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