Btrfs: Free free_space item properly in btrfs_trim_block_group()
[linux-2.6.git] / fs / btrfs / ref-cache.c
1 /*
2  * Copyright (C) 2008 Oracle.  All rights reserved.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public
6  * License v2 as published by the Free Software Foundation.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
11  * General Public License for more details.
12  *
13  * You should have received a copy of the GNU General Public
14  * License along with this program; if not, write to the
15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16  * Boston, MA 021110-1307, USA.
17  */
18
19 #include <linux/sched.h>
20 #include <linux/slab.h>
21 #include <linux/sort.h>
22 #include "ctree.h"
23 #include "ref-cache.h"
24 #include "transaction.h"
25
26 /*
27  * leaf refs are used to cache the information about which extents
28  * a given leaf has references on.  This allows us to process that leaf
29  * in btrfs_drop_snapshot without needing to read it back from disk.
30  */
31
32 /*
33  * kmalloc a leaf reference struct and update the counters for the
34  * total ref cache size
35  */
36 struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
37                                             int nr_extents)
38 {
39         struct btrfs_leaf_ref *ref;
40         size_t size = btrfs_leaf_ref_size(nr_extents);
41
42         ref = kmalloc(size, GFP_NOFS);
43         if (ref) {
44                 spin_lock(&root->fs_info->ref_cache_lock);
45                 root->fs_info->total_ref_cache_size += size;
46                 spin_unlock(&root->fs_info->ref_cache_lock);
47
48                 memset(ref, 0, sizeof(*ref));
49                 atomic_set(&ref->usage, 1);
50                 INIT_LIST_HEAD(&ref->list);
51         }
52         return ref;
53 }
54
55 /*
56  * free a leaf reference struct and update the counters for the
57  * total ref cache size
58  */
59 void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
60 {
61         if (!ref)
62                 return;
63         WARN_ON(atomic_read(&ref->usage) == 0);
64         if (atomic_dec_and_test(&ref->usage)) {
65                 size_t size = btrfs_leaf_ref_size(ref->nritems);
66
67                 BUG_ON(ref->in_tree);
68                 kfree(ref);
69
70                 spin_lock(&root->fs_info->ref_cache_lock);
71                 root->fs_info->total_ref_cache_size -= size;
72                 spin_unlock(&root->fs_info->ref_cache_lock);
73         }
74 }
75
76 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
77                                    struct rb_node *node)
78 {
79         struct rb_node **p = &root->rb_node;
80         struct rb_node *parent = NULL;
81         struct btrfs_leaf_ref *entry;
82
83         while (*p) {
84                 parent = *p;
85                 entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
86
87                 if (bytenr < entry->bytenr)
88                         p = &(*p)->rb_left;
89                 else if (bytenr > entry->bytenr)
90                         p = &(*p)->rb_right;
91                 else
92                         return parent;
93         }
94
95         entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
96         rb_link_node(node, parent, p);
97         rb_insert_color(node, root);
98         return NULL;
99 }
100
101 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
102 {
103         struct rb_node *n = root->rb_node;
104         struct btrfs_leaf_ref *entry;
105
106         while (n) {
107                 entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
108                 WARN_ON(!entry->in_tree);
109
110                 if (bytenr < entry->bytenr)
111                         n = n->rb_left;
112                 else if (bytenr > entry->bytenr)
113                         n = n->rb_right;
114                 else
115                         return n;
116         }
117         return NULL;
118 }
119
120 int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
121                            int shared)
122 {
123         struct btrfs_leaf_ref *ref = NULL;
124         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
125
126         if (shared)
127                 tree = &root->fs_info->shared_ref_tree;
128         if (!tree)
129                 return 0;
130
131         spin_lock(&tree->lock);
132         while (!list_empty(&tree->list)) {
133                 ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
134                 BUG_ON(ref->tree != tree);
135                 if (ref->root_gen > max_root_gen)
136                         break;
137                 if (!xchg(&ref->in_tree, 0)) {
138                         cond_resched_lock(&tree->lock);
139                         continue;
140                 }
141
142                 rb_erase(&ref->rb_node, &tree->root);
143                 list_del_init(&ref->list);
144
145                 spin_unlock(&tree->lock);
146                 btrfs_free_leaf_ref(root, ref);
147                 cond_resched();
148                 spin_lock(&tree->lock);
149         }
150         spin_unlock(&tree->lock);
151         return 0;
152 }
153
154 /*
155  * find the leaf ref for a given extent.  This returns the ref struct with
156  * a usage reference incremented
157  */
158 struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
159                                              u64 bytenr)
160 {
161         struct rb_node *rb;
162         struct btrfs_leaf_ref *ref = NULL;
163         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
164 again:
165         if (tree) {
166                 spin_lock(&tree->lock);
167                 rb = tree_search(&tree->root, bytenr);
168                 if (rb)
169                         ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
170                 if (ref)
171                         atomic_inc(&ref->usage);
172                 spin_unlock(&tree->lock);
173                 if (ref)
174                         return ref;
175         }
176         if (tree != &root->fs_info->shared_ref_tree) {
177                 tree = &root->fs_info->shared_ref_tree;
178                 goto again;
179         }
180         return NULL;
181 }
182
183 /*
184  * add a fully filled in leaf ref struct
185  * remove all the refs older than a given root generation
186  */
187 int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
188                        int shared)
189 {
190         int ret = 0;
191         struct rb_node *rb;
192         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
193
194         if (shared)
195                 tree = &root->fs_info->shared_ref_tree;
196
197         spin_lock(&tree->lock);
198         rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
199         if (rb) {
200                 ret = -EEXIST;
201         } else {
202                 atomic_inc(&ref->usage);
203                 ref->tree = tree;
204                 ref->in_tree = 1;
205                 list_add_tail(&ref->list, &tree->list);
206         }
207         spin_unlock(&tree->lock);
208         return ret;
209 }
210
211 /*
212  * remove a single leaf ref from the tree.  This drops the ref held by the tree
213  * only
214  */
215 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
216 {
217         struct btrfs_leaf_ref_tree *tree;
218
219         if (!xchg(&ref->in_tree, 0))
220                 return 0;
221
222         tree = ref->tree;
223         spin_lock(&tree->lock);
224
225         rb_erase(&ref->rb_node, &tree->root);
226         list_del_init(&ref->list);
227
228         spin_unlock(&tree->lock);
229
230         btrfs_free_leaf_ref(root, ref);
231         return 0;
232 }