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
extent_map_init(void)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
extent_map_exit(void)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 * @mask: flags for memory allocations during tree operations
32 *
33 * Initialize the extent tree @tree. Should be called for each new inode
34 * or other user of the extent_map interface.
35 */
extent_map_tree_init(struct extent_map_tree * tree,gfp_t mask)36 void extent_map_tree_init(struct extent_map_tree *tree, gfp_t mask)
37 {
38 tree->map = RB_ROOT;
39 rwlock_init(&tree->lock);
40 }
41
42 /**
43 * alloc_extent_map - allocate new extent map structure
44 * @mask: memory allocation flags
45 *
46 * Allocate a new extent_map structure. The new structure is
47 * returned with a reference count of one and needs to be
48 * freed using free_extent_map()
49 */
alloc_extent_map(gfp_t mask)50 struct extent_map *alloc_extent_map(gfp_t mask)
51 {
52 struct extent_map *em;
53 em = kmem_cache_alloc(extent_map_cache, mask);
54 if (!em)
55 return NULL;
56 em->in_tree = 0;
57 em->flags = 0;
58 em->compress_type = BTRFS_COMPRESS_NONE;
59 atomic_set(&em->refs, 1);
60 return em;
61 }
62
63 /**
64 * free_extent_map - drop reference count of an extent_map
65 * @em: extent map beeing releasead
66 *
67 * Drops the reference out on @em by one and free the structure
68 * if the reference count hits zero.
69 */
free_extent_map(struct extent_map * em)70 void free_extent_map(struct extent_map *em)
71 {
72 if (!em)
73 return;
74 WARN_ON(atomic_read(&em->refs) == 0);
75 if (atomic_dec_and_test(&em->refs)) {
76 WARN_ON(em->in_tree);
77 kmem_cache_free(extent_map_cache, em);
78 }
79 }
80
tree_insert(struct rb_root * root,u64 offset,struct rb_node * node)81 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
82 struct rb_node *node)
83 {
84 struct rb_node **p = &root->rb_node;
85 struct rb_node *parent = NULL;
86 struct extent_map *entry;
87
88 while (*p) {
89 parent = *p;
90 entry = rb_entry(parent, struct extent_map, rb_node);
91
92 WARN_ON(!entry->in_tree);
93
94 if (offset < entry->start)
95 p = &(*p)->rb_left;
96 else if (offset >= extent_map_end(entry))
97 p = &(*p)->rb_right;
98 else
99 return parent;
100 }
101
102 entry = rb_entry(node, struct extent_map, rb_node);
103 entry->in_tree = 1;
104 rb_link_node(node, parent, p);
105 rb_insert_color(node, root);
106 return NULL;
107 }
108
109 /*
110 * search through the tree for an extent_map with a given offset. If
111 * it can't be found, try to find some neighboring extents
112 */
__tree_search(struct rb_root * root,u64 offset,struct rb_node ** prev_ret,struct rb_node ** next_ret)113 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
114 struct rb_node **prev_ret,
115 struct rb_node **next_ret)
116 {
117 struct rb_node *n = root->rb_node;
118 struct rb_node *prev = NULL;
119 struct rb_node *orig_prev = NULL;
120 struct extent_map *entry;
121 struct extent_map *prev_entry = NULL;
122
123 while (n) {
124 entry = rb_entry(n, struct extent_map, rb_node);
125 prev = n;
126 prev_entry = entry;
127
128 WARN_ON(!entry->in_tree);
129
130 if (offset < entry->start)
131 n = n->rb_left;
132 else if (offset >= extent_map_end(entry))
133 n = n->rb_right;
134 else
135 return n;
136 }
137
138 if (prev_ret) {
139 orig_prev = prev;
140 while (prev && offset >= extent_map_end(prev_entry)) {
141 prev = rb_next(prev);
142 prev_entry = rb_entry(prev, struct extent_map, rb_node);
143 }
144 *prev_ret = prev;
145 prev = orig_prev;
146 }
147
148 if (next_ret) {
149 prev_entry = rb_entry(prev, struct extent_map, rb_node);
150 while (prev && offset < prev_entry->start) {
151 prev = rb_prev(prev);
152 prev_entry = rb_entry(prev, struct extent_map, rb_node);
153 }
154 *next_ret = prev;
155 }
156 return NULL;
157 }
158
159 /* check to see if two extent_map structs are adjacent and safe to merge */
mergable_maps(struct extent_map * prev,struct extent_map * next)160 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
161 {
162 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
163 return 0;
164
165 /*
166 * don't merge compressed extents, we need to know their
167 * actual size
168 */
169 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
170 return 0;
171
