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

Version: ~ [ linux-5.10-rc1 ] ~ [ linux-5.9.1 ] ~ [ linux-5.8.16 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.72 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.152 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.202 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.240 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.240 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.85 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Interface for controlling IO bandwidth on a request queue
  3  *
  4  * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
  5  */
  6 
  7 #include <linux/module.h>
  8 #include <linux/slab.h>
  9 #include <linux/blkdev.h>
 10 #include <linux/bio.h>
 11 #include <linux/blktrace_api.h>
 12 #include "blk-cgroup.h"
 13 #include "blk.h"
 14 
 15 /* Max dispatch from a group in 1 round */
 16 static int throtl_grp_quantum = 8;
 17 
 18 /* Total max dispatch from all groups in one round */
 19 static int throtl_quantum = 32;
 20 
 21 /* Throttling is performed over 100ms slice and after that slice is renewed */
 22 static unsigned long throtl_slice = HZ/10;      /* 100 ms */
 23 
 24 static struct blkcg_policy blkcg_policy_throtl;
 25 
 26 /* A workqueue to queue throttle related work */
 27 static struct workqueue_struct *kthrotld_workqueue;
 28 static void throtl_schedule_delayed_work(struct throtl_data *td,
 29                                 unsigned long delay);
 30 
 31 struct throtl_rb_root {
 32         struct rb_root rb;
 33         struct rb_node *left;
 34         unsigned int count;
 35         unsigned long min_disptime;
 36 };
 37 
 38 #define THROTL_RB_ROOT  (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
 39                         .count = 0, .min_disptime = 0}
 40 
 41 #define rb_entry_tg(node)       rb_entry((node), struct throtl_grp, rb_node)
 42 
 43 /* Per-cpu group stats */
 44 struct tg_stats_cpu {
 45         /* total bytes transferred */
 46         struct blkg_rwstat              service_bytes;
 47         /* total IOs serviced, post merge */
 48         struct blkg_rwstat              serviced;
 49 };
 50 
 51 struct throtl_grp {
 52         /* must be the first member */
 53         struct blkg_policy_data pd;
 54 
 55         /* active throtl group service_tree member */
 56         struct rb_node rb_node;
 57 
 58         /*
 59          * Dispatch time in jiffies. This is the estimated time when group
 60          * will unthrottle and is ready to dispatch more bio. It is used as
 61          * key to sort active groups in service tree.
 62          */
 63         unsigned long disptime;
 64 
 65         unsigned int flags;
 66 
 67         /* Two lists for READ and WRITE */
 68         struct bio_list bio_lists[2];
 69 
 70         /* Number of queued bios on READ and WRITE lists */
 71         unsigned int nr_queued[2];
 72 
 73         /* bytes per second rate limits */
 74         uint64_t bps[2];
 75 
 76         /* IOPS limits */
 77         unsigned int iops[2];
 78 
 79         /* Number of bytes disptached in current slice */
 80         uint64_t bytes_disp[2];
 81         /* Number of bio's dispatched in current slice */
 82         unsigned int io_disp[2];
 83 
 84         /* When did we start a new slice */
 85         unsigned long slice_start[2];
 86         unsigned long slice_end[2];
 87 
 88         /* Some throttle limits got updated for the group */
 89         int limits_changed;
 90 
 91         /* Per cpu stats pointer */
 92         struct tg_stats_cpu __percpu *stats_cpu;
 93 
 94         /* List of tgs waiting for per cpu stats memory to be allocated */
 95         struct list_head stats_alloc_node;
 96 };
 97 
 98 struct throtl_data
 99 {
100         /* service tree for active throtl groups */
101         struct throtl_rb_root tg_service_tree;
102 
103         struct request_queue *queue;
104 
105         /* Total Number of queued bios on READ and WRITE lists */
106         unsigned int nr_queued[2];
107 
108         /*
109          * number of total undestroyed groups
110          */
111         unsigned int nr_undestroyed_grps;
112 
113         /* Work for dispatching throttled bios */
114         struct delayed_work throtl_work;
115 
116         int limits_changed;
117 };
118 
119 /* list and work item to allocate percpu group stats */
120 static DEFINE_SPINLOCK(tg_stats_alloc_lock);
121 static LIST_HEAD(tg_stats_alloc_list);
122 
123 static void tg_stats_alloc_fn(struct work_struct *);
124 static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
125 
126 static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
127 {
128         return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
129 }
130 
131 static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
132 {
133         return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
134 }
135 
136 static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
137 {
138         return pd_to_blkg(&tg->pd);
139 }
140 
141 static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
142 {
143         return blkg_to_tg(td->queue->root_blkg);
144 }
145 
146 enum tg_state_flags {
147         THROTL_TG_FLAG_on_rr = 0,       /* on round-robin busy list */
148 };
149 
150 #define THROTL_TG_FNS(name)                                             \
151 static inline void throtl_mark_tg_##name(struct throtl_grp *tg)         \
152 {                                                                       \
153         (tg)->flags |= (1 << THROTL_TG_FLAG_##name);                    \
154 }                                                                       \
155 static inline void throtl_clear_tg_##name(struct throtl_grp *tg)        \
156 {                                                                       \
157         (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name);                   \
158 }                                                                       \
159 static inline int throtl_tg_##name(const struct throtl_grp *tg)         \
160 {                                                                       \
161         return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0;       \
162 }
163 
164 THROTL_TG_FNS(on_rr);
165 
166 #define throtl_log_tg(td, tg, fmt, args...)     do {                    \
167         char __pbuf[128];                                               \
168                                                                         \
169         blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf));              \
170         blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \
171 } while (0)
172 
173 #define throtl_log(td, fmt, args...)    \
174         blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
175 
176 static inline unsigned int total_nr_queued(struct throtl_data *td)
177 {
178         return td->nr_queued[0] + td->nr_queued[1];
179 }
180 
181 /*
182  * Worker for allocating per cpu stat for tgs. This is scheduled on the
183  * system_wq once there are some groups on the alloc_list waiting for
184  * allocation.
