treewide: remove SPDX "WITH Linux-syscall-note" from kernel-space headers
[sfrench/cifs-2.6.git] / 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         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_done_bio(struct rq_qos *rqos, struct bio *bio)
87 {
88         do {
89                 if (rqos->ops->done_bio)
90                         rqos->ops->done_bio(rqos, bio);
91                 rqos = rqos->next;
92         } while (rqos);
93 }
94
95 /*
96  * Return true, if we can't increase the depth further by scaling
97  */
98 bool rq_depth_calc_max_depth(struct rq_depth *rqd)
99 {
100         unsigned int depth;
101         bool ret = false;
102
103         /*
104          * For QD=1 devices, this is a special case. It's important for those
105          * to have one request ready when one completes, so force a depth of
106          * 2 for those devices. On the backend, it'll be a depth of 1 anyway,
107          * since the device can't have more than that in flight. If we're
108          * scaling down, then keep a setting of 1/1/1.
109          */
110         if (rqd->queue_depth == 1) {
111                 if (rqd->scale_step > 0)
112                         rqd->max_depth = 1;
113                 else {
114                         rqd->max_depth = 2;
115                         ret = true;
116                 }
117         } else {
118                 /*
119                  * scale_step == 0 is our default state. If we have suffered
120                  * latency spikes, step will be > 0, and we shrink the
121                  * allowed write depths. If step is < 0, we're only doing
122                  * writes, and we allow a temporarily higher depth to
123                  * increase performance.
124                  */
125                 depth = min_t(unsigned int, rqd->default_depth,
126                               rqd->queue_depth);
127                 if (rqd->scale_step > 0)
128                         depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
129                 else if (rqd->scale_step < 0) {
130                         unsigned int maxd = 3 * rqd->queue_depth / 4;
131
132                         depth = 1 + ((depth - 1) << -rqd->scale_step);
133                         if (depth > maxd) {
134                                 depth = maxd;
135                                 ret = true;
136                         }
137                 }
138
139                 rqd->max_depth = depth;
140         }
141
142         return ret;
143 }
144
145 void rq_depth_scale_up(struct rq_depth *rqd)
146 {
147         /*
148          * Hit max in previous round, stop here
149          */
150         if (rqd->scaled_max)
151                 return;
152
153         rqd->scale_step--;
154
155         rqd->scaled_max = rq_depth_calc_max_depth(rqd);
156 }
157
158 /*
159  * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
160  * had a latency violation.
161  */
162 void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
163 {
164         /*
165          * Stop scaling down when we've hit the limit. This also prevents
166          * ->scale_step from going to crazy values, if the device can't
167          * keep up.
168          */
169         if (rqd->max_depth == 1)
170                 return;
171
172         if (rqd->scale_step < 0 && hard_throttle)
173                 rqd->scale_step = 0;
174         else
175                 rqd->scale_step++;
176
177         rqd->scaled_max = false;
178         rq_depth_calc_max_depth(rqd);
179 }
180
181 struct rq_qos_wait_data {
182         struct wait_queue_entry wq;
183         struct task_struct *task;
184         struct rq_wait *rqw;
185         acquire_inflight_cb_t *cb;
186         void *private_data;
187         bool got_token;
188 };
189
190 static int rq_qos_wake_function(struct wait_queue_entry *curr,
191                                 unsigned int mode, int wake_flags, void *key)
192 {
193         struct rq_qos_wait_data *data = container_of(curr,
194                                                      struct rq_qos_wait_data,
195                                                      wq);
196
197         /*
198          * If we fail to get a budget, return -1 to interrupt the wake up loop
199          * in __wake_up_common.
200          */
201         if (!data->cb(data->rqw, data->private_data))
202                 return -1;
203
204         data->got_token = true;
205         list_del_init(&curr->entry);
206         wake_up_process(data->task);
207         return 1;
208 }
209
210 /**
211  * rq_qos_wait - throttle on a rqw if we need to
212  * @private_data - caller provided specific data
213  * @acquire_inflight_cb - inc the rqw->inflight counter if we can
214  * @cleanup_cb - the callback to cleanup in case we race with a waker
215  *
216  * This provides a uniform place for the rq_qos users to do their throttling.
217  * Since you can end up with a lot of things sleeping at once, this manages the
218  * waking up based on the resources available.  The acquire_inflight_cb should
219  * inc the rqw->inflight if we have the ability to do so, or return false if not
220  * and then we will sleep until the room becomes available.
221  *
222  * cleanup_cb is in case that we race with a waker and need to cleanup the
223  * inflight count accordingly.
224  */
225 void rq_qos_wait(struct rq_wait *rqw, void *private_data,
226                  acquire_inflight_cb_t *acquire_inflight_cb,
227                  cleanup_cb_t *cleanup_cb)
228 {
229         struct rq_qos_wait_data data = {
230                 .wq = {
231                         .func   = rq_qos_wake_function,
232                         .entry  = LIST_HEAD_INIT(data.wq.entry),
233                 },
234                 .task = current,
235                 .rqw = rqw,
236                 .cb = acquire_inflight_cb,
237                 .private_data = private_data,
238         };
239         bool has_sleeper;
240
241         has_sleeper = wq_has_sleeper(&rqw->wait);
242         if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
243                 return;
244
245         prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE);
246         do {
247                 if (data.got_token)
248                         break;
249                 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
250                         finish_wait(&rqw->wait, &data.wq);
251
252                         /*
253                          * We raced with wbt_wake_function() getting a token,
254                          * which means we now have two. Put our local token
255                          * and wake anyone else potentially waiting for one.
256                          */
257                         if (data.got_token)
258                                 cleanup_cb(rqw, private_data);
259                         break;
260                 }
261                 io_schedule();
262                 has_sleeper = false;
263         } while (1);
264         finish_wait(&rqw->wait, &data.wq);
265 }
266
267 void rq_qos_exit(struct request_queue *q)
268 {
269         blk_mq_debugfs_unregister_queue_rqos(q);
270
271         while (q->rq_qos) {
272                 struct rq_qos *rqos = q->rq_qos;
273                 q->rq_qos = rqos->next;
274                 rqos->ops->exit(rqos);
275         }
276 }