172 if (extent_map_end(prev) == next->start &&
173 prev->flags == next->flags &&
174 prev->bdev == next->bdev &&
175 ((next->block_start == EXTENT_MAP_HOLE &&
176 prev->block_start == EXTENT_MAP_HOLE) ||
177 (next->block_start == EXTENT_MAP_INLINE &&
178 prev->block_start == EXTENT_MAP_INLINE) ||
179 (next->block_start == EXTENT_MAP_DELALLOC &&
180 prev->block_start == EXTENT_MAP_DELALLOC) ||
181 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
182 next->block_start == extent_map_block_end(prev)))) {
183 return 1;
184 }
185 return 0;
186 }
187
unpin_extent_cache(struct extent_map_tree * tree,u64 start,u64 len)188 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
189 {
190 int ret = 0;
191 struct extent_map *merge = NULL;
192 struct rb_node *rb;
193 struct extent_map *em;
194
195 write_lock(&tree->lock);
196 em = lookup_extent_mapping(tree, start, len);
197
198 WARN_ON(!em || em->start != start);
199
200 if (!em)
201 goto out;
202
203 clear_bit(EXTENT_FLAG_PINNED, &em->flags);
204
205 if (em->start != 0) {
206 rb = rb_prev(&em->rb_node);
207 if (rb)
208 merge = rb_entry(rb, struct extent_map, rb_node);
209 if (rb && mergable_maps(merge, em)) {
210 em->start = merge->start;
211 em->len += merge->len;
212 em->block_len += merge->block_len;
213 em->block_start = merge->block_start;
214 merge->in_tree = 0;
215 rb_erase(&merge->rb_node, &tree->map);
216 free_extent_map(merge);
217 }
218 }
219
220 rb = rb_next(&em->rb_node);
221 if (rb)
222 merge = rb_entry(rb, struct extent_map, rb_node);
223 if (rb && mergable_maps(em, merge)) {
224 em->len += merge->len;
225 em->block_len += merge->len;
226 rb_erase(&merge->rb_node, &tree->map);
227 merge->in_tree = 0;
228 free_extent_map(merge);
229 }
230
231 free_extent_map(em);
232 out:
233 write_unlock(&tree->lock);
234 return ret;
235
236 }
237
238 /**
239 * add_extent_mapping - add new extent map to the extent tree
240 * @tree: tree to insert new map in
241 * @em: map to insert
242 *
243 * Insert @em into @tree or perform a simple forward/backward merge with
244 * existing mappings. The extent_map struct passed in will be inserted
245 * into the tree directly, with an additional reference taken, or a
246 * reference dropped if the merge attempt was successful.
247 */
add_extent_mapping(struct extent_map_tree * tree,struct extent_map * em)248 int add_extent_mapping(struct extent_map_tree *tree,
249 struct extent_map *em)
250 {
251 int ret = 0;
252 struct extent_map *merge = NULL;
253 struct rb_node *rb;
254 struct extent_map *exist;
255
256 exist = lookup_extent_mapping(tree, em->start, em->len);
257 if (exist) {
258 free_extent_map(exist);
259 ret = -EEXIST;
260 goto out;
261 }
262 rb = tree_insert(&tree->map, em->start, &em->rb_node);
263 if (rb) {
264 ret = -EEXIST;
265 goto out;
266 }
267 atomic_inc(&em->refs);
268 if (em->start != 0) {
269 rb = rb_prev(&em->rb_node);
270 if (rb)
271 merge = rb_entry(rb, struct extent_map, rb_node);
272 if (rb && mergable_maps(merge, em)) {
273 em->start = merge->start;
274 em->len += merge->len;
275 em->block_len += merge->block_len;
276 em->block_start = merge->block_start;
277 merge->in_tree = 0;
278 rb_erase(&merge->rb_node, &tree->map);
279 free_extent_map(merge);
280 }
281 }
282 rb = rb_next(&em->rb_node);
283 if (rb)
284 merge = rb_entry(rb, struct extent_map, rb_node);
285 if (rb && mergable_maps(em, merge)) {
286 em->len += merge->len;
287 em->block_len += merge->len;
288 rb_erase(&merge->rb_node, &tree->map);
289 merge->in_tree = 0;
290 free_extent_map(merge);
291 }
292 out:
293 return ret;
294 }
295
296 /* simple helper to do math around the end of an extent, handling wrap */
range_end(u64 start,u64 len)297 static u64 range_end(u64 start, u64 len)
298 {
299 if (start + len < start)
300 return (u64)-1;
301 return start + len;
302 }
303
304 /**
305 * lookup_extent_mapping - lookup extent_map
306 * @tree: tree to lookup in
307 * @start: byte offset to start the search
308 * @len: length of the lookup range
309 *
310 * Find and return the first extent_map struct in @tree that intersects the
311 * [start, len] range. There may be additional objects in the tree that
312 * intersect, so check the object returned carefully to make sure that no
313 * additional lookups are needed.
