fs/btrfs/extent_map.c

   1 #include <linux/err.h>
   2 #include <linux/slab.h>
   3 #include <linux/spinlock.h>
   4 #include <linux/hardirq.h>
   5 #include "ctree.h"
   6 #include "extent_map.h"
   7
   8
   9 static struct kmem_cache *extent_map_cache;
  10
  11 int __init extent_map_init(void)
  12 {
  13         extent_map_cache = kmem_cache_create("btrfs_extent_map",
  14                         sizeof(struct extent_map), 0,
  15                         SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
  16         if (!extent_map_cache)
  17                 return -ENOMEM;
  18         return 0;
  19 }
  20
  21 void extent_map_exit(void)
  22 {
  23         if (extent_map_cache)
  24                 kmem_cache_destroy(extent_map_cache);
  25 }
  26
  27 /**
  28  * extent_map_tree_init - initialize extent map tree
  29  * @tree:               tree to initialize
  30  *
  31  * Initialize the extent tree @tree.  Should be called for each new inode
  32  * or other user of the extent_map interface.
  33  */
  34 void extent_map_tree_init(struct extent_map_tree *tree)
  35 {
  36         tree->map = RB_ROOT;
  37         INIT_LIST_HEAD(&tree->modified_extents);
  38         rwlock_init(&tree->lock);
  39 }
  40
  41 /**
  42  * alloc_extent_map - allocate new extent map structure
  43  *
  44  * Allocate a new extent_map structure.  The new structure is
  45  * returned with a reference count of one and needs to be
  46  * freed using free_extent_map()
  47  */
  48 struct extent_map *alloc_extent_map(void)
  49 {
  50         struct extent_map *em;
  51         em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
  52         if (!em)
  53                 return NULL;
  54         RB_CLEAR_NODE(&em->rb_node);
  55         em->flags = 0;
  56         em->compress_type = BTRFS_COMPRESS_NONE;
  57         em->generation = 0;
  58         atomic_set(&em->refs, 1);
  59         INIT_LIST_HEAD(&em->list);
  60         return em;
  61 }
  62
  63 /**
  64  * free_extent_map - drop reference count of an extent_map
  65  * @em:         extent map beeing releasead
  66  *
  67  * Drops the reference out on @em by one and free the structure
  68  * if the reference count hits zero.
  69  */
  70 void free_extent_map(struct extent_map *em)
  71 {
  72         if (!em)
  73                 return;
  74         WARN_ON(atomic_read(&em->refs) == 0);
  75         if (atomic_dec_and_test(&em->refs)) {
  76                 WARN_ON(extent_map_in_tree(em));
  77                 WARN_ON(!list_empty(&em->list));
  78                 if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
  79                         kfree(em->map_lookup);
  80                 kmem_cache_free(extent_map_cache, em);
  81         }
  82 }
  83
  84 /* simple helper to do math around the end of an extent, handling wrap */
  85 static u64 range_end(u64 start, u64 len)
  86 {
  87         if (start + len < start)
  88                 return (u64)-1;
  89         return start + len;
  90 }
  91
  92 static int tree_insert(struct rb_root *root, struct extent_map *em)
  93 {
  94         struct rb_node **p = &root->rb_node;
  95         struct rb_node *parent = NULL;
  96         struct extent_map *entry = NULL;
  97         struct rb_node *orig_parent = NULL;
  98         u64 end = range_end(em->start, em->len);
  99
 100         while (*p) {
 101                 parent = *p;
 102                 entry = rb_entry(parent, struct extent_map, rb_node);
 103
 104                 if (em->start < entry->start)
 105                         p = &(*p)->rb_left;
 106                 else if (em->start >= extent_map_end(entry))
 107                         p = &(*p)->rb_right;
 108                 else
 109                         return -EEXIST;
 110         }
 111
 112         orig_parent = parent;
 113         while (parent && em->start >= extent_map_end(entry)) {
 114                 parent = rb_next(parent);
 115                 entry = rb_entry(parent, struct extent_map, rb_node);
 116         }
 117         if (parent)
 118                 if (end > entry->start && em->start < extent_map_end(entry))
 119                         return -EEXIST;
 120
 121         parent = orig_parent;
 122         entry = rb_entry(parent, struct extent_map, rb_node);
 123         while (parent && em->start < entry->start) {
 124                 parent = rb_prev(parent);
 125                 entry = rb_entry(parent, struct extent_map, rb_node);
 126         }
 127         if (parent)
 128                 if (end > entry->start && em->start < extent_map_end(entry))
 129                         return -EEXIST;
 130
 131         rb_link_node(&em->rb_node, orig_parent, p);
 132         rb_insert_color(&em->rb_node, root);
 133         return 0;
 134 }
 135
 136 /*
 137  * search through the tree for an extent_map with a given offset.  If
 138  * it can't be found, try to find some neighboring extents
 139  */
 140 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 141                                      struct rb_node **prev_ret,
 142                                      struct rb_node **next_ret)
 143 {
 144         struct rb_node *n = root->rb_node;
 145         struct rb_node *prev = NULL;
 146         struct rb_node *orig_prev = NULL;
 147         struct extent_map *entry;
