microblaze: Fix "kstack=" parsing
[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/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 }