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TOMOYO Linux Cross Reference
Linux/block/blk-iocost.c

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  1 /* SPDX-License-Identifier: GPL-2.0
  2  *
  3  * IO cost model based controller.
  4  *
  5  * Copyright (C) 2019 Tejun Heo <tj@kernel.org>
  6  * Copyright (C) 2019 Andy Newell <newella@fb.com>
  7  * Copyright (C) 2019 Facebook
  8  *
  9  * One challenge of controlling IO resources is the lack of trivially
 10  * observable cost metric.  This is distinguished from CPU and memory where
 11  * wallclock time and the number of bytes can serve as accurate enough
 12  * approximations.
 13  *
 14  * Bandwidth and iops are the most commonly used metrics for IO devices but
 15  * depending on the type and specifics of the device, different IO patterns
 16  * easily lead to multiple orders of magnitude variations rendering them
 17  * useless for the purpose of IO capacity distribution.  While on-device
 18  * time, with a lot of clutches, could serve as a useful approximation for
 19  * non-queued rotational devices, this is no longer viable with modern
 20  * devices, even the rotational ones.
 21  *
 22  * While there is no cost metric we can trivially observe, it isn't a
 23  * complete mystery.  For example, on a rotational device, seek cost
 24  * dominates while a contiguous transfer contributes a smaller amount
 25  * proportional to the size.  If we can characterize at least the relative
 26  * costs of these different types of IOs, it should be possible to
 27  * implement a reasonable work-conserving proportional IO resource
 28  * distribution.
 29  *
 30  * 1. IO Cost Model
 31  *
 32  * IO cost model estimates the cost of an IO given its basic parameters and
 33  * history (e.g. the end sector of the last IO).  The cost is measured in
 34  * device time.  If a given IO is estimated to cost 10ms, the device should
 35  * be able to process ~100 of those IOs in a second.
 36  *
 37  * Currently, there's only one builtin cost model - linear.  Each IO is
 38  * classified as sequential or random and given a base cost accordingly.
 39  * On top of that, a size cost proportional to the length of the IO is
 40  * added.  While simple, this model captures the operational
 41  * characteristics of a wide varienty of devices well enough.  Default
 42  * paramters for several different classes of devices are provided and the
 43  * parameters can be configured from userspace via
 44  * /sys/fs/cgroup/io.cost.model.
 45  *
 46  * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate
 47  * device-specific coefficients.
 48  *
 49  * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate
 50  * device-specific coefficients.
 51  *
 52  * 2. Control Strategy
 53  *
 54  * The device virtual time (vtime) is used as the primary control metric.
 55  * The control strategy is composed of the following three parts.
 56  *
 57  * 2-1. Vtime Distribution
 58  *
 59  * When a cgroup becomes active in terms of IOs, its hierarchical share is
 60  * calculated.  Please consider the following hierarchy where the numbers
 61  * inside parentheses denote the configured weights.
 62  *
 63  *           root
 64  *         /       \
 65  *      A (w:100)  B (w:300)
 66  *      /       \
 67  *  A0 (w:100)  A1 (w:100)
 68  *
 69  * If B is idle and only A0 and A1 are actively issuing IOs, as the two are
 70  * of equal weight, each gets 50% share.  If then B starts issuing IOs, B
 71  * gets 300/(100+300) or 75% share, and A0 and A1 equally splits the rest,
 72  * 12.5% each.  The distribution mechanism only cares about these flattened
 73  * shares.  They're called hweights (hierarchical weights) and always add
 74  * upto 1 (HWEIGHT_WHOLE).
 75  *
 76  * A given cgroup's vtime runs slower in inverse proportion to its hweight.
 77  * For example, with 12.5% weight, A0's time runs 8 times slower (100/12.5)
 78  * against the device vtime - an IO which takes 10ms on the underlying
 79  * device is considered to take 80ms on A0.
 80  *
 81  * This constitutes the basis of IO capacity distribution.  Each cgroup's
 82  * vtime is running at a rate determined by its hweight.  A cgroup tracks
 83  * the vtime consumed by past IOs and can issue a new IO iff doing so
 84  * wouldn't outrun the current device vtime.  Otherwise, the IO is
 85  * suspended until the vtime has progressed enough to cover it.
 86  *
 87  * 2-2. Vrate Adjustment
 88  *
 89  * It's unrealistic to expect the cost model to be perfect.  There are too
 90  * many devices and even on the same device the overall performance
 91  * fluctuates depending on numerous factors such as IO mixture and device
 92  * internal garbage collection.  The controller needs to adapt dynamically.
 93  *
 94  * This is achieved by adjusting the overall IO rate according to how busy
 95  * the device is.  If the device becomes overloaded, we're sending down too
 96  * many IOs and should generally slow down.  If there are waiting issuers
 97  * but the device isn't saturated, we're issuing too few and should
 98  * generally speed up.
 99  *
100  * To slow down, we lower the vrate - the rate at which the device vtime
101  * passes compared to the wall clock.  For example, if the vtime is running
102  * at the vrate of 75%, all cgroups added up would only be able to issue
103  * 750ms worth of IOs per second, and vice-versa for speeding up.
104  *
105  * Device business is determined using two criteria - rq wait and
106  * completion latencies.
107  *
108  * When a device gets saturated, the on-device and then the request queues
109  * fill up and a bio which is ready to be issued has to wait for a request
110  * to become available.  When this delay becomes noticeable, it's a clear
111  * indication that the device is saturated and we lower the vrate.  This
112  * saturation signal is fairly conservative as it only triggers when both
113  * hardware and software queues are filled up, and is used as the default
114  * busy signal.
115  *
116  * As devices can have deep queues and be unfair in how the queued commands
117  * are executed, soley depending on rq wait may not result in satisfactory
118  * control quality.  For a better control quality, completion latency QoS
119  * parameters can be configured so that the device is considered saturated
120  * if N'th percentile completion latency rises above the set point.
121  *
122  * The completion latency requirements are a function of both the
123  * underlying device characteristics and the desired IO latency quality of
124  * service.  There is an inherent trade-off - the tighter the latency QoS,
125  * the higher the bandwidth lossage.  Latency QoS is disabled by default
126  * and can be set through /sys/fs/cgroup/io.cost.qos.
127  *
128  * 2-3. Work Conservation
129  *
130  * Imagine two cgroups A and B with equal weights.  A is issuing a small IO
131  * periodically while B is sending out enough parallel IOs to saturate the
132  * device on its own.  Let's say A's usage amounts to 100ms worth of IO
133  * cost per second, i.e., 10% of the device capacity.  The naive
134  * distribution of half and half would lead to 60% utilization of the
135  * device, a significant reduction in the total amount of work done
136  * compared to free-for-all competition.  This is too high a cost to pay
137  * for IO control.
138  *
139  * To conserve the total amount of work done, we keep track of how much
140  * each active cgroup is actually using and yield part of its weight if
141  * there are other cgroups which can make use of it.  In the above case,
142  * A's weight will be lowered so that it hovers above the actual usage and
143  * B would be able to use the rest.
144  *
145  * As we don't want to penalize a cgroup for donating its weight, the
146  * surplus weight adjustment factors in a margin and has an immediate
147  * snapback mechanism in case the cgroup needs more IO vtime for itself.
148  *
149  * Note that adjusting down surplus weights has the same effects as
150  * accelerating vtime for other cgroups and work conservation can also be
151  * implemented by adjusting vrate dynamically.  However, squaring who can
152  * donate and should take back how much requires hweight propagations
153  * anyway making it easier to implement and understand as a separate
154  * mechanism.
155  *
156  * 3. Monitoring
157  *
158  * Instead of debugfs or other clumsy monitoring mechanisms, this
159  * controller uses a drgn based monitoring script -
160  * tools/cgroup/iocost_monitor.py.  For details on drgn, please see
161  * https://github.com/osandov/drgn.  The ouput looks like the following.
162  *
163  *  sdb RUN   per=300ms cur_per=234.218:v203.695 busy= +1 vrate= 62.12%
164  *                 active      weight      hweight% inflt% dbt  delay usages%
165  *  test/a              *    50/   50  33.33/ 33.33  27.65   2  0*041 033:033:033
166  *  test/b              *   100/  100  66.67/ 66.67  17.56   0  0*000 066:079:077
167  *
168  * - per        : Timer period
169  * - cur_per    : Internal wall and device vtime clock
170  * - vrate      : Device virtual time rate against wall clock
171  * - weight     : Surplus-adjusted and configured weights
172  * - hweight    : Surplus-adjusted and configured hierarchical weights
173  * - inflt      : The percentage of in-flight IO cost at the end of last period
174  * - del_ms     : Deferred issuer delay induction level and duration
175  * - usages     : Usage history
176  */
177 
178 #include <linux/kernel.h>
179 #include <linux/module.h>
180 #include <linux/timer.h>
181 #include <linux/time64.h>
182 #include <linux/parser.h>
183 #include <linux/sched/signal.h>
184 #include <linux/blk-cgroup.h>
185 #include "blk-rq-qos.h"
186 #include "blk-stat.h"
187 #include "blk-wbt.h"
188 
189 #ifdef CONFIG_TRACEPOINTS
190 
191 /* copied from TRACE_CGROUP_PATH, see cgroup-internal.h */
192 #define TRACE_IOCG_PATH_LEN 1024
193 static DEFINE_SPINLOCK(trace_iocg_path_lock);
194 static char trace_iocg_path[TRACE_IOCG_PATH_LEN];
195 
196 #define TRACE_IOCG_PATH(type, iocg, ...)                                        \
197         do {                                                                    \
198                 unsigned long flags;                                            \
199                 if (trace_iocost_##type##_enabled()) {                          \
200                         spin_lock_irqsave(&trace_iocg_path_lock, flags);        \
201                         cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup,      \
202                                     trace_iocg_path, TRACE_IOCG_PATH_LEN);      \
203                         trace_iocost_##type(iocg, trace_iocg_path,              \
204                                               ##__VA_ARGS__);                   \
205                         spin_unlock_irqrestore(&trace_iocg_path_lock, flags);   \
206                 }                                                               \
207         } while (0)
208 
209 #else   /* CONFIG_TRACE_POINTS */
210 #define TRACE_IOCG_PATH(type, iocg, ...)        do { } while (0)
211 #endif  /* CONFIG_TRACE_POINTS */
212 
213 enum {
214         MILLION                 = 1000000,
215 
216         /* timer period is calculated from latency requirements, bound it */
217         MIN_PERIOD              = USEC_PER_MSEC,
218         MAX_PERIOD              = USEC_PER_SEC,
219 
220         /*
221          * A cgroup's vtime can run 50% behind the device vtime, which
222          * serves as its IO credit buffer.  Surplus weight adjustment is
223          * immediately canceled if the vtime margin runs below 10%.
224          */
225         MARGIN_PCT              = 50,
226         INUSE_MARGIN_PCT        = 10,
227 
228         /* Have some play in waitq timer operations */
229         WAITQ_TIMER_MARGIN_PCT  = 5,
230 
231         /*
232          * vtime can wrap well within a reasonable uptime when vrate is
233          * consistently raised.  Don't trust recorded cgroup vtime if the
234          * period counter indicates that it's older than 5mins.
235          */
236         VTIME_VALID_DUR         = 300 * USEC_PER_SEC,
237 
238         /*
239          * Remember the past three non-zero usages and use the max for
240          * surplus calculation.  Three slots guarantee that we remember one
241          * full period usage from the last active stretch even after
242          * partial deactivation and re-activation periods.  Don't start
243          * giving away weight before collecting two data points to prevent
244          * hweight adjustments based on one partial activation period.
245          */
246         NR_USAGE_SLOTS          = 3,
247         MIN_VALID_USAGES        = 2,
248 
249         /* 1/64k is granular enough and can easily be handled w/ u32 */
250         HWEIGHT_WHOLE           = 1 << 16,
251 
252         /*
253          * As vtime is used to calculate the cost of each IO, it needs to
254          * be fairly high precision.  For example, it should be able to
255          * represent the cost of a single page worth of discard with
256          * suffificient accuracy.  At the same time, it should be able to
257          * represent reasonably long enough durations to be useful and
258          * convenient during operation.
259          *
260          * 1s worth of vtime is 2^37.  This gives us both sub-nanosecond
261          * granularity and days of wrap-around time even at extreme vrates.
