Release 4.11 fs/btrfs/locking.c
/*
* Copyright (C) 2008 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#include <linux/sched.h>
#include <linux/pagemap.h>
#include <linux/spinlock.h>
#include <linux/page-flags.h>
#include <asm/bug.h>
#include "ctree.h"
#include "extent_io.h"
#include "locking.h"
static void btrfs_assert_tree_read_locked(struct extent_buffer *eb);
/*
* if we currently have a spinning reader or writer lock
* (indicated by the rw flag) this will bump the count
* of blocking holders and drop the spinlock.
*/
void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw)
{
/*
* no lock is required. The lock owner may change if
* we have a read lock, but it won't change to or away
* from us. If we have the write lock, we are the owner
* and it'll never change.
*/
if (eb->lock_nested && current->pid == eb->lock_owner)
return;
if (rw == BTRFS_WRITE_LOCK) {
if (atomic_read(&eb->blocking_writers) == 0) {
WARN_ON(atomic_read(&eb->spinning_writers) != 1);
atomic_dec(&eb->spinning_writers);
btrfs_assert_tree_locked(eb);
atomic_inc(&eb->blocking_writers);
write_unlock(&eb->lock);
}
} else if (rw == BTRFS_READ_LOCK) {
btrfs_assert_tree_read_locked(eb);
atomic_inc(&eb->blocking_readers);
WARN_ON(atomic_read(&eb->spinning_readers) == 0);
atomic_dec(&eb->spinning_readers);
read_unlock(&eb->lock);
}
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 127 | 88.19% | 3 | 75.00% |
| Arne Jansen | 17 | 11.81% | 1 | 25.00% |
| Total | 144 | 100.00% | 4 | 100.00% |
/*
* if we currently have a blocking lock, take the spinlock
* and drop our blocking count
*/
void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
{
/*
* no lock is required. The lock owner may change if
* we have a read lock, but it won't change to or away
* from us. If we have the write lock, we are the owner
* and it'll never change.
*/
if (eb->lock_nested && current->pid == eb->lock_owner)
return;
if (rw == BTRFS_WRITE_LOCK_BLOCKING) {
BUG_ON(atomic_read(&eb->blocking_writers) != 1);
write_lock(&eb->lock);
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_inc(&eb->spinning_writers);
/*
* atomic_dec_and_test implies a barrier for waitqueue_active
*/
if (atomic_dec_and_test(&eb->blocking_writers) &&
waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);
} else if (rw == BTRFS_READ_LOCK_BLOCKING) {
BUG_ON(atomic_read(&eb->blocking_readers) == 0);
read_lock(&eb->lock);
atomic_inc(&eb->spinning_readers);
/*
* atomic_dec_and_test implies a barrier for waitqueue_active
*/
if (atomic_dec_and_test(&eb->blocking_readers) &&
waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);
}
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 150 | 88.76% | 4 | 66.67% |
| Arne Jansen | 17 | 10.06% | 1 | 16.67% |
| David Sterba | 2 | 1.18% | 1 | 16.67% |
| Total | 169 | 100.00% | 6 | 100.00% |
/*
* take a spinning read lock. This will wait for any blocking
* writers
*/
void btrfs_tree_read_lock(struct extent_buffer *eb)
{
again:
BUG_ON(!atomic_read(&eb->blocking_writers) &&
current->pid == eb->lock_owner);
read_lock(&eb->lock);
if (atomic_read(&eb->blocking_writers) &&
current->pid == eb->lock_owner) {
/*
* This extent is already write-locked by our thread. We allow
* an additional read lock to be added because it's for the same
* thread. btrfs_find_all_roots() depends on this as it may be
* called on a partly (write-)locked tree.
*/
BUG_ON(eb->lock_nested);
eb->lock_nested = 1;
read_unlock(&eb->lock);
return;
}
if (atomic_read(&eb->blocking_writers)) {
read_unlock(&eb->lock);
wait_event(eb->write_lock_wq,
atomic_read(&eb->blocking_writers) == 0);
goto again;
}
atomic_inc(&eb->read_locks);
atomic_inc(&eb->spinning_readers);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 98 | 70.50% | 3 | 60.00% |
| Arne Jansen | 30 | 21.58% | 1 | 20.00% |
| Liu Bo | 11 | 7.91% | 1 | 20.00% |
| Total | 139 | 100.00% | 5 | 100.00% |
/*
* take a spinning read lock.
* returns 1 if we get the read lock and 0 if we don't
* this won't wait for blocking writers
*/
int btrfs_tree_read_lock_atomic(struct extent_buffer *eb)
{
if (atomic_read(&eb->blocking_writers))
return 0;
read_lock(&eb->lock);
if (atomic_read(&eb->blocking_writers)) {
read_unlock(&eb->lock);
return 0;
}
atomic_inc(&eb->read_locks);
atomic_inc(&eb->spinning_readers);
return 1;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 73 | 100.00% | 1 | 100.00% |
| Total | 73 | 100.00% | 1 | 100.00% |
/*
* returns 1 if we get the read lock and 0 if we don't
* this won't wait for blocking writers
*/
int btrfs_try_tree_read_lock(struct extent_buffer *eb)
{
if (atomic_read(&eb->blocking_writers))
return 0;
if (!read_trylock(&eb->lock))
return 0;
if (atomic_read(&eb->blocking_writers)) {
read_unlock(&eb->lock);
return 0;
}
atomic_inc(&eb->read_locks);
atomic_inc(&eb->spinning_readers);
return 1;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 79 | 100.00% | 6 | 100.00% |
| Total | 79 | 100.00% | 6 | 100.00% |
/*
* returns 1 if we get the read lock and 0 if we don't
* this won't wait for blocking writers or readers
*/
int btrfs_try_tree_write_lock(struct extent_buffer *eb)
{
if (atomic_read(&eb->blocking_writers) ||
atomic_read(&eb->blocking_readers))
return 0;
write_lock(&eb->lock);
if (atomic_read(&eb->blocking_writers) ||
atomic_read(&eb->blocking_readers)) {
write_unlock(&eb->lock);
return 0;
}
atomic_inc(&eb->write_locks);
atomic_inc(&eb->spinning_writers);
eb->lock_owner = current->pid;
return 1;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 89 | 91.75% | 5 | 83.33% |
| Arne Jansen | 8 | 8.25% | 1 | 16.67% |
| Total | 97 | 100.00% | 6 | 100.00% |
/*
* drop a spinning read lock
*/
void btrfs_tree_read_unlock(struct extent_buffer *eb)
{
/*
* if we're nested, we have the write lock. No new locking
* is needed as long as we are the lock owner.
