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 /* check to see if two extent_map structs are adjacent and safe to merge */ 159 static int mergable_maps(struct extent_map *prev, struct extent_map *next) 160 { 161 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags)) 162 return 0; 163 164 /* 165 * don't merge compressed extents, we need to know their 166 * actual size 167 */ 168 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags)) 169 return 0; 170 171 if (extent_map_end(prev) == next->start && 172 prev->flags == next->flags && 173 prev->bdev == next->bdev && 174 ((next->block_start == EXTENT_MAP_HOLE && 175 prev->block_start == EXTENT_MAP_HOLE) || 176 (next->block_start == EXTENT_MAP_INLINE && 177 prev->block_start == EXTENT_MAP_INLINE) || 178 (next->block_start == EXTENT_MAP_DELALLOC && 179 prev->block_start == EXTENT_MAP_DELALLOC) || 180 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 && 181 next->block_start == extent_map_block_end(prev)))) { 182 return 1; 183 } 184 return 0; 185 } 186 187 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len) 188 { 189 int ret = 0; 190 struct extent_map *merge = NULL; 191 struct rb_node *rb; 192 struct extent_map *em; 193 194 write_lock(&tree->lock); 195 em = lookup_extent_mapping(tree, start, len); 196 197 WARN_ON(!em || em->start != start); 198 199 if (!em) 200 goto out; 201 202 clear_bit(EXTENT_FLAG_PINNED, &em->flags); 203 204 if (em->start != 0) { 205 rb = rb_prev(&em->rb_node); 206 if (rb) 207 merge = rb_entry(rb, struct extent_map, rb_node); 208 if (rb && mergable_maps(merge, em)) { 209 em->start = merge->start; 210 em->len += merge->len; 211 em->block_len += merge->block_len; 212 em->block_start = merge->block_start; 213 merge->in_tree = 0; 214 rb_erase(&merge->rb_node, &tree->map); 215 free_extent_map(merge); 216 } 217 } 218 219 rb = rb_next(&em->rb_node); 220 if (rb) 221 merge = rb_entry(rb, struct extent_map, rb_node); 222 if (rb && mergable_maps(em, merge)) { 223 em->len += merge->len; 224 em->block_len += merge->len; 225 rb_erase(&merge->rb_node, &tree->map); 226 merge->in_tree = 0; 227 free_extent_map(merge); 228 } 229 230 free_extent_map(em); 231 out: 232 write_unlock(&tree->lock); 233 return ret; 234 235 } 236 237 /** 238 * add_extent_mapping - add new extent map to the extent tree 239 * @tree: tree to insert new map in 240 * @em: map to insert 241 * 242 * Insert @em into @tree or perform a simple forward/backward merge with 243 * existing mappings. The extent_map struct passed in will be inserted 244 * into the tree directly, with an additional reference taken, or a 245 * reference dropped if the merge attempt was sucessfull. 246 */ 247 int add_extent_mapping(struct extent_map_tree *tree, 248 struct extent_map *em) 249 { 250 int ret = 0; 251 struct extent_map *merge = NULL; 252 struct rb_node *rb; 253 struct extent_map *exist; 254 255 exist = lookup_extent_mapping(tree, em->start, em->len); 256 if (exist) { 257 free_extent_map(exist); 258 ret = -EEXIST; 259 goto out; 260 } 261 rb = tree_insert(&tree->map, em->start, &em->rb_node); 262 if (rb) { 263 ret = -EEXIST; 264 goto out; 265 } 266 atomic_inc(&em->refs); 267 if (em->start != 0) { 268 rb = rb_prev(&em->rb_node); 269 if (rb) 270 merge = rb_entry(rb, struct extent_map, rb_node); 271 if (rb && mergable_maps(merge, em)) { 272 em->start = merge->start; 273 em->len += merge->len; 274 em->block_len += merge->block_len; 275 em->block_start = merge->block_start; 276 merge->in_tree = 0; 277 rb_erase(&merge->rb_node, &tree->map); 278 free_extent_map(merge); 279 } 280 } 281 rb = rb_next(&em->rb_node); 282 if (rb) 283 merge = rb_entry(rb, struct