262          */
263         VTIME_PER_SEC_SHIFT     = 37,
264         VTIME_PER_SEC           = 1LLU << VTIME_PER_SEC_SHIFT,
265         VTIME_PER_USEC          = VTIME_PER_SEC / USEC_PER_SEC,
266 
267         /* bound vrate adjustments within two orders of magnitude */
268         VRATE_MIN_PPM           = 10000,        /* 1% */
269         VRATE_MAX_PPM           = 100000000,    /* 10000% */
270 
271         VRATE_MIN               = VTIME_PER_USEC * VRATE_MIN_PPM / MILLION,
272         VRATE_CLAMP_ADJ_PCT     = 4,
273 
274         /* if IOs end up waiting for requests, issue less */
275         RQ_WAIT_BUSY_PCT        = 5,
276 
277         /* unbusy hysterisis */
278         UNBUSY_THR_PCT          = 75,
279 
280         /* don't let cmds which take a very long time pin lagging for too long */
281         MAX_LAGGING_PERIODS     = 10,
282 
283         /*
284          * If usage% * 1.25 + 2% is lower than hweight% by more than 3%,
285          * donate the surplus.
286          */
287         SURPLUS_SCALE_PCT       = 125,                  /* * 125% */
288         SURPLUS_SCALE_ABS       = HWEIGHT_WHOLE / 50,   /* + 2% */
289         SURPLUS_MIN_ADJ_DELTA   = HWEIGHT_WHOLE / 33,   /* 3% */
290 
291         /* switch iff the conditions are met for longer than this */
292         AUTOP_CYCLE_NSEC        = 10LLU * NSEC_PER_SEC,
293 
294         /*
295          * Count IO size in 4k pages.  The 12bit shift helps keeping
296          * size-proportional components of cost calculation in closer
297          * numbers of digits to per-IO cost components.
298          */
299         IOC_PAGE_SHIFT          = 12,
300         IOC_PAGE_SIZE           = 1 << IOC_PAGE_SHIFT,
301         IOC_SECT_TO_PAGE_SHIFT  = IOC_PAGE_SHIFT - SECTOR_SHIFT,
302 
303         /* if apart further than 16M, consider randio for linear model */
304         LCOEF_RANDIO_PAGES      = 4096,
305 };
306 
307 enum ioc_running {
308         IOC_IDLE,
309         IOC_RUNNING,
310         IOC_STOP,
311 };
312 
313 /* io.cost.qos controls including per-dev enable of the whole controller */
314 enum {
315         QOS_ENABLE,
316         QOS_CTRL,
317         NR_QOS_CTRL_PARAMS,
318 };
319 
320 /* io.cost.qos params */
321 enum {
322         QOS_RPPM,
323         QOS_RLAT,
324         QOS_WPPM,
325         QOS_WLAT,
326         QOS_MIN,
327         QOS_MAX,
328         NR_QOS_PARAMS,
329 };
330 
331 /* io.cost.model controls */
332 enum {
333         COST_CTRL,
334         COST_MODEL,
335         NR_COST_CTRL_PARAMS,
336 };
337 
338 /* builtin linear cost model coefficients */
339 enum {
340         I_LCOEF_RBPS,
341         I_LCOEF_RSEQIOPS,
342         I_LCOEF_RRANDIOPS,
343         I_LCOEF_WBPS,
344         I_LCOEF_WSEQIOPS,
345         I_LCOEF_WRANDIOPS,
346         NR_I_LCOEFS,
347 };
348 
349 enum {
350         LCOEF_RPAGE,
351         LCOEF_RSEQIO,
352         LCOEF_RRANDIO,
353         LCOEF_WPAGE,
354         LCOEF_WSEQIO,
355         LCOEF_WRANDIO,
356         NR_LCOEFS,
357 };
358 
359 enum {
360         AUTOP_INVALID,
361         AUTOP_HDD,
362         AUTOP_SSD_QD1,
363         AUTOP_SSD_DFL,
364         AUTOP_SSD_FAST,
365 };
366 
367 struct ioc_gq;
368 
369 struct ioc_params {
370         u32                             qos[NR_QOS_PARAMS];
371         u64                             i_lcoefs[NR_I_LCOEFS];
372         u64                             lcoefs[NR_LCOEFS];
373         u32                             too_fast_vrate_pct;
374         u32                             too_slow_vrate_pct;
375 };
376 
377 struct ioc_missed {
378         u32                             nr_met;
379         u32                             nr_missed;
380         u32                             last_met;
381         u32                             last_missed;
382 };
383 
384 struct ioc_pcpu_stat {
385         struct ioc_missed               missed[2];
386 
387         u64                             rq_wait_ns;
388         u64                             last_rq_wait_ns;
389 };
390 
391 /* per device */
392 struct ioc {
393         struct rq_qos                   rqos;
394 
395         bool                            enabled;
396 
397         struct ioc_params               params;
398         u32                             period_us;
399         u32                             margin_us;
400         u64                             vrate_min;
401         u64                             vrate_max;
402 
403         spinlock_t                      lock;
404         struct timer_list               timer;
405         struct list_head                active_iocgs;   /* active cgroups */
406         struct ioc_pcpu_stat __percpu   *pcpu_stat;
407 
408         enum ioc_running                running;
409         atomic64_t                      vtime_rate;
410 
411         seqcount_t                      period_seqcount;
412         u32                             period_at;      /* wallclock starttime */
413         u64                             period_at_vtime; /* vtime starttime */
414 
415         atomic64_t                      cur_period;     /* inc'd each period */
416         int                             busy_level;     /* saturation history */
417 
418         u64                             inuse_margin_vtime;
419         bool                            weights_updated;
420         atomic_t                        hweight_gen;    /* for lazy hweights */
421 
422         u64                             autop_too_fast_at;
423         u64                             autop_too_slow_at;
424         int                             autop_idx;
425         bool                            user_qos_params:1;
426         bool                            user_cost_model:1;
427 };
428 
429 /* per device-cgroup pair */
430 struct ioc_gq {
431         struct blkg_policy_data         pd;
432         struct ioc                      *ioc;
433 
434         /*
435          * A iocg can get its weight from two sources - an explicit
436          * per-device-cgroup configuration or the default weight of the
437          * cgroup.  `cfg_weight` is the explicit per-device-cgroup
438          * configuration.  `weight` is the effective considering both
439          * sources.
440          *
441          * When an idle cgroup becomes active its `active` goes from 0 to
442          * `weight`.  `inuse` is the surplus adjusted active weight.
443          * `active` and `inuse` are used to calculate `hweight_active` and
444          * `hweight_inuse`.
445          *
446          * `last_inuse` remembers `inuse` while an iocg is idle to persist
447          * surplus adjustments.
448          */
449         u32                             cfg_weight;
450         u32                             weight;
451         u32                             active;
452         u32                             inuse;
453         u32                             last_inuse;
454 
455         sector_t                        cursor;         /* to detect randio */
456 
457         /*
458          * `vtime` is this iocg's vtime cursor which progresses as IOs are
459          * issued.  If lagging behind device vtime, the delta represents
460          * the currently available IO budget.  If runnning ahead, the
461          * overage.
462          *
463          * `vtime_done` is the same but progressed on completion rather
464          * than issue.  The delta behind `vtime` represents the cost of
465          * currently in-flight IOs.
466          *
467          * `last_vtime` is used to remember `vtime` at the end of the last
468          * period to calculate utilization.
469          */
470         atomic64_t                      vtime;
471         atomic64_t                      done_vtime;
472         u64                             abs_vdebt;
473         u64                             last_vtime;
474 
475         /*
476          * The period this iocg was last active in.  Used for deactivation
477          * and invalidating `vtime`.
478          */
479         atomic64_t                      active_period;
480         struct list_head                active_list;
481 
482         /* see __propagate_active_weight() and current_hweight() for details */
483         u64                             child_active_sum;
484         u64                             child_inuse_sum;
485         int                             hweight_gen;
486         u32                             hweight_active;
487         u32                             hweight_inuse;
488         bool                            has_surplus;
489 
490         struct wait_queue_head          waitq;
491         struct hrtimer                  waitq_timer;
492         struct hrtimer                  delay_timer;
493 
494         /* usage is recorded as fractions of HWEIGHT_WHOLE */
495         int                             usage_idx;
496         u32                             usages[NR_USAGE_SLOTS];
497 
498         /* this iocg's depth in the hierarchy and ancestors including self */
499         int                             level;
500         struct ioc_gq                   *ancestors[];
501 };
502 
503 /* per cgroup */
504 struct ioc_cgrp {
505         struct blkcg_policy_data        cpd;
506         unsigned int                    dfl_weight;
507 };
508 
509 struct ioc_now {
510         u64                             now_ns;
511         u32                             now;
512         u64                             vnow;
513         u64                             vrate;
514 };
515 
516 struct iocg_wait {
517         struct wait_queue_entry         wait;
518         struct bio                      *bio;
519         u64                             abs_cost;
520         bool                            committed;
521 };
522 
523 struct iocg_wake_ctx {
524         struct ioc_gq                   *iocg;
525         u32                             hw_inuse;
526         s64                             vbudget;
527 };
528 
529 static const struct ioc_params autop[] = {
530         [AUTOP_HDD] = {
531                 .qos                            = {
532                         [QOS_RLAT]              =        250000, /* 250ms */
533                         [QOS_WLAT]              =        250000,
534                         [QOS_MIN]               = VRATE_MIN_PPM,
535                         [QOS_MAX]               = VRATE_MAX_PPM,
536                 },
537                 .i_lcoefs                       = {
538                         [I_LCOEF_RBPS]          =     174019176,
539                         [I_LCOEF_RSEQIOPS]      =         41708,
540                         [I_LCOEF_RRANDIOPS]     =           370,
541                         [I_LCOEF_WBPS]          =     178075866,
542                         [I_LCOEF_WSEQIOPS]      =         42705,
543                         [I_LCOEF_WRANDIOPS]     =           378,
544                 },
545         },
546         [AUTOP_SSD_QD1] = {
547                 .qos                            = {
548                         [QOS_RLAT]              =         25000, /* 25ms */
549                         [QOS_WLAT]              =         25000,
550                         [QOS_MIN]               = VRATE_MIN_PPM,
551                         [QOS_MAX]               = VRATE_MAX_PPM,
552                 },
553                 .i_lcoefs                       = {
554                         [I_LCOEF_RBPS]          =     245855193,
555                         [I_LCOEF_RSEQIOPS]      =         61575,
556                         [I_LCOEF_RRANDIOPS]     =          6946,
557                         [I_LCOEF_WBPS]          =     141365009,
558                         [I_LCOEF_WSEQIOPS]      =         33716,
559                         [I_LCOEF_WRANDIOPS]     =         26796,
560                 },
561         },
562         [AUTOP_SSD_DFL] = {
563                 .qos                            = {
564                         [QOS_RLAT]              =         25000, /* 25ms */
565                         [QOS_WLAT]              =         25000,
566                         [QOS_MIN]               = VRATE_MIN_PPM,
567                         [QOS_MAX]               = VRATE_MAX_PPM,
568                 },
569                 .i_lcoefs                       = {
570                         [I_LCOEF_RBPS]          =     488636629,
571                         [I_LCOEF_RSEQIOPS]      =          8932,
572                         [I_LCOEF_RRANDIOPS]     =          8518,
573                         [I_LCOEF_WBPS]          =     427891549,
574                         [I_LCOEF_WSEQIOPS]      =         28755,
575                         [I_LCOEF_WRANDIOPS]     =         21940,
576                 },
577                 .too_fast_vrate_pct             =           500,
578         },
579         [AUTOP_SSD_FAST] = {
580                 .qos                            = {
581                         [QOS_RLAT]              =          5000, /* 5ms */
582                         [QOS_WLAT]              =          5000,
583                         [QOS_MIN]               = VRATE_MIN_PPM,
584                         [QOS_MAX]               = VRATE_MAX_PPM,
585                 },
586                 .i_lcoefs                       = {
587                         [I_LCOEF_RBPS]          =    3102524156LLU,
588                         [I_LCOEF_RSEQIOPS]      =        724816,
589                         [I_LCOEF_RRANDIOPS]     =        778122,
590                         [I_LCOEF_WBPS]          =    1742780862LLU,
591                         [I_LCOEF_WSEQIOPS]      =        425702,
592                         [I_LCOEF_WRANDIOPS]     =        443193,
593                 },
594                 .too_slow_vrate_pct             =            10,
595         },
596 };
597 
598 /*
599  * vrate adjust percentages indexed by ioc->busy_level.  We adjust up on
600  * vtime credit shortage and down on device saturation.
