root/fs/btrfs/extent_map.c

DEFINITIONS

1. extent_map_init
2. extent_map_exit
3. extent_map_tree_init
4. alloc_extent_map
5. free_extent_map
6. range_end
7. tree_insert
8. __tree_search
9. mergable_maps
10. try_merge_map
11. unpin_extent_cache
12. clear_em_logging
13. setup_extent_mapping
14. extent_map_device_set_bits
15. extent_map_device_clear_bits
16. add_extent_mapping
17. __lookup_extent_mapping
18. lookup_extent_mapping
19. search_extent_mapping
20. remove_extent_mapping
21. replace_extent_mapping
22. next_extent_map
23. prev_extent_map
24. merge_extent_mapping
25. btrfs_add_extent_mapping

   1 // SPDX-License-Identifier: GPL-2.0
   2 
   3 #include <linux/err.h>
   4 #include <linux/slab.h>
   5 #include <linux/spinlock.h>
   6 #include "ctree.h"
   7 #include "volumes.h"
   8 #include "extent_map.h"
   9 #include "compression.h"
  10 
  11 
  12 static struct kmem_cache *extent_map_cache;
  13 
  14 int __init extent_map_init(void)
  15 {
  16         extent_map_cache = kmem_cache_create("btrfs_extent_map",
  17                         sizeof(struct extent_map), 0,
  18                         SLAB_MEM_SPREAD, NULL);
  19         if (!extent_map_cache)
  20                 return -ENOMEM;
  21         return 0;
  22 }
  23 
  24 void __cold extent_map_exit(void)
  25 {
  26         kmem_cache_destroy(extent_map_cache);
  27 }
  28 
  29 /**
  30  * extent_map_tree_init - initialize extent map tree
  31  * @tree:               tree to initialize
  32  *
  33  * Initialize the extent tree @tree.  Should be called for each new inode
  34  * or other user of the extent_map interface.
  35  */
  36 void extent_map_tree_init(struct extent_map_tree *tree)
  37 {
  38         tree->map = RB_ROOT_CACHED;
  39         INIT_LIST_HEAD(&tree->modified_extents);
  40         rwlock_init(&tree->lock);
  41 }
  42 
  43 /**
  44  * alloc_extent_map - allocate new extent map structure
  45  *
  46  * Allocate a new extent_map structure.  The new structure is
  47  * returned with a reference count of one and needs to be
  48  * freed using free_extent_map()
  49  */
  50 struct extent_map *alloc_extent_map(void)
  51 {
  52         struct extent_map *em;
  53         em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
  54         if (!em)
  55                 return NULL;
  56         RB_CLEAR_NODE(&em->rb_node);
  57         em->flags = 0;
  58         em->compress_type = BTRFS_COMPRESS_NONE;
  59         em->generation = 0;
  60         refcount_set(&em->refs, 1);
  61         INIT_LIST_HEAD(&em->list);
  62         return em;
  63 }
  64 
  65 /**
  66  * free_extent_map - drop reference count of an extent_map
  67  * @em:         extent map being released
  68  *
  69  * Drops the reference out on @em by one and free the structure
  70  * if the reference count hits zero.
