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#include "blk-rq-qos.h"
#include "blk-wbt.h"
/*
* Increment 'v', if 'v' is below 'below'. Returns true if we succeeded,
* false if 'v' + 1 would be bigger than 'below'.
*/
static bool atomic_inc_below(atomic_t *v, int below)
{
int cur = atomic_read(v);
for (;;) {
int old;
if (cur >= below)
return false;
old = atomic_cmpxchg(v, cur, cur + 1);
if (old == cur)
break;
cur = old;
}
return true;
}
bool rq_wait_inc_below(struct rq_wait *rq_wait, int limit)
{
return atomic_inc_below(&rq_wait->inflight, limit);
}
void rq_qos_cleanup(struct request_queue *q, enum wbt_flags wb_acct)
{
struct rq_qos *rqos;
for (rqos = q->rq_qos; rqos; rqos = rqos->next) {
if (rqos->ops->cleanup)
rqos->ops->cleanup(rqos, wb_acct);
}
}
void rq_qos_done(struct request_queue *q, struct request *rq)
{
struct rq_qos *rqos;
for (rqos = q->rq_qos; rqos; rqos = rqos->next) {
if (rqos->ops->done)
rqos->ops->done(rqos, rq);
}
}
void rq_qos_issue(struct request_queue *q, struct request *rq)
{
struct rq_qos *rqos;
for(rqos = q->rq_qos; rqos; rqos = rqos->next) {
if (rqos->ops->issue)
rqos->ops->issue(rqos, rq);
}
}
void rq_qos_requeue(struct request_queue *q, struct request *rq)
{
struct rq_qos *rqos;
for(rqos = q->rq_qos; rqos; rqos = rqos->next) {
if (rqos->ops->requeue)
rqos->ops->requeue(rqos, rq);
}
}
enum wbt_flags rq_qos_throttle(struct request_queue *q, struct bio *bio,
spinlock_t *lock)
{
struct rq_qos *rqos;
enum wbt_flags flags = 0;
for(rqos = q->rq_qos; rqos; rqos = rqos->next) {
if (rqos->ops->throttle)
flags |= rqos->ops->throttle(rqos, bio, lock);
}
return flags;
}
/*
* Return true, if we can't increase the depth further by scaling
*/
bool rq_depth_calc_max_depth(struct rq_depth *rqd)
{
unsigned int depth;
bool ret = false;
/*
* For QD=1 devices, this is a special case. It's important for those
* to have one request ready when one completes, so force a depth of
* 2 for those devices. On the backend, it'll be a depth of 1 anyway,
* since the device can't have more than that in flight. If we're
* scaling down, then keep a setting of 1/1/1.
*/
if (rqd->queue_depth == 1) {
if (rqd->scale_step > 0)
rqd->max_depth = 1;
else {
rqd->max_depth = 2;
ret = true;
}
} else {
/*
* scale_step == 0 is our default state. If we have suffered
* latency spikes, step will be > 0, and we shrink the
* allowed write depths. If step is < 0, we're only doing
* writes, and we allow a temporarily higher depth to
* increase performance.
*/
depth = min_t(unsigned int, rqd->default_depth,
rqd->queue_depth);
if (rqd->scale_step > 0)
depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
else if (rqd->scale_step < 0) {
unsigned int maxd = 3 * rqd->queue_depth / 4;
depth = 1 + ((depth - 1) << -rqd->scale_step);
if (depth > maxd) {
depth = maxd;
ret = true;
}
}
rqd->max_depth = depth;
}
return ret;
}
void rq_depth_scale_up(struct rq_depth *rqd)
{
/*
* Hit max in previous round, stop here
*/
if (rqd->scaled_max)
return;
rqd->scale_step--;
rqd->scaled_max = rq_depth_calc_max_depth(rqd);
}
/*
* Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
* had a latency violation.
*/
void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
{
/*
* Stop scaling down when we've hit the limit. This also prevents
* ->scale_step from going to crazy values, if the device can't
* keep up.
*/
if (rqd->max_depth == 1)
return;
if (rqd->scale_step < 0 && hard_throttle)
rqd->scale_step = 0;
else
rqd->scale_step++;
rqd->scaled_max = false;
rq_depth_calc_max_depth(rqd);
}
void rq_qos_exit(struct request_queue *q)
{
while (q->rq_qos) {
struct rq_qos *rqos = q->rq_qos;
q->rq_qos = rqos->next;
rqos->ops->exit(rqos);
}
}
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