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

Version: ~ [ linux-5.5-rc1 ] ~ [ linux-5.4.2 ] ~ [ linux-5.3.15 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.88 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.158 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.206 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.206 ] ~ [ 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-3.16.78 ] ~ [ 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-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ 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 <linux/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 
 29 /*
 30  * To implement hierarchical throttling, throtl_grps form a tree and bios
 31  * are dispatched upwards level by level until they reach the top and get
 32  * issued.  When dispatching bios from the children and local group at each
 33  * level, if the bios are dispatched into a single bio_list, there's a risk
 34  * of a local or child group which can queue many bios at once filling up
 35  * the list starving others.
 36  *
 37  * To avoid such starvation, dispatched bios are queued separately
 38  * according to where they came from.  When they are again dispatched to
 39  * the parent, they're popped in round-robin order so that no single source
 40  * hogs the dispatch window.
 41  *
 42  * throtl_qnode is used to keep the queued bios separated by their sources.
 43  * Bios are queued to throtl_qnode which in turn is queued to
 44  * throtl_service_queue and then dispatched in round-robin order.
 45  *
 46  * It's also used to track the reference counts on blkg's.  A qnode always
 47  * belongs to a throtl_grp and gets queued on itself or the parent, so
 48  * incrementing the reference of the associated throtl_grp when a qnode is
 49  * queued and decrementing when dequeued is enough to keep the whole blkg
 50  * tree pinned while bios are in flight.
 51  */
 52 struct throtl_qnode {
 53         struct list_head        node;           /* service_queue->queued[] */
 54         struct bio_list         bios;           /* queued bios */
 55         struct throtl_grp       *tg;            /* tg this qnode belongs to */
 56 };
 57 
 58 struct throtl_service_queue {
 59         struct throtl_service_queue *parent_sq; /* the parent service_queue */
 60 
 61         /*
 62          * Bios queued directly to this service_queue or dispatched from
 63          * children throtl_grp's.
 64          */
 65         struct list_head        queued[2];      /* throtl_qnode [READ/WRITE] */
 66         unsigned int            nr_queued[2];   /* number of queued bios */
 67 
 68         /*
 69          * RB tree of active children throtl_grp's, which are sorted by
 70          * their ->disptime.
 71          */
 72         struct rb_root          pending_tree;   /* RB tree of active tgs */
 73         struct rb_node          *first_pending; /* first node in the tree */
 74         unsigned int            nr_pending;     /* # queued in the tree */
 75         unsigned long           first_pending_disptime; /* disptime of the first tg */
 76         struct timer_list       pending_timer;  /* fires on first_pending_disptime */
 77 };
 78 
 79 enum tg_state_flags {
 80         THROTL_TG_PENDING       = 1 << 0,       /* on parent's pending tree */
 81         THROTL_TG_WAS_EMPTY     = 1 << 1,       /* bio_lists[] became non-empty */
 82 };
 83 
 84 #define rb_entry_tg(node)       rb_entry((node), struct throtl_grp, rb_node)
 85 
 86 struct throtl_grp {
 87         /* must be the first member */
 88         struct blkg_policy_data pd;
 89 
 90         /* active throtl group service_queue member */
 91         struct rb_node rb_node;
 92 
 93         /* throtl_data this group belongs to */
 94         struct throtl_data *td;
 95 
 96         /* this group's service queue */
 97         struct throtl_service_queue service_queue;
 98 
 99         /*
100          * qnode_on_self is used when bios are directly queued to this
101          * throtl_grp so that local bios compete fairly with bios
102          * dispatched from children.  qnode_on_parent is used when bios are
103          * dispatched from this throtl_grp into its parent and will compete
104          * with the sibling qnode_on_parents and the parent's
105          * qnode_on_self.
106          */
107         struct throtl_qnode qnode_on_self[2];
108         struct throtl_qnode qnode_on_parent[2];
109 
110         /*
111          * Dispatch time in jiffies. This is the estimated time when group
112          * will unthrottle and is ready to dispatch more bio. It is used as
113          * key to sort active groups in service tree.
114          */
115         unsigned long disptime;
116 
117         unsigned int flags;
118 
119         /* are there any throtl rules between this group and td? */
120         bool has_rules[2];
121 
122         /* bytes per second rate limits */
123         uint64_t bps[2];
124 
125         /* IOPS limits */
126         unsigned int iops[2];
127 
128         /* Number of bytes disptached in current slice */
129         uint64_t bytes_disp[2];
130         /* Number of bio's dispatched in current slice */
131         unsigned int io_disp[2];
132 
133         /* When did we start a new slice */
134         unsigned long slice_start[2];
135         unsigned long slice_end[2];
136 };
137 
138 struct throtl_data
139 {
140         /* service tree for active throtl groups */
141         struct throtl_service_queue service_queue;
142 
143         struct request_queue *queue;
144 
145         /* Total Number of queued bios on READ and WRITE lists */
146         unsigned int nr_queued[2];
147 
148         /*
149          * number of total undestroyed groups
150          */
151         unsigned int nr_undestroyed_grps;
152 
153         /* Work for dispatching throttled bios */
154         struct work_struct dispatch_work;
155 };
156 
157 static void throtl_pending_timer_fn(unsigned long arg);
158 
159 static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
160 {
161         return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
162 }
163 
164 static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
165 {
166         return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
167 }
168 
169 static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
170 {
171         return pd_to_blkg(&tg->pd);
172 }
173 
174 /**
175  * sq_to_tg - return the throl_grp the specified service queue belongs to
176  * @sq: the throtl_service_queue of interest
177  *
178  * Return the throtl_grp @sq belongs to.  If @sq is the top-level one
179  * embedded in throtl_data, %NULL is returned.
180  */
181 static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
182 {
183         if (sq && sq->parent_sq)
184                 return container_of(sq, struct throtl_grp, service_queue);
185         else
186                 return NULL;
187 }
188 
189 /**
190  * sq_to_td - return throtl_data the specified service queue belongs to
191  * @sq: the throtl_service_queue of interest
192  *
193  * A service_queue can be embeded in either a throtl_grp or throtl_data.
194  * Determine the associated throtl_data accordingly and return it.
