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TOMOYO Linux Cross Reference
Linux/fs/btrfs/extent_map.c

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  1 #include <linux/err.h>
  2 #include <linux/slab.h>
  3 #include <linux/spinlock.h>
  4 #include <linux/hardirq.h>
  5 #include "ctree.h"
  6 #include "extent_map.h"
  7 #include "compression.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("btrfs_extent_map",
 15                         sizeof(struct extent_map), 0,
 16                         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         kmem_cache_destroy(extent_map_cache);
 25 }
 26 
 27 /**
 28  * extent_map_tree_init - initialize extent map tree
 29  * @tree:               tree to initialize
 30  *
 31  * Initialize the extent tree @tree.  Should be called for each new inode
 32  * or other user of the extent_map interface.
 33  */
 34 void extent_map_tree_init(struct extent_map_tree *tree)
 35 {
 36         tree->map = RB_ROOT;
 37         INIT_LIST_HEAD(&tree->modified_extents);
 38         rwlock_init(&tree->lock);
 39 }
 40 
 41 /**
 42  * alloc_extent_map - allocate new extent map structure
 43  *
 44  * Allocate a new extent_map structure.  The new structure is
 45  * returned with a reference count of one and needs to be
 46  * freed using free_extent_map()
 47  */
 48 struct extent_map *alloc_extent_map(void)
 49 {
 50         struct extent_map *em;
 51         em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
 52         if (!em)
 53                 return NULL;
 54         RB_CLEAR_NODE(&em->rb_node);
 55         em->flags = 0;
 56         em->compress_type = BTRFS_COMPRESS_NONE;
 57         em->generation = 0;
 58         atomic_set(&em->refs, 1);
 59         INIT_LIST_HEAD(&em->list);
 60         return em;
 61 }
 62 
 63 /**
 64  * free_extent_map - drop reference count of an extent_map
 65  * @em:         extent map being released
 66  *
 67  * Drops the reference out on @em by one and free the structure
 68  * if the reference count hits zero.
 69  */
 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(extent_map_in_tree(em));
 77                 WARN_ON(!list_empty(&em->list));
 78                 if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
 79                         kfree(em->map_lookup);
 80                 kmem_cache_free(extent_map_cache, em);
 81         }
 82 }
 83 
 84 /* simple helper to do math around the end of an extent, handling wrap */
 85 static u64 range_end(u64 start, u64 len)
 86 {
 87         if (start + len < start)
 88                 return (u64)-1;
 89         return start + len;
 90 }
 91 
 92 static int tree_insert(struct rb_root *root, struct extent_map *em)
 93 {
 94         struct rb_node **p = &root->rb_node;
 95         struct rb_node *parent = NULL;
 96         struct extent_map *entry = NULL;
 97         struct rb_node *orig_parent = NULL;
 98         u64 end = range_end(em->start, em->len);
 99 
100         while (*p) {
101                 parent = *p;
102                 entry = rb_entry(parent, struct extent_map, rb_node);
103 
104                 if (em->start < entry->start)
105                         p = &(*p)->rb_left;
106                 else if (em->start >= extent_map_end(entry))
107                         p = &(*p)->rb_right;
108                 else
109                         return -EEXIST;
110         }
111 
112         orig_parent = parent;
113         while (parent && em->start >= extent_map_end(entry)) {
114                 parent = rb_next(parent);
115                 entry = rb_entry(parent, struct extent_map, rb_node);
116         }
117         if (parent)
118                 if (end > entry->start && em->start < extent_map_end(entry))
119                         return -EEXIST;
120 
121         parent = orig_parent;
122         entry = rb_entry(parent, struct extent_map, rb_node);
123         while (parent && em->start < entry->start) {
124                 parent = rb_prev(parent);
125                 entry = rb_entry(parent, struct extent_map, rb_node);
126         }
127         if (parent)
128                 if (end > entry->start && em->start < extent_map_end(entry))
129                         return -EEXIST;
130 
131         rb_link_node(&em->rb_node, orig_parent, p);
132         rb_insert_color(&em->rb_node, root);
133         return 0;
134 }
135 
136 /*
137  * search through the tree for an extent_map with a given offset.  If
138  * it can't be found, try to find some neighboring extents
139  */
140 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
141                                      struct rb_node **prev_ret,
142                                      struct rb_node **next_ret)
143 {
144         struct rb_node *n = root->rb_node;
145         struct rb_node *prev = NULL;
146         struct rb_node *orig_prev = NULL;
147         struct extent_map *entry;
148         struct extent_map *prev_entry = NULL;
149 
150         while (n) {
151                 entry = rb_entry(n, struct extent_map, rb_node);
152                 prev = n;
