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/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 EXPORT_SYMBOL(extent_map_tree_init);
  47
  48 /**
  49  * alloc_extent_map - allocate new extent map structure
  50  * @mask:       memory allocation flags
  51  *
  52  * Allocate a new extent_map structure.  The new structure is
  53  * returned with a reference count of one and needs to be
  54  * freed using free_extent_map()
  55  */
  56 struct extent_map *alloc_extent_map(gfp_t mask)
  57 {
  58         struct extent_map *em;
  59         em = kmem_cache_alloc(extent_map_cache, mask);
  60         if (!em || IS_ERR(em))
  61                 return em;
  62         em->in_tree = 0;
  63         em->flags = 0;
  64         atomic_set(&em->refs, 1);
  65         return em;
  66 }
  67 EXPORT_SYMBOL(alloc_extent_map);
  68
  69 /**
  70  * free_extent_map - drop reference count of an extent_map
  71  * @em:         extent map beeing releasead
  72  *
  73  * Drops the reference out on @em by one and free the structure
  74  * if the reference count hits zero.
  75  */
  76 void free_extent_map(struct extent_map *em)
  77 {
  78         if (!em)
  79                 return;
  80         WARN_ON(atomic_read(&em->refs) == 0);
  81         if (atomic_dec_and_test(&em->refs)) {
  82                 WARN_ON(em->in_tree);
  83                 kmem_cache_free(extent_map_cache, em);
  84         }
  85 }
  86 EXPORT_SYMBOL(free_extent_map);
  87
  88 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  89                                    struct rb_node *node)
  90 {
  91         struct rb_node **p = &root->rb_node;
  92         struct rb_node *parent = NULL;
  93         struct extent_map *entry;
  94
  95         while (*p) {
  96                 parent = *p;
  97                 entry = rb_entry(parent, struct extent_map, rb_node);
  98
  99                 WARN_ON(!entry->in_tree);
 100
 101                 if (offset < entry->start)
 102                         p = &(*p)->rb_left;
 103                 else if (offset >= extent_map_end(entry))
 104                         p = &(*p)->rb_right;
 105                 else
 106                         return parent;
 107         }
 108
 109         entry = rb_entry(node, struct extent_map, rb_node);
 110         entry->in_tree = 1;
 111         rb_link_node(node, parent, p);
 112         rb_insert_color(node, root);
 113         return NULL;
 114 }
 115
 116 /*
 117  * search through the tree for an extent_map with a given offset.  If
 118  * it can't be found, try to find some neighboring extents
 119  */
 120 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 121                                      struct rb_node **prev_ret,
 122                                      struct rb_node **next_ret)
 123 {
 124         struct rb_node *n = root->rb_node;
 125         struct rb_node *prev = NULL;
 126         struct rb_node *orig_prev = NULL;
 127         struct extent_map *entry;
 128         struct extent_map *prev_entry = NULL;
 129
 130         while (n) {
 131                 entry = rb_entry(n, struct extent_map, rb_node);
 132                 prev = n;
 133                 prev_entry = entry;
 134
 135                 WARN_ON(!entry->in_tree);
 136
 137                 if (offset < entry->start)
 138                         n = n->rb_left;
 139                 else if (offset >= extent_map_end(entry))
 140                         n = n->rb_right;
 141                 else
 142                         return n;
 143         }
 144
 145         if (prev_ret) {
 146                 orig_prev = prev;
 147                 while (prev && offset >= extent_map_end(prev_entry)) {
 148                         prev = rb_next(prev);
 149                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 150                 }
 151                 *prev_ret = prev;
 152                 prev = orig_prev;
 153         }
 154
 155         if (next_ret) {
 156                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 157                 while (prev && offset < prev_entry->start) {
 158                         prev = rb_prev(prev);
 159                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 160                 }
 161                 *next_ret = prev;
 162         }
 163         return NULL;
 164 }
 165
 166 /*
 167  * look for an offset in the tree, and if it can't be found, return
 168  * the first offset we can find smaller than 'offset'.
 169  */
 170 static inline struct rb_node *tree_search(struct rb_root *root, u64 offset)
 171 {
 172         struct rb_node *prev;
 173         struct rb_node *ret;
 174         ret = __tree_search(root, offset, &prev, NULL);
 175         if (!ret)
 176                 return prev;
 177         return ret;
 178 }
 179
 180 /* check to see if two extent_map structs are adjacent and safe to merge */
 181 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 182 {
 183         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 184                 return 0;
 185
 186         /*
 187          * don't merge compressed extents, we need to know their
 188          * actual size
 189          */
 190         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 191                 return 0;
 192
 193         if (extent_map_end(prev) == next->start &&
 194             prev->flags == next->flags &&
 195             prev->bdev == next->bdev &&
 196             ((next->block_start == EXTENT_MAP_HOLE &&
 197               prev->block_start == EXTENT_MAP_HOLE) ||
 198              (next->block_start == EXTENT_MAP_INLINE &&
 199               prev->block_start == EXTENT_MAP_INLINE) ||
 200              (next->block_start == EXTENT_MAP_DELALLOC &&
 201               prev->block_start == EXTENT_MAP_DELALLOC) ||
 202              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 203               next->block_start == extent_map_block_end(prev)))) {
 204                 return 1;
 205         }
 206         return 0;
 207 }
 208
 209 /**
 210  * add_extent_mapping - add new extent map to the extent tree
 211  * @tree:       tree to insert new map in
 212  * @em:         map to insert
 213  *
 214  * Insert @em into @tree or perform a simple forward/backward merge with
 215  * existing mappings.  The extent_map struct passed in will be inserted
 216  * into the tree directly, with an additional reference taken, or a
 217  * reference dropped if the merge attempt was sucessfull.
