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 if (extent_map_cache) 24 kmem_cache_destroy(extent_map_cache); 25 } 26 27 /** 28 * extent_map_tree_init - initialize extent map tree 29 * @tree: tree to initialize 30 * 31 * Initialize the extent tree @tree. Should be called for each new inode 32 * or other user of the extent_map interface. 33 */ 34 void extent_map_tree_init(struct extent_map_tree *tree) 35 { 36 tree->map = RB_ROOT; 37 INIT_LIST_HEAD(&tree->modified_extents); 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_zalloc(extent_map_cache, GFP_NOFS); 52 if (!em) 53 return NULL; 54 RB_CLEAR_NODE(&em->rb_node); 55 em->flags = 0; 56 em->compress_type = BTRFS_COMPRESS_NONE; 57 em->generation = 0; 58 atomic_set(&em->refs, 1); 59 INIT_LIST_HEAD(&em->list); 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(extent_map_in_tree(em)); 77 WARN_ON(!list_empty(&em->list)); 78 kmem_cache_free(extent_map_cache, em); 79 } 80 } 81 82 /* simple helper to do math around the end of an extent, handling wrap */ 83 static u64 range_end(u64 start, u64 len) 84 { 85 if (start + len < start) 86 return (u64)-1; 87 return start + len; 88 } 89 90 static int tree_insert(struct rb_root *root, struct extent_map *em) 91 { 92 struct rb_node **p = &root->rb_node; 93 struct rb_node *parent = NULL; 94 struct extent_map *entry = NULL; 95 struct rb_node *orig_parent = NULL; 96 u64 end = range_end(em->start, em->len); 97 98 while (*p) { 99 parent = *p; 100 entry = rb_entry(parent, struct extent_map, rb_node); 101 102 if (em->start < entry->start) 103 p = &(*p)->rb_left; 104 else if (em->start >= extent_map_end(entry)) 105 p = &(*p)->rb_right; 106 else 107 return -EEXIST; 108 } 109 110 orig_parent = parent; 111 while (parent && em->start >= extent_map_end(entry)) { 112 parent = rb_next(parent); 113 entry = rb_entry(parent, struct extent_map, rb_node); 114 } 115 if (parent) 116 if (end > entry->start && em->start < extent_map_end(entry)) 117 return -EEXIST; 118 119 parent = orig_parent; 120 entry = rb_entry(parent, struct extent_map, rb_node); 121 while (parent && em->start < entry->start) { 122 parent = rb_prev(parent); 123 entry = rb_entry(parent, struct extent_map, rb_node); 124 } 125 if (parent) 126 if (end > entry->start && em->start < extent_map_end(entry)) 127 return -EEXIST; 128 129 rb_link_node(&em->rb_node, orig_parent, p); 130 rb_insert_color(&em->rb_node, root); 131 return 0; 132 } 133 134 /* 135 * search through the tree for an extent_map with a given offset. If 136 * it can't be found, try to find some neighboring extents 137 */ 138 static struct rb_node *__tree_search(struct rb_root *root, u64 offset, 139 struct rb_node **prev_ret, 140 struct rb_node **next_ret) 141 { 142 struct rb_node *n = root->rb_node; 143 struct rb_node *prev = NULL; 144 struct rb_node *orig_prev = NULL; 145 struct extent_map *entry; 146 struct extent_map *prev_entry = NULL; 147 148 while (n) { 149 entry = rb_entry(n, struct extent_map, rb_node); 150 prev = n; 151 prev_entry = entry; 152 153 if (offset < entry->start) 154 n = n->rb_left; 155 else if (offset >= extent_map_end(entry)) 156 n = n->rb_right; 157 else 158 return n; 159 } 160 161 if (prev_ret) { 162 orig_prev = prev; 163 while (prev && offset >= extent_map_end(prev_entry)) { 164 prev = rb_next(prev); 165 prev_entry = rb_entry(prev, struct extent_map, rb_node); 166 } 167 *prev_ret = prev; 168 prev = orig_prev; 169 } 170 171 if (next_ret) { 172 prev_entry = rb_entry(prev, struct extent_map, rb_node); 173 while (prev && offset < prev_entry->start) { 174 prev = rb_prev(prev); 175 prev_entry = rb_entry(prev, struct extent_map, rb_node); 176 } 177 *next_ret = prev; 178 } 179 return NULL; 180 } 181 182 /* check to see if two extent_map structs