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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> | |
925baedd CM |
19 | #include <linux/pagemap.h> |
20 | #include <linux/spinlock.h> | |
21 | #include <linux/page-flags.h> | |
4881ee5a | 22 | #include <asm/bug.h> |
925baedd CM |
23 | #include "ctree.h" |
24 | #include "extent_io.h" | |
25 | #include "locking.h" | |
26 | ||
bd681513 | 27 | void btrfs_assert_tree_read_locked(struct extent_buffer *eb); |
d397712b | 28 | |
b4ce94de | 29 | /* |
bd681513 CM |
30 | * if we currently have a spinning reader or writer lock |
31 | * (indicated by the rw flag) this will bump the count | |
32 | * of blocking holders and drop the spinlock. | |
b4ce94de | 33 | */ |
bd681513 | 34 | void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw) |
925baedd | 35 | { |
bd681513 CM |
36 | if (rw == BTRFS_WRITE_LOCK) { |
37 | if (atomic_read(&eb->blocking_writers) == 0) { | |
38 | WARN_ON(atomic_read(&eb->spinning_writers) != 1); | |
39 | atomic_dec(&eb->spinning_writers); | |
40 | btrfs_assert_tree_locked(eb); | |
41 | atomic_inc(&eb->blocking_writers); | |
42 | write_unlock(&eb->lock); | |
43 | } | |
44 | } else if (rw == BTRFS_READ_LOCK) { | |
45 | btrfs_assert_tree_read_locked(eb); | |
46 | atomic_inc(&eb->blocking_readers); | |
47 | WARN_ON(atomic_read(&eb->spinning_readers) == 0); | |
48 | atomic_dec(&eb->spinning_readers); | |
49 | read_unlock(&eb->lock); | |
b4ce94de | 50 | } |
bd681513 | 51 | return; |
b4ce94de | 52 | } |
f9efa9c7 | 53 | |
b4ce94de | 54 | /* |
bd681513 CM |
55 | * if we currently have a blocking lock, take the spinlock |
56 | * and drop our blocking count | |
b4ce94de | 57 | */ |
bd681513 | 58 | void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw) |
b4ce94de | 59 | { |
bd681513 CM |
60 | if (rw == BTRFS_WRITE_LOCK_BLOCKING) { |
61 | BUG_ON(atomic_read(&eb->blocking_writers) != 1); | |
62 | write_lock(&eb->lock); | |
63 | WARN_ON(atomic_read(&eb->spinning_writers)); | |
64 | atomic_inc(&eb->spinning_writers); | |
65 | if (atomic_dec_and_test(&eb->blocking_writers)) | |
66 | wake_up(&eb->write_lock_wq); | |
67 | } else if (rw == BTRFS_READ_LOCK_BLOCKING) { | |
68 | BUG_ON(atomic_read(&eb->blocking_readers) == 0); | |
69 | read_lock(&eb->lock); | |
70 | atomic_inc(&eb->spinning_readers); | |
71 | if (atomic_dec_and_test(&eb->blocking_readers)) | |
72 | wake_up(&eb->read_lock_wq); | |
b4ce94de | 73 | } |
bd681513 | 74 | return; |
b4ce94de CM |
75 | } |
76 | ||
77 | /* | |
bd681513 CM |
78 | * take a spinning read lock. This will wait for any blocking |
79 | * writers | |
b4ce94de | 80 | */ |
bd681513 | 81 | void btrfs_tree_read_lock(struct extent_buffer *eb) |
b4ce94de | 82 | { |
bd681513 CM |
83 | again: |
84 | wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0); | |
85 | read_lock(&eb->lock); | |
86 | if (atomic_read(&eb->blocking_writers)) { | |
87 | read_unlock(&eb->lock); | |
88 | wait_event(eb->write_lock_wq, | |
89 | atomic_read(&eb->blocking_writers) == 0); | |
90 | goto again; | |
b4ce94de | 91 | } |
bd681513 CM |
92 | atomic_inc(&eb->read_locks); |
93 | atomic_inc(&eb->spinning_readers); | |
b4ce94de CM |
94 | } |
95 | ||
96 | /* | |
bd681513 CM |
97 | * returns 1 if we get the read lock and 0 if we don't |
98 | * this won't wait for blocking writers | |
b4ce94de | 99 | */ |
bd681513 | 100 | int btrfs_try_tree_read_lock(struct extent_buffer *eb) |
b4ce94de | 101 | { |
bd681513 CM |
102 | if (atomic_read(&eb->blocking_writers)) |
103 | return 0; | |
b4ce94de | 104 | |
bd681513 CM |
105 | read_lock(&eb->lock); |
106 | if (atomic_read(&eb->blocking_writers)) { | |
107 | read_unlock(&eb->lock); | |
108 | return 0; | |
b9473439 | 109 | } |
bd681513 CM |
110 | atomic_inc(&eb->read_locks); |
111 | atomic_inc(&eb->spinning_readers); | |
