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             : static bool atomic_inc_below(atomic_t *v, unsigned int below)
      10             : {
      11           0 :         unsigned int cur = atomic_read(v);
      12             : 
      13             :         do {
      14           0 :                 if (cur >= below)
      15             :                         return false;
      16           0 :         } while (!atomic_try_cmpxchg(v, &cur, cur + 1));
      17             : 
      18             :         return true;
      19             : }
      20             : 
      21           0 : bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit)
      22             : {
      23           0 :         return atomic_inc_below(&rq_wait->inflight, limit);
      24             : }
      25             : 
      26           0 : void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio)
      27             : {
      28             :         do {
      29           0 :                 if (rqos->ops->cleanup)
      30           0 :                         rqos->ops->cleanup(rqos, bio);
      31           0 :                 rqos = rqos->next;
      32           0 :         } while (rqos);
      33           0 : }
      34             : 
      35           0 : void __rq_qos_done(struct rq_qos *rqos, struct request *rq)
      36             : {
      37             :         do {
      38           0 :                 if (rqos->ops->done)
      39           0 :                         rqos->ops->done(rqos, rq);
      40           0 :                 rqos = rqos->next;
      41           0 :         } while (rqos);
      42           0 : }
      43             : 
      44           0 : void __rq_qos_issue(struct rq_qos *rqos, struct request *rq)
      45             : {
      46             :         do {
      47           0 :                 if (rqos->ops->issue)
      48           0 :                         rqos->ops->issue(rqos, rq);
      49           0 :                 rqos = rqos->next;
      50           0 :         } while (rqos);
      51           0 : }
      52             : 
      53           0 : void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq)
      54             : {
      55             :         do {
      56           0 :                 if (rqos->ops->requeue)
      57           0 :                         rqos->ops->requeue(rqos, rq);
      58           0 :                 rqos = rqos->next;
      59           0 :         } while (rqos);
      60           0 : }
      61             : 
      62           0 : void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio)
      63             : {
      64             :         do {
      65           0 :                 if (rqos->ops->throttle)
      66           0 :                         rqos->ops->throttle(rqos, bio);
      67           0 :                 rqos = rqos->next;
      68           0 :         } while (rqos);
      69           0 : }
      70             : 
      71           0 : void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
      72             : {
      73             :         do {
      74           0 :                 if (rqos->ops->track)
      75           0 :                         rqos->ops->track(rqos, rq, bio);
      76           0 :                 rqos = rqos->next;
      77           0 :         } while (rqos);
      78           0 : }
      79             : 
      80           0 : void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio)
      81             : {
      82             :         do {
      83           0 :                 if (rqos->ops->merge)
      84           0 :                         rqos->ops->merge(rqos, rq, bio);
      85           0 :                 rqos = rqos->next;
      86           0 :         } while (rqos);
      87           0 : }
      88             : 
      89           0 : void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio)
      90             : {
      91             :         do {
      92           0 :                 if (rqos->ops->done_bio)
      93           0 :                         rqos->ops->done_bio(rqos, bio);
      94           0 :                 rqos = rqos->next;
      95           0 :         } while (rqos);
      96           0 : }
      97             : 
      98           0 : void __rq_qos_queue_depth_changed(struct rq_qos *rqos)
      99             : {
     100             :         do {
     101           0 :                 if (rqos->ops->queue_depth_changed)
     102           0 :                         rqos->ops->queue_depth_changed(rqos);
     103           0 :                 rqos = rqos->next;
     104           0 :         } while (rqos);
     105           0 : }
     106             : 
     107             : /*
     108             :  * Return true, if we can't increase the depth further by scaling
     109             :  */
     110           0 : bool rq_depth_calc_max_depth(struct rq_depth *rqd)
     111             : {
     112             :         unsigned int depth;
     113           0 :         bool ret = false;
     114             : 
     115             :         /*
     116             :          * For QD=1 devices, this is a special case. It's important for those
     117             :          * to have one request ready when one completes, so force a depth of
     118             :          * 2 for those devices. On the backend, it'll be a depth of 1 anyway,
     119             :          * since the device can't have more than that in flight. If we're
     120             :          * scaling down, then keep a setting of 1/1/1.
     121             :          */
     122           0 :         if (rqd->queue_depth == 1) {
     123           0 :                 if (rqd->scale_step > 0)
     124           0 :                         rqd->max_depth = 1;
     125             :                 else {
     126           0 :                         rqd->max_depth = 2;
     127           0 :                         ret = true;
     128             :                 }
     129             :         } else {
     130             :                 /*
     131             :                  * scale_step == 0 is our default state. If we have suffered
     132             :                  * latency spikes, step will be > 0, and we shrink the
     133             :                  * allowed write depths. If step is < 0, we're only doing
     134             :                  * writes, and we allow a temporarily higher depth to
     135             :                  * increase performance.
