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 "messages.h"
   9 #include "ctree.h"
  10 #include "disk-io.h"
  11 #include "locking.h"
  12 #include "free-space-tree.h"
  13 #include "transaction.h"
  14 #include "block-group.h"
  15 #include "fs.h"
  16 #include "accessors.h"
  17 #include "extent-tree.h"
  18 #include "root-tree.h"
  19
  20 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
  21                                         struct btrfs_block_group *block_group,
  22                                         struct btrfs_path *path);
  23
  24 static struct btrfs_root *btrfs_free_space_root(
  25                                 struct btrfs_block_group *block_group)
  26 {
  27         struct btrfs_key key = {
  28                 .objectid = BTRFS_FREE_SPACE_TREE_OBJECTID,
  29                 .type = BTRFS_ROOT_ITEM_KEY,
  30                 .offset = 0,
  31         };
  32
  33         if (btrfs_fs_incompat(block_group->fs_info, EXTENT_TREE_V2))
  34                 key.offset = block_group->global_root_id;
  35         return btrfs_global_root(block_group->fs_info, &key);
  36 }
  37
  38 void set_free_space_tree_thresholds(struct btrfs_block_group *cache)
  39 {
  40         u32 bitmap_range;
  41         size_t bitmap_size;
  42         u64 num_bitmaps, total_bitmap_size;
  43
  44         if (WARN_ON(cache->length == 0))
  45                 btrfs_warn(cache->fs_info, "block group %llu length is zero",
  46                            cache->start);
  47
  48         /*
  49          * We convert to bitmaps when the disk space required for using extents
  50          * exceeds that required for using bitmaps.
  51          */
  52         bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
  53         num_bitmaps = div_u64(cache->length + bitmap_range - 1, bitmap_range);
  54         bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
  55         total_bitmap_size = num_bitmaps * bitmap_size;
  56         cache->bitmap_high_thresh = div_u64(total_bitmap_size,
  57                                             sizeof(struct btrfs_item));
  58
  59         /*
  60          * We allow for a small buffer between the high threshold and low
  61          * threshold to avoid thrashing back and forth between the two formats.
  62          */
  63         if (cache->bitmap_high_thresh > 100)
  64                 cache->bitmap_low_thresh = cache->bitmap_high_thresh - 100;
  65         else
  66                 cache->bitmap_low_thresh = 0;
  67 }
  68
  69 static int add_new_free_space_info(struct btrfs_trans_handle *trans,
  70                                    struct btrfs_block_group *block_group,
  71                                    struct btrfs_path *path)
  72 {
  73         struct btrfs_root *root = btrfs_free_space_root(block_group);
  74         struct btrfs_free_space_info *info;
  75         struct btrfs_key key;
  76         struct extent_buffer *leaf;
  77         int ret;
  78
  79         key.objectid = block_group->start;
  80         key.type = BTRFS_FREE_SPACE_INFO_KEY;
  81         key.offset = block_group->length;
  82
  83         ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
  84         if (ret)
  85                 goto out;
  86
  87         leaf = path->nodes[0];
  88         info = btrfs_item_ptr(leaf, path->slots[0],
  89                               struct btrfs_free_space_info);
  90         btrfs_set_free_space_extent_count(leaf, info, 0);
  91         btrfs_set_free_space_flags(leaf, info, 0);
  92         btrfs_mark_buffer_dirty(leaf);
  93
  94         ret = 0;
  95 out:
  96         btrfs_release_path(path);
  97         return ret;
  98 }
  99
 100 EXPORT_FOR_TESTS
 101 struct btrfs_free_space_info *search_free_space_info(
 102                 struct btrfs_trans_handle *trans,
 103                 struct btrfs_block_group *block_group,
 104                 struct btrfs_path *path, int cow)
 105 {
 106         struct btrfs_fs_info *fs_info = block_group->fs_info;
 107         struct btrfs_root *root = btrfs_free_space_root(block_group);
 108         struct btrfs_key key;
 109         int ret;
 110
 111         key.objectid = block_group->start;
 112         key.type = BTRFS_FREE_SPACE_INFO_KEY;
 113         key.offset = block_group->length;
 114
 115         ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
 116         if (ret < 0)
 117                 return ERR_PTR(ret);
 118         if (ret != 0) {
 119                 btrfs_warn(fs_info, "missing free space info for %llu",
 120                            block_group->start);
 121                 ASSERT(0);
 122                 return ERR_PTR(-ENOENT);
 123         }
 124
 125         return btrfs_item_ptr(path->nodes[0], path->slots[0],
 126                               struct btrfs_free_space_info);
 127 }
 128
 129 /*
 130  * btrfs_search_slot() but we're looking for the greatest key less than the
 131  * passed key.
 132  */
 133 static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
 134                                   struct btrfs_root *root,
 135                                   struct btrfs_key *key, struct btrfs_path *p,
 136                                   int ins_len, int cow)
 137 {
 138         int ret;
 139
 140         ret = btrfs_search_slot(trans, root, key, p, ins_len, cow);
 141         if (ret < 0)
 142                 return ret;
 143
 144         if (ret == 0) {
 145                 ASSERT(0);
 146                 return -EIO;
 147         }
 148
 149         if (p->slots[0] == 0) {
 150                 ASSERT(0);
 151                 return -EIO;
 152         }
 153         p->slots[0]--;
 154
 155         return 0;
 156 }
 157
 158 static inline u32 free_space_bitmap_size(const struct btrfs_fs_info *fs_info,
 159                                          u64 size)
 160 {
 161         return DIV_ROUND_UP(size >> fs_info->sectorsize_bits, BITS_PER_BYTE);
 162 }
 163
 164 static unsigned long *alloc_bitmap(u32 bitmap_size)
 165 {
 166         unsigned long *ret;
 167         unsigned int nofs_flag;
 168         u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));
 169
 170         /*
 171          * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
 172          * into the filesystem as the free space bitmap can be modified in the
 173          * critical section of a transaction commit.
 174          *
 175          * TODO: push the memalloc_nofs_{save,restore}() to the caller where we
 176          * know that recursion is unsafe.