601  */
602 static u32 vrate_adj_pct[] =
603         { 0, 0, 0, 0,
604           1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
605           2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
606           4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16 };
607 
608 static struct blkcg_policy blkcg_policy_iocost;
609 
610 /* accessors and helpers */
611 static struct ioc *rqos_to_ioc(struct rq_qos *rqos)
612 {
613         return container_of(rqos, struct ioc, rqos);
614 }
615 
616 static struct ioc *q_to_ioc(struct request_queue *q)
617 {
618         return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST));
619 }
620 
621 static const char *q_name(struct request_queue *q)
622 {
623         if (test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
624                 return kobject_name(q->kobj.parent);
625         else
626                 return "<unknown>";
627 }
628 
629 static const char __maybe_unused *ioc_name(struct ioc *ioc)
630 {
631         return q_name(ioc->rqos.q);
632 }
633 
634 static struct ioc_gq *pd_to_iocg(struct blkg_policy_data *pd)
635 {
636         return pd ? container_of(pd, struct ioc_gq, pd) : NULL;
637 }
638 
639 static struct ioc_gq *blkg_to_iocg(struct blkcg_gq *blkg)
640 {
641         return pd_to_iocg(blkg_to_pd(blkg, &blkcg_policy_iocost));
642 }
643 
644 static struct blkcg_gq *iocg_to_blkg(struct ioc_gq *iocg)
645 {
646         return pd_to_blkg(&iocg->pd);
647 }
648 
649 static struct ioc_cgrp *blkcg_to_iocc(struct blkcg *blkcg)
650 {
651         return container_of(blkcg_to_cpd(blkcg, &blkcg_policy_iocost),
652                             struct ioc_cgrp, cpd);
653 }
654 
655 /*
656  * Scale @abs_cost to the inverse of @hw_inuse.  The lower the hierarchical
657  * weight, the more expensive each IO.  Must round up.
658  */
659 static u64 abs_cost_to_cost(u64 abs_cost, u32 hw_inuse)
660 {
661         return DIV64_U64_ROUND_UP(abs_cost * HWEIGHT_WHOLE, hw_inuse);
662 }
663 
664 /*
665  * The inverse of abs_cost_to_cost().  Must round up.
666  */
667 static u64 cost_to_abs_cost(u64 cost, u32 hw_inuse)
668 {
669         return DIV64_U64_ROUND_UP(cost * hw_inuse, HWEIGHT_WHOLE);
670 }
671 
672 static void iocg_commit_bio(struct ioc_gq *iocg, struct bio *bio, u64 cost)
673 {
674         bio->bi_iocost_cost = cost;
675         atomic64_add(cost, &iocg->vtime);
676 }
677 
678 #define CREATE_TRACE_POINTS
679 #include <trace/events/iocost.h>
680 
681 /* latency Qos params changed, update period_us and all the dependent params */
682 static void ioc_refresh_period_us(struct ioc *ioc)
683 {
684         u32 ppm, lat, multi, period_us;
685 
686         lockdep_assert_held(&ioc->lock);
687 
688         /* pick the higher latency target */
689         if (ioc->params.qos[QOS_RLAT] >= ioc->params.qos[QOS_WLAT]) {
690                 ppm = ioc->params.qos[QOS_RPPM];
691                 lat = ioc->params.qos[QOS_RLAT];
692         } else {
693                 ppm = ioc->params.qos[QOS_WPPM];
694                 lat = ioc->params.qos[QOS_WLAT];
695         }
696 
697         /*
698          * We want the period to be long enough to contain a healthy number
699          * of IOs while short enough for granular control.  Define it as a
700          * multiple of the latency target.  Ideally, the multiplier should
701          * be scaled according to the percentile so that it would nominally
702          * contain a certain number of requests.  Let's be simpler and
703          * scale it linearly so that it's 2x >= pct(90) and 10x at pct(50).
704          */
705         if (ppm)
706                 multi = max_t(u32, (MILLION - ppm) / 50000, 2);
707         else
708                 multi = 2;
709         period_us = multi * lat;
710         period_us = clamp_t(u32, period_us, MIN_PERIOD, MAX_PERIOD);
711 
712         /* calculate dependent params */
713         ioc->period_us = period_us;
714         ioc->margin_us = period_us * MARGIN_PCT / 100;
715         ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP(
716                         period_us * VTIME_PER_USEC * INUSE_MARGIN_PCT, 100);
717 }
718 
719 static int ioc_autop_idx(struct ioc *ioc)
720 {
721         int idx = ioc->autop_idx;
722         const struct ioc_params *p = &autop[idx];
723         u32 vrate_pct;
724         u64 now_ns;
725 
726         /* rotational? */
727         if (!blk_queue_nonrot(ioc->rqos.q))
728                 return AUTOP_HDD;
729 
730         /* handle SATA SSDs w/ broken NCQ */
731         if (blk_queue_depth(ioc->rqos.q) == 1)
732                 return AUTOP_SSD_QD1;
733 
734         /* use one of the normal ssd sets */
735         if (idx < AUTOP_SSD_DFL)
736                 return AUTOP_SSD_DFL;
737 
738         /* if user is overriding anything, maintain what was there */
739         if (ioc->user_qos_params || ioc->user_cost_model)
740                 return idx;
741 
742         /* step up/down based on the vrate */
743         vrate_pct = div64_u64(atomic64_read(&ioc->vtime_rate) * 100,
744                               VTIME_PER_USEC);
745         now_ns = ktime_get_ns();
746 
747         if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) {
748                 if (!ioc->autop_too_fast_at)
749                         ioc->autop_too_fast_at = now_ns;
750                 if (now_ns - ioc->autop_too_fast_at >= AUTOP_CYCLE_NSEC)
751                         return idx + 1;
752         } else {
753                 ioc->autop_too_fast_at = 0;
754         }
755 
756         if (p->too_slow_vrate_pct && p->too_slow_vrate_pct >= vrate_pct) {
757                 if (!ioc->autop_too_slow_at)
758                         ioc->autop_too_slow_at = now_ns;
759                 if (now_ns - ioc->autop_too_slow_at >= AUTOP_CYCLE_NSEC)
760                         return idx - 1;
761         } else {
762                 ioc->autop_too_slow_at = 0;
763         }
764 
765         return idx;
766 }
767 
768 /*
769  * Take the followings as input
770  *
771  *  @bps        maximum sequential throughput
772  *  @seqiops    maximum sequential 4k iops
773  *  @randiops   maximum random 4k iops
774  *
775  * and calculate the linear model cost coefficients.
776  *
777  *  *@page      per-page cost           1s / (@bps / 4096)
778  *  *@seqio     base cost of a seq IO   max((1s / @seqiops) - *@page, 0)
779  *  @randiops   base cost of a rand IO  max((1s / @randiops) - *@page, 0)
780  */
781 static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops,
782                         u64 *page, u64 *seqio, u64 *randio)
783 {
784         u64 v;
785 
786         *page = *seqio = *randio = 0;
787 
788         if (bps)
789                 *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC,
790                                            DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE));
791 
792         if (seqiops) {
793                 v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops);
794                 if (v > *page)
795                         *seqio = v - *page;
796         }
797 
798         if (randiops) {
799                 v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops);
800                 if (v > *page)
801                         *randio = v - *page;
802         }
803 }
804 
805 static void ioc_refresh_lcoefs(struct ioc *ioc)
806 {
807         u64 *u = ioc->params.i_lcoefs;
808         u64 *c = ioc->params.lcoefs;
809 
810         calc_lcoefs(u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
811                     &c[LCOEF_RPAGE], &c[LCOEF_RSEQIO], &c[LCOEF_RRANDIO]);
812         calc_lcoefs(u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS],
813                     &c[LCOEF_WPAGE], &c[LCOEF_WSEQIO], &c[LCOEF_WRANDIO]);
814 }
815 
816 static bool ioc_refresh_params(struct ioc *ioc, bool force)
817 {
818         const struct ioc_params *p;
819         int idx;
820 
821         lockdep_assert_held(&ioc->lock);
822 
823         idx = ioc_autop_idx(ioc);
824         p = &autop[idx];
825 
826         if (idx == ioc->autop_idx && !force)
827                 return false;
828 
829         if (idx != ioc->autop_idx)
830                 atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
831 
832         ioc->autop_idx = idx;
833         ioc->autop_too_fast_at = 0;
834         ioc->autop_too_slow_at = 0;
835 
836         if (!ioc->user_qos_params)
837                 memcpy(ioc->params.qos, p->qos, sizeof(p->qos));
838         if (!ioc->user_cost_model)
839                 memcpy(ioc->params.i_lcoefs, p->i_lcoefs, sizeof(p->i_lcoefs));
840 
841         ioc_refresh_period_us(ioc);
842         ioc_refresh_lcoefs(ioc);
843 
844         ioc->vrate_min = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MIN] *
845                                             VTIME_PER_USEC, MILLION);
846         ioc->vrate_max = div64_u64((u64)ioc->params.qos[QOS_MAX] *
847                                    VTIME_PER_USEC, MILLION);
848 
849         return true;
850 }
851 
852 /* take a snapshot of the current [v]time and vrate */
853 static void ioc_now(struct ioc *ioc, struct ioc_now *now)
854 {
855         unsigned seq;
856 
857         now->now_ns = ktime_get();
858         now->now = ktime_to_us(now->now_ns);
859         now->vrate = atomic64_read(&ioc->vtime_rate);
860 
861         /*
862          * The current vtime is
863          *
864          *   vtime at period start + (wallclock time since the start) * vrate
865          *
866          * As a consistent snapshot of `period_at_vtime` and `period_at` is
867          * needed, they're seqcount protected.
868          */
869         do {
870                 seq = read_seqcount_begin(&ioc->period_seqcount);
871                 now->vnow = ioc->period_at_vtime +
872                         (now->now - ioc->period_at) * now->vrate;
873         } while (read_seqcount_retry(&ioc->period_seqcount, seq));
874 }
875 
876 static void ioc_start_period(struct ioc *ioc, struct ioc_now *now)
877 {
878         lockdep_assert_held(&ioc->lock);
879         WARN_ON_ONCE(ioc->running != IOC_RUNNING);
880 
881         write_seqcount_begin(&ioc->period_seqcount);
882         ioc->period_at = now->now;
883         ioc->period_at_vtime = now->vnow;
884         write_seqcount_end(&ioc->period_seqcount);
885 
886         ioc->timer.expires = jiffies + usecs_to_jiffies(ioc->period_us);
887         add_timer(&ioc->timer);
888 }
889 
890 /*
891  * Update @iocg's `active` and `inuse` to @active and @inuse, update level
892  * weight sums and propagate upwards accordingly.
893  */
894 static void __propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse)
895 {
896         struct ioc *ioc = iocg->ioc;
897         int lvl;
898 
899         lockdep_assert_held(&ioc->lock);
900 
901         inuse = min(active, inuse);
902 
903         for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
904                 struct ioc_gq *parent = iocg->ancestors[lvl];
905                 struct ioc_gq *child = iocg->ancestors[lvl + 1];
906                 u32 parent_active = 0, parent_inuse = 0;
907 
908                 /* update the level sums */
909                 parent->child_active_sum += (s32)(active - child->active);
910                 parent->child_inuse_sum += (s32)(inuse - child->inuse);
911                 /* apply the udpates */
912                 child->active = active;
913                 child->inuse = inuse;
914 
915                 /*
916                  * The delta between inuse and active sums indicates that
917                  * that much of weight is being given away.  Parent's inuse
918                  * and active should reflect the ratio.
