
1392         btrfs_free_path(path);
1393         if (ret)
1394                 btrfs_abort_transaction(trans, ret);
1395         return ret;
1396 }
1397
1398 static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
1399                                    struct btrfs_path *path,
1400                                    u32 expected_extent_count)
1401 {
1402         struct btrfs_block_group_cache *block_group;
1403         struct btrfs_fs_info *fs_info;
1404         struct btrfs_root *root;
1405         struct btrfs_key key;
1406         int prev_bit = 0, bit;
1407         /* Initialize to silence GCC. */
1408         u64 extent_start = 0;
1409         u64 end, offset;
1410         u64 total_found = 0;
1411         u32 extent_count = 0;
1412         int ret;
1413
1414         block_group = caching_ctl->block_group;
1415         fs_info = block_group->fs_info;
1416         root = fs_info->free_space_root;
1417
1418         end = block_group->key.objectid + block_group->key.offset;
1419
1420         while (1) {
1421                 ret = btrfs_next_item(root, path);
1422                 if (ret < 0)
1423                         goto out;
1424                 if (ret)
1425                         break;
1426
1427                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1428
1429                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1430                         break;
1431
1432                 ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
1433                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1434
1435                 caching_ctl->progress = key.objectid;
1436
1437                 offset = key.objectid;
1438                 while (offset < key.objectid + key.offset) {
1439                         bit = free_space_test_bit(block_group, path, offset);
1440                         if (prev_bit == 0 && bit == 1) {
1441                                 extent_start = offset;
1442                         } else if (prev_bit == 1 && bit == 0) {
1443                                 total_found += add_new_free_space(block_group,
1444                                                                   extent_start,
1445                                                                   offset);
1446                                 if (total_found > CACHING_CTL_WAKE_UP) {
1447                                         total_found = 0;
1448                                         wake_up(&caching_ctl->wait);
1449                                 }
1450                                 extent_count++;
1451                         }
1452                         prev_bit = bit;
1453                         offset += fs_info->sectorsize;
1454                 }
1455         }
1456         if (prev_bit == 1) {
1457                 total_found += add_new_free_space(block_group, extent_start,
1458                                                   end);
1459                 extent_count++;
1460         }
1461
1462         if (extent_count != expected_extent_count) {
1463                 btrfs_err(fs_info,
1464                           "incorrect extent count for %llu; counted %u, expected %u",
1465                           block_group->key.objectid, extent_count,
1466                           expected_extent_count);
1467                 ASSERT(0);
1468                 ret = -EIO;
1469                 goto out;
1470         }
1471
1472         caching_ctl->progress = (u64)-1;
1473
1474         ret = 0;
1475 out:
1476         return ret;
1477 }
1478
1479 static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
1480                                    struct btrfs_path *path,
1481                                    u32 expected_extent_count)
1482 {
1483         struct btrfs_block_group_cache *block_group;
1484         struct btrfs_fs_info *fs_info;
1485         struct btrfs_root *root;
1486         struct btrfs_key key;
1487         u64 end;
1488         u64 total_found = 0;
1489         u32 extent_count = 0;
1490         int ret;
1491
1492         block_group = caching_ctl->block_group;
1493         fs_info = block_group->fs_info;
1494         root = fs_info->free_space_root;
1495
1496         end = block_group->key.objectid + block_group->key.offset;
1497
1498         while (1) {
1499                 ret = btrfs_next_item(root, path);
1500                 if (ret < 0)
1501                         goto out;
1502                 if (ret)
1503                         break;
1504
1505                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1506
1507                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1508                         break;
1509
1510                 ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
1511                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1512
1513                 caching_ctl->progress = key.objectid;
1514
1515                 total_found += add_new_free_space(block_group, key.objectid,
1516                                                   key.objectid + key.offset);
1517                 if (total_found > CACHING_CTL_WAKE_UP) {
1518                         total_found = 0;
1519                         wake_up(&caching_ctl->wait);
1520                 }
1521                 extent_count++;
1522         }
1523
1524         if (extent_count != expected_extent_count) {
1525                 btrfs_err(fs_info,
1526                           "incorrect extent count for %llu; counted %u, expected %u",
1527                           block_group->key.objectid, extent_count,
1528                           expected_extent_count);
1529                 ASSERT(0);
1530                 ret = -EIO;
1531                 goto out;
1532         }
1533
1534         caching_ctl->progress = (u64)-1;
1535
1536         ret = 0;
1537 out:
1538         return ret;
1539 }
1540
1541 int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
1542 {
1543         struct btrfs_block_group_cache *block_group;
1544         struct btrfs_free_space_info *info;
1545         struct btrfs_path *path;
1546         u32 extent_count, flags;
1547         int ret;
1548
1549         block_group = caching_ctl->block_group;
1550
1551         path = btrfs_alloc_path();
1552         if (!path)
1553                 return -ENOMEM;
1554
1555         /*
1556          * Just like caching_thread() doesn't want to deadlock on the extent
1557          * tree, we don't want to deadlock on the free space tree.
1558          */
1559         path->skip_locking = 1;
1560         path->search_commit_root = 1;
1561         path->reada = READA_FORWARD;
1562
1563         info = search_free_space_info(NULL, block_group, path, 0);
1564         if (IS_ERR(info)) {
1565                 ret = PTR_ERR(info);
1566                 goto out;
1567         }
1568         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
1569         flags = btrfs_free_space_flags(path->nodes[0], info);
1570
1571         /*
1572          * We left path pointing to the free space info item, so now
1573          * load_free_space_foo can just iterate through the free space tree from
1574          * there.
1575          */
1576         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS)
1577                 ret = load_free_space_bitmaps(caching_ctl, path, extent_count);
1578         else
1579                 ret = load_free_space_extents(caching_ctl, path, extent_count);
1580
1581 out:
1582         btrfs_free_path(path);
1583         return ret;
1584 }