Btrfs: clean up code for merging extent maps
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / btrfs / extent_map.c
blob7c97b330145981d241cec9f13a75b3fa1869f8db
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"
10 static struct kmem_cache *extent_map_cache;
12 int __init extent_map_init(void)
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;
22 void extent_map_exit(void)
24 if (extent_map_cache)
25 kmem_cache_destroy(extent_map_cache);
28 /**
29 * extent_map_tree_init - initialize extent map tree
30 * @tree: tree to initialize
32 * Initialize the extent tree @tree. Should be called for each new inode
33 * or other user of the extent_map interface.
35 void extent_map_tree_init(struct extent_map_tree *tree)
37 tree->map = RB_ROOT;
38 rwlock_init(&tree->lock);
41 /**
42 * alloc_extent_map - allocate new extent map structure
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()
48 struct extent_map *alloc_extent_map(void)
50 struct extent_map *em;
51 em = kmem_cache_alloc(extent_map_cache, GFP_NOFS);
52 if (!em)
53 return NULL;
54 em->in_tree = 0;
55 em->flags = 0;
56 em->compress_type = BTRFS_COMPRESS_NONE;
57 atomic_set(&em->refs, 1);
58 return em;
61 /**
62 * free_extent_map - drop reference count of an extent_map
63 * @em: extent map beeing releasead
65 * Drops the reference out on @em by one and free the structure
66 * if the reference count hits zero.
68 void free_extent_map(struct extent_map *em)
70 if (!em)
71 return;
72 WARN_ON(atomic_read(&em->refs) == 0);
73 if (atomic_dec_and_test(&em->refs)) {
74 WARN_ON(em->in_tree);
75 kmem_cache_free(extent_map_cache, em);
79 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
80 struct rb_node *node)
82 struct rb_node **p = &root->rb_node;
83 struct rb_node *parent = NULL;
84 struct extent_map *entry;
86 while (*p) {
87 parent = *p;
88 entry = rb_entry(parent, struct extent_map, rb_node);
90 WARN_ON(!entry->in_tree);
92 if (offset < entry->start)
93 p = &(*p)->rb_left;
94 else if (offset >= extent_map_end(entry))
95 p = &(*p)->rb_right;
96 else
97 return parent;
100 entry = rb_entry(node, struct extent_map, rb_node);
101 entry->in_tree = 1;
102 rb_link_node(node, parent, p);
103 rb_insert_color(node, root);
104 return NULL;
108 * search through the tree for an extent_map with a given offset. If
109 * it can't be found, try to find some neighboring extents
111 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
112 struct rb_node **prev_ret,
113 struct rb_node **next_ret)
115 struct rb_node *n = root->rb_node;
116 struct rb_node *prev = NULL;
117 struct rb_node *orig_prev = NULL;
118 struct extent_map *entry;
119 struct extent_map *prev_entry = NULL;
121 while (n) {
122 entry = rb_entry(n, struct extent_map, rb_node);
123 prev = n;
124 prev_entry = entry;
126 WARN_ON(!entry->in_tree);
128 if (offset < entry->start)
129 n = n->rb_left;
130 else if (offset >= extent_map_end(entry))
131 n = n->rb_right;
132 else
133 return n;
136 if (prev_ret) {
137 orig_prev = prev;
138 while (prev && offset >= extent_map_end(prev_entry)) {
139 prev = rb_next(prev);
140 prev_entry = rb_entry(prev, struct extent_map, rb_node);
142 *prev_ret = prev;
143 prev = orig_prev;
146 if (next_ret) {
147 prev_entry = rb_entry(prev, struct extent_map, rb_node);
148 while (prev && offset < prev_entry->start) {
149 prev = rb_prev(prev);
150 prev_entry = rb_entry(prev, struct extent_map, rb_node);
152 *next_ret = prev;
154 return NULL;
157 /* check to see if two extent_map structs are adjacent and safe to merge */
158 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
160 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
161 return 0;
164 * don't merge compressed extents, we need to know their
165 * actual size
167 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
168 return 0;
170 if (extent_map_end(prev) == next->start &&
171 prev->flags == next->flags &&
172 prev->bdev == next->bdev &&
173 ((next->block_start == EXTENT_MAP_HOLE &&
174 prev->block_start == EXTENT_MAP_HOLE) ||
175 (next->block_start == EXTENT_MAP_INLINE &&
176 prev->block_start == EXTENT_MAP_INLINE) ||
177 (next->block_start == EXTENT_MAP_DELALLOC &&
178 prev->block_start == EXTENT_MAP_DELALLOC) ||
179 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
180 next->block_start == extent_map_block_end(prev)))) {
181 return 1;
183 return 0;
186 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