919                  */
920                 if (parent->child_active_sum) {
921                         parent_active = parent->weight;
922                         parent_inuse = DIV64_U64_ROUND_UP(
923                                 parent_active * parent->child_inuse_sum,
924                                 parent->child_active_sum);
925                 }
926 
927                 /* do we need to keep walking up? */
928                 if (parent_active == parent->active &&
929                     parent_inuse == parent->inuse)
930                         break;
931 
932                 active = parent_active;
933                 inuse = parent_inuse;
934         }
935 
936         ioc->weights_updated = true;
937 }
938 
939 static void commit_active_weights(struct ioc *ioc)
940 {
941         lockdep_assert_held(&ioc->lock);
942 
943         if (ioc->weights_updated) {
944                 /* paired with rmb in current_hweight(), see there */
945                 smp_wmb();
946                 atomic_inc(&ioc->hweight_gen);
947                 ioc->weights_updated = false;
948         }
949 }
950 
951 static void propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse)
952 {
953         __propagate_active_weight(iocg, active, inuse);
954         commit_active_weights(iocg->ioc);
955 }
956 
957 static void current_hweight(struct ioc_gq *iocg, u32 *hw_activep, u32 *hw_inusep)
958 {
959         struct ioc *ioc = iocg->ioc;
960         int lvl;
961         u32 hwa, hwi;
962         int ioc_gen;
963 
964         /* hot path - if uptodate, use cached */
965         ioc_gen = atomic_read(&ioc->hweight_gen);
966         if (ioc_gen == iocg->hweight_gen)
967                 goto out;
968 
969         /*
970          * Paired with wmb in commit_active_weights().  If we saw the
971          * updated hweight_gen, all the weight updates from
972          * __propagate_active_weight() are visible too.
973          *
974          * We can race with weight updates during calculation and get it
975          * wrong.  However, hweight_gen would have changed and a future
976          * reader will recalculate and we're guaranteed to discard the
977          * wrong result soon.
978          */
979         smp_rmb();
980 
981         hwa = hwi = HWEIGHT_WHOLE;
982         for (lvl = 0; lvl <= iocg->level - 1; lvl++) {
983                 struct ioc_gq *parent = iocg->ancestors[lvl];
984                 struct ioc_gq *child = iocg->ancestors[lvl + 1];
985                 u32 active_sum = READ_ONCE(parent->child_active_sum);
986                 u32 inuse_sum = READ_ONCE(parent->child_inuse_sum);
987                 u32 active = READ_ONCE(child->active);
988                 u32 inuse = READ_ONCE(child->inuse);
989 
990                 /* we can race with deactivations and either may read as zero */
991                 if (!active_sum || !inuse_sum)
992                         continue;
993 
994                 active_sum = max(active, active_sum);
995                 hwa = hwa * active / active_sum;        /* max 16bits * 10000 */
996 
997                 inuse_sum = max(inuse, inuse_sum);
998                 hwi = hwi * inuse / inuse_sum;          /* max 16bits * 10000 */
999         }
1000 
1001         iocg->hweight_active = max_t(u32, hwa, 1);
1002         iocg->hweight_inuse = max_t(u32, hwi, 1);
1003         iocg->hweight_gen = ioc_gen;
1004 out:
1005         if (hw_activep)
1006                 *hw_activep = iocg->hweight_active;
1007         if (hw_inusep)
1008                 *hw_inusep = iocg->hweight_inuse;
1009 }
1010 
1011 static void weight_updated(struct ioc_gq *iocg)
1012 {
1013         struct ioc *ioc = iocg->ioc;
1014         struct blkcg_gq *blkg = iocg_to_blkg(iocg);
1015         struct ioc_cgrp *iocc = blkcg_to_iocc(blkg->blkcg);
1016         u32 weight;
1017 
1018         lockdep_assert_held(&ioc->lock);
1019 
1020         weight = iocg->cfg_weight ?: iocc->dfl_weight;
1021         if (weight != iocg->weight && iocg->active)
1022                 propagate_active_weight(iocg, weight,
1023                         DIV64_U64_ROUND_UP(iocg->inuse * weight, iocg->weight));
1024         iocg->weight = weight;
1025 }
1026 
1027 static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now)
1028 {
1029         struct ioc *ioc = iocg->ioc;
1030         u64 last_period, cur_period, max_period_delta;
1031         u64 vtime, vmargin, vmin;
1032         int i;
1033 
1034         /*
1035          * If seem to be already active, just update the stamp to tell the
1036          * timer that we're still active.  We don't mind occassional races.
1037          */
1038         if (!list_empty(&iocg->active_list)) {
1039                 ioc_now(ioc, now);
1040                 cur_period = atomic64_read(&ioc->cur_period);
1041                 if (atomic64_read(&iocg->active_period) != cur_period)
1042                         atomic64_set(&iocg->active_period, cur_period);
1043                 return true;
1044         }
1045 
1046         /* racy check on internal node IOs, treat as root level IOs */
1047         if (iocg->child_active_sum)
1048                 return false;
1049 
1050         spin_lock_irq(&ioc->lock);
1051 
1052         ioc_now(ioc, now);
1053 
1054         /* update period */
1055         cur_period = atomic64_read(&ioc->cur_period);
1056         last_period = atomic64_read(&iocg->active_period);
1057         atomic64_set(&iocg->active_period, cur_period);
1058 
1059         /* already activated or breaking leaf-only constraint? */
1060         if (!list_empty(&iocg->active_list))
1061                 goto succeed_unlock;
1062         for (i = iocg->level - 1; i > 0; i--)
1063                 if (!list_empty(&iocg->ancestors[i]->active_list))
1064                         goto fail_unlock;
1065 
1066         if (iocg->child_active_sum)
1067                 goto fail_unlock;
1068 
1069         /*
1070          * vtime may wrap when vrate is raised substantially due to
1071          * underestimated IO costs.  Look at the period and ignore its
1072          * vtime if the iocg has been idle for too long.  Also, cap the
1073          * budget it can start with to the margin.
1074          */
1075         max_period_delta = DIV64_U64_ROUND_UP(VTIME_VALID_DUR, ioc->period_us);
1076         vtime = atomic64_read(&iocg->vtime);
1077         vmargin = ioc->margin_us * now->vrate;
1078         vmin = now->vnow - vmargin;
1079 
1080         if (last_period + max_period_delta < cur_period ||
1081             time_before64(vtime, vmin)) {
1082                 atomic64_add(vmin - vtime, &iocg->vtime);
1083                 atomic64_add(vmin - vtime, &iocg->done_vtime);
1084                 vtime = vmin;
1085         }
1086 
1087         /*
1088          * Activate, propagate weight and start period timer if not
1089          * running.  Reset hweight_gen to avoid accidental match from
1090          * wrapping.
1091          */
1092         iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1;
1093         list_add(&iocg->active_list, &ioc->active_iocgs);
1094         propagate_active_weight(iocg, iocg->weight,
1095                                 iocg->last_inuse ?: iocg->weight);
1096 
1097         TRACE_IOCG_PATH(iocg_activate, iocg, now,
1098                         last_period, cur_period, vtime);
1099 
1100         iocg->last_vtime = vtime;
1101 
1102         if (ioc->running == IOC_IDLE) {
1103                 ioc->running = IOC_RUNNING;
1104                 ioc_start_period(ioc, now);
1105         }
1106 
1107 succeed_unlock:
1108         spin_unlock_irq(&ioc->lock);
1109         return true;
1110 
1111 fail_unlock:
1112         spin_unlock_irq(&ioc->lock);
1113         return false;
1114 }
1115 
1116 static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode,
1117                         int flags, void *key)
1118 {
1119         struct iocg_wait *wait = container_of(wq_entry, struct iocg_wait, wait);
1120         struct iocg_wake_ctx *ctx = (struct iocg_wake_ctx *)key;
1121         u64 cost = abs_cost_to_cost(wait->abs_cost, ctx->hw_inuse);
1122 
1123         ctx->vbudget -= cost;
1124 
1125         if (ctx->vbudget < 0)
1126                 return -1;
1127 
1128         iocg_commit_bio(ctx->iocg, wait->bio, cost);
1129 
1130         /*
1131          * autoremove_wake_function() removes the wait entry only when it
1132          * actually changed the task state.  We want the wait always
1133          * removed.  Remove explicitly and use default_wake_function().
1134          */
1135         list_del_init(&wq_entry->entry);
1136         wait->committed = true;
1137 
1138         default_wake_function(wq_entry, mode, flags, key);
1139         return 0;
1140 }
1141 
1142 static void iocg_kick_waitq(struct ioc_gq *iocg, struct ioc_now *now)
1143 {
1144         struct ioc *ioc = iocg->ioc;
1145         struct iocg_wake_ctx ctx = { .iocg = iocg };
1146         u64 margin_ns = (u64)(ioc->period_us *
1147                               WAITQ_TIMER_MARGIN_PCT / 100) * NSEC_PER_USEC;
1148         u64 vdebt, vshortage, expires, oexpires;
1149         s64 vbudget;
1150         u32 hw_inuse;
1151 
1152         lockdep_assert_held(&iocg->waitq.lock);
1153 
1154         current_hweight(iocg, NULL, &hw_inuse);
1155         vbudget = now->vnow - atomic64_read(&iocg->vtime);
1156 
1157         /* pay off debt */
1158         vdebt = abs_cost_to_cost(iocg->abs_vdebt, hw_inuse);
1159         if (vdebt && vbudget > 0) {
1160                 u64 delta = min_t(u64, vbudget, vdebt);
1161                 u64 abs_delta = min(cost_to_abs_cost(delta, hw_inuse),
1162                                     iocg->abs_vdebt);
1163 
1164                 atomic64_add(delta, &iocg->vtime);
1165                 atomic64_add(delta, &iocg->done_vtime);
1166                 iocg->abs_vdebt -= abs_delta;
1167         }
1168 
1169         /*
1170          * Wake up the ones which are due and see how much vtime we'll need
1171          * for the next one.
1172          */
1173         ctx.hw_inuse = hw_inuse;
1174         ctx.vbudget = vbudget - vdebt;
1175         __wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);
1176         if (!waitqueue_active(&iocg->waitq))
1177                 return;
1178         if (WARN_ON_ONCE(ctx.vbudget >= 0))
1179                 return;
1180 
1181         /* determine next wakeup, add a quarter margin to guarantee chunking */
1182         vshortage = -ctx.vbudget;
1183         expires = now->now_ns +
1184                 DIV64_U64_ROUND_UP(vshortage, now->vrate) * NSEC_PER_USEC;
1185         expires += margin_ns / 4;
1186 
1187         /* if already active and close enough, don't bother */
1188         oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->waitq_timer));
1189         if (hrtimer_is_queued(&iocg->waitq_timer) &&
1190             abs(oexpires - expires) <= margin_ns / 4)
1191                 return;
1192 
1193         hrtimer_start_range_ns(&iocg->waitq_timer, ns_to_ktime(expires),
1194                                margin_ns / 4, HRTIMER_MODE_ABS);
1195 }
1196 
1197 static enum hrtimer_restart iocg_waitq_timer_fn(struct hrtimer *timer)
1198 {
1199         struct ioc_gq *iocg = container_of(timer, struct ioc_gq, waitq_timer);
1200         struct ioc_now now;
1201         unsigned long flags;
1202 
1203         ioc_now(iocg->ioc, &now);
1204 
1205         spin_lock_irqsave(&iocg->waitq.lock, flags);
1206         iocg_kick_waitq(iocg, &now);
1207         spin_unlock_irqrestore(&iocg->waitq.lock, flags);
1208 
1209         return HRTIMER_NORESTART;
1210 }
1211 
1212 static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now, u64 cost)
1213 {
1214         struct ioc *ioc = iocg->ioc;
1215         struct blkcg_gq *blkg = iocg_to_blkg(iocg);
1216         u64 vtime = atomic64_read(&iocg->vtime);
1217         u64 vmargin = ioc->margin_us * now->vrate;
1218         u64 margin_ns = ioc->margin_us * NSEC_PER_USEC;
1219         u64 expires, oexpires;
1220         u32 hw_inuse;
1221 
1222         lockdep_assert_held(&iocg->waitq.lock);
1223 
1224         /* debt-adjust vtime */
1225         current_hweight(iocg, NULL, &hw_inuse);
1226         vtime += abs_cost_to_cost(iocg->abs_vdebt, hw_inuse);
1227 
1228         /*
1229          * Clear or maintain depending on the overage. Non-zero vdebt is what
1230          * guarantees that @iocg is online and future iocg_kick_delay() will
1231          * clear use_delay. Don't leave it on when there's no vdebt.