153                 prev_entry = entry;
154 
155                 if (offset < entry->start)
156                         n = n->rb_left;
157                 else if (offset >= extent_map_end(entry))
158                         n = n->rb_right;
159                 else
160                         return n;
161         }
162 
163         if (prev_ret) {
164                 orig_prev = prev;
165                 while (prev && offset >= extent_map_end(prev_entry)) {
166                         prev = rb_next(prev);
167                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
168                 }
169                 *prev_ret = prev;
170                 prev = orig_prev;
171         }
172 
173         if (next_ret) {
174                 prev_entry = rb_entry(prev, struct extent_map, rb_node);
175                 while (prev && offset < prev_entry->start) {
176                         prev = rb_prev(prev);
177                         prev_entry = rb_entry(prev, struct extent_map, rb_node);
178                 }
179                 *next_ret = prev;
180         }
181         return NULL;
182 }
183 
184 /* check to see if two extent_map structs are adjacent and safe to merge */
185 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
186 {
187         if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
188                 return 0;
189 
190         /*
191          * don't merge compressed extents, we need to know their
192          * actual size
193          */
194         if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
195                 return 0;
196 
197         if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
198             test_bit(EXTENT_FLAG_LOGGING, &next->flags))
199                 return 0;
200 
201         /*
202          * We don't want to merge stuff that hasn't been written to the log yet
203          * since it may not reflect exactly what is on disk, and that would be
204          * bad.
205          */
206         if (!list_empty(&prev->list) || !list_empty(&next->list))
207                 return 0;
208 
209         if (extent_map_end(prev) == next->start &&
210             prev->flags == next->flags &&
211             prev->bdev == next->bdev &&
212             ((next->block_start == EXTENT_MAP_HOLE &&
213               prev->block_start == EXTENT_MAP_HOLE) ||
214              (next->block_start == EXTENT_MAP_INLINE &&
215               prev->block_start == EXTENT_MAP_INLINE) ||
216              (next->block_start == EXTENT_MAP_DELALLOC &&
217               prev->block_start == EXTENT_MAP_DELALLOC) ||
218              (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
219               next->block_start == extent_map_block_end(prev)))) {
220                 return 1;
221         }
222         return 0;
223 }
224 
225 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
226 {
227         struct extent_map *merge = NULL;
228         struct rb_node *rb;
229 
230         if (em->start != 0) {
231                 rb = rb_prev(&em->rb_node);
232                 if (rb)
233                         merge = rb_entry(rb, struct extent_map, rb_node);
234                 if (rb && mergable_maps(merge, em)) {
235                         em->start = merge->start;
236                         em->orig_start = merge->orig_start;
237                         em->len += merge->len;
238                         em->block_len += merge->block_len;
239                         em->block_start = merge->block_start;
240                         em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
241                         em->mod_start = merge->mod_start;
242                         em->generation = max(em->generation, merge->generation);
243 
244                         rb_erase(&merge->rb_node, &tree->map);
245                         RB_CLEAR_NODE(&merge->rb_node);
246                         free_extent_map(merge);
247                 }
248         }
249 
250         rb = rb_next(&em->rb_node);
251         if (rb)
252                 merge = rb_entry(rb, struct extent_map, rb_node);
253         if (rb && mergable_maps(em, merge)) {
254                 em->len += merge->len;
255                 em->block_len += merge->block_len;
256                 rb_erase(&merge->rb_node, &tree->map);
257                 RB_CLEAR_NODE(&merge->rb_node);
258                 em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
259                 em->generation = max(em->generation, merge->generation);
260                 free_extent_map(merge);
261         }
262 }
263 
264 /**
265  * unpin_extent_cache - unpin an extent from the cache
266  * @tree:       tree to unpin the extent in
267  * @start:      logical offset in the file
268  * @len:        length of the extent
269  * @gen:        generation that this extent has been modified in
270  *
271  * Called after an extent has been written to disk properly.  Set the generation
272  * to the generation that actually added the file item to the inode so we know
273  * we need to sync this extent when we call fsync().
