/*
* This is somewhat different from trylock. It will take the
* spinlock but if it finds the lock is set to blocking, it will
* return without the lock held.
*
* returns 1 if it was able to take the lock and zero otherwise
*
* After this call, scheduling is not safe without first calling
* btrfs_set_lock_blocking()
*/
int btrfs_try_spin_lock(struct extent_buffer *eb)
{
#ifndef CONFIG_PREEMPT_RT
int i;
if (btrfs_spin_on_block(eb)) {
spin_nested(eb);
if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
return 1;
spin_unlock(&eb->lock);
}
/* spin for a bit on the BLOCKING flag */
for (i = 0; i < 2; i++) {
cpu_relax();
if (!btrfs_spin_on_block(eb))
break;
spin_nested(eb);
if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
return 1;
spin_unlock(&eb->lock);
}
#endif
return 0;
}
/*
* returns with the extent buffer spinlocked.
*
* This will spin and/or wait as required to take the lock, and then
* return with the spinlock held.
*
* After this call, scheduling is not safe without first calling
* btrfs_set_lock_blocking()
*/
int btrfs_tree_lock(struct extent_buffer *eb)
{
DEFINE_WAIT(wait);
wait.func = btrfs_wake_function;
while(1) {
spin_nested(eb);
/* nobody is blocking, exit with the spinlock held */
if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
return 0;
/*
* we have the spinlock, but the real owner is blocking.
* wait for them
*/
spin_unlock(&eb->lock);
/*
* spin for a bit, and if the blocking flag goes away,
* loop around
*/
if (btrfs_spin_on_block(eb))
continue;
prepare_to_wait_exclusive(&eb->lock_wq, &wait,
TASK_UNINTERRUPTIBLE);
if (test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
schedule();
finish_wait(&eb->lock_wq, &wait);
}
return 0;
}
/*
* This is somewhat different from trylock. It will take the
* spinlock but if it finds the lock is set to blocking, it will
* return without the lock held.
*
* returns 1 if it was able to take the lock and zero otherwise
*
* After this call, scheduling is not safe without first calling
* btrfs_set_lock_blocking()
*/
int btrfs_try_spin_lock(struct extent_buffer *eb)
{
int i;
spin_nested(eb);
if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
return 1;
spin_unlock(&eb->lock);
/* spin for a bit on the BLOCKING flag */
for (i = 0; i < 2; i++) {
if (!btrfs_spin_on_block(eb))
break;
spin_nested(eb);
if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
return 1;
spin_unlock(&eb->lock);
}
return 0;
}