  71  */
  72 void free_extent_map(struct extent_map *em)
  73 {
  74         if (!em)
  75                 return;
  76         WARN_ON(refcount_read(&em->refs) == 0);
  77         if (refcount_dec_and_test(&em->refs)) {
  78                 WARN_ON(extent_map_in_tree(em));
  79                 WARN_ON(!list_empty(&em->list));
  80                 if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
  81                         kfree(em->map_lookup);
  82                 kmem_cache_free(extent_map_cache, em);
  83         }
  84 }
  85 
  86 /* simple helper to do math around the end of an extent, handling wrap */
  87 static u64 range_end(u64 start, u64 len)
  88 {
  89         if (start + len < start)
  90                 return (u64)-1;
  91         return start + len;
  92 }
  93 
  94 static int tree_insert(struct rb_root_cached *root, struct extent_map *em)
  95 {
  96         struct rb_node **p = &root->rb_root.rb_node;
  97         struct rb_node *parent = NULL;
  98         struct extent_map *entry = NULL;
  99         struct rb_node *orig_parent = NULL;
 100         u64 end = range_end(em->start, em->len);
 101         bool leftmost = true;
 102 
 103         while (*p) {
 104                 parent = *p;
 105                 entry = rb_entry(parent, struct extent_map, rb_node);
 106 
 107                 if (em->start < entry->start) {
 108                         p = &(*p)->rb_left;
 109                 } else if (em->start >= extent_map_end(entry)) {
 110                         p = &(*p)->rb_right;
 111                         leftmost = false;
 112                 } else {
 113                         return -EEXIST;
 114                 }
 115         }
 116 
 117         orig_parent = parent;
 118         while (parent && em->start >= extent_map_end(entry)) {
 119                 parent = rb_next(parent);
 120                 entry = rb_entry(parent, struct extent_map, rb_node);
 121         }
 122         if (parent)
 123                 if (end > entry->start && em->start < extent_map_end(entry))
 124                         return -EEXIST;
 125 
 126         parent = orig_parent;
 127         entry = rb_entry(parent, struct extent_map, rb_node);
 128         while (parent && em->start < entry->start) {
 129                 parent = rb_prev(parent);
 130                 entry = rb_entry(parent, struct extent_map, rb_node);
 131         }
 132         if (parent)
 133                 if (end > entry->start && em->start < extent_map_end(entry))
 134                         return -EEXIST;
 135 
 136         rb_link_node(&em->rb_node, orig_parent, p);
 137         rb_insert_color_cached(&em->rb_node, root, leftmost);
 138         return 0;
 139 }
 140 
 141 /*
 142  * search through the tree for an extent_map with a given offset.  If
 143  * it can't be found, try to find some neighboring extents
 144  */
 145 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 146                                      struct rb_node **prev_ret,
 147                                      struct rb_node **next_ret)
 148 {
 149         struct rb_node *n = root->rb_node;
 150         struct rb_node *prev = NULL;
 151         struct rb_node *orig_prev = NULL;
 152         struct extent_map *entry;
 153         struct extent_map *prev_entry = NULL;
 154 
 155         while (n) {
 156                 entry = rb_entry(n, struct extent_map, rb_node);
 157                 prev = n;
 158                 prev_entry = entry;
 159 
 160                 if (offset < entry->start)
 161                         n = n->rb_left;
 162                 else if (offset >= extent_map_end(entry))
 163                         n = n->rb_right;
 164                 else
 165                         return n;
 166         }
 167 
 168         if (prev_ret) {
 169                 orig_prev = prev;
 170                 while (prev && offset >= extent_map_end(prev_entry)) {
 171                         prev = rb_next(prev);
 172                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 173                 }
 174                 *prev_ret = prev;
 175                 prev = orig_prev;
 176         }
 177 
 178         if (next_ret) {
 179                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 180                 while (prev && offset < prev_entry->start) {
 181                         prev = rb_prev(prev);
 182                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 183                 }
 184                 *next_ret = prev;
 185         }
 186         return NULL;
 187 }
 188 
 189 /* check to see if two extent_map structs are adjacent and safe to merge */
 190 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 191 {
 192         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 193                 return 0;
 194 
 195         /*
 196          * don't merge compressed extents, we need to know their
 197          * actual size
 198          */
 199         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 200                 return 0;
 201 
 202         if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
 203             test_bit(EXTENT_FLAG_LOGGING, &next->flags))
 204                 return 0;
 205 
 206         /*
 207          * We don't want to merge stuff that hasn't been written to the log yet
 208          * since it may not reflect exactly what is on disk, and that would be
 209          * bad.