extent_map, rb_node); 284 if (rb && mergable_maps(em, merge)) { 285 em->len += merge->len; 286 em->block_len += merge->len; 287 rb_erase(&merge->rb_node, &tree->map); 288 merge->in_tree = 0; 289 free_extent_map(merge); 290 } 291 out: 292 return ret; 293 } 294 295 /* simple helper to do math around the end of an extent, handling wrap */ 296 static u64 range_end(u64 start, u64 len) 297 { 298 if (start + len < start) 299 return (u64)-1; 300 return start + len; 301 } 302 303 /** 304 * lookup_extent_mapping - lookup extent_map 305 * @tree: tree to lookup in 306 * @start: byte offset to start the search 307 * @len: length of the lookup range 308 * 309 * Find and return the first extent_map struct in @tree that intersects the 310 * [start, len] range. There may be additional objects in the tree that 311 * intersect, so check the object returned carefully to make sure that no 312 * additional lookups are needed. 313 */ 314 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree, 315 u64 start, u64 len) 316 { 317 struct extent_map *em; 318 struct rb_node *rb_node; 319 struct rb_node *prev = NULL; 320 struct rb_node *next = NULL; 321 u64 end = range_end(start, len); 322 323 rb_node = __tree_search(&tree->map, start, &prev, &next); 324 if (!rb_node && prev) { 325 em = rb_entry(prev, struct extent_map, rb_node); 326 if (end > em->start && start < extent_map_end(em)) 327 goto found; 328 } 329 if (!rb_node && next) { 330 em = rb_entry(next, struct extent_map, rb_node); 331 if (end > em->start && start < extent_map_end(em)) 332 goto found; 333 } 334 if (!rb_node) { 335 em = NULL; 336 goto out; 337 } 338 if (IS_ERR(rb_node)) { 339 em = ERR_PTR(PTR_ERR(rb_node)); 340 goto out; 341 } 342 em = rb_entry(rb_node, struct extent_map, rb_node); 343 if (end > em->start && start < extent_map_end(em)) 344 goto found; 345 346 em = NULL; 347 goto out; 348 349 found: 350 atomic_inc(&em->refs); 351 out: 352 return em; 353 } 354 355 /** 356 * search_extent_mapping - find a nearby extent map 357 * @tree: tree to lookup in 358 * @start: byte offset to start the search 359 * @len: length of the lookup range 360 * 361 * Find and return the first extent_map struct in @tree that intersects the 362 * [start, len] range. 363 * 364 * If one can't be found, any nearby extent may be returned 365 */ 366 struct extent_map *search_extent_mapping(struct extent_map_tree *tree, 367 u64 start, u64 len) 368 { 369 struct extent_map *em; 370 struct rb_node *rb_node; 371 struct rb_node *prev = NULL; 372 struct rb_node *next = NULL; 373 374 rb_node = __tree_search(&tree->map, start, &prev, &next); 375 if (!rb_node && prev) { 376 em = rb_entry(prev, struct extent_map, rb_node); 377 goto found; 378 } 379 if (!rb_node && next) { 380 em = rb_entry(next, struct extent_map, rb_node); 381 goto found; 382 } 383 if (!rb_node) { 384 em = NULL; 385 goto out; 386 } 387 if (IS_ERR(rb_node)) { 388 em = ERR_PTR(PTR_ERR(rb_node)); 389 goto out; 390 } 391 em = rb_entry(rb_node, struct extent_map, rb_node); 392 goto found; 393 394 em = NULL; 395 goto out; 396 397 found: 398 atomic_inc(&em->refs); 399 out: 400 return em; 401 } 402 403 /** 404 * remove_extent_mapping - removes an extent_map from the extent tree 405 * @tree: extent tree to remove from 406 * @em: extent map beeing removed 407 * 408 * Removes @em from @tree. No reference counts are dropped, and no checks 409 * are done to see if the range is in use 410 */ 411 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 412 { 413 int ret = 0; 414 415 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); 416 rb_erase(&em->rb_node, &tree->map); 417 em->in_tree = 0; 418 return ret; 419 } 420