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 spin_lock_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 /** 202 * add_extent_mapping - add new extent map to the extent tree 203 * @tree: tree to insert new map in 204 * @em: map to insert 205 * 206 * Insert @em into @tree or perform a simple forward/backward merge with 207 * existing mappings. The extent_map struct passed in will be inserted 208 * into the tree directly, with an additional reference taken, or a 209 * reference dropped if the merge attempt was sucessfull. 210 */ 211 int add_extent_mapping(struct extent_map_tree *tree, 212 struct extent_map *em) 213 { 214 int ret = 0; 215 struct extent_map *merge = NULL; 216 struct rb_node *rb; 217 struct extent_map *exist; 218 219 exist = lookup_extent_mapping(tree, em->start, em->len); 220 if (exist) { 221 free_extent_map(exist); 222 ret = -EEXIST; 223 goto out; 224 } 225 assert_spin_locked(&tree->lock); 226 rb = tree_insert(&tree->map, em->start, &em->rb_node); 227 if (rb) { 228 ret = -EEXIST; 229 goto out; 230 } 231 atomic_inc(&em->refs); 232 if (em->start != 0) { 233 rb = rb_prev(&em->rb_node); 234 if (rb) 235 merge = rb_entry(rb, struct extent_map, rb_node); 236 if (rb && mergable_maps(merge, em)) { 237 em->start = merge->start; 238 em->len += merge->len; 239 em->block_len += merge->block_len; 240 em->block_start = merge->block_start; 241 merge->in_tree = 0; 242 rb_erase(&merge->rb_node, &tree->map); 243 free_extent_map(merge); 244 } 245 } 246 rb = rb_next(&em->rb_node); 247 if (rb) 248 merge = rb_entry(rb, struct extent_map, rb_node); 249 if (rb && mergable_maps(em, merge)) { 250 em->len += merge->len; 251 em->block_len += merge->len; 252 rb_erase(&merge->rb_node, &tree->map); 253 merge->in_tree = 0; 254 free_extent_map(merge); 255 } 256 out: 257 return ret; 258 } 259 260 /* simple helper to do math around the end of an extent, handling wrap */ 261 static u64 range_end(u64 start, u64 len) 262 { 263 if (start + len < start) 264 return (u64)-1; 265 return start + len; 266 } 267 268 /** 269 * lookup_extent_mapping - lookup extent_map 270 * @tree: tree to lookup in 271 * @start: byte offset to start the search 272 * @len: length of the lookup range 273 * 274 * Find and return the first extent_map struct in @tree that intersects the 275 * [start, len] range. There may be additional objects in the tree that 276 * intersect, so check the object returned carefully to make sure that no 277 * additional lookups are needed. 278 */ 279 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree, 280 u64 start, u64 len) 281 { 282 struct extent_map *em; 283 struct rb_node *rb_node; 284 struct rb_node *prev = NULL; 285 struct rb_node *next = NULL; 286 u64 end = range_end(start, len); 287 288 assert_spin_locked(&tree->lock); 289 rb_node = __tree_search(&tree->map, start, &prev, &next); 290 if (!rb_node && prev) { 291 em = rb_entry(prev, struct extent_map, rb_node); 292 if (end > em->start && start < extent_map_end(em)) 293 goto found; 294 } 295 if (!rb_node && next) { 296 em = rb_entry(next, struct extent_map, rb_node); 297 if (end > em->start && start < extent_map_end(em)) 298 goto found; 299 } 300 if (!rb_node) { 301 em = NULL; 302 goto out; 303 } 304 if (IS_ERR(rb_node)) { 305 em = ERR_PTR(PTR_ERR(rb_node)); 306 goto out; 307 } 308 em = rb_entry(rb_node, struct extent_map, rb_node); 309 if (end > em->start && start < extent_map_end(em)) 310 goto found; 311 312 em = NULL; 313 goto out; 314 315 found: 316 atomic_inc(&em->refs); 317 out: 318 return em; 319 } 320 321 /** 322 * remove_extent_mapping - removes an extent_map from the extent tree 323 * @tree: extent tree to remove from 324 * @em: extent map beeing removed 325 * 326 * Removes @em from @tree. No reference counts are dropped, and no checks 327 * are done to see if the range is in use 328 */ 329 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 330 { 331 int ret = 0; 332 333 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); 334 assert_spin_locked(&tree->lock); 335 rb_erase(&em->rb_node, &tree->map); 336 em->in_tree = 0; 337 return ret; 338 } 339