Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : 
       3             : #include "blk-rq-qos.h"
       4             : 
       5             : /*
       6             :  * Increment 'v', if 'v' is below 'below'. Returns true if we succeeded,
       7             :  * false if 'v' + 1 would be bigger than 'below'.
       8             :  */
       9           0 : static bool atomic_inc_below(atomic_t *v, unsigned int below)
      10             : {
      11           0 :         unsigned int cur = atomic_read(v);
      12             : 
      13           0 :         for (;;) {
      14           0 :                 unsigned int old;
      15             : 
      16           0 :                 if (cur >= below)
      17             :                         return false;
      18           0 :                 old = atomic_cmpxchg(v, cur, cur + 1);
      19           0 :                 if (old == cur)
      20             :                         break;
      21             :                 cur = old;
      22             :         }
      23             : 
      24             :         return true;
      25             : }
      26             : 
      27           0 : bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit)
      28             : {
      29           0 :         return atomic_inc_below(&rq_wait->inflight, limit);
      30             : }
      31             : 
      32           0 : void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio)
      33             : {
      34           0 :         do {
      35           0 :                 if (rqos->ops->cleanup)
      36           0 :                         rqos->ops->cleanup(rqos, bio);
      37           0 :                 rqos = rqos->next;
      38           0 :         } while (rqos);
      39           0 : }
      40             : 
      41           0 : void __rq_qos_done(struct rq_qos *rqos, struct request *rq)
      42             : {
      43           0 :         do {
      44           0 :                 if (rqos->ops->done)
      45           0 :                         rqos->ops->done(rqos, rq);
      46           0 :                 rqos = rqos->next;
      47           0 :         } while (rqos);
      48           0 : }
      49             : 
      50           0 : void __rq_qos_issue(struct rq_qos *rqos, struct request *rq)
      51             : {
      52           0 :         do {
      53           0 :                 if (rqos->ops->issue)
      54           0 :                         rqos->ops->issue(rqos, rq);
      55           0 :                 rqos = rqos->next;
      56           0 :         } while (rqos);
      57           0 : }
      58             : 
      59           0 : void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq)
      60             : {
      61           0 :         do {
      62           0 :                 if (rqos->ops->requeue)
      63           0 :                         rqos->ops->requeue(rqos, rq);
      64           0 :                 rqos = rqos->next;
      65           0 :         } while (rqos);
      66           0 : }
      67             : 
      68           0 : void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio)
      69             : {
      70           0 :         do {
      71           0 :                 if (rqos->ops->throttle)
      72           0 :                         rqos->ops->throttle(rqos, bio);
      73           0 :                 rqos = rqos->next;
      74           0 :         } while (rqos);
      75           0 : }
      76             : 
      77           0 : void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
      78             : {
      79           0 :         do {
      80           0 :                 if (rqos->ops->track)
      81           0 :                         rqos->ops->track(rqos, rq, bio);
      82           0 :                 rqos = rqos->next;
      83           0 :         } while (rqos);
      84           0 : }
      85             : 
      86           0 : void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio)
      87             : {
      88           0 :         do {
      89           0 :                 if (rqos->ops->merge)
      90           0 :                         rqos->ops->merge(rqos, rq, bio);
      91           0 :                 rqos = rqos->next;
      92           0 :         } while (rqos);
      93           0 : }
      94             : 
      95           0 : void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio)
      96             : {
      97           0 :         do {
      98           0 :                 if (rqos->ops->done_bio)
      99           0 :                         rqos->ops->done_bio(rqos, bio);
     100           0 :                 rqos = rqos->next;
     101           0 :         } while (rqos);
     102           0 : }
     103             : 
     104           0 : void __rq_qos_queue_depth_changed(struct rq_qos *rqos)
     105             : {
     106           0 :         do {
     107           0 :                 if (rqos->ops->queue_depth_changed)
     108           0 :                         rqos->ops->queue_depth_changed(rqos);
     109           0 :                 rqos = rqos->next;
     110           0 :         } while (rqos);
     111           0 : }
     112             : 
     113             : /*
     114             :  * Return true, if we can't increase the depth further by scaling
     115             :  */
     116           0 : bool rq_depth_calc_max_depth(struct rq_depth *rqd)
     117             : {
     118           0 :         unsigned int depth;
     119           0 :         bool ret = false;
     120             : 
     121             :         /*
     122             :          * For QD=1 devices, this is a special case. It's important for those
     123             :          * to have one request ready when one completes, so force a depth of
     124             :          * 2 for those devices. On the backend, it'll be a depth of 1 anyway,
     125             :          * since the device can't have more than that in flight. If we're
     126             :          * scaling down, then keep a setting of 1/1/1.