are adjacent and safe to merge */ 183 static int mergable_maps(struct extent_map *prev, struct extent_map *next) 184 { 185 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags)) 186 return 0; 187 188 /* 189 * don't merge compressed extents, we need to know their 190 * actual size 191 */ 192 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags)) 193 return 0; 194 195 if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) || 196 test_bit(EXTENT_FLAG_LOGGING, &next->flags)) 197 return 0; 198 199 /* 200 * We don't want to merge stuff that hasn't been written to the log yet 201 * since it may not reflect exactly what is on disk, and that would be 202 * bad. 203 */ 204 if (!list_empty(&prev->list) || !list_empty(&next->list)) 205 return 0; 206 207 if (extent_map_end(prev) == next->start && 208 prev->flags == next->flags && 209 prev->bdev == next->bdev && 210 ((next->block_start == EXTENT_MAP_HOLE && 211 prev->block_start == EXTENT_MAP_HOLE) || 212 (next->block_start == EXTENT_MAP_INLINE && 213 prev->block_start == EXTENT_MAP_INLINE) || 214 (next->block_start == EXTENT_MAP_DELALLOC && 215 prev->block_start == EXTENT_MAP_DELALLOC) || 216 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 && 217 next->block_start == extent_map_block_end(prev)))) { 218 return 1; 219 } 220 return 0; 221 } 222 223 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em) 224 { 225 struct extent_map *merge = NULL; 226 struct rb_node *rb; 227 228 if (em->start != 0) { 229 rb = rb_prev(&em->rb_node); 230 if (rb) 231 merge = rb_entry(rb, struct extent_map, rb_node); 232 if (rb && mergable_maps(merge, em)) { 233 em->start = merge->start; 234 em->orig_start = merge->orig_start; 235 em->len += merge->len; 236 em->block_len += merge->block_len; 237 em->block_start = merge->block_start; 238 em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start; 239 em->mod_start = merge->mod_start; 240 em->generation = max(em->generation, merge->generation); 241 242 rb_erase(&merge->rb_node, &tree->map); 243 RB_CLEAR_NODE(&merge->rb_node); 244 free_extent_map(merge); 245 } 246 } 247 248 rb = rb_next(&em->rb_node); 249 if (rb) 250 merge = rb_entry(rb, struct extent_map, rb_node); 251 if (rb && mergable_maps(em, merge)) { 252 em->len += merge->len; 253 em->block_len += merge->block_len; 254 rb_erase(&merge->rb_node, &tree->map); 255 RB_CLEAR_NODE(&merge->rb_node); 256 em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start; 257 em->generation = max(em->generation, merge->generation); 258 free_extent_map(merge); 259 } 260 } 261 262 /** 263 * unpin_extent_cache - unpin an extent from the cache 264 * @tree: tree to unpin the extent in 265 * @start: logical offset in the file 266 * @len: length of the extent 267 * @gen: generation that this extent has been modified in 268 * 269 * Called after an extent has been written to disk properly. Set the generation 270 * to the generation that actually added the file item to the inode so we know 271 * we need to sync this extent when we call fsync(). 272 */ 273 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, 274 u64 gen) 275 { 276 int ret = 0; 277 struct extent_map *em; 278 bool prealloc = false; 279 280 write_lock(&tree->lock); 281 em = lookup_extent_mapping(tree, start, len); 282 283 WARN_ON(!em || em->start != start); 284 285 if (!em) 286 goto out; 287 288 if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags)) 289 list_move(&em->list, &tree->modified_extents); 290 em->generation = gen; 291 clear_bit(EXTENT_FLAG_PINNED, &em->flags); 292 em->mod_start = em->start; 293 em->mod_len = em->len; 294 295 if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) { 296 prealloc = true; 297 clear_bit(EXTENT_FLAG_FILLING, &em->flags); 298 } 299 300 