     136             :                  */
     137           0 :                 depth = min_t(unsigned int, rqd->default_depth,
     138             :                               rqd->queue_depth);
     139           0 :                 if (rqd->scale_step > 0)
     140           0 :                         depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
     141           0 :                 else if (rqd->scale_step < 0) {
     142           0 :                         unsigned int maxd = 3 * rqd->queue_depth / 4;
     143             : 
     144           0 :                         depth = 1 + ((depth - 1) << -rqd->scale_step);
     145           0 :                         if (depth > maxd) {
     146           0 :                                 depth = maxd;
     147           0 :                                 ret = true;
     148             :                         }
     149             :                 }
     150             : 
     151           0 :                 rqd->max_depth = depth;
     152             :         }
     153             : 
     154           0 :         return ret;
     155             : }
     156             : 
     157             : /* Returns true on success and false if scaling up wasn't possible */
     158           0 : bool rq_depth_scale_up(struct rq_depth *rqd)
     159             : {
     160             :         /*
     161             :          * Hit max in previous round, stop here
     162             :          */
     163           0 :         if (rqd->scaled_max)
     164             :                 return false;
     165             : 
     166           0 :         rqd->scale_step--;
     167             : 
     168           0 :         rqd->scaled_max = rq_depth_calc_max_depth(rqd);
     169           0 :         return true;
     170             : }
     171             : 
     172             : /*
     173             :  * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
     174             :  * had a latency violation. Returns true on success and returns false if
     175             :  * scaling down wasn't possible.
     176             :  */
     177           0 : bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
     178             : {
     179             :         /*
     180             :          * Stop scaling down when we've hit the limit. This also prevents
     181             :          * ->scale_step from going to crazy values, if the device can't
     182             :          * keep up.
     183             :          */
     184           0 :         if (rqd->max_depth == 1)
     185             :                 return false;
     186             : 
     187           0 :         if (rqd->scale_step < 0 && hard_throttle)
     188           0 :                 rqd->scale_step = 0;
     189             :         else
     190           0 :                 rqd->scale_step++;
     191             : 
     192           0 :         rqd->scaled_max = false;
     193           0 :         rq_depth_calc_max_depth(rqd);
     194           0 :         return true;
     195             : }
     196             : 
     197             : struct rq_qos_wait_data {
     198             :         struct wait_queue_entry wq;
     199             :         struct task_struct *task;
     200             :         struct rq_wait *rqw;
     201             :         acquire_inflight_cb_t *cb;
     202             :         void *private_data;
     203             :         bool got_token;
     204             : };
     205             : 
     206           0 : static int rq_qos_wake_function(struct wait_queue_entry *curr,
     207             :                                 unsigned int mode, int wake_flags, void *key)
     208             : {
     209           0 :         struct rq_qos_wait_data *data = container_of(curr,
     210             :                                                      struct rq_qos_wait_data,
     211             :                                                      wq);
     212             : 
     213             :         /*
     214             :          * If we fail to get a budget, return -1 to interrupt the wake up loop
     215             :          * in __wake_up_common.
     216             :          */
     217           0 :         if (!data->cb(data->rqw, data->private_data))
     218             :                 return -1;
     219             : 
     220           0 :         data->got_token = true;
     221           0 :         smp_wmb();
     222           0 :         list_del_init(&curr->entry);
     223           0 :         wake_up_process(data->task);
     224           0 :         return 1;
     225             : }
     226             : 
     227             : /**
     228             :  * rq_qos_wait - throttle on a rqw if we need to
     229             :  * @rqw: rqw to throttle on
     230             :  * @private_data: caller provided specific data
     231             :  * @acquire_inflight_cb: inc the rqw->inflight counter if we can
     232             :  * @cleanup_cb: the callback to cleanup in case we race with a waker
     233             :  *
     234             :  * This provides a uniform place for the rq_qos users to do their throttling.
     235             :  * Since you can end up with a lot of things sleeping at once, this manages the
     236             :  * waking up based on the resources available.  The acquire_inflight_cb should
     237             :  * inc the rqw->inflight if we have the ability to do so, or return false if not
     238             :  * and then we will sleep until the room becomes available.
     239             :  *
     240             :  * cleanup_cb is in case that we race with a waker and need to cleanup the
     241             :  * inflight count accordingly.
