1 #include <linux/err.h> 2 #include <linux/gfp.h> 3 #include <linux/slab.h> 4 #include <linux/module.h> 5 #include <linux/spinlock.h> 6 #include <linux/hardirq.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_node = NULL; 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 atomic_set(&em->refs, 1); 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(em->in_tree); 76 kmem_cache_free(extent_map_cache, em); 77 } 78 } 79 80 static struct rb_node *tree_insert(struct rb_root *root, u64 offset, 81 struct rb_node *node) 82 { 83 struct rb_node **p = &root->rb_node; 84 struct rb_node *parent = NULL; 85 struct extent_map *entry; 86 87 while (*p) { 88 parent = *p; 89 entry = rb_entry(parent, struct extent_map, rb_node); 90 91 WARN_ON(!entry->in_tree); 92 93 if (offset < entry->start) 94 p = &(*p)->rb_left; 95 else if (offset >= extent_map_end(entry)) 96 p = &(*p)->rb_right; 97 else 98 return parent; 99 } 100 101 entry = rb_entry(node, struct extent_map, rb_node); 102 entry->in_tree = 1; 103 rb_link_node(node, parent, p); 104 rb_insert_color(node, root); 105 return NULL; 106 } 107 108 /* 109 * search through the tree for an extent_map with a given offset. If 110 * it can't be found, try to find some neighboring extents 111 */ 112 static struct rb_node *__tree_search(struct rb_root *root, u64 offset, 113 struct rb_node **prev_ret, 114 struct rb_node **next_ret) 115 { 116 struct rb_node *n = root->rb_node; 117 struct rb_node *prev = NULL; 118 struct rb_node *orig_prev = NULL; 119 struct extent_map *entry; 120 struct extent_map *prev_entry = NULL; 121 122 while (n) { 123 entry = rb_entry(n, struct extent_map, rb_node); 124 prev = n; 125 prev_entry = entry; 126 127 WARN_ON(!entry->in_tree); 128 129 if (offset < entry->start) 130 n = n->rb_left; 131 else if (offset >= extent_map_end(entry)) 132 n = n->rb_right; 133 else 134 return n; 135 } 136 137 if (prev_ret) { 138 orig_prev = prev; 139 while (prev && offset >= extent_map_end(prev_entry)) { 140 prev = rb_next(prev); 141 prev_entry = rb_entry(prev, struct extent_map, rb_node); 142 } 143 *prev_ret = prev; 144 prev = orig_prev; 145 } 146 147 if (next_ret) { 148 prev_entry = rb_entry(prev, struct extent_map, rb_node); 149 while (prev && offset < prev_entry->start) { 150 prev = rb_prev(prev); 151 prev_entry = rb_entry(prev, struct extent_map, rb_node); 152 } 153 *next_ret = prev; 154 } 155 return NULL; 156 } 157 158 /* 159 * look for an offset in the tree, and if it can't be found, return 160 * the first offset we can find smaller than 'offset'. 161 */ 162 static inline struct rb_node *tree_search(struct rb_root *root, u64 offset) 163 { 164 struct rb_node *prev; 165 struct rb_node *ret; 166 ret = __tree_search(root, offset, &prev, NULL); 167 if (!ret) 168 return prev; 169 return ret; 170 } 171 172 /* check to see if two extent_map structs are adjacent and safe to merge */ 173 static int mergable_maps(struct extent_map *prev, struct extent_map *next) 174 { 175 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags)) 176 return 0; 177 178 /* 179 * don't merge compressed extents, we need to know their 180 * actual size 181 */ 182 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags)) 183 return 0; 184 185 if (extent_map_end(prev) == next->start && 186 prev->flags == next->flags && 187 prev->bdev == next->bdev && 188 ((next->block_start == EXTENT_MAP_HOLE && 189 prev->block_start == EXTENT_MAP_HOLE) || 190 (next->block_start == EXTENT_MAP_INLINE && 191 prev->block_start == EXTENT_MAP_INLINE) || 192 (next->block_start == EXTENT_MAP_DELALLOC && 193 prev->block_start == EXTENT_MAP_DELALLOC) || 194 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 && 195 next->block_start == extent_map_block_end(prev)))) { 196 return 1; 197 } 198 return 0; 199 } 200 201 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len) 202 { 203 int ret = 0; 204 struct extent_map *merge = NULL; 205 struct rb_node *rb; 206 struct extent_map *em; 207 208 write_lock(&tree->lock); 209 em = lookup_extent_mapping(tree, start, len); 210 211 WARN_ON(!em || em->start != start); 212 213 if (!em) 214 goto out; 215 216 clear_bit(EXTENT_FLAG_PINNED, &em->flags); 217 218 if (em->start != 0) { 219 rb = rb_prev(&em->rb_node); 220 if (rb) 221 merge = rb_entry(rb, struct extent_map, rb_node); 222 if (rb && mergable_maps(merge, em)) { 223 em->start = merge->start; 224 em->len += merge->len; 225 em->block_len += merge->block_len; 226 em->block_start = merge->block_start; 227 merge->in_tree = 0; 228 rb_erase(&merge->rb_node, &tree->map); 229 free_extent_map(merge); 230 } 231 } 232 233 rb = rb_next(&em->rb_node); 234 if (rb) 235 merge = rb_entry(rb, struct extent_map, rb_node); 236 if (rb && mergable_maps(em, merge)) { 237 em->len += merge->len; 238 em->block_len += merge->len; 239 rb_erase(&merge->rb_node, &tree->map); 240 merge->in_tree = 0; 241 free_extent_map(merge); 242 } 243 244 free_extent_map(em); 245 out: 246 write_unlock(&tree->lock); 247 return ret; 248 249 } 250 251 /** 252 * add_extent_mapping - add new extent map to the extent tree 253 * @tree: tree to insert new map in 254 * @em: map to insert 255 * 256 * Insert @em into @tree or perform a simple forward/backward merge with 257 * existing mappings. The extent_map struct passed in will be inserted 258 * into the tree directly, with an additional reference taken, or a 259 * reference dropped if the merge attempt was successfull. 