 177          */
 178         nofs_flag = memalloc_nofs_save();
 179         ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
 180         memalloc_nofs_restore(nofs_flag);
 181         return ret;
 182 }
 183
 184 static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
 185 {
 186         u8 *p = ((u8 *)map) + BIT_BYTE(start);
 187         const unsigned int size = start + len;
 188         int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
 189         u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
 190
 191         while (len - bits_to_set >= 0) {
 192                 *p |= mask_to_set;
 193                 len -= bits_to_set;
 194                 bits_to_set = BITS_PER_BYTE;
 195                 mask_to_set = ~0;
 196                 p++;
 197         }
 198         if (len) {
 199                 mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
 200                 *p |= mask_to_set;
 201         }
 202 }
 203
 204 EXPORT_FOR_TESTS
 205 int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 206                                   struct btrfs_block_group *block_group,
 207                                   struct btrfs_path *path)
 208 {
 209         struct btrfs_fs_info *fs_info = trans->fs_info;
 210         struct btrfs_root *root = btrfs_free_space_root(block_group);
 211         struct btrfs_free_space_info *info;
 212         struct btrfs_key key, found_key;
 213         struct extent_buffer *leaf;
 214         unsigned long *bitmap;
 215         char *bitmap_cursor;
 216         u64 start, end;
 217         u64 bitmap_range, i;
 218         u32 bitmap_size, flags, expected_extent_count;
 219         u32 extent_count = 0;
 220         int done = 0, nr;
 221         int ret;
 222
 223         bitmap_size = free_space_bitmap_size(fs_info, block_group->length);
 224         bitmap = alloc_bitmap(bitmap_size);
 225         if (!bitmap) {
 226                 ret = -ENOMEM;
 227                 goto out;
 228         }
 229
 230         start = block_group->start;
 231         end = block_group->start + block_group->length;
 232
 233         key.objectid = end - 1;
 234         key.type = (u8)-1;
 235         key.offset = (u64)-1;
 236
 237         while (!done) {
 238                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 239                 if (ret)
 240                         goto out;
 241
 242                 leaf = path->nodes[0];
 243                 nr = 0;
 244                 path->slots[0]++;
 245                 while (path->slots[0] > 0) {
 246                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 247
 248                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
 249                                 ASSERT(found_key.objectid == block_group->start);
 250                                 ASSERT(found_key.offset == block_group->length);
 251                                 done = 1;
 252                                 break;
 253                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY) {
 254                                 u64 first, last;
 255
 256                                 ASSERT(found_key.objectid >= start);
 257                                 ASSERT(found_key.objectid < end);
 258                                 ASSERT(found_key.objectid + found_key.offset <= end);
 259
 260                                 first = div_u64(found_key.objectid - start,
 261                                                 fs_info->sectorsize);
 262                                 last = div_u64(found_key.objectid + found_key.offset - start,
 263                                                fs_info->sectorsize);
 264                                 le_bitmap_set(bitmap, first, last - first);
 265
 266                                 extent_count++;
 267                                 nr++;
 268                                 path->slots[0]--;
 269                         } else {
 270                                 ASSERT(0);
 271                         }
 272                 }
 273
 274                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
 275                 if (ret)
 276                         goto out;
 277                 btrfs_release_path(path);
 278         }
 279
 280         info = search_free_space_info(trans, block_group, path, 1);
 281         if (IS_ERR(info)) {
 282                 ret = PTR_ERR(info);
 283                 goto out;
 284         }
 285         leaf = path->nodes[0];
 286         flags = btrfs_free_space_flags(leaf, info);
 287         flags |= BTRFS_FREE_SPACE_USING_BITMAPS;
 288         btrfs_set_free_space_flags(leaf, info, flags);
 289         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
 290         btrfs_mark_buffer_dirty(leaf);
 291         btrfs_release_path(path);
 292
 293         if (extent_count != expected_extent_count) {
 294                 btrfs_err(fs_info,
 295                           "incorrect extent count for %llu; counted %u, expected %u",
 296                           block_group->start, extent_count,
 297                           expected_extent_count);
 298                 ASSERT(0);
 299                 ret = -EIO;
 300                 goto out;
 301         }
 302
 303         bitmap_cursor = (char *)bitmap;
 304         bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
 305         i = start;
 306         while (i < end) {
 307                 unsigned long ptr;
 308                 u64 extent_size;
 309                 u32 data_size;
 310
 311                 extent_size = min(end - i, bitmap_range);
 312                 data_size = free_space_bitmap_size(fs_info, extent_size);
 313
 314                 key.objectid = i;
 315                 key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
 316                 key.offset = extent_size;
 317
 318                 ret = btrfs_insert_empty_item(trans, root, path, &key,
 319                                               data_size);
 320                 if (ret)
 321                         goto out;
 322
 323                 leaf = path->nodes[0];
 324                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 325                 write_extent_buffer(leaf, bitmap_cursor, ptr,
 326                                     data_size);
 327                 btrfs_mark_buffer_dirty(leaf);
 328                 btrfs_release_path(path);
 329
 330                 i += extent_size;
 331                 bitmap_cursor += data_size;
 332         }
 333
 334         ret = 0;
 335 out:
 336         kvfree(bitmap);
 337         if (ret)
 338                 btrfs_abort_transaction(trans, ret);
 339         return ret;
 340 }
 341
 342 EXPORT_FOR_TESTS
 343 int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
 344                                   struct btrfs_block_group *block_group,
 345                                   struct btrfs_path *path)
 346 {
 347         struct btrfs_fs_info *fs_info = trans->fs_info;
 348         struct btrfs_root *root = btrfs_free_space_root(block_group);
 349         struct btrfs_free_space_info *info;
 350         struct btrfs_key key, found_key;
 351         struct extent_buffer *leaf;
 352         unsigned long *bitmap;
 353         u64 start, end;
 354         u32 bitmap_size, flags, expected_extent_count;
 355         unsigned long nrbits, start_bit, end_bit;
 356         u32 extent_count = 0;
 357         int done = 0, nr;
 358         int ret;
 359
 360         bitmap_size = free_space_bitmap_size(fs_info, block_group->length);
 361         bitmap = alloc_bitmap(bitmap_size);
 362         if (!bitmap) {
 363                 ret = -ENOMEM;
 364                 goto out;
 365         }
 366
 367         start = block_group->start;
 368         end = block_group->start + block_group->length;
 369
 370         key.objectid = end - 1;
 371         key.type = (u8)-1;
 372         key.offset = (u64)-1;
 373
 374         while (!done) {
 375                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 376                 if (ret)
 377                         goto out;
 378
 379                 leaf = path->nodes[0];
 380                 nr = 0;
 381                 path->slots[0]++;
 382                 while (path->slots[0] > 0) {
 383                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 384
