fs/btrfs/extent_map.c

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