fs/btrfs/free-space-cache.c

   1 /*
   2  * Copyright (C) 2008 Red Hat.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/pagemap.h>
  20 #include <linux/sched.h>
  21 #include <linux/math64.h>
  22 #include "ctree.h"
  23 #include "free-space-cache.h"
  24 #include "transaction.h"
  25
  26 #define BITS_PER_BITMAP         (PAGE_CACHE_SIZE * 8)
  27 #define MAX_CACHE_BYTES_PER_GIG (32 * 1024)
  28
  29 static inline unsigned long offset_to_bit(u64 bitmap_start, u64 sectorsize,
  30                                           u64 offset)
  31 {
  32         BUG_ON(offset < bitmap_start);
  33         offset -= bitmap_start;
  34         return (unsigned long)(div64_u64(offset, sectorsize));
  35 }
  36
  37 static inline unsigned long bytes_to_bits(u64 bytes, u64 sectorsize)
  38 {
  39         return (unsigned long)(div64_u64(bytes, sectorsize));
  40 }
  41
  42 static inline u64 offset_to_bitmap(struct btrfs_block_group_cache *block_group,
  43                                    u64 offset)
  44 {
  45         u64 bitmap_start;
  46         u64 bytes_per_bitmap;
  47
  48         bytes_per_bitmap = BITS_PER_BITMAP * block_group->sectorsize;
  49         bitmap_start = offset - block_group->key.objectid;
  50         bitmap_start = div64_u64(bitmap_start, bytes_per_bitmap);
  51         bitmap_start *= bytes_per_bitmap;
  52         bitmap_start += block_group->key.objectid;
  53
  54         return bitmap_start;
  55 }
  56
  57 static int tree_insert_offset(struct rb_root *root, u64 offset,
  58                               struct rb_node *node, int bitmap)
  59 {
  60         struct rb_node **p = &root->rb_node;
  61         struct rb_node *parent = NULL;
  62         struct btrfs_free_space *info;
  63
  64         while (*p) {
  65                 parent = *p;
  66                 info = rb_entry(parent, struct btrfs_free_space, offset_index);
  67
  68                 if (offset < info->offset) {
  69                         p = &(*p)->rb_left;
  70                 } else if (offset > info->offset) {
  71                         p = &(*p)->rb_right;
  72                 } else {
  73                         /*
  74                          * we could have a bitmap entry and an extent entry
  75                          * share the same offset.  If this is the case, we want
  76                          * the extent entry to always be found first if we do a
  77                          * linear search through the tree, since we want to have
  78                          * the quickest allocation time, and allocating from an
  79                          * extent is faster than allocating from a bitmap.  So
  80                          * if we're inserting a bitmap and we find an entry at
  81                          * this offset, we want to go right, or after this entry
  82                          * logically.  If we are inserting an extent and we've
  83                          * found a bitmap, we want to go left, or before
  84                          * logically.
  85                          */
  86                         if (bitmap) {
  87                                 WARN_ON(info->bitmap);
  88                                 p = &(*p)->rb_right;
  89                         } else {
  90                                 WARN_ON(!info->bitmap);
  91                                 p = &(*p)->rb_left;
  92                         }
  93                 }
  94         }
  95
  96         rb_link_node(node, parent, p);
  97         rb_insert_color(node, root);
  98
  99         return 0;
 100 }
 101
 102 /*
 103  * searches the tree for the given offset.
 104  *
 105  * fuzzy - If this is set, then we are trying to make an allocation, and we just
 106  * want a section that has at least bytes size and comes at or after the given
 107  * offset.
 108  */
 109 static struct btrfs_free_space *
 110 tree_search_offset(struct btrfs_block_group_cache *block_group,
 111                    u64 offset, int bitmap_only, int fuzzy)
 112 {
 113         struct rb_node *n = block_group->free_space_offset.rb_node;
 114         struct btrfs_free_space *entry, *prev = NULL;
 115
 116         /* find entry that is closest to the 'offset' */
 117         while (1) {
 118                 if (!n) {
 119                         entry = NULL;
 120                         break;
 121                 }
 122
 123                 entry = rb_entry(n, struct btrfs_free_space, offset_index);
 124                 prev = entry;
 125
 126                 if (offset < entry->offset)
 127                         n = n->rb_left;
 128                 else if (offset > entry->offset)
 129                         n = n->rb_right;
 130                 else
 131                         break;
 132         }
 133
 134         if (bitmap_only) {
 135                 if (!entry)
 136                         return NULL;
 137                 if (entry->bitmap)
 138                         return entry;
 139
 140                 /*
 141                  * bitmap entry and extent entry may share same offset,
 142                  * in that case, bitmap entry comes after extent entry.