 385                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
 386                                 ASSERT(found_key.objectid == block_group->start);
 387                                 ASSERT(found_key.offset == block_group->length);
 388                                 done = 1;
 389                                 break;
 390                         } else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
 391                                 unsigned long ptr;
 392                                 char *bitmap_cursor;
 393                                 u32 bitmap_pos, data_size;
 394
 395                                 ASSERT(found_key.objectid >= start);
 396                                 ASSERT(found_key.objectid < end);
 397                                 ASSERT(found_key.objectid + found_key.offset <= end);
 398
 399                                 bitmap_pos = div_u64(found_key.objectid - start,
 400                                                      fs_info->sectorsize *
 401                                                      BITS_PER_BYTE);
 402                                 bitmap_cursor = ((char *)bitmap) + bitmap_pos;
 403                                 data_size = free_space_bitmap_size(fs_info,
 404                                                                 found_key.offset);
 405
 406                                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
 407                                 read_extent_buffer(leaf, bitmap_cursor, ptr,
 408                                                    data_size);
 409
 410                                 nr++;
 411                                 path->slots[0]--;
 412                         } else {
 413                                 ASSERT(0);
 414                         }
 415                 }
 416
 417                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
 418                 if (ret)
 419                         goto out;
 420                 btrfs_release_path(path);
 421         }
 422
 423         info = search_free_space_info(trans, block_group, path, 1);
 424         if (IS_ERR(info)) {
 425                 ret = PTR_ERR(info);
 426                 goto out;
 427         }
 428         leaf = path->nodes[0];
 429         flags = btrfs_free_space_flags(leaf, info);
 430         flags &= ~BTRFS_FREE_SPACE_USING_BITMAPS;
 431         btrfs_set_free_space_flags(leaf, info, flags);
 432         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
 433         btrfs_mark_buffer_dirty(leaf);
 434         btrfs_release_path(path);
 435
 436         nrbits = block_group->length >> block_group->fs_info->sectorsize_bits;
 437         start_bit = find_next_bit_le(bitmap, nrbits, 0);
 438
 439         while (start_bit < nrbits) {
 440                 end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
 441                 ASSERT(start_bit < end_bit);
 442
 443                 key.objectid = start + start_bit * block_group->fs_info->sectorsize;
 444                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 445                 key.offset = (end_bit - start_bit) * block_group->fs_info->sectorsize;
 446
 447                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 448                 if (ret)
 449                         goto out;
 450                 btrfs_release_path(path);
 451
 452                 extent_count++;
 453
 454                 start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
 455         }
 456
 457         if (extent_count != expected_extent_count) {
 458                 btrfs_err(fs_info,
 459                           "incorrect extent count for %llu; counted %u, expected %u",
 460                           block_group->start, extent_count,
 461                           expected_extent_count);
 462                 ASSERT(0);
 463                 ret = -EIO;
 464                 goto out;
 465         }
 466
 467         ret = 0;
 468 out:
 469         kvfree(bitmap);
 470         if (ret)
 471                 btrfs_abort_transaction(trans, ret);
 472         return ret;
 473 }
 474
 475 static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
 476                                           struct btrfs_block_group *block_group,
 477                                           struct btrfs_path *path,
 478                                           int new_extents)
 479 {
 480         struct btrfs_free_space_info *info;
 481         u32 flags;
 482         u32 extent_count;
 483         int ret = 0;
 484
 485         if (new_extents == 0)
 486                 return 0;
 487
 488         info = search_free_space_info(trans, block_group, path, 1);
 489         if (IS_ERR(info)) {
 490                 ret = PTR_ERR(info);
 491                 goto out;
 492         }
 493         flags = btrfs_free_space_flags(path->nodes[0], info);
 494         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
 495
 496         extent_count += new_extents;
 497         btrfs_set_free_space_extent_count(path->nodes[0], info, extent_count);
 498         btrfs_mark_buffer_dirty(path->nodes[0]);
 499         btrfs_release_path(path);
 500
 501         if (!(flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 502             extent_count > block_group->bitmap_high_thresh) {
 503                 ret = convert_free_space_to_bitmaps(trans, block_group, path);
 504         } else if ((flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 505                    extent_count < block_group->bitmap_low_thresh) {
 506                 ret = convert_free_space_to_extents(trans, block_group, path);
 507         }
 508
 509 out:
 510         return ret;
 511 }
 512
 513 EXPORT_FOR_TESTS
 514 int free_space_test_bit(struct btrfs_block_group *block_group,
 515                         struct btrfs_path *path, u64 offset)
 516 {
 517         struct extent_buffer *leaf;
 518         struct btrfs_key key;
 519         u64 found_start, found_end;
 520         unsigned long ptr, i;
 521
 522         leaf = path->nodes[0];
 523         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 524         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 525
 526         found_start = key.objectid;
 527         found_end = key.objectid + key.offset;
 528         ASSERT(offset >= found_start && offset < found_end);
 529
 530         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 531         i = div_u64(offset - found_start,
 532                     block_group->fs_info->sectorsize);
 533         return !!extent_buffer_test_bit(leaf, ptr, i);
 534 }
 535
 536 static void free_space_set_bits(struct btrfs_block_group *block_group,
 537                                 struct btrfs_path *path, u64 *start, u64 *size,
 538                                 int bit)
 539 {
 540         struct btrfs_fs_info *fs_info = block_group->fs_info;
 541         struct extent_buffer *leaf;
 542         struct btrfs_key key;
 543         u64 end = *start + *size;
 544         u64 found_start, found_end;
 545         unsigned long ptr, first, last;
 546
 547         leaf = path->nodes[0];
 548         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 549         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 550
 551         found_start = key.objectid;
 552         found_end = key.objectid + key.offset;
 553         ASSERT(*start >= found_start && *start < found_end);
 554         ASSERT(end > found_start);
 555
 556         if (end > found_end)
 557                 end = found_end;
 558
 559         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 560         first = (*start - found_start) >> fs_info->sectorsize_bits;
 561         last = (end - found_start) >> fs_info->sectorsize_bits;
 562         if (bit)
 563                 extent_buffer_bitmap_set(leaf, ptr, first, last - first);
 564         else
 565                 extent_buffer_bitmap_clear(leaf, ptr, first, last - first);
 566         btrfs_mark_buffer_dirty(leaf);
 567
 568         *size -= end - *start;
 569         *start = end;
 570 }
 571
 572 /*
 573  * We can't use btrfs_next_item() in modify_free_space_bitmap() because
 574  * btrfs_next_leaf() doesn't get the path for writing. We can forgo the fancy
 575  * tree walking in btrfs_next_leaf() anyways because we know exactly what we're
 576  * looking for.
