blob: e95df435d8976606730bb04faa3e7ceb2a87917c [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>
Chris Mason925baed2008-06-25 16:01:30 -040019#include <linux/pagemap.h>
20#include <linux/spinlock.h>
21#include <linux/page-flags.h>
Chris Mason4881ee52008-07-24 09:51:08 -040022#include <asm/bug.h>
Chris Mason925baed2008-06-25 16:01:30 -040023#include "ctree.h"
24#include "extent_io.h"
25#include "locking.h"
26
Chris Masonbd681512011-07-16 15:23:14 -040027void btrfs_assert_tree_read_locked(struct extent_buffer *eb);
28
29/*
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.
33 */
34void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw)
Chris Masonb4ce94d2009-02-04 09:25:08 -050035{
Arne Jansen5b25f702011-09-13 10:55:48 +020036 if (eb->lock_nested) {
37 read_lock(&eb->lock);
38 if (eb->lock_nested && current->pid == eb->lock_owner) {
39 read_unlock(&eb->lock);
40 return;
41 }
42 read_unlock(&eb->lock);
43 }
Chris Masonbd681512011-07-16 15:23:14 -040044 if (rw == BTRFS_WRITE_LOCK) {
45 if (atomic_read(&eb->blocking_writers) == 0) {
46 WARN_ON(atomic_read(&eb->spinning_writers) != 1);
47 atomic_dec(&eb->spinning_writers);
48 btrfs_assert_tree_locked(eb);
49 atomic_inc(&eb->blocking_writers);
50 write_unlock(&eb->lock);
51 }
52 } else if (rw == BTRFS_READ_LOCK) {
53 btrfs_assert_tree_read_locked(eb);
54 atomic_inc(&eb->blocking_readers);
55 WARN_ON(atomic_read(&eb->spinning_readers) == 0);
56 atomic_dec(&eb->spinning_readers);
57 read_unlock(&eb->lock);
58 }
59 return;
Chris Masonb4ce94d2009-02-04 09:25:08 -050060}
Chris Masond3977122009-01-05 21:25:51 -050061
Chris Masonb4ce94d2009-02-04 09:25:08 -050062/*
Chris Masonbd681512011-07-16 15:23:14 -040063 * if we currently have a blocking lock, take the spinlock
64 * and drop our blocking count
Chris Masonb4ce94d2009-02-04 09:25:08 -050065 */
Chris Masonbd681512011-07-16 15:23:14 -040066void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
Chris Masonb4ce94d2009-02-04 09:25:08 -050067{
Arne Jansen5b25f702011-09-13 10:55:48 +020068 if (eb->lock_nested) {
69 read_lock(&eb->lock);
Stefan Behrensaa2ffd02012-07-26 03:40:35 -060070 if (eb->lock_nested && current->pid == eb->lock_owner) {
Arne Jansen5b25f702011-09-13 10:55:48 +020071 read_unlock(&eb->lock);
72 return;
73 }
74 read_unlock(&eb->lock);
75 }
Chris Masonbd681512011-07-16 15:23:14 -040076 if (rw == BTRFS_WRITE_LOCK_BLOCKING) {
77 BUG_ON(atomic_read(&eb->blocking_writers) != 1);
78 write_lock(&eb->lock);
79 WARN_ON(atomic_read(&eb->spinning_writers));
80 atomic_inc(&eb->spinning_writers);
Chris Masoncbea5ac2012-07-23 15:25:05 -040081 if (atomic_dec_and_test(&eb->blocking_writers) &&
82 waitqueue_active(&eb->write_lock_wq))
Chris Masonbd681512011-07-16 15:23:14 -040083 wake_up(&eb->write_lock_wq);
84 } else if (rw == BTRFS_READ_LOCK_BLOCKING) {
85 BUG_ON(atomic_read(&eb->blocking_readers) == 0);
86 read_lock(&eb->lock);
87 atomic_inc(&eb->spinning_readers);
Chris Masoncbea5ac2012-07-23 15:25:05 -040088 if (atomic_dec_and_test(&eb->blocking_readers) &&
89 waitqueue_active(&eb->read_lock_wq))
Chris Masonbd681512011-07-16 15:23:14 -040090 wake_up(&eb->read_lock_wq);
Chris Masonb4ce94d2009-02-04 09:25:08 -050091 }
Chris Masonbd681512011-07-16 15:23:14 -040092 return;
Chris Masonb4ce94d2009-02-04 09:25:08 -050093}
94
95/*
Chris Masonbd681512011-07-16 15:23:14 -040096 * take a spinning read lock. This will wait for any blocking
97 * writers
Chris Masonb4ce94d2009-02-04 09:25:08 -050098 */
Chris Masonbd681512011-07-16 15:23:14 -040099void btrfs_tree_read_lock(struct extent_buffer *eb)
Chris Masonb4ce94d2009-02-04 09:25:08 -0500100{
Chris Masonbd681512011-07-16 15:23:14 -0400101again:
Arne Jansen5b25f702011-09-13 10:55:48 +0200102 read_lock(&eb->lock);
103 if (atomic_read(&eb->blocking_writers) &&
104 current->pid == eb->lock_owner) {
105 /*
106 * This extent is already write-locked by our thread. We allow
107 * an additional read lock to be added because it's for the same
108 * thread. btrfs_find_all_roots() depends on this as it may be
109 * called on a partly (write-)locked tree.
