blob: e30aa6e2958fee23b12553764f78cac4b993ebb1 [file] [log] [blame]
Chris Mason925baed2008-06-25 16:01:30 -04001/*
2 * Copyright (C) 2008 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#include <linux/sched.h>
19#include <linux/gfp.h>
20#include <linux/pagemap.h>
21#include <linux/spinlock.h>
22#include <linux/page-flags.h>
Chris Mason4881ee52008-07-24 09:51:08 -040023#include <asm/bug.h>
Chris Mason925baed2008-06-25 16:01:30 -040024#include "ctree.h"
25#include "extent_io.h"
26#include "locking.h"
27
Chris Masond352ac62008-09-29 15:18:18 -040028/*
29 * locks the per buffer mutex in an extent buffer. This uses adaptive locks
30 * and the spin is not tuned very extensively. The spinning does make a big
31 * difference in almost every workload, but spinning for the right amount of
32 * time needs some help.
33 *
34 * In general, we want to spin as long as the lock holder is doing btree searches,
35 * and we should give up if they are in more expensive code.
36 */
Chris Mason925baed2008-06-25 16:01:30 -040037int btrfs_tree_lock(struct extent_buffer *eb)
38{
Chris Masonf9efa9c2008-06-25 16:14:04 -040039 int i;
40
Chris Masona61e6f22008-07-22 11:18:08 -040041 if (mutex_trylock(&eb->mutex))
Chris Masonf9efa9c2008-06-25 16:14:04 -040042 return 0;
43 for (i = 0; i < 512; i++) {
44 cpu_relax();
Chris Masona61e6f22008-07-22 11:18:08 -040045 if (mutex_trylock(&eb->mutex))
Chris Masonf9efa9c2008-06-25 16:14:04 -040046 return 0;
47 }
48 cpu_relax();
Chris Mason6dddcbe2008-07-22 11:18:09 -040049 mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
Chris Mason925baed2008-06-25 16:01:30 -040050 return 0;
51}
52
53int btrfs_try_tree_lock(struct extent_buffer *eb)
54{
Chris Masona61e6f22008-07-22 11:18:08 -040055 return mutex_trylock(&eb->mutex);
Chris Mason925baed2008-06-25 16:01:30 -040056}
57
58int btrfs_tree_unlock(struct extent_buffer *eb)
59{
Chris Masona61e6f22008-07-22 11:18:08 -040060 mutex_unlock(&eb->mutex);
Chris Mason925baed2008-06-25 16:01:30 -040061 return 0;
62}
63
64int btrfs_tree_locked(struct extent_buffer *eb)
65{
Chris Masona61e6f22008-07-22 11:18:08 -040066 return mutex_is_locked(&eb->mutex);
Chris Mason925baed2008-06-25 16:01:30 -040067}
Chris Mason65b51a02008-08-01 15:11:20 -040068
Chris Masond352ac62008-09-29 15:18:18 -040069/*
70 * btrfs_search_slot uses this to decide if it should drop its locks
71 * before doing something expensive like allocating free blocks for cow.
72 */
Chris Mason65b51a02008-08-01 15:11:20 -040073int btrfs_path_lock_waiting(struct btrfs_path *path, int level)
74{
75 int i;
76 struct extent_buffer *eb;
77 for (i = level; i <= level + 1 && i < BTRFS_MAX_LEVEL; i++) {
78 eb = path->nodes[i];
79 if (!eb)
80 break;
81 smp_mb();
82 if (!list_empty(&eb->mutex.wait_list))
83 return 1;
84 }
85 return 0;
86}
87