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  * @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_ROOT;
  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         em->compress_type = BTRFS_COMPRESS_NONE;
  59         atomic_set(&em->refs, 1);
  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(em->in_tree);
  77                 kmem_cache_free(extent_map_cache, em);
  78         }
  79 }
  80
  81 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  82                                    struct rb_node *node)
  83 {
  84         struct rb_node **p = &root->rb_node;
  85         struct rb_node *parent = NULL;
  86         struct extent_map *entry;
  87
  88         while (*p) {
  89                 parent = *p;
  90                 entry = rb_entry(parent, struct extent_map, rb_node);
  91
  92                 WARN_ON(!entry->in_tree);
  93
  94                 if (offset < entry->start)
  95                         p = &(*p)->rb_left;
  96                 else if (offset >= extent_map_end(entry))
  97                         p = &(*p)->rb_right;
  98                 else
  99                         return parent;
 100         }
 101
 102         entry = rb_entry(node, struct extent_map, rb_node);
 103         entry->in_tree = 1;
 104         rb_link_node(node, parent, p);
 105         rb_insert_color(node, root);
 106         return NULL;
 107 }
 108
 109 /*
 110  * search through the tree for an extent_map with a given offset.  If
 111  * it can't be found, try to find some neighboring extents
 112  */
 113 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 114                                      struct rb_node **prev_ret,
 115                                      struct rb_node **next_ret)
 116 {
 117         struct rb_node *n = root->rb_node;
 118         struct rb_node *prev = NULL;
 119         struct rb_node *orig_prev = NULL;
 120         struct extent_map *entry;
 121         struct extent_map *prev_entry = NULL;
 122
 123         while (n) {
 124                 entry = rb_entry(n, struct extent_map, rb_node);
 125                 prev = n;
 126                 prev_entry = entry;
 127
 128                 WARN_ON(!entry->in_tree);
 129
 130                 if (offset < entry->start)
 131                         n = n->rb_left;
 132                 else if (offset >= extent_map_end(entry))
 133                         n = n->rb_right;
 134                 else
 135                         return n;
 136         }
 137
 138         if (prev_ret) {
 139                 orig_prev = prev;
 140                 while (prev && offset >= extent_map_end(prev_entry)) {
 141                         prev = rb_next(prev);
 142                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 143                 }
 144                 *prev_ret = prev;
 145                 prev = orig_prev;
 146         }
 147
 148         if (next_ret) {
 149                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 150                 while (prev && offset < prev_entry->start) {
 151                         prev = rb_prev(prev);
 152                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 153                 }
 154                 *next_ret = prev;
 155         }
 156         return NULL;
 157 }
 158
 159 /* check to see if two extent_map structs are adjacent and safe to merge */
 160 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 161 {
 162         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 163                 return 0;
 164
 165         /*
 166          * don't merge compressed extents, we need to know their
 167          * actual size
 168          */
 169         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 170                 return 0;
 171
 172         if (extent_map_end(prev) == next->start &&
 173             prev->flags == next->flags &&
 174             prev->bdev == next->bdev &&
 175             ((next->block_start == EXTENT_MAP_HOLE &&
 176               prev->block_start == EXTENT_MAP_HOLE) ||
 177              (next->block_start == EXTENT_MAP_INLINE &&
 178               prev->block_start == EXTENT_MAP_INLINE) ||
 179              (next->block_start == EXTENT_MAP_DELALLOC &&
 180               prev->block_start == EXTENT_MAP_DELALLOC) ||
 181              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 182               next->block_start == extent_map_block_end(prev)))) {
 183                 return 1;
 184         }
 185         return 0;
 186 }
 187
 188 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
 189 {
 190         int ret = 0;
 191         struct extent_map *merge = NULL;
 192         struct rb_node *rb;
 193         struct extent_map *em;
 194
 195         write_lock(&tree->lock);
 196         em = lookup_extent_mapping(tree, start, len);
 197
 198         WARN_ON(!em || em->start != start);
 199
 200         if (!em)
 201                 goto out;
 202
 203         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 204
 205         if (em->start != 0) {
 206                 rb = rb_prev(&em->rb_node);
 207                 if (rb)
 208                         merge = rb_entry(rb, struct extent_map, rb_node);
 209                 if (rb && mergable_maps(merge, em)) {
 210                         em->start = merge->start;
 211                         em->len += merge->len;
 212                         em->block_len += merge->block_len;
 213                         em->block_start = merge->block_start;
 214                         merge->in_tree = 0;
 215                         rb_erase(&merge->rb_node, &tree->map);
 216                         free_extent_map(merge);
 217                 }
 218         }
 219
 220         rb = rb_next(&em->rb_node);
 221         if (rb)
 222                 merge = rb_entry(rb, struct extent_map, rb_node);
 223         if (rb && mergable_maps(em, merge)) {
 224                 em->len += merge->len;
 225                 em->block_len += merge->len;
 226                 rb_erase(&merge->rb_node, &tree->map);
 227                 merge->in_tree = 0;
 228                 free_extent_map(merge);
 229         }
 230
 231         free_extent_map(em);
 232 out:
 233         write_unlock(&tree->lock);
 234         return ret;
 235
 236 }
 237
 238 /**
 239  * add_extent_mapping - add new extent map to the extent tree
 240  * @tree:       tree to insert new map in
 241  * @em:         map to insert
 242  *
 243  * Insert @em into @tree or perform a simple forward/backward merge with
 244  * existing mappings.  The extent_map struct passed in will be inserted
 245  * into the tree directly, with an additional reference taken, or a
 246  * reference dropped if the merge attempt was successfull.