195  */
196 static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
197 {
198         struct throtl_grp *tg = sq_to_tg(sq);
199 
200         if (tg)
201                 return tg->td;
202         else
203                 return container_of(sq, struct throtl_data, service_queue);
204 }
205 
206 /**
207  * throtl_log - log debug message via blktrace
208  * @sq: the service_queue being reported
209  * @fmt: printf format string
210  * @args: printf args
211  *
212  * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
213  * throtl_grp; otherwise, just "throtl".
214  */
215 #define throtl_log(sq, fmt, args...)    do {                            \
216         struct throtl_grp *__tg = sq_to_tg((sq));                       \
217         struct throtl_data *__td = sq_to_td((sq));                      \
218                                                                         \
219         (void)__td;                                                     \
220         if (likely(!blk_trace_note_message_enabled(__td->queue)))       \
221                 break;                                                  \
222         if ((__tg)) {                                                   \
223                 char __pbuf[128];                                       \
224                                                                         \
225                 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf));    \
226                 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
227         } else {                                                        \
228                 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args);  \
229         }                                                               \
230 } while (0)
231 
232 static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
233 {
234         INIT_LIST_HEAD(&qn->node);
235         bio_list_init(&qn->bios);
236         qn->tg = tg;
237 }
238 
239 /**
240  * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
241  * @bio: bio being added
242  * @qn: qnode to add bio to
243  * @queued: the service_queue->queued[] list @qn belongs to
244  *
245  * Add @bio to @qn and put @qn on @queued if it's not already on.
246  * @qn->tg's reference count is bumped when @qn is activated.  See the
247  * comment on top of throtl_qnode definition for details.
248  */
249 static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
250                                  struct list_head *queued)
251 {
252         bio_list_add(&qn->bios, bio);
253         if (list_empty(&qn->node)) {
254                 list_add_tail(&qn->node, queued);
255                 blkg_get(tg_to_blkg(qn->tg));
256         }
257 }
258 
259 /**
260  * throtl_peek_queued - peek the first bio on a qnode list
261  * @queued: the qnode list to peek
262  */
263 static struct bio *throtl_peek_queued(struct list_head *queued)
264 {
265         struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
266         struct bio *bio;
267 
268         if (list_empty(queued))
269                 return NULL;
270 
271         bio = bio_list_peek(&qn->bios);
272         WARN_ON_ONCE(!bio);
273         return bio;
274 }
275 
276 /**
277  * throtl_pop_queued - pop the first bio form a qnode list
278  * @queued: the qnode list to pop a bio from
279  * @tg_to_put: optional out argument for throtl_grp to put
280  *
281  * Pop the first bio from the qnode list @queued.  After popping, the first
282  * qnode is removed from @queued if empty or moved to the end of @queued so
283  * that the popping order is round-robin.
284  *
285  * When the first qnode is removed, its associated throtl_grp should be put
286  * too.  If @tg_to_put is NULL, this function automatically puts it;
287  * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
288  * responsible for putting it.
289  */
290 static struct bio *throtl_pop_queued(struct list_head *queued,
291                                      struct throtl_grp **tg_to_put)
292 {
293         struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
294         struct bio *bio;
295 
296         if (list_empty(queued))
297                 return NULL;
298 
299         bio = bio_list_pop(&qn->bios);
300         WARN_ON_ONCE(!bio);
301 
302         if (bio_list_empty(&qn->bios)) {
303                 list_del_init(&qn->node);
304                 if (tg_to_put)
305                         *tg_to_put = qn->tg;
306                 else
307                         blkg_put(tg_to_blkg(qn->tg));
308         } else {
309                 list_move_tail(&qn->node, queued);
310         }
311 
312         return bio;
313 }
314 
315 /* init a service_queue, assumes the caller zeroed it */
316 static void throtl_service_queue_init(struct throtl_service_queue *sq)
317 {
318         INIT_LIST_HEAD(&sq->queued[0]);
319         INIT_LIST_HEAD(&sq->queued[1]);
320         sq->pending_tree = RB_ROOT;
321         setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
322                     (unsigned long)sq);
323 }
324 
325 static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
326 {
327         struct throtl_grp *tg;
328         int rw;
329 
330         tg = kzalloc_node(sizeof(*tg), gfp, node);
331         if (!tg)
332                 return NULL;
333 
334         throtl_service_queue_init(&tg->service_queue);
335 
336         for (rw = READ; rw <= WRITE; rw++) {
337                 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
338                 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
339         }
340 
341         RB_CLEAR_NODE(&tg->rb_node);
342         tg->bps[READ] = -1;
343         tg->bps[WRITE] = -1;
344         tg->iops[READ] = -1;
345         tg->iops[WRITE] = -1;
346 
347         return &tg->pd;
348 }
349 
350 static void throtl_pd_init(struct blkg_policy_data *pd)
351 {
352         struct throtl_grp *tg = pd_to_tg(pd);
353         struct blkcg_gq *blkg = tg_to_blkg(tg);
354         struct throtl_data *td = blkg->q->td;
355         struct throtl_service_queue *sq = &tg->service_queue;
356 
357         /*
358          * If on the default hierarchy, we switch to properly hierarchical
359          * behavior where limits on a given throtl_grp are applied to the
360          * whole subtree rather than just the group itself.  e.g. If 16M
361          * read_bps limit is set on the root group, the whole system can't
362          * exceed 16M for the device.
363          *
364          * If not on the default hierarchy, the broken flat hierarchy
365          * behavior is retained where all throtl_grps are treated as if
366          * they're all separate root groups right below throtl_data.
367          * Limits of a group don't interact with limits of other groups
368          * regardless of the position of the group in the hierarchy.
369          */
370         sq->parent_sq = &td->service_queue;
371         if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
372                 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
373         tg->td = td;
374 }
375 
376 /*
377  * Set has_rules[] if @tg or any of its parents have limits configured.
378  * This doesn't require walking up to the top of the hierarchy as the
379  * parent's has_rules[] is guaranteed to be correct.
380  */
381 static void tg_update_has_rules(struct throtl_grp *tg)
382 {
383         struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
384         int rw;
385 
386         for (rw = READ; rw <= WRITE; rw++)
387                 tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
388                                     (tg->bps[rw] != -1 || tg->iops[rw] != -1);
389 }
390 
391 static void throtl_pd_online(struct blkg_policy_data *pd)
392 {
393         /*
394          * We don't want new groups to escape the limits of its ancestors.
395          * Update has_rules[] after a new group is brought online.