 210          */
 211         if (!list_empty(&prev->list) || !list_empty(&next->list))
 212                 return 0;
 213 
 214         ASSERT(next->block_start != EXTENT_MAP_DELALLOC &&
 215                prev->block_start != EXTENT_MAP_DELALLOC);
 216 
 217         if (extent_map_end(prev) == next->start &&
 218             prev->flags == next->flags &&
 219             prev->bdev == next->bdev &&
 220             ((next->block_start == EXTENT_MAP_HOLE &&
 221               prev->block_start == EXTENT_MAP_HOLE) ||
 222              (next->block_start == EXTENT_MAP_INLINE &&
 223               prev->block_start == EXTENT_MAP_INLINE) ||
 224              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 225               next->block_start == extent_map_block_end(prev)))) {
 226                 return 1;
 227         }
 228         return 0;
 229 }
 230 
 231 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
 232 {
 233         struct extent_map *merge = NULL;
 234         struct rb_node *rb;
 235 
 236         /*
 237          * We can't modify an extent map that is in the tree and that is being
 238          * used by another task, as it can cause that other task to see it in
 239          * inconsistent state during the merging. We always have 1 reference for
 240          * the tree and 1 for this task (which is unpinning the extent map or
 241          * clearing the logging flag), so anything > 2 means it's being used by
 242          * other tasks too.
 243          */
 244         if (refcount_read(&em->refs) > 2)
 245                 return;
 246 
 247         if (em->start != 0) {
 248                 rb = rb_prev(&em->rb_node);
 249                 if (rb)
 250                         merge = rb_entry(rb, struct extent_map, rb_node);
 251                 if (rb && mergable_maps(merge, em)) {
 252                         em->start = merge->start;
 253                         em->orig_start = merge->orig_start;
 254                         em->len += merge->len;
 255                         em->block_len += merge->block_len;
 256                         em->block_start = merge->block_start;
 257                         em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
 258                         em->mod_start = merge->mod_start;
 259                         em->generation = max(em->generation, merge->generation);
 260 
 261                         rb_erase_cached(&merge->rb_node, &tree->map);
 262                         RB_CLEAR_NODE(&merge->rb_node);
 263                         free_extent_map(merge);
 264                 }
 265         }
 266 
 267         rb = rb_next(&em->rb_node);
 268         if (rb)
 269                 merge = rb_entry(rb, struct extent_map, rb_node);
 270         if (rb && mergable_maps(em, merge)) {
 271                 em->len += merge->len;
 272                 em->block_len += merge->block_len;
 273                 rb_erase_cached(&merge->rb_node, &tree->map);
 274                 RB_CLEAR_NODE(&merge->rb_node);
 275                 em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
 276                 em->generation = max(em->generation, merge->generation);
 277                 free_extent_map(merge);
 278         }
 279 }
 280 
 281 /**
 282  * unpin_extent_cache - unpin an extent from the cache
 283  * @tree:       tree to unpin the extent in
 284  * @start:      logical offset in the file
 285  * @len:        length of the extent
 286  * @gen:        generation that this extent has been modified in
 287  *
 288  * Called after an extent has been written to disk properly.  Set the generation
 289  * to the generation that actually added the file item to the inode so we know
 290  * we need to sync this extent when we call fsync().