185  */
186 static void tg_stats_alloc_fn(struct work_struct *work)
187 {
188         static struct tg_stats_cpu *stats_cpu;  /* this fn is non-reentrant */
189         struct delayed_work *dwork = to_delayed_work(work);
190         bool empty = false;
191 
192 alloc_stats:
193         if (!stats_cpu) {
194                 stats_cpu = alloc_percpu(struct tg_stats_cpu);
195                 if (!stats_cpu) {
196                         /* allocation failed, try again after some time */
197                         schedule_delayed_work(dwork, msecs_to_jiffies(10));
198                         return;
199                 }
200         }
201 
202         spin_lock_irq(&tg_stats_alloc_lock);
203 
204         if (!list_empty(&tg_stats_alloc_list)) {
205                 struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
206                                                          struct throtl_grp,
207                                                          stats_alloc_node);
208                 swap(tg->stats_cpu, stats_cpu);
209                 list_del_init(&tg->stats_alloc_node);
210         }
211 
212         empty = list_empty(&tg_stats_alloc_list);
213         spin_unlock_irq(&tg_stats_alloc_lock);
214         if (!empty)
215                 goto alloc_stats;
216 }
217 
218 static void throtl_pd_init(struct blkcg_gq *blkg)
219 {
220         struct throtl_grp *tg = blkg_to_tg(blkg);
221         unsigned long flags;
222 
223         RB_CLEAR_NODE(&tg->rb_node);
224         bio_list_init(&tg->bio_lists[0]);
225         bio_list_init(&tg->bio_lists[1]);
226         tg->limits_changed = false;
227 
228         tg->bps[READ] = -1;
229         tg->bps[WRITE] = -1;
230         tg->iops[READ] = -1;
231         tg->iops[WRITE] = -1;
232 
233         /*
234          * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
235          * but percpu allocator can't be called from IO path.  Queue tg on
236          * tg_stats_alloc_list and allocate from work item.
237          */
238         spin_lock_irqsave(&tg_stats_alloc_lock, flags);
239         list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
240         schedule_delayed_work(&tg_stats_alloc_work, 0);
241         spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
242 }
243 
244 static void throtl_pd_exit(struct blkcg_gq *blkg)
245 {
246         struct throtl_grp *tg = blkg_to_tg(blkg);
247         unsigned long flags;
248 
249         spin_lock_irqsave(&tg_stats_alloc_lock, flags);
250         list_del_init(&tg->stats_alloc_node);
251         spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
252 
253         free_percpu(tg->stats_cpu);
254 }
255 
256 static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
257 {
258         struct throtl_grp *tg = blkg_to_tg(blkg);
259         int cpu;
260 
261         if (tg->stats_cpu == NULL)
262                 return;
263 
264         for_each_possible_cpu(cpu) {
265                 struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
266 
267                 blkg_rwstat_reset(&sc->service_bytes);
268                 blkg_rwstat_reset(&sc->serviced);
269         }
270 }
271 
272 static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
273                                            struct blkcg *blkcg)
274 {
275         /*
276          * This is the common case when there are no blkcgs.  Avoid lookup
277          * in this case
278          */
279         if (blkcg == &blkcg_root)
280                 return td_root_tg(td);
281 
282         return blkg_to_tg(blkg_lookup(blkcg, td->queue));
283 }
284 
285 static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
286                                                   struct blkcg *blkcg)
287 {
288         struct request_queue *q = td->queue;
289         struct throtl_grp *tg = NULL;
290 
291         /*
292          * This is the common case when there are no blkcgs.  Avoid lookup
293          * in this case
294          */
295         if (blkcg == &blkcg_root) {
296                 tg = td_root_tg(td);
297         } else {
298                 struct blkcg_gq *blkg;
299 
300                 blkg = blkg_lookup_create(blkcg, q);
301 
302                 /* if %NULL and @q is alive, fall back to root_tg */
303                 if (!IS_ERR(blkg))
304                         tg = blkg_to_tg(blkg);
305                 else if (!blk_queue_dying(q))
306                         tg = td_root_tg(td);
307         }
308 
309         return tg;
310 }
311 
312 static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
313 {
314         /* Service tree is empty */
315         if (!root->count)
316                 return NULL;
317 
318         if (!root->left)
319                 root->left = rb_first(&root->rb);
320 
321         if (root->left)
322                 return rb_entry_tg(root->left);
323 
324         return NULL;
