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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 | * | |
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 | */ | |
925baedd CM |
37 | int btrfs_tree_lock(struct extent_buffer *eb) |
38 | { | |
f9efa9c7 CM |
39 | int i; |
40 | ||
a61e6f29 | 41 | if (mutex_trylock(&eb->mutex)) |
f9efa9c7 CM |
42 | return 0; |
43 | for (i = 0; i < 512; i++) { | |
44 | cpu_relax(); | |
a61e6f29 | 45 | if (mutex_trylock(&eb->mutex)) |
f9efa9c7 CM |
46 | return 0; |
47 | } | |
48 | cpu_relax(); | |
6dddcbeb | 49 | mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb)); |
925baedd CM |
50 | return 0; |
51 | } | |
52 | ||
53 | int btrfs_try_tree_lock(struct extent_buffer *eb) | |
54 | { | |
a61e6f29 | 55 | return mutex_trylock(&eb->mutex); |
925baedd CM |
56 | } |
57 | ||
58 | int btrfs_tree_unlock(struct extent_buffer *eb) | |
59 | { | |
a61e6f29 | 60 | mutex_unlock(&eb->mutex); |
925baedd CM |
61 | return 0; |
62 | } | |
63 | ||
64 | int btrfs_tree_locked(struct extent_buffer *eb) | |
65 | { | |
a61e6f29 | 66 | return mutex_is_locked(&eb->mutex); |
925baedd | 67 | } |
65b51a00 | 68 | |
d352ac68 CM |
69 | /* |
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 | */ | |
65b51a00 CM |
73 | int 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 |