 577  */
 578 static int free_space_next_bitmap(struct btrfs_trans_handle *trans,
 579                                   struct btrfs_root *root, struct btrfs_path *p)
 580 {
 581         struct btrfs_key key;
 582
 583         if (p->slots[0] + 1 < btrfs_header_nritems(p->nodes[0])) {
 584                 p->slots[0]++;
 585                 return 0;
 586         }
 587
 588         btrfs_item_key_to_cpu(p->nodes[0], &key, p->slots[0]);
 589         btrfs_release_path(p);
 590
 591         key.objectid += key.offset;
 592         key.type = (u8)-1;
 593         key.offset = (u64)-1;
 594
 595         return btrfs_search_prev_slot(trans, root, &key, p, 0, 1);
 596 }
 597
 598 /*
 599  * If remove is 1, then we are removing free space, thus clearing bits in the
 600  * bitmap. If remove is 0, then we are adding free space, thus setting bits in
 601  * the bitmap.
 602  */
 603 static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 604                                     struct btrfs_block_group *block_group,
 605                                     struct btrfs_path *path,
 606                                     u64 start, u64 size, int remove)
 607 {
 608         struct btrfs_root *root = btrfs_free_space_root(block_group);
 609         struct btrfs_key key;
 610         u64 end = start + size;
 611         u64 cur_start, cur_size;
 612         int prev_bit, next_bit;
 613         int new_extents;
 614         int ret;
 615
 616         /*
 617          * Read the bit for the block immediately before the extent of space if
 618          * that block is within the block group.
 619          */
 620         if (start > block_group->start) {
 621                 u64 prev_block = start - block_group->fs_info->sectorsize;
 622
 623                 key.objectid = prev_block;
 624                 key.type = (u8)-1;
 625                 key.offset = (u64)-1;
 626
 627                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 628                 if (ret)
 629                         goto out;
 630
 631                 prev_bit = free_space_test_bit(block_group, path, prev_block);
 632
 633                 /* The previous block may have been in the previous bitmap. */
 634                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 635                 if (start >= key.objectid + key.offset) {
 636                         ret = free_space_next_bitmap(trans, root, path);
 637                         if (ret)
 638                                 goto out;
 639                 }
 640         } else {
 641                 key.objectid = start;
 642                 key.type = (u8)-1;
 643                 key.offset = (u64)-1;
 644
 645                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 646                 if (ret)
 647                         goto out;
 648
 649                 prev_bit = -1;
 650         }
 651
 652         /*
 653          * Iterate over all of the bitmaps overlapped by the extent of space,
 654          * clearing/setting bits as required.
 655          */
 656         cur_start = start;
 657         cur_size = size;
 658         while (1) {
 659                 free_space_set_bits(block_group, path, &cur_start, &cur_size,
 660                                     !remove);
 661                 if (cur_size == 0)
 662                         break;
 663                 ret = free_space_next_bitmap(trans, root, path);
 664                 if (ret)
 665                         goto out;
 666         }
 667
 668         /*
 669          * Read the bit for the block immediately after the extent of space if
 670          * that block is within the block group.
 671          */
 672         if (end < block_group->start + block_group->length) {
 673                 /* The next block may be in the next bitmap. */
 674                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 675                 if (end >= key.objectid + key.offset) {
 676                         ret = free_space_next_bitmap(trans, root, path);
 677                         if (ret)
 678                                 goto out;
 679                 }
 680
 681                 next_bit = free_space_test_bit(block_group, path, end);
 682         } else {
 683                 next_bit = -1;
 684         }
 685
 686         if (remove) {
 687                 new_extents = -1;
 688                 if (prev_bit == 1) {
 689                         /* Leftover on the left. */
 690                         new_extents++;
 691                 }
 692                 if (next_bit == 1) {
 693                         /* Leftover on the right. */
 694                         new_extents++;
 695                 }
 696         } else {
 697                 new_extents = 1;
 698                 if (prev_bit == 1) {
 699                         /* Merging with neighbor on the left. */
 700                         new_extents--;
 701                 }
 702                 if (next_bit == 1) {
 703                         /* Merging with neighbor on the right. */
 704                         new_extents--;
 705                 }
 706         }
 707
 708         btrfs_release_path(path);
 709         ret = update_free_space_extent_count(trans, block_group, path,
 710                                              new_extents);
 711
 712 out:
 713         return ret;
 714 }
 715
 716 static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 717                                     struct btrfs_block_group *block_group,
 718                                     struct btrfs_path *path,
 719                                     u64 start, u64 size)
 720 {
 721         struct btrfs_root *root = btrfs_free_space_root(block_group);
 722         struct btrfs_key key;
 723         u64 found_start, found_end;
 724         u64 end = start + size;
 725         int new_extents = -1;
 726         int ret;
 727
 728         key.objectid = start;
 729         key.type = (u8)-1;
 730         key.offset = (u64)-1;
 731
 732         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 733         if (ret)
 734                 goto out;
 735
 736         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 737
 738         ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
 739
 740         found_start = key.objectid;
 741         found_end = key.objectid + key.offset;
 742         ASSERT(start >= found_start && end <= found_end);
 743
 744         /*
 745          * Okay, now that we've found the free space extent which contains the
 746          * free space that we are removing, there are four cases:
 747          *
 748          * 1. We're using the whole extent: delete the key we found and
 749          * decrement the free space extent count.
 750          * 2. We are using part of the extent starting at the beginning: delete
 751          * the key we found and insert a new key representing the leftover at
 752          * the end. There is no net change in the number of extents.
 753          * 3. We are using part of the extent ending at the end: delete the key
 754          * we found and insert a new key representing the leftover at the
 755          * beginning. There is no net change in the number of extents.
 756          * 4. We are using part of the extent in the middle: delete the key we
 757          * found and insert two new keys representing the leftovers on each
 758          * side. Where we used to have one extent, we now have two, so increment
 759          * the extent count. We may need to convert the block group to bitmaps
 760          * as a result.