 291  */
 292 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
 293                        u64 gen)
 294 {
 295         int ret = 0;
 296         struct extent_map *em;
 297         bool prealloc = false;
 298 
 299         write_lock(&tree->lock);
 300         em = lookup_extent_mapping(tree, start, len);
 301 
 302         WARN_ON(!em || em->start != start);
 303 
 304         if (!em)
 305                 goto out;
 306 
 307         em->generation = gen;
 308         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 309         em->mod_start = em->start;
 310         em->mod_len = em->len;
 311 
 312         if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
 313                 prealloc = true;
 314                 clear_bit(EXTENT_FLAG_FILLING, &em->flags);
 315         }
 316 
 317         try_merge_map(tree, em);
 318 
 319         if (prealloc) {
 320                 em->mod_start = em->start;
 321                 em->mod_len = em->len;
 322         }
 323 
 324         free_extent_map(em);
 325 out:
 326         write_unlock(&tree->lock);
 327         return ret;
 328 
 329 }
 330 
 331 void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
 332 {
 333         clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
 334         if (extent_map_in_tree(em))
 335                 try_merge_map(tree, em);
 336 }
 337 
 338 static inline void setup_extent_mapping(struct extent_map_tree *tree,
 339                                         struct extent_map *em,
 340                                         int modified)
 341 {
 342         refcount_inc(&em->refs);
 343         em->mod_start = em->start;
 344         em->mod_len = em->len;
 345 
 346         if (modified)
 347                 list_move(&em->list, &tree->modified_extents);
 348         else
 349                 try_merge_map(tree, em);
 350 }
 351 
 352 static void extent_map_device_set_bits(struct extent_map *em, unsigned bits)
 353 {
 354         struct map_lookup *map = em->map_lookup;
 355         u64 stripe_size = em->orig_block_len;
 356         int i;
 357 
 358         for (i = 0; i < map->num_stripes; i++) {
 359                 struct btrfs_bio_stripe *stripe = &map->stripes[i];
 360                 struct btrfs_device *device = stripe->dev;
 361 
 362                 set_extent_bits_nowait(&device->alloc_state, stripe->physical,
 363                                  stripe->physical + stripe_size - 1, bits);
 364         }
 365 }
 366 
 367 static void extent_map_device_clear_bits(struct extent_map *em, unsigned bits)
 368 {
 369         struct map_lookup *map = em->map_lookup;
 370         u64 stripe_size = em->orig_block_len;
 371         int i;
 372 
 373         for (i = 0; i < map->num_stripes; i++) {
 374                 struct btrfs_bio_stripe *stripe = &map->stripes[i];
 375                 struct btrfs_device *device = stripe->dev;
 376 
 377                 __clear_extent_bit(&device->alloc_state, stripe->physical,
 378                                    stripe->physical + stripe_size - 1, bits,
 379                                    0, 0, NULL, GFP_NOWAIT, NULL);
 380         }
 381 }
 382 
 383 /**
 384  * add_extent_mapping - add new extent map to the extent tree
 385  * @tree:       tree to insert new map in
 386  * @em:         map to insert
 387  *
 388  * Insert @em into @tree or perform a simple forward/backward merge with
 389  * existing mappings.  The extent_map struct passed in will be inserted
 390  * into the tree directly, with an additional reference taken, or a
 391  * reference dropped if the merge attempt was successful.
 392  */
 393 int add_extent_mapping(struct extent_map_tree *tree,
 394                        struct extent_map *em, int modified)
 395 {
 396         int ret = 0;
 397 
 398         lockdep_assert_held_write(&tree->lock);
 399 
 400         ret = tree_insert(&tree->map, em);
 401         if (ret)
 402                 goto out;
 403 
 404         setup_extent_mapping(tree, em, modified);
 405         if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags)) {
 406                 extent_map_device_set_bits(em, CHUNK_ALLOCATED);
 407                 extent_map_device_clear_bits(em, CHUNK_TRIMMED);
 408         }
 409 out:
 410         return ret;
 411 }
 412 
 413 static struct extent_map *
 414 __lookup_extent_mapping(struct extent_map_tree *tree,
 415                         u64 start, u64 len, int strict)
 416 {
 417         struct extent_map *em;
 418         struct rb_node *rb_node;
 419         struct rb_node *prev = NULL;
 420         struct rb_node *next = NULL;
 421         u64 end = range_end(start, len);
 422 
 423         rb_node = __tree_search(&tree->map.rb_root, start, &prev, &next);
 424         if (!rb_node) {
 425                 if (prev)
 426                         rb_node = prev;
 427                 else if (next)
 428                         rb_node = next;
 429                 else
 430                         return NULL;
 431         }
 432 
 433         em = rb_entry(rb_node, struct extent_map, rb_node);
 434 
 435         if (strict && !(end > em->start && start < extent_map_end(em)))
 436                 return NULL;
 437 
 438         refcount_inc(&em->refs);
 439         return em;
 440 }
 441 
 442 /**
 443  * lookup_extent_mapping - lookup extent_map
 444  * @tree:       tree to lookup in
 445  * @start:      byte offset to start the search
 446  * @len:        length of the lookup range
 447  *
 448  * Find and return the first extent_map struct in @tree that intersects the
 449  * [start, len] range.  There may be additional objects in the tree that
 450  * intersect, so check the object returned carefully to make sure that no
 451  * additional lookups are needed.
