303 lines
7.0 KiB
C
303 lines
7.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include "blk-rq-qos.h"
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/*
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* Increment 'v', if 'v' is below 'below'. Returns true if we succeeded,
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* false if 'v' + 1 would be bigger than 'below'.
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*/
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static bool atomic_inc_below(atomic_t *v, unsigned int below)
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{
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unsigned int cur = atomic_read(v);
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for (;;) {
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unsigned int old;
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if (cur >= below)
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return false;
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old = atomic_cmpxchg(v, cur, cur + 1);
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if (old == cur)
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break;
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cur = old;
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}
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return true;
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}
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bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit)
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{
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return atomic_inc_below(&rq_wait->inflight, limit);
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}
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void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio)
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{
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do {
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if (rqos->ops->cleanup)
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rqos->ops->cleanup(rqos, bio);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_done(struct rq_qos *rqos, struct request *rq)
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{
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do {
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if (rqos->ops->done)
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rqos->ops->done(rqos, rq);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_issue(struct rq_qos *rqos, struct request *rq)
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{
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do {
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if (rqos->ops->issue)
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rqos->ops->issue(rqos, rq);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq)
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{
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do {
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if (rqos->ops->requeue)
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rqos->ops->requeue(rqos, rq);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio)
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{
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do {
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if (rqos->ops->throttle)
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rqos->ops->throttle(rqos, bio);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
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{
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do {
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if (rqos->ops->track)
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rqos->ops->track(rqos, rq, bio);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio)
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{
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do {
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if (rqos->ops->merge)
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rqos->ops->merge(rqos, rq, bio);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio)
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{
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do {
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if (rqos->ops->done_bio)
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rqos->ops->done_bio(rqos, bio);
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rqos = rqos->next;
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} while (rqos);
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}
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void __rq_qos_queue_depth_changed(struct rq_qos *rqos)
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{
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do {
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if (rqos->ops->queue_depth_changed)
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rqos->ops->queue_depth_changed(rqos);
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rqos = rqos->next;
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} while (rqos);
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}
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/*
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* Return true, if we can't increase the depth further by scaling
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*/
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bool rq_depth_calc_max_depth(struct rq_depth *rqd)
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{
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unsigned int depth;
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bool ret = false;
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/*
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* For QD=1 devices, this is a special case. It's important for those
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* to have one request ready when one completes, so force a depth of
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* 2 for those devices. On the backend, it'll be a depth of 1 anyway,
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* since the device can't have more than that in flight. If we're
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* scaling down, then keep a setting of 1/1/1.
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*/
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if (rqd->queue_depth == 1) {
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if (rqd->scale_step > 0)
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rqd->max_depth = 1;
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else {
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rqd->max_depth = 2;
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ret = true;
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}
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} else {
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/*
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* scale_step == 0 is our default state. If we have suffered
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* latency spikes, step will be > 0, and we shrink the
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* allowed write depths. If step is < 0, we're only doing
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* writes, and we allow a temporarily higher depth to
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* increase performance.
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*/
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depth = min_t(unsigned int, rqd->default_depth,
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rqd->queue_depth);
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if (rqd->scale_step > 0)
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depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
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else if (rqd->scale_step < 0) {
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unsigned int maxd = 3 * rqd->queue_depth / 4;
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depth = 1 + ((depth - 1) << -rqd->scale_step);
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if (depth > maxd) {
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depth = maxd;
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ret = true;
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}
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}
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rqd->max_depth = depth;
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}
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return ret;
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}
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/* Returns true on success and false if scaling up wasn't possible */
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bool rq_depth_scale_up(struct rq_depth *rqd)
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{
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/*
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* Hit max in previous round, stop here
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*/
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if (rqd->scaled_max)
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return false;
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rqd->scale_step--;
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rqd->scaled_max = rq_depth_calc_max_depth(rqd);
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return true;
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}
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/*
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* Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
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* had a latency violation. Returns true on success and returns false if
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* scaling down wasn't possible.
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*/
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bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
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{
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/*
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* Stop scaling down when we've hit the limit. This also prevents
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* ->scale_step from going to crazy values, if the device can't
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* keep up.
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*/
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if (rqd->max_depth == 1)
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return false;
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if (rqd->scale_step < 0 && hard_throttle)
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rqd->scale_step = 0;
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else
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rqd->scale_step++;
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rqd->scaled_max = false;
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rq_depth_calc_max_depth(rqd);
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return true;
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}
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struct rq_qos_wait_data {
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struct wait_queue_entry wq;
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struct task_struct *task;
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struct rq_wait *rqw;
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acquire_inflight_cb_t *cb;
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void *private_data;
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bool got_token;
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};
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static int rq_qos_wake_function(struct wait_queue_entry *curr,
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unsigned int mode, int wake_flags, void *key)
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{
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struct rq_qos_wait_data *data = container_of(curr,
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struct rq_qos_wait_data,
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wq);
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/*
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* If we fail to get a budget, return -1 to interrupt the wake up loop
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* in __wake_up_common.
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*/
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if (!data->cb(data->rqw, data->private_data))
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return -1;
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data->got_token = true;
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smp_wmb();
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list_del_init(&curr->entry);
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wake_up_process(data->task);
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return 1;
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}
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/**
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* rq_qos_wait - throttle on a rqw if we need to
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* @rqw: rqw to throttle on
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* @private_data: caller provided specific data
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* @acquire_inflight_cb: inc the rqw->inflight counter if we can
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* @cleanup_cb: the callback to cleanup in case we race with a waker
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*
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* This provides a uniform place for the rq_qos users to do their throttling.
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* Since you can end up with a lot of things sleeping at once, this manages the
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* waking up based on the resources available. The acquire_inflight_cb should
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* inc the rqw->inflight if we have the ability to do so, or return false if not
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* and then we will sleep until the room becomes available.
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*
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* cleanup_cb is in case that we race with a waker and need to cleanup the
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* inflight count accordingly.
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*/
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void rq_qos_wait(struct rq_wait *rqw, void *private_data,
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acquire_inflight_cb_t *acquire_inflight_cb,
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cleanup_cb_t *cleanup_cb)
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{
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struct rq_qos_wait_data data = {
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.wq = {
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.func = rq_qos_wake_function,
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.entry = LIST_HEAD_INIT(data.wq.entry),
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},
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.task = current,
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.rqw = rqw,
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.cb = acquire_inflight_cb,
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.private_data = private_data,
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};
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bool has_sleeper;
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has_sleeper = wq_has_sleeper(&rqw->wait);
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if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
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return;
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has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq,
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TASK_UNINTERRUPTIBLE);
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do {
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/* The memory barrier in set_task_state saves us here. */
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if (data.got_token)
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break;
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if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
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finish_wait(&rqw->wait, &data.wq);
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/*
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* We raced with wbt_wake_function() getting a token,
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* which means we now have two. Put our local token
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* and wake anyone else potentially waiting for one.
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*/
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smp_rmb();
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if (data.got_token)
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cleanup_cb(rqw, private_data);
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break;
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}
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io_schedule();
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has_sleeper = true;
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set_current_state(TASK_UNINTERRUPTIBLE);
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} while (1);
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finish_wait(&rqw->wait, &data.wq);
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}
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void rq_qos_exit(struct request_queue *q)
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{
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while (q->rq_qos) {
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struct rq_qos *rqos = q->rq_qos;
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q->rq_qos = rqos->next;
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rqos->ops->exit(rqos);
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}
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}
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