1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2007 Oracle. All rights reserved.
4 */
5
6 #include <linux/sched.h>
7 #include "ctree.h"
8 #include "disk-io.h"
9 #include "print-tree.h"
10 #include "transaction.h"
11 #include "locking.h"
12
13 /*
14 * Defrag all the leaves in a given btree.
15 * Read all the leaves and try to get key order to
16 * better reflect disk order
17 */
18
19 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
20 struct btrfs_root *root)
21 {
22 struct btrfs_path *path = NULL;
23 struct btrfs_key key;
24 int ret = 0;
25 int wret;
26 int level;
27 int next_key_ret = 0;
28 u64 last_ret = 0;
29
30 if (root->fs_info->extent_root == root) {
31 /*
32 * there's recursion here right now in the tree locking,
33 * we can't defrag the extent root without deadlock
34 */
35 goto out;
36 }
37
38 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
39 goto out;
40
41 path = btrfs_alloc_path();
42 if (!path)
43 return -ENOMEM;
44
45 level = btrfs_header_level(root->node);
46
47 if (level == 0)
48 goto out;
49
50 if (root->defrag_progress.objectid == 0) {
51 struct extent_buffer *root_node;
52 u32 nritems;
53
54 root_node = btrfs_lock_root_node(root);
55 btrfs_set_lock_blocking_write(root_node);
56 nritems = btrfs_header_nritems(root_node);
57 root->defrag_max.objectid = 0;
58 /* from above we know this is not a leaf */
59 btrfs_node_key_to_cpu(root_node, &root->defrag_max,
60 nritems - 1);
61 btrfs_tree_unlock(root_node);
62 free_extent_buffer(root_node);
63 memset(&key, 0, sizeof(key));
64 } else {
65 memcpy(&key, &root->defrag_progress, sizeof(key));
66 }
67
68 path->keep_locks = 1;
69
70 ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
71 if (ret < 0)
72 goto out;
73 if (ret > 0) {
74 ret = 0;
75 goto out;
76 }
77 btrfs_release_path(path);
78 /*
79 * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
80 * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
81 * a deadlock (attempting to write lock an already write locked leaf).
82 */
83 path->lowest_level = 1;
84 wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
85
86 if (wret < 0) {
87 ret = wret;
88 goto out;
89 }
90 if (!path->nodes[1]) {
91 ret = 0;
92 goto out;
93 }
94 /*
95 * The node at level 1 must always be locked when our path has
96 * keep_locks set and lowest_level is 1, regardless of the value of
97 * path->slots[1].
98 */
99 BUG_ON(path->locks[1] == 0);
100 ret = btrfs_realloc_node(trans, root,
101 path->nodes[1], 0,
102 &last_ret,
103 &root->defrag_progress);
104 if (ret) {
105 WARN_ON(ret == -EAGAIN);
106 goto out;
107 }
108 /*
109 * Now that we reallocated the node we can find the next key. Note that
110 * btrfs_find_next_key() can release our path and do another search
111 * without COWing, this is because even with path->keep_locks = 1,
112 * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
113 * node when path->slots[node_level - 1] does not point to the last
114 * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
115 * we search for the next key after reallocating our node.
116 */
117 path->slots[1] = btrfs_header_nritems(path->nodes[1]);
118 next_key_ret = btrfs_find_next_key(root, path, &key, 1,
119 BTRFS_OLDEST_GENERATION);
120 if (next_key_ret == 0) {
121 memcpy(&root->defrag_progress, &key, sizeof(key));
122 ret = -EAGAIN;
123 }
124 out:
125 btrfs_free_path(path);
126 if (ret == -EAGAIN) {
127 if (root->defrag_max.objectid > root->defrag_progress.objectid)
128 goto done;
129 if (root->defrag_max.type > root->defrag_progress.type)
130 goto done;
131 if (root->defrag_max.offset > root->defrag_progress.offset)
132 goto done;
133 ret = 0;
134 }
135 done:
136 if (ret != -EAGAIN) {
137 memset(&root->defrag_progress, 0,
138 sizeof(root->defrag_progress));
139 root->defrag_trans_start = trans->transid;
140 }
141 return ret;
142 }