Btrfs: Allow worker threads to exit when idle
[linux-2.6.git] / fs / btrfs / tree-defrag.c
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 /* defrag all the leaves in a given btree.  If cache_only == 1, don't read
27  * things from disk, otherwise read all the leaves and try to get key order to
28  * better reflect disk order
29  */
30
31 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
32                         struct btrfs_root *root, int cache_only)
33 {
34         struct btrfs_path *path = NULL;
35         struct btrfs_key key;
36         int ret = 0;
37         int wret;
38         int level;
39         int orig_level;
40         int is_extent = 0;
41         int next_key_ret = 0;
42         u64 last_ret = 0;
43         u64 min_trans = 0;
44
45         if (cache_only)
46                 goto out;
47
48         if (root->fs_info->extent_root == root) {
49                 /*
50                  * there's recursion here right now in the tree locking,
51                  * we can't defrag the extent root without deadlock
52                  */
53                 goto out;
54         }
55
56         if (root->ref_cows == 0 && !is_extent)
57                 goto out;
58
59         if (btrfs_test_opt(root, SSD))
60                 goto out;
61
62         path = btrfs_alloc_path();
63         if (!path)
64                 return -ENOMEM;
65
66         level = btrfs_header_level(root->node);
67         orig_level = level;
68
69         if (level == 0)
70                 goto out;
71
72         if (root->defrag_progress.objectid == 0) {
73                 struct extent_buffer *root_node;
74                 u32 nritems;
75
76                 root_node = btrfs_lock_root_node(root);
77                 btrfs_set_lock_blocking(root_node);
78                 nritems = btrfs_header_nritems(root_node);
79                 root->defrag_max.objectid = 0;
80                 /* from above we know this is not a leaf */
81                 btrfs_node_key_to_cpu(root_node, &root->defrag_max,
82                                       nritems - 1);
83                 btrfs_tree_unlock(root_node);
84                 free_extent_buffer(root_node);
85                 memset(&key, 0, sizeof(key));
86         } else {
87                 memcpy(&key, &root->defrag_progress, sizeof(key));
88         }
89
90         path->keep_locks = 1;
91         if (cache_only)
92                 min_trans = root->defrag_trans_start;
93
94         ret = btrfs_search_forward(root, &key, NULL, path,
95                                    cache_only, min_trans);
96         if (ret < 0)
97                 goto out;
98         if (ret > 0) {
99                 ret = 0;
100                 goto out;
101         }
102         btrfs_release_path(root, path);
103         wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
104
105         if (wret < 0) {
106                 ret = wret;
107                 goto out;
108         }
109         if (!path->nodes[1]) {
110                 ret = 0;
111                 goto out;
112         }
113         path->slots[1] = btrfs_header_nritems(path->nodes[1]);
114         next_key_ret = btrfs_find_next_key(root, path, &key, 1, cache_only,
115                                            min_trans);
116         ret = btrfs_realloc_node(trans, root,
117                                  path->nodes[1], 0,
118                                  cache_only, &last_ret,
119                                  &root->defrag_progress);
120         WARN_ON(ret && ret != -EAGAIN);
121         if (next_key_ret == 0) {
122                 memcpy(&root->defrag_progress, &key, sizeof(key));
123                 ret = -EAGAIN;
124         }
125
126         btrfs_release_path(root, path);
127 out:
128         if (path)
129                 btrfs_free_path(path);
130         if (ret == -EAGAIN) {
131                 if (root->defrag_max.objectid > root->defrag_progress.objectid)
132                         goto done;
133                 if (root->defrag_max.type > root->defrag_progress.type)
134                         goto done;
135                 if (root->defrag_max.offset > root->defrag_progress.offset)
136                         goto done;
137                 ret = 0;
138         }
139 done:
140         if (ret != -EAGAIN) {
141                 memset(&root->defrag_progress, 0,
142                        sizeof(root->defrag_progress));
143                 root->defrag_trans_start = trans->transid;
144         }
145         return ret;
146 }