396          */
397         tg_update_has_rules(pd_to_tg(pd));
398 }
399 
400 static void throtl_pd_free(struct blkg_policy_data *pd)
401 {
402         struct throtl_grp *tg = pd_to_tg(pd);
403 
404         del_timer_sync(&tg->service_queue.pending_timer);
405         kfree(tg);
406 }
407 
408 static struct throtl_grp *
409 throtl_rb_first(struct throtl_service_queue *parent_sq)
410 {
411         /* Service tree is empty */
412         if (!parent_sq->nr_pending)
413                 return NULL;
414 
415         if (!parent_sq->first_pending)
416                 parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
417 
418         if (parent_sq->first_pending)
419                 return rb_entry_tg(parent_sq->first_pending);
420 
421         return NULL;
422 }
423 
424 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
425 {
426         rb_erase(n, root);
427         RB_CLEAR_NODE(n);
428 }
429 
430 static void throtl_rb_erase(struct rb_node *n,
431                             struct throtl_service_queue *parent_sq)
432 {
433         if (parent_sq->first_pending == n)
434                 parent_sq->first_pending = NULL;
435         rb_erase_init(n, &parent_sq->pending_tree);
436         --parent_sq->nr_pending;
437 }
438 
439 static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
440 {
441         struct throtl_grp *tg;
442 
443         tg = throtl_rb_first(parent_sq);
444         if (!tg)
445                 return;
446 
447         parent_sq->first_pending_disptime = tg->disptime;
448 }
449 
450 static void tg_service_queue_add(struct throtl_grp *tg)
451 {
452         struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
453         struct rb_node **node = &parent_sq->pending_tree.rb_node;
454         struct rb_node *parent = NULL;
455         struct throtl_grp *__tg;
456         unsigned long key = tg->disptime;
457         int left = 1;
458 
459         while (*node != NULL) {
460                 parent = *node;
461                 __tg = rb_entry_tg(parent);
462 
463                 if (time_before(key, __tg->disptime))
464                         node = &parent->rb_left;
465                 else {
466                         node = &parent->rb_right;
467                         left = 0;
468                 }
469         }
470 
471         if (left)
472                 parent_sq->first_pending = &tg->rb_node;
473 
474         rb_link_node(&tg->rb_node, parent, node);
475         rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
476 }
477 
478 static void __throtl_enqueue_tg(struct throtl_grp *tg)
479 {
480         tg_service_queue_add(tg);
481         tg->flags |= THROTL_TG_PENDING;
482         tg->service_queue.parent_sq->nr_pending++;
483 }
484 
485 static void throtl_enqueue_tg(struct throtl_grp *tg)
486 {
487         if (!(tg->flags & THROTL_TG_PENDING))
488                 __throtl_enqueue_tg(tg);
489 }
490 
491 static void __throtl_dequeue_tg(struct throtl_grp *tg)
492 {
493         throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
494         tg->flags &= ~THROTL_TG_PENDING;
495 }
496 
497 static void throtl_dequeue_tg(struct throtl_grp *tg)
498 {
499         if (tg->flags & THROTL_TG_PENDING)
500                 __throtl_dequeue_tg(tg);
501 }
502 
503 /* Call with queue lock held */
504 static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
505                                           unsigned long expires)
506 {
507         mod_timer(&sq->pending_timer, expires);
508         throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
509                    expires - jiffies, jiffies);
510 }
511 
512 /**
513  * throtl_schedule_next_dispatch - schedule the next dispatch cycle
514  * @sq: the service_queue to schedule dispatch for
515  * @force: force scheduling
516  *
517  * Arm @sq->pending_timer so that the next dispatch cycle starts on the
518  * dispatch time of the first pending child.  Returns %true if either timer
519  * is armed or there's no pending child left.  %false if the current
520  * dispatch window is still open and the caller should continue
521  * dispatching.
522  *
523  * If @force is %true, the dispatch timer is always scheduled and this
524  * function is guaranteed to return %true.  This is to be used when the
525  * caller can't dispatch itself and needs to invoke pending_timer
526  * unconditionally.  Note that forced scheduling is likely to induce short
527  * delay before dispatch starts even if @sq->first_pending_disptime is not
528  * in the future and thus shouldn't be used in hot paths.
529  */
530 static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
531                                           bool force)
532 {
533         /* any pending children left? */
534         if (!sq->nr_pending)
535                 return true;
536 
537         update_min_dispatch_time(sq);
538 
539         /* is the next dispatch time in the future? */
540         if (force || time_after(sq->first_pending_disptime, jiffies)) {
541                 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
542                 return true;
543         }
544 
545         /* tell the caller to continue dispatching */
546         return false;
547 }
548 
549 static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
550                 bool rw, unsigned long start)
551 {
552         tg->bytes_disp[rw] = 0;
553         tg->io_disp[rw] = 0;
554 
555         /*
556          * Previous slice has expired. We must have trimmed it after last
557          * bio dispatch. That means since start of last slice, we never used
558          * that bandwidth. Do try to make use of that bandwidth while giving
559          * credit.
560          */
561         if (time_after_eq(start, tg->slice_start[rw]))
562                 tg->slice_start[rw] = start;
563 
564         tg->slice_end[rw] = jiffies + throtl_slice;
565         throtl_log(&tg->service_queue,
566                    "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
567                    rw == READ ? 'R' : 'W', tg->slice_start[rw],
568                    tg->slice_end[rw], jiffies);
569 }
570 
571 static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
572 {
573         tg->bytes_disp[rw] = 0;
574         tg->io_disp[rw] = 0;
575         tg->slice_start[rw] = jiffies;
576         tg->slice_end[rw] = jiffies + throtl_slice;
577         throtl_log(&tg->service_queue,
578                    "[%c] new slice start=%lu end=%lu jiffies=%lu",
579                    rw == READ ? 'R' : 'W', tg->slice_start[rw],
580                    tg->slice_end[rw], jiffies);
581 }
582 
583 static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
584                                         unsigned long jiffy_end)
585 {
586         tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
587 }
588 
589 static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
590                                        unsigned long jiffy_end)
591 {
592         tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
593         throtl_log(&tg->service_queue,
594                    "[%c] extend slice start=%lu end=%lu jiffies=%lu",
595                    rw == READ ? 'R' : 'W', tg->slice_start[rw],
596                    tg->slice_end[rw], jiffies);
597 }
598 
599 /* Determine if previously allocated or extended slice is complete or not */
600 static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
601 {
602         if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
603                 return false;
604 
605         return 1;
606 }
607 
608 /* Trim the used slices and adjust slice start accordingly */
609 static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
610 {
611         unsigned long nr_slices, time_elapsed, io_trim;
612         u64 bytes_trim, tmp;
613 
614         BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
615 
616         /*
617          * If bps are unlimited (-1), then time slice don't get
618          * renewed. Don't try to trim the slice if slice is used. A new
619          * slice will start when appropriate.
