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_zalloc(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->orig_start = merge->orig_start; 202 em->len += merge->len; 203 em->block_len += merge->block_len; 204 em->block_start = merge->block_start; 205 merge->in_tree = 0; 206 em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start; 207 em->mod_start = merge->mod_start; 208 em->generation = max(em->generation, merge->generation); 209 list_move(&em->list, &tree->modified_extents); 210 211 list_del_init(&merge->list); 212 rb_erase(&merge->rb_node, &tree->map); 213 free_extent_map(merge); 214 } 215 } 216 217 rb = rb_next(&em->rb_node); 218 if (rb) 219 merge = rb_entry(rb, struct extent_map, rb_node); 220 if (rb && mergable_maps(em, merge)) { 221 em->len += merge->len; 222 em->block_len += merge->len; 223 rb_erase(&merge->rb_node, &tree->map); 224 merge->in_tree = 0; 225 em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start; 226 em->generation = max(em->generation, merge->generation); 227 list_del_init(&merge->list); 228 free_extent_map(merge); 229 } 230 } 231 232 /** 233 * unpint_extent_cache - unpin an extent from the cache 234 * @tree: tree to unpin the extent in 235 * @start: logical offset in the file 236 * @len: length of the extent 237 * @gen: generation that this extent has been modified in 238 * @prealloc: if this is set we need to clear the prealloc flag 239 * 240 * Called after an extent has been written to disk properly. Set the generation 241 * to the generation that actually added the file item to the inode so we know 242 * we need to sync this extent when we call fsync(). 243 */ 244 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, 245 u64 gen) 246 { 247 int ret = 0; 248 struct extent_map *em; 249 bool prealloc = false; 250 251 write_lock(&tree->lock); 252 em = lookup_extent_mapping(tree, start, len); 253 254 WARN_ON(!em || em->start != start); 255 256 if (!em) 257 goto out; 258 259 list_move(&em->list, &tree->modified_extents); 260 em->generation = gen; 261 clear_bit(EXTENT_FLAG_PINNED, &em->flags); 262 em->mod_start = em->start; 263 em->mod_len = em->len; 264 265 if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) { 266 prealloc = true; 267 clear_bit(EXTENT_FLAG_FILLING, &em->flags); 268 } 269 270 try_merge_map(tree, em); 271 272 if (prealloc) { 273 em->mod_start = em->start; 274 em->mod_len = em->len; 275 } 276 277 free_extent_map(em); 278 out: 279 write_unlock(&tree->lock); 280 return ret; 281 282 } 283 284 /** 285 * add_extent_mapping - add new extent map to the extent tree 286 * @tree: tree to insert new map in 287 * @em: map to insert 288 * 289 * Insert @em into @tree or perform a simple forward/backward merge with 290 * existing mappings. The extent_map struct passed in will be inserted 291 * into the tree directly, with an additional reference taken, or a 292 * reference dropped if the merge attempt was successful. 293 */ 294 int add_extent_mapping(struct extent_map_tree *tree, 295 struct extent_map *em) 296 { 297 int ret = 0; 298 struct rb_node *rb; 299 struct extent_map *exist; 300 301 exist = lookup_extent_mapping(tree, em->start, em->len); 302 if (exist) { 303 free_extent_map(exist); 304 ret = -EEXIST; 305 goto out; 306 } 307 rb = tree_insert(&tree->map, em->start, &em->rb_node); 308 if (rb) { 309 ret = -EEXIST; 310 goto out; 311 } 312 atomic_inc(&em->refs); 313 314 em->mod_start = em->start; 315 em->mod_len = em->len; 316 317 try_merge_map(tree, em); 318 out: 319 return ret; 320 } 321 322 /* simple helper to do math around the end of an extent, handling wrap */ 323 static u64 range_end(u64 start, u64 len) 324 { 325 if (start + len < start) 326 return (u64)-1; 327 return start + len; 328 } 329 330 struct extent_map *__lookup_extent_mapping(struct extent_map_tree *tree, 331 u64 start, u64 len, int strict) 332 { 333 struct extent_map *em; 334 struct rb_node *rb_node; 335 struct rb_node *prev = NULL; 336 struct rb_node *next = NULL; 337 u64 end = range_end(start, len); 338 339 rb_node = __tree_search(&tree->map, start, &prev, &next); 340 if (!rb_node) { 341 if (prev) 342 rb_node = prev; 343 else if (next) 344 rb_node = next; 345 else 346 return NULL; 347 } 348 349 em = rb_entry(rb_node, struct extent_map, rb_node); 350 351 if (strict && !(end > em->start && start < extent_map_end(em))) 352 return NULL; 353 354 atomic_inc(&em->refs); 355 return em; 356 } 357 358 /** 359 * lookup_extent_mapping - lookup extent_map 360 * @tree: tree to lookup in 361 * @start: byte offset to start the search 362 * @len: length of the lookup range 363 * 364 * Find and return the first extent_map struct in @tree that intersects the 365 * [start, len] range. There may be additional objects in the tree that 366 * intersect, so check the object returned carefully to make sure that no 367 * additional lookups are needed. 368 */ 369 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree, 370 u64 start, u64 len) 371 { 372 return __lookup_extent_mapping(tree, start, len, 1); 373 } 374 375 /** 376 * search_extent_mapping - find a nearby extent map 377 * @tree: tree to lookup in 378 * @start: byte offset to start the search 379 * @len: length of the lookup range 380 * 381 * Find and return the first extent_map struct in @tree that intersects the 382 * [start, len] range. 383 * 384 * If one can't be found, any nearby extent may be returned 385 */ 386 struct extent_map *search_extent_mapping(struct extent_map_tree *tree, 387 u64 start, u64 len) 388 { 389 return __lookup_extent_mapping(tree, start, len, 0); 390 } 391 392 /** 393 * remove_extent_mapping - removes an extent_map from the extent tree 394 * @tree: extent tree to remove from 395 * @em: extent map beeing removed 396 * 397 * Removes @em from @tree. No reference counts are dropped, and no checks 398 * are done to see if the range is in use 399 */ 400 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 401 { 402 int ret = 0; 403 404 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); 405 rb_erase(&em->rb_node, &tree->map); 406 if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags)) 407 list_del_init(&em->list); 408 em->in_tree = 0; 409 return ret; 410 } 411