314 */
lookup_extent_mapping(struct extent_map_tree * tree,u64 start,u64 len)315 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
316 u64 start, u64 len)
317 {
318 struct extent_map *em;
319 struct rb_node *rb_node;
320 struct rb_node *prev = NULL;
321 struct rb_node *next = NULL;
322 u64 end = range_end(start, len);
323
324 rb_node = __tree_search(&tree->map, start, &prev, &next);
325 if (!rb_node && prev) {
326 em = rb_entry(prev, struct extent_map, rb_node);
327 if (end > em->start && start < extent_map_end(em))
328 goto found;
329 }
330 if (!rb_node && next) {
331 em = rb_entry(next, struct extent_map, rb_node);
332 if (end > em->start && start < extent_map_end(em))
333 goto found;
334 }
335 if (!rb_node) {
336 em = NULL;
337 goto out;
338 }
339 if (IS_ERR(rb_node)) {
340 em = ERR_CAST(rb_node);
341 goto out;
342 }
343 em = rb_entry(rb_node, struct extent_map, rb_node);
344 if (end > em->start && start < extent_map_end(em))
345 goto found;
346
347 em = NULL;
348 goto out;
349
350 found:
351 atomic_inc(&em->refs);
352 out:
353 return em;
354 }
355
356 /**
357 * search_extent_mapping - find a nearby extent map
358 * @tree: tree to lookup in
359 * @start: byte offset to start the search
360 * @len: length of the lookup range
361 *
362 * Find and return the first extent_map struct in @tree that intersects the
363 * [start, len] range.
364 *
365 * If one can't be found, any nearby extent may be returned
366 */
search_extent_mapping(struct extent_map_tree * tree,u64 start,u64 len)367 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
368 u64 start, u64 len)
369 {
370 struct extent_map *em;
371 struct rb_node *rb_node;
372 struct rb_node *prev = NULL;
373 struct rb_node *next = NULL;
374
375 rb_node = __tree_search(&tree->map, start, &prev, &next);
376 if (!rb_node && prev) {
377 em = rb_entry(prev, struct extent_map, rb_node);
378 goto found;
379 }
380 if (!rb_node && next) {
381 em = rb_entry(next, struct extent_map, rb_node);
382 goto found;
383 }
384 if (!rb_node) {
385 em = NULL;
386 goto out;
387 }
388 if (IS_ERR(rb_node)) {
389 em = ERR_CAST(rb_node);
390 goto out;
391 }
392 em = rb_entry(rb_node, struct extent_map, rb_node);
393 goto found;
394
395 em = NULL;
396 goto out;
397
398 found:
399 atomic_inc(&em->refs);
400 out:
401 return em;
402 }
403
404 /**
405 * remove_extent_mapping - removes an extent_map from the extent tree
406 * @tree: extent tree to remove from
407 * @em: extent map beeing removed
408 *
409 * Removes @em from @tree. No reference counts are dropped, and no checks
410 * are done to see if the range is in use
411 */
remove_extent_mapping(struct extent_map_tree * tree,struct extent_map * em)412 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
413 {
414 int ret = 0;
415
416 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
417 rb_erase(&em->rb_node, &tree->map);
418 em->in_tree = 0;
419 return ret;
420 }
421