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 wake_up_process(data->task);
223 list_del_init_careful(&curr->entry);
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_task_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 }
356
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.