Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 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> |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 19 | #include <linux/pagemap.h> |
| 20 | #include <linux/spinlock.h> |
| 21 | #include <linux/page-flags.h> |
Chris Mason | 4881ee5 | 2008-07-24 09:51:08 -0400 | [diff] [blame] | 22 | #include <asm/bug.h> |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 23 | #include "ctree.h" |
| 24 | #include "extent_io.h" |
| 25 | #include "locking.h" |
| 26 | |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 27 | void 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 | */ |
| 34 | void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw) |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 35 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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); |
| 50 | } |
| 51 | return; |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 52 | } |
Chris Mason | d397712 | 2009-01-05 21:25:51 -0500 | [diff] [blame] | 53 | |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 54 | /* |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 55 | * if we currently have a blocking lock, take the spinlock |
| 56 | * and drop our blocking count |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 57 | */ |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 58 | void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw) |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 59 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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); |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 73 | } |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 74 | return; |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 75 | } |
| 76 | |
| 77 | /* |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 78 | * take a spinning read lock. This will wait for any blocking |
| 79 | * writers |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 80 | */ |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 81 | void btrfs_tree_read_lock(struct extent_buffer *eb) |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 82 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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; |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 91 | } |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 92 | atomic_inc(&eb->read_locks); |
| 93 | atomic_inc(&eb->spinning_readers); |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 94 | } |
| 95 | |
| 96 | /* |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 97 | * returns 1 if we get the read lock and 0 if we don't |
| 98 | * this won't wait for blocking writers |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 99 | */ |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 100 | int btrfs_try_tree_read_lock(struct extent_buffer *eb) |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 101 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 102 | if (atomic_read(&eb->blocking_writers)) |
| 103 | return 0; |
Chris Mason | 66d7e85 | 2009-03-12 20:12:45 -0400 | [diff] [blame] | 104 | |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 105 | read_lock(&eb->lock); |
| 106 | if (atomic_read(&eb->blocking_writers)) { |
| 107 | read_unlock(&eb->lock); |
| 108 | return 0; |
Chris Mason | f9efa9c | 2008-06-25 16:14:04 -0400 | [diff] [blame] | 109 | } |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 110 | atomic_inc(&eb->read_locks); |
| 111 | atomic_inc(&eb->spinning_readers); |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 112 | return 1; |
| 113 | } |
| 114 | |
| 115 | /* |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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 |
| 118 | */ |
| 119 | int btrfs_try_tree_write_lock(struct extent_buffer *eb) |
| 120 | { |
| 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); |
| 132 | return 1; |
| 133 | } |
| 134 | |
| 135 | /* |
| 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 |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 162 | */ |
| 163 | int btrfs_tree_lock(struct extent_buffer *eb) |
| 164 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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; |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 174 | } |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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); |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 184 | return 0; |
| 185 | } |
| 186 | |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 187 | /* |
| 188 | * drop a spinning or a blocking write lock. |
| 189 | */ |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 190 | int btrfs_tree_unlock(struct extent_buffer *eb) |
| 191 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 192 | int blockers = atomic_read(&eb->blocking_writers); |
Chris Mason | b4ce94d | 2009-02-04 09:25:08 -0500 | [diff] [blame] | 193 | |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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 | } |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 209 | return 0; |
| 210 | } |
| 211 | |
Chris Mason | b9447ef | 2009-03-09 11:45:38 -0400 | [diff] [blame] | 212 | void btrfs_assert_tree_locked(struct extent_buffer *eb) |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 213 | { |
Chris Mason | bd68151 | 2011-07-16 15:23:14 -0400 | [diff] [blame] | 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)); |
Chris Mason | 925baed | 2008-06-25 16:01:30 -0400 | [diff] [blame] | 220 | } |