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
btrfs_defrag_leaves(struct btrfs_trans_handle * trans,struct btrfs_root * root)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_SHAREABLE, &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 nritems = btrfs_header_nritems(root_node);
56 root->defrag_max.objectid = 0;
57 /* from above we know this is not a leaf */
58 btrfs_node_key_to_cpu(root_node, &root->defrag_max,
59 nritems - 1);
60 btrfs_tree_unlock(root_node);
61 free_extent_buffer(root_node);
62 memset(&key, 0, sizeof(key));
63 } else {
64 memcpy(&key, &root->defrag_progress, sizeof(key));
65 }
66
67 path->keep_locks = 1;
68
69 ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
70 if (ret < 0)
71 goto out;
72 if (ret > 0) {
73 ret = 0;
74 goto out;
75 }
76 btrfs_release_path(path);
77 /*
78 * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
79 * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
80 * a deadlock (attempting to write lock an already write locked leaf).
81 */
82 path->lowest_level = 1;
83 wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
84
85 if (wret < 0) {
86 ret = wret;
87 goto out;
88 }
89 if (!path->nodes[1]) {
90 ret = 0;
91 goto out;
92 }
93 /*
94 * The node at level 1 must always be locked when our path has
95 * keep_locks set and lowest_level is 1, regardless of the value of
96 * path->slots[1].
97 */
98 BUG_ON(path->locks[1] == 0);
99 ret = btrfs_realloc_node(trans, root,
100 path->nodes[1], 0,
101 &last_ret,
102 &root->defrag_progress);
103 if (ret) {
104 WARN_ON(ret == -EAGAIN);
105 goto out;
106 }
107 /*
108 * Now that we reallocated the node we can find the next key. Note that
109 * btrfs_find_next_key() can release our path and do another search
110 * without COWing, this is because even with path->keep_locks = 1,
111 * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
112 * node when path->slots[node_level - 1] does not point to the last
113 * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
114 * we search for the next key after reallocating our node.
115 */
116 path->slots[1] = btrfs_header_nritems(path->nodes[1]);
117 next_key_ret = btrfs_find_next_key(root, path, &key, 1,
118 BTRFS_OLDEST_GENERATION);
119 if (next_key_ret == 0) {
120 memcpy(&root->defrag_progress, &key, sizeof(key));
121 ret = -EAGAIN;
122 }
123 out:
124 btrfs_free_path(path);
125 if (ret == -EAGAIN) {
126 if (root->defrag_max.objectid > root->defrag_progress.objectid)
127 goto done;
128 if (root->defrag_max.type > root->defrag_progress.type)
129 goto done;
130 if (root->defrag_max.offset > root->defrag_progress.offset)
131 goto done;
132 ret = 0;
133 }
134 done:
135 if (ret != -EAGAIN)
136 memset(&root->defrag_progress, 0,
137 sizeof(root->defrag_progress));
138
139 return ret;
140 }
141