1232          */
1233         if (!iocg->abs_vdebt || time_before_eq64(vtime, now->vnow)) {
1234                 blkcg_clear_delay(blkg);
1235                 return false;
1236         }
1237         if (!atomic_read(&blkg->use_delay) &&
1238             time_before_eq64(vtime, now->vnow + vmargin))
1239                 return false;
1240 
1241         /* use delay */
1242         if (cost) {
1243                 u64 cost_ns = DIV64_U64_ROUND_UP(cost * NSEC_PER_USEC,
1244                                                  now->vrate);
1245                 blkcg_add_delay(blkg, now->now_ns, cost_ns);
1246         }
1247         blkcg_use_delay(blkg);
1248 
1249         expires = now->now_ns + DIV64_U64_ROUND_UP(vtime - now->vnow,
1250                                                    now->vrate) * NSEC_PER_USEC;
1251 
1252         /* if already active and close enough, don't bother */
1253         oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->delay_timer));
1254         if (hrtimer_is_queued(&iocg->delay_timer) &&
1255             abs(oexpires - expires) <= margin_ns / 4)
1256                 return true;
1257 
1258         hrtimer_start_range_ns(&iocg->delay_timer, ns_to_ktime(expires),
1259                                margin_ns / 4, HRTIMER_MODE_ABS);
1260         return true;
1261 }
1262 
1263 static enum hrtimer_restart iocg_delay_timer_fn(struct hrtimer *timer)
1264 {
1265         struct ioc_gq *iocg = container_of(timer, struct ioc_gq, delay_timer);
1266         struct ioc_now now;
1267         unsigned long flags;
1268 
1269         spin_lock_irqsave(&iocg->waitq.lock, flags);
1270         ioc_now(iocg->ioc, &now);
1271         iocg_kick_delay(iocg, &now, 0);
1272         spin_unlock_irqrestore(&iocg->waitq.lock, flags);
1273 
1274         return HRTIMER_NORESTART;
1275 }
1276 
1277 static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p)
1278 {
1279         u32 nr_met[2] = { };
1280         u32 nr_missed[2] = { };
1281         u64 rq_wait_ns = 0;
1282         int cpu, rw;
1283 
1284         for_each_online_cpu(cpu) {
1285                 struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu);
1286                 u64 this_rq_wait_ns;
1287 
1288                 for (rw = READ; rw <= WRITE; rw++) {
1289                         u32 this_met = READ_ONCE(stat->missed[rw].nr_met);
1290                         u32 this_missed = READ_ONCE(stat->missed[rw].nr_missed);
1291 
1292                         nr_met[rw] += this_met - stat->missed[rw].last_met;
1293                         nr_missed[rw] += this_missed - stat->missed[rw].last_missed;
1294                         stat->missed[rw].last_met = this_met;
1295                         stat->missed[rw].last_missed = this_missed;
1296                 }
1297 
1298                 this_rq_wait_ns = READ_ONCE(stat->rq_wait_ns);
1299                 rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns;
1300                 stat->last_rq_wait_ns = this_rq_wait_ns;
1301         }
1302 
1303         for (rw = READ; rw <= WRITE; rw++) {
1304                 if (nr_met[rw] + nr_missed[rw])
1305                         missed_ppm_ar[rw] =
1306                                 DIV64_U64_ROUND_UP((u64)nr_missed[rw] * MILLION,
1307                                                    nr_met[rw] + nr_missed[rw]);
1308                 else
1309                         missed_ppm_ar[rw] = 0;
1310         }
1311 
1312         *rq_wait_pct_p = div64_u64(rq_wait_ns * 100,
1313                                    ioc->period_us * NSEC_PER_USEC);
1314 }
1315 
1316 /* was iocg idle this period? */
1317 static bool iocg_is_idle(struct ioc_gq *iocg)
1318 {
1319         struct ioc *ioc = iocg->ioc;
1320 
1321         /* did something get issued this period? */
1322         if (atomic64_read(&iocg->active_period) ==
1323             atomic64_read(&ioc->cur_period))
1324                 return false;
1325 
1326         /* is something in flight? */
1327         if (atomic64_read(&iocg->done_vtime) != atomic64_read(&iocg->vtime))
1328                 return false;
1329 
1330         return true;
1331 }
1332 
1333 /* returns usage with margin added if surplus is large enough */
1334 static u32 surplus_adjusted_hweight_inuse(u32 usage, u32 hw_inuse)
1335 {
1336         /* add margin */
1337         usage = DIV_ROUND_UP(usage * SURPLUS_SCALE_PCT, 100);
1338         usage += SURPLUS_SCALE_ABS;
1339 
1340         /* don't bother if the surplus is too small */
1341         if (usage + SURPLUS_MIN_ADJ_DELTA > hw_inuse)
1342                 return 0;
1343 
1344         return usage;
1345 }
1346 
1347 static void ioc_timer_fn(struct timer_list *timer)
1348 {
1349         struct ioc *ioc = container_of(timer, struct ioc, timer);
1350         struct ioc_gq *iocg, *tiocg;
1351         struct ioc_now now;
1352         int nr_surpluses = 0, nr_shortages = 0, nr_lagging = 0;
1353         u32 ppm_rthr = MILLION - ioc->params.qos[QOS_RPPM];
1354         u32 ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM];
1355         u32 missed_ppm[2], rq_wait_pct;
1356         u64 period_vtime;
1357         int prev_busy_level, i;
1358 
1359         /* how were the latencies during the period? */
1360         ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct);
1361 
1362         /* take care of active iocgs */
1363         spin_lock_irq(&ioc->lock);
1364 
1365         ioc_now(ioc, &now);
1366 
1367         period_vtime = now.vnow - ioc->period_at_vtime;
1368         if (WARN_ON_ONCE(!period_vtime)) {
1369                 spin_unlock_irq(&ioc->lock);
1370                 return;
1371         }
1372 
1373         /*
1374          * Waiters determine the sleep durations based on the vrate they
1375          * saw at the time of sleep.  If vrate has increased, some waiters
1376          * could be sleeping for too long.  Wake up tardy waiters which
1377          * should have woken up in the last period and expire idle iocgs.
1378          */
1379         list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) {
1380                 if (!waitqueue_active(&iocg->waitq) && iocg->abs_vdebt &&
1381                     !iocg_is_idle(iocg))
1382                         continue;
1383 
1384                 spin_lock(&iocg->waitq.lock);
1385 
1386                 if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt) {
1387                         /* might be oversleeping vtime / hweight changes, kick */
1388                         iocg_kick_waitq(iocg, &now);
1389                         iocg_kick_delay(iocg, &now, 0);
1390                 } else if (iocg_is_idle(iocg)) {
1391                         /* no waiter and idle, deactivate */
1392                         iocg->last_inuse = iocg->inuse;
1393                         __propagate_active_weight(iocg, 0, 0);
1394                         list_del_init(&iocg->active_list);
1395                 }
1396 
1397                 spin_unlock(&iocg->waitq.lock);
1398         }
1399         commit_active_weights(ioc);
1400 
1401         /* calc usages and see whether some weights need to be moved around */
1402         list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
1403                 u64 vdone, vtime, vusage, vmargin, vmin;
1404                 u32 hw_active, hw_inuse, usage;
1405 
1406                 /*
1407                  * Collect unused and wind vtime closer to vnow to prevent
1408                  * iocgs from accumulating a large amount of budget.
1409                  */
1410                 vdone = atomic64_read(&iocg->done_vtime);
1411                 vtime = atomic64_read(&iocg->vtime);
1412                 current_hweight(iocg, &hw_active, &hw_inuse);
1413 
1414                 /*
1415                  * Latency QoS detection doesn't account for IOs which are
1416                  * in-flight for longer than a period.  Detect them by
1417                  * comparing vdone against period start.  If lagging behind
1418                  * IOs from past periods, don't increase vrate.
1419                  */
1420                 if ((ppm_rthr != MILLION || ppm_wthr != MILLION) &&
1421                     !atomic_read(&iocg_to_blkg(iocg)->use_delay) &&
1422                     time_after64(vtime, vdone) &&
1423                     time_after64(vtime, now.vnow -
1424                                  MAX_LAGGING_PERIODS * period_vtime) &&
1425                     time_before64(vdone, now.vnow - period_vtime))
1426                         nr_lagging++;
1427 
1428                 if (waitqueue_active(&iocg->waitq))
1429                         vusage = now.vnow - iocg->last_vtime;
1430                 else if (time_before64(iocg->last_vtime, vtime))
1431                         vusage = vtime - iocg->last_vtime;
1432                 else
1433                         vusage = 0;
1434 
1435                 iocg->last_vtime += vusage;
1436                 /*
1437                  * Factor in in-flight vtime into vusage to avoid
1438                  * high-latency completions appearing as idle.  This should
1439                  * be done after the above ->last_time adjustment.
1440                  */
1441                 vusage = max(vusage, vtime - vdone);
1442 
1443                 /* calculate hweight based usage ratio and record */
1444                 if (vusage) {
1445                         usage = DIV64_U64_ROUND_UP(vusage * hw_inuse,
1446                                                    period_vtime);
1447                         iocg->usage_idx = (iocg->usage_idx + 1) % NR_USAGE_SLOTS;
1448                         iocg->usages[iocg->usage_idx] = usage;
1449                 } else {
1450                         usage = 0;
1451                 }
1452 
1453                 /* see whether there's surplus vtime */
1454                 vmargin = ioc->margin_us * now.vrate;
1455                 vmin = now.vnow - vmargin;
1456 
1457                 iocg->has_surplus = false;
1458 
1459                 if (!waitqueue_active(&iocg->waitq) &&
1460                     time_before64(vtime, vmin)) {
1461                         u64 delta = vmin - vtime;
1462 
1463                         /* throw away surplus vtime */
1464                         atomic64_add(delta, &iocg->vtime);
1465                         atomic64_add(delta, &iocg->done_vtime);
1466                         iocg->last_vtime += delta;
1467                         /* if usage is sufficiently low, maybe it can donate */
1468                         if (surplus_adjusted_hweight_inuse(usage, hw_inuse)) {
1469                                 iocg->has_surplus = true;
1470                                 nr_surpluses++;
1471                         }
1472                 } else if (hw_inuse < hw_active) {
1473                         u32 new_hwi, new_inuse;
1474 
1475                         /* was donating but might need to take back some */
1476                         if (waitqueue_active(&iocg->waitq)) {
1477                                 new_hwi = hw_active;
1478                         } else {
1479                                 new_hwi = max(hw_inuse,
1480                                               usage * SURPLUS_SCALE_PCT / 100 +
1481                                               SURPLUS_SCALE_ABS);
1482                         }
1483 
1484                         new_inuse = div64_u64((u64)iocg->inuse * new_hwi,
1485                                               hw_inuse);
1486                         new_inuse = clamp_t(u32, new_inuse, 1, iocg->active);
1487 
1488                         if (new_inuse > iocg->inuse) {
1489                                 TRACE_IOCG_PATH(inuse_takeback, iocg, &now,
1490                                                 iocg->inuse, new_inuse,
1491                                                 hw_inuse, new_hwi);
1492                                 __propagate_active_weight(iocg, iocg->weight,
1493                                                           new_inuse);
1494                         }
1495                 } else {
1496                         /* genuninely out of vtime */
1497                         nr_shortages++;
1498                 }
1499         }
1500 
1501         if (!nr_shortages || !nr_surpluses)
1502                 goto skip_surplus_transfers;
1503 
1504         /* there are both shortages and surpluses, transfer surpluses */
1505         list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
1506                 u32 usage, hw_active, hw_inuse, new_hwi, new_inuse;
1507                 int nr_valid = 0;
1508 
1509                 if (!iocg->has_surplus)
1510                         continue;
1511 
1512                 /* base the decision on max historical usage */
1513                 for (i = 0, usage = 0; i < NR_USAGE_SLOTS; i++) {
1514                         if (iocg->usages[i]) {
1515                                 usage = max(usage, iocg->usages[i]);
1516                                 nr_valid++;
1517                         }
1518                 }
1519                 if (nr_valid < MIN_VALID_USAGES)
1520                         continue;
1521 
1522                 current_hweight(iocg, &hw_active, &hw_inuse);
1523                 new_hwi = surplus_adjusted_hweight_inuse(usage, hw_inuse);
1524                 if (!new_hwi)
1525                         continue;
1526 
1527                 new_inuse = DIV64_U64_ROUND_UP((u64)iocg->inuse * new_hwi,
1528                                                hw_inuse);
1529                 if (new_inuse < iocg->inuse) {
1530                         TRACE_IOCG_PATH(inuse_giveaway, iocg, &now,
1531                                         iocg->inuse, new_inuse,
1532                                         hw_inuse, new_hwi);
1533                         __propagate_active_weight(iocg, iocg->weight, new_inuse);
1534                 }
1535         }
1536 skip_surplus_transfers:
1537         commit_active_weights(ioc);
1538 
1539         /*
1540          * If q is getting clogged or we're missing too much, we're issuing
1541          * too much IO and should lower vtime rate.  If we're not missing
1542          * and experiencing shortages but not surpluses, we're too stingy
1543          * and should increase vtime rate.
