/*
* We have two copies, and flip between them to make it seem like an atomic
* update. The update is not really atomic wrt the events counter, but
* it is internally consistent with the bit layout depending on shift.
*
* We copy the events count, move the bits around and flip the index.
*/
void prop_change_shift(struct prop_descriptor *pd, int shift)
{
int index;
int offset;
u64 events;
unsigned long flags;
if (shift > PROP_MAX_SHIFT)
shift = PROP_MAX_SHIFT;
mutex_lock(&pd->mutex);
index = pd->index ^ 1;
offset = pd->pg[pd->index].shift - shift;
if (!offset)
goto out;
pd->pg[index].shift = shift;
local_irq_save(flags);
events = percpu_counter_sum(&pd->pg[pd->index].events);
if (offset < 0)
events <<= -offset;
else
events >>= offset;
percpu_counter_set(&pd->pg[index].events, events);
/*
* ensure the new pg is fully written before the switch
*/
smp_wmb();
pd->index = index;
local_irq_restore(flags);
synchronize_rcu();
out:
mutex_unlock(&pd->mutex);
}
/*
* Compare counter against given value.
* Return 1 if greater, 0 if equal and -1 if less
*/
int __percpu_counter_compare(struct percpu_counter *fbc, int64_t rhs,
int32_t batch)
{
int64_t count;
count = percpu_counter_read(fbc);
/* Check to see if rough count will be sufficient for comparison */
if (abs(count - rhs) > (batch * num_online_cpus())) {
if (count > rhs)
return 1;
else
return -1;
}
/* Need to use precise count */
count = percpu_counter_sum(fbc);
if (count > rhs)
return 1;
else if (count < rhs)
return -1;
else
return 0;
}
/*
* Catch up with missed period expirations.
*
* until (c_{j} == c)
* x_{j} -= x_{j}/2;
* c_{j}++;
*/
static
void prop_norm_percpu(struct prop_global *pg, struct prop_local_percpu *pl)
{
unsigned long period = 1UL << (pg->shift - 1);
unsigned long period_mask = ~(period - 1);
unsigned long global_period;
unsigned long flags;
global_period = percpu_counter_read(&pg->events);
global_period &= period_mask;
/*
* Fast path - check if the local and global period count still match
* outside of the lock.
*/
if (pl->period == global_period)
return;
raw_spin_lock_irqsave(&pl->lock, flags);
prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
/*
* For each missed period, we half the local counter.
* basically:
* pl->events >> (global_period - pl->period);
*/
period = (global_period - pl->period) >> (pg->shift - 1);
if (period < BITS_PER_LONG) {
s64 val = percpu_counter_read(&pl->events);
if (val < (nr_cpu_ids * PROP_BATCH))
val = percpu_counter_sum(&pl->events);
__percpu_counter_add(&pl->events, -val + (val >> period),
PROP_BATCH);
} else
static
void prop_norm_percpu(struct prop_global *pg, struct prop_local_percpu *pl)
{
unsigned long period = 1UL << (pg->shift - 1);
unsigned long period_mask = ~(period - 1);
unsigned long global_period;
unsigned long flags;
global_period = percpu_counter_read(&pg->events);
global_period &= period_mask;
/*
*/
if (pl->period == global_period)
return;
raw_spin_lock_irqsave(&pl->lock, flags);
prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
/*
*/
period = (global_period - pl->period) >> (pg->shift - 1);
if (period < BITS_PER_LONG) {
s64 val = percpu_counter_read(&pl->events);
if (val < (nr_cpu_ids * PROP_BATCH))
val = percpu_counter_sum(&pl->events);
__percpu_counter_add(&pl->events, -val + (val >> period),
PROP_BATCH);
} else
uint64_t read_partitioned_counter(PARTITIONED_COUNTER pc) {
return percpu_counter_sum(&pc->pcpu_counter);
}
/*
* blocked until all in-flight bios operations are finished.
*/
static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
{
set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
&fs_info->dev_replace.bio_counter));
}
