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 } 414