     242             :  */
     243           0 : void rq_qos_wait(struct rq_wait *rqw, void *private_data,
     244             :                  acquire_inflight_cb_t *acquire_inflight_cb,
     245             :                  cleanup_cb_t *cleanup_cb)
     246             : {
     247           0 :         struct rq_qos_wait_data data = {
     248             :                 .wq = {
     249             :                         .func   = rq_qos_wake_function,
     250             :                         .entry  = LIST_HEAD_INIT(data.wq.entry),
     251             :                 },
     252           0 :                 .task = current,
     253             :                 .rqw = rqw,
     254             :                 .cb = acquire_inflight_cb,
     255             :                 .private_data = private_data,
     256             :         };
     257             :         bool has_sleeper;
     258             : 
     259           0 :         has_sleeper = wq_has_sleeper(&rqw->wait);
     260           0 :         if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
     261           0 :                 return;
     262             : 
     263           0 :         has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq,
     264           0 :                                                  TASK_UNINTERRUPTIBLE);
     265             :         do {
     266             :                 /* The memory barrier in set_task_state saves us here. */
     267           0 :                 if (data.got_token)
     268             :                         break;
     269           0 :                 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
     270           0 :                         finish_wait(&rqw->wait, &data.wq);
     271             : 
     272             :                         /*
     273             :                          * We raced with wbt_wake_function() getting a token,
     274             :                          * which means we now have two. Put our local token
     275             :                          * and wake anyone else potentially waiting for one.
     276             :                          */
     277           0 :                         smp_rmb();
     278           0 :                         if (data.got_token)
     279           0 :                                 cleanup_cb(rqw, private_data);
     280             :                         break;
     281             :                 }
     282           0 :                 io_schedule();
     283           0 :                 has_sleeper = true;
     284           0 :                 set_current_state(TASK_UNINTERRUPTIBLE);
     285             :         } while (1);
     286           0 :         finish_wait(&rqw->wait, &data.wq);
     287             : }
     288             : 
     289           0 : void rq_qos_exit(struct request_queue *q)
     290             : {
     291           0 :         mutex_lock(&q->rq_qos_mutex);
     292           0 :         while (q->rq_qos) {
     293           0 :                 struct rq_qos *rqos = q->rq_qos;
     294           0 :                 q->rq_qos = rqos->next;
     295           0 :                 rqos->ops->exit(rqos);
     296             :         }
     297           0 :         mutex_unlock(&q->rq_qos_mutex);
     298           0 : }
     299             : 
     300           0 : int rq_qos_add(struct rq_qos *rqos, struct gendisk *disk, enum rq_qos_id id,
     301             :                 const struct rq_qos_ops *ops)
     302             : {
     303           0 :         struct request_queue *q = disk->queue;
     304             : 
     305             :         lockdep_assert_held(&q->rq_qos_mutex);
     306             : 
     307           0 :         rqos->disk = disk;
     308           0 :         rqos->id = id;
     309           0 :         rqos->ops = ops;
     310             : 
     311             :         /*
     312             :          * No IO can be in-flight when adding rqos, so freeze queue, which
     313             :          * is fine since we only support rq_qos for blk-mq queue.
     314             :          */
     315           0 :         blk_mq_freeze_queue(q);
     316             : 
     317           0 :         if (rq_qos_id(q, rqos->id))
     318             :                 goto ebusy;
     319           0 :         rqos->next = q->rq_qos;
     320           0 :         q->rq_qos = rqos;
     321             : 
     322           0 :         blk_mq_unfreeze_queue(q);
     323             : 
     324           0 :         if (rqos->ops->debugfs_attrs) {
     325           0 :                 mutex_lock(&q->debugfs_mutex);
     326           0 :                 blk_mq_debugfs_register_rqos(rqos);
     327           0 :                 mutex_unlock(&q->debugfs_mutex);
     328             :         }
     329             : 
     330             :         return 0;
     331             : ebusy:
     332           0 :         blk_mq_unfreeze_queue(q);
     333           0 :         return -EBUSY;
     334             : }
     335             : 
     336           0 : void rq_qos_del(struct rq_qos *rqos)
     337             : {
     338           0 :         struct request_queue *q = rqos->disk->queue;
     339             :         struct rq_qos **cur;
     340             : 
     341             :         lockdep_assert_held(&q->rq_qos_mutex);
     342             : 
     343           0 :         blk_mq_freeze_queue(q);
     344           0 :         for (cur = &q->rq_qos; *cur; cur = &(*cur)->next) {
     345           0 :                 if (*cur == rqos) {
     346           0 :                         *cur = rqos->next;
     347           0 :                         break;
     348             :                 }
     349             :         }
     350           0 :         blk_mq_unfreeze_queue(q);
     351             : 
     352           0 :         mutex_lock(&q->debugfs_mutex);
     353           0 :         blk_mq_debugfs_unregister_rqos(rqos);
     354           0 :         mutex_unlock(&q->debugfs_mutex);
     355           0 : }