try_merge_map(tree, em); 301 302 if (prealloc) { 303 em->mod_start = em->start; 304 em->mod_len = em->len; 305 } 306 307 free_extent_map(em); 308 out: 309 write_unlock(&tree->lock); 310 return ret; 311 312 } 313 314 void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em) 315 { 316 clear_bit(EXTENT_FLAG_LOGGING, &em->flags); 317 if (extent_map_in_tree(em)) 318 try_merge_map(tree, em); 319 } 320 321 /** 322 * add_extent_mapping - add new extent map to the extent tree 323 * @tree: tree to insert new map in 324 * @em: map to insert 325 * 326 * Insert @em into @tree or perform a simple forward/backward merge with 327 * existing mappings. The extent_map struct passed in will be inserted 328 * into the tree directly, with an additional reference taken, or a 329 * reference dropped if the merge attempt was successful. 330 */ 331 int add_extent_mapping(struct extent_map_tree *tree, 332 struct extent_map *em, int modified) 333 { 334 int ret = 0; 335 336 ret = tree_insert(&tree->map, em); 337 if (ret) 338 goto out; 339 340 atomic_inc(&em->refs); 341 342 em->mod_start = em->start; 343 em->mod_len = em->len; 344 345 if (modified) 346 list_move(&em->list, &tree->modified_extents); 347 else 348 try_merge_map(tree, em); 349 out: 350 return ret; 351 } 352 353 static struct extent_map * 354 __lookup_extent_mapping(struct extent_map_tree *tree, 355 u64 start, u64 len, int strict) 356 { 357 struct extent_map *em; 358 struct rb_node *rb_node; 359 struct rb_node *prev = NULL; 360 struct rb_node *next = NULL; 361 u64 end = range_end(start, len); 362 363 rb_node = __tree_search(&tree->map, start, &prev, &next); 364 if (!rb_node) { 365 if (prev) 366 rb_node = prev; 367 else if (next) 368 rb_node = next; 369 else 370 return NULL; 371 } 372 373 em = rb_entry(rb_node, struct extent_map, rb_node); 374 375 if (strict && !(end > em->start && start < extent_map_end(em))) 376 return NULL; 377 378 atomic_inc(&em->refs); 379 return em; 380 } 381 382 /** 383 * lookup_extent_mapping - lookup extent_map 384 * @tree: tree to lookup in 385 * @start: byte offset to start the search 386 * @len: length of the lookup range 387 * 388 * Find and return the first extent_map struct in @tree that intersects the 389 * [start, len] range. There may be additional objects in the tree that 390 * intersect, so check the object returned carefully to make sure that no 391 * additional lookups are needed. 392 */ 393 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree, 394 u64 start, u64 len) 395 { 396 return __lookup_extent_mapping(tree, start, len, 1); 397 } 398 399 /** 400 * search_extent_mapping - find a nearby extent map 401 * @tree: tree to lookup in 402 * @start: byte offset to start the search 403 * @len: length of the lookup range 404 * 405 * Find and return the first extent_map struct in @tree that intersects the 406 * [start, len] range. 407 * 408 * If one can't be found, any nearby extent may be returned 409 */ 410 struct extent_map *search_extent_mapping(struct extent_map_tree *tree, 411 u64 start, u64 len) 412 { 413 return __lookup_extent_mapping(tree, start, len, 0); 414 } 415 416 /** 417 * remove_extent_mapping - removes an extent_map from the extent tree 418 * @tree: extent tree to remove from 419 * @em: extent map beeing removed 420 * 421 * Removes @em from @tree. No reference counts are dropped, and no checks 422 * are done to see if the range is in use 423 */ 424 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 425 { 426 int ret = 0; 427 428 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); 429 rb_erase(&em->rb_node, &tree->map); 430 if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags)) 431 list_del_init(&em->list); 432 RB_CLEAR_NODE(&em->rb_node); 433 return ret; 434 } 435