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925baedd CM |
1 | /* |
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> | |
4881ee5a | 23 | #include <asm/bug.h> |
925baedd CM |
24 | #include "ctree.h" |
25 | #include "extent_io.h" | |
26 | #include "locking.h" | |
27 | ||
d352ac68 CM |
28 | /* |
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 | * | |
d397712b CM |
34 | * In general, we want to spin as long as the lock holder is doing btree |
35 | * searches, and we should give up if they are in more expensive code. | |
d352ac68 | 36 | */ |
d397712b | 37 | |
925baedd CM |
38 | int btrfs_tree_lock(struct extent_buffer *eb) |
39 | { | |
f9efa9c7 CM |
40 | int i; |
41 | ||
a61e6f29 | 42 | if (mutex_trylock(&eb->mutex)) |
f9efa9c7 CM |
43 | return 0; |
44 | for (i = 0; i < 512; i++) { | |
45 | cpu_relax(); | |
a61e6f29 | 46 | if (mutex_trylock(&eb->mutex)) |
f9efa9c7 CM |
47 | return 0; |
48 | } | |
49 | cpu_relax(); | |
6dddcbeb | 50 | mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb)); |
925baedd CM |
51 | return 0; |
52 | } | |
53 | ||
54 | int btrfs_try_tree_lock(struct extent_buffer *eb) | |
55 | { | |
a61e6f29 | 56 | return mutex_trylock(&eb->mutex); |
925baedd CM |
57 | } |
58 | ||
59 | int btrfs_tree_unlock(struct extent_buffer *eb) | |
60 | { | |
a61e6f29 | 61 | mutex_unlock(&eb->mutex); |
925baedd CM |
62 | return 0; |
63 | } | |
64 | ||
65 | int btrfs_tree_locked(struct extent_buffer *eb) | |
66 | { | |
a61e6f29 | 67 | return mutex_is_locked(&eb->mutex); |
925baedd | 68 | } |
65b51a00 | 69 | |
d352ac68 CM |
70 | /* |
71 | * btrfs_search_slot uses this to decide if it should drop its locks | |
72 | * before doing something expensive like allocating free blocks for cow. | |
73 | */ | |
65b51a00 CM |
74 | int btrfs_path_lock_waiting(struct btrfs_path *path, int level) |
75 | { | |
76 | int i; | |
77 | struct extent_buffer *eb; | |
78 | for (i = level; i <= level + 1 && i < BTRFS_MAX_LEVEL; i++) { | |
79 | eb = path->nodes[i]; | |
80 | if (!eb) | |
81 | break; | |
82 | smp_mb(); | |
83 | if (!list_empty(&eb->mutex.wait_list)) | |
84 | return 1; | |
85 | } | |
86 | return 0; | |
87 | } | |
88 |