1544          */
1545         prev_busy_level = ioc->busy_level;
1546         if (rq_wait_pct > RQ_WAIT_BUSY_PCT ||
1547             missed_ppm[READ] > ppm_rthr ||
1548             missed_ppm[WRITE] > ppm_wthr) {
1549                 ioc->busy_level = max(ioc->busy_level, 0);
1550                 ioc->busy_level++;
1551         } else if (rq_wait_pct <= RQ_WAIT_BUSY_PCT * UNBUSY_THR_PCT / 100 &&
1552                    missed_ppm[READ] <= ppm_rthr * UNBUSY_THR_PCT / 100 &&
1553                    missed_ppm[WRITE] <= ppm_wthr * UNBUSY_THR_PCT / 100) {
1554                 /* take action iff there is contention */
1555                 if (nr_shortages && !nr_lagging) {
1556                         ioc->busy_level = min(ioc->busy_level, 0);
1557                         /* redistribute surpluses first */
1558                         if (!nr_surpluses)
1559                                 ioc->busy_level--;
1560                 }
1561         } else {
1562                 ioc->busy_level = 0;
1563         }
1564 
1565         ioc->busy_level = clamp(ioc->busy_level, -1000, 1000);
1566 
1567         if (ioc->busy_level > 0 || (ioc->busy_level < 0 && !nr_lagging)) {
1568                 u64 vrate = atomic64_read(&ioc->vtime_rate);
1569                 u64 vrate_min = ioc->vrate_min, vrate_max = ioc->vrate_max;
1570 
1571                 /* rq_wait signal is always reliable, ignore user vrate_min */
1572                 if (rq_wait_pct > RQ_WAIT_BUSY_PCT)
1573                         vrate_min = VRATE_MIN;
1574 
1575                 /*
1576                  * If vrate is out of bounds, apply clamp gradually as the
1577                  * bounds can change abruptly.  Otherwise, apply busy_level
1578                  * based adjustment.
1579                  */
1580                 if (vrate < vrate_min) {
1581                         vrate = div64_u64(vrate * (100 + VRATE_CLAMP_ADJ_PCT),
1582                                           100);
1583                         vrate = min(vrate, vrate_min);
1584                 } else if (vrate > vrate_max) {
1585                         vrate = div64_u64(vrate * (100 - VRATE_CLAMP_ADJ_PCT),
1586                                           100);
1587                         vrate = max(vrate, vrate_max);
1588                 } else {
1589                         int idx = min_t(int, abs(ioc->busy_level),
1590                                         ARRAY_SIZE(vrate_adj_pct) - 1);
1591                         u32 adj_pct = vrate_adj_pct[idx];
1592 
1593                         if (ioc->busy_level > 0)
1594                                 adj_pct = 100 - adj_pct;
1595                         else
1596                                 adj_pct = 100 + adj_pct;
1597 
1598                         vrate = clamp(DIV64_U64_ROUND_UP(vrate * adj_pct, 100),
1599                                       vrate_min, vrate_max);
1600                 }
1601 
1602                 trace_iocost_ioc_vrate_adj(ioc, vrate, missed_ppm, rq_wait_pct,
1603                                            nr_lagging, nr_shortages,
1604                                            nr_surpluses);
1605 
1606                 atomic64_set(&ioc->vtime_rate, vrate);
1607                 ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP(
1608                         ioc->period_us * vrate * INUSE_MARGIN_PCT, 100);
1609         } else if (ioc->busy_level != prev_busy_level || nr_lagging) {
1610                 trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
1611                                            missed_ppm, rq_wait_pct, nr_lagging,
1612                                            nr_shortages, nr_surpluses);
1613         }
1614 
1615         ioc_refresh_params(ioc, false);
1616 
1617         /*
1618          * This period is done.  Move onto the next one.  If nothing's
1619          * going on with the device, stop the timer.
1620          */
1621         atomic64_inc(&ioc->cur_period);
1622 
1623         if (ioc->running != IOC_STOP) {
1624                 if (!list_empty(&ioc->active_iocgs)) {
1625                         ioc_start_period(ioc, &now);
1626                 } else {
1627                         ioc->busy_level = 0;
1628                         ioc->running = IOC_IDLE;
1629                 }
1630         }
1631 
1632         spin_unlock_irq(&ioc->lock);
1633 }
1634 
1635 static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg,
1636                                     bool is_merge, u64 *costp)
1637 {
1638         struct ioc *ioc = iocg->ioc;
1639         u64 coef_seqio, coef_randio, coef_page;
1640         u64 pages = max_t(u64, bio_sectors(bio) >> IOC_SECT_TO_PAGE_SHIFT, 1);
1641         u64 seek_pages = 0;
1642         u64 cost = 0;
1643 
1644         switch (bio_op(bio)) {
1645         case REQ_OP_READ:
1646                 coef_seqio      = ioc->params.lcoefs[LCOEF_RSEQIO];
1647                 coef_randio     = ioc->params.lcoefs[LCOEF_RRANDIO];
1648                 coef_page       = ioc->params.lcoefs[LCOEF_RPAGE];
1649                 break;
1650         case REQ_OP_WRITE:
1651                 coef_seqio      = ioc->params.lcoefs[LCOEF_WSEQIO];
1652                 coef_randio     = ioc->params.lcoefs[LCOEF_WRANDIO];
1653                 coef_page       = ioc->params.lcoefs[LCOEF_WPAGE];
1654                 break;
1655         default:
1656                 goto out;
1657         }
1658 
1659         if (iocg->cursor) {
1660                 seek_pages = abs(bio->bi_iter.bi_sector - iocg->cursor);
1661                 seek_pages >>= IOC_SECT_TO_PAGE_SHIFT;
1662         }
1663 
1664         if (!is_merge) {
1665                 if (seek_pages > LCOEF_RANDIO_PAGES) {
1666                         cost += coef_randio;
1667                 } else {
1668                         cost += coef_seqio;
1669                 }
1670         }
1671         cost += pages * coef_page;
1672 out:
1673         *costp = cost;
1674 }
1675 
1676 static u64 calc_vtime_cost(struct bio *bio, struct ioc_gq *iocg, bool is_merge)
1677 {
1678         u64 cost;
1679 
1680         calc_vtime_cost_builtin(bio, iocg, is_merge, &cost);
1681         return cost;
1682 }
1683 
1684 static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
1685 {
1686         struct blkcg_gq *blkg = bio->bi_blkg;
1687         struct ioc *ioc = rqos_to_ioc(rqos);
1688         struct ioc_gq *iocg = blkg_to_iocg(blkg);
1689         struct ioc_now now;
1690         struct iocg_wait wait;
1691         u32 hw_active, hw_inuse;
1692         u64 abs_cost, cost, vtime;
1693 
1694         /* bypass IOs if disabled or for root cgroup */
1695         if (!ioc->enabled || !iocg->level)
1696                 return;
1697 
1698         /* always activate so that even 0 cost IOs get protected to some level */
1699         if (!iocg_activate(iocg, &now))
1700                 return;
1701 
1702         /* calculate the absolute vtime cost */
1703         abs_cost = calc_vtime_cost(bio, iocg, false);
1704         if (!abs_cost)
1705                 return;
1706 
1707         iocg->cursor = bio_end_sector(bio);
1708 
1709         vtime = atomic64_read(&iocg->vtime);
1710         current_hweight(iocg, &hw_active, &hw_inuse);
1711 
1712         if (hw_inuse < hw_active &&
1713             time_after_eq64(vtime + ioc->inuse_margin_vtime, now.vnow)) {
1714                 TRACE_IOCG_PATH(inuse_reset, iocg, &now,
1715                                 iocg->inuse, iocg->weight, hw_inuse, hw_active);
1716                 spin_lock_irq(&ioc->lock);
1717                 propagate_active_weight(iocg, iocg->weight, iocg->weight);
1718                 spin_unlock_irq(&ioc->lock);
1719                 current_hweight(iocg, &hw_active, &hw_inuse);
1720         }
1721 
1722         cost = abs_cost_to_cost(abs_cost, hw_inuse);
1723 
1724         /*
1725          * If no one's waiting and within budget, issue right away.  The
1726          * tests are racy but the races aren't systemic - we only miss once
1727          * in a while which is fine.
1728          */
1729         if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
1730             time_before_eq64(vtime + cost, now.vnow)) {
1731                 iocg_commit_bio(iocg, bio, cost);
1732                 return;
1733         }
1734 
1735         /*
1736          * We activated above but w/o any synchronization. Deactivation is
1737          * synchronized with waitq.lock and we won't get deactivated as long
1738          * as we're waiting or has debt, so we're good if we're activated
1739          * here. In the unlikely case that we aren't, just issue the IO.
1740          */
1741         spin_lock_irq(&iocg->waitq.lock);
1742 
1743         if (unlikely(list_empty(&iocg->active_list))) {
1744                 spin_unlock_irq(&iocg->waitq.lock);
1745                 iocg_commit_bio(iocg, bio, cost);
1746                 return;
1747         }
1748 
1749         /*
1750          * We're over budget. If @bio has to be issued regardless, remember
1751          * the abs_cost instead of advancing vtime. iocg_kick_waitq() will pay
1752          * off the debt before waking more IOs.
1753          *
1754          * This way, the debt is continuously paid off each period with the
1755          * actual budget available to the cgroup. If we just wound vtime, we
1756          * would incorrectly use the current hw_inuse for the entire amount
1757          * which, for example, can lead to the cgroup staying blocked for a
1758          * long time even with substantially raised hw_inuse.
1759          *
1760          * An iocg with vdebt should stay online so that the timer can keep
1761          * deducting its vdebt and [de]activate use_delay mechanism
1762          * accordingly. We don't want to race against the timer trying to
1763          * clear them and leave @iocg inactive w/ dangling use_delay heavily
1764          * penalizing the cgroup and its descendants.
1765          */
1766         if (bio_issue_as_root_blkg(bio) || fatal_signal_pending(current)) {
1767                 iocg->abs_vdebt += abs_cost;
1768                 if (iocg_kick_delay(iocg, &now, cost))
1769                         blkcg_schedule_throttle(rqos->q,
1770                                         (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
1771                 spin_unlock_irq(&iocg->waitq.lock);
1772                 return;
1773         }
1774 
1775         /*
1776          * Append self to the waitq and schedule the wakeup timer if we're
1777          * the first waiter.  The timer duration is calculated based on the
1778          * current vrate.  vtime and hweight changes can make it too short
1779          * or too long.  Each wait entry records the absolute cost it's
1780          * waiting for to allow re-evaluation using a custom wait entry.
1781          *
1782          * If too short, the timer simply reschedules itself.  If too long,
1783          * the period timer will notice and trigger wakeups.
1784          *
1785          * All waiters are on iocg->waitq and the wait states are
1786          * synchronized using waitq.lock.
1787          */
1788         init_waitqueue_func_entry(&wait.wait, iocg_wake_fn);
1789         wait.wait.private = current;
1790         wait.bio = bio;
1791         wait.abs_cost = abs_cost;
1792         wait.committed = false; /* will be set true by waker */
1793 
1794         __add_wait_queue_entry_tail(&iocg->waitq, &wait.wait);
1795         iocg_kick_waitq(iocg, &now);
1796 
1797         spin_unlock_irq(&iocg->waitq.lock);
1798 
1799         while (true) {
1800                 set_current_state(TASK_UNINTERRUPTIBLE);
1801                 if (wait.committed)
1802                         break;
1803                 io_schedule();
1804         }
1805 
1806         /* waker already committed us, proceed */
1807         finish_wait(&iocg->waitq, &wait.wait);
1808 }
1809 
1810 static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
1811                            struct bio *bio)
1812 {
1813         struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
1814         struct ioc *ioc = iocg->ioc;
1815         sector_t bio_end = bio_end_sector(bio);
1816         struct ioc_now now;
1817         u32 hw_inuse;
1818         u64 abs_cost, cost;
1819         unsigned long flags;
1820 
1821         /* bypass if disabled or for root cgroup */
1822         if (!ioc->enabled || !iocg->level)
1823                 return;
1824 
1825         abs_cost = calc_vtime_cost(bio, iocg, true);
1826         if (!abs_cost)
1827                 return;
1828 
1829         ioc_now(ioc, &now);
1830         current_hweight(iocg, NULL, &hw_inuse);
1831         cost = abs_cost_to_cost(abs_cost, hw_inuse);
1832 
1833         /* update cursor if backmerging into the request at the cursor */
1834         if (blk_rq_pos(rq) < bio_end &&
1835             blk_rq_pos(rq) + blk_rq_sectors(rq) == iocg->cursor)
1836                 iocg->cursor = bio_end;
1837 
1838         /*
1839          * Charge if there's enough vtime budget and the existing request has
1840          * cost assigned.