620          */
621         if (throtl_slice_used(tg, rw))
622                 return;
623 
624         /*
625          * A bio has been dispatched. Also adjust slice_end. It might happen
626          * that initially cgroup limit was very low resulting in high
627          * slice_end, but later limit was bumped up and bio was dispached
628          * sooner, then we need to reduce slice_end. A high bogus slice_end
629          * is bad because it does not allow new slice to start.
630          */
631 
632         throtl_set_slice_end(tg, rw, jiffies + throtl_slice);
633 
634         time_elapsed = jiffies - tg->slice_start[rw];
635 
636         nr_slices = time_elapsed / throtl_slice;
637 
638         if (!nr_slices)
639                 return;
640         tmp = tg->bps[rw] * throtl_slice * nr_slices;
641         do_div(tmp, HZ);
642         bytes_trim = tmp;
643 
644         io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
645 
646         if (!bytes_trim && !io_trim)
647                 return;
648 
649         if (tg->bytes_disp[rw] >= bytes_trim)
650                 tg->bytes_disp[rw] -= bytes_trim;
651         else
652                 tg->bytes_disp[rw] = 0;
653 
654         if (tg->io_disp[rw] >= io_trim)
655                 tg->io_disp[rw] -= io_trim;
656         else
657                 tg->io_disp[rw] = 0;
658 
659         tg->slice_start[rw] += nr_slices * throtl_slice;
660 
661         throtl_log(&tg->service_queue,
662                    "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
663                    rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
664                    tg->slice_start[rw], tg->slice_end[rw], jiffies);
665 }
666 
667 static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
668                                   unsigned long *wait)
669 {
670         bool rw = bio_data_dir(bio);
671         unsigned int io_allowed;
672         unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
673         u64 tmp;
674 
675         jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
676 
677         /* Slice has just started. Consider one slice interval */
678         if (!jiffy_elapsed)
679                 jiffy_elapsed_rnd = throtl_slice;
680 
681         jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
682 
683         /*
684          * jiffy_elapsed_rnd should not be a big value as minimum iops can be
685          * 1 then at max jiffy elapsed should be equivalent of 1 second as we
686          * will allow dispatch after 1 second and after that slice should
687          * have been trimmed.
688          */
689 
690         tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
691         do_div(tmp, HZ);
692 
693         if (tmp > UINT_MAX)
694                 io_allowed = UINT_MAX;
695         else
696                 io_allowed = tmp;
697 
698         if (tg->io_disp[rw] + 1 <= io_allowed) {
699                 if (wait)
700                         *wait = 0;
701                 return true;
702         }
703 
704         /* Calc approx time to dispatch */
705         jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
706 
707         if (jiffy_wait > jiffy_elapsed)
708                 jiffy_wait = jiffy_wait - jiffy_elapsed;
709         else
710                 jiffy_wait = 1;
711 
712         if (wait)
713                 *wait = jiffy_wait;
714         return 0;
715 }
716 
717 static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
718                                  unsigned long *wait)
719 {
720         bool rw = bio_data_dir(bio);
721         u64 bytes_allowed, extra_bytes, tmp;
722         unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
723 
724         jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
725 
726         /* Slice has just started. Consider one slice interval */
727         if (!jiffy_elapsed)
728                 jiffy_elapsed_rnd = throtl_slice;
729 
730         jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
731 
732         tmp = tg->bps[rw] * jiffy_elapsed_rnd;
733         do_div(tmp, HZ);
734         bytes_allowed = tmp;
735 
736         if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {
737                 if (wait)
738                         *wait = 0;
739                 return true;
740         }
741 
742         /* Calc approx time to dispatch */
743         extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;
744         jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
745 
746         if (!jiffy_wait)
747                 jiffy_wait = 1;
748 
749         /*
750          * This wait time is without taking into consideration the rounding
751          * up we did. Add that time also.
752          */
753         jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
754         if (wait)
755                 *wait = jiffy_wait;
756         return 0;
757 }
758 
759 /*
760  * Returns whether one can dispatch a bio or not. Also returns approx number
761  * of jiffies to wait before this bio is with-in IO rate and can be dispatched
762  */
763 static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
764                             unsigned long *wait)
765 {
766         bool rw = bio_data_dir(bio);
767         unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
768 
769         /*
770          * Currently whole state machine of group depends on first bio
771          * queued in the group bio list. So one should not be calling
772          * this function with a different bio if there are other bios
773          * queued.
774          */
775         BUG_ON(tg->service_queue.nr_queued[rw] &&
776                bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
777 
778         /* If tg->bps = -1, then BW is unlimited */
779         if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
780                 if (wait)
781                         *wait = 0;
782                 return true;
783         }
784 
785         /*
786          * If previous slice expired, start a new one otherwise renew/extend
787          * existing slice to make sure it is at least throtl_slice interval
788          * long since now.
789          */
790         if (throtl_slice_used(tg, rw))
791                 throtl_start_new_slice(tg, rw);
792         else {
793                 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
794                         throtl_extend_slice(tg, rw, jiffies + throtl_slice);
795         }
796 
797         if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
798             tg_with_in_iops_limit(tg, bio, &iops_wait)) {
799                 if (wait)
800                         *wait = 0;
801                 return 1;
802         }
803 
804         max_wait = max(bps_wait, iops_wait);
805 
806         if (wait)
807                 *wait = max_wait;
808 
809         if (time_before(tg->slice_end[rw], jiffies + max_wait))
810                 throtl_extend_slice(tg, rw, jiffies + max_wait);
811 
812         return 0;
813 }
814 
815 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
816 {
817         bool rw = bio_data_dir(bio);
818 
819         /* Charge the bio to the group */
820         tg->bytes_disp[rw] += bio->bi_iter.bi_size;
821         tg->io_disp[rw]++;
822 
823         /*
824          * REQ_THROTTLED is used to prevent the same bio to be throttled
825          * more than once as a throttled bio will go through blk-throtl the
826          * second time when it eventually gets issued.  Set it when a bio
827          * is being charged to a tg.