112 | return 1; | |
b4ce94de CM |
113 | } |
114 | ||
115 | /* | |
bd681513 CM |
116 | * returns 1 if we get the read lock and 0 if we don't |
117 | * this won't wait for blocking writers or readers | |
b4ce94de | 118 | */ |
bd681513 | 119 | int btrfs_try_tree_write_lock(struct extent_buffer *eb) |
b4ce94de | 120 | { |
bd681513 CM |
121 | if (atomic_read(&eb->blocking_writers) || |
122 | atomic_read(&eb->blocking_readers)) | |
123 | return 0; | |
124 | write_lock(&eb->lock); | |
125 | if (atomic_read(&eb->blocking_writers) || | |
126 | atomic_read(&eb->blocking_readers)) { | |
127 | write_unlock(&eb->lock); | |
128 | return 0; | |
129 | } | |
130 | atomic_inc(&eb->write_locks); | |
131 | atomic_inc(&eb->spinning_writers); | |
b4ce94de CM |
132 | return 1; |
133 | } | |
134 | ||
135 | /* | |
bd681513 CM |
136 | * drop a spinning read lock |
137 | */ | |
138 | void btrfs_tree_read_unlock(struct extent_buffer *eb) | |
139 | { | |
140 | btrfs_assert_tree_read_locked(eb); | |
141 | WARN_ON(atomic_read(&eb->spinning_readers) == 0); | |
142 | atomic_dec(&eb->spinning_readers); | |
143 | atomic_dec(&eb->read_locks); | |
144 | read_unlock(&eb->lock); | |
145 | } | |
146 | ||
147 | /* | |
148 | * drop a blocking read lock | |
149 | */ | |
150 | void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb) | |
151 | { | |
152 | btrfs_assert_tree_read_locked(eb); | |
153 | WARN_ON(atomic_read(&eb->blocking_readers) == 0); | |
154 | if (atomic_dec_and_test(&eb->blocking_readers)) | |
155 | wake_up(&eb->read_lock_wq); | |
156 | atomic_dec(&eb->read_locks); | |
157 | } | |
158 | ||
159 | /* | |
160 | * take a spinning write lock. This will wait for both | |
161 | * blocking readers or writers | |
b4ce94de CM |
162 | */ |
163 | int btrfs_tree_lock(struct extent_buffer *eb) | |
164 | { | |
bd681513 CM |
165 | again: |
166 | wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0); | |
167 | wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0); | |
168 | write_lock(&eb->lock); | |
169 | if (atomic_read(&eb->blocking_readers)) { | |
170 | write_unlock(&eb->lock); | |
171 | wait_event(eb->read_lock_wq, | |
172 | atomic_read(&eb->blocking_readers) == 0); | |
173 | goto again; | |
f9efa9c7 | 174 | } |
bd681513 CM |
175 | if (atomic_read(&eb->blocking_writers)) { |
176 | write_unlock(&eb->lock); | |
177 | wait_event(eb->write_lock_wq, | |
178 | atomic_read(&eb->blocking_writers) == 0); | |
179 | goto again; | |
180 | } | |
181 | WARN_ON(atomic_read(&eb->spinning_writers)); | |
182 | atomic_inc(&eb->spinning_writers); | |
183 | atomic_inc(&eb->write_locks); | |
925baedd CM |
184 | return 0; |
185 | } | |
186 | ||
bd681513 CM |
187 | /* |
188 | * drop a spinning or a blocking write lock. | |
189 | */ | |
925baedd CM |
190 | int btrfs_tree_unlock(struct extent_buffer *eb) |
191 | { | |
bd681513 CM |
192 | int blockers = atomic_read(&eb->blocking_writers); |
193 | ||
194 | BUG_ON(blockers > 1); | |
195 | ||
196 | btrfs_assert_tree_locked(eb); | |
197 | atomic_dec(&eb->write_locks); | |
198 | ||
199 | if (blockers) { | |
200 | WARN_ON(atomic_read(&eb->spinning_writers)); | |
201 | atomic_dec(&eb->blocking_writers); | |
202 | smp_wmb(); | |
203 | wake_up(&eb->write_lock_wq); | |
204 | } else { | |
205 | WARN_ON(atomic_read(&eb->spinning_writers) != 1); | |
206 | atomic_dec(&eb->spinning_writers); | |
207 | write_unlock(&eb->lock); | |
208 | } | |
925baedd CM |
209 | return 0; |
210 | } | |
211 | ||
b9447ef8 | 212 | void btrfs_assert_tree_locked(struct extent_buffer *eb) |
925baedd | 213 | { |
bd681513 CM |
214 | BUG_ON(!atomic_read(&eb->write_locks)); |
215 | } | |
216 | ||
217 | void btrfs_assert_tree_read_locked(struct extent_buffer *eb) | |
218 | { | |
219 | BUG_ON(!atomic_read(&eb->read_locks)); | |
925baedd | 220 | } |