110 */
111 BUG_ON(eb->lock_nested);
112 eb->lock_nested = 1;
113 read_unlock(&eb->lock);
114 return;
115 }
Chris Masonbd681512011-07-16 15:23:14 -0400116 if (atomic_read(&eb->blocking_writers)) {
117 read_unlock(&eb->lock);
Liu Bo39f9d022012-12-27 09:01:22 +0000118 wait_event(eb->write_lock_wq,
119 atomic_read(&eb->blocking_writers) == 0);
Chris Masonbd681512011-07-16 15:23:14 -0400120 goto again;
Chris Masonb4ce94d2009-02-04 09:25:08 -0500121 }
Chris Masonbd681512011-07-16 15:23:14 -0400122 atomic_inc(&eb->read_locks);
123 atomic_inc(&eb->spinning_readers);
Chris Masonb4ce94d2009-02-04 09:25:08 -0500124}
125
126/*
Chris Masonbd681512011-07-16 15:23:14 -0400127 * returns 1 if we get the read lock and 0 if we don't
128 * this won't wait for blocking writers
Chris Masonb4ce94d2009-02-04 09:25:08 -0500129 */
Chris Masonbd681512011-07-16 15:23:14 -0400130int btrfs_try_tree_read_lock(struct extent_buffer *eb)
Chris Mason925baed2008-06-25 16:01:30 -0400131{
Chris Masonbd681512011-07-16 15:23:14 -0400132 if (atomic_read(&eb->blocking_writers))
133 return 0;
Chris Mason66d7e852009-03-12 20:12:45 -0400134
Chris Masonbd681512011-07-16 15:23:14 -0400135 read_lock(&eb->lock);
136 if (atomic_read(&eb->blocking_writers)) {
137 read_unlock(&eb->lock);
138 return 0;
Chris Masonf9efa9c2008-06-25 16:14:04 -0400139 }
Chris Masonbd681512011-07-16 15:23:14 -0400140 atomic_inc(&eb->read_locks);
141 atomic_inc(&eb->spinning_readers);
Chris Masonb4ce94d2009-02-04 09:25:08 -0500142 return 1;
143}
144
145/*
Chris Masonbd681512011-07-16 15:23:14 -0400146 * returns 1 if we get the read lock and 0 if we don't
147 * this won't wait for blocking writers or readers
148 */
149int btrfs_try_tree_write_lock(struct extent_buffer *eb)
150{
151 if (atomic_read(&eb->blocking_writers) ||
152 atomic_read(&eb->blocking_readers))
153 return 0;
154 write_lock(&eb->lock);
155 if (atomic_read(&eb->blocking_writers) ||
156 atomic_read(&eb->blocking_readers)) {
157 write_unlock(&eb->lock);
158 return 0;
159 }
160 atomic_inc(&eb->write_locks);
161 atomic_inc(&eb->spinning_writers);
Arne Jansen5b25f702011-09-13 10:55:48 +0200162 eb->lock_owner = current->pid;
Chris Masonbd681512011-07-16 15:23:14 -0400163 return 1;
164}
165
166/*
167 * drop a spinning read lock
168 */
169void btrfs_tree_read_unlock(struct extent_buffer *eb)
170{
Arne Jansen5b25f702011-09-13 10:55:48 +0200171 if (eb->lock_nested) {
172 read_lock(&eb->lock);
173 if (eb->lock_nested && current->pid == eb->lock_owner) {
174 eb->lock_nested = 0;
175 read_unlock(&eb->lock);
176 return;
177 }
178 read_unlock(&eb->lock);
179 }
Chris Masonbd681512011-07-16 15:23:14 -0400180 btrfs_assert_tree_read_locked(eb);
181 WARN_ON(atomic_read(&eb->spinning_readers) == 0);
182 atomic_dec(&eb->spinning_readers);
183 atomic_dec(&eb->read_locks);
184 read_unlock(&eb->lock);
185}
186
187/*
188 * drop a blocking read lock
189 */
190void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
191{
Arne Jansen5b25f702011-09-13 10:55:48 +0200192 if (eb->lock_nested) {
193 read_lock(&eb->lock);
194 if (eb->lock_nested && current->pid == eb->lock_owner) {
