block/blk-rq-qos.c

   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         unsigned int cur = atomic_read(v);
  12
  13         do {
  14                 if (cur >= below)
  15                         return false;
  16         } while (!atomic_try_cmpxchg(v, &cur, cur + 1));
  17
  18         return true;
  19 }
  20
  21 bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit)
  22 {
  23         return atomic_inc_below(&rq_wait->inflight, limit);
  24 }
  25
  26 void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio)
  27 {
  28         do {
  29                 if (rqos->ops->cleanup)
  30                         rqos->ops->cleanup(rqos, bio);
  31                 rqos = rqos->next;
  32         } while (rqos);
  33 }
  34
  35 void __rq_qos_done(struct rq_qos *rqos, struct request *rq)
  36 {
  37         do {
  38                 if (rqos->ops->done)
  39                         rqos->ops->done(rqos, rq);
  40                 rqos = rqos->next;
  41         } while (rqos);
  42 }
  43
  44 void __rq_qos_issue(struct rq_qos *rqos, struct request *rq)
  45 {
  46         do {
  47                 if (rqos->ops->issue)
  48                         rqos->ops->issue(rqos, rq);
  49                 rqos = rqos->next;
  50         } while (rqos);
  51 }
  52
  53 void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq)
  54 {
  55         do {
  56                 if (rqos->ops->requeue)
  57                         rqos->ops->requeue(rqos, rq);
  58                 rqos = rqos->next;
  59         } while (rqos);
  60 }
  61
  62 void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio)
  63 {
  64         do {
  65                 if (rqos->ops->throttle)
  66                         rqos->ops->throttle(rqos, bio);
  67                 rqos = rqos->next;
  68         } while (rqos);
  69 }
  70
  71 void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
  72 {
  73         do {
  74                 if (rqos->ops->track)
  75                         rqos->ops->track(rqos, rq, bio);
  76                 rqos = rqos->next;
  77         } while (rqos);
  78 }
  79
  80 void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio)
  81 {
  82         do {
  83                 if (rqos->ops->merge)
  84                         rqos->ops->merge(rqos, rq, bio);
  85                 rqos = rqos->next;
  86         } while (rqos);
  87 }
  88
  89 void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio)
  90 {
  91         do {
  92                 if (rqos->ops->done_bio)
  93                         rqos->ops->done_bio(rqos, bio);
  94                 rqos = rqos->next;
  95         } while (rqos);
  96 }
  97
  98 void __rq_qos_queue_depth_changed(struct rq_qos *rqos)
  99 {
 100         do {
 101                 if (rqos->ops->queue_depth_changed)
 102                         rqos->ops->queue_depth_changed(rqos);
 103                 rqos = rqos->next;
 104         } while (rqos);
 105 }
 106
 107 /*
 108  * Return true, if we can't increase the depth further by scaling
 109  */
 110 bool rq_depth_calc_max_depth(struct rq_depth *rqd)
 111 {
 112         unsigned int depth;
 113         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         if (rqd->queue_depth == 1) {
 123                 if (rqd->scale_step > 0)
 124                         rqd->max_depth = 1;
 125                 else {
 126                         rqd->max_depth = 2;
 127                         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                 depth = min_t(unsigned int, rqd->default_depth,
 138                               rqd->queue_depth);
 139                 if (rqd->scale_step > 0)
 140                         depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
 141                 else if (rqd->scale_step < 0) {
 142                         unsigned int maxd = 3 * rqd->queue_depth / 4;
 143
 144                         depth = 1 + ((depth - 1) << -rqd->scale_step);
 145                         if (depth > maxd) {
 146                                 depth = maxd;
 147                                 ret = true;
 148                         }
 149                 }
 150
 151                 rqd->max_depth = depth;
 152         }
 153
 154         return ret;
 155 }
 156
 157 /* Returns true on success and false if scaling up wasn't possible */
 158 bool rq_depth_scale_up(struct rq_depth *rqd)
 159 {
 160         /*
 161          * Hit max in previous round, stop here
 162          */
 163         if (rqd->scaled_max)
 164                 return false;
 165
 166         rqd->scale_step--;
 167
