1 /*
2 * Copyright (C) 2007 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 "ctree.h"
21 #include "disk-io.h"
22 #include "print-tree.h"
23 #include "transaction.h"
24 #include "locking.h"
25
26 /*
27 * Defrag all the leaves in a given btree.
28 * Read all the leaves and try to get key order to
29 * better reflect disk order
30 */
31
btrfs_defrag_leaves(struct btrfs_trans_handle * trans,struct btrfs_root * root)32 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
33 struct btrfs_root *root)
34 {
35 struct btrfs_path *path = NULL;
36 struct btrfs_key key;
37 int ret = 0;
38 int wret;
39 int level;
40 int next_key_ret = 0;
41 u64 last_ret = 0;
42 u64 min_trans = 0;
43
44 if (root->fs_info->extent_root == root) {
45 /*
46 * there's recursion here right now in the tree locking,
47 * we can't defrag the extent root without deadlock
48 */
49 goto out;
50 }
51
52 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
53 goto out;
54
55 path = btrfs_alloc_path();
56 if (!path)
57 return -ENOMEM;
58
59 level = btrfs_header_level(root->node);
60
61 if (level == 0)
62 goto out;
63
64 if (root->defrag_progress.objectid == 0) {
65 struct extent_buffer *root_node;
66 u32 nritems;
67
68 root_node = btrfs_lock_root_node(root);
69 btrfs_set_lock_blocking(root_node);
70 nritems = btrfs_header_nritems(root_node);
71 root->defrag_max.objectid = 0;
72 /* from above we know this is not a leaf */
73 btrfs_node_key_to_cpu(root_node, &root->defrag_max,
74 nritems - 1);
75 btrfs_tree_unlock(root_node);
76 free_extent_buffer(root_node);
77 memset(&key, 0, sizeof(key));
78 } else {
79 memcpy(&key, &root->defrag_progress, sizeof(key));
80 }
81
82 path->keep_locks = 1;
83
84 ret = btrfs_search_forward(root, &key, path, min_trans);
85 if (ret < 0)
86 goto out;
87 if (ret > 0) {
88 ret = 0;
89 goto out;
90 }
91 btrfs_release_path(path);
92 /*
93 * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
94 * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
95 * a deadlock (attempting to write lock an already write locked leaf).
96 */
97 path->lowest_level = 1;
98 wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
99
100 if (wret < 0) {
101 ret = wret;
102 goto out;
103 }
104 if (!path->nodes[1]) {
105 ret = 0;
106 goto out;
107 }
108 /*
109 * The node at level 1 must always be locked when our path has
110 * keep_locks set and lowest_level is 1, regardless of the value of
111 * path->slots[1].
112 */
113 BUG_ON(path->locks[1] == 0);
114 ret = btrfs_realloc_node(trans, root,
115 path->nodes[1], 0,
116 &last_ret,
117 &root->defrag_progress);
118 if (ret) {
119 WARN_ON(ret == -EAGAIN);
120 goto out;
121 }
122 /*
123 * Now that we reallocated the node we can find the next key. Note that
124 * btrfs_find_next_key() can release our path and do another search
125 * without COWing, this is because even with path->keep_locks = 1,
126 * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
127 * node when path->slots[node_level - 1] does not point to the last
128 * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
129 * we search for the next key after reallocating our node.
130 */
131 path->slots[1] = btrfs_header_nritems(path->nodes[1]);
132 next_key_ret = btrfs_find_next_key(root, path, &key, 1,
133 min_trans);
134 if (next_key_ret == 0) {
135 memcpy(&root->defrag_progress, &key, sizeof(key));
136 ret = -EAGAIN;
137 }
138 out:
139 btrfs_free_path(path);
140 if (ret == -EAGAIN) {
141 if (root->defrag_max.objectid > root->defrag_progress.objectid)
142 goto done;
143 if (root->defrag_max.type > root->defrag_progress.type)
144 goto done;
145 if (root->defrag_max.offset > root->defrag_progress.offset)
146 goto done;
147 ret = 0;
148 }
149 done:
150 if (ret != -EAGAIN) {
151 memset(&root->defrag_progress, 0,
152 sizeof(root->defrag_progress));
153 root->defrag_trans_start = trans->transid;
154 }
155 return ret;
156 }
157