 148         struct extent_map *prev_entry = NULL;
 149
 150         while (n) {
 151                 entry = rb_entry(n, struct extent_map, rb_node);
 152                 prev = n;
 153                 prev_entry = entry;
 154
 155                 if (offset < entry->start)
 156                         n = n->rb_left;
 157                 else if (offset >= extent_map_end(entry))
 158                         n = n->rb_right;
 159                 else
 160                         return n;
 161         }
 162
 163         if (prev_ret) {
 164                 orig_prev = prev;
 165                 while (prev && offset >= extent_map_end(prev_entry)) {
 166                         prev = rb_next(prev);
 167                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 168                 }
 169                 *prev_ret = prev;
 170                 prev = orig_prev;
 171         }
 172
 173         if (next_ret) {
 174                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 175                 while (prev && offset < prev_entry->start) {
 176                         prev = rb_prev(prev);
 177                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 178                 }
 179                 *next_ret = prev;
 180         }
 181         return NULL;
 182 }
 183
 184 /* check to see if two extent_map structs are adjacent and safe to merge */
 185 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 186 {
 187         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 188                 return 0;
 189
 190         /*
 191          * don't merge compressed extents, we need to know their
 192          * actual size
 193          */
 194         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 195                 return 0;
 196
 197         if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
 198             test_bit(EXTENT_FLAG_LOGGING, &next->flags))
 199                 return 0;
 200
 201         /*
 202          * We don't want to merge stuff that hasn't been written to the log yet
 203          * since it may not reflect exactly what is on disk, and that would be
 204          * bad.
 205          */
 206         if (!list_empty(&prev->list) || !list_empty(&next->list))
 207                 return 0;
 208
 209         if (extent_map_end(prev) == next->start &&
 210             prev->flags == next->flags &&
 211             prev->bdev == next->bdev &&
 212             ((next->block_start == EXTENT_MAP_HOLE &&
 213               prev->block_start == EXTENT_MAP_HOLE) ||
 214              (next->block_start == EXTENT_MAP_INLINE &&
 215               prev->block_start == EXTENT_MAP_INLINE) ||
 216              (next->block_start == EXTENT_MAP_DELALLOC &&
 217               prev->block_start == EXTENT_MAP_DELALLOC) ||
 218              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 219               next->block_start == extent_map_block_end(prev)))) {
 220                 return 1;
 221         }
 222         return 0;
 223 }
 224
 225 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
 226 {
 227         struct extent_map *merge = NULL;
 228         struct rb_node *rb;
 229
 230         if (em->start != 0) {
 231                 rb = rb_prev(&em->rb_node);
 232                 if (rb)
 233                         merge = rb_entry(rb, struct extent_map, rb_node);
 234                 if (rb && mergable_maps(merge, em)) {
 235                         em->start = merge->start;
 236                         em->orig_start = merge->orig_start;
 237                         em->len += merge->len;
 238                         em->block_len += merge->block_len;
 239                         em->block_start = merge->block_start;
 240                         em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
 241                         em->mod_start = merge->mod_start;
 242                         em->generation = max(em->generation, merge->generation);
 243
 244                         rb_erase(&merge->rb_node, &tree->map);
 245                         RB_CLEAR_NODE(&merge->rb_node);
 246                         free_extent_map(merge);
 247                 }
 248         }
 249
 250         rb = rb_next(&em->rb_node);
 251         if (rb)
 252                 merge = rb_entry(rb, struct extent_map, rb_node);
 253         if (rb && mergable_maps(em, merge)) {
 254                 em->len += merge->len;
 255                 em->block_len += merge->block_len;
 256                 rb_erase(&merge->rb_node, &tree->map);
 257                 RB_CLEAR_NODE(&merge->rb_node);
 258                 em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
 259                 em->generation = max(em->generation, merge->generation);
 260                 free_extent_map(merge);
 261         }
 262 }
 263
 264 /**
 265  * unpin_extent_cache - unpin an extent from the cache
 266  * @tree:       tree to unpin the extent in
 267  * @start:      logical offset in the file
 268  * @len:        length of the extent
 269  * @gen:        generation that this extent has been modified in
 270  *
 271  * Called after an extent has been written to disk properly.  Set the generation
 272  * to the generation that actually added the file item to the inode so we know
 273  * we need to sync this extent when we call fsync().
