xref: /openbmc/linux/fs/btrfs/extent_map.c (revision df2634f43f5106947f3735a0b61a6527a4b278cd) 
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 
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_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  */
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  */
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 
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  */
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 */
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 
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 successfull.
247  */
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 */
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  */
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  */
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  */
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