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 /* temporary define until extent_map moves out of btrfs */ 10 struct kmem_cache *btrfs_cache_create(const char *name, size_t size, 11 unsigned long extra_flags, 12 void (*ctor)(void *, struct kmem_cache *, 13 unsigned long)); 14 15 static struct kmem_cache *extent_map_cache; 16 17 int __init extent_map_init(void) 18 { 19 extent_map_cache = btrfs_cache_create("extent_map", 20 sizeof(struct extent_map), 0, 21 NULL); 22 if (!extent_map_cache) 23 return -ENOMEM; 24 return 0; 25 } 26 27 void extent_map_exit(void) 28 { 29 if (extent_map_cache) 30 kmem_cache_destroy(extent_map_cache); 31 } 32 33 /** 34 * extent_map_tree_init - initialize extent map tree 35 * @tree: tree to initialize 36 * @mask: flags for memory allocations during tree operations 37 * 38 * Initialize the extent tree @tree. Should be called for each new inode 39 * or other user of the extent_map interface. 40 */ 41 void extent_map_tree_init(struct extent_map_tree *tree, gfp_t mask) 42 { 43 tree->map.rb_node = NULL; 44 spin_lock_init(&tree->lock); 45 } 46 47 /** 48 * alloc_extent_map - allocate new extent map structure 49 * @mask: memory allocation flags 50 * 51 * Allocate a new extent_map structure. The new structure is 52 * returned with a reference count of one and needs to be 53 * freed using free_extent_map() 54 */ 55 struct extent_map *alloc_extent_map(gfp_t mask) 56 { 57 struct extent_map *em; 58 em = kmem_cache_alloc(extent_map_cache, mask); 59 if (!em || IS_ERR(em)) 60 return em; 61 em->in_tree = 0; 62 em->flags = 0; 63 atomic_set(&em->refs, 1); 64 return em; 65 } 66 67 /** 68 * free_extent_map - drop reference count of an extent_map 69 * @em: extent map beeing releasead 70 * 71 * Drops the reference out on @em by one and free the structure 72 * if the reference count hits zero. 73 */ 74 void free_extent_map(struct extent_map *em) 75 { 76 if (!em) 77 return; 78 WARN_ON(atomic_read(&em->refs) == 0); 79 if (atomic_dec_and_test(&em->refs)) { 80 WARN_ON(em->in_tree); 81 kmem_cache_free(extent_map_cache, em); 82 } 83 } 84 85 static struct rb_node *tree_insert(struct rb_root *root, u64 offset, 86 struct rb_node *node) 87 { 88 struct rb_node **p = &root->rb_node; 89 struct rb_node *parent = NULL; 90 struct extent_map *entry; 91 92 while (*p) { 93 parent = *p; 94 entry = rb_entry(parent, struct extent_map, rb_node); 95 96 WARN_ON(!entry->in_tree); 97 98 if (offset < entry->start) 99 p = &(*p)->rb_left; 100 else if (offset >= extent_map_end(entry)) 101 p = &(*p)->rb_right; 102 else 103 return parent; 104 } 105 106 entry = rb_entry(node, struct extent_map, rb_node); 107 entry->in_tree = 1; 108 rb_link_node(node, parent, p); 109 rb_insert_color(node, root); 110 return NULL; 111 } 112 113 /* 114 * search through the tree for an extent_map with a given offset. If 115 * it can't be found, try to find some neighboring extents 116 */ 117 static struct rb_node *__tree_search(struct rb_root *root, u64 offset, 118 struct rb_node **prev_ret, 119 struct rb_node **next_ret) 120 { 121 struct rb_node *n = root->rb_node; 122 struct rb_node *prev = NULL; 123 struct rb_node *orig_prev = NULL; 124 struct extent_map *entry; 125 struct extent_map *prev_entry = NULL; 126 127 while (n) { 128 entry = rb_entry(n, struct extent_map, rb_node); 129 prev = n; 130 prev_entry = entry; 131 132 WARN_ON(!entry->in_tree); 133 134 if (offset < entry->start) 135 n = n->rb_left; 136 else if (offset >= extent_map_end(entry)) 137 n = n->rb_right; 138 else 139 return n; 140 } 141 142 if (prev_ret) { 143 orig_prev = prev; 144 while (prev && offset >= extent_map_end(prev_entry)) { 145 prev = rb_next(prev); 146 prev_entry = rb_entry(prev, struct extent_map, rb_node); 147 } 148 *prev_ret = prev; 149 prev = orig_prev; 150 } 151 152 if (next_ret) { 153 prev_entry = rb_entry(prev, struct extent_map, rb_node); 154 while (prev && offset < prev_entry->start) { 155 prev = rb_prev(prev); 156 prev_entry = rb_entry(prev, struct extent_map, rb_node); 157 } 158 *next_ret = prev; 159 } 160 return NULL; 161 } 162 163 /* 164 * look for an offset in the tree, and if it can't be found, return 165 * the first offset we can find smaller than 'offset'. 