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 /*
 118  * search through the tree for an extent_map with a given offset.  If
 119  * it can't be found, try to find some neighboring extents
 120  */
 121 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
 122                                      struct rb_node **prev_ret,
 123                                      struct rb_node **next_ret)
 124 {
 125         struct rb_node *n = root->rb_node;
 126         struct rb_node *prev = NULL;
 127         struct rb_node *orig_prev = NULL;
 128         struct extent_map *entry;
 129         struct extent_map *prev_entry = NULL;
 130
 131         while (n) {
 132                 entry = rb_entry(n, struct extent_map, rb_node);
 133                 prev = n;
 134                 prev_entry = entry;
 135
 136                 WARN_ON(!entry->in_tree);
 137
 138                 if (offset < entry->start)
 139                         n = n->rb_left;
 140                 else if (offset >= extent_map_end(entry))
 141                         n = n->rb_right;
 142                 else
 143                         return n;
 144         }
 145
 146         if (prev_ret) {
 147                 orig_prev = prev;
 148                 while (prev && offset >= extent_map_end(prev_entry)) {
 149                         prev = rb_next(prev);
 150                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 151                 }
 152                 *prev_ret = prev;
 153                 prev = orig_prev;
 154         }
 155
 156         if (next_ret) {
 157                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
 158                 while (prev && offset < prev_entry->start) {
 159                         prev = rb_prev(prev);
 160                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
 161                 }
 162                 *next_ret = prev;
 163         }
 164         return NULL;
 165 }
 166
 167 /*
 168  * look for an offset in the tree, and if it can't be found, return
 169  * the first offset we can find smaller than 'offset'.
 170  */
 171 static inline struct rb_node *tree_search(struct rb_root *root, u64 offset)
 172 {
 173         struct rb_node *prev;
 174         struct rb_node *ret;
 175         ret = __tree_search(root, offset, &prev, NULL);
 176         if (!ret)
 177                 return prev;
 178         return ret;
 179 }
 180
 181 /* check to see if two extent_map structs are adjacent and safe to merge */
 182 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
 183 {
 184         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
 185                 return 0;
 186
 187         /*
 188          * don't merge compressed extents, we need to know their
 189          * actual size
 190          */
 191         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
 192                 return 0;
 193
 194         if (extent_map_end(prev) == next->start &&
 195             prev->flags == next->flags &&
 196             prev->bdev == next->bdev &&
 197             ((next->block_start == EXTENT_MAP_HOLE &&
 198               prev->block_start == EXTENT_MAP_HOLE) ||
 199              (next->block_start == EXTENT_MAP_INLINE &&
 200               prev->block_start == EXTENT_MAP_INLINE) ||
 201              (next->block_start == EXTENT_MAP_DELALLOC &&
 202               prev->block_start == EXTENT_MAP_DELALLOC) ||
 203              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
 204               next->block_start == extent_map_block_end(prev)))) {
 205                 return 1;
 206         }
 207         return 0;
 208 }
 209
 210 /**
 211  * add_extent_mapping - add new extent map to the extent tree
 212  * @tree:       tree to insert new map in
 213  * @em:         map to insert
 214  *
 215  * Insert @em into @tree or perform a simple forward/backward merge with
 216  * existing mappings.  The extent_map struct passed in will be inserted
 217  * into the tree directly, with an additional reference taken, or a
 218  * reference dropped if the merge attempt was sucessfull.
