Linux 2.6.31.6
[linux/fpc-iii.git] / fs / btrfs / ref-cache.c
blobd0cc62bccb948e776fb9845c7da1a8f2119788f6
1 /*
2 * Copyright (C) 2008 Oracle. All rights reserved.
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.
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.
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.
19 #include <linux/sched.h>
20 #include <linux/sort.h>
21 #include "ctree.h"
22 #include "ref-cache.h"
23 #include "transaction.h"
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.
32 * kmalloc a leaf reference struct and update the counters for the
33 * total ref cache size
35 struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
36 int nr_extents)
38 struct btrfs_leaf_ref *ref;
39 size_t size = btrfs_leaf_ref_size(nr_extents);
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);
47 memset(ref, 0, sizeof(*ref));
48 atomic_set(&ref->usage, 1);
49 INIT_LIST_HEAD(&ref->list);
51 return ref;
55 * free a leaf reference struct and update the counters for the
56 * total ref cache size
58 void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
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);
66 BUG_ON(ref->in_tree);
67 kfree(ref);
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);
75 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
76 struct rb_node *node)
78 struct rb_node **p = &root->rb_node;
79 struct rb_node *parent = NULL;
80 struct btrfs_leaf_ref *entry;
82 while (*p) {
83 parent = *p;
84 entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
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;
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;
100 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
102 struct rb_node *n = root->rb_node;
103 struct btrfs_leaf_ref *entry;
105 while (n) {
106 entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
107 WARN_ON(!entry->in_tree);
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;
116 return NULL;
119 int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
120 int shared)
122 struct btrfs_leaf_ref *ref = NULL;
123 struct btrfs_leaf_ref_tree *tree = root->ref_tree;
125 if (shared)
126 tree = &root->fs_info->shared_ref_tree;
127 if (!tree)
128 return 0;
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;
141 rb_erase(&ref->rb_node, &tree->root);
142 list_del_init(&ref->list);
144 spin_unlock(&tree->lock);
145 btrfs_free_leaf_ref(root, ref);
146 cond_resched();
147 spin_lock(&tree->lock);
149 spin_unlock(&tree->lock);
150 return 0;
154 * find the leaf ref for a given extent. This returns the ref struct with
155 * a usage reference incremented
157 struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
158 u64 bytenr)
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;
175 if (tree != &root->fs_info->shared_ref_tree) {
176 tree = &root->fs_info->shared_ref_tree;
177 goto again;
179 return NULL;
183 * add a fully filled in leaf ref struct
184 * remove all the refs older than a given root generation
186 int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
187 int shared)
189 int ret = 0;
190 struct rb_node *rb;
191 struct btrfs_leaf_ref_tree *tree = root->ref_tree;
193 if (shared)
194 tree = &root->fs_info->shared_ref_tree;
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);
206 spin_unlock(&tree->lock);
207 return ret;
211 * remove a single leaf ref from the tree. This drops the ref held by the tree
212 * only
214 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
216 struct btrfs_leaf_ref_tree *tree;
218 if (!xchg(&ref->in_tree, 0))
219 return 0;
221 tree = ref->tree;
222 spin_lock(&tree->lock);
224 rb_erase(&ref->rb_node, &tree->root);
225 list_del_init(&ref->list);
227 spin_unlock(&tree->lock);
229 btrfs_free_leaf_ref(root, ref);
230 return 0;