fs/btrfs/free-space-tree.c

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