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("btrfs_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         INIT_LIST_HEAD(&tree->modified_extents);
  39         rwlock_init(&tree->lock);
  40 }
  41
  42 /**
  43  * alloc_extent_map - allocate new extent map structure
  44  *
  45  * Allocate a new extent_map structure.  The new structure is
  46  * returned with a reference count of one and needs to be
  47  * freed using free_extent_map()
  48  */
  49 struct extent_map *alloc_extent_map(void)
  50 {
  51         struct extent_map *em;
  52         em = kmem_cache_alloc(extent_map_cache, GFP_NOFS);
  53         if (!em)
  54                 return NULL;
  55         em->in_tree = 0;
  56         em->flags = 0;
  57         em->compress_type = BTRFS_COMPRESS_NONE;
  58         em->generation = 0;
  59         atomic_set(&em->refs, 1);
  60         INIT_LIST_HEAD(&em->list);
  61         return em;
  62 }
  63
  64 /**
  65  * free_extent_map - drop reference count of an extent_map
  66  * @em:         extent map beeing releasead
  67  *
  68  * Drops the reference out on @em by one and free the structure
  69  * if the reference count hits zero.
  70  */
  71 void free_extent_map(struct extent_map *em)
  72 {
  73         if (!em)
  74                 return;
  75         WARN_ON(atomic_read(&em->refs) == 0);
  76         if (atomic_dec_and_test(&em->refs)) {
  77                 WARN_ON(em->in_tree);
  78                 WARN_ON(!list_empty(&em->list));
  79                 kmem_cache_free(extent_map_cache, em);
  80         }
  81 }
  82
  83 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  84                                    struct rb_node *node)
  85 {
  86         struct rb_node **p = &root->rb_node;
  87         struct rb_node *parent = NULL;
  88         struct extent_map *entry;
  89
  90         while (*p) {
  91                 parent = *p;
  92                 entry = rb_entry(parent, struct extent_map, rb_node);
  93
  94                 WARN_ON(!entry->in_tree);
  95
  96                 if (offset < entry->start)
  97                         p = &(*p)->rb_left;
  98                 else if (offset >= extent_map_end(entry))
  99                         p = &(*p)->rb_right;
 100                 else
 101                         return parent;
 102         }
 103
 104         entry = rb_entry(node, struct extent_map, rb_node);
 105         entry->in_tree = 1;
 106         rb_link_node(node, parent, p);
 107         rb_insert_color(node, root);
 108         return NULL;
 109 }
 110
 111 /*
 112  * search through the tree for an extent_map with a given offset.  If
 113  * it can't be found, try to find some neighboring extents
 114  */
 115 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 116                                      struct rb_node **prev_ret,
 117                                      struct rb_node **next_ret)
 118 {
 119         struct rb_node *n = root->rb_node;
 120         struct rb_node *prev = NULL;
 121         struct rb_node *orig_prev = NULL;
 122         struct extent_map *entry;
 123         struct extent_map *prev_entry = NULL;
 124
 125         while (n) {
 126                 entry = rb_entry(n, struct extent_map, rb_node);
 127                 prev = n;
 128                 prev_entry = entry;
 129
 130                 WARN_ON(!entry->in_tree);
 131
 132                 if (offset < entry->start)
 133                         n = n->rb_left;
 134                 else if (offset >= extent_map_end(entry))
 135                         n = n->rb_right;
 136                 else
 137                         return n;
 138         }
 139
 140         if (prev_ret) {
 141                 orig_prev = prev;
 142                 while (prev && offset >= extent_map_end(prev_entry)) {
 143                         prev = rb_next(prev);
 144                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 145                 }
 146                 *prev_ret = prev;
 147                 prev = orig_prev;
 148         }
 149
 150         if (next_ret) {
 151                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 152                 while (prev && offset < prev_entry->start) {
 153                         prev = rb_prev(prev);
 154                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 155                 }
 156                 *next_ret = prev;
 157         }
 158         return NULL;
 159 }
 160
 161 /* check to see if two extent_map structs are adjacent and safe to merge */
 162 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 163 {
 164         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 165                 return 0;
 166