     127             :          */
     128           0 :         if (rqd->queue_depth == 1) {
     129           0 :                 if (rqd->scale_step > 0)
     130           0 :                         rqd->max_depth = 1;
     131             :                 else {
     132           0 :                         rqd->max_depth = 2;
     133           0 :                         ret = true;
     134             :                 }
     135             :         } else {
     136             :                 /*
     137             :                  * scale_step == 0 is our default state. If we have suffered
     138             :                  * latency spikes, step will be > 0, and we shrink the
     139             :                  * allowed write depths. If step is < 0, we're only doing
     140             :                  * writes, and we allow a temporarily higher depth to
     141             :                  * increase performance.
     142             :                  */
     143           0 :                 depth = min_t(unsigned int, rqd->default_depth,
     144             :                               rqd->queue_depth);
     145           0 :                 if (rqd->scale_step > 0)
     146           0 :                         depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
     147           0 :                 else if (rqd->scale_step < 0) {
     148           0 :                         unsigned int maxd = 3 * rqd->queue_depth / 4;
     149             : 
     150           0 :                         depth = 1 + ((depth - 1) << -rqd->scale_step);
     151           0 :                         if (depth > maxd) {
     152           0 :                                 depth = maxd;
     153           0 :                                 ret = true;
     154             :                         }
     155             :                 }
     156             : 
     157           0 :                 rqd->max_depth = depth;
     158             :         }
     159             : 
     160           0 :         return ret;
     161             : }
     162             : 
     163             : /* Returns true on success and false if scaling up wasn't possible */
     164           0 : bool rq_depth_scale_up(struct rq_depth *rqd)
     165             : {
     166             :         /*
     167             :          * Hit max in previous round, stop here
     168             :          */
     169           0 :         if (rqd->scaled_max)
     170             :                 return false;
     171             : 
     172           0 :         rqd->scale_step--;
     173             : 
     174           0 :         rqd->scaled_max = rq_depth_calc_max_depth(rqd);
     175           0 :         return true;
     176             : }
     177             : 
     178             : /*
     179             :  * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
     180             :  * had a latency violation. Returns true on success and returns false if
     181             :  * scaling down wasn't possible.
     182             :  */
     183           0 : bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
     184             : {
     185             :         /*
     186             :          * Stop scaling down when we've hit the limit. This also prevents
     187             :          * ->scale_step from going to crazy values, if the device can't
     188             :          * keep up.
     189             :          */
     190           0 :         if (rqd->max_depth == 1)
     191             :                 return false;
     192             : 
     193           0 :         if (rqd->scale_step < 0 && hard_throttle)
     194           0 :                 rqd->scale_step = 0;
     195             :         else
     196           0 :                 rqd->scale_step++;
     197             : 
     198           0 :         rqd->scaled_max = false;
     199           0 :         rq_depth_calc_max_depth(rqd);
     200           0 :         return true;
     201             : }
     202             : 
     203             : struct rq_qos_wait_data {
     204             :         struct wait_queue_entry wq;
     205             :         struct task_struct *task;
     206             :         struct rq_wait *rqw;
     207             :         acquire_inflight_cb_t *cb;
     208             :         void *private_data;
     209             :         bool got_token;
     210             : };
     211             : 
     212           0 : static int rq_qos_wake_function(struct wait_queue_entry *curr,
     213             :                                 unsigned int mode, int wake_flags, void *key)
     214             : {
     215           0 :         struct rq_qos_wait_data *data = container_of(curr,
     216             :                                                      struct rq_qos_wait_data,
     217             :                                                      wq);
     218             : 
     219             :         /*
     220             :          * If we fail to get a budget, return -1 to interrupt the wake up loop
     221             :          * in __wake_up_common.
