fs/btrfs/extent_map.c

   1 #include <linux/err.h>
   2 #include <linux/gfp.h>
   3 #include <linux/slab.h>
   4 #include <linux/module.h>
   5 #include <linux/spinlock.h>
   6 #include <linux/hardirq.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  * @mask:               flags for memory allocations during tree operations
  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, gfp_t mask)
  37 {
  38         tree->map.rb_node = NULL;
  39         rwlock_init(&tree->lock);
  40 }
  41
  42 /**
  43  * alloc_extent_map - allocate new extent map structure
  44  * @mask:       memory allocation flags
  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(gfp_t mask)
  51 {
  52         struct extent_map *em;
  53         em = kmem_cache_alloc(extent_map_cache, mask);
  54         if (!em || IS_ERR(em))
  55                 return em;
  56         em->in_tree = 0;
  57         em->flags = 0;
  58         atomic_set(&em->refs, 1);
  59         return em;
  60 }
  61
  62 /**
  63  * free_extent_map - drop reference count of an extent_map
  64  * @em:         extent map beeing releasead
  65  *
  66  * Drops the reference out on @em by one and free the structure
  67  * if the reference count hits zero.
  68  */
  69 void free_extent_map(struct extent_map *em)
  70 {
  71         if (!em)
  72                 return;
  73         WARN_ON(atomic_read(&em->refs) == 0);
  74         if (atomic_dec_and_test(&em->refs)) {
  75                 WARN_ON(em->in_tree);
  76                 kmem_cache_free(extent_map_cache, em);
  77         }
  78 }
  79
  80 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  81                                    struct rb_node *node)
  82 {
  83         struct rb_node **p = &root->rb_node;
  84         struct rb_node *parent = NULL;
  85         struct extent_map *entry;
  86
  87         while (*p) {
  88                 parent = *p;
  89                 entry = rb_entry(parent, struct extent_map, rb_node);
  90
  91                 WARN_ON(!entry->in_tree);
  92
  93                 if (offset < entry->start)
  94                         p = &(*p)->rb_left;
  95                 else if (offset >= extent_map_end(entry))
  96                         p = &(*p)->rb_right;
  97                 else
  98                         return parent;
  99         }
 100
 101         entry = rb_entry(node, struct extent_map, rb_node);
 102         entry->in_tree = 1;
 103         rb_link_node(node, parent, p);
 104         rb_insert_color(node, root);
 105         return NULL;
 106 }
 107
 108 /*
 109  * search through the tree for an extent_map with a given offset.  If
 110  * it can't be found, try to find some neighboring extents
 111  */
 112 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 113                                      struct rb_node **prev_ret,
 114                                      struct rb_node **next_ret)
 115 {
 116         struct rb_node *n = root->rb_node;
 117         struct rb_node *prev = NULL;
 118         struct rb_node *orig_prev = NULL;
 119         struct extent_map *entry;
 120         struct extent_map *prev_entry = NULL;
 121
 122         while (n) {
 123                 entry = rb_entry(n, struct extent_map, rb_node);
 124                 prev = n;
 125                 prev_entry = entry;
 126
 127                 WARN_ON(!entry->in_tree);
 128
 129                 if (offset < entry->start)
 130                         n = n->rb_left;
 131                 else if (offset >= extent_map_end(entry))
 132                         n = n->rb_right;
 133                 else
 134                         return n;
 135         }
 136
 137         if (prev_ret) {
 138                 orig_prev = prev;
 139                 while (prev && offset >= extent_map_end(prev_entry)) {
 140                         prev = rb_next(prev);
 141                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 142                 }
 143                 *prev_ret = prev;
 144                 prev = orig_prev;
 145         }
 146
 147         if (next_ret) {
 148                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 149                 while (prev && offset < prev_entry->start) {
 150                         prev = rb_prev(prev);
 151                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 152                 }
 153                 *next_ret = prev;
 154         }
 155         return NULL;
 156 }
 157
 158 /* check to see if two extent_map structs are adjacent and safe to merge */
 159 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 160 {
 161         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 162                 return 0;
 163
 164         /*
 165          * don't merge compressed extents, we need to know their
 166          * actual size
 167          */
 168         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 169                 return 0;
 170
 171         if (extent_map_end(prev) == next->start &&
 172             prev->flags == next->flags &&
 173             prev->bdev == next->bdev &&
 174             ((next->block_start == EXTENT_MAP_HOLE &&
 175               prev->block_start == EXTENT_MAP_HOLE) ||
 176              (next->block_start == EXTENT_MAP_INLINE &&