 219  */
 220 int add_extent_mapping(struct extent_map_tree *tree,
 221                        struct extent_map *em)
 222 {
 223         int ret = 0;
 224         struct extent_map *merge = NULL;
 225         struct rb_node *rb;
 226         struct extent_map *exist;
 227
 228         exist = lookup_extent_mapping(tree, em->start, em->len);
 229         if (exist) {
 230                 free_extent_map(exist);
 231                 ret = -EEXIST;
 232                 goto out;
 233         }
 234         assert_spin_locked(&tree->lock);
 235         rb = tree_insert(&tree->map, em->start, &em->rb_node);
 236         if (rb) {
 237                 ret = -EEXIST;
 238                 free_extent_map(merge);
 239                 goto out;
 240         }
 241         atomic_inc(&em->refs);
 242         if (em->start != 0) {
 243                 rb = rb_prev(&em->rb_node);
 244                 if (rb)
 245                         merge = rb_entry(rb, struct extent_map, rb_node);
 246                 if (rb && mergable_maps(merge, em)) {
 247                         em->start = merge->start;
 248                         em->len += merge->len;
 249                         em->block_len += merge->block_len;
 250                         em->block_start = merge->block_start;
 251                         merge->in_tree = 0;
 252                         rb_erase(&merge->rb_node, &tree->map);
 253                         free_extent_map(merge);
 254                 }
 255          }
 256         rb = rb_next(&em->rb_node);
 257         if (rb)
 258                 merge = rb_entry(rb, struct extent_map, rb_node);
 259         if (rb && mergable_maps(em, merge)) {
 260                 em->len += merge->len;
 261                 em->block_len += merge->len;
 262                 rb_erase(&merge->rb_node, &tree->map);
 263                 merge->in_tree = 0;
 264                 free_extent_map(merge);
 265         }
 266 out:
 267         return ret;
 268 }
 269 EXPORT_SYMBOL(add_extent_mapping);
 270
 271 /* simple helper to do math around the end of an extent, handling wrap */
 272 static u64 range_end(u64 start, u64 len)
 273 {
 274         if (start + len < start)
 275                 return (u64)-1;
 276         return start + len;
 277 }
 278
 279 /**
 280  * lookup_extent_mapping - lookup extent_map
 281  * @tree:       tree to lookup in
 282  * @start:      byte offset to start the search
 283  * @len:        length of the lookup range
 284  *
 285  * Find and return the first extent_map struct in @tree that intersects the
 286  * [start, len] range.  There may be additional objects in the tree that
 287  * intersect, so check the object returned carefully to make sure that no
 288  * additional lookups are needed.
 289  */
 290 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
 291                                          u64 start, u64 len)
 292 {
 293         struct extent_map *em;
 294         struct rb_node *rb_node;
 295         struct rb_node *prev = NULL;
 296         struct rb_node *next = NULL;
 297         u64 end = range_end(start, len);
 298
 299         assert_spin_locked(&tree->lock);
 300         rb_node = __tree_search(&tree->map, start, &prev, &next);
 301         if (!rb_node && prev) {
 302                 em = rb_entry(prev, struct extent_map, rb_node);
 303                 if (end > em->start && start < extent_map_end(em))
 304                         goto found;
 305         }
 306         if (!rb_node && next) {
 307                 em = rb_entry(next, struct extent_map, rb_node);
 308                 if (end > em->start && start < extent_map_end(em))
 309                         goto found;
 310         }
 311         if (!rb_node) {
 312                 em = NULL;
 313                 goto out;
 314         }
 315         if (IS_ERR(rb_node)) {
 316                 em = ERR_PTR(PTR_ERR(rb_node));
 317                 goto out;
 318         }
 319         em = rb_entry(rb_node, struct extent_map, rb_node);
 320         if (end > em->start && start < extent_map_end(em))
 321                 goto found;
 322
 323         em = NULL;
 324         goto out;
 325
 326 found:
 327         atomic_inc(&em->refs);
 328 out:
 329         return em;
 330 }
 331 EXPORT_SYMBOL(lookup_extent_mapping);
 332
 333 /**
 334  * remove_extent_mapping - removes an extent_map from the extent tree
 335  * @tree:       extent tree to remove from
 336  * @em:         extent map beeing removed
 337  *
 338  * Removes @em from @tree.  No reference counts are dropped, and no checks
 339  * are done to see if the range is in use
 340  */
 341 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
 342 {
 343         int ret = 0;
 344
 345         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
 346         assert_spin_locked(&tree->lock);
 347         rb_erase(&em->rb_node, &tree->map);
 348         em->in_tree = 0;
 349         return ret;
 350 }
 351 EXPORT_SYMBOL(remove_extent_mapping);