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 for (;;) { 14 unsigned int old; 15 16 if (cur >= below) 17 return false; 18 old = atomic_cmpxchg(v, cur, cur + 1); 19 if (old == cur) 20 break; 21 cur = old; 22 } 23 24 return true; 25 } 26 27 bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit) 28 { 29 return atomic_inc_below(&rq_wait->inflight, limit); 30 } 31 32 void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio) 33 { 34 do { 35 if (rqos->ops->cleanup) 36 rqos->ops->cleanup(rqos, bio); 37 rqos = rqos->next; 38 } while (rqos); 39 } 40 41 void __rq_qos_done(struct rq_qos *rqos, struct request *rq) 42 { 43 do { 44 if (rqos->ops->done) 45 rqos->ops->done(rqos, rq); 46 rqos = rqos->next; 47 } while (rqos); 48 } 49 50 void __rq_qos_issue(struct rq_qos *rqos, struct request *rq) 51 { 52 do { 53 if (rqos->ops->issue) 54 rqos->ops->issue(rqos, rq); 55 rqos = rqos->next; 56 } while (rqos); 57 } 58 59 void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq) 60 { 61 do { 62 if (rqos->ops->requeue) 63 rqos->ops->requeue(rqos, rq); 64 rqos = rqos->next; 65 } while (rqos); 66 } 67 68 void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio) 69 { 70 do { 71 if (rqos->ops->throttle) 72 rqos->ops->throttle(rqos, bio); 73 rqos = rqos->next; 74 } while (rqos); 75 } 76 77 void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio) 78 { 79 do { 80 if (rqos->ops->track) 81 rqos->ops->track(rqos, rq, bio); 82 rqos = rqos->next; 83 } while (rqos); 84 } 85 86 void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio) 87 { 88 do { 89 if (rqos->ops->merge) 90 rqos->ops->merge(rqos, rq, bio); 91 rqos = rqos->next; 92 } while (rqos); 93 } 94 95 void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio) 96 { 97 do { 98 if (rqos->ops->done_bio) 99 rqos->ops->done_bio(rqos, bio); 100 rqos = rqos->next; 101 } while (rqos); 102 } 103 104 void __rq_qos_queue_depth_changed(struct rq_qos *rqos) 105 { 106 do { 107 if (rqos->ops->queue_depth_changed) 108 rqos->ops->queue_depth_changed(rqos); 109 rqos = rqos->next; 110 } while (rqos); 111 } 112 113 /* 114 * Return true, if we can't increase the depth further by scaling 115 */ 116 bool rq_depth_calc_max_depth(struct rq_depth *rqd) 117 { 118 unsigned int depth; 119 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 if (rqd->queue_depth == 1) { 129 if (rqd->scale_step > 0) 130 rqd->max_depth = 1; 131 else { 132 rqd->max_depth = 2; 133 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 depth = min_t(unsigned int, rqd->default_depth, 144 rqd->queue_depth); 145 if (rqd->scale_step > 0) 146 depth = 1 + ((depth - 1) >> min(31, rqd->scale_step)); 147 else if (rqd->scale_step < 0) { 148 unsigned int maxd = 3 * rqd->queue_depth / 4; 149 150 depth = 1 + ((depth - 1) << -rqd->scale_step); 151 if (depth > maxd) { 152 depth = maxd; 153 ret = true; 154 } 155 } 156 157 rqd->max_depth = depth; 158 } 159 160 return ret; 161 } 162 163 /* Returns true on success and false if scaling up wasn't possible */ 164 bool rq_depth_scale_up(struct rq_depth *rqd) 165 { 166 /* 167 * Hit max in previous round, stop here 168 */ 169 if (rqd->scaled_max) 170 return false; 171 172 rqd->scale_step--; 173 174 rqd->scaled_max = rq_depth_calc_max_depth(rqd); 175 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 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 if (rqd->max_depth == 1) 191 return false; 192 193 if (rqd->scale_step < 0 && hard_throttle) 194 rqd->scale_step = 0; 195 else 196 rqd->scale_step++; 197 198 rqd->scaled_max = false; 199 rq_depth_calc_max_depth(rqd); 200 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 static int rq_qos_wake_function(struct wait_queue_entry *curr, 213 unsigned int mode, int wake_flags, void *key) 214 { 215 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 if (!data->cb(data->rqw, data->private_data)) 224 return -1; 225 226 data->got_token = true; 227 smp_wmb(); 228 list_del_init(&curr->entry); 229 wake_up_process(data->task); 230 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 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 struct rq_qos_wait_data data = { 254 .wq = { 255 .func = rq_qos_wake_function, 256 .entry = LIST_HEAD_INIT(data.wq.entry), 257 }, 258 .task = current, 259 .rqw = rqw, 260 .cb = acquire_inflight_cb, 261 .private_data = private_data, 262 }; 263 bool has_sleeper; 264 265 has_sleeper = wq_has_sleeper(&rqw->wait); 266 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) 267 return; 268 269 has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq, 270 TASK_UNINTERRUPTIBLE); 271 do { 272 /* The memory barrier in set_task_state saves us here. */ 273 if (data.got_token) 274 break; 275 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) { 276 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 smp_rmb(); 284 if (data.got_token) 285 cleanup_cb(rqw, private_data); 286 break; 287 } 288 io_schedule(); 289 has_sleeper = true; 290 set_current_state(TASK_UNINTERRUPTIBLE); 291 } while (1); 292 finish_wait(&rqw->wait, &data.wq); 293 } 294 295 void rq_qos_exit(struct request_queue *q) 296 { 297 blk_mq_debugfs_unregister_queue_rqos(q); 298 299 while (q->rq_qos) { 300 struct rq_qos *rqos = q->rq_qos; 301 q->rq_qos = rqos->next; 302 rqos->ops->exit(rqos); 303 } 304 } 305