 761          */
 762
 763         /* Delete the existing key (cases 1-4). */
 764         ret = btrfs_del_item(trans, root, path);
 765         if (ret)
 766                 goto out;
 767
 768         /* Add a key for leftovers at the beginning (cases 3 and 4). */
 769         if (start > found_start) {
 770                 key.objectid = found_start;
 771                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 772                 key.offset = start - found_start;
 773
 774                 btrfs_release_path(path);
 775                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 776                 if (ret)
 777                         goto out;
 778                 new_extents++;
 779         }
 780
 781         /* Add a key for leftovers at the end (cases 2 and 4). */
 782         if (end < found_end) {
 783                 key.objectid = end;
 784                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 785                 key.offset = found_end - end;
 786
 787                 btrfs_release_path(path);
 788                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 789                 if (ret)
 790                         goto out;
 791                 new_extents++;
 792         }
 793
 794         btrfs_release_path(path);
 795         ret = update_free_space_extent_count(trans, block_group, path,
 796                                              new_extents);
 797
 798 out:
 799         return ret;
 800 }
 801
 802 EXPORT_FOR_TESTS
 803 int __remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 804                                   struct btrfs_block_group *block_group,
 805                                   struct btrfs_path *path, u64 start, u64 size)
 806 {
 807         struct btrfs_free_space_info *info;
 808         u32 flags;
 809         int ret;
 810
 811         if (test_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, &block_group->runtime_flags)) {
 812                 ret = __add_block_group_free_space(trans, block_group, path);
 813                 if (ret)
 814                         return ret;
 815         }
 816
 817         info = search_free_space_info(NULL, block_group, path, 0);
 818         if (IS_ERR(info))
 819                 return PTR_ERR(info);
 820         flags = btrfs_free_space_flags(path->nodes[0], info);
 821         btrfs_release_path(path);
 822
 823         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
 824                 return modify_free_space_bitmap(trans, block_group, path,
 825                                                 start, size, 1);
 826         } else {
 827                 return remove_free_space_extent(trans, block_group, path,
 828                                                 start, size);
 829         }
 830 }
 831
 832 int remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 833                                 u64 start, u64 size)
 834 {
 835         struct btrfs_block_group *block_group;
 836         struct btrfs_path *path;
 837         int ret;
 838
 839         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
 840                 return 0;
 841
 842         path = btrfs_alloc_path();
 843         if (!path) {
 844                 ret = -ENOMEM;
 845                 goto out;
 846         }
 847
 848         block_group = btrfs_lookup_block_group(trans->fs_info, start);
 849         if (!block_group) {
 850                 ASSERT(0);
 851                 ret = -ENOENT;
 852                 goto out;
 853         }
 854
 855         mutex_lock(&block_group->free_space_lock);
 856         ret = __remove_from_free_space_tree(trans, block_group, path, start,
 857                                             size);
 858         mutex_unlock(&block_group->free_space_lock);
 859
 860         btrfs_put_block_group(block_group);
 861 out:
 862         btrfs_free_path(path);
 863         if (ret)
 864                 btrfs_abort_transaction(trans, ret);
 865         return ret;
 866 }
 867
 868 static int add_free_space_extent(struct btrfs_trans_handle *trans,
 869                                  struct btrfs_block_group *block_group,
 870                                  struct btrfs_path *path,
 871                                  u64 start, u64 size)
 872 {
 873         struct btrfs_root *root = btrfs_free_space_root(block_group);
 874         struct btrfs_key key, new_key;
 875         u64 found_start, found_end;
 876         u64 end = start + size;
 877         int new_extents = 1;
 878         int ret;
 879
 880         /*
 881          * We are adding a new extent of free space, but we need to merge
 882          * extents. There are four cases here:
 883          *
 884          * 1. The new extent does not have any immediate neighbors to merge
 885          * with: add the new key and increment the free space extent count. We
 886          * may need to convert the block group to bitmaps as a result.
 887          * 2. The new extent has an immediate neighbor before it: remove the
 888          * previous key and insert a new key combining both of them. There is no
 889          * net change in the number of extents.
 890          * 3. The new extent has an immediate neighbor after it: remove the next
 891          * key and insert a new key combining both of them. There is no net
 892          * change in the number of extents.
 893          * 4. The new extent has immediate neighbors on both sides: remove both
 894          * of the keys and insert a new key combining all of them. Where we used
 895          * to have two extents, we now have one, so decrement the extent count.
 896          */
 897
 898         new_key.objectid = start;
 899         new_key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
 900         new_key.offset = size;
 901
 902         /* Search for a neighbor on the left. */
 903         if (start == block_group->start)
 904                 goto right;
 905         key.objectid = start - 1;
 906         key.type = (u8)-1;
 907         key.offset = (u64)-1;
 908
 909         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 910         if (ret)
 911                 goto out;
 912
 913         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 914
 915         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
 916                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
 917                 btrfs_release_path(path);
 918                 goto right;
 919         }
 920
 921         found_start = key.objectid;
 922         found_end = key.objectid + key.offset;
 923         ASSERT(found_start >= block_group->start &&
 924                found_end > block_group->start);
 925         ASSERT(found_start < start && found_end <= start);
 926
 927         /*
 928          * Delete the neighbor on the left and absorb it into the new key (cases
 929          * 2 and 4).
 930          */
 931         if (found_end == start) {
 932                 ret = btrfs_del_item(trans, root, path);
 933                 if (ret)
 934                         goto out;
 935                 new_key.objectid = found_start;
 936                 new_key.offset += key.offset;
 937                 new_extents--;
 938         }
 939         btrfs_release_path(path);
 940
 941 right:
 942         /* Search for a neighbor on the right. */
 943         if (end == block_group->start + block_group->length)
 944                 goto insert;
 945         key.objectid = end;
 946         key.type = (u8)-1;
 947         key.offset = (u64)-1;
 948
 949         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 950         if (ret)
 951                 goto out;
 952
 953         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 954
 955         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
 956                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
 957                 btrfs_release_path(path);
 958                 goto insert;
 959         }
 960
 961         found_start = key.objectid;
 962         found_end = key.objectid + key.offset;
 963         ASSERT(found_start >= block_group->start &&
 964                found_end > block_group->start);
 965         ASSERT((found_start < start && found_end <= start) ||
 966                (found_start >= end && found_end > end));
 967
 968         /*
 969          * Delete the neighbor on the right and absorb it into the new key
 970          * (cases 3 and 4).