166 */ 167 static inline struct rb_node *tree_search(struct rb_root *root, u64 offset) 168 { 169 struct rb_node *prev; 170 struct rb_node *ret; 171 ret = __tree_search(root, offset, &prev, NULL); 172 if (!ret) 173 return prev; 174 return ret; 175 } 176 177 /* check to see if two extent_map structs are adjacent and safe to merge */ 178 static int mergable_maps(struct extent_map *prev, struct extent_map *next) 179 { 180 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags)) 181 return 0; 182 183 /* 184 * don't merge compressed extents, we need to know their 185 * actual size 186 */ 187 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags)) 188 return 0; 189 190 if (extent_map_end(prev) == next->start && 191 prev->flags == next->flags && 192 prev->bdev == next->bdev && 193 ((next->block_start == EXTENT_MAP_HOLE && 194 prev->block_start == EXTENT_MAP_HOLE) || 195 (next->block_start == EXTENT_MAP_INLINE && 196 prev->block_start == EXTENT_MAP_INLINE) || 197 (next->block_start == EXTENT_MAP_DELALLOC && 198 prev->block_start == EXTENT_MAP_DELALLOC) || 199 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 && 200 next->block_start == extent_map_block_end(prev)))) { 201 return 1; 202 } 203 return 0; 204 } 205 206 /** 207 * add_extent_mapping - add new extent map to the extent tree 208 * @tree: tree to insert new map in 209 * @em: map to insert 210 * 211 * Insert @em into @tree or perform a simple forward/backward merge with 212 * existing mappings. The extent_map struct passed in will be inserted 213 * into the tree directly, with an additional reference taken, or a 214 * reference dropped if the merge attempt was sucessfull. 215 */ 216 int add_extent_mapping(struct extent_map_tree *tree, 217 struct extent_map *em) 218 { 219 int ret = 0; 220 struct extent_map *merge = NULL; 221 struct rb_node *rb; 222 struct extent_map *exist; 223 224 exist = lookup_extent_mapping(tree, em->start, em->len); 225 if (exist) { 226 free_extent_map(exist); 227 ret = -EEXIST; 228 goto out; 229 } 230 assert_spin_locked(&tree->lock); 231 rb = tree_insert(&tree->map, em->start, &em->rb_node); 232 if (rb) { 233 ret = -EEXIST; 234 goto out; 235 } 236 atomic_inc(&em->refs); 237 if (em->start != 0) { 238 rb = rb_prev(&em->rb_node); 239 if (rb) 240 merge = rb_entry(rb, struct extent_map, rb_node); 241 if (rb && mergable_maps(merge, em)) { 242 em->start = merge->start; 243 em->len += merge->len; 244 em->block_len += merge->block_len; 245 em->block_start = merge->block_start; 246 merge->in_tree = 0; 247 rb_erase(&merge->rb_node, &tree->map); 248 free_extent_map(merge); 249 } 250 } 251 rb = rb_next(&em->rb_node); 252 if (rb) 253 merge = rb_entry(rb, struct extent_map, rb_node); 254 if (rb && mergable_maps(em, merge)) { 255 em->len += merge->len; 256 em->block_len += merge->len; 257 rb_erase(&merge->rb_node, &tree->map); 258 merge->in_tree = 0; 259 free_extent_map(merge); 260 } 261 out: 262 return ret; 263 } 264 265 /* simple helper to do math around the end of an extent, handling wrap */ 266 static u64 range_end(u64 start, u64 len) 267 { 268 if (start + len < start) 269 return (u64)-1; 270 return start + len; 271 } 272 273 /** 274 * lookup_extent_mapping - lookup extent_map 275 * @tree: tree to lookup in 276 * @start: byte offset to start the search 277 * @len: length of the lookup range 278 * 279 * Find and return the first extent_map struct in @tree that intersects the 280 * [start, len] range. There may be additional objects in the tree that 281 * intersect, so check the object returned carefully to make sure that no 282 * additional lookups are needed. 283 */ 284 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree, 285 u64 start, u64 len) 286 { 287 struct extent_map *em; 288 struct rb_node *rb_node; 289 struct rb_node *prev = NULL; 290 struct rb_node *next = NULL; 291 u64 end = range_end(start, len); 292 293 assert_spin_locked(&tree->lock); 294 rb_node = __tree_search(&tree->map, start, &prev, &next); 295 if (!rb_node && prev) { 296 em = rb_entry(prev, struct extent_map, rb_node); 297 if (end > em->start && start < extent_map_end(em)) 298 goto found; 299 } 300 if (!rb_node && next) { 301 em = rb_entry(next, struct extent_map, rb_node); 302 if (end > em->start && start < extent_map_end(em)) 303 goto found; 304 } 305 if (!rb_node) { 306 em = NULL; 307 goto out; 308 } 309 if (IS_ERR(rb_node)) { 310 em = ERR_PTR(PTR_ERR(rb_node)); 311 goto out; 312 } 313 em = rb_entry(rb_node, struct extent_map, rb_node); 314 if (end > em->start && start < extent_map_end(em)) 315 goto found; 316 317 em = NULL; 318 goto out; 319 320 found: 321 atomic_inc(&em->refs); 322 out: 323 return em; 324 } 325 326 /** 327 * remove_extent_mapping - removes an extent_map from the extent tree 328 * @tree: extent tree to remove from 329 * @em: extent map beeing removed 330 * 331 * Removes @em from @tree. No reference counts are dropped, and no checks 332 * are done to see if the range is in use 333 */ 334 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 335 { 336 int ret = 0; 337 338 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); 339 assert_spin_locked(&tree->lock); 340 rb_erase(&em->rb_node, &tree->map); 341 em->in_tree = 0; 342 return ret; 343 } 344