325 }
326 
327 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
328 {
329         rb_erase(n, root);
330         RB_CLEAR_NODE(n);
331 }
332 
333 static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
334 {
335         if (root->left == n)
336                 root->left = NULL;
337         rb_erase_init(n, &root->rb);
338         --root->count;
339 }
340 
341 static void update_min_dispatch_time(struct throtl_rb_root *st)
342 {
343         struct throtl_grp *tg;
344 
345         tg = throtl_rb_first(st);
346         if (!tg)
347                 return;
348 
349         st->min_disptime = tg->disptime;
350 }
351 
352 static void
353 tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
354 {
355         struct rb_node **node = &st->rb.rb_node;
356         struct rb_node *parent = NULL;
357         struct throtl_grp *__tg;
358         unsigned long key = tg->disptime;
359         int left = 1;
360 
361         while (*node != NULL) {
362                 parent = *node;
363                 __tg = rb_entry_tg(parent);
364 
365                 if (time_before(key, __tg->disptime))
366                         node = &parent->rb_left;
367                 else {
368                         node = &parent->rb_right;
369                         left = 0;
370                 }
371         }
372 
373         if (left)
374                 st->left = &tg->rb_node;
375 
376         rb_link_node(&tg->rb_node, parent, node);
377         rb_insert_color(&tg->rb_node, &st->rb);
378 }
379 
380 static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
381 {
382         struct throtl_rb_root *st = &td->tg_service_tree;
383 
384         tg_service_tree_add(st, tg);
385         throtl_mark_tg_on_rr(tg);
386         st->count++;
387 }
388 
389 static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
390 {
391         if (!throtl_tg_on_rr(tg))
392                 __throtl_enqueue_tg(td, tg);
393 }
394 
395 static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
396 {
397         throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
398         throtl_clear_tg_on_rr(tg);
399 }
400 
401 static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
402 {
403         if (throtl_tg_on_rr(tg))
404                 __throtl_dequeue_tg(td, tg);
405 }
406 
407 static void throtl_schedule_next_dispatch(struct throtl_data *td)
408 {
409         struct throtl_rb_root *st = &td->tg_service_tree;
410 
411         /*
412          * If there are more bios pending, schedule more work.
413          */
414         if (!total_nr_queued(td))
415                 return;
416 
417         BUG_ON(!st->count);
418 
419         update_min_dispatch_time(st);
420 
421         if (time_before_eq(st->min_disptime, jiffies))
422                 throtl_schedule_delayed_work(td, 0);
423         else
424                 throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
425 }
426 
427 static inline void
428 throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
429 {
430         tg->bytes_disp[rw] = 0;
431         tg->io_disp[rw] = 0;
432         tg->slice_start[rw] = jiffies;
433         tg->slice_end[rw] = jiffies + throtl_slice;
434         throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
435                         rw == READ ? 'R' : 'W', tg->slice_start[rw],
436                         tg->slice_end[rw], jiffies);
437 }
438 
439 static inline void throtl_set_slice_end(struct throtl_data *td,
440                 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
441 {
442         tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
443 }
444 
445 static inline void throtl_extend_slice(struct throtl_data *td,
446                 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
447 {
448         tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
449         throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
450                         rw == READ ? 'R' : 'W', tg->slice_start[rw],
451                         tg->slice_end[rw], jiffies);
452 }
453 
454 /* Determine if previously allocated or extended slice is complete or not */
455 static bool
456 throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
457 {
458         if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
459                 return 0;
460 
461         return 1;
462 }
463 
464 /* Trim the used slices and adjust slice start accordingly */
465 static inline void
466 throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
467 {
468         unsigned long nr_slices, time_elapsed, io_trim;
469         u64 bytes_trim, tmp;
470 
471         BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
472 
473         /*
474          * If bps are unlimited (-1), then time slice don't get
475          * renewed. Don't try to trim the slice if slice is used. A new
476          * slice will start when appropriate.