 177               prev->block_start == EXTENT_MAP_INLINE) ||
 178              (next->block_start == EXTENT_MAP_DELALLOC &&
 179               prev->block_start == EXTENT_MAP_DELALLOC) ||
 180              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 181               next->block_start == extent_map_block_end(prev)))) {
 182                 return 1;
 183         }
 184         return 0;
 185 }
 186
 187 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
 188 {
 189         int ret = 0;
 190         struct extent_map *merge = NULL;
 191         struct rb_node *rb;
 192         struct extent_map *em;
 193
 194         write_lock(&tree->lock);
 195         em = lookup_extent_mapping(tree, start, len);
 196
 197         WARN_ON(!em || em->start != start);
 198
 199         if (!em)
 200                 goto out;
 201
 202         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 203
 204         if (em->start != 0) {
 205                 rb = rb_prev(&em->rb_node);
 206                 if (rb)
 207                         merge = rb_entry(rb, struct extent_map, rb_node);
 208                 if (rb && mergable_maps(merge, em)) {
 209                         em->start = merge->start;
 210                         em->len += merge->len;
 211                         em->block_len += merge->block_len;
 212                         em->block_start = merge->block_start;
 213                         merge->in_tree = 0;
 214                         rb_erase(&merge->rb_node, &tree->map);
 215                         free_extent_map(merge);
 216                 }
 217         }
 218
 219         rb = rb_next(&em->rb_node);
 220         if (rb)
 221                 merge = rb_entry(rb, struct extent_map, rb_node);
 222         if (rb && mergable_maps(em, merge)) {
 223                 em->len += merge->len;
 224                 em->block_len += merge->len;
 225                 rb_erase(&merge->rb_node, &tree->map);
 226                 merge->in_tree = 0;
 227                 free_extent_map(merge);
 228         }
 229
 230         free_extent_map(em);
 231 out:
 232         write_unlock(&tree->lock);
 233         return ret;
 234
 235 }
 236
 237 /**
 238  * add_extent_mapping - add new extent map to the extent tree
 239  * @tree:       tree to insert new map in
 240  * @em:         map to insert
 241  *
 242  * Insert @em into @tree or perform a simple forward/backward merge with
 243  * existing mappings.  The extent_map struct passed in will be inserted
 244  * into the tree directly, with an additional reference taken, or a
 245  * reference dropped if the merge attempt was successfull.
 246  */
 247 int add_extent_mapping(struct extent_map_tree *tree,
 248                        struct extent_map *em)
 249 {
 250         int ret = 0;
 251         struct extent_map *merge = NULL;
 252         struct rb_node *rb;
 253         struct extent_map *exist;
 254
 255         exist = lookup_extent_mapping(tree, em->start, em->len);
 256         if (exist) {
 257                 free_extent_map(exist);
 258                 ret = -EEXIST;
 259                 goto out;
 260         }
 261         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 262         if (rb) {
 263                 ret = -EEXIST;
 264                 goto out;
 265         }
 266         atomic_inc(&em->refs);
 267         if (em->start != 0) {
 268                 rb = rb_prev(&em->rb_node);
 269                 if (rb)
 270                         merge = rb_entry(rb, struct extent_map, rb_node);
 271                 if (rb && mergable_maps(merge, em)) {
 272                         em->start = merge->start;
 273                         em->len += merge->len;
 274                         em->block_len += merge->block_len;
 275                         em->block_start = merge->block_start;
 276                         merge->in_tree = 0;
 277                         rb_erase(&merge->rb_node, &tree->map);
 278                         free_extent_map(merge);
 279                 }
 280          }
 281         rb = rb_next(&em->rb_node);
 282         if (rb)
 283                 merge = rb_entry(rb, struct extent_map, rb_node);
 284         if (rb && mergable_maps(em, merge)) {
 285                 em->len += merge->len;
 286                 em->block_len += merge->len;
 287                 rb_erase(&merge->rb_node, &tree->map);
 288                 merge->in_tree = 0;
 289                 free_extent_map(merge);
 290         }
 291 out:
 292         return ret;
 293 }
 294
 295 /* simple helper to do math around the end of an extent, handling wrap */
 296 static u64 range_end(u64 start, u64 len)
 297 {
 298         if (start + len < start)
 299                 return (u64)-1;
 300         return start + len;
 301 }
 302
 303 /**
 304  * lookup_extent_mapping - lookup extent_map
 305  * @tree:       tree to lookup in
 306  * @start:      byte offset to start the search
 307  * @len:        length of the lookup range
 308  *
 309  * Find and return the first extent_map struct in @tree that intersects the
 310  * [start, len] range.  There may be additional objects in the tree that
 311  * intersect, so check the object returned carefully to make sure that no
 312  * additional lookups are needed.
