aboutsummaryrefslogtreecommitdiff
path: root/fs/btrfs/ref-cache.c
blob: a97314cf6bd6ef7ac44aa60a4485261a74e241a7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include "ctree.h"
#include "ref-cache.h"
#include "transaction.h"

/*
 * leaf refs are used to cache the information about which extents
 * a given leaf has references on.  This allows us to process that leaf
 * in btrfs_drop_snapshot without needing to read it back from disk.
 */

/*
 * kmalloc a leaf reference struct and update the counters for the
 * total ref cache size
 */
struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
					    int nr_extents)
{
	struct btrfs_leaf_ref *ref;
	size_t size = btrfs_leaf_ref_size(nr_extents);

	ref = kmalloc(size, GFP_NOFS);
	if (ref) {
		spin_lock(&root->fs_info->ref_cache_lock);
		root->fs_info->total_ref_cache_size += size;
		spin_unlock(&root->fs_info->ref_cache_lock);

		memset(ref, 0, sizeof(*ref));
		atomic_set(&ref->usage, 1);
		INIT_LIST_HEAD(&ref->list);
	}
	return ref;
}

/*
 * free a leaf reference struct and update the counters for the
 * total ref cache size
 */
void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
	if (!ref)
		return;
	WARN_ON(atomic_read(&ref->usage) == 0);
	if (atomic_dec_and_test(&ref->usage)) {
		size_t size = btrfs_leaf_ref_size(ref->nritems);

		BUG_ON(ref->in_tree);
		kfree(ref);

		spin_lock(&root->fs_info->ref_cache_lock);
		root->fs_info->total_ref_cache_size -= size;
		spin_unlock(&root->fs_info->ref_cache_lock);
	}
}

static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
				   struct rb_node *node)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent = NULL;
	struct btrfs_leaf_ref *entry;

	while (*p) {
		parent = *p;
		entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);

		if (bytenr < entry->bytenr)
			p = &(*p)->rb_left;
		else if (bytenr > entry->bytenr)
			p = &(*p)->rb_right;
		else
			return parent;
	}

	entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
	rb_link_node(node, parent, p);
	rb_insert_color(node, root);
	return NULL;
}

static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
{
	struct rb_node *n = root->rb_node;
	struct btrfs_leaf_ref *entry;

	while (n) {
		entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
		WARN_ON(!entry->in_tree);

		if (bytenr < entry->bytenr)
			n = n->rb_left;
		else if (bytenr > entry->bytenr)
			n = n->rb_right;
		else
			return n;
	}
	return NULL;
}

int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
			   int shared)
{
	struct btrfs_leaf_ref *ref = NULL;
	struct btrfs_leaf_ref_tree *tree = root->ref_tree;

	if (shared)
		tree = &root->fs_info->shared_ref_tree;
	if (!tree)
		return 0;

	spin_lock(&tree->lock);
	while (!list_empty(&tree->list)) {
		ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
		BUG_ON(ref->tree != tree);
		if (ref->root_gen > max_root_gen)
			break;
		if (!xchg(&ref->in_tree, 0)) {
			cond_resched_lock(&tree->lock);
			continue;
		}

		rb_erase(&ref->rb_node, &tree->root);
		list_del_init(&ref->list);

		spin_unlock(&tree->lock);
		btrfs_free_leaf_ref(root, ref);
		cond_resched();
		spin_lock(&tree->lock);
	}
	spin_unlock(&tree->lock);
	return 0;
}

/*
 * find the leaf ref for a given extent.  This returns the ref struct with
 * a usage reference incremented
 */
struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
					     u64 bytenr)
{
	struct rb_node *rb;
	struct btrfs_leaf_ref *ref = NULL;
	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
again:
	if (tree) {
		spin_lock(&tree->lock);
		rb = tree_search(&tree->root, bytenr);
		if (rb)
			ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
		if (ref)
			atomic_inc(&ref->usage);
		spin_unlock(&tree->lock);
		if (ref)
			return ref;
	}
	if (tree != &root->fs_info->shared_ref_tree) {
		tree = &root->fs_info->shared_ref_tree;
		goto again;
	}
	return NULL;
}

/*
 * add a fully filled in leaf ref struct
 * remove all the refs older than a given root generation
 */
int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
		       int shared)
{
	int ret = 0;
	struct rb_node *rb;
	struct btrfs_leaf_ref_tree *tree = root->ref_tree;

	if (shared)
		tree = &root->fs_info->shared_ref_tree;

	spin_lock(&tree->lock);
	rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
	if (rb) {
		ret = -EEXIST;
	} else {
		atomic_inc(&ref->usage);
		ref->tree = tree;
		ref->in_tree = 1;
		list_add_tail(&ref->list, &tree->list);
	}
	spin_unlock(&tree->lock);
	return ret;
}

/*
 * remove a single leaf ref from the tree.  This drops the ref held by the tree
 * only
 */
int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
	struct btrfs_leaf_ref_tree *tree;

	if (!xchg(&ref->in_tree, 0))
		return 0;

	tree = ref->tree;
	spin_lock(&tree->lock);

	rb_erase(&ref->rb_node, &tree->root);
	list_del_init(&ref->list);

	spin_unlock(&tree->lock);

	btrfs_free_leaf_ref(root, ref);
	return 0;
}