477          */
478         if (throtl_slice_used(td, tg, rw))
479                 return;
480 
481         /*
482          * A bio has been dispatched. Also adjust slice_end. It might happen
483          * that initially cgroup limit was very low resulting in high
484          * slice_end, but later limit was bumped up and bio was dispached
485          * sooner, then we need to reduce slice_end. A high bogus slice_end
486          * is bad because it does not allow new slice to start.
487          */
488 
489         throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
490 
491         time_elapsed = jiffies - tg->slice_start[rw];
492 
493         nr_slices = time_elapsed / throtl_slice;
494 
495         if (!nr_slices)
496                 return;
497         tmp = tg->bps[rw] * throtl_slice * nr_slices;
498         do_div(tmp, HZ);
499         bytes_trim = tmp;
500 
501         io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
502 
503         if (!bytes_trim && !io_trim)
504                 return;
505 
506         if (tg->bytes_disp[rw] >= bytes_trim)
507                 tg->bytes_disp[rw] -= bytes_trim;
508         else
509                 tg->bytes_disp[rw] = 0;
510 
511         if (tg->io_disp[rw] >= io_trim)
512                 tg->io_disp[rw] -= io_trim;
513         else
514                 tg->io_disp[rw] = 0;
515 
516         tg->slice_start[rw] += nr_slices * throtl_slice;
517 
518         throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
519                         " start=%lu end=%lu jiffies=%lu",
520                         rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
521                         tg->slice_start[rw], tg->slice_end[rw], jiffies);
522 }
523 
524 static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
525                 struct bio *bio, unsigned long *wait)
526 {
527         bool rw = bio_data_dir(bio);
528         unsigned int io_allowed;
529         unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
530         u64 tmp;
531 
532         jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
533 
534         /* Slice has just started. Consider one slice interval */
535         if (!jiffy_elapsed)
536                 jiffy_elapsed_rnd = throtl_slice;
537 
538         jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
539 
540         /*
541          * jiffy_elapsed_rnd should not be a big value as minimum iops can be
542          * 1 then at max jiffy elapsed should be equivalent of 1 second as we
543          * will allow dispatch after 1 second and after that slice should
544          * have been trimmed.
545          */
546 
547         tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
548         do_div(tmp, HZ);
549 
550         if (tmp > UINT_MAX)
551                 io_allowed = UINT_MAX;
552         else
553                 io_allowed = tmp;
554 
555         if (tg->io_disp[rw] + 1 <= io_allowed) {
556                 if (wait)
557                         *wait = 0;
558                 return 1;
559         }
560 
561         /* Calc approx time to dispatch */
562         jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
563 
564         if (jiffy_wait > jiffy_elapsed)
565                 jiffy_wait = jiffy_wait - jiffy_elapsed;
566         else
567                 jiffy_wait = 1;
568 
569         if (wait)
570                 *wait = jiffy_wait;
571         return 0;
572 }
573 
574 static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
575                 struct bio *bio, unsigned long *wait)
576 {
577         bool rw = bio_data_dir(bio);
578         u64 bytes_allowed, extra_bytes, tmp;
579         unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
580 
581         jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
582 
583         /* Slice has just started. Consider one slice interval */
584         if (!jiffy_elapsed)
585                 jiffy_elapsed_rnd = throtl_slice;
586 
587         jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
588 
589         tmp = tg->bps[rw] * jiffy_elapsed_rnd;
590         do_div(tmp, HZ);
591         bytes_allowed = tmp;
592 
593         if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
594                 if (wait)
595                         *wait = 0;
596                 return 1;
597         }
598 
599         /* Calc approx time to dispatch */
600         extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
601         jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
602 
603         if (!jiffy_wait)
604                 jiffy_wait = 1;
605 
606         /*
607          * This wait time is without taking into consideration the rounding
608          * up we did. Add that time also.
609          */
610         jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
611         if (wait)
612                 *wait = jiffy_wait;
613         return 0;
614 }
615 
616 static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
617         if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
618                 return 1;
619         return 0;
620 }
621 
622 /*
623  * Returns whether one can dispatch a bio or not. Also returns approx number
624  * of jiffies to wait before this bio is with-in IO rate and can be dispatched
625  */
626 static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
627                                 struct bio *bio, unsigned long *wait)
628 {
629         bool rw = bio_data_dir(bio);
630         unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
631 
632         /*
633          * Currently whole state machine of group depends on first bio
634          * queued in the group bio list. So one should not be calling
635          * this function with a different bio if there are other bios
636          * queued.
637          */
638         BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
639 
640         /* If tg->bps = -1, then BW is unlimited */
641         if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
642                 if (wait)
643                         *wait = 0;
644                 return 1;
645         }
646 
647         /*
648          * If previous slice expired, start a new one otherwise renew/extend
649          * existing slice to make sure it is at least throtl_slice interval
650          * long since now.