 452  */
 453 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 454                                          u64 start, u64 len)
 455 {
 456         return __lookup_extent_mapping(tree, start, len, 1);
 457 }
 458 
 459 /**
 460  * search_extent_mapping - find a nearby extent map
 461  * @tree:       tree to lookup in
 462  * @start:      byte offset to start the search
 463  * @len:        length of the lookup range
 464  *
 465  * Find and return the first extent_map struct in @tree that intersects the
 466  * [start, len] range.
 467  *
 468  * If one can't be found, any nearby extent may be returned
 469  */
 470 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
 471                                          u64 start, u64 len)
 472 {
 473         return __lookup_extent_mapping(tree, start, len, 0);
 474 }
 475 
 476 /**
 477  * remove_extent_mapping - removes an extent_map from the extent tree
 478  * @tree:       extent tree to remove from
 479  * @em:         extent map being removed
 480  *
 481  * Removes @em from @tree.  No reference counts are dropped, and no checks
 482  * are done to see if the range is in use
 483  */
 484 void remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 485 {
 486         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 487         rb_erase_cached(&em->rb_node, &tree->map);
 488         if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
 489                 list_del_init(&em->list);
 490         if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
 491                 extent_map_device_clear_bits(em, CHUNK_ALLOCATED);
 492         RB_CLEAR_NODE(&em->rb_node);
 493 }
 494 
 495 void replace_extent_mapping(struct extent_map_tree *tree,
 496                             struct extent_map *cur,
 497                             struct extent_map *new,
 498                             int modified)
 499 {
 500         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
 501         ASSERT(extent_map_in_tree(cur));
 502         if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
 503                 list_del_init(&cur->list);
 504         rb_replace_node_cached(&cur->rb_node, &new->rb_node, &tree->map);
 505         RB_CLEAR_NODE(&cur->rb_node);
 506 
 507         setup_extent_mapping(tree, new, modified);
 508 }
 509 
 510 static struct extent_map *next_extent_map(struct extent_map *em)
 511 {
 512         struct rb_node *next;
 513 
 514         next = rb_next(&em->rb_node);
 515         if (!next)
 516                 return NULL;
 517         return container_of(next, struct extent_map, rb_node);
 518 }
 519 
 520 static struct extent_map *prev_extent_map(struct extent_map *em)
 521 {
 522         struct rb_node *prev;
 523 
 524         prev = rb_prev(&em->rb_node);
 525         if (!prev)
 526                 return NULL;
 527         return container_of(prev, struct extent_map, rb_node);
 528 }
 529 
 530 /*
 531  * Helper for btrfs_get_extent.  Given an existing extent in the tree,
 532  * the existing extent is the nearest extent to map_start,
 533  * and an extent that you want to insert, deal with overlap and insert
 534  * the best fitted new extent into the tree.