828          */
829         if (!(bio->bi_rw & REQ_THROTTLED))
830                 bio->bi_rw |= REQ_THROTTLED;
831 }
832 
833 /**
834  * throtl_add_bio_tg - add a bio to the specified throtl_grp
835  * @bio: bio to add
836  * @qn: qnode to use
837  * @tg: the target throtl_grp
838  *
839  * Add @bio to @tg's service_queue using @qn.  If @qn is not specified,
840  * tg->qnode_on_self[] is used.
841  */
842 static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
843                               struct throtl_grp *tg)
844 {
845         struct throtl_service_queue *sq = &tg->service_queue;
846         bool rw = bio_data_dir(bio);
847 
848         if (!qn)
849                 qn = &tg->qnode_on_self[rw];
850 
851         /*
852          * If @tg doesn't currently have any bios queued in the same
853          * direction, queueing @bio can change when @tg should be
854          * dispatched.  Mark that @tg was empty.  This is automatically
855          * cleaered on the next tg_update_disptime().
856          */
857         if (!sq->nr_queued[rw])
858                 tg->flags |= THROTL_TG_WAS_EMPTY;
859 
860         throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
861 
862         sq->nr_queued[rw]++;
863         throtl_enqueue_tg(tg);
864 }
865 
866 static void tg_update_disptime(struct throtl_grp *tg)
867 {
868         struct throtl_service_queue *sq = &tg->service_queue;
869         unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
870         struct bio *bio;
871 
872         if ((bio = throtl_peek_queued(&sq->queued[READ])))
873                 tg_may_dispatch(tg, bio, &read_wait);
874 
875         if ((bio = throtl_peek_queued(&sq->queued[WRITE])))
876                 tg_may_dispatch(tg, bio, &write_wait);
877 
878         min_wait = min(read_wait, write_wait);
879         disptime = jiffies + min_wait;
880 
881         /* Update dispatch time */
882         throtl_dequeue_tg(tg);
883         tg->disptime = disptime;
884         throtl_enqueue_tg(tg);
885 
886         /* see throtl_add_bio_tg() */
887         tg->flags &= ~THROTL_TG_WAS_EMPTY;
888 }
889 
890 static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
891                                         struct throtl_grp *parent_tg, bool rw)
892 {
893         if (throtl_slice_used(parent_tg, rw)) {
894                 throtl_start_new_slice_with_credit(parent_tg, rw,
895                                 child_tg->slice_start[rw]);
896         }
897 
898 }
899 
900 static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
901 {
902         struct throtl_service_queue *sq = &tg->service_queue;
903         struct throtl_service_queue *parent_sq = sq->parent_sq;
904         struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
905         struct throtl_grp *tg_to_put = NULL;
906         struct bio *bio;
907 
908         /*
909          * @bio is being transferred from @tg to @parent_sq.  Popping a bio
910          * from @tg may put its reference and @parent_sq might end up
911          * getting released prematurely.  Remember the tg to put and put it
912          * after @bio is transferred to @parent_sq.
913          */
914         bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
915         sq->nr_queued[rw]--;
916 
917         throtl_charge_bio(tg, bio);
918 
919         /*
920          * If our parent is another tg, we just need to transfer @bio to
921          * the parent using throtl_add_bio_tg().  If our parent is
922          * @td->service_queue, @bio is ready to be issued.  Put it on its
923          * bio_lists[] and decrease total number queued.  The caller is
924          * responsible for issuing these bios.
925          */
926         if (parent_tg) {
927                 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
928                 start_parent_slice_with_credit(tg, parent_tg, rw);
929         } else {
930                 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
931                                      &parent_sq->queued[rw]);
932                 BUG_ON(tg->td->nr_queued[rw] <= 0);
933                 tg->td->nr_queued[rw]--;
934         }
935 
936         throtl_trim_slice(tg, rw);
937 
938         if (tg_to_put)
939                 blkg_put(tg_to_blkg(tg_to_put));
940 }
941 
942 static int throtl_dispatch_tg(struct throtl_grp *tg)
943 {
944         struct throtl_service_queue *sq = &tg->service_queue;
945         unsigned int nr_reads = 0, nr_writes = 0;
946         unsigned int max_nr_reads = throtl_grp_quantum*3/4;
947         unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
948         struct bio *bio;
949 
950         /* Try to dispatch 75% READS and 25% WRITES */
951 
952         while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
953                tg_may_dispatch(tg, bio, NULL)) {
954 
955                 tg_dispatch_one_bio(tg, bio_data_dir(bio));
956                 nr_reads++;
957 
958                 if (nr_reads >= max_nr_reads)
959                         break;
960         }
961 
962         while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
963                tg_may_dispatch(tg, bio, NULL)) {
964 
965                 tg_dispatch_one_bio(tg, bio_data_dir(bio));
966                 nr_writes++;
967 
968                 if (nr_writes >= max_nr_writes)
969                         break;
970         }
971 
972         return nr_reads + nr_writes;
973 }
974 
975 static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
976 {
977         unsigned int nr_disp = 0;
978 
979         while (1) {
980                 struct throtl_grp *tg = throtl_rb_first(parent_sq);
981                 struct throtl_service_queue *sq = &tg->service_queue;
982 
983                 if (!tg)
984                         break;
985 
986                 if (time_before(jiffies, tg->disptime))
987                         break;
988 
989                 throtl_dequeue_tg(tg);
990 
991                 nr_disp += throtl_dispatch_tg(tg);
992 
993                 if (sq->nr_queued[0] || sq->nr_queued[1])
994                         tg_update_disptime(tg);
995 
996                 if (nr_disp >= throtl_quantum)
997                         break;
998         }
999 
1000         return nr_disp;
1001 }
1002 
1003 /**
1004  * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1005  * @arg: the throtl_service_queue being serviced
1006  *
1007  * This timer is armed when a child throtl_grp with active bio's become
1008  * pending and queued on the service_queue's pending_tree and expires when
1009  * the first child throtl_grp should be dispatched.  This function
1010  * dispatches bio's from the children throtl_grps to the parent
1011  * service_queue.