* The write unlock will do a barrier for us, and the lock_nested
* field only matters to the lock owner.
*/
if (eb->lock_nested && current->pid == eb->lock_owner) {
eb->lock_nested = 0;
return;
}
btrfs_assert_tree_read_locked(eb);
WARN_ON(atomic_read(&eb->spinning_readers) == 0);
atomic_dec(&eb->spinning_readers);
atomic_dec(&eb->read_locks);
read_unlock(&eb->lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 53 | 69.74% | 4 | 80.00% |
| Arne Jansen | 23 | 30.26% | 1 | 20.00% |
| Total | 76 | 100.00% | 5 | 100.00% |
/*
* drop a blocking read lock
*/
void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
{
/*
* if we're nested, we have the write lock. No new locking
* is needed as long as we are the lock owner.
* The write unlock will do a barrier for us, and the lock_nested
* field only matters to the lock owner.
*/
if (eb->lock_nested && current->pid == eb->lock_owner) {
eb->lock_nested = 0;
return;
}
btrfs_assert_tree_read_locked(eb);
WARN_ON(atomic_read(&eb->blocking_readers) == 0);
/*
* atomic_dec_and_test implies a barrier for waitqueue_active
*/
if (atomic_dec_and_test(&eb->blocking_readers) &&
waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);
atomic_dec(&eb->read_locks);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 63 | 72.41% | 6 | 75.00% |
| Arne Jansen | 23 | 26.44% | 1 | 12.50% |
| David Sterba | 1 | 1.15% | 1 | 12.50% |
| Total | 87 | 100.00% | 8 | 100.00% |
/*
* take a spinning write lock. This will wait for both
* blocking readers or writers
*/
void btrfs_tree_lock(struct extent_buffer *eb)
{
WARN_ON(eb->lock_owner == current->pid);
again:
wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
write_lock(&eb->lock);
if (atomic_read(&eb->blocking_readers)) {
write_unlock(&eb->lock);
wait_event(eb->read_lock_wq,
atomic_read(&eb->blocking_readers) == 0);
goto again;
}
if (atomic_read(&eb->blocking_writers)) {
write_unlock(&eb->lock);
wait_event(eb->write_lock_wq,
atomic_read(&eb->blocking_writers) == 0);
goto again;
}
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_inc(&eb->spinning_writers);
atomic_inc(&eb->write_locks);
eb->lock_owner = current->pid;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 160 | 88.89% | 6 | 66.67% |
| Zhao Lei | 11 | 6.11% | 1 | 11.11% |
| Arne Jansen | 8 | 4.44% | 1 | 11.11% |
| Jeff Mahoney | 1 | 0.56% | 1 | 11.11% |
| Total | 180 | 100.00% | 9 | 100.00% |
/*
* drop a spinning or a blocking write lock.
*/
void btrfs_tree_unlock(struct extent_buffer *eb)
{
int blockers = atomic_read(&eb->blocking_writers);
BUG_ON(blockers > 1);
btrfs_assert_tree_locked(eb);
eb->lock_owner = 0;
atomic_dec(&eb->write_locks);
if (blockers) {
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_dec(&eb->blocking_writers);
/*
* Make sure counter is updated before we wake up waiters.
*/
smp_mb();
if (waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);
} else {
WARN_ON(atomic_read(&eb->spinning_writers) != 1);
atomic_dec(&eb->spinning_writers);
write_unlock(&eb->lock);
}
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 124 | 98.41% | 6 | 75.00% |
| David Sterba | 1 | 0.79% | 1 | 12.50% |
| Jeff Mahoney | 1 | 0.79% | 1 | 12.50% |
| Total | 126 | 100.00% | 8 | 100.00% |
void btrfs_assert_tree_locked(struct extent_buffer *eb)
{
BUG_ON(!atomic_read(&eb->write_locks));
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 22 | 100.00% | 5 | 100.00% |
| Total | 22 | 100.00% | 5 | 100.00% |
static void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
{
BUG_ON(!atomic_read(&eb->read_locks));
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 22 | 95.65% | 4 | 80.00% |
| Eric Sandeen | 1 | 4.35% | 1 | 20.00% |
| Total | 23 | 100.00% | 5 | 100.00% |
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Chris Mason | 1104 | 87.62% | 13 | 65.00% |
| Arne Jansen | 126 | 10.00% | 1 | 5.00% |
| Zhao Lei | 11 | 0.87% | 1 | 5.00% |
| Liu Bo | 11 | 0.87% | 1 | 5.00% |
| David Sterba | 4 | 0.32% | 2 | 10.00% |
| Jeff Mahoney | 2 | 0.16% | 1 | 5.00% |
| Eric Sandeen | 2 | 0.16% | 1 | 5.00% |
| Total | 1260 | 100.00% | 20 | 100.00% |
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.