 167         /*
 168          * don't merge compressed extents, we need to know their
 169          * actual size
 170          */
 171         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 172                 return 0;
 173
 174         if (extent_map_end(prev) == next->start &&
 175             prev->flags == next->flags &&
 176             prev->bdev == next->bdev &&
 177             ((next->block_start == EXTENT_MAP_HOLE &&
 178               prev->block_start == EXTENT_MAP_HOLE) ||
 179              (next->block_start == EXTENT_MAP_INLINE &&
 180               prev->block_start == EXTENT_MAP_INLINE) ||
 181              (next->block_start == EXTENT_MAP_DELALLOC &&
 182               prev->block_start == EXTENT_MAP_DELALLOC) ||
 183              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 184               next->block_start == extent_map_block_end(prev)))) {
 185                 return 1;
 186         }
 187         return 0;
 188 }
 189
 190 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
 191 {
 192         struct extent_map *merge = NULL;
 193         struct rb_node *rb;
 194
 195         if (em->start != 0) {
 196                 rb = rb_prev(&em->rb_node);
 197                 if (rb)
 198                         merge = rb_entry(rb, struct extent_map, rb_node);
 199                 if (rb && mergable_maps(merge, em)) {
 200                         em->start = merge->start;
 201                         em->len += merge->len;
 202                         em->block_len += merge->block_len;
 203                         em->block_start = merge->block_start;
 204                         merge->in_tree = 0;
 205                         if (merge->generation > em->generation) {
 206                                 em->mod_start = em->start;
 207                                 em->mod_len = em->len;
 208                                 em->generation = merge->generation;
 209                                 list_move(&em->list, &tree->modified_extents);
 210                         }
 211
 212                         list_del_init(&merge->list);
 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                 if (merge->generation > em->generation) {
 227                         em->mod_len = em->len;
 228                         em->generation = merge->generation;
 229                         list_move(&em->list, &tree->modified_extents);
 230                 }
 231                 list_del_init(&merge->list);
 232                 free_extent_map(merge);
 233         }
 234 }
 235
 236 /**
 237  * unpin_extent_cache - unpin an extent from the cache
 238  * @tree:       tree to unpin the extent in
 239  * @start:      logical offset in the file
 240  * @len:        length of the extent
 241  * @gen:        generation that this extent has been modified in
 242  *
 243  * Called after an extent has been written to disk properly.  Set the generation
 244  * to the generation that actually added the file item to the inode so we know
 245  * we need to sync this extent when we call fsync().
 246  */
 247 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
 248                        u64 gen)
 249 {
 250         int ret = 0;
 251         struct extent_map *em;
 252         bool prealloc = false;
 253
 254         write_lock(&tree->lock);
 255         em = lookup_extent_mapping(tree, start, len);
 256
 257         WARN_ON(!em || em->start != start);
 258
 259         if (!em)
 260                 goto out;
 261
 262         list_move(&em->list, &tree->modified_extents);
 263         em->generation = gen;
 264         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 265         em->mod_start = em->start;
 266         em->mod_len = em->len;
 267
 268         if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
 269                 prealloc = true;
 270                 clear_bit(EXTENT_FLAG_PREALLOC, &em->flags);
 271         }
 272
 273         try_merge_map(tree, em);
 274
 275         if (prealloc) {
 276                 em->mod_start = em->start;
 277                 em->mod_len = em->len;
 278         }
 279
 280         free_extent_map(em);
 281 out:
 282         write_unlock(&tree->lock);
 283         return ret;
 284
 285 }
 286
 287 /**
 288  * add_extent_mapping - add new extent map to the extent tree
 289  * @tree:       tree to insert new map in
 290  * @em:         map to insert
 291  *
 292  * Insert @em into @tree or perform a simple forward/backward merge with
 293  * existing mappings.  The extent_map struct passed in will be inserted
 294  * into the tree directly, with an additional reference taken, or a
 295  * reference dropped if the merge attempt was successful.