 247  */
 248 int add_extent_mapping(struct extent_map_tree *tree,
 249                        struct extent_map *em)
 250 {
 251         int ret = 0;
 252         struct extent_map *merge = NULL;
 253         struct rb_node *rb;
 254         struct extent_map *exist;
 255
 256         exist = lookup_extent_mapping(tree, em->start, em->len);
 257         if (exist) {
 258                 free_extent_map(exist);
 259                 ret = -EEXIST;
 260                 goto out;
 261         }
 262         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 263         if (rb) {
 264                 ret = -EEXIST;
 265                 goto out;
 266         }
 267         atomic_inc(&em->refs);
 268         if (em->start != 0) {
 269                 rb = rb_prev(&em->rb_node);
 270                 if (rb)
 271                         merge = rb_entry(rb, struct extent_map, rb_node);
 272                 if (rb && mergable_maps(merge, em)) {
 273                         em->start = merge->start;
 274                         em->len += merge->len;
 275                         em->block_len += merge->block_len;
 276                         em->block_start = merge->block_start;
 277                         merge->in_tree = 0;
 278                         rb_erase(&merge->rb_node, &tree->map);
 279                         free_extent_map(merge);
 280                 }
 281          }
 282         rb = rb_next(&em->rb_node);
 283         if (rb)
 284                 merge = rb_entry(rb, struct extent_map, rb_node);
 285         if (rb && mergable_maps(em, merge)) {
 286                 em->len += merge->len;
 287                 em->block_len += merge->len;
 288                 rb_erase(&merge->rb_node, &tree->map);
 289                 merge->in_tree = 0;
 290                 free_extent_map(merge);
 291         }
 292 out:
 293         return ret;
 294 }
 295
 296 /* simple helper to do math around the end of an extent, handling wrap */
 297 static u64 range_end(u64 start, u64 len)
 298 {
 299         if (start + len < start)
 300                 return (u64)-1;
 301         return start + len;
 302 }
 303
 304 /**
 305  * lookup_extent_mapping - lookup extent_map
 306  * @tree:       tree to lookup in
 307  * @start:      byte offset to start the search
 308  * @len:        length of the lookup range
 309  *
 310  * Find and return the first extent_map struct in @tree that intersects the
 311  * [start, len] range.  There may be additional objects in the tree that
 312  * intersect, so check the object returned carefully to make sure that no
 313  * additional lookups are needed.
 314  */
 315 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 316                                          u64 start, u64 len)
 317 {
 318         struct extent_map *em;
 319         struct rb_node *rb_node;
 320         struct rb_node *prev = NULL;
 321         struct rb_node *next = NULL;
 322         u64 end = range_end(start, len);
 323
 324         rb_node = __tree_search(&tree->map, start, &prev, &next);
 325         if (!rb_node && prev) {
 326                 em = rb_entry(prev, struct extent_map, rb_node);
 327                 if (end > em->start && start < extent_map_end(em))
 328                         goto found;
 329         }
 330         if (!rb_node && next) {
 331                 em = rb_entry(next, struct extent_map, rb_node);
 332                 if (end > em->start && start < extent_map_end(em))
 333                         goto found;
 334         }
 335         if (!rb_node) {
 336                 em = NULL;
 337                 goto out;
 338         }
 339         if (IS_ERR(rb_node)) {
 340                 em = ERR_CAST(rb_node);
 341                 goto out;
 342         }
 343         em = rb_entry(rb_node, struct extent_map, rb_node);
 344         if (end > em->start && start < extent_map_end(em))
 345                 goto found;
 346
 347         em = NULL;
 348         goto out;
 349
 350 found:
 351         atomic_inc(&em->refs);
 352 out:
 353         return em;
 354 }
 355
 356 /**
 357  * search_extent_mapping - find a nearby extent map
 358  * @tree:       tree to lookup in
 359  * @start:      byte offset to start the search
 360  * @len:        length of the lookup range
 361  *
 362  * Find and return the first extent_map struct in @tree that intersects the
 363  * [start, len] range.
 364  *
 365  * If one can't be found, any nearby extent may be returned
 366  */
 367 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
 368                                          u64 start, u64 len)
 369 {
 370         struct extent_map *em;
 371         struct rb_node *rb_node;
 372         struct rb_node *prev = NULL;
 373         struct rb_node *next = NULL;
 374
 375         rb_node = __tree_search(&tree->map, start, &prev, &next);
 376         if (!rb_node && prev) {
 377                 em = rb_entry(prev, struct extent_map, rb_node);
 378                 goto found;
 379         }
 380         if (!rb_node && next) {
 381                 em = rb_entry(next, struct extent_map, rb_node);
 382                 goto found;
 383         }
 384         if (!rb_node) {
 385                 em = NULL;
 386                 goto out;
 387         }
 388         if (IS_ERR(rb_node)) {
 389                 em = ERR_CAST(rb_node);
 390                 goto out;
 391         }
 392         em = rb_entry(rb_node, struct extent_map, rb_node);
 393         goto found;
 394
 395         em = NULL;
 396         goto out;
 397
 398 found:
 399         atomic_inc(&em->refs);
 400 out:
 401         return em;
 402 }
 403
 404 /**
 405  * remove_extent_mapping - removes an extent_map from the extent tree
 406  * @tree:       extent tree to remove from
 407  * @em:         extent map beeing removed
 408  *
 409  * Removes @em from @tree.  No reference counts are dropped, and no checks
 410  * are done to see if the range is in use
 411  */
 412 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 413 {
 414         int ret = 0;
 415
 416         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 417         rb_erase(&em->rb_node, &tree->map);
 418         em->in_tree = 0;
 419         return ret;
 420 }