fs/btrfs/extent_map.c

   1 #include <linux/err.h>
   2 #include <linux/slab.h>
   3 #include <linux/module.h>
   4 #include <linux/spinlock.h>
   5 #include <linux/hardirq.h>
   6 #include "ctree.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  *
  32  * Initialize the extent tree @tree.  Should be called for each new inode
  33  * or other user of the extent_map interface.
  34  */
  35 void extent_map_tree_init(struct extent_map_tree *tree)
  36 {
  37         tree->map = RB_ROOT;
  38         rwlock_init(&tree->lock);
  39 }
  40
  41 /**
  42  * alloc_extent_map - allocate new extent map structure
  43  *
  44  * Allocate a new extent_map structure.  The new structure is
  45  * returned with a reference count of one and needs to be
  46  * freed using free_extent_map()
  47  */
  48 struct extent_map *alloc_extent_map(void)
  49 {
  50         struct extent_map *em;
  51         em = kmem_cache_alloc(extent_map_cache, GFP_NOFS);
  52         if (!em)
  53                 return NULL;
  54         em->in_tree = 0;
  55         em->flags = 0;
  56         em->compress_type = BTRFS_COMPRESS_NONE;
  57         atomic_set(&em->refs, 1);
  58         return em;
  59 }
  60
  61 /**
  62  * free_extent_map - drop reference count of an extent_map
  63  * @em:         extent map beeing releasead
  64  *
  65  * Drops the reference out on @em by one and free the structure
  66  * if the reference count hits zero.
  67  */
  68 void free_extent_map(struct extent_map *em)
  69 {
  70         if (!em)
  71                 return;
  72         WARN_ON(atomic_read(&em->refs) == 0);
  73         if (atomic_dec_and_test(&em->refs)) {
  74                 WARN_ON(em->in_tree);
  75                 kmem_cache_free(extent_map_cache, em);
  76         }
  77 }
  78
  79 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  80                                    struct rb_node *node)
  81 {
  82         struct rb_node **p = &root->rb_node;
  83         struct rb_node *parent = NULL;
  84         struct extent_map *entry;
  85
  86         while (*p) {
  87                 parent = *p;
  88                 entry = rb_entry(parent, struct extent_map, rb_node);
  89
  90                 WARN_ON(!entry->in_tree);
  91
  92                 if (offset < entry->start)
  93                         p = &(*p)->rb_left;
  94                 else if (offset >= extent_map_end(entry))
  95                         p = &(*p)->rb_right;
  96                 else
  97                         return parent;
  98         }
  99
 100         entry = rb_entry(node, struct extent_map, rb_node);
 101         entry->in_tree = 1;
 102         rb_link_node(node, parent, p);
 103         rb_insert_color(node, root);
 104         return NULL;
 105 }
 106
 107 /*
 108  * search through the tree for an extent_map with a given offset.  If
 109  * it can't be found, try to find some neighboring extents
 110  */
 111 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 112                                      struct rb_node **prev_ret,
 113                                      struct rb_node **next_ret)
 114 {
 115         struct rb_node *n = root->rb_node;
 116         struct rb_node *prev = NULL;
 117         struct rb_node *orig_prev = NULL;
 118         struct extent_map *entry;
 119         struct extent_map *prev_entry = NULL;
 120
 121         while (n) {
 122                 entry = rb_entry(n, struct extent_map, rb_node);
 123                 prev = n;
 124                 prev_entry = entry;
 125
 126                 WARN_ON(!entry->in_tree);
 127
 128                 if (offset < entry->start)
 129                         n = n->rb_left;
 130                 else if (offset >= extent_map_end(entry))
 131                         n = n->rb_right;
 132                 else
 133                         return n;
 134         }
 135
 136         if (prev_ret) {
 137                 orig_prev = prev;
 138                 while (prev && offset >= extent_map_end(prev_entry)) {
 139                         prev = rb_next(prev);
 140                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 141                 }
 142                 *prev_ret = prev;
 143                 prev = orig_prev;
 144         }
 145
 146         if (next_ret) {
 147                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 148                 while (prev && offset < prev_entry->start) {
 149                         prev = rb_prev(prev);
 150                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 151                 }
 152                 *next_ret = prev;
 153         }
 154         return NULL;
 155 }
 156
 157 /* check to see if two extent_map structs are adjacent and safe to merge */
 158 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 159 {
 160         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 161                 return 0;
 162
 163         /*
 164          * don't merge compressed extents, we need to know their
 165          * actual size
 166          */
 167         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 168                 return 0;
 169
 170         if (extent_map_end(prev) == next->start &&
 171             prev->flags == next->flags &&
 172             prev->bdev == next->bdev &&
 173             ((next->block_start == EXTENT_MAP_HOLE &&
 174               prev->block_start == EXTENT_MAP_HOLE) ||
 175              (next->block_start == EXTENT_MAP_INLINE &&
 176               prev->block_start == EXTENT_MAP_INLINE) ||
 177              (next->block_start == EXTENT_MAP_DELALLOC &&
 178               prev->block_start == EXTENT_MAP_DELALLOC) ||
 179              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 180               next->block_start == extent_map_block_end(prev)))) {
 181                 return 1;
 182         }
 183         return 0;
 184 }
 185
 186 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
 187 {
 188         struct extent_map *merge = NULL;
 189         struct rb_node *rb;
 190
 191         if (em->start != 0) {