1012  *
1013  * If the parent's parent is another throtl_grp, dispatching is propagated
1014  * by either arming its pending_timer or repeating dispatch directly.  If
1015  * the top-level service_tree is reached, throtl_data->dispatch_work is
1016  * kicked so that the ready bio's are issued.
1017  */
1018 static void throtl_pending_timer_fn(unsigned long arg)
1019 {
1020         struct throtl_service_queue *sq = (void *)arg;
1021         struct throtl_grp *tg = sq_to_tg(sq);
1022         struct throtl_data *td = sq_to_td(sq);
1023         struct request_queue *q = td->queue;
1024         struct throtl_service_queue *parent_sq;
1025         bool dispatched;
1026         int ret;
1027 
1028         spin_lock_irq(q->queue_lock);
1029 again:
1030         parent_sq = sq->parent_sq;
1031         dispatched = false;
1032 
1033         while (true) {
1034                 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1035                            sq->nr_queued[READ] + sq->nr_queued[WRITE],
1036                            sq->nr_queued[READ], sq->nr_queued[WRITE]);
1037 
1038                 ret = throtl_select_dispatch(sq);
1039                 if (ret) {
1040                         throtl_log(sq, "bios disp=%u", ret);
1041                         dispatched = true;
1042                 }
1043 
1044                 if (throtl_schedule_next_dispatch(sq, false))
1045                         break;
1046 
1047                 /* this dispatch windows is still open, relax and repeat */
1048                 spin_unlock_irq(q->queue_lock);
1049                 cpu_relax();
1050                 spin_lock_irq(q->queue_lock);
1051         }
1052 
1053         if (!dispatched)
1054                 goto out_unlock;
1055 
1056         if (parent_sq) {
1057                 /* @parent_sq is another throl_grp, propagate dispatch */
1058                 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1059                         tg_update_disptime(tg);
1060                         if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1061                                 /* window is already open, repeat dispatching */
1062                                 sq = parent_sq;
1063                                 tg = sq_to_tg(sq);
1064                                 goto again;
1065                         }
1066                 }
1067         } else {
1068                 /* reached the top-level, queue issueing */
1069                 queue_work(kthrotld_workqueue, &td->dispatch_work);
1070         }
1071 out_unlock:
1072         spin_unlock_irq(q->queue_lock);
1073 }
1074 
1075 /**
1076  * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1077  * @work: work item being executed
1078  *
1079  * This function is queued for execution when bio's reach the bio_lists[]
1080  * of throtl_data->service_queue.  Those bio's are ready and issued by this
1081  * function.
1082  */
1083 static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1084 {
1085         struct throtl_data *td = container_of(work, struct throtl_data,
1086                                               dispatch_work);
1087         struct throtl_service_queue *td_sq = &td->service_queue;
1088         struct request_queue *q = td->queue;
1089         struct bio_list bio_list_on_stack;
1090         struct bio *bio;
1091         struct blk_plug plug;
1092         int rw;
1093 
1094         bio_list_init(&bio_list_on_stack);
1095 
1096         spin_lock_irq(q->queue_lock);
1097         for (rw = READ; rw <= WRITE; rw++)
1098                 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1099                         bio_list_add(&bio_list_on_stack, bio);
1100         spin_unlock_irq(q->queue_lock);
1101 
1102         if (!bio_list_empty(&bio_list_on_stack)) {
1103                 blk_start_plug(&plug);
1104                 while((bio = bio_list_pop(&bio_list_on_stack)))
1105                         generic_make_request(bio);
1106                 blk_finish_plug(&plug);
1107         }
1108 }
1109 
1110 static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1111                               int off)
1112 {
1113         struct throtl_grp *tg = pd_to_tg(pd);
1114         u64 v = *(u64 *)((void *)tg + off);
1115 
1116         if (v == -1)
1117                 return 0;
1118         return __blkg_prfill_u64(sf, pd, v);
1119 }
1120 
1121 static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1122                                int off)
1123 {
1124         struct throtl_grp *tg = pd_to_tg(pd);
1125         unsigned int v = *(unsigned int *)((void *)tg + off);
1126 
1127         if (v == -1)
1128                 return 0;
1129         return __blkg_prfill_u64(sf, pd, v);
1130 }
1131 
1132 static int tg_print_conf_u64(struct seq_file *sf, void *v)
1133 {
1134         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1135                           &blkcg_policy_throtl, seq_cft(sf)->private, false);
1136         return 0;
1137 }
1138 
1139 static int tg_print_conf_uint(struct seq_file *sf, void *v)
1140 {
1141         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1142                           &blkcg_policy_throtl, seq_cft(sf)->private, false);
1143         return 0;
1144 }
1145 
1146 static void tg_conf_updated(struct throtl_grp *tg)
1147 {
1148         struct throtl_service_queue *sq = &tg->service_queue;
1149         struct cgroup_subsys_state *pos_css;
1150         struct blkcg_gq *blkg;
1151 
1152         throtl_log(&tg->service_queue,
1153                    "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1154                    tg->bps[READ], tg->bps[WRITE],
1155                    tg->iops[READ], tg->iops[WRITE]);
1156 
1157         /*
1158          * Update has_rules[] flags for the updated tg's subtree.  A tg is
1159          * considered to have rules if either the tg itself or any of its
1160          * ancestors has rules.  This identifies groups without any
1161          * restrictions in the whole hierarchy and allows them to bypass
1162          * blk-throttle.
1163          */
1164         blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg))
1165                 tg_update_has_rules(blkg_to_tg(blkg));
1166 
1167         /*
1168          * We're already holding queue_lock and know @tg is valid.  Let's
1169          * apply the new config directly.
1170          *
1171          * Restart the slices for both READ and WRITES. It might happen
1172          * that a group's limit are dropped suddenly and we don't want to
1173          * account recently dispatched IO with new low rate.