 274  */
 275 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
 276                        u64 gen)
 277 {
 278         int ret = 0;
 279         struct extent_map *em;
 280         bool prealloc = false;
 281
 282         write_lock(&tree->lock);
 283         em = lookup_extent_mapping(tree, start, len);
 284
 285         WARN_ON(!em || em->start != start);
 286
 287         if (!em)
 288                 goto out;
 289
 290         em->generation = gen;
 291         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 292         em->mod_start = em->start;
 293         em->mod_len = em->len;
 294
 295         if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
 296                 prealloc = true;
 297                 clear_bit(EXTENT_FLAG_FILLING, &em->flags);
 298         }
 299
 300         try_merge_map(tree, em);
 301
 302         if (prealloc) {
 303                 em->mod_start = em->start;
 304                 em->mod_len = em->len;
 305         }
 306
 307         free_extent_map(em);
 308 out:
 309         write_unlock(&tree->lock);
 310         return ret;
 311
 312 }
 313
 314 void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
 315 {
 316         clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
 317         if (extent_map_in_tree(em))
 318                 try_merge_map(tree, em);
 319 }
 320
 321 static inline void setup_extent_mapping(struct extent_map_tree *tree,
 322                                         struct extent_map *em,
 323                                         int modified)
 324 {
 325         atomic_inc(&em->refs);
 326         em->mod_start = em->start;
 327         em->mod_len = em->len;
 328
 329         if (modified)
 330                 list_move(&em->list, &tree->modified_extents);
 331         else
 332                 try_merge_map(tree, em);
 333 }
 334
 335 /**
 336  * add_extent_mapping - add new extent map to the extent tree
 337  * @tree:       tree to insert new map in
 338  * @em:         map to insert
 339  *
 340  * Insert @em into @tree or perform a simple forward/backward merge with
 341  * existing mappings.  The extent_map struct passed in will be inserted
 342  * into the tree directly, with an additional reference taken, or a
 343  * reference dropped if the merge attempt was successful.
 344  */
 345 int add_extent_mapping(struct extent_map_tree *tree,
 346                        struct extent_map *em, int modified)
 347 {
 348         int ret = 0;
 349
 350         ret = tree_insert(&tree->map, em);
 351         if (ret)
 352                 goto out;
 353
 354         setup_extent_mapping(tree, em, modified);
 355 out:
 356         return ret;
 357 }
 358
 359 static struct extent_map *
 360 __lookup_extent_mapping(struct extent_map_tree *tree,
 361                         u64 start, u64 len, int strict)
 362 {
 363         struct extent_map *em;
 364         struct rb_node *rb_node;
 365         struct rb_node *prev = NULL;
 366         struct rb_node *next = NULL;
 367         u64 end = range_end(start, len);
 368
 369         rb_node = __tree_search(&tree->map, start, &prev, &next);
 370         if (!rb_node) {
 371                 if (prev)
 372                         rb_node = prev;
 373                 else if (next)
 374                         rb_node = next;
 375                 else
 376                         return NULL;
 377         }
 378
 379         em = rb_entry(rb_node, struct extent_map, rb_node);
 380
 381         if (strict && !(end > em->start && start < extent_map_end(em)))
 382                 return NULL;
 383
 384         atomic_inc(&em->refs);
 385         return em;
 386 }
 387
 388 /**
 389  * lookup_extent_mapping - lookup extent_map
 390  * @tree:       tree to lookup in
 391  * @start:      byte offset to start the search
 392  * @len:        length of the lookup range
 393  *
 394  * Find and return the first extent_map struct in @tree that intersects the
 395  * [start, len] range.  There may be additional objects in the tree that
 396  * intersect, so check the object returned carefully to make sure that no
 397  * additional lookups are needed.
 398  */
 399 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 400                                          u64 start, u64 len)
 401 {
 402         return __lookup_extent_mapping(tree, start, len, 1);
 403 }
 404
 405 /**
 406  * search_extent_mapping - find a nearby extent map
 407  * @tree:       tree to lookup in
 408  * @start:      byte offset to start the search
 409  * @len:        length of the lookup range
 410  *
 411  * Find and return the first extent_map struct in @tree that intersects the
 412  * [start, len] range.
 413  *
 414  * If one can't be found, any nearby extent may be returned
 415  */
 416 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
 417                                          u64 start, u64 len)
 418 {
 419         return __lookup_extent_mapping(tree, start, len, 0);
 420 }
 421
 422 /**
 423  * remove_extent_mapping - removes an extent_map from the extent tree
 424  * @tree:       extent tree to remove from
 425  * @em:         extent map beeing removed
 426  *
 427  * Removes @em from @tree.  No reference counts are dropped, and no checks
 428  * are done to see if the range is in use
 429  */
 430 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 431 {
 432         int ret = 0;
 433
 434         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 435         rb_erase(&em->rb_node, &tree->map);
 436         if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
 437                 list_del_init(&em->list);
 438         RB_CLEAR_NODE(&em->rb_node);
 439         return ret;
 440 }
 441
 442 void replace_extent_mapping(struct extent_map_tree *tree,
 443                             struct extent_map *cur,
 444                             struct extent_map *new,
 445                             int modified)
 446 {
 447         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
 448         ASSERT(extent_map_in_tree(cur));
 449         if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
 450                 list_del_init(&cur->list);
 451         rb_replace_node(&cur->rb_node, &new->rb_node, &tree->map);
 452         RB_CLEAR_NODE(&cur->rb_node);
 453
 454         setup_extent_mapping(tree, new, modified);
 455 }