 143                  */
 144                 n = rb_next(n);
 145                 if (!n)
 146                         return NULL;
 147                 entry = rb_entry(n, struct btrfs_free_space, offset_index);
 148                 if (entry->offset != offset)
 149                         return NULL;
 150
 151                 WARN_ON(!entry->bitmap);
 152                 return entry;
 153         } else if (entry) {
 154                 if (entry->bitmap) {
 155                         /*
 156                          * if previous extent entry covers the offset,
 157                          * we should return it instead of the bitmap entry
 158                          */
 159                         n = &entry->offset_index;
 160                         while (1) {
 161                                 n = rb_prev(n);
 162                                 if (!n)
 163                                         break;
 164                                 prev = rb_entry(n, struct btrfs_free_space,
 165                                                 offset_index);
 166                                 if (!prev->bitmap) {
 167                                         if (prev->offset + prev->bytes > offset)
 168                                                 entry = prev;
 169                                         break;
 170                                 }
 171                         }
 172                 }
 173                 return entry;
 174         }
 175
 176         if (!prev)
 177                 return NULL;
 178
 179         /* find last entry before the 'offset' */
 180         entry = prev;
 181         if (entry->offset > offset) {
 182                 n = rb_prev(&entry->offset_index);
 183                 if (n) {
 184                         entry = rb_entry(n, struct btrfs_free_space,
 185                                         offset_index);
 186                         BUG_ON(entry->offset > offset);
 187                 } else {
 188                         if (fuzzy)
 189                                 return entry;
 190                         else
 191                                 return NULL;
 192                 }
 193         }
 194
 195         if (entry->bitmap) {
 196                 n = &entry->offset_index;
 197                 while (1) {
 198                         n = rb_prev(n);
 199                         if (!n)
 200                                 break;
 201                         prev = rb_entry(n, struct btrfs_free_space,
 202                                         offset_index);
 203                         if (!prev->bitmap) {
 204                                 if (prev->offset + prev->bytes > offset)
 205                                         return prev;
 206                                 break;
 207                         }
 208                 }
 209                 if (entry->offset + BITS_PER_BITMAP *
 210                     block_group->sectorsize > offset)
 211                         return entry;
 212         } else if (entry->offset + entry->bytes > offset)
 213                 return entry;
 214
 215         if (!fuzzy)
 216                 return NULL;
 217
 218         while (1) {
 219                 if (entry->bitmap) {
 220                         if (entry->offset + BITS_PER_BITMAP *
 221                             block_group->sectorsize > offset)
 222                                 break;
 223                 } else {
 224                         if (entry->offset + entry->bytes > offset)
 225                                 break;
 226                 }
 227
 228                 n = rb_next(&entry->offset_index);
 229                 if (!n)
 230                         return NULL;
 231                 entry = rb_entry(n, struct btrfs_free_space, offset_index);
 232         }
 233         return entry;
 234 }
 235
 236 static void unlink_free_space(struct btrfs_block_group_cache *block_group,
 237                               struct btrfs_free_space *info)
 238 {
 239         rb_erase(&info->offset_index, &block_group->free_space_offset);
 240         block_group->free_extents--;
 241         block_group->free_space -= info->bytes;
 242 }
 243
 244 static int link_free_space(struct btrfs_block_group_cache *block_group,
 245                            struct btrfs_free_space *info)
 246 {
 247         int ret = 0;
 248
 249         BUG_ON(!info->bitmap && !info->bytes);
 250         ret = tree_insert_offset(&block_group->free_space_offset, info->offset,
 251                                  &info->offset_index, (info->bitmap != NULL));
 252         if (ret)
 253                 return ret;
 254
 255         block_group->free_space += info->bytes;
 256         block_group->free_extents++;
 257         return ret;
 258 }
 259
 260 static void recalculate_thresholds(struct btrfs_block_group_cache *block_group)
 261 {
 262         u64 max_bytes, possible_bytes;
 263
 264         /*
 265          * The goal is to keep the total amount of memory used per 1gb of space
 266          * at or below 32k, so we need to adjust how much memory we allow to be
 267          * used by extent based free space tracking
 268          */
 269         max_bytes = MAX_CACHE_BYTES_PER_GIG *
 270                 (div64_u64(block_group->key.offset, 1024 * 1024 * 1024));
 271
 272         possible_bytes = (block_group->total_bitmaps * PAGE_CACHE_SIZE) +
 273                 (sizeof(struct btrfs_free_space) *
 274                  block_group->extents_thresh);
 275
 276         if (possible_bytes > max_bytes) {
 277                 int extent_bytes = max_bytes -
 278                         (block_group->total_bitmaps * PAGE_CACHE_SIZE);
 279
 280                 if (extent_bytes <= 0) {
 281                         block_group->extents_thresh = 0;
 282                         return;
 283                 }
 284
 285                 block_group->extents_thresh = extent_bytes /
 286                         (sizeof(struct btrfs_free_space));
 287         }
 288 }
 289
 290 static void bitmap_clear_bits(struct btrfs_block_group_cache *block_group,
 291                               struct btrfs_free_space *info, u64 offset,
 292                               u64 bytes)
 293 {
 294         unsigned long start, end;
 295         unsigned long i;
 296
 297         start = offset_to_bit(info->offset, block_group->sectorsize, offset);
 298         end = start + bytes_to_bits(bytes, block_group->sectorsize);
 299         BUG_ON(end > BITS_PER_BITMAP);
 300
 301         for (i = start; i < end; i++)
