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 (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
31 goto out;
32
33 path = btrfs_alloc_path();
34 if (!path)
35 return -ENOMEM;
36
37 level = btrfs_header_level(root->node);
38
39 if (level == 0)
40 goto out;
41
42 if (root->defrag_progress.objectid == 0) {
43 struct extent_buffer *root_node;
44 u32 nritems;
45
46 root_node = btrfs_lock_root_node(root);
47 nritems = btrfs_header_nritems(root_node);
48 root->defrag_max.objectid = 0;
49 /* from above we know this is not a leaf */
50 btrfs_node_key_to_cpu(root_node, &root->defrag_max,
51 nritems - 1);
52 btrfs_tree_unlock(root_node);
53 free_extent_buffer(root_node);
54 memset(&key, 0, sizeof(key));
55 } else {
56 memcpy(&key, &root->defrag_progress, sizeof(key));
57 }
58
59 path->keep_locks = 1;
60
61 ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
62 if (ret < 0)
63 goto out;
64 if (ret > 0) {
65 ret = 0;
66 goto out;
67 }
68 btrfs_release_path(path);
69 /*
70 * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
71 * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
72 * a deadlock (attempting to write lock an already write locked leaf).
73 */
74 path->lowest_level = 1;
75 wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
76
77 if (wret < 0) {
78 ret = wret;
79 goto out;
80 }
81 if (!path->nodes[1]) {
82 ret = 0;
83 goto out;
84 }
85 /*
86 * The node at level 1 must always be locked when our path has
87 * keep_locks set and lowest_level is 1, regardless of the value of
88 * path->slots[1].
89 */
90 BUG_ON(path->locks[1] == 0);
91 ret = btrfs_realloc_node(trans, root,
92 path->nodes[1], 0,
93 &last_ret,
94 &root->defrag_progress);
95 if (ret) {
96 WARN_ON(ret == -EAGAIN);
97 goto out;
98 }
99 /*
100 * Now that we reallocated the node we can find the next key. Note that
101 * btrfs_find_next_key() can release our path and do another search
102 * without COWing, this is because even with path->keep_locks = 1,
103 * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
104 * node when path->slots[node_level - 1] does not point to the last
105 * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
106 * we search for the next key after reallocating our node.
107 */
108 path->slots[1] = btrfs_header_nritems(path->nodes[1]);
109 next_key_ret = btrfs_find_next_key(root, path, &key, 1,
110 BTRFS_OLDEST_GENERATION);
111 if (next_key_ret == 0) {
112 memcpy(&root->defrag_progress, &key, sizeof(key));
113 ret = -EAGAIN;
114 }
115 out:
116 btrfs_free_path(path);
117 if (ret == -EAGAIN) {
118 if (root->defrag_max.objectid > root->defrag_progress.objectid)
119 goto done;
120 if (root->defrag_max.type > root->defrag_progress.type)
121 goto done;
122 if (root->defrag_max.offset > root->defrag_progress.offset)
123 goto done;
124 ret = 0;
125 }
126 done:
127 if (ret != -EAGAIN)
128 memset(&root->defrag_progress, 0,
129 sizeof(root->defrag_progress));
130
131 return ret;
132 }
133