 192                 rb = rb_prev(&em->rb_node);
 193                 if (rb)
 194                         merge = rb_entry(rb, struct extent_map, rb_node);
 195                 if (rb && mergable_maps(merge, em)) {
 196                         em->start = merge->start;
 197                         em->len += merge->len;
 198                         em->block_len += merge->block_len;
 199                         em->block_start = merge->block_start;
 200                         merge->in_tree = 0;
 201                         rb_erase(&merge->rb_node, &tree->map);
 202                         free_extent_map(merge);
 203                 }
 204         }
 205
 206         rb = rb_next(&em->rb_node);
 207         if (rb)
 208                 merge = rb_entry(rb, struct extent_map, rb_node);
 209         if (rb && mergable_maps(em, merge)) {
 210                 em->len += merge->len;
 211                 em->block_len += merge->len;
 212                 rb_erase(&merge->rb_node, &tree->map);
 213                 merge->in_tree = 0;
 214                 free_extent_map(merge);
 215         }
 216 }
 217
 218 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
 219 {
 220         int ret = 0;
 221         struct extent_map *em;
 222
 223         write_lock(&tree->lock);
 224         em = lookup_extent_mapping(tree, start, len);
 225
 226         WARN_ON(!em || em->start != start);
 227
 228         if (!em)
 229                 goto out;
 230
 231         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 232
 233         try_merge_map(tree, em);
 234
 235         free_extent_map(em);
 236 out:
 237         write_unlock(&tree->lock);
 238         return ret;
 239
 240 }
 241
 242 /**
 243  * add_extent_mapping - add new extent map to the extent tree
 244  * @tree:       tree to insert new map in
 245  * @em:         map to insert
 246  *
 247  * Insert @em into @tree or perform a simple forward/backward merge with
 248  * existing mappings.  The extent_map struct passed in will be inserted
 249  * into the tree directly, with an additional reference taken, or a
 250  * reference dropped if the merge attempt was successful.
 251  */
 252 int add_extent_mapping(struct extent_map_tree *tree,
 253                        struct extent_map *em)
 254 {
 255         int ret = 0;
 256         struct rb_node *rb;
 257         struct extent_map *exist;
 258
 259         exist = lookup_extent_mapping(tree, em->start, em->len);
 260         if (exist) {
 261                 free_extent_map(exist);
 262                 ret = -EEXIST;
 263                 goto out;
 264         }
 265         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 266         if (rb) {
 267                 ret = -EEXIST;
 268                 goto out;
 269         }
 270         atomic_inc(&em->refs);
 271
 272         try_merge_map(tree, em);
 273 out:
 274         return ret;
 275 }
 276
 277 /* simple helper to do math around the end of an extent, handling wrap */
 278 static u64 range_end(u64 start, u64 len)
 279 {
 280         if (start + len < start)
 281                 return (u64)-1;
 282         return start + len;
 283 }
 284
 285 struct extent_map *__lookup_extent_mapping(struct extent_map_tree *tree,
 286                                            u64 start, u64 len, int strict)
 287 {
 288         struct extent_map *em;
 289         struct rb_node *rb_node;
 290         struct rb_node *prev = NULL;
 291         struct rb_node *next = NULL;
 292         u64 end = range_end(start, len);
 293
 294         rb_node = __tree_search(&tree->map, start, &prev, &next);
 295         if (!rb_node) {
 296                 if (prev)
 297                         rb_node = prev;
 298                 else if (next)
 299                         rb_node = next;
 300                 else
 301                         return NULL;
 302         }
 303
 304         em = rb_entry(rb_node, struct extent_map, rb_node);
 305
 306         if (strict && !(end > em->start && start < extent_map_end(em)))
 307                 return NULL;
 308
 309         atomic_inc(&em->refs);
 310         return em;
 311 }
 312
 313 /**
 314  * lookup_extent_mapping - lookup extent_map
 315  * @tree:       tree to lookup in
 316  * @start:      byte offset to start the search
 317  * @len:        length of the lookup range
 318  *
 319  * Find and return the first extent_map struct in @tree that intersects the
 320  * [start, len] range.  There may be additional objects in the tree that
 321  * intersect, so check the object returned carefully to make sure that no
 322  * additional lookups are needed.
 323  */
 324 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 325                                          u64 start, u64 len)
 326 {
 327         return __lookup_extent_mapping(tree, start, len, 1);
 328 }
 329
 330 /**
 331  * search_extent_mapping - find a nearby extent map
 332  * @tree:       tree to lookup in
 333  * @start:      byte offset to start the search
 334  * @len:        length of the lookup range
 335  *
 336  * Find and return the first extent_map struct in @tree that intersects the
 337  * [start, len] range.
 338  *
 339  * If one can't be found, any nearby extent may be returned
 340  */
 341 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
 342                                          u64 start, u64 len)
 343 {
 344         return __lookup_extent_mapping(tree, start, len, 0);
 345 }
 346
 347 /**
 348  * remove_extent_mapping - removes an extent_map from the extent tree
 349  * @tree:       extent tree to remove from
 350  * @em:         extent map beeing removed
 351  *
 352  * Removes @em from @tree.  No reference counts are dropped, and no checks
 353  * are done to see if the range is in use
 354  */
 355 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 356 {
 357         int ret = 0;
 358
 359         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 360         rb_erase(&em->rb_node, &tree->map);
 361         em->in_tree = 0;
 362         return ret;
 363 }