651          */
652         if (throtl_slice_used(td, tg, rw))
653                 throtl_start_new_slice(td, tg, rw);
654         else {
655                 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
656                         throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
657         }
658 
659         if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
660             && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
661                 if (wait)
662                         *wait = 0;
663                 return 1;
664         }
665 
666         max_wait = max(bps_wait, iops_wait);
667 
668         if (wait)
669                 *wait = max_wait;
670 
671         if (time_before(tg->slice_end[rw], jiffies + max_wait))
672                 throtl_extend_slice(td, tg, rw, jiffies + max_wait);
673 
674         return 0;
675 }
676 
677 static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
678                                          int rw)
679 {
680         struct throtl_grp *tg = blkg_to_tg(blkg);
681         struct tg_stats_cpu *stats_cpu;
682         unsigned long flags;
683 
684         /* If per cpu stats are not allocated yet, don't do any accounting. */
685         if (tg->stats_cpu == NULL)
686                 return;
687 
688         /*
689          * Disabling interrupts to provide mutual exclusion between two
690          * writes on same cpu. It probably is not needed for 64bit. Not
691          * optimizing that case yet.
692          */
693         local_irq_save(flags);
694 
695         stats_cpu = this_cpu_ptr(tg->stats_cpu);
696 
697         blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
698         blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
699 
700         local_irq_restore(flags);
701 }
702 
703 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
704 {
705         bool rw = bio_data_dir(bio);
706 
707         /* Charge the bio to the group */
708         tg->bytes_disp[rw] += bio->bi_size;
709         tg->io_disp[rw]++;
710 
711         throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw);
712 }
713 
714 static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
715                         struct bio *bio)
716 {
717         bool rw = bio_data_dir(bio);
718 
719         bio_list_add(&tg->bio_lists[rw], bio);
720         /* Take a bio reference on tg */
721         blkg_get(tg_to_blkg(tg));
722         tg->nr_queued[rw]++;
723         td->nr_queued[rw]++;
724         throtl_enqueue_tg(td, tg);
725 }
726 
727 static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
728 {
729         unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
730         struct bio *bio;
731 
732         if ((bio = bio_list_peek(&tg->bio_lists[READ])))
733                 tg_may_dispatch(td, tg, bio, &read_wait);
734 
735         if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
736                 tg_may_dispatch(td, tg, bio, &write_wait);
737 
738         min_wait = min(read_wait, write_wait);
739         disptime = jiffies + min_wait;
740 
741         /* Update dispatch time */
742         throtl_dequeue_tg(td, tg);
743         tg->disptime = disptime;
744         throtl_enqueue_tg(td, tg);
745 }
746 
747 static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
748                                 bool rw, struct bio_list *bl)
749 {
750         struct bio *bio;
751 
752         bio = bio_list_pop(&tg->bio_lists[rw]);
753         tg->nr_queued[rw]--;
754         /* Drop bio reference on blkg */
755         blkg_put(tg_to_blkg(tg));
756 
757         BUG_ON(td->nr_queued[rw] <= 0);
758         td->nr_queued[rw]--;
759 
760         throtl_charge_bio(tg, bio);
761         bio_list_add(bl, bio);
762         bio->bi_rw |= REQ_THROTTLED;
763 
764         throtl_trim_slice(td, tg, rw);
765 }
766 
767 static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
768                                 struct bio_list *bl)
769 {
770         unsigned int nr_reads = 0, nr_writes = 0;
771         unsigned int max_nr_reads = throtl_grp_quantum*3/4;
772         unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
773         struct bio *bio;
774 
775         /* Try to dispatch 75% READS and 25% WRITES */
776 
777         while ((bio = bio_list_peek(&tg->bio_lists[READ]))
778                 && tg_may_dispatch(td, tg, bio, NULL)) {
779 
780                 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
781                 nr_reads++;
782 
783                 if (nr_reads >= max_nr_reads)
784                         break;
785         }
786 
787         while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
788                 && tg_may_dispatch(td, tg, bio, NULL)) {
789 
790                 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
791                 nr_writes++;
792 
793                 if (nr_writes >= max_nr_writes)
794                         break;
795         }
796 
797         return nr_reads + nr_writes;
798 }
799 
800 static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
801 {
802         unsigned int nr_disp = 0;
803         struct throtl_grp *tg;
804         struct throtl_rb_root *st = &td->tg_service_tree;
805 
806         while (1) {
807                 tg = throtl_rb_first(st);
808 
809                 if (!tg)
810                         break;
811 
812                 if (time_before(jiffies, tg->disptime))
813                         break;
814 
815                 throtl_dequeue_tg(td, tg);
816 
817                 nr_disp += throtl_dispatch_tg(td, tg, bl);