 168         rqd->scaled_max = rq_depth_calc_max_depth(rqd);
 169         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 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         if (rqd->max_depth == 1)
 185                 return false;
 186
 187         if (rqd->scale_step < 0 && hard_throttle)
 188                 rqd->scale_step = 0;
 189         else
 190                 rqd->scale_step++;
 191
 192         rqd->scaled_max = false;
 193         rq_depth_calc_max_depth(rqd);
 194         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 static int rq_qos_wake_function(struct wait_queue_entry *curr,
 207                                 unsigned int mode, int wake_flags, void *key)
 208 {
 209         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         if (!data->cb(data->rqw, data->private_data))
 218                 return -1;
 219
 220         data->got_token = true;
 221         smp_wmb();
 222         list_del_init(&curr->entry);
 223         wake_up_process(data->task);
 224         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 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         struct rq_qos_wait_data data = {
 248                 .wq = {
 249                         .func   = rq_qos_wake_function,
 250                         .entry  = LIST_HEAD_INIT(data.wq.entry),
 251                 },
 252                 .task = current,
 253                 .rqw = rqw,
 254                 .cb = acquire_inflight_cb,
 255                 .private_data = private_data,
 256         };
 257         bool has_sleeper;
 258
 259         has_sleeper = wq_has_sleeper(&rqw->wait);
 260         if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
 261                 return;
 262
 263         has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq,
 264                                                  TASK_UNINTERRUPTIBLE);
 265         do {
 266                 /* The memory barrier in set_current_state saves us here. */
 267                 if (data.got_token)
 268                         break;
 269                 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
 270                         finish_wait(&rqw->wait, &data.wq);
 271
 272                         /*
 273                          * We raced with rq_qos_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                         smp_rmb();
 278                         if (data.got_token)
 279                                 cleanup_cb(rqw, private_data);
 280                         break;
 281                 }
 282                 io_schedule();
 283                 has_sleeper = true;
 284                 set_current_state(TASK_UNINTERRUPTIBLE);
 285         } while (1);
 286         finish_wait(&rqw->wait, &data.wq);
 287 }
 288
 289 void rq_qos_exit(struct request_queue *q)
 290 {
 291         mutex_lock(&q->rq_qos_mutex);
 292         while (q->rq_qos) {
 293                 struct rq_qos *rqos = q->rq_qos;
 294                 q->rq_qos = rqos->next;
 295                 rqos->ops->exit(rqos);
 296         }
 297         mutex_unlock(&q->rq_qos_mutex);
 298 }
 299
 300 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         struct request_queue *q = disk->queue;
 304
 305         lockdep_assert_held(&q->rq_qos_mutex);
 306
 307         rqos->disk = disk;
 308         rqos->id = id;
 309         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         blk_mq_freeze_queue(q);
 316
 317         if (rq_qos_id(q, rqos->id))
 318                 goto ebusy;
 319         rqos->next = q->rq_qos;
 320         q->rq_qos = rqos;
 321
 322         blk_mq_unfreeze_queue(q);
 323
 324         if (rqos->ops->debugfs_attrs) {
 325                 mutex_lock(&q->debugfs_mutex);
 326                 blk_mq_debugfs_register_rqos(rqos);
 327                 mutex_unlock(&q->debugfs_mutex);
 328         }
 329
 330         return 0;
 331 ebusy:
 332         blk_mq_unfreeze_queue(q);
 333         return -EBUSY;
 334 }
 335
 336 void rq_qos_del(struct rq_qos *rqos)
 337 {
 338         struct request_queue *q = rqos->disk->queue;
 339         struct rq_qos **cur;
 340
 341         lockdep_assert_held(&q->rq_qos_mutex);
 342
 343         blk_mq_freeze_queue(q);
 344         for (cur = &q->rq_qos; *cur; cur = &(*cur)->next) {
 345                 if (*cur == rqos) {
 346                         *cur = rqos->next;
 347                         break;
 348                 }
 349         }
 350         blk_mq_unfreeze_queue(q);
 351
 352         mutex_lock(&q->debugfs_mutex);
 353         blk_mq_debugfs_unregister_rqos(rqos);
 354         mutex_unlock(&q->debugfs_mutex);
 355 }