 971          */
 972         if (found_start == end) {
 973                 ret = btrfs_del_item(trans, root, path);
 974                 if (ret)
 975                         goto out;
 976                 new_key.offset += key.offset;
 977                 new_extents--;
 978         }
 979         btrfs_release_path(path);
 980
 981 insert:
 982         /* Insert the new key (cases 1-4). */
 983         ret = btrfs_insert_empty_item(trans, root, path, &new_key, 0);
 984         if (ret)
 985                 goto out;
 986
 987         btrfs_release_path(path);
 988         ret = update_free_space_extent_count(trans, block_group, path,
 989                                              new_extents);
 990
 991 out:
 992         return ret;
 993 }
 994
 995 EXPORT_FOR_TESTS
 996 int __add_to_free_space_tree(struct btrfs_trans_handle *trans,
 997                              struct btrfs_block_group *block_group,
 998                              struct btrfs_path *path, u64 start, u64 size)
 999 {
1000         struct btrfs_free_space_info *info;
1001         u32 flags;
1002         int ret;
1003
1004         if (test_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, &block_group->runtime_flags)) {
1005                 ret = __add_block_group_free_space(trans, block_group, path);
1006                 if (ret)
1007                         return ret;
1008         }
1009
1010         info = search_free_space_info(NULL, block_group, path, 0);
1011         if (IS_ERR(info))
1012                 return PTR_ERR(info);
1013         flags = btrfs_free_space_flags(path->nodes[0], info);
1014         btrfs_release_path(path);
1015
1016         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
1017                 return modify_free_space_bitmap(trans, block_group, path,
1018                                                 start, size, 0);
1019         } else {
1020                 return add_free_space_extent(trans, block_group, path, start,
1021                                              size);
1022         }
1023 }
1024
1025 int add_to_free_space_tree(struct btrfs_trans_handle *trans,
1026                            u64 start, u64 size)
1027 {
1028         struct btrfs_block_group *block_group;
1029         struct btrfs_path *path;
1030         int ret;
1031
1032         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1033                 return 0;
1034
1035         path = btrfs_alloc_path();
1036         if (!path) {
1037                 ret = -ENOMEM;
1038                 goto out;
1039         }
1040
1041         block_group = btrfs_lookup_block_group(trans->fs_info, start);
1042         if (!block_group) {
1043                 ASSERT(0);
1044                 ret = -ENOENT;
1045                 goto out;
1046         }
1047
1048         mutex_lock(&block_group->free_space_lock);
1049         ret = __add_to_free_space_tree(trans, block_group, path, start, size);
1050         mutex_unlock(&block_group->free_space_lock);
1051
1052         btrfs_put_block_group(block_group);
1053 out:
1054         btrfs_free_path(path);
1055         if (ret)
1056                 btrfs_abort_transaction(trans, ret);
1057         return ret;
1058 }
1059
1060 /*
1061  * Populate the free space tree by walking the extent tree. Operations on the
1062  * extent tree that happen as a result of writes to the free space tree will go
1063  * through the normal add/remove hooks.
1064  */
1065 static int populate_free_space_tree(struct btrfs_trans_handle *trans,
1066                                     struct btrfs_block_group *block_group)
1067 {
1068         struct btrfs_root *extent_root;
1069         struct btrfs_path *path, *path2;
1070         struct btrfs_key key;
1071         u64 start, end;
1072         int ret;
1073
1074         path = btrfs_alloc_path();
1075         if (!path)
1076                 return -ENOMEM;
1077         path->reada = READA_FORWARD;
1078
1079         path2 = btrfs_alloc_path();
1080         if (!path2) {
1081                 btrfs_free_path(path);
1082                 return -ENOMEM;
1083         }
1084
1085         ret = add_new_free_space_info(trans, block_group, path2);
1086         if (ret)
1087                 goto out;
1088
1089         mutex_lock(&block_group->free_space_lock);
1090
1091         /*
1092          * Iterate through all of the extent and metadata items in this block
1093          * group, adding the free space between them and the free space at the
1094          * end. Note that EXTENT_ITEM and METADATA_ITEM are less than
1095          * BLOCK_GROUP_ITEM, so an extent may precede the block group that it's
1096          * contained in.
1097          */
1098         key.objectid = block_group->start;
1099         key.type = BTRFS_EXTENT_ITEM_KEY;
1100         key.offset = 0;
1101
1102         extent_root = btrfs_extent_root(trans->fs_info, key.objectid);
1103         ret = btrfs_search_slot_for_read(extent_root, &key, path, 1, 0);
1104         if (ret < 0)
1105                 goto out_locked;
1106         ASSERT(ret == 0);
1107
1108         start = block_group->start;
1109         end = block_group->start + block_group->length;
1110         while (1) {
1111                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1112
1113                 if (key.type == BTRFS_EXTENT_ITEM_KEY ||
1114                     key.type == BTRFS_METADATA_ITEM_KEY) {
1115                         if (key.objectid >= end)
1116                                 break;
1117
1118                         if (start < key.objectid) {
1119                                 ret = __add_to_free_space_tree(trans,
1120                                                                block_group,
1121                                                                path2, start,
1122                                                                key.objectid -
1123                                                                start);
1124                                 if (ret)
1125                                         goto out_locked;
1126                         }
1127                         start = key.objectid;
1128                         if (key.type == BTRFS_METADATA_ITEM_KEY)
1129                                 start += trans->fs_info->nodesize;
1130                         else
1131                                 start += key.offset;
1132                 } else if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
1133                         if (key.objectid != block_group->start)
1134                                 break;
1135                 }
1136
1137                 ret = btrfs_next_item(extent_root, path);
1138                 if (ret < 0)
1139                         goto out_locked;
1140                 if (ret)
1141                         break;
1142         }
1143         if (start < end) {
1144                 ret = __add_to_free_space_tree(trans, block_group, path2,
1145                                                start, end - start);
1146                 if (ret)
1147                         goto out_locked;
1148         }
1149
1150         ret = 0;
1151 out_locked:
1152         mutex_unlock(&block_group->free_space_lock);
1153 out:
1154         btrfs_free_path(path2);
1155         btrfs_free_path(path);
1156         return ret;
1157 }
1158
1159 int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
1160 {
1161         struct btrfs_trans_handle *trans;
1162         struct btrfs_root *tree_root = fs_info->tree_root;
1163         struct btrfs_root *free_space_root;
1164         struct btrfs_block_group *block_group;
1165         struct rb_node *node;
1166         int ret;
1167
1168         trans = btrfs_start_transaction(tree_root, 0);
1169         if (IS_ERR(trans))
1170                 return PTR_ERR(trans);
1171
1172         set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1173         set_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
1174         free_space_root = btrfs_create_tree(trans,
1175                                             BTRFS_FREE_SPACE_TREE_OBJECTID);
1176         if (IS_ERR(free_space_root)) {
1177                 ret = PTR_ERR(free_space_root);
1178                 goto abort;
1179         }
1180         ret = btrfs_global_root_insert(free_space_root);
1181         if (ret) {
1182                 btrfs_put_root(free_space_root);
1183                 goto abort;
1184         }
1185
1186         node = rb_first_cached(&fs_info->block_group_cache_tree);
1187         while (node) {
1188                 block_group = rb_entry(node, struct btrfs_block_group,
1189                                        cache_node);
1190                 ret = populate_free_space_tree(trans, block_group);
1191                 if (ret)
1192                         goto abort;
1193                 node = rb_next(node);
1194         }
1195
1196         btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1197         btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1198         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1199         ret = btrfs_commit_transaction(trans);
1200
1201         /*
1202          * Now that we've committed the transaction any reading of our commit
1203          * root will be safe, so we can cache from the free space tree now.
