blob: 5e178d8f7167f496e928613b6c1f0000c2ea242e [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);
70 if (&eb->lock_nested && current->pid == eb->lock_owner) {
71 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);
81 if (atomic_dec_and_test(&eb->blocking_writers))
82 wake_up(&eb->write_lock_wq);
83 } else if (rw == BTRFS_READ_LOCK_BLOCKING) {
84 BUG_ON(atomic_read(&eb->blocking_readers) == 0);
85 read_lock(&eb->lock);
86 atomic_inc(&eb->spinning_readers);
87 if (atomic_dec_and_test(&eb->blocking_readers))
88 wake_up(&eb->read_lock_wq);
Chris Masonb4ce94d2009-02-04 09:25:08 -050089 }
Chris Masonbd681512011-07-16 15:23:14 -040090 return;
Chris Masonb4ce94d2009-02-04 09:25:08 -050091}
92
93/*
Chris Masonbd681512011-07-16 15:23:14 -040094 * take a spinning read lock. This will wait for any blocking
95 * writers
Chris Masonb4ce94d2009-02-04 09:25:08 -050096 */
Chris Masonbd681512011-07-16 15:23:14 -040097void btrfs_tree_read_lock(struct extent_buffer *eb)
Chris Masonb4ce94d2009-02-04 09:25:08 -050098{
Chris Masonbd681512011-07-16 15:23:14 -040099again:
Arne Jansen5b25f702011-09-13 10:55:48 +0200100 read_lock(&eb->lock);
101 if (atomic_read(&eb->blocking_writers) &&
102 current->pid == eb->lock_owner) {
103 /*
104 * This extent is already write-locked by our thread. We allow
105 * an additional read lock to be added because it's for the same
106 * thread. btrfs_find_all_roots() depends on this as it may be
107 * called on a partly (write-)locked tree.
108 */
109 BUG_ON(eb->lock_nested);
110 eb->lock_nested = 1;
111 read_unlock(&eb->lock);
112 return;
113 }
114 read_unlock(&eb->lock);
Chris Masonbd681512011-07-16 15:23:14 -0400115 wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
116 read_lock(&eb->lock);
117 if (atomic_read(&eb->blocking_writers)) {
118 read_unlock(&eb->lock);
Chris Masonbd681512011-07-16 15:23:14 -0400119 goto again;
Chris Masonb4ce94d2009-02-04 09:25:08 -0500120 }
Chris Masonbd681512011-07-16 15:23:14 -0400121 atomic_inc(&eb->read_locks);
122 atomic_inc(&eb->spinning_readers);
Chris Masonb4ce94d2009-02-04 09:25:08 -0500123}
124
125/*
Chris Masonbd681512011-07-16 15:23:14 -0400126 * returns 1 if we get the read lock and 0 if we don't
127 * this won't wait for blocking writers
Chris Masonb4ce94d2009-02-04 09:25:08 -0500128 */
Chris Masonbd681512011-07-16 15:23:14 -0400129int btrfs_try_tree_read_lock(struct extent_buffer *eb)
Chris Mason925baed2008-06-25 16:01:30 -0400130{
Chris Masonbd681512011-07-16 15:23:14 -0400131 if (atomic_read(&eb->blocking_writers))
132 return 0;
Chris Mason66d7e852009-03-12 20:12:45 -0400133
Chris Masonbd681512011-07-16 15:23:14 -0400134 read_lock(&eb->lock);
135 if (atomic_read(&eb->blocking_writers)) {
136 read_unlock(&eb->lock);
137 return 0;
Chris Masonf9efa9c2008-06-25 16:14:04 -0400138 }
Chris Masonbd681512011-07-16 15:23:14 -0400139 atomic_inc(&eb->read_locks);
140 atomic_inc(&eb->spinning_readers);
Chris Masonb4ce94d2009-02-04 09:25:08 -0500141 return 1;
142}
143
144/*
Chris Masonbd681512011-07-16 15:23:14 -0400145 * returns 1 if we get the read lock and 0 if we don't
146 * this won't wait for blocking writers or readers
147 */
148int btrfs_try_tree_write_lock(struct extent_buffer *eb)
149{
150 if (atomic_read(&eb->blocking_writers) ||
151 atomic_read(&eb->blocking_readers))
152 return 0;
153 write_lock(&eb->lock);
154 if (atomic_read(&eb->blocking_writers) ||
155 atomic_read(&eb->blocking_readers)) {
156 write_unlock(&eb->lock);
157 return 0;
158 }
159 atomic_inc(&eb->write_locks);
160 atomic_inc(&eb->spinning_writers);
Arne Jansen5b25f702011-09-13 10:55:48 +0200161 eb->lock_owner = current->pid;