     222             :          */
     223           0 :         if (!data->cb(data->rqw, data->private_data))
     224             :                 return -1;
     225             : 
     226           0 :         data->got_token = true;
     227           0 :         smp_wmb();
     228           0 :         list_del_init(&curr->entry);
     229           0 :         wake_up_process(data->task);
     230           0 :         return 1;
     231             : }
     232             : 
     233             : /**
     234             :  * rq_qos_wait - throttle on a rqw if we need to
     235             :  * @rqw: rqw to throttle on
     236             :  * @private_data: caller provided specific data
     237             :  * @acquire_inflight_cb: inc the rqw->inflight counter if we can
     238             :  * @cleanup_cb: the callback to cleanup in case we race with a waker
     239             :  *
     240             :  * This provides a uniform place for the rq_qos users to do their throttling.
     241             :  * Since you can end up with a lot of things sleeping at once, this manages the
     242             :  * waking up based on the resources available.  The acquire_inflight_cb should
     243             :  * inc the rqw->inflight if we have the ability to do so, or return false if not
     244             :  * and then we will sleep until the room becomes available.
     245             :  *
     246             :  * cleanup_cb is in case that we race with a waker and need to cleanup the
     247             :  * inflight count accordingly.
     248             :  */
     249           0 : void rq_qos_wait(struct rq_wait *rqw, void *private_data,
     250             :                  acquire_inflight_cb_t *acquire_inflight_cb,
     251             :                  cleanup_cb_t *cleanup_cb)
     252             : {
     253           0 :         struct rq_qos_wait_data data = {
     254             :                 .wq = {
     255             :                         .func   = rq_qos_wake_function,
     256             :                         .entry  = LIST_HEAD_INIT(data.wq.entry),
     257             :                 },
     258           0 :                 .task = current,
     259             :                 .rqw = rqw,
     260             :                 .cb = acquire_inflight_cb,
     261             :                 .private_data = private_data,
     262             :         };
     263           0 :         bool has_sleeper;
     264             : 
     265           0 :         has_sleeper = wq_has_sleeper(&rqw->wait);
     266           0 :         if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
     267           0 :                 return;
     268             : 
     269           0 :         prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE);
     270           0 :         has_sleeper = !wq_has_single_sleeper(&rqw->wait);
     271           0 :         do {
     272             :                 /* The memory barrier in set_task_state saves us here. */
     273           0 :                 if (data.got_token)
     274             :                         break;
     275           0 :                 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
     276           0 :                         finish_wait(&rqw->wait, &data.wq);
     277             : 
     278             :                         /*
     279             :                          * We raced with wbt_wake_function() getting a token,
     280             :                          * which means we now have two. Put our local token
     281             :                          * and wake anyone else potentially waiting for one.
     282             :                          */
     283           0 :                         smp_rmb();
     284           0 :                         if (data.got_token)
     285           0 :                                 cleanup_cb(rqw, private_data);
     286             :                         break;
     287             :                 }
     288           0 :                 io_schedule();
     289           0 :                 has_sleeper = true;
     290           0 :                 set_current_state(TASK_UNINTERRUPTIBLE);
     291           0 :         } while (1);
     292           0 :         finish_wait(&rqw->wait, &data.wq);
     293             : }
     294             : 
     295           0 : void rq_qos_exit(struct request_queue *q)
     296             : {
     297           0 :         blk_mq_debugfs_unregister_queue_rqos(q);
     298             : 
     299           0 :         while (q->rq_qos) {
     300           0 :                 struct rq_qos *rqos = q->rq_qos;
     301           0 :                 q->rq_qos = rqos->next;
     302           0 :                 rqos->ops->exit(rqos);
     303             :         }
     304           0 : }