195 eb->lock_nested = 0;
196 read_unlock(&eb->lock);
197 return;
198 }
199 read_unlock(&eb->lock);
200 }
Chris Masonbd681512011-07-16 15:23:14 -0400201 btrfs_assert_tree_read_locked(eb);
202 WARN_ON(atomic_read(&eb->blocking_readers) == 0);
Chris Masoncbea5ac2012-07-23 15:25:05 -0400203 if (atomic_dec_and_test(&eb->blocking_readers) &&
204 waitqueue_active(&eb->read_lock_wq))
Chris Masonbd681512011-07-16 15:23:14 -0400205 wake_up(&eb->read_lock_wq);
206 atomic_dec(&eb->read_locks);
207}
208
209/*
210 * take a spinning write lock. This will wait for both
211 * blocking readers or writers
Chris Masonb4ce94d2009-02-04 09:25:08 -0500212 */
Jeff Mahoney143bede2012-03-01 14:56:26 +0100213void btrfs_tree_lock(struct extent_buffer *eb)
Chris Masonb4ce94d2009-02-04 09:25:08 -0500214{
Chris Masonbd681512011-07-16 15:23:14 -0400215again:
216 wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
217 wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
218 write_lock(&eb->lock);
219 if (atomic_read(&eb->blocking_readers)) {
220 write_unlock(&eb->lock);
221 wait_event(eb->read_lock_wq,
222 atomic_read(&eb->blocking_readers) == 0);
223 goto again;
Chris Masonb4ce94d2009-02-04 09:25:08 -0500224 }
Chris Masonbd681512011-07-16 15:23:14 -0400225 if (atomic_read(&eb->blocking_writers)) {
226 write_unlock(&eb->lock);
227 wait_event(eb->write_lock_wq,
228 atomic_read(&eb->blocking_writers) == 0);
229 goto again;
230 }
231 WARN_ON(atomic_read(&eb->spinning_writers));
232 atomic_inc(&eb->spinning_writers);
233 atomic_inc(&eb->write_locks);
Arne Jansen5b25f702011-09-13 10:55:48 +0200234 eb->lock_owner = current->pid;
Chris Masonb4ce94d2009-02-04 09:25:08 -0500235}
236
Chris Masonbd681512011-07-16 15:23:14 -0400237/*
238 * drop a spinning or a blocking write lock.
239 */
Jeff Mahoney143bede2012-03-01 14:56:26 +0100240void btrfs_tree_unlock(struct extent_buffer *eb)
Chris Mason925baed2008-06-25 16:01:30 -0400241{
Chris Masonbd681512011-07-16 15:23:14 -0400242 int blockers = atomic_read(&eb->blocking_writers);
Chris Masonb4ce94d2009-02-04 09:25:08 -0500243
Chris Masonbd681512011-07-16 15:23:14 -0400244 BUG_ON(blockers > 1);
245
246 btrfs_assert_tree_locked(eb);
247 atomic_dec(&eb->write_locks);
248
249 if (blockers) {
250 WARN_ON(atomic_read(&eb->spinning_writers));
251 atomic_dec(&eb->blocking_writers);
Chris Masoncbea5ac2012-07-23 15:25:05 -0400252 smp_mb();
253 if (waitqueue_active(&eb->write_lock_wq))
254 wake_up(&eb->write_lock_wq);
Chris Masonbd681512011-07-16 15:23:14 -0400255 } else {
256 WARN_ON(atomic_read(&eb->spinning_writers) != 1);
257 atomic_dec(&eb->spinning_writers);
258 write_unlock(&eb->lock);
259 }
Chris Mason925baed2008-06-25 16:01:30 -0400260}
261
Chris Masonb9447ef2009-03-09 11:45:38 -0400262void btrfs_assert_tree_locked(struct extent_buffer *eb)
Chris Mason925baed2008-06-25 16:01:30 -0400263{
Chris Masonbd681512011-07-16 15:23:14 -0400264 BUG_ON(!atomic_read(&eb->write_locks));
265}
266
267void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
268{
269 BUG_ON(!atomic_read(&eb->read_locks));
Chris Mason925baed2008-06-25 16:01:30 -0400270}