1841          */
1842         if (rq->bio && rq->bio->bi_iocost_cost &&
1843             time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow)) {
1844                 iocg_commit_bio(iocg, bio, cost);
1845                 return;
1846         }
1847 
1848         /*
1849          * Otherwise, account it as debt if @iocg is online, which it should
1850          * be for the vast majority of cases. See debt handling in
1851          * ioc_rqos_throttle() for details.
1852          */
1853         spin_lock_irqsave(&iocg->waitq.lock, flags);
1854         if (likely(!list_empty(&iocg->active_list))) {
1855                 iocg->abs_vdebt += abs_cost;
1856                 iocg_kick_delay(iocg, &now, cost);
1857         } else {
1858                 iocg_commit_bio(iocg, bio, cost);
1859         }
1860         spin_unlock_irqrestore(&iocg->waitq.lock, flags);
1861 }
1862 
1863 static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
1864 {
1865         struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
1866 
1867         if (iocg && bio->bi_iocost_cost)
1868                 atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime);
1869 }
1870 
1871 static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
1872 {
1873         struct ioc *ioc = rqos_to_ioc(rqos);
1874         u64 on_q_ns, rq_wait_ns;
1875         int pidx, rw;
1876 
1877         if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns)
1878                 return;
1879 
1880         switch (req_op(rq) & REQ_OP_MASK) {
1881         case REQ_OP_READ:
1882                 pidx = QOS_RLAT;
1883                 rw = READ;
1884                 break;
1885         case REQ_OP_WRITE:
1886                 pidx = QOS_WLAT;
1887                 rw = WRITE;
1888                 break;
1889         default:
1890                 return;
1891         }
1892 
1893         on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
1894         rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns;
1895 
1896         if (on_q_ns <= ioc->params.qos[pidx] * NSEC_PER_USEC)
1897                 this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_met);
1898         else
1899                 this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_missed);
1900 
1901         this_cpu_add(ioc->pcpu_stat->rq_wait_ns, rq_wait_ns);
1902 }
1903 
1904 static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos)
1905 {
1906         struct ioc *ioc = rqos_to_ioc(rqos);
1907 
1908         spin_lock_irq(&ioc->lock);
1909         ioc_refresh_params(ioc, false);
1910         spin_unlock_irq(&ioc->lock);
1911 }
1912 
1913 static void ioc_rqos_exit(struct rq_qos *rqos)
1914 {
1915         struct ioc *ioc = rqos_to_ioc(rqos);
1916 
1917         blkcg_deactivate_policy(rqos->q, &blkcg_policy_iocost);
1918 
1919         spin_lock_irq(&ioc->lock);
1920         ioc->running = IOC_STOP;
1921         spin_unlock_irq(&ioc->lock);
1922 
1923         del_timer_sync(&ioc->timer);
1924         free_percpu(ioc->pcpu_stat);
1925         kfree(ioc);
1926 }
1927 
1928 static struct rq_qos_ops ioc_rqos_ops = {
1929         .throttle = ioc_rqos_throttle,
1930         .merge = ioc_rqos_merge,
1931         .done_bio = ioc_rqos_done_bio,
1932         .done = ioc_rqos_done,
1933         .queue_depth_changed = ioc_rqos_queue_depth_changed,
1934         .exit = ioc_rqos_exit,
1935 };
1936 
1937 static int blk_iocost_init(struct request_queue *q)
1938 {
1939         struct ioc *ioc;
1940         struct rq_qos *rqos;
1941         int ret;
1942 
1943         ioc = kzalloc(sizeof(*ioc), GFP_KERNEL);
1944         if (!ioc)
1945                 return -ENOMEM;
1946 
1947         ioc->pcpu_stat = alloc_percpu(struct ioc_pcpu_stat);
1948         if (!ioc->pcpu_stat) {
1949                 kfree(ioc);
1950                 return -ENOMEM;
1951         }
1952 
1953         rqos = &ioc->rqos;
1954         rqos->id = RQ_QOS_COST;
1955         rqos->ops = &ioc_rqos_ops;
1956         rqos->q = q;
1957 
1958         spin_lock_init(&ioc->lock);
1959         timer_setup(&ioc->timer, ioc_timer_fn, 0);
1960         INIT_LIST_HEAD(&ioc->active_iocgs);
1961 
1962         ioc->running = IOC_IDLE;
1963         atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
1964         seqcount_init(&ioc->period_seqcount);
1965         ioc->period_at = ktime_to_us(ktime_get());
1966         atomic64_set(&ioc->cur_period, 0);
1967         atomic_set(&ioc->hweight_gen, 0);
1968 
1969         spin_lock_irq(&ioc->lock);
1970         ioc->autop_idx = AUTOP_INVALID;
1971         ioc_refresh_params(ioc, true);
1972         spin_unlock_irq(&ioc->lock);
1973 
1974         rq_qos_add(q, rqos);
1975         ret = blkcg_activate_policy(q, &blkcg_policy_iocost);
1976         if (ret) {
1977                 rq_qos_del(q, rqos);
1978                 free_percpu(ioc->pcpu_stat);
1979                 kfree(ioc);
1980                 return ret;
1981         }
1982         return 0;
1983 }
1984 
1985 static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp)
1986 {
1987         struct ioc_cgrp *iocc;
1988 
1989         iocc = kzalloc(sizeof(struct ioc_cgrp), gfp);
1990         if (!iocc)
1991                 return NULL;
1992 
1993         iocc->dfl_weight = CGROUP_WEIGHT_DFL;
1994         return &iocc->cpd;
1995 }
1996 
1997 static void ioc_cpd_free(struct blkcg_policy_data *cpd)
1998 {
1999         kfree(container_of(cpd, struct ioc_cgrp, cpd));
2000 }
2001 
2002 static struct blkg_policy_data *ioc_pd_alloc(gfp_t gfp, struct request_queue *q,
2003                                              struct blkcg *blkcg)
2004 {
2005         int levels = blkcg->css.cgroup->level + 1;
2006         struct ioc_gq *iocg;
2007 
2008         iocg = kzalloc_node(sizeof(*iocg) + levels * sizeof(iocg->ancestors[0]),
2009                             gfp, q->node);
2010         if (!iocg)
2011                 return NULL;
2012 
2013         return &iocg->pd;
2014 }
2015 
2016 static void ioc_pd_init(struct blkg_policy_data *pd)
2017 {
2018         struct ioc_gq *iocg = pd_to_iocg(pd);
2019         struct blkcg_gq *blkg = pd_to_blkg(&iocg->pd);
2020         struct ioc *ioc = q_to_ioc(blkg->q);
2021         struct ioc_now now;
2022         struct blkcg_gq *tblkg;
2023         unsigned long flags;
2024 
2025         ioc_now(ioc, &now);
2026 
2027         iocg->ioc = ioc;
2028         atomic64_set(&iocg->vtime, now.vnow);
2029         atomic64_set(&iocg->done_vtime, now.vnow);
2030         atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period));
2031         INIT_LIST_HEAD(&iocg->active_list);
2032         iocg->hweight_active = HWEIGHT_WHOLE;
2033         iocg->hweight_inuse = HWEIGHT_WHOLE;
2034 
2035         init_waitqueue_head(&iocg->waitq);
2036         hrtimer_init(&iocg->waitq_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
2037         iocg->waitq_timer.function = iocg_waitq_timer_fn;
2038         hrtimer_init(&iocg->delay_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
2039         iocg->delay_timer.function = iocg_delay_timer_fn;
2040 
2041         iocg->level = blkg->blkcg->css.cgroup->level;
2042 
2043         for (tblkg = blkg; tblkg; tblkg = tblkg->parent) {
2044                 struct ioc_gq *tiocg = blkg_to_iocg(tblkg);
2045                 iocg->ancestors[tiocg->level] = tiocg;
2046         }
2047 
2048         spin_lock_irqsave(&ioc->lock, flags);
2049         weight_updated(iocg);
2050         spin_unlock_irqrestore(&ioc->lock, flags);
2051 }
2052 
2053 static void ioc_pd_free(struct blkg_policy_data *pd)
2054 {
2055         struct ioc_gq *iocg = pd_to_iocg(pd);
2056         struct ioc *ioc = iocg->ioc;
2057 
2058         if (ioc) {
2059                 spin_lock(&ioc->lock);
2060                 if (!list_empty(&iocg->active_list)) {
2061                         propagate_active_weight(iocg, 0, 0);
2062                         list_del_init(&iocg->active_list);
2063                 }
2064                 spin_unlock(&ioc->lock);
2065 
2066                 hrtimer_cancel(&iocg->waitq_timer);
2067                 hrtimer_cancel(&iocg->delay_timer);
2068         }
2069         kfree(iocg);
2070 }
2071 
2072 static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
2073                              int off)
2074 {
2075         const char *dname = blkg_dev_name(pd->blkg);
2076         struct ioc_gq *iocg = pd_to_iocg(pd);
2077 
2078         if (dname && iocg->cfg_weight)
2079                 seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight);
2080         return 0;
2081 }
2082 
2083 
2084 static int ioc_weight_show(struct seq_file *sf, void *v)
2085 {
2086         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
2087         struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
2088 
2089         seq_printf(sf, "default %u\n", iocc->dfl_weight);
2090         blkcg_print_blkgs(sf, blkcg, ioc_weight_prfill,
2091                           &blkcg_policy_iocost, seq_cft(sf)->private, false);
2092         return 0;
2093 }
2094 
2095 static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
2096                                 size_t nbytes, loff_t off)
2097 {
2098         struct blkcg *blkcg = css_to_blkcg(of_css(of));
2099         struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
2100         struct blkg_conf_ctx ctx;
2101         struct ioc_gq *iocg;
2102         u32 v;
2103         int ret;
2104 
2105         if (!strchr(buf, ':')) {
2106                 struct blkcg_gq *blkg;
2107 
2108                 if (!sscanf(buf, "default %u", &v) && !sscanf(buf, "%u", &v))
2109                         return -EINVAL;
2110 
2111                 if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
2112                         return -EINVAL;
2113 
2114                 spin_lock(&blkcg->lock);
2115                 iocc->dfl_weight = v;
2116                 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
2117                         struct ioc_gq *iocg = blkg_to_iocg(blkg);
2118 
2119                         if (iocg) {
2120                                 spin_lock_irq(&iocg->ioc->lock);
2121                                 weight_updated(iocg);
2122                                 spin_unlock_irq(&iocg->ioc->lock);
2123                         }
2124                 }
2125                 spin_unlock(&blkcg->lock);
2126 
2127                 return nbytes;
2128         }
2129 
2130         ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, buf, &ctx);
2131         if (ret)
2132                 return ret;
2133 
2134         iocg = blkg_to_iocg(ctx.blkg);
2135 
2136         if (!strncmp(ctx.body, "default", 7)) {
2137                 v = 0;
2138         } else {
2139                 if (!sscanf(ctx.body, "%u", &v))
2140                         goto einval;
2141                 if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
2142                         goto einval;
2143         }
2144 
2145         spin_lock(&iocg->ioc->lock);
2146         iocg->cfg_weight = v;
2147         weight_updated(iocg);
2148         spin_unlock(&iocg->ioc->lock);
2149 
2150         blkg_conf_finish(&ctx);
2151         return nbytes;
2152 
2153 einval:
2154         blkg_conf_finish(&ctx);
2155         return -EINVAL;
2156 }
2157 
2158 static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
2159                           int off)
2160 {
2161         const char *dname = blkg_dev_name(pd->blkg);
2162         struct ioc *ioc = pd_to_iocg(pd)->ioc;
2163 
2164         if (!dname)
2165                 return 0;
2166 
2167         seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n",
2168                    dname, ioc->enabled, ioc->user_qos_params ? "user" : "auto",
2169                    ioc->params.qos[QOS_RPPM] / 10000,
2170                    ioc->params.qos[QOS_RPPM] % 10000 / 100,
2171                    ioc->params.qos[QOS_RLAT],
2172                    ioc->params.qos[QOS_WPPM] / 10000,
2173                    ioc->params.qos[QOS_WPPM] % 10000 / 100,
2174                    ioc->params.qos[QOS_WLAT],