274  */
275 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
276                        u64 gen)
277 {
278         int ret = 0;
279         struct extent_map *em;
280         bool prealloc = false;
281 
282         write_lock(&tree->lock);
283         em = lookup_extent_mapping(tree, start, len);
284 
285         WARN_ON(!em || em->start != start);
286 
287         if (!em)
288                 goto out;
289 
290         em->generation = gen;
291         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
292         em->mod_start = em->start;
293         em->mod_len = em->len;
294 
295         if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
296                 prealloc = true;
297                 clear_bit(EXTENT_FLAG_FILLING, &em->flags);
298         }
299 
300         try_merge_map(tree, em);
301 
302         if (prealloc) {
303                 em->mod_start = em->start;
304                 em->mod_len = em->len;
305         }
306 
307         free_extent_map(em);
308 out:
309         write_unlock(&tree->lock);
310         return ret;
311 
312 }
313 
314 void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
315 {
316         clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
317         if (extent_map_in_tree(em))
318                 try_merge_map(tree, em);
319 }
320 
321 static inline void setup_extent_mapping(struct extent_map_tree *tree,
322                                         struct extent_map *em,
323                                         int modified)
324 {
325         atomic_inc(&em->refs);
326         em->mod_start = em->start;
327         em->mod_len = em->len;
328 
329         if (modified)
330                 list_move(&em->list, &tree->modified_extents);
331         else
332                 try_merge_map(tree, em);
333 }
334 
335 /**
336  * add_extent_mapping - add new extent map to the extent tree
337  * @tree:       tree to insert new map in
338  * @em:         map to insert
339  *
340  * Insert @em into @tree or perform a simple forward/backward merge with
341  * existing mappings.  The extent_map struct passed in will be inserted
342  * into the tree directly, with an additional reference taken, or a
343  * reference dropped if the merge attempt was successful.
344  */
345 int add_extent_mapping(struct extent_map_tree *tree,
346                        struct extent_map *em, int modified)
347 {
348         int ret = 0;
349 
350         ret = tree_insert(&tree->map, em);
351         if (ret)
352                 goto out;
353 
354         setup_extent_mapping(tree, em, modified);
355 out:
356         return ret;
357 }
358 
359 static struct extent_map *
360 __lookup_extent_mapping(struct extent_map_tree *tree,
361                         u64 start, u64 len, int strict)
362 {
363         struct extent_map *em;
364         struct rb_node *rb_node;
365         struct rb_node *prev = NULL;
366         struct rb_node *next = NULL;
367         u64 end = range_end(start, len);
368 
369         rb_node = __tree_search(&tree->map, start, &prev, &next);
370         if (!rb_node) {
371                 if (prev)
372                         rb_node = prev;
373                 else if (next)
374                         rb_node = next;
375                 else
376                         return NULL;
377         }
378 
379         em = rb_entry(rb_node, struct extent_map, rb_node);
380 
381         if (strict && !(end > em->start && start < extent_map_end(em)))
382                 return NULL;
383 
384         atomic_inc(&em->refs);
385         return em;
386 }
387 
388 /**
389  * lookup_extent_mapping - lookup extent_map
390  * @tree:       tree to lookup in
391  * @start:      byte offset to start the search
392  * @len:        length of the lookup range
393  *
394  * Find and return the first extent_map struct in @tree that intersects the
395  * [start, len] range.  There may be additional objects in the tree that
396  * intersect, so check the object returned carefully to make sure that no
397  * additional lookups are needed.
398  */
399 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
400                                          u64 start, u64 len)
401 {
402         return __lookup_extent_mapping(tree, start, len, 1);
403 }
404 
405 /**
406  * search_extent_mapping - find a nearby extent map
407  * @tree:       tree to lookup in
408  * @start:      byte offset to start the search
409  * @len:        length of the lookup range
410  *
411  * Find and return the first extent_map struct in @tree that intersects the
412  * [start, len] range.
413  *
414  * If one can't be found, any nearby extent may be returned
415  */
416 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
417                                          u64 start, u64 len)
418 {
419         return __lookup_extent_mapping(tree, start, len, 0);
420 }
421 
422 /**
423  * remove_extent_mapping - removes an extent_map from the extent tree
424  * @tree:       extent tree to remove from
425  * @em:         extent map being removed
426  *
427  * Removes @em from @tree.  No reference counts are dropped, and no checks
428  * are done to see if the range is in use
429  */
430 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
431 {
432         int ret = 0;
433 
434         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
435         rb_erase(&em->rb_node, &tree->map);
436         if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
437                 list_del_init(&em->list);
438         RB_CLEAR_NODE(&em->rb_node);
439         return ret;
440 }
441 
442 void replace_extent_mapping(struct extent_map_tree *tree,
443                             struct extent_map *cur,
444                             struct extent_map *new,
445                             int modified)
446 {
447         WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
448         ASSERT(extent_map_in_tree(cur));
449         if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
450                 list_del_init(&cur->list);
451         rb_replace_node(&cur->rb_node, &new->rb_node, &tree->map);
452         RB_CLEAR_NODE(&cur->rb_node);
453 
454         setup_extent_mapping(tree, new, modified);
455 }
456 

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