 313  */
 314 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 315                                          u64 start, u64 len)
 316 {
 317         struct extent_map *em;
 318         struct rb_node *rb_node;
 319         struct rb_node *prev = NULL;
 320         struct rb_node *next = NULL;
 321         u64 end = range_end(start, len);
 322
 323         rb_node = __tree_search(&tree->map, start, &prev, &next);
 324         if (!rb_node && prev) {
 325                 em = rb_entry(prev, struct extent_map, rb_node);
 326                 if (end > em->start && start < extent_map_end(em))
 327                         goto found;
 328         }
 329         if (!rb_node && next) {
 330                 em = rb_entry(next, struct extent_map, rb_node);
 331                 if (end > em->start && start < extent_map_end(em))
 332                         goto found;
 333         }
 334         if (!rb_node) {
 335                 em = NULL;
 336                 goto out;
 337         }
 338         if (IS_ERR(rb_node)) {
 339                 em = ERR_PTR(PTR_ERR(rb_node));
 340                 goto out;
 341         }
 342         em = rb_entry(rb_node, struct extent_map, rb_node);
 343         if (end > em->start && start < extent_map_end(em))
 344                 goto found;
 345
 346         em = NULL;
 347         goto out;
 348
 349 found:
 350         atomic_inc(&em->refs);
 351 out:
 352         return em;
 353 }
 354
 355 /**
 356  * search_extent_mapping - find a nearby extent map
 357  * @tree:       tree to lookup in
 358  * @start:      byte offset to start the search
 359  * @len:        length of the lookup range
 360  *
 361  * Find and return the first extent_map struct in @tree that intersects the
 362  * [start, len] range.
 363  *
 364  * If one can't be found, any nearby extent may be returned
 365  */
 366 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
 367                                          u64 start, u64 len)
 368 {
 369         struct extent_map *em;
 370         struct rb_node *rb_node;
 371         struct rb_node *prev = NULL;
 372         struct rb_node *next = NULL;
 373
 374         rb_node = __tree_search(&tree->map, start, &prev, &next);
 375         if (!rb_node && prev) {
 376                 em = rb_entry(prev, struct extent_map, rb_node);
 377                 goto found;
 378         }
 379         if (!rb_node && next) {
 380                 em = rb_entry(next, struct extent_map, rb_node);
 381                 goto found;
 382         }
 383         if (!rb_node) {
 384                 em = NULL;
 385                 goto out;
 386         }
 387         if (IS_ERR(rb_node)) {
 388                 em = ERR_PTR(PTR_ERR(rb_node));
 389                 goto out;
 390         }
 391         em = rb_entry(rb_node, struct extent_map, rb_node);
 392         goto found;
 393
 394         em = NULL;
 395         goto out;
 396
 397 found:
 398         atomic_inc(&em->refs);
 399 out:
 400         return em;
 401 }
 402
 403 /**
 404  * remove_extent_mapping - removes an extent_map from the extent tree
 405  * @tree:       extent tree to remove from
 406  * @em:         extent map beeing removed
 407  *
 408  * Removes @em from @tree.  No reference counts are dropped, and no checks
 409  * are done to see if the range is in use
 410  */
 411 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 412 {
 413         int ret = 0;
 414
 415         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 416         rb_erase(&em->rb_node, &tree->map);
 417         em->in_tree = 0;
 418         return ret;
 419 }