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-rw-r--r--fs/btrfs/extent_map.c351
1 files changed, 351 insertions, 0 deletions
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
new file mode 100644
index 000000000000..4a83e33ada32
--- /dev/null
+++ b/fs/btrfs/extent_map.c
@@ -0,0 +1,351 @@
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 */
11struct 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
16static struct kmem_cache *extent_map_cache;
17
18int __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
28void 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 */
42void 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}
47EXPORT_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 */
57struct 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}
68EXPORT_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 */
77void 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}
87EXPORT_SYMBOL(free_extent_map);
88
89static 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 */
121static 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 */
171static 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 */
182static 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 */
220int 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 }
266out:
267 return ret;
268}
269EXPORT_SYMBOL(add_extent_mapping);
270
271/* simple helper to do math around the end of an extent, handling wrap */
272static 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 */
290struct 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
326found:
327 atomic_inc(&em->refs);
328out:
329 return em;
330}
331EXPORT_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 */
341int 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}
351EXPORT_SYMBOL(remove_extent_mapping);