 296  */
 297 int add_extent_mapping(struct extent_map_tree *tree,
 298                        struct extent_map *em)
 299 {
 300         int ret = 0;
 301         struct rb_node *rb;
 302         struct extent_map *exist;
 303
 304         exist = lookup_extent_mapping(tree, em->start, em->len);
 305         if (exist) {
 306                 free_extent_map(exist);
 307                 ret = -EEXIST;
 308                 goto out;
 309         }
 310         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 311         if (rb) {
 312                 ret = -EEXIST;
 313                 goto out;
 314         }
 315         atomic_inc(&em->refs);
 316
 317         em->mod_start = em->start;
 318         em->mod_len = em->len;
 319
 320         try_merge_map(tree, em);
 321 out:
 322         return ret;
 323 }
 324
 325 /* simple helper to do math around the end of an extent, handling wrap */
 326 static u64 range_end(u64 start, u64 len)
 327 {
 328         if (start + len < start)
 329                 return (u64)-1;
 330         return start + len;
 331 }
 332
 333 struct extent_map *__lookup_extent_mapping(struct extent_map_tree *tree,
 334                                            u64 start, u64 len, int strict)
 335 {
 336         struct extent_map *em;
 337         struct rb_node *rb_node;
 338         struct rb_node *prev = NULL;
 339         struct rb_node *next = NULL;
 340         u64 end = range_end(start, len);
 341
 342         rb_node = __tree_search(&tree->map, start, &prev, &next);
 343         if (!rb_node) {
 344                 if (prev)
 345                         rb_node = prev;
 346                 else if (next)
 347                         rb_node = next;
 348                 else
 349                         return NULL;
 350         }
 351
 352         em = rb_entry(rb_node, struct extent_map, rb_node);
 353
 354         if (strict && !(end > em->start && start < extent_map_end(em)))
 355                 return NULL;
 356
 357         atomic_inc(&em->refs);
 358         return em;
 359 }
 360
 361 /**
 362  * lookup_extent_mapping - lookup extent_map
 363  * @tree:       tree to lookup in
 364  * @start:      byte offset to start the search
 365  * @len:        length of the lookup range
 366  *
 367  * Find and return the first extent_map struct in @tree that intersects the
 368  * [start, len] range.  There may be additional objects in the tree that
 369  * intersect, so check the object returned carefully to make sure that no
 370  * additional lookups are needed.
 371  */
 372 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 373                                          u64 start, u64 len)
 374 {
 375         return __lookup_extent_mapping(tree, start, len, 1);
 376 }
 377
 378 /**
 379  * search_extent_mapping - find a nearby extent map
 380  * @tree:       tree to lookup in
 381  * @start:      byte offset to start the search
 382  * @len:        length of the lookup range
 383  *
 384  * Find and return the first extent_map struct in @tree that intersects the
 385  * [start, len] range.
 386  *
 387  * If one can't be found, any nearby extent may be returned
 388  */
 389 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
 390                                          u64 start, u64 len)
 391 {
 392         return __lookup_extent_mapping(tree, start, len, 0);
 393 }
 394
 395 /**
 396  * remove_extent_mapping - removes an extent_map from the extent tree
 397  * @tree:       extent tree to remove from
 398  * @em:         extent map beeing removed
 399  *
 400  * Removes @em from @tree.  No reference counts are dropped, and no checks
 401  * are done to see if the range is in use
 402  */
 403 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 404 {
 405         int ret = 0;
 406
 407         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 408         rb_erase(&em->rb_node, &tree->map);
 409         if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
 410                 list_del_init(&em->list);
 411         em->in_tree = 0;
 412         return ret;
 413 }