 218  */
 219 int add_extent_mapping(struct extent_map_tree *tree,
 220                        struct extent_map *em)
 221 {
 222         int ret = 0;
 223         struct extent_map *merge = NULL;
 224         struct rb_node *rb;
 225         struct extent_map *exist;
 226
 227         exist = lookup_extent_mapping(tree, em->start, em->len);
 228         if (exist) {
 229                 free_extent_map(exist);
 230                 ret = -EEXIST;
 231                 goto out;
 232         }
 233         assert_spin_locked(&tree->lock);
 234         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 235         if (rb) {
 236                 ret = -EEXIST;
 237                 goto out;
 238         }
 239         atomic_inc(&em->refs);
 240         if (em->start != 0) {
 241                 rb = rb_prev(&em->rb_node);
 242                 if (rb)
 243                         merge = rb_entry(rb, struct extent_map, rb_node);
 244                 if (rb && mergable_maps(merge, em)) {
 245                         em->start = merge->start;
 246                         em->len += merge->len;
 247                         em->block_len += merge->block_len;
 248                         em->block_start = merge->block_start;
 249                         merge->in_tree = 0;
 250                         rb_erase(&merge->rb_node, &tree->map);
 251                         free_extent_map(merge);
 252                 }
 253          }
 254         rb = rb_next(&em->rb_node);
 255         if (rb)
 256                 merge = rb_entry(rb, struct extent_map, rb_node);
 257         if (rb && mergable_maps(em, merge)) {
 258                 em->len += merge->len;
 259                 em->block_len += merge->len;
 260                 rb_erase(&merge->rb_node, &tree->map);
 261                 merge->in_tree = 0;
 262                 free_extent_map(merge);
 263         }
 264 out:
 265         return ret;
 266 }
 267 EXPORT_SYMBOL(add_extent_mapping);
 268
 269 /* simple helper to do math around the end of an extent, handling wrap */
 270 static u64 range_end(u64 start, u64 len)
 271 {
 272         if (start + len < start)
 273                 return (u64)-1;
 274         return start + len;
 275 }
 276
 277 /**
 278  * lookup_extent_mapping - lookup extent_map
 279  * @tree:       tree to lookup in
 280  * @start:      byte offset to start the search
 281  * @len:        length of the lookup range
 282  *
 283  * Find and return the first extent_map struct in @tree that intersects the
 284  * [start, len] range.  There may be additional objects in the tree that
 285  * intersect, so check the object returned carefully to make sure that no
 286  * additional lookups are needed.
 287  */
 288 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 289                                          u64 start, u64 len)
 290 {
 291         struct extent_map *em;
 292         struct rb_node *rb_node;
 293         struct rb_node *prev = NULL;
 294         struct rb_node *next = NULL;
 295         u64 end = range_end(start, len);
 296
 297         assert_spin_locked(&tree->lock);
 298         rb_node = __tree_search(&tree->map, start, &prev, &next);
 299         if (!rb_node && prev) {
 300                 em = rb_entry(prev, struct extent_map, rb_node);
 301                 if (end > em->start && start < extent_map_end(em))
 302                         goto found;
 303         }
 304         if (!rb_node && next) {
 305                 em = rb_entry(next, struct extent_map, rb_node);
 306                 if (end > em->start && start < extent_map_end(em))
 307                         goto found;
 308         }
 309         if (!rb_node) {
 310                 em = NULL;
 311                 goto out;
 312         }
 313         if (IS_ERR(rb_node)) {
 314                 em = ERR_PTR(PTR_ERR(rb_node));
 315                 goto out;
 316         }
 317         em = rb_entry(rb_node, struct extent_map, rb_node);
 318         if (end > em->start && start < extent_map_end(em))
 319                 goto found;
 320
 321         em = NULL;
 322         goto out;
 323
 324 found:
 325         atomic_inc(&em->refs);
 326 out:
 327         return em;
 328 }
 329 EXPORT_SYMBOL(lookup_extent_mapping);
 330
 331 /**
 332  * remove_extent_mapping - removes an extent_map from the extent tree
 333  * @tree:       extent tree to remove from
 334  * @em:         extent map beeing removed
 335  *
 336  * Removes @em from @tree.  No reference counts are dropped, and no checks
 337  * are done to see if the range is in use
 338  */
 339 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 340 {
 341         int ret = 0;
 342
 343         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 344         assert_spin_locked(&tree->lock);
 345         rb_erase(&em->rb_node, &tree->map);
 346         em->in_tree = 0;
 347         return ret;
 348 }
 349 EXPORT_SYMBOL(remove_extent_mapping);