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/sort.h>
21 #include "ctree.h"
22 #include "ref-cache.h"
23 #include "transaction.h"
24
25 /*
26 * leaf refs are used to cache the information about which extents
27 * a given leaf has references on. This allows us to process that leaf
28 * in btrfs_drop_snapshot without needing to read it back from disk.
29 */
30
31 /*
32 * kmalloc a leaf reference struct and update the counters for the
33 * total ref cache size
34 */
35 struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
36 int nr_extents)
37 {
38 struct btrfs_leaf_ref *ref;
39 size_t size = btrfs_leaf_ref_size(nr_extents);
40
41 ref = kmalloc(size, GFP_NOFS);
42 if (ref) {
43 spin_lock(&root->fs_info->ref_cache_lock);
44 root->fs_info->total_ref_cache_size += size;
45 spin_unlock(&root->fs_info->ref_cache_lock);
46
47 memset(ref, 0, sizeof(*ref));
48 atomic_set(&ref->usage, 1);
49 INIT_LIST_HEAD(&ref->list);
50 }
51 return ref;
52 }
53
54 /*
55 * free a leaf reference struct and update the counters for the
56 * total ref cache size
57 */
58 void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
59 {
60 if (!ref)
61 return;
62 WARN_ON(atomic_read(&ref->usage) == 0);
63 if (atomic_dec_and_test(&ref->usage)) {
64 size_t size = btrfs_leaf_ref_size(ref->nritems);
65
66 BUG_ON(ref->in_tree);
67 kfree(ref);
68
69 spin_lock(&root->fs_info->ref_cache_lock);
70 root->fs_info->total_ref_cache_size -= size;
71 spin_unlock(&root->fs_info->ref_cache_lock);
72 }
73 }
74
75 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
76 struct rb_node *node)
77 {
78 struct rb_node **p = &root->rb_node;
79 struct rb_node *parent = NULL;
80 struct btrfs_leaf_ref *entry;
81
82 while (*p) {
83 parent = *p;
84 entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
85
86 if (bytenr < entry->bytenr)
87 p = &(*p)->rb_left;
88 else if (bytenr > entry->bytenr)
89 p = &(*p)->rb_right;
90 else
91 return parent;
92 }
93
94 entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
95 rb_link_node(node, parent, p);
96 rb_insert_color(node, root);
97 return NULL;
98 }
99
100 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
101 {
102 struct rb_node *n = root->rb_node;
103 struct btrfs_leaf_ref *entry;
104
105 while (n) {
106 entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
107 WARN_ON(!entry->in_tree);
108
109 if (bytenr < entry->bytenr)
110 n = n->rb_left;
111 else if (bytenr > entry->bytenr)
112 n = n->rb_right;
113 else
114 return n;
115 }
116 return NULL;
117 }
118
119 int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
120 int shared)
121 {
122 struct btrfs_leaf_ref *ref = NULL;
123 struct btrfs_leaf_ref_tree *tree = root->ref_tree;
124
125 if (shared)
126 tree = &root->fs_info->shared_ref_tree;
127 if (!tree)
128 return 0;
129
130 spin_lock(&tree->lock);
131 while (!list_empty(&tree->list)) {
132 ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
133 BUG_ON(ref->tree != tree);
134 if (ref->root_gen > max_root_gen)
135 break;
136 if (!xchg(&ref->in_tree, 0)) {
137 cond_resched_lock(&tree->lock);
138 continue;
139 }
140
141 rb_erase(&ref->rb_node, &tree->root);
142 list_del_init(&ref->list);
143
144 spin_unlock(&tree->lock);
145 btrfs_free_leaf_ref(root, ref);
146 cond_resched();
147 spin_lock(&tree->lock);
148 }
149 spin_unlock(&tree->lock);
150 return 0;
151 }
152
153 /*
154 * find the leaf ref for a given extent. This returns the ref struct with
155 * a usage reference incremented
156 */
157 struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
158 u64 bytenr)
159 {
160 struct rb_node *rb;
161 struct btrfs_leaf_ref *ref = NULL;
162 struct btrfs_leaf_ref_tree *tree = root->ref_tree;
163 again:
164 if (tree) {
165 spin_lock(&tree->lock);
166 rb = tree_search(&tree->root, bytenr);
167 if (rb)
168 ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
169 if (ref)
170 atomic_inc(&ref->usage);
171 spin_unlock(&tree->lock);
172 if (ref)
173 return ref;
174 }
175 if (tree != &root->fs_info->shared_ref_tree) {
176 tree = &root->fs_info->shared_ref_tree;
177 goto again;
178 }
179 return NULL;
180 }
181
182 /*
183 * add a fully filled in leaf ref struct
184 * remove all the refs older than a given root generation
185 */
186 int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
187 int shared)
188 {
189 int ret = 0;
190 struct rb_node *rb;
191 struct btrfs_leaf_ref_tree *tree = root->ref_tree;
192
193 if (shared)
194 tree = &root->fs_info->shared_ref_tree;
195
196 spin_lock(&tree->lock);
197 rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
198 if (rb) {
199 ret = -EEXIST;
200 } else {
201 atomic_inc(&ref->usage);
202 ref->tree = tree;
203 ref->in_tree = 1;
204 list_add_tail(&ref->list, &tree->list);
205 }
206 spin_unlock(&tree->lock);
207 return ret;
208 }
209
210 /*
211 * remove a single leaf ref from the tree. This drops the ref held by the tree
212 * only
213 */
214 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
215 {
216 struct btrfs_leaf_ref_tree *tree;
217
218 if (!xchg(&ref->in_tree, 0))
219 return 0;
220
221 tree = ref->tree;
222 spin_lock(&tree->lock);
223
224 rb_erase(&ref->rb_node, &tree->root);
225 list_del_init(&ref->list);
226
227 spin_unlock(&tree->lock);
228
229 btrfs_free_leaf_ref(root, ref);
230 return 0;
231 }
232
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