1174          */
1175         throtl_start_new_slice(tg, 0);
1176         throtl_start_new_slice(tg, 1);
1177 
1178         if (tg->flags & THROTL_TG_PENDING) {
1179                 tg_update_disptime(tg);
1180                 throtl_schedule_next_dispatch(sq->parent_sq, true);
1181         }
1182 }
1183 
1184 static ssize_t tg_set_conf(struct kernfs_open_file *of,
1185                            char *buf, size_t nbytes, loff_t off, bool is_u64)
1186 {
1187         struct blkcg *blkcg = css_to_blkcg(of_css(of));
1188         struct blkg_conf_ctx ctx;
1189         struct throtl_grp *tg;
1190         int ret;
1191         u64 v;
1192 
1193         ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1194         if (ret)
1195                 return ret;
1196 
1197         ret = -EINVAL;
1198         if (sscanf(ctx.body, "%llu", &v) != 1)
1199                 goto out_finish;
1200         if (!v)
1201                 v = -1;
1202 
1203         tg = blkg_to_tg(ctx.blkg);
1204 
1205         if (is_u64)
1206                 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1207         else
1208                 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1209 
1210         tg_conf_updated(tg);
1211         ret = 0;
1212 out_finish:
1213         blkg_conf_finish(&ctx);
1214         return ret ?: nbytes;
1215 }
1216 
1217 static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1218                                char *buf, size_t nbytes, loff_t off)
1219 {
1220         return tg_set_conf(of, buf, nbytes, off, true);
1221 }
1222 
1223 static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1224                                 char *buf, size_t nbytes, loff_t off)
1225 {
1226         return tg_set_conf(of, buf, nbytes, off, false);
1227 }
1228 
1229 static struct cftype throtl_legacy_files[] = {
1230         {
1231                 .name = "throttle.read_bps_device",
1232                 .private = offsetof(struct throtl_grp, bps[READ]),
1233                 .seq_show = tg_print_conf_u64,
1234                 .write = tg_set_conf_u64,
1235         },
1236         {
1237                 .name = "throttle.write_bps_device",
1238                 .private = offsetof(struct throtl_grp, bps[WRITE]),
1239                 .seq_show = tg_print_conf_u64,
1240                 .write = tg_set_conf_u64,
1241         },
1242         {
1243                 .name = "throttle.read_iops_device",
1244                 .private = offsetof(struct throtl_grp, iops[READ]),
1245                 .seq_show = tg_print_conf_uint,
1246                 .write = tg_set_conf_uint,
1247         },
1248         {
1249                 .name = "throttle.write_iops_device",
1250                 .private = offsetof(struct throtl_grp, iops[WRITE]),
1251                 .seq_show = tg_print_conf_uint,
1252                 .write = tg_set_conf_uint,
1253         },
1254         {
1255                 .name = "throttle.io_service_bytes",
1256                 .private = (unsigned long)&blkcg_policy_throtl,
1257                 .seq_show = blkg_print_stat_bytes,
1258         },
1259         {
1260                 .name = "throttle.io_serviced",
1261                 .private = (unsigned long)&blkcg_policy_throtl,
1262                 .seq_show = blkg_print_stat_ios,
1263         },
1264         { }     /* terminate */
1265 };
1266 
1267 static u64 tg_prfill_max(struct seq_file *sf, struct blkg_policy_data *pd,
1268                          int off)
1269 {
1270         struct throtl_grp *tg = pd_to_tg(pd);
1271         const char *dname = blkg_dev_name(pd->blkg);
1272         char bufs[4][21] = { "max", "max", "max", "max" };
1273 
1274         if (!dname)
1275                 return 0;
1276         if (tg->bps[READ] == -1 && tg->bps[WRITE] == -1 &&
1277             tg->iops[READ] == -1 && tg->iops[WRITE] == -1)
1278                 return 0;
1279 
1280         if (tg->bps[READ] != -1)
1281                 snprintf(bufs[0], sizeof(bufs[0]), "%llu", tg->bps[READ]);
1282         if (tg->bps[WRITE] != -1)
1283                 snprintf(bufs[1], sizeof(bufs[1]), "%llu", tg->bps[WRITE]);
1284         if (tg->iops[READ] != -1)
1285                 snprintf(bufs[2], sizeof(bufs[2]), "%u", tg->iops[READ]);
1286         if (tg->iops[WRITE] != -1)
1287                 snprintf(bufs[3], sizeof(bufs[3]), "%u", tg->iops[WRITE]);
1288 
1289         seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s\n",
1290                    dname, bufs[0], bufs[1], bufs[2], bufs[3]);
1291         return 0;
1292 }
1293 
1294 static int tg_print_max(struct seq_file *sf, void *v)
1295 {
1296         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_max,
1297                           &blkcg_policy_throtl, seq_cft(sf)->private, false);
1298         return 0;
1299 }
1300 
1301 static ssize_t tg_set_max(struct kernfs_open_file *of,
1302                           char *buf, size_t nbytes, loff_t off)
1303 {
1304         struct blkcg *blkcg = css_to_blkcg(of_css(of));
1305         struct blkg_conf_ctx ctx;
1306         struct throtl_grp *tg;
1307         u64 v[4];
1308         int ret;
1309 
1310         ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1311         if (ret)
1312                 return ret;
1313 
1314         tg = blkg_to_tg(ctx.blkg);
1315 
1316         v[0] = tg->bps[READ];
1317         v[1] = tg->bps[WRITE];
1318         v[2] = tg->iops[READ];
1319         v[3] = tg->iops[WRITE];
1320 
1321         while (true) {
1322                 char tok[27];   /* wiops=18446744073709551616 */
1323                 char *p;
1324                 u64 val = -1;
1325                 int len;
1326 
1327                 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1328                         break;
1329                 if (tok[0] == '\0')
1330                         break;
1331                 ctx.body += len;
1332 
1333                 ret = -EINVAL;
1334                 p = tok;
1335                 strsep(&p, "=");
1336                 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1337                         goto out_finish;
1338 
1339                 ret = -ERANGE;
1340                 if (!val)
1341                         goto out_finish;
1342 
1343                 ret = -EINVAL;
1344                 if (!strcmp(tok, "rbps"))
1345                         v[0] = val;
1346                 else if (!strcmp(tok, "wbps"))
1347                         v[1] = val;
1348                 else if (!strcmp(tok, "riops"))
1349                         v[2] = min_t(u64, val, UINT_MAX);
1350                 else if (!strcmp(tok, "wiops"))
1351                         v[3] = min_t(u64, val, UINT_MAX);
1352                 else
1353                         goto out_finish;
1354         }
1355 
1356         tg->bps[READ] = v[0];
1357         tg->bps[WRITE] = v[1];
1358         tg->iops[READ] = v[2];
1359         tg->iops[WRITE] = v[3];
1360 
