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