188 struct extent_map *merge = NULL;
189 struct rb_node *rb;
191 if (em->start != 0) {
192 rb = rb_prev(&em->rb_node);
193 if (rb)
194 merge = rb_entry(rb, struct extent_map, rb_node);
195 if (rb && mergable_maps(merge, em)) {
196 em->start = merge->start;
197 em->len += merge->len;
198 em->block_len += merge->block_len;
199 em->block_start = merge->block_start;
200 merge->in_tree = 0;
201 rb_erase(&merge->rb_node, &tree->map);
202 free_extent_map(merge);
206 rb = rb_next(&em->rb_node);
207 if (rb)
208 merge = rb_entry(rb, struct extent_map, rb_node);
209 if (rb && mergable_maps(em, merge)) {
210 em->len += merge->len;
211 em->block_len += merge->len;
212 rb_erase(&merge->rb_node, &tree->map);
213 merge->in_tree = 0;
214 free_extent_map(merge);
218 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
220 int ret = 0;
221 struct extent_map *em;
223 write_lock(&tree->lock);
224 em = lookup_extent_mapping(tree, start, len);
226 WARN_ON(!em || em->start != start);
228 if (!em)
229 goto out;
231 clear_bit(EXTENT_FLAG_PINNED, &em->flags);
233 try_merge_map(tree, em);
235 free_extent_map(em);
236 out:
237 write_unlock(&tree->lock);
238 return ret;
243 * add_extent_mapping - add new extent map to the extent tree
244 * @tree: tree to insert new map in
245 * @em: map to insert
247 * Insert @em into @tree or perform a simple forward/backward merge with
248 * existing mappings. The extent_map struct passed in will be inserted
249 * into the tree directly, with an additional reference taken, or a
250 * reference dropped if the merge attempt was successful.
252 int add_extent_mapping(struct extent_map_tree *tree,
253 struct extent_map *em)
255 int ret = 0;
256 struct rb_node *rb;
257 struct extent_map *exist;
259 exist = lookup_extent_mapping(tree, em->start, em->len);
260 if (exist) {
261 free_extent_map(exist);
262 ret = -EEXIST;
263 goto out;
265 rb = tree_insert(&tree->map, em->start, &em->rb_node);
266 if (rb) {
267 ret = -EEXIST;
268 goto out;
270 atomic_inc(&em->refs);
272 try_merge_map(tree, em);
273 out:
274 return ret;
277 /* simple helper to do math around the end of an extent, handling wrap */
278 static u64 range_end(u64 start, u64 len)
280 if (start + len < start)
281 return (u64)-1;
282 return start + len;
285 struct extent_map *__lookup_extent_mapping(struct extent_map_tree *tree,
286 u64 start, u64 len, int strict)
288 struct extent_map *em;
289 struct rb_node *rb_node;
290 struct rb_node *prev = NULL;
291 struct rb_node *next = NULL;
292 u64 end = range_end(start, len);
294 rb_node = __tree_search(&tree->map, start, &prev, &next);
295 if (!rb_node) {
296 if (prev)
297 rb_node = prev;
298 else if (next)
299 rb_node = next;
300 else
301 return NULL;
304 em = rb_entry(rb_node, struct extent_map, rb_node);
306 if (strict && !(end > em->start && start < extent_map_end(em)))
307 return NULL;
309 atomic_inc(&em->refs);
310 return em;
314 * lookup_extent_mapping - lookup extent_map
315 * @tree: tree to lookup in
316 * @start: byte offset to start the search
317 * @len: length of the lookup range
319 * Find and return the first extent_map struct in @tree that intersects the
320 * [start, len] range. There may be additional objects in the tree that
321 * intersect, so check the object returned carefully to make sure that no
322 * additional lookups are needed.
324 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
325 u64 start, u64 len)
327 return __lookup_extent_mapping(tree, start, len, 1);
331 * search_extent_mapping - find a nearby extent map
332 * @tree: tree to lookup in
333 * @start: byte offset to start the search
334 * @len: length of the lookup range
336 * Find and return the first extent_map struct in @tree that intersects the
337 * [start, len] range.
339 * If one can't be found, any nearby extent may be returned
341 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
342 u64 start, u64 len)
344 return __lookup_extent_mapping(tree, start, len, 0);
348 * remove_extent_mapping - removes an extent_map from the extent tree
349 * @tree: extent tree to remove from
350 * @em: extent map beeing removed
352 * Removes @em from @tree. No reference counts are dropped, and no checks
353 * are done to see if the range is in use
355 int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
357 int ret = 0;
359 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
360 rb_erase(&em->rb_node, &tree->map);
361 em->in_tree = 0;
362 return ret;