2175                    ioc->params.qos[QOS_MIN] / 10000,
2176                    ioc->params.qos[QOS_MIN] % 10000 / 100,
2177                    ioc->params.qos[QOS_MAX] / 10000,
2178                    ioc->params.qos[QOS_MAX] % 10000 / 100);
2179         return 0;
2180 }
2181 
2182 static int ioc_qos_show(struct seq_file *sf, void *v)
2183 {
2184         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
2185 
2186         blkcg_print_blkgs(sf, blkcg, ioc_qos_prfill,
2187                           &blkcg_policy_iocost, seq_cft(sf)->private, false);
2188         return 0;
2189 }
2190 
2191 static const match_table_t qos_ctrl_tokens = {
2192         { QOS_ENABLE,           "enable=%u"     },
2193         { QOS_CTRL,             "ctrl=%s"       },
2194         { NR_QOS_CTRL_PARAMS,   NULL            },
2195 };
2196 
2197 static const match_table_t qos_tokens = {
2198         { QOS_RPPM,             "rpct=%s"       },
2199         { QOS_RLAT,             "rlat=%u"       },
2200         { QOS_WPPM,             "wpct=%s"       },
2201         { QOS_WLAT,             "wlat=%u"       },
2202         { QOS_MIN,              "min=%s"        },
2203         { QOS_MAX,              "max=%s"        },
2204         { NR_QOS_PARAMS,        NULL            },
2205 };
2206 
2207 static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
2208                              size_t nbytes, loff_t off)
2209 {
2210         struct gendisk *disk;
2211         struct ioc *ioc;
2212         u32 qos[NR_QOS_PARAMS];
2213         bool enable, user;
2214         char *p;
2215         int ret;
2216 
2217         disk = blkcg_conf_get_disk(&input);
2218         if (IS_ERR(disk))
2219                 return PTR_ERR(disk);
2220 
2221         ioc = q_to_ioc(disk->queue);
2222         if (!ioc) {
2223                 ret = blk_iocost_init(disk->queue);
2224                 if (ret)
2225                         goto err;
2226                 ioc = q_to_ioc(disk->queue);
2227         }
2228 
2229         spin_lock_irq(&ioc->lock);
2230         memcpy(qos, ioc->params.qos, sizeof(qos));
2231         enable = ioc->enabled;
2232         user = ioc->user_qos_params;
2233         spin_unlock_irq(&ioc->lock);
2234 
2235         while ((p = strsep(&input, " \t\n"))) {
2236                 substring_t args[MAX_OPT_ARGS];
2237                 char buf[32];
2238                 int tok;
2239                 s64 v;
2240 
2241                 if (!*p)
2242                         continue;
2243 
2244                 switch (match_token(p, qos_ctrl_tokens, args)) {
2245                 case QOS_ENABLE:
2246                         match_u64(&args[0], &v);
2247                         enable = v;
2248                         continue;
2249                 case QOS_CTRL:
2250                         match_strlcpy(buf, &args[0], sizeof(buf));
2251                         if (!strcmp(buf, "auto"))
2252                                 user = false;
2253                         else if (!strcmp(buf, "user"))
2254                                 user = true;
2255                         else
2256                                 goto einval;
2257                         continue;
2258                 }
2259 
2260                 tok = match_token(p, qos_tokens, args);
2261                 switch (tok) {
2262                 case QOS_RPPM:
2263                 case QOS_WPPM:
2264                         if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
2265                             sizeof(buf))
2266                                 goto einval;
2267                         if (cgroup_parse_float(buf, 2, &v))
2268                                 goto einval;
2269                         if (v < 0 || v > 10000)
2270                                 goto einval;
2271                         qos[tok] = v * 100;
2272                         break;
2273                 case QOS_RLAT:
2274                 case QOS_WLAT:
2275                         if (match_u64(&args[0], &v))
2276                                 goto einval;
2277                         qos[tok] = v;
2278                         break;
2279                 case QOS_MIN:
2280                 case QOS_MAX:
2281                         if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
2282                             sizeof(buf))
2283                                 goto einval;
2284                         if (cgroup_parse_float(buf, 2, &v))
2285                                 goto einval;
2286                         if (v < 0)
2287                                 goto einval;
2288                         qos[tok] = clamp_t(s64, v * 100,
2289                                            VRATE_MIN_PPM, VRATE_MAX_PPM);
2290                         break;
2291                 default:
2292                         goto einval;
2293                 }
2294                 user = true;
2295         }
2296 
2297         if (qos[QOS_MIN] > qos[QOS_MAX])
2298                 goto einval;
2299 
2300         spin_lock_irq(&ioc->lock);
2301 
2302         if (enable) {
2303                 blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q);
2304                 ioc->enabled = true;
2305         } else {
2306                 blk_queue_flag_clear(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q);
2307                 ioc->enabled = false;
2308         }
2309 
2310         if (user) {
2311                 memcpy(ioc->params.qos, qos, sizeof(qos));
2312                 ioc->user_qos_params = true;
2313         } else {
2314                 ioc->user_qos_params = false;
2315         }
2316 
2317         ioc_refresh_params(ioc, true);
2318         spin_unlock_irq(&ioc->lock);
2319 
2320         put_disk_and_module(disk);
2321         return nbytes;
2322 einval:
2323         ret = -EINVAL;
2324 err:
2325         put_disk_and_module(disk);
2326         return ret;
2327 }
2328 
2329 static u64 ioc_cost_model_prfill(struct seq_file *sf,
2330                                  struct blkg_policy_data *pd, int off)
2331 {
2332         const char *dname = blkg_dev_name(pd->blkg);
2333         struct ioc *ioc = pd_to_iocg(pd)->ioc;
2334         u64 *u = ioc->params.i_lcoefs;
2335 
2336         if (!dname)
2337                 return 0;
2338 
2339         seq_printf(sf, "%s ctrl=%s model=linear "
2340                    "rbps=%llu rseqiops=%llu rrandiops=%llu "
2341                    "wbps=%llu wseqiops=%llu wrandiops=%llu\n",
2342                    dname, ioc->user_cost_model ? "user" : "auto",
2343                    u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
2344                    u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS]);
2345         return 0;
2346 }
2347 
2348 static int ioc_cost_model_show(struct seq_file *sf, void *v)
2349 {
2350         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
2351 
2352         blkcg_print_blkgs(sf, blkcg, ioc_cost_model_prfill,
2353                           &blkcg_policy_iocost, seq_cft(sf)->private, false);
2354         return 0;
2355 }
2356 
2357 static const match_table_t cost_ctrl_tokens = {
2358         { COST_CTRL,            "ctrl=%s"       },
2359         { COST_MODEL,           "model=%s"      },
2360         { NR_COST_CTRL_PARAMS,  NULL            },
2361 };
2362 
2363 static const match_table_t i_lcoef_tokens = {
2364         { I_LCOEF_RBPS,         "rbps=%u"       },
2365         { I_LCOEF_RSEQIOPS,     "rseqiops=%u"   },
2366         { I_LCOEF_RRANDIOPS,    "rrandiops=%u"  },
2367         { I_LCOEF_WBPS,         "wbps=%u"       },
2368         { I_LCOEF_WSEQIOPS,     "wseqiops=%u"   },
2369         { I_LCOEF_WRANDIOPS,    "wrandiops=%u"  },
2370         { NR_I_LCOEFS,          NULL            },
2371 };
2372 
2373 static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
2374                                     size_t nbytes, loff_t off)
2375 {
2376         struct gendisk *disk;
2377         struct ioc *ioc;
2378         u64 u[NR_I_LCOEFS];
2379         bool user;
2380         char *p;
2381         int ret;
2382 
2383         disk = blkcg_conf_get_disk(&input);
2384         if (IS_ERR(disk))
2385                 return PTR_ERR(disk);
2386 
2387         ioc = q_to_ioc(disk->queue);
2388         if (!ioc) {
2389                 ret = blk_iocost_init(disk->queue);
2390                 if (ret)
2391                         goto err;
2392                 ioc = q_to_ioc(disk->queue);
2393         }
2394 
2395         spin_lock_irq(&ioc->lock);
2396         memcpy(u, ioc->params.i_lcoefs, sizeof(u));
2397         user = ioc->user_cost_model;
2398         spin_unlock_irq(&ioc->lock);
2399 
2400         while ((p = strsep(&input, " \t\n"))) {
2401                 substring_t args[MAX_OPT_ARGS];
2402                 char buf[32];
2403                 int tok;
2404                 u64 v;
2405 
2406                 if (!*p)
2407                         continue;
2408 
2409                 switch (match_token(p, cost_ctrl_tokens, args)) {
2410                 case COST_CTRL:
2411                         match_strlcpy(buf, &args[0], sizeof(buf));
2412                         if (!strcmp(buf, "auto"))
2413                                 user = false;
2414                         else if (!strcmp(buf, "user"))
2415                                 user = true;
2416                         else
2417                                 goto einval;
2418                         continue;
2419                 case COST_MODEL:
2420                         match_strlcpy(buf, &args[0], sizeof(buf));
2421                         if (strcmp(buf, "linear"))
2422                                 goto einval;
2423                         continue;
2424                 }
2425 
2426                 tok = match_token(p, i_lcoef_tokens, args);
2427                 if (tok == NR_I_LCOEFS)
2428                         goto einval;
2429                 if (match_u64(&args[0], &v))
2430                         goto einval;
2431                 u[tok] = v;
2432                 user = true;
2433         }
2434 
2435         spin_lock_irq(&ioc->lock);
2436         if (user) {
2437                 memcpy(ioc->params.i_lcoefs, u, sizeof(u));
2438                 ioc->user_cost_model = true;
2439         } else {
2440                 ioc->user_cost_model = false;
2441         }
2442         ioc_refresh_params(ioc, true);
2443         spin_unlock_irq(&ioc->lock);
2444 
2445         put_disk_and_module(disk);
2446         return nbytes;
2447 
2448 einval:
2449         ret = -EINVAL;
2450 err:
2451         put_disk_and_module(disk);
2452         return ret;
2453 }
2454 
2455 static struct cftype ioc_files[] = {
2456         {
2457                 .name = "weight",
2458                 .flags = CFTYPE_NOT_ON_ROOT,
2459                 .seq_show = ioc_weight_show,
2460                 .write = ioc_weight_write,
2461         },
2462         {
2463                 .name = "cost.qos",
2464                 .flags = CFTYPE_ONLY_ON_ROOT,
2465                 .seq_show = ioc_qos_show,
2466                 .write = ioc_qos_write,
2467         },
2468         {
2469                 .name = "cost.model",
2470                 .flags = CFTYPE_ONLY_ON_ROOT,
2471                 .seq_show = ioc_cost_model_show,
2472                 .write = ioc_cost_model_write,
2473         },
2474         {}
2475 };
2476 
2477 static struct blkcg_policy blkcg_policy_iocost = {
2478         .dfl_cftypes    = ioc_files,
2479         .cpd_alloc_fn   = ioc_cpd_alloc,
2480         .cpd_free_fn    = ioc_cpd_free,
2481         .pd_alloc_fn    = ioc_pd_alloc,
2482         .pd_init_fn     = ioc_pd_init,
2483         .pd_free_fn     = ioc_pd_free,
2484 };
2485 
2486 static int __init ioc_init(void)
2487 {
2488         return blkcg_policy_register(&blkcg_policy_iocost);
2489 }
2490 
2491 static void __exit ioc_exit(void)
2492 {
2493         return blkcg_policy_unregister(&blkcg_policy_iocost);
2494 }
2495 
2496 module_init(ioc_init);
2497 module_exit(ioc_exit);
2498 

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