1204          */
1205         clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
1206         return ret;
1207
1208 abort:
1209         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1210         clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
1211         btrfs_abort_transaction(trans, ret);
1212         btrfs_end_transaction(trans);
1213         return ret;
1214 }
1215
1216 static int clear_free_space_tree(struct btrfs_trans_handle *trans,
1217                                  struct btrfs_root *root)
1218 {
1219         struct btrfs_path *path;
1220         struct btrfs_key key;
1221         int nr;
1222         int ret;
1223
1224         path = btrfs_alloc_path();
1225         if (!path)
1226                 return -ENOMEM;
1227
1228         key.objectid = 0;
1229         key.type = 0;
1230         key.offset = 0;
1231
1232         while (1) {
1233                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
1234                 if (ret < 0)
1235                         goto out;
1236
1237                 nr = btrfs_header_nritems(path->nodes[0]);
1238                 if (!nr)
1239                         break;
1240
1241                 path->slots[0] = 0;
1242                 ret = btrfs_del_items(trans, root, path, 0, nr);
1243                 if (ret)
1244                         goto out;
1245
1246                 btrfs_release_path(path);
1247         }
1248
1249         ret = 0;
1250 out:
1251         btrfs_free_path(path);
1252         return ret;
1253 }
1254
1255 int btrfs_clear_free_space_tree(struct btrfs_fs_info *fs_info)
1256 {
1257         struct btrfs_trans_handle *trans;
1258         struct btrfs_root *tree_root = fs_info->tree_root;
1259         struct btrfs_key key = {
1260                 .objectid = BTRFS_FREE_SPACE_TREE_OBJECTID,
1261                 .type = BTRFS_ROOT_ITEM_KEY,
1262                 .offset = 0,
1263         };
1264         struct btrfs_root *free_space_root = btrfs_global_root(fs_info, &key);
1265         int ret;
1266
1267         trans = btrfs_start_transaction(tree_root, 0);
1268         if (IS_ERR(trans))
1269                 return PTR_ERR(trans);
1270
1271         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1272         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1273
1274         ret = clear_free_space_tree(trans, free_space_root);
1275         if (ret)
1276                 goto abort;
1277
1278         ret = btrfs_del_root(trans, &free_space_root->root_key);
1279         if (ret)
1280                 goto abort;
1281
1282         btrfs_global_root_delete(free_space_root);
1283         list_del(&free_space_root->dirty_list);
1284
1285         btrfs_tree_lock(free_space_root->node);
1286         btrfs_clean_tree_block(free_space_root->node);
1287         btrfs_tree_unlock(free_space_root->node);
1288         btrfs_free_tree_block(trans, btrfs_root_id(free_space_root),
1289                               free_space_root->node, 0, 1);
1290
1291         btrfs_put_root(free_space_root);
1292
1293         return btrfs_commit_transaction(trans);
1294
1295 abort:
1296         btrfs_abort_transaction(trans, ret);
1297         btrfs_end_transaction(trans);
1298         return ret;
1299 }
1300
1301 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
1302                                         struct btrfs_block_group *block_group,
1303                                         struct btrfs_path *path)
1304 {
1305         int ret;
1306
1307         clear_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, &block_group->runtime_flags);
1308
1309         ret = add_new_free_space_info(trans, block_group, path);
1310         if (ret)
1311                 return ret;
1312
1313         return __add_to_free_space_tree(trans, block_group, path,
1314                                         block_group->start,
1315                                         block_group->length);
1316 }
1317
1318 int add_block_group_free_space(struct btrfs_trans_handle *trans,
1319                                struct btrfs_block_group *block_group)
1320 {
1321         struct btrfs_fs_info *fs_info = trans->fs_info;
1322         struct btrfs_path *path = NULL;
1323         int ret = 0;
1324
1325         if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
1326                 return 0;
1327
1328         mutex_lock(&block_group->free_space_lock);
1329         if (!test_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, &block_group->runtime_flags))
1330                 goto out;
1331
1332         path = btrfs_alloc_path();
1333         if (!path) {
1334                 ret = -ENOMEM;
1335                 goto out;
1336         }
1337
1338         ret = __add_block_group_free_space(trans, block_group, path);
1339
1340 out:
1341         btrfs_free_path(path);
1342         mutex_unlock(&block_group->free_space_lock);
1343         if (ret)
1344                 btrfs_abort_transaction(trans, ret);
1345         return ret;
1346 }
1347
1348 int remove_block_group_free_space(struct btrfs_trans_handle *trans,
1349                                   struct btrfs_block_group *block_group)
1350 {
1351         struct btrfs_root *root = btrfs_free_space_root(block_group);
1352         struct btrfs_path *path;
1353         struct btrfs_key key, found_key;
1354         struct extent_buffer *leaf;
1355         u64 start, end;
1356         int done = 0, nr;
1357         int ret;
1358
1359         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1360                 return 0;
1361
1362         if (test_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, &block_group->runtime_flags)) {
1363                 /* We never added this block group to the free space tree. */
1364                 return 0;
1365         }
1366
1367         path = btrfs_alloc_path();
1368         if (!path) {
1369                 ret = -ENOMEM;
1370                 goto out;
1371         }
1372
1373         start = block_group->start;
1374         end = block_group->start + block_group->length;
1375
1376         key.objectid = end - 1;
1377         key.type = (u8)-1;
1378         key.offset = (u64)-1;
1379
1380         while (!done) {
1381                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
1382                 if (ret)
1383                         goto out;
1384
1385                 leaf = path->nodes[0];
1386                 nr = 0;
1387                 path->slots[0]++;
1388                 while (path->slots[0] > 0) {
1389                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
1390
1391                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
1392                                 ASSERT(found_key.objectid == block_group->start);
1393                                 ASSERT(found_key.offset == block_group->length);
1394                                 done = 1;
1395                                 nr++;
1396                                 path->slots[0]--;
1397                                 break;
1398                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY ||
1399                                    found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
1400                                 ASSERT(found_key.objectid >= start);
1401                                 ASSERT(found_key.objectid < end);
1402                                 ASSERT(found_key.objectid + found_key.offset <= end);
1403                                 nr++;
1404                                 path->slots[0]--;
1405                         } else {