1361         tg_conf_updated(tg);
1362         ret = 0;
1363 out_finish:
1364         blkg_conf_finish(&ctx);
1365         return ret ?: nbytes;
1366 }
1367 
1368 static struct cftype throtl_files[] = {
1369         {
1370                 .name = "max",
1371                 .flags = CFTYPE_NOT_ON_ROOT,
1372                 .seq_show = tg_print_max,
1373                 .write = tg_set_max,
1374         },
1375         { }     /* terminate */
1376 };
1377 
1378 static void throtl_shutdown_wq(struct request_queue *q)
1379 {
1380         struct throtl_data *td = q->td;
1381 
1382         cancel_work_sync(&td->dispatch_work);
1383 }
1384 
1385 static struct blkcg_policy blkcg_policy_throtl = {
1386         .dfl_cftypes            = throtl_files,
1387         .legacy_cftypes         = throtl_legacy_files,
1388 
1389         .pd_alloc_fn            = throtl_pd_alloc,
1390         .pd_init_fn             = throtl_pd_init,
1391         .pd_online_fn           = throtl_pd_online,
1392         .pd_free_fn             = throtl_pd_free,
1393 };
1394 
1395 bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
1396                     struct bio *bio)
1397 {
1398         struct throtl_qnode *qn = NULL;
1399         struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
1400         struct throtl_service_queue *sq;
1401         bool rw = bio_data_dir(bio);
1402         bool throttled = false;
1403 
1404         WARN_ON_ONCE(!rcu_read_lock_held());
1405 
1406         /* see throtl_charge_bio() */
1407         if ((bio->bi_rw & REQ_THROTTLED) || !tg->has_rules[rw])
1408                 goto out;
1409 
1410         spin_lock_irq(q->queue_lock);
1411 
1412         if (unlikely(blk_queue_bypass(q)))
1413                 goto out_unlock;
1414 
1415         sq = &tg->service_queue;
1416 
1417         while (true) {
1418                 /* throtl is FIFO - if bios are already queued, should queue */
1419                 if (sq->nr_queued[rw])
1420                         break;
1421 
1422                 /* if above limits, break to queue */
1423                 if (!tg_may_dispatch(tg, bio, NULL))
1424                         break;
1425 
1426                 /* within limits, let's charge and dispatch directly */
1427                 throtl_charge_bio(tg, bio);
1428 
1429                 /*
1430                  * We need to trim slice even when bios are not being queued
1431                  * otherwise it might happen that a bio is not queued for
1432                  * a long time and slice keeps on extending and trim is not
1433                  * called for a long time. Now if limits are reduced suddenly
1434                  * we take into account all the IO dispatched so far at new
1435                  * low rate and * newly queued IO gets a really long dispatch
1436                  * time.
1437                  *
1438                  * So keep on trimming slice even if bio is not queued.
1439                  */
1440                 throtl_trim_slice(tg, rw);
1441 
1442                 /*
1443                  * @bio passed through this layer without being throttled.
1444                  * Climb up the ladder.  If we''re already at the top, it
1445                  * can be executed directly.
1446                  */
1447                 qn = &tg->qnode_on_parent[rw];
1448                 sq = sq->parent_sq;
1449                 tg = sq_to_tg(sq);
1450                 if (!tg)
1451                         goto out_unlock;
1452         }
1453 
1454         /* out-of-limit, queue to @tg */
1455         throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1456                    rw == READ ? 'R' : 'W',
1457                    tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw],
1458                    tg->io_disp[rw], tg->iops[rw],
1459                    sq->nr_queued[READ], sq->nr_queued[WRITE]);
1460 
1461         bio_associate_current(bio);
1462         tg->td->nr_queued[rw]++;
1463         throtl_add_bio_tg(bio, qn, tg);
1464         throttled = true;
1465 
1466         /*
1467          * Update @tg's dispatch time and force schedule dispatch if @tg
1468          * was empty before @bio.  The forced scheduling isn't likely to
1469          * cause undue delay as @bio is likely to be dispatched directly if
1470          * its @tg's disptime is not in the future.
1471          */
1472         if (tg->flags & THROTL_TG_WAS_EMPTY) {
1473                 tg_update_disptime(tg);
1474                 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
1475         }
1476 
1477 out_unlock:
1478         spin_unlock_irq(q->queue_lock);
1479 out:
1480         /*
1481          * As multiple blk-throtls may stack in the same issue path, we
1482          * don't want bios to leave with the flag set.  Clear the flag if
1483          * being issued.
1484          */
1485         if (!throttled)
1486                 bio->bi_rw &= ~REQ_THROTTLED;
1487         return throttled;
1488 }
1489 
1490 /*
1491  * Dispatch all bios from all children tg's queued on @parent_sq.  On
1492  * return, @parent_sq is guaranteed to not have any active children tg's
1493  * and all bios from previously active tg's are on @parent_sq->bio_lists[].
1494  */
1495 static void tg_drain_bios(struct throtl_service_queue *parent_sq)
1496 {
1497         struct throtl_grp *tg;
1498 
1499         while ((tg = throtl_rb_first(parent_sq))) {
1500                 struct throtl_service_queue *sq = &tg->service_queue;
1501                 struct bio *bio;
1502 
1503                 throtl_dequeue_tg(tg);
1504 
1505                 while ((bio = throtl_peek_queued(&sq->queued[READ])))
1506                         tg_dispatch_one_bio(tg, bio_data_dir(bio));
1507                 while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
1508                         tg_dispatch_one_bio(tg, bio_data_dir(bio));
1509         }
1510 }
1511 
1512 /**
1513  * blk_throtl_drain - drain throttled bios
1514  * @q: request_queue to drain throttled bios for
1515  *
1516  * Dispatch all currently throttled bios on @q through ->make_request_fn().
1517  */
1518 void blk_throtl_drain(struct request_queue *q)
1519         __releases(q->queue_lock) __acquires(q->queue_lock)
1520 {
1521         struct throtl_data *td = q->td;
1522         struct blkcg_gq *blkg;
1523         struct cgroup_subsys_state *pos_css;
1524         struct bio *bio;
1525         int rw;
1526 
1527         queue_lockdep_assert_held(q);
1528         rcu_read_lock();
1529 
1530         /*
1531          * Drain each tg while doing post-order walk on the blkg tree, so
1532          * that all bios are propagated to td->service_queue.  It'd be
1533          * better to walk service_queue tree directly but blkg walk is
1534          * easier.
1535          */
1536         blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
1537                 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
1538 
1539         