fs/btrfs/extent_map.c

   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/version.h>
   7 #include <linux/hardirq.h>
   8 #include "extent_map.h"
   9
  10 /* temporary define until extent_map moves out of btrfs */
  11 struct kmem_cache *btrfs_cache_create(const char *name, size_t size,
  12                                        unsigned long extra_flags,
  13                                        void (*ctor)(void *, struct kmem_cache *,
  14                                                     unsigned long));
  15
  16 static struct kmem_cache *extent_map_cache;
  17
  18 int __init extent_map_init(void)
  19 {
  20         extent_map_cache = btrfs_cache_create("extent_map",
  21                                             sizeof(struct extent_map), 0,
  22                                             NULL);
  23         if (!extent_map_cache)
  24                 return -ENOMEM;
  25         return 0;
  26 }
  27
  28 void extent_map_exit(void)
  29 {
  30         if (extent_map_cache)
  31                 kmem_cache_destroy(extent_map_cache);
  32 }
  33
  34 /**
  35  * extent_map_tree_init - initialize extent map tree
  36  * @tree:               tree to initialize
  37  * @mask:               flags for memory allocations during tree operations
  38  *
  39  * Initialize the extent tree @tree.  Should be called for each new inode
  40  * or other user of the extent_map interface.
  41  */
  42 void extent_map_tree_init(struct extent_map_tree *tree, gfp_t mask)
  43 {
  44         tree->map.rb_node = NULL;
  45         spin_lock_init(&tree->lock);
  46 }
  47 EXPORT_SYMBOL(extent_map_tree_init);
  48
  49 /**
  50  * alloc_extent_map - allocate new extent map structure
  51  * @mask:       memory allocation flags
  52  *
  53  * Allocate a new extent_map structure.  The new structure is
  54  * returned with a reference count of one and needs to be
  55  * freed using free_extent_map()
  56  */
  57 struct extent_map *alloc_extent_map(gfp_t mask)
  58 {
  59         struct extent_map *em;
  60         em = kmem_cache_alloc(extent_map_cache, mask);
  61         if (!em || IS_ERR(em))
  62                 return em;
  63         em->in_tree = 0;
  64         em->flags = 0;
  65         atomic_set(&em->refs, 1);
  66         return em;
  67 }
  68 EXPORT_SYMBOL(alloc_extent_map);
  69
  70 /**
  71  * free_extent_map - drop reference count of an extent_map
  72  * @em:         extent map beeing releasead
  73  *
  74  * Drops the reference out on @em by one and free the structure
  75  * if the reference count hits zero.
  76  */
  77 void free_extent_map(struct extent_map *em)
  78 {
  79         if (!em)
  80                 return;
  81         WARN_ON(atomic_read(&em->refs) == 0);
  82         if (atomic_dec_and_test(&em->refs)) {
  83                 WARN_ON(em->in_tree);
  84                 kmem_cache_free(extent_map_cache, em);
  85         }
  86 }
  87 EXPORT_SYMBOL(free_extent_map);
  88
  89 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  90                                    struct rb_node *node)
  91 {
  92         struct rb_node ** p = &root->rb_node;
  93         struct rb_node * parent = NULL;
  94         struct extent_map *entry;
  95
  96         while(*p) {
  97                 parent = *p;
  98                 entry = rb_entry(parent, struct extent_map, rb_node);
  99
 100                 WARN_ON(!entry->in_tree);
 101
 102                 if (offset < entry->start)
 103                         p = &(*p)->rb_left;
 104                 else if (offset >= extent_map_end(entry))
 105                         p = &(*p)->rb_right;
 106                 else
 107                         return parent;
 108         }
 109
 110         entry = rb_entry(node, struct extent_map, rb_node);
 111         entry->in_tree = 1;
 112         rb_link_node(node, parent, p);
 113         rb_insert_color(node, root);
 114         return NULL;
 115 }
 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 static inline struct rb_node *tree_search(struct rb_root *root, u64 offset)
 164 {
 165         struct rb_node *prev;
 166         struct rb_node *ret;
 167         ret = __tree_search(root, offset, &prev, NULL);
 168         if (!ret)
 169                 return prev;
 170         return ret;
 171 }
 172
 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         if (extent_map_end(prev) == next->start &&
 179             prev->flags == next->flags &&
 180             prev->bdev == next->bdev &&
 181             ((next->block_start == EXTENT_MAP_HOLE &&
 182               prev->block_start == EXTENT_MAP_HOLE) ||
 183              (next->block_start == EXTENT_MAP_INLINE &&
 184               prev->block_start == EXTENT_MAP_INLINE) ||
 185              (next->block_start == EXTENT_MAP_DELALLOC &&
 186               prev->block_start == EXTENT_MAP_DELALLOC) ||
 187              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 188               next->block_start == extent_map_block_end(prev)))) {
 189                 return 1;
 190         }
 191         return 0;
 192 }
 193
 194 /**
 195  * add_extent_mapping - add new extent map to the extent tree
 196  * @tree:       tree to insert new map in
 197  * @em:         map to insert
 198  *
 199  * Insert @em into @tree or perform a simple forward/backward merge with
 200  * existing mappings.  The extent_map struct passed in will be inserted
 201  * into the tree directly, with an additional reference taken, or a
 202  * reference dropped if the merge attempt was sucessfull.