818 
819                 if (tg->nr_queued[0] || tg->nr_queued[1]) {
820                         tg_update_disptime(td, tg);
821                         throtl_enqueue_tg(td, tg);
822                 }
823 
824                 if (nr_disp >= throtl_quantum)
825                         break;
826         }
827 
828         return nr_disp;
829 }
830 
831 static void throtl_process_limit_change(struct throtl_data *td)
832 {
833         struct request_queue *q = td->queue;
834         struct blkcg_gq *blkg, *n;
835 
836         if (!td->limits_changed)
837                 return;
838 
839         xchg(&td->limits_changed, false);
840 
841         throtl_log(td, "limits changed");
842 
843         list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
844                 struct throtl_grp *tg = blkg_to_tg(blkg);
845 
846                 if (!tg->limits_changed)
847                         continue;
848 
849                 if (!xchg(&tg->limits_changed, false))
850                         continue;
851 
852                 throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
853                         " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
854                         tg->iops[READ], tg->iops[WRITE]);
855 
856                 /*
857                  * Restart the slices for both READ and WRITES. It
858                  * might happen that a group's limit are dropped
859                  * suddenly and we don't want to account recently
860                  * dispatched IO with new low rate
861                  */
862                 throtl_start_new_slice(td, tg, 0);
863                 throtl_start_new_slice(td, tg, 1);
864 
865                 if (throtl_tg_on_rr(tg))
866                         tg_update_disptime(td, tg);
867         }
868 }
869 
870 /* Dispatch throttled bios. Should be called without queue lock held. */
871 static int throtl_dispatch(struct request_queue *q)
872 {
873         struct throtl_data *td = q->td;
874         unsigned int nr_disp = 0;
875         struct bio_list bio_list_on_stack;
876         struct bio *bio;
877         struct blk_plug plug;
878 
879         spin_lock_irq(q->queue_lock);
880 
881         throtl_process_limit_change(td);
882 
883         if (!total_nr_queued(td))
884                 goto out;
885 
886         bio_list_init(&bio_list_on_stack);
887 
888         throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
889                         total_nr_queued(td), td->nr_queued[READ],
890                         td->nr_queued[WRITE]);
891 
892         nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
893 
894         if (nr_disp)
895                 throtl_log(td, "bios disp=%u", nr_disp);
896 
897         throtl_schedule_next_dispatch(td);
898 out:
899         spin_unlock_irq(q->queue_lock);
900 
901         /*
902          * If we dispatched some requests, unplug the queue to make sure
903          * immediate dispatch
904          */
905         if (nr_disp) {
906                 blk_start_plug(&plug);
907                 while((bio = bio_list_pop(&bio_list_on_stack)))
908                         generic_make_request(bio);
909                 blk_finish_plug(&plug);
910         }
911         return nr_disp;
912 }
913 
914 void blk_throtl_work(struct work_struct *work)
915 {
916         struct throtl_data *td = container_of(work, struct throtl_data,
917                                         throtl_work.work);
918         struct request_queue *q = td->queue;
919 
920         throtl_dispatch(q);
921 }
922 
923 /* Call with queue lock held */
924 static void
925 throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
926 {
927 
928         struct delayed_work *dwork = &td->throtl_work;
929 
930         /* schedule work if limits changed even if no bio is queued */
931         if (total_nr_queued(td) || td->limits_changed) {
932                 mod_delayed_work(kthrotld_workqueue, dwork, delay);
933                 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
934                                 delay, jiffies);
935         }
936 }
937 
938 static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
939                                 struct blkg_policy_data *pd, int off)
940 {
941         struct throtl_grp *tg = pd_to_tg(pd);
942         struct blkg_rwstat rwstat = { }, tmp;
943         int i, cpu;
944 
945         if (tg->stats_cpu == NULL)
946                 return 0;
947 
948         for_each_possible_cpu(cpu) {
949                 struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
950 
951                 tmp = blkg_rwstat_read((void *)sc + off);
952                 for (i = 0; i < BLKG_RWSTAT_NR; i++)
953                         rwstat.cnt[i] += tmp.cnt[i];
954         }
955 
956         return __blkg_prfill_rwstat(sf, pd, &rwstat);
957 }
958 
959 static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
960                                struct seq_file *sf)
961 {
962         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
963 
964         blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl,
965                           cft->private, true);
966         return 0;
967 }
968 
969 static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
970                               int off)
971 {
972         struct throtl_grp *tg = pd_to_tg(pd);
973         u64 v = *(u64 *)((void *)tg + off);
974 
975         if (v == -1)
976                 return 0;
977         return __blkg_prfill_u64(sf, pd, v);
978 }
