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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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