forked from luck/tmp_suning_uos_patched
ee86395458
There are atomic operations that imply the barrier for waitqueue_active mixed in an if-condition. Signed-off-by: David Sterba <dsterba@suse.com>
314 lines
8.4 KiB
C
314 lines
8.4 KiB
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);
|
|
}
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
}
|
|
|
|
void btrfs_assert_tree_locked(struct extent_buffer *eb)
|
|
{
|
|
BUG_ON(!atomic_read(&eb->write_locks));
|
|
}
|
|
|
|
static void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
|
|
{
|
|
BUG_ON(!atomic_read(&eb->read_locks));
|
|
}
|