979 
980 static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
981                                int off)
982 {
983         struct throtl_grp *tg = pd_to_tg(pd);
984         unsigned int v = *(unsigned int *)((void *)tg + off);
985 
986         if (v == -1)
987                 return 0;
988         return __blkg_prfill_u64(sf, pd, v);
989 }
990 
991 static int tg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft,
992                              struct seq_file *sf)
993 {
994         blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_u64,
995                           &blkcg_policy_throtl, cft->private, false);
996         return 0;
997 }
998 
999 static int tg_print_conf_uint(struct cgroup *cgrp, struct cftype *cft,
1000                               struct seq_file *sf)
1001 {
1002         blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_uint,
1003                           &blkcg_policy_throtl, cft->private, false);
1004         return 0;
1005 }
1006 
1007 static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf,
1008                        bool is_u64)
1009 {
1010         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1011         struct blkg_conf_ctx ctx;
1012         struct throtl_grp *tg;
1013         struct throtl_data *td;
1014         int ret;
1015 
1016         ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1017         if (ret)
1018                 return ret;
1019 
1020         tg = blkg_to_tg(ctx.blkg);
1021         td = ctx.blkg->q->td;
1022 
1023         if (!ctx.v)
1024                 ctx.v = -1;
1025 
1026         if (is_u64)
1027                 *(u64 *)((void *)tg + cft->private) = ctx.v;
1028         else
1029                 *(unsigned int *)((void *)tg + cft->private) = ctx.v;
1030 
1031         /* XXX: we don't need the following deferred processing */
1032         xchg(&tg->limits_changed, true);
1033         xchg(&td->limits_changed, true);
1034         throtl_schedule_delayed_work(td, 0);
1035 
1036         blkg_conf_finish(&ctx);
1037         return 0;
1038 }
1039 
1040 static int tg_set_conf_u64(struct cgroup *cgrp, struct cftype *cft,
1041                            const char *buf)
1042 {
1043         return tg_set_conf(cgrp, cft, buf, true);
1044 }
1045 
1046 static int tg_set_conf_uint(struct cgroup *cgrp, struct cftype *cft,
1047                             const char *buf)
1048 {
1049         return tg_set_conf(cgrp, cft, buf, false);
1050 }
1051 
1052 static struct cftype throtl_files[] = {
1053         {
1054                 .name = "throttle.read_bps_device",
1055                 .private = offsetof(struct throtl_grp, bps[READ]),
1056                 .read_seq_string = tg_print_conf_u64,
1057                 .write_string = tg_set_conf_u64,
1058                 .max_write_len = 256,
1059         },
1060         {
1061                 .name = "throttle.write_bps_device",
1062                 .private = offsetof(struct throtl_grp, bps[WRITE]),
1063                 .read_seq_string = tg_print_conf_u64,
1064                 .write_string = tg_set_conf_u64,
1065                 .max_write_len = 256,
1066         },
1067         {
1068                 .name = "throttle.read_iops_device",
1069                 .private = offsetof(struct throtl_grp, iops[READ]),
1070                 .read_seq_string = tg_print_conf_uint,
1071                 .write_string = tg_set_conf_uint,
1072                 .max_write_len = 256,
1073         },
1074         {
1075                 .name = "throttle.write_iops_device",
1076                 .private = offsetof(struct throtl_grp, iops[WRITE]),
1077                 .read_seq_string = tg_print_conf_uint,
1078                 .write_string = tg_set_conf_uint,
1079                 .max_write_len = 256,
1080         },
1081         {
1082                 .name = "throttle.io_service_bytes",
1083                 .private = offsetof(struct tg_stats_cpu, service_bytes),
1084                 .read_seq_string = tg_print_cpu_rwstat,
1085         },
1086         {
1087                 .name = "throttle.io_serviced",
1088                 .private = offsetof(struct tg_stats_cpu, serviced),
1089                 .read_seq_string = tg_print_cpu_rwstat,
1090         },
1091         { }     /* terminate */
1092 };
1093 
1094 static void throtl_shutdown_wq(struct request_queue *q)
1095 {
1096         struct throtl_data *td = q->td;
1097 
1098         cancel_delayed_work_sync(&td->throtl_work);
1099 }
1100 
1101 static struct blkcg_policy blkcg_policy_throtl = {
1102         .pd_size                = sizeof(struct throtl_grp),
1103         .cftypes                = throtl_files,
1104 
1105         .pd_init_fn             = throtl_pd_init,
1106         .pd_exit_fn             = throtl_pd_exit,
1107         .pd_reset_stats_fn      = throtl_pd_reset_stats,
1108 };
1109 
1110 bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
1111 {
1112         struct throtl_data *td = q->td;
1113         struct throtl_grp *tg;
1114         bool rw = bio_data_dir(bio), update_disptime = true;
1115         struct blkcg *blkcg;
1116         bool throttled = false;
1117 
1118         if (bio->bi_rw & REQ_THROTTLED) {
1119                 bio->bi_rw &= ~REQ_THROTTLED;
1120                 goto out;
1121         }
1122 
1123         /*
1124          * A throtl_grp pointer retrieved under rcu can be used to access
1125          * basic fields like stats and io rates. If a group has no rules,
1126          * just update the dispatch stats in lockless manner and return.