260 */ 261 int add_extent_mapping(struct extent_map_tree *tree, 262 struct extent_map *em) 263 { 264 int ret = 0; 265 struct extent_map *merge = NULL; 266 struct rb_node *rb; 267 struct extent_map *exist; 268 269 exist = lookup_extent_mapping(tree, em->start, em->len); 270 if (exist) { 271 free_extent_map(exist); 272 ret = -EEXIST; 273 goto out; 274 } 275 rb = tree_insert(&tree->map, em->start, &em->rb_node); 276 if (rb) { 277 ret = -EEXIST; 278 goto out; 279 } 280 atomic_inc(&em->refs); 281 if (em->start != 0) { 282 rb = rb_prev(&em->rb_node); 283 if (rb) 284 merge = rb_entry(rb, struct extent_map, rb_node); 285 if (rb && mergable_maps(merge, em)) { 286 em->start = merge->start; 287 em->len += merge->len; 288 em->block_len += merge->block_len; 289 em->block_start = merge->block_start; 290 merge->in_tree = 0; 291 rb_erase(&merge->rb_node, &tree->map); 292 free_extent_map(merge); 293 } 294 } 295 rb = rb_next(&em->rb_node); 296 if (rb) 297 merge = rb_entry(rb, struct extent_map, rb_node); 298 if (rb && mergable_maps(em, merge)) { 299 em->len += merge->len; 300 em->block_len += merge->len; 301 rb_erase(&merge->rb_node, &tree->map); 302 merge->in_tree = 0; 303 free_extent_map(merge); 304 } 305 out: 306 return ret; 307 } 308 309 /* simple helper to do math around the end of an extent, handling wrap */ 310 static u64 range_end(u64 start, u64 len) 311 { 312 if (start + len < start) 313 return (u64)-1; 314 return start + len; 315 } 316 317 /** 318 * lookup_extent_mapping - lookup extent_map 319 * @tree: tree to lookup in 320 * @start: byte offset to start the search 321 * @len: length of the lookup range 322 * 323 * Find and return the first extent_map struct in @tree that intersects the 324 * [start, len] range. There may be additional objects in the tree that 325 * intersect, so check the object returned carefully to make sure that no 326 * additional lookups are needed. 327 */ 328 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree, 329 u64 start, u64 len) 330 { 331 struct extent_map *em; 332 struct rb_node *rb_node; 333 struct rb_node *prev = NULL; 334 struct rb_node *next = NULL; 335 u64 end = range_end(start, len); 336 337 rb_node = __tree_search(&tree->map, start, &prev, &next); 338 if (!rb_node && prev) { 339 em = rb_entry(prev, struct extent_map, rb_node); 340 if (end > em->start && start < extent_map_end(em)) 341 goto found; 342 } 343 if (!rb_node && next) { 344 em = rb_entry(next, struct extent_map, rb_node); 345 if (end > em->start && start < extent_map_end(em)) 346 goto found; 347 } 348 if (!rb_node) { 349 em = NULL; 350 goto out; 351 } 352 if (IS_ERR(rb_node)) { 353 em = ERR_PTR(PTR_ERR(rb_node)); 354 goto out; 355 } 356 em = rb_entry(rb_node, struct extent_map, rb_node); 357 if (end > em->start && start < extent_map_end(em)) 358 goto found; 359 360 em = NULL; 361 goto out; 362 363 found: 364 atomic_inc(&em->refs); 365 out: 366 return em; 367 } 368 369 /** 370 * search_extent_mapping - find a nearby extent map 371 * @tree: tree to lookup in 372 * @start: byte offset to start the search 373 * @len: length of the lookup range 374 * 375 * Find and return the first extent_map struct in @tree that intersects the 376 * [start, len] range. 377 * 378 * If one can't be found, any nearby extent may be returned 379 */ 380 struct extent_map *search_extent_mapping(struct extent_map_tree *tree, 381 u64 start, u64 len) 382 { 383 struct extent_map *em; 384 struct rb_node *rb_node; 385 struct rb_node *prev = NULL; 386 struct rb_node *next = NULL; 387 388 rb_node = __tree_search(&tree->map, start, &prev, &next); 389 if (!rb_node && prev) { 390 em = rb_entry(prev, struct extent_map, rb_node); 391 goto found; 392 } 393 if (!rb_node && next) { 394 em = rb_entry(next, struct extent_map, rb_node); 395 goto found; 396 } 397 if (!rb_node) { 398 em = NULL; 399 goto out; 400 } 401 if (IS_ERR(rb_node)) { 402 em = ERR_PTR(PTR_ERR(rb_node)); 403 goto out; 404 } 405 em = rb_entry(rb_node, struct extent_map, rb_node); 406 goto found; 407 408 em = NULL; 409 goto out; 410 411 found: 412 atomic_inc(&em->refs); 413 out: 414 return em; 415 } 416 417 /** 418 * remove_extent_mapping - removes an extent_map from the extent tree 419 * @tree: extent tree to remove from 420 * @em: extent map beeing removed 421 * 422 * Removes @em from @tree. No reference counts are dropped, and no checks 423 * are done to see if the range is in use 424 */ 425 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 426 { 427 int ret = 0; 428 429 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); 430 rb_erase(&em->rb_node, &tree->map); 431 em->in_tree = 0; 432 return ret; 433 } 434