 302                 clear_bit(i, info->bitmap);
 303
 304         info->bytes -= bytes;
 305         block_group->free_space -= bytes;
 306 }
 307
 308 static void bitmap_set_bits(struct btrfs_block_group_cache *block_group,
 309                             struct btrfs_free_space *info, u64 offset,
 310                             u64 bytes)
 311 {
 312         unsigned long start, end;
 313         unsigned long i;
 314
 315         start = offset_to_bit(info->offset, block_group->sectorsize, offset);
 316         end = start + bytes_to_bits(bytes, block_group->sectorsize);
 317         BUG_ON(end > BITS_PER_BITMAP);
 318
 319         for (i = start; i < end; i++)
 320                 set_bit(i, info->bitmap);
 321
 322         info->bytes += bytes;
 323         block_group->free_space += bytes;
 324 }
 325
 326 static int search_bitmap(struct btrfs_block_group_cache *block_group,
 327                          struct btrfs_free_space *bitmap_info, u64 *offset,
 328                          u64 *bytes)
 329 {
 330         unsigned long found_bits = 0;
 331         unsigned long bits, i;
 332         unsigned long next_zero;
 333
 334         i = offset_to_bit(bitmap_info->offset, block_group->sectorsize,
 335                           max_t(u64, *offset, bitmap_info->offset));
 336         bits = bytes_to_bits(*bytes, block_group->sectorsize);
 337
 338         for (i = find_next_bit(bitmap_info->bitmap, BITS_PER_BITMAP, i);
 339              i < BITS_PER_BITMAP;
 340              i = find_next_bit(bitmap_info->bitmap, BITS_PER_BITMAP, i + 1)) {
 341                 next_zero = find_next_zero_bit(bitmap_info->bitmap,
 342                                                BITS_PER_BITMAP, i);
 343                 if ((next_zero - i) >= bits) {
 344                         found_bits = next_zero - i;
 345                         break;
 346                 }
 347                 i = next_zero;
 348         }
 349
 350         if (found_bits) {
 351                 *offset = (u64)(i * block_group->sectorsize) +
 352                         bitmap_info->offset;
 353                 *bytes = (u64)(found_bits) * block_group->sectorsize;
 354                 return 0;
 355         }
 356
 357         return -1;
 358 }
 359
 360 static struct btrfs_free_space *find_free_space(struct btrfs_block_group_cache
 361                                                 *block_group, u64 *offset,
 362                                                 u64 *bytes, int debug)
 363 {
 364         struct btrfs_free_space *entry;
 365         struct rb_node *node;
 366         int ret;
 367
 368         if (!block_group->free_space_offset.rb_node)
 369                 return NULL;
 370
 371         entry = tree_search_offset(block_group,
 372                                    offset_to_bitmap(block_group, *offset),
 373                                    0, 1);
 374         if (!entry)
 375                 return NULL;
 376
 377         for (node = &entry->offset_index; node; node = rb_next(node)) {
 378                 entry = rb_entry(node, struct btrfs_free_space, offset_index);
 379                 if (entry->bytes < *bytes)
 380                         continue;
 381
 382                 if (entry->bitmap) {
 383                         ret = search_bitmap(block_group, entry, offset, bytes);
 384                         if (!ret)
 385                                 return entry;
 386                         continue;
 387                 }
 388
 389                 *offset = entry->offset;
 390                 *bytes = entry->bytes;
 391                 return entry;
 392         }
 393
 394         return NULL;
 395 }
 396
 397 static void add_new_bitmap(struct btrfs_block_group_cache *block_group,
 398                            struct btrfs_free_space *info, u64 offset)
 399 {
 400         u64 bytes_per_bg = BITS_PER_BITMAP * block_group->sectorsize;
 401         int max_bitmaps = (int)div64_u64(block_group->key.offset +
 402                                          bytes_per_bg - 1, bytes_per_bg);
 403         BUG_ON(block_group->total_bitmaps >= max_bitmaps);
 404
 405         info->offset = offset_to_bitmap(block_group, offset);
 406         link_free_space(block_group, info);
 407         block_group->total_bitmaps++;
 408
 409         recalculate_thresholds(block_group);
 410 }
 411
 412 static noinline int remove_from_bitmap(struct btrfs_block_group_cache *block_group,
 413                               struct btrfs_free_space *bitmap_info,
 414                               u64 *offset, u64 *bytes)
 415 {
 416         u64 end;
 417
 418 again:
 419         end = bitmap_info->offset +
 420                 (u64)(BITS_PER_BITMAP * block_group->sectorsize) - 1;
 421
 422         if (*offset > bitmap_info->offset && *offset + *bytes > end) {
 423                 bitmap_clear_bits(block_group, bitmap_info, *offset,
 424                                   end - *offset + 1);
 425                 *bytes -= end - *offset + 1;
 426                 *offset = end + 1;
 427         } else if (*offset >= bitmap_info->offset && *offset + *bytes <= end) {
 428                 bitmap_clear_bits(block_group, bitmap_info, *offset, *bytes);
 429                 *bytes = 0;
 430         }
 431
 432         if (*bytes) {
 433                 if (!bitmap_info->bytes) {
 434                         unlink_free_space(block_group, bitmap_info);
 435                         kfree(bitmap_info->bitmap);
 436                         kfree(bitmap_info);
 437                         block_group->total_bitmaps--;
 438                         recalculate_thresholds(block_group);
 439                 }
 440
 441                 bitmap_info = tree_search_offset(block_group,
 442                                                  offset_to_bitmap(block_group,
 443                                                                   *offset),
 444                                                  1, 0);
 445                 if (!bitmap_info)
 446                         return -EINVAL;
 447
 448                 if (!bitmap_info->bitmap)
 449                         return -EAGAIN;
 450
 451                 goto again;
 452         } else if (!bitmap_info->bytes) {
 453                 unlink_free_space(block_group, bitmap_info);
 454                 kfree(bitmap_info->bitmap);
 455                 kfree(bitmap_info);
 456                 block_group->total_bitmaps--;
 457                 recalculate_thresholds(block_group);
 458         }
 459
 460         return 0;
 461 }
 462
 463 static int insert_into_bitmap(struct btrfs_block_group_cache *block_group,
 464                               struct btrfs_free_space *info)
 465 {
 466         struct btrfs_free_space *bitmap_info;
 467         int added = 0;
 468         u64 bytes, offset, end;
 469         int ret;
 470
 471         /*
 472          * If we are below the extents threshold then we can add this as an
 473          * extent, and don't have to deal with the bitmap
 474          */
 475         if (block_group->free_extents < block_group->extents_thresh &&
 476             info->bytes > block_group->sectorsize * 4)
 477                 return 0;
 478
 479         /*
 480          * some block groups are so tiny they can't be enveloped by a bitmap, so
 481          * don't even bother to create a bitmap for this
 482          */
 483         if (BITS_PER_BITMAP * block_group->sectorsize >
 484             block_group->key.offset)
 485                 return 0;
 486
 487         bytes = info->bytes;
 488         offset = info->offset;
 489
 490 again:
 491         bitmap_info = tree_search_offset(block_group,
 492                                          offset_to_bitmap(block_group, offset),
 493                                          1, 0);
 494         if (!bitmap_info) {
 495                 BUG_ON(added);
 496                 goto new_bitmap;
 497         }
 498
 499         end = bitmap_info->offset +
 500                 (u64)(BITS_PER_BITMAP * block_group->sectorsize);
 501
 502         if (offset >= bitmap_info->offset && offset + bytes > end) {
 503                 bitmap_set_bits(block_group, bitmap_info, offset,
 504                                 end - offset);
 505                 bytes -= end - offset;
 506                 offset = end;
 507                 added = 0;
 508         } else if (offset >= bitmap_info->offset && offset + bytes <= end) {
 509                 bitmap_set_bits(block_group, bitmap_info, offset, bytes);
 510                 bytes = 0;
 511         } else {
 512                 BUG();
 513         }
 514
 515         if (!bytes) {
 516                 ret = 1;
 517                 goto out;
 518         } else
 519                 goto again;
 520
 521 new_bitmap:
 522         if (info && info->bitmap) {
 523                 add_new_bitmap(block_group, info, offset);
 524                 added = 1;
 525                 info = NULL;
 526                 goto again;
 527         } else {
 528                 spin_unlock(&block_group->tree_lock);
 529
 530                 /* no pre-allocated info, allocate a new one */
 531                 if (!info) {
 532                         info = kzalloc(sizeof(struct btrfs_free_space),
 533                                        GFP_NOFS);
 534                         if (!info) {
 535                                 spin_lock(&block_group->tree_lock);
 536                                 ret = -ENOMEM;
 537                                 goto out;
 538                         }
 539                 }
 540
 541                 /* allocate the bitmap */
 542                 info->bitmap = kzalloc(PAGE_CACHE_SIZE, GFP_NOFS);
 543                 spin_lock(&block_group->tree_lock);
 544                 if (!info->bitmap) {
 545                         ret = -ENOMEM;
 546                         goto out;
 547                 }
 548                 goto again;
 549         }
 550
 551 out:
 552         if (info) {
 553                 if (info->bitmap)
 554                         kfree(info->bitmap);
 555                 kfree(info);
 556         }
 557
 558         return ret;
 559 }
 560
 561 int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
 562                          u64 offset, u64 bytes)
 563 {
 564         struct btrfs_free_space *right_info = NULL;
 565         struct btrfs_free_space *left_info = NULL;
 566         struct btrfs_free_space *info = NULL;
 567         int ret = 0;
 568
 569         info = kzalloc(sizeof(struct btrfs_free_space), GFP_NOFS);
 570         if (!info)
 571                 return -ENOMEM;
 572
 573         info->offset = offset;
 574         info->bytes = bytes;
 575
 576         spin_lock(&block_group->tree_lock);
 577
 578         /*
 579          * first we want to see if there is free space adjacent to the range we
 580          * are adding, if there is remove that struct and add a new one to
 581          * cover the entire range
 582          */
 583         right_info = tree_search_offset(block_group, offset + bytes, 0, 0);
 584         if (right_info && rb_prev(&right_info->offset_index))
 585                 left_info = rb_entry(rb_prev(&right_info->offset_index),
 586                                      struct btrfs_free_space, offset_index);
 587         else
 588                 left_info = tree_search_offset(block_group, offset - 1, 0, 0);
 589
 590         /*
 591          * If there was no extent directly to the left or right of this new
 592          * extent then we know we're going to have to allocate a new extent, so
 593          * before we do that see if we need to drop this into a bitmap
 594          */
 595         if ((!left_info || left_info->bitmap) &&
 596             (!right_info || right_info->bitmap)) {
 597                 ret = insert_into_bitmap(block_group, info);
 598
 599                 if (ret < 0) {
 600                         goto out;
 601                 } else if (ret) {
 602                         ret = 0;
 603                         goto out;
 604                 }
 605         }
 606
 607         if (right_info && !right_info->bitmap) {
 608                 unlink_free_space(block_group, right_info);
 609                 info->bytes += right_info->bytes;
 610                 kfree(right_info);
 611         }
 612
 613         if (left_info && !left_info->bitmap &&
 614             left_info->offset + left_info->bytes == offset) {
 615                 unlink_free_space(block_group, left_info);
 616                 info->offset = left_info->offset;
 617                 info->bytes += left_info->bytes;
 618                 kfree(left_info);
 619         }
 620
 621         ret = link_free_space(block_group, info);
 622         if (ret)
 623                 kfree(info);
 624 out:
 625         spin_unlock(&block_group->tree_lock);
 626
 627         if (ret) {
 628                 printk(KERN_CRIT "btrfs: unable to add free space :%d\n", ret);
 629                 BUG_ON(ret == -EEXIST);
 630         }
 631
 632         return ret;
 633 }
 634
 635 int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
 636                             u64 offset, u64 bytes)
 637 {
 638         struct btrfs_free_space *info;
 639         struct btrfs_free_space *next_info = NULL;
 640         int ret = 0;
 641
 642         spin_lock(&block_group->tree_lock);
 643
 644 again:
 645         info = tree_search_offset(block_group, offset, 0, 0);
 646         if (!info) {
 647                 WARN_ON(1);
 648                 goto out_lock;
 649         }
 650
 651         if (info->bytes < bytes && rb_next(&info->offset_index)) {
 652                 u64 end;
 653                 next_info = rb_entry(rb_next(&info->offset_index),
 654                                              struct btrfs_free_space,
 655                                              offset_index);
 656
 657                 if (next_info->bitmap)
 658                         end = next_info->offset + BITS_PER_BITMAP *
 659                                 block_group->sectorsize - 1;
 660                 else
 661                         end = next_info->offset + next_info->bytes;
 662
 663                 if (next_info->bytes < bytes ||
 664                     next_info->offset > offset || offset > end) {
 665                         printk(KERN_CRIT "Found free space at %llu, size %llu,"
 666                               " trying to use %llu\n",
 667                               (unsigned long long)info->offset,
 668                               (unsigned long long)info->bytes,
 669                               (unsigned long long)bytes);
 670                         WARN_ON(1);
 671                         ret = -EINVAL;
 672                         goto out_lock;
 673                 }
 674
 675                 info = next_info;
 676         }
 677
 678         if (info->bytes == bytes) {
 679                 unlink_free_space(block_group, info);
 680                 if (info->bitmap) {
 681                         kfree(info->bitmap);
 682                         block_group->total_bitmaps--;
 683                 }
 684                 kfree(info);
 685                 goto out_lock;
 686         }
 687
 688         if (!info->bitmap && info->offset == offset) {
 689                 unlink_free_space(block_group, info);
 690                 info->offset += bytes;
 691                 info->bytes -= bytes;
 692                 link_free_space(block_group, info);
 693                 goto out_lock;
 694         }
 695
 696         if (!info->bitmap && info->offset <= offset &&
 697             info->offset + info->bytes >= offset + bytes) {
 698                 u64 old_start = info->offset;
 699                 /*
 700                  * we're freeing space in the middle of the info,
 701                  * this can happen during tree log replay
 702                  *
 703                  * first unlink the old info and then
 704                  * insert it again after the hole we're creating
 705                  */
 706                 unlink_free_space(block_group, info);
 707                 if (offset + bytes < info->offset + info->bytes) {
 708                         u64 old_end = info->offset + info->bytes;
 709
 710                         info->offset = offset + bytes;
 711                         info->bytes = old_end - info->offset;
 712                         ret = link_free_space(block_group, info);
 713                         WARN_ON(ret);
 714                         if (ret)
 715                                 goto out_lock;
 716                 } else {
 717                         /* the hole we're creating ends at the end
 718                          * of the info struct, just free the info
 719                          */
 720                         kfree(info);
 721                 }
 722                 spin_unlock(&block_group->tree_lock);
 723
 724                 /* step two, insert a new info struct to cover
 725                  * anything before the hole
 726                  */
 727                 ret = btrfs_add_free_space(block_group, old_start,
 728                                            offset - old_start);
 729                 WARN_ON(ret);
 730                 goto out;
 731         }
 732
 733         ret = remove_from_bitmap(block_group, info, &offset, &bytes);
 734         if (ret == -EAGAIN)
 735                 goto again;
 736         BUG_ON(ret);
 737 out_lock:
 738         spin_unlock(&block_group->tree_lock);
 739 out:
 740         return ret;
 741 }
 742
 743 void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
 744                            u64 bytes)
 745 {
 746         struct btrfs_free_space *info;
 747         struct rb_node *n;
 748         int count = 0;
 749
 750         for (n = rb_first(&block_group->free_space_offset); n; n = rb_next(n)) {
 751                 info = rb_entry(n, struct btrfs_free_space, offset_index);
 752                 if (info->bytes >= bytes)
 753                         count++;
 754                 printk(KERN_CRIT "entry offset %llu, bytes %llu, bitmap %s\n",
 755                        (unsigned long long)info->offset,
 756                        (unsigned long long)info->bytes,
 757                        (info->bitmap) ? "yes" : "no");
 758         }
 759         printk(KERN_INFO "block group has cluster?: %s\n",
 760                list_empty(&block_group->cluster_list) ? "no" : "yes");
 761         printk(KERN_INFO "%d blocks of free space at or bigger than bytes is"
 762                "\n", count);
 763 }
 764
 765 u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group)
 766 {
 767         struct btrfs_free_space *info;
 768         struct rb_node *n;
 769         u64 ret = 0;
 770
 771         for (n = rb_first(&block_group->free_space_offset); n;
 772              n = rb_next(n)) {
 773                 info = rb_entry(n, struct btrfs_free_space, offset_index);
 774                 ret += info->bytes;
 775         }
 776
 777         return ret;
 778 }
 779
 780 /*
 781  * for a given cluster, put all of its extents back into the free
 782  * space cache.  If the block group passed doesn't match the block group
 783  * pointed to by the cluster, someone else raced in and freed the
 784  * cluster already.  In that case, we just return without changing anything
 785  */
 786 static int
 787 __btrfs_return_cluster_to_free_space(
 788                              struct btrfs_block_group_cache *block_group,
 789                              struct btrfs_free_cluster *cluster)
 790 {
 791         struct btrfs_free_space *entry;
 792         struct rb_node *node;
 793         bool bitmap;
 794
 795         spin_lock(&cluster->lock);
 796         if (cluster->block_group != block_group)
 797                 goto out;
 798
 799         bitmap = cluster->points_to_bitmap;
 800         cluster->block_group = NULL;
 801         cluster->window_start = 0;
 802         list_del_init(&cluster->block_group_list);
 803         cluster->points_to_bitmap = false;
 804
 805         if (bitmap)
 806                 goto out;
 807
 808         node = rb_first(&cluster->root);
 809         while (node) {
 810                 entry = rb_entry(node, struct btrfs_free_space, offset_index);
 811                 node = rb_next(&entry->offset_index);
 812                 rb_erase(&entry->offset_index, &cluster->root);
 813                 BUG_ON(entry->bitmap);
 814                 tree_insert_offset(&block_group->free_space_offset,
 815                                    entry->offset, &entry->offset_index, 0);
 816         }
 817         cluster->root.rb_node = NULL;
 818
 819 out:
 820         spin_unlock(&cluster->lock);
 821         btrfs_put_block_group(block_group);
 822         return 0;
 823 }
 824
 825 void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
 826 {
 827         struct btrfs_free_space *info;
 828         struct rb_node *node;
 829         struct btrfs_free_cluster *cluster;
 830         struct list_head *head;
 831
 832         spin_lock(&block_group->tree_lock);
 833         while ((head = block_group->cluster_list.next) !=
 834                &block_group->cluster_list) {
 835                 cluster = list_entry(head, struct btrfs_free_cluster,
 836                                      block_group_list);
 837
 838                 WARN_ON(cluster->block_group != block_group);
 839                 __btrfs_return_cluster_to_free_space(block_group, cluster);
 840                 if (need_resched()) {
 841                         spin_unlock(&block_group->tree_lock);
 842                         cond_resched();
 843                         spin_lock(&block_group->tree_lock);
 844                 }
 845         }
 846
 847         while ((node = rb_last(&block_group->free_space_offset)) != NULL) {
 848                 info = rb_entry(node, struct btrfs_free_space, offset_index);
 849                 unlink_free_space(block_group, info);
 850                 if (info->bitmap)
 851                         kfree(info->bitmap);
 852                 kfree(info);
 853                 if (need_resched()) {
 854                         spin_unlock(&block_group->tree_lock);
 855                         cond_resched();
 856                         spin_lock(&block_group->tree_lock);
 857                 }
 858         }
 859
 860         spin_unlock(&block_group->tree_lock);
 861 }
 862
 863 u64 btrfs_find_space_for_alloc(struct btrfs_block_group_cache *block_group,
 864                                u64 offset, u64 bytes, u64 empty_size)
 865 {
 866         struct btrfs_free_space *entry = NULL;
 867         u64 bytes_search = bytes + empty_size;
 868         u64 ret = 0;
 869
 870         spin_lock(&block_group->tree_lock);
 871         entry = find_free_space(block_group, &offset, &bytes_search, 0);
 872         if (!entry)
 873                 goto out;
 874
 875         ret = offset;
 876         if (entry->bitmap) {
 877                 bitmap_clear_bits(block_group, entry, offset, bytes);
 878                 if (!entry->bytes) {
 879                         unlink_free_space(block_group, entry);
 880                         kfree(entry->bitmap);
 881                         kfree(entry);
 882                         block_group->total_bitmaps--;
 883                         recalculate_thresholds(block_group);
 884                 }
 885         } else {
 886                 unlink_free_space(block_group, entry);
 887                 entry->offset += bytes;
 888                 entry->bytes -= bytes;
 889                 if (!entry->bytes)
 890                         kfree(entry);
 891                 else
 892                         link_free_space(block_group, entry);
 893         }
 894
 895 out:
 896         spin_unlock(&block_group->tree_lock);
 897
 898         return ret;
 899 }
 900
 901 /*
 902  * given a cluster, put all of its extents back into the free space
 903  * cache.  If a block group is passed, this function will only free
 904  * a cluster that belongs to the passed block group.
 905  *
 906  * Otherwise, it'll get a reference on the block group pointed to by the
 907  * cluster and remove the cluster from it.
 908  */
 909 int btrfs_return_cluster_to_free_space(
 910                                struct btrfs_block_group_cache *block_group,
 911                                struct btrfs_free_cluster *cluster)
 912 {
 913         int ret;
 914
 915         /* first, get a safe pointer to the block group */
 916         spin_lock(&cluster->lock);
 917         if (!block_group) {
 918                 block_group = cluster->block_group;
 919                 if (!block_group) {
 920                         spin_unlock(&cluster->lock);
 921                         return 0;
 922                 }
 923         } else if (cluster->block_group != block_group) {
 924                 /* someone else has already freed it don't redo their work */
 925                 spin_unlock(&cluster->lock);
 926                 return 0;
 927         }
 928         atomic_inc(&block_group->count);
 929         spin_unlock(&cluster->lock);
 930
 931         /* now return any extents the cluster had on it */
 932         spin_lock(&block_group->tree_lock);
 933         ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
 934         spin_unlock(&block_group->tree_lock);
 935
 936         /* finally drop our ref */
 937         btrfs_put_block_group(block_group);
 938         return ret;
 939 }
 940
 941 static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
 942                                    struct btrfs_free_cluster *cluster,
 943                                    u64 bytes, u64 min_start)
 944 {
 945         struct btrfs_free_space *entry;
 946         int err;
 947         u64 search_start = cluster->window_start;
 948         u64 search_bytes = bytes;
 949         u64 ret = 0;
 950
 951         spin_lock(&block_group->tree_lock);
 952         spin_lock(&cluster->lock);
 953
 954         if (!cluster->points_to_bitmap)
 955                 goto out;
 956
 957         if (cluster->block_group != block_group)
 958                 goto out;
 959
 960         entry = tree_search_offset(block_group, search_start, 0, 0);
 961
 962         if (!entry || !entry->bitmap)
 963                 goto out;
 964
 965         search_start = min_start;
 966         search_bytes = bytes;
 967
 968         err = search_bitmap(block_group, entry, &search_start,
 969                             &search_bytes);
 970         if (err)
 971                 goto out;
 972
 973         ret = search_start;
 974         bitmap_clear_bits(block_group, entry, ret, bytes);
 975 out:
 976         spin_unlock(&cluster->lock);
 977         spin_unlock(&block_group->tree_lock);
 978
 979         return ret;
 980 }
 981
 982 /*
 983  * given a cluster, try to allocate 'bytes' from it, returns 0
 984  * if it couldn't find anything suitably large, or a logical disk offset
 985  * if things worked out
 986  */
 987 u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
 988                              struct btrfs_free_cluster *cluster, u64 bytes,
 989                              u64 min_start)
 990 {
 991         struct btrfs_free_space *entry = NULL;
 992         struct rb_node *node;
 993         u64 ret = 0;
 994
 995         if (cluster->points_to_bitmap)
 996                 return btrfs_alloc_from_bitmap(block_group, cluster, bytes,
 997                                                min_start);
 998
 999         spin_lock(&cluster->lock);
1000         if (bytes > cluster->max_size)
1001                 goto out;
1002
1003         if (cluster->block_group != block_group)
1004                 goto out;
1005
1006         node = rb_first(&cluster->root);
1007         if (!node)
1008                 goto out;
1009
1010         entry = rb_entry(node, struct btrfs_free_space, offset_index);
1011
1012         while(1) {
1013                 if (entry->bytes < bytes || entry->offset < min_start) {
1014                         struct rb_node *node;
1015
1016                         node = rb_next(&entry->offset_index);
1017                         if (!node)
1018                                 break;
1019                         entry = rb_entry(node, struct btrfs_free_space,
1020                                          offset_index);
1021                         continue;
1022                 }
1023                 ret = entry->offset;
1024
1025                 entry->offset += bytes;
1026                 entry->bytes -= bytes;
1027
1028                 if (entry->bytes == 0) {
1029                         rb_erase(&entry->offset_index, &cluster->root);
1030                         kfree(entry);
1031                 }
1032                 break;
1033         }
1034 out:
1035         spin_unlock(&cluster->lock);
1036
1037         return ret;
1038 }
1039
1040 static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
1041                                 struct btrfs_free_space *entry,
1042                                 struct btrfs_free_cluster *cluster,
1043                                 u64 offset, u64 bytes, u64 min_bytes)
1044 {
1045         unsigned long next_zero;
1046         unsigned long i;
1047         unsigned long search_bits;
1048         unsigned long total_bits;
1049         unsigned long found_bits;
1050         unsigned long start = 0;
1051         unsigned long total_found = 0;
1052         bool found = false;
1053
1054         i = offset_to_bit(entry->offset, block_group->sectorsize,
1055                           max_t(u64, offset, entry->offset));
1056         search_bits = bytes_to_bits(min_bytes, block_group->sectorsize);
1057         total_bits = bytes_to_bits(bytes, block_group->sectorsize);
1058
1059 again:
1060         found_bits = 0;
1061         for (i = find_next_bit(entry->bitmap, BITS_PER_BITMAP, i);
1062              i < BITS_PER_BITMAP;
1063              i = find_next_bit(entry->bitmap, BITS_PER_BITMAP, i + 1)) {
1064                 next_zero = find_next_zero_bit(entry->bitmap,
1065                                                BITS_PER_BITMAP, i);
1066                 if (next_zero - i >= search_bits) {
1067                         found_bits = next_zero - i;
1068                         break;
1069                 }
1070                 i = next_zero;
1071         }
1072
1073         if (!found_bits)
1074                 return -1;
1075
1076         if (!found) {
1077                 start = i;
1078                 found = true;
1079         }
1080
1081         total_found += found_bits;
1082
1083         if (cluster->max_size < found_bits * block_group->sectorsize)
1084                 cluster->max_size = found_bits * block_group->sectorsize;
1085
1086         if (total_found < total_bits) {
1087                 i = find_next_bit(entry->bitmap, BITS_PER_BITMAP, next_zero);
1088                 if (i - start > total_bits * 2) {
1089                         total_found = 0;
1090                         cluster->max_size = 0;
1091                         found = false;
1092                 }
1093                 goto again;
1094         }
1095
1096         cluster->window_start = start * block_group->sectorsize +
1097                 entry->offset;
1098         cluster->points_to_bitmap = true;
1099
1100         return 0;
1101 }
1102
1103 /*
1104  * here we try to find a cluster of blocks in a block group.  The goal
1105  * is to find at least bytes free and up to empty_size + bytes free.
1106  * We might not find them all in one contiguous area.
1107  *
1108  * returns zero and sets up cluster if things worked out, otherwise
1109  * it returns -enospc
1110  */
1111 int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
1112                              struct btrfs_root *root,
1113                              struct btrfs_block_group_cache *block_group,
1114                              struct btrfs_free_cluster *cluster,
1115                              u64 offset, u64 bytes, u64 empty_size)
1116 {
1117         struct btrfs_free_space *entry = NULL;
1118         struct rb_node *node;
1119         struct btrfs_free_space *next;
1120         struct btrfs_free_space *last = NULL;
1121         u64 min_bytes;
1122         u64 window_start;
1123         u64 window_free;
1124         u64 max_extent = 0;
1125         bool found_bitmap = false;
1126         int ret;
1127
1128         /* for metadata, allow allocates with more holes */
1129         if (btrfs_test_opt(root, SSD_SPREAD)) {
1130                 min_bytes = bytes + empty_size;
1131         } else if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
1132                 /*
1133                  * we want to do larger allocations when we are
1134                  * flushing out the delayed refs, it helps prevent
1135                  * making more work as we go along.
1136                  */
1137                 if (trans->transaction->delayed_refs.flushing)
1138                         min_bytes = max(bytes, (bytes + empty_size) >> 1);
1139                 else
1140                         min_bytes = max(bytes, (bytes + empty_size) >> 4);
1141         } else
1142                 min_bytes = max(bytes, (bytes + empty_size) >> 2);
1143
1144         spin_lock(&block_group->tree_lock);
1145         spin_lock(&cluster->lock);
1146
1147         /* someone already found a cluster, hooray */
1148         if (cluster->block_group) {
1149                 ret = 0;
1150                 goto out;
1151         }
1152 again:
1153         entry = tree_search_offset(block_group, offset, found_bitmap, 1);
1154         if (!entry) {
1155                 ret = -ENOSPC;
1156                 goto out;
1157         }
1158
1159         /*
1160          * If found_bitmap is true, we exhausted our search for extent entries,
1161          * and we just want to search all of the bitmaps that we can find, and
1162          * ignore any extent entries we find.
1163          */
1164         while (entry->bitmap || found_bitmap ||
1165                (!entry->bitmap && entry->bytes < min_bytes)) {
1166                 struct rb_node *node = rb_next(&entry->offset_index);
1167
1168                 if (entry->bitmap && entry->bytes > bytes + empty_size) {
1169                         ret = btrfs_bitmap_cluster(block_group, entry, cluster,
1170                                                    offset, bytes + empty_size,
1171                                                    min_bytes);
1172                         if (!ret)
1173                                 goto got_it;
1174                 }
1175
1176                 if (!node) {
1177                         ret = -ENOSPC;
1178                         goto out;
1179                 }
1180                 entry = rb_entry(node, struct btrfs_free_space, offset_index);
1181         }
1182
1183         /*
1184          * We already searched all the extent entries from the passed in offset
1185          * to the end and didn't find enough space for the cluster, and we also
1186          * didn't find any bitmaps that met our criteria, just go ahead and exit
1187          */
1188         if (found_bitmap) {
1189                 ret = -ENOSPC;
1190                 goto out;
1191         }
1192
1193         cluster->points_to_bitmap = false;
1194         window_start = entry->offset;
1195         window_free = entry->bytes;
1196         last = entry;
1197         max_extent = entry->bytes;
1198
1199         while (1) {
1200                 /* out window is just right, lets fill it */
1201                 if (window_free >= bytes + empty_size)
1202                         break;
1203
1204                 node = rb_next(&last->offset_index);
1205                 if (!node) {
1206                         if (found_bitmap)
1207                                 goto again;
1208                         ret = -ENOSPC;
1209                         goto out;
1210                 }
1211                 next = rb_entry(node, struct btrfs_free_space, offset_index);
1212
1213                 /*
1214                  * we found a bitmap, so if this search doesn't result in a
1215                  * cluster, we know to go and search again for the bitmaps and
1216                  * start looking for space there
1217                  */
1218                 if (next->bitmap) {
1219                         if (!found_bitmap)
1220                                 offset = next->offset;
1221                         found_bitmap = true;
1222                         last = next;
1223                         continue;
1224                 }
1225
1226                 /*
1227                  * we haven't filled the empty size and the window is
1228                  * very large.  reset and try again
1229                  */
1230                 if (next->offset - (last->offset + last->bytes) > 128 * 1024 ||
1231                     next->offset - window_start > (bytes + empty_size) * 2) {
1232                         entry = next;
1233                         window_start = entry->offset;
1234                         window_free = entry->bytes;
1235                         last = entry;
1236                         max_extent = 0;
1237                 } else {
1238                         last = next;
1239                         window_free += next->bytes;
1240                         if (entry->bytes > max_extent)
1241                                 max_extent = entry->bytes;
1242                 }
1243         }
1244
1245         cluster->window_start = entry->offset;
1246
1247         /*
1248          * now we've found our entries, pull them out of the free space
1249          * cache and put them into the cluster rbtree
1250          *
1251          * The cluster includes an rbtree, but only uses the offset index
1252          * of each free space cache entry.
1253          */
1254         while (1) {
1255                 node = rb_next(&entry->offset_index);
1256                 if (entry->bitmap && node) {
1257                         entry = rb_entry(node, struct btrfs_free_space,
1258                                          offset_index);
1259                         continue;
1260                 } else if (entry->bitmap && !node) {
1261                         break;
1262                 }
1263
1264                 rb_erase(&entry->offset_index, &block_group->free_space_offset);
1265                 ret = tree_insert_offset(&cluster->root, entry->offset,
1266                                          &entry->offset_index, 0);
1267                 BUG_ON(ret);
1268
1269                 if (!node || entry == last)
1270                         break;
1271
1272                 entry = rb_entry(node, struct btrfs_free_space, offset_index);
1273         }
1274
1275         cluster->max_size = max_extent;
1276 got_it:
1277         ret = 0;
1278         atomic_inc(&block_group->count);
1279         list_add_tail(&cluster->block_group_list, &block_group->cluster_list);
1280         cluster->block_group = block_group;
1281 out:
1282         spin_unlock(&cluster->lock);
1283         spin_unlock(&block_group->tree_lock);
1284
1285         return ret;
1286 }
1287
1288 /*
1289  * simple code to zero out a cluster
1290  */
1291 void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
1292 {
1293         spin_lock_init(&cluster->lock);
1294         spin_lock_init(&cluster->refill_lock);
1295         cluster->root.rb_node = NULL;
1296         cluster->max_size = 0;
1297         cluster->points_to_bitmap = false;
1298         INIT_LIST_HEAD(&cluster->block_group_list);
1299         cluster->block_group = NULL;
1300 }
1301