Chris Masonbd681512011-07-16 15:23:14 -0400162 return 1;
163}
164
165/*
166 * drop a spinning read lock
167 */
168void btrfs_tree_read_unlock(struct extent_buffer *eb)
169{
Arne Jansen5b25f702011-09-13 10:55:48 +0200170 if (eb->lock_nested) {
171 read_lock(&eb->lock);
172 if (eb->lock_nested && current->pid == eb->lock_owner) {
173 eb->lock_nested = 0;
174 read_unlock(&eb->lock);
175 return;
176 }
177 read_unlock(&eb->lock);
178 }
Chris Masonbd681512011-07-16 15:23:14 -0400179 btrfs_assert_tree_read_locked(eb);
180 WARN_ON(atomic_read(&eb->spinning_readers) == 0);
181 atomic_dec(&eb->spinning_readers);
182 atomic_dec(&eb->read_locks);
183 read_unlock(&eb->lock);
184}
185
186/*
187 * drop a blocking read lock
188 */
189void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
190{
Arne Jansen5b25f702011-09-13 10:55:48 +0200191 if (eb->lock_nested) {
192 read_lock(&eb->lock);
193 if (eb->lock_nested && current->pid == eb->lock_owner) {
194 eb->lock_nested = 0;
195 read_unlock(&eb->lock);
196 return;
197 }
198 read_unlock(&eb->lock);
199 }
Chris Masonbd681512011-07-16 15:23:14 -0400200 btrfs_assert_tree_read_locked(eb);
201 WARN_ON(atomic_read(&eb->blocking_readers) == 0);
202 if (atomic_dec_and_test(&eb->blocking_readers))
203 wake_up(&eb->read_lock_wq);
204 atomic_dec(&eb->read_locks);
205}
206
207/*
208 * take a spinning write lock. This will wait for both
209 * blocking readers or writers
Chris Masonb4ce94d2009-02-04 09:25:08 -0500210 */
211int btrfs_tree_lock(struct extent_buffer *eb)
212{
Chris Masonbd681512011-07-16 15:23:14 -0400213again:
214 wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
215 wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
216 write_lock(&eb->lock);
217 if (atomic_read(&eb->blocking_readers)) {
218 write_unlock(&eb->lock);
219 wait_event(eb->read_lock_wq,
220 atomic_read(&eb->blocking_readers) == 0);
221 goto again;
Chris Masonb4ce94d2009-02-04 09:25:08 -0500222 }
Chris Masonbd681512011-07-16 15:23:14 -0400223 if (atomic_read(&eb->blocking_writers)) {
224 write_unlock(&eb->lock);
225 wait_event(eb->write_lock_wq,
226 atomic_read(&eb->blocking_writers) == 0);
227 goto again;
228 }
229 WARN_ON(atomic_read(&eb->spinning_writers));
230 atomic_inc(&eb->spinning_writers);
231 atomic_inc(&eb->write_locks);
Arne Jansen5b25f702011-09-13 10:55:48 +0200232 eb->lock_owner = current->pid;
Chris Masonb4ce94d2009-02-04 09:25:08 -0500233 return 0;
234}
235
Chris Masonbd681512011-07-16 15:23:14 -0400236/*
237 * drop a spinning or a blocking write lock.
238 */
Chris Mason925baed2008-06-25 16:01:30 -0400239int btrfs_tree_unlock(struct extent_buffer *eb)
240{
Chris Masonbd681512011-07-16 15:23:14 -0400241 int blockers = atomic_read(&eb->blocking_writers);
Chris Masonb4ce94d2009-02-04 09:25:08 -0500242
Chris Masonbd681512011-07-16 15:23:14 -0400243 BUG_ON(blockers > 1);
244
245 btrfs_assert_tree_locked(eb);
246 atomic_dec(&eb->write_locks);
247
248 if (blockers) {
249 WARN_ON(atomic_read(&eb->spinning_writers));
250 atomic_dec(&eb->blocking_writers);
251 smp_wmb();
252 wake_up(&eb->write_lock_wq);
253 } else {
254 WARN_ON(atomic_read(&eb->spinning_writers) != 1);
255 atomic_dec(&eb->spinning_writers);
256 write_unlock(&eb->lock);
257 }
Chris Mason925baed2008-06-25 16:01:30 -0400258 return 0;
259}
260
Chris Masonb9447ef2009-03-09 11:45:38 -0400261void btrfs_assert_tree_locked(struct extent_buffer *eb)
Chris Mason925baed2008-06-25 16:01:30 -0400262{
Chris Masonbd681512011-07-16 15:23:14 -0400263 BUG_ON(!atomic_read(&eb->write_locks));
264}
265
266void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
267{
268 BUG_ON(!atomic_read(&eb->read_locks));
Chris Mason925baed2008-06-25 16:01:30 -0400269}