 535  */
 536 static noinline int merge_extent_mapping(struct extent_map_tree *em_tree,
 537                                          struct extent_map *existing,
 538                                          struct extent_map *em,
 539                                          u64 map_start)
 540 {
 541         struct extent_map *prev;
 542         struct extent_map *next;
 543         u64 start;
 544         u64 end;
 545         u64 start_diff;
 546 
 547         BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
 548 
 549         if (existing->start > map_start) {
 550                 next = existing;
 551                 prev = prev_extent_map(next);
 552         } else {
 553                 prev = existing;
 554                 next = next_extent_map(prev);
 555         }
 556 
 557         start = prev ? extent_map_end(prev) : em->start;
 558         start = max_t(u64, start, em->start);
 559         end = next ? next->start : extent_map_end(em);
 560         end = min_t(u64, end, extent_map_end(em));
 561         start_diff = start - em->start;
 562         em->start = start;
 563         em->len = end - start;
 564         if (em->block_start < EXTENT_MAP_LAST_BYTE &&
 565             !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
 566                 em->block_start += start_diff;
 567                 em->block_len = em->len;
 568         }
 569         return add_extent_mapping(em_tree, em, 0);
 570 }
 571 
 572 /**
 573  * btrfs_add_extent_mapping - add extent mapping into em_tree
 574  * @fs_info - used for tracepoint
 575  * @em_tree - the extent tree into which we want to insert the extent mapping
 576  * @em_in   - extent we are inserting
 577  * @start   - start of the logical range btrfs_get_extent() is requesting
 578  * @len     - length of the logical range btrfs_get_extent() is requesting
 579  *
 580  * Note that @em_in's range may be different from [start, start+len),
 581  * but they must be overlapped.
 582  *
 583  * Insert @em_in into @em_tree. In case there is an overlapping range, handle
 584  * the -EEXIST by either:
 585  * a) Returning the existing extent in @em_in if @start is within the
 586  *    existing em.
 587  * b) Merge the existing extent with @em_in passed in.
 588  *
 589  * Return 0 on success, otherwise -EEXIST.
 590  *
 591  */
 592 int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
 593                              struct extent_map_tree *em_tree,
 594                              struct extent_map **em_in, u64 start, u64 len)
 595 {
 596         int ret;
 597         struct extent_map *em = *em_in;
 598 
 599         ret = add_extent_mapping(em_tree, em, 0);
 600         /* it is possible that someone inserted the extent into the tree
 601          * while we had the lock dropped.  It is also possible that
 602          * an overlapping map exists in the tree
 603          */
 604         if (ret == -EEXIST) {
 605                 struct extent_map *existing;
 606 
 607                 ret = 0;
 608 
 609                 existing = search_extent_mapping(em_tree, start, len);
 610 
 611                 trace_btrfs_handle_em_exist(fs_info, existing, em, start, len);
 612 
 613                 /*
 614                  * existing will always be non-NULL, since there must be
 615                  * extent causing the -EEXIST.
 616                  */
 617                 if (start >= existing->start &&
 618                     start < extent_map_end(existing)) {
 619                         free_extent_map(em);
 620                         *em_in = existing;
 621                         ret = 0;
 622                 } else {
 623                         u64 orig_start = em->start;
 624                         u64 orig_len = em->len;
 625 
 626                         /*
 627                          * The existing extent map is the one nearest to
 628                          * the [start, start + len) range which overlaps
 629                          */
 630                         ret = merge_extent_mapping(em_tree, existing,
 631                                                    em, start);
 632                         if (ret) {
 633                                 free_extent_map(em);
 634                                 *em_in = NULL;
 635                                 WARN_ONCE(ret,
 636 "unexpected error %d: merge existing(start %llu len %llu) with em(start %llu len %llu)\n",
 637                                           ret, existing->start, existing->len,
 638                                           orig_start, orig_len);
 639                         }
 640                         free_extent_map(existing);
 641                 }
 642         }
 643 
 644         ASSERT(ret == 0 || ret == -EEXIST);
 645         return ret;
 646 }