1127          */
1128         rcu_read_lock();
1129         blkcg = bio_blkcg(bio);
1130         tg = throtl_lookup_tg(td, blkcg);
1131         if (tg) {
1132                 if (tg_no_rule_group(tg, rw)) {
1133                         throtl_update_dispatch_stats(tg_to_blkg(tg),
1134                                                      bio->bi_size, bio->bi_rw);
1135                         goto out_unlock_rcu;
1136                 }
1137         }
1138 
1139         /*
1140          * Either group has not been allocated yet or it is not an unlimited
1141          * IO group
1142          */
1143         spin_lock_irq(q->queue_lock);
1144         tg = throtl_lookup_create_tg(td, blkcg);
1145         if (unlikely(!tg))
1146                 goto out_unlock;
1147 
1148         if (tg->nr_queued[rw]) {
1149                 /*
1150                  * There is already another bio queued in same dir. No
1151                  * need to update dispatch time.
1152                  */
1153                 update_disptime = false;
1154                 goto queue_bio;
1155 
1156         }
1157 
1158         /* Bio is with-in rate limit of group */
1159         if (tg_may_dispatch(td, tg, bio, NULL)) {
1160                 throtl_charge_bio(tg, bio);
1161 
1162                 /*
1163                  * We need to trim slice even when bios are not being queued
1164                  * otherwise it might happen that a bio is not queued for
1165                  * a long time and slice keeps on extending and trim is not
1166                  * called for a long time. Now if limits are reduced suddenly
1167                  * we take into account all the IO dispatched so far at new
1168                  * low rate and * newly queued IO gets a really long dispatch
1169                  * time.
1170                  *
1171                  * So keep on trimming slice even if bio is not queued.
1172                  */
1173                 throtl_trim_slice(td, tg, rw);
1174                 goto out_unlock;
1175         }
1176 
1177 queue_bio:
1178         throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
1179                         " iodisp=%u iops=%u queued=%d/%d",
1180                         rw == READ ? 'R' : 'W',
1181                         tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
1182                         tg->io_disp[rw], tg->iops[rw],
1183                         tg->nr_queued[READ], tg->nr_queued[WRITE]);
1184 
1185         bio_associate_current(bio);
1186         throtl_add_bio_tg(q->td, tg, bio);
1187         throttled = true;
1188 
1189         if (update_disptime) {
1190                 tg_update_disptime(td, tg);
1191                 throtl_schedule_next_dispatch(td);
1192         }
1193 
1194 out_unlock:
1195         spin_unlock_irq(q->queue_lock);
1196 out_unlock_rcu:
1197         rcu_read_unlock();
1198 out:
1199         return throttled;
1200 }
1201 
1202 /**
1203  * blk_throtl_drain - drain throttled bios
1204  * @q: request_queue to drain throttled bios for
1205  *
1206  * Dispatch all currently throttled bios on @q through ->make_request_fn().
1207  */
1208 void blk_throtl_drain(struct request_queue *q)
1209         __releases(q->queue_lock) __acquires(q->queue_lock)
1210 {
1211         struct throtl_data *td = q->td;
1212         struct throtl_rb_root *st = &td->tg_service_tree;
1213         struct throtl_grp *tg;
1214         struct bio_list bl;
1215         struct bio *bio;
1216 
1217         queue_lockdep_assert_held(q);
1218 
1219         bio_list_init(&bl);
1220 
1221         while ((tg = throtl_rb_first(st))) {
1222                 throtl_dequeue_tg(td, tg);
1223 
1224                 while ((bio = bio_list_peek(&tg->bio_lists[READ])))
1225                         tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1226                 while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
1227                         tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1228         }
1229         spin_unlock_irq(q->queue_lock);
1230 
1231         while ((bio = bio_list_pop(&bl)))
1232                 generic_make_request(bio);
1233 
1234         spin_lock_irq(q->queue_lock);
1235 }
1236 
1237 int blk_throtl_init(struct request_queue *q)
1238 {
1239         struct throtl_data *td;
1240         int ret;
1241 
1242         td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1243         if (!td)
1244                 return -ENOMEM;
1245 
1246         td->tg_service_tree = THROTL_RB_ROOT;
1247         td->limits_changed = false;
1248         INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1249 
1250         q->td = td;
1251         td->queue = q;
1252 
1253         /* activate policy */
1254         ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1255         if (ret)
1256                 kfree(td);
1257         return ret;
1258 }
1259 
1260 void blk_throtl_exit(struct request_queue *q)
1261 {
1262         BUG_ON(!q->td);
1263         throtl_shutdown_wq(q);
1264         blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1265         kfree(q->td);
1266 }
1267 
1268 static int __init throtl_init(void)
1269 {
1270         kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1271         if (!kthrotld_workqueue)
1272                 panic("Failed to create kthrotld\n");
1273 
1274         return blkcg_policy_register(&blkcg_policy_throtl);
1275 }
1276 
1277 module_init(throtl_init);
1278 

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