 203  */
 204 int add_extent_mapping(struct extent_map_tree *tree,
 205                        struct extent_map *em)
 206 {
 207         int ret = 0;
 208         struct extent_map *merge = NULL;
 209         struct rb_node *rb;
 210
 211         BUG_ON(spin_trylock(&tree->lock));
 212         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 213         if (rb) {
 214                 ret = -EEXIST;
 215                 free_extent_map(merge);
 216                 goto out;
 217         }
 218         atomic_inc(&em->refs);
 219         if (em->start != 0) {
 220                 rb = rb_prev(&em->rb_node);
 221                 if (rb)
 222                         merge = rb_entry(rb, struct extent_map, rb_node);
 223                 if (rb && mergable_maps(merge, em)) {
 224                         em->start = merge->start;
 225                         em->len += merge->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         rb = rb_next(&em->rb_node);
 233         if (rb)
 234                 merge = rb_entry(rb, struct extent_map, rb_node);
 235         if (rb && mergable_maps(em, merge)) {
 236                 em->len += merge->len;
 237                 rb_erase(&merge->rb_node, &tree->map);
 238                 merge->in_tree = 0;
 239                 free_extent_map(merge);
 240         }
 241 out:
 242         return ret;
 243 }
 244 EXPORT_SYMBOL(add_extent_mapping);
 245
 246 static u64 range_end(u64 start, u64 len)
 247 {
 248         if (start + len < start)
 249                 return (u64)-1;
 250         return start + len;
 251 }
 252
 253 /**
 254  * lookup_extent_mapping - lookup extent_map
 255  * @tree:       tree to lookup in
 256  * @start:      byte offset to start the search
 257  * @len:        length of the lookup range
 258  *
 259  * Find and return the first extent_map struct in @tree that intersects the
 260  * [start, len] range.  There may be additional objects in the tree that
 261  * intersect, so check the object returned carefully to make sure that no
 262  * additional lookups are needed.
 263  */
 264 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 265                                          u64 start, u64 len)
 266 {
 267         struct extent_map *em;
 268         struct rb_node *rb_node;
 269         struct rb_node *prev = NULL;
 270         struct rb_node *next = NULL;
 271         u64 end = range_end(start, len);
 272
 273         BUG_ON(spin_trylock(&tree->lock));
 274         rb_node = __tree_search(&tree->map, start, &prev, &next);
 275         if (!rb_node && prev) {
 276                 em = rb_entry(prev, struct extent_map, rb_node);
 277                 if (end > em->start && start < extent_map_end(em))
 278                         goto found;
 279         }
 280         if (!rb_node && next) {
 281                 em = rb_entry(next, struct extent_map, rb_node);
 282                 if (end > em->start && start < extent_map_end(em))
 283                         goto found;
 284         }
 285         if (!rb_node) {
 286                 em = NULL;
 287                 goto out;
 288         }
 289         if (IS_ERR(rb_node)) {
 290                 em = ERR_PTR(PTR_ERR(rb_node));
 291                 goto out;
 292         }
 293         em = rb_entry(rb_node, struct extent_map, rb_node);
 294         if (end > em->start && start < extent_map_end(em))
 295                 goto found;
 296
 297         em = NULL;
 298         goto out;
 299
 300 found:
 301         atomic_inc(&em->refs);
 302 out:
 303         return em;
 304 }
 305 EXPORT_SYMBOL(lookup_extent_mapping);
 306
 307 /**
 308  * remove_extent_mapping - removes an extent_map from the extent tree
 309  * @tree:       extent tree to remove from
 310  * @em:         extent map beeing removed
 311  *
 312  * Removes @em from @tree.  No reference counts are dropped, and no checks
 313  * are done to see if the range is in use
 314  */
 315 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 316 {
 317         int ret = 0;
 318
 319         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 320         BUG_ON(spin_trylock(&tree->lock));
 321         rb_erase(&em->rb_node, &tree->map);
 322         em->in_tree = 0;
 323         return ret;
 324 }
 325 EXPORT_SYMBOL(remove_extent_mapping);