1406                                 ASSERT(0);
1407                         }
1408                 }
1409
1410                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
1411                 if (ret)
1412                         goto out;
1413                 btrfs_release_path(path);
1414         }
1415
1416         ret = 0;
1417 out:
1418         btrfs_free_path(path);
1419         if (ret)
1420                 btrfs_abort_transaction(trans, ret);
1421         return ret;
1422 }
1423
1424 static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
1425                                    struct btrfs_path *path,
1426                                    u32 expected_extent_count)
1427 {
1428         struct btrfs_block_group *block_group;
1429         struct btrfs_fs_info *fs_info;
1430         struct btrfs_root *root;
1431         struct btrfs_key key;
1432         int prev_bit = 0, bit;
1433         /* Initialize to silence GCC. */
1434         u64 extent_start = 0;
1435         u64 end, offset;
1436         u64 total_found = 0;
1437         u32 extent_count = 0;
1438         int ret;
1439
1440         block_group = caching_ctl->block_group;
1441         fs_info = block_group->fs_info;
1442         root = btrfs_free_space_root(block_group);
1443
1444         end = block_group->start + block_group->length;
1445
1446         while (1) {
1447                 ret = btrfs_next_item(root, path);
1448                 if (ret < 0)
1449                         goto out;
1450                 if (ret)
1451                         break;
1452
1453                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1454
1455                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1456                         break;
1457
1458                 ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
1459                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1460
1461                 offset = key.objectid;
1462                 while (offset < key.objectid + key.offset) {
1463                         bit = free_space_test_bit(block_group, path, offset);
1464                         if (prev_bit == 0 && bit == 1) {
1465                                 extent_start = offset;
1466                         } else if (prev_bit == 1 && bit == 0) {
1467                                 total_found += add_new_free_space(block_group,
1468                                                                   extent_start,
1469                                                                   offset);
1470                                 if (total_found > CACHING_CTL_WAKE_UP) {
1471                                         total_found = 0;
1472                                         wake_up(&caching_ctl->wait);
1473                                 }
1474                                 extent_count++;
1475                         }
1476                         prev_bit = bit;
1477                         offset += fs_info->sectorsize;
1478                 }
1479         }
1480         if (prev_bit == 1) {
1481                 total_found += add_new_free_space(block_group, extent_start,
1482                                                   end);
1483                 extent_count++;
1484         }
1485
1486         if (extent_count != expected_extent_count) {
1487                 btrfs_err(fs_info,
1488                           "incorrect extent count for %llu; counted %u, expected %u",
1489                           block_group->start, extent_count,
1490                           expected_extent_count);
1491                 ASSERT(0);
1492                 ret = -EIO;
1493                 goto out;
1494         }
1495
1496         ret = 0;
1497 out:
1498         return ret;
1499 }
1500
1501 static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
1502                                    struct btrfs_path *path,
1503                                    u32 expected_extent_count)
1504 {
1505         struct btrfs_block_group *block_group;
1506         struct btrfs_fs_info *fs_info;
1507         struct btrfs_root *root;
1508         struct btrfs_key key;
1509         u64 end;
1510         u64 total_found = 0;
1511         u32 extent_count = 0;
1512         int ret;
1513
1514         block_group = caching_ctl->block_group;
1515         fs_info = block_group->fs_info;
1516         root = btrfs_free_space_root(block_group);
1517
1518         end = block_group->start + block_group->length;
1519
1520         while (1) {
1521                 ret = btrfs_next_item(root, path);
1522                 if (ret < 0)
1523                         goto out;
1524                 if (ret)
1525                         break;
1526
1527                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1528
1529                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1530                         break;
1531
1532                 ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
1533                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1534
1535                 total_found += add_new_free_space(block_group, key.objectid,
1536                                                   key.objectid + key.offset);
1537                 if (total_found > CACHING_CTL_WAKE_UP) {
1538                         total_found = 0;
1539                         wake_up(&caching_ctl->wait);
1540                 }
1541                 extent_count++;
1542         }
1543
1544         if (extent_count != expected_extent_count) {
1545                 btrfs_err(fs_info,
1546                           "incorrect extent count for %llu; counted %u, expected %u",
1547                           block_group->start, extent_count,
1548                           expected_extent_count);
1549                 ASSERT(0);
1550                 ret = -EIO;
1551                 goto out;
1552         }
1553
1554         ret = 0;
1555 out:
1556         return ret;
1557 }
1558
1559 int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
1560 {
1561         struct btrfs_block_group *block_group;
1562         struct btrfs_free_space_info *info;
1563         struct btrfs_path *path;
1564         u32 extent_count, flags;
1565         int ret;
1566
1567         block_group = caching_ctl->block_group;
1568
1569         path = btrfs_alloc_path();
1570         if (!path)
1571                 return -ENOMEM;
1572
1573         /*
1574          * Just like caching_thread() doesn't want to deadlock on the extent
1575          * tree, we don't want to deadlock on the free space tree.
1576          */
1577         path->skip_locking = 1;
1578         path->search_commit_root = 1;
1579         path->reada = READA_FORWARD;
1580
1581         info = search_free_space_info(NULL, block_group, path, 0);
1582         if (IS_ERR(info)) {
1583                 ret = PTR_ERR(info);
1584                 goto out;
1585         }
1586         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
1587         flags = btrfs_free_space_flags(path->nodes[0], info);
1588
1589         /*
1590          * We left path pointing to the free space info item, so now
1591          * load_free_space_foo can just iterate through the free space tree from
1592          * there.
1593          */
1594         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS)
1595                 ret = load_free_space_bitmaps(caching_ctl, path, extent_count);
1596         else
1597                 ret = load_free_space_extents(caching_ctl, path, extent_count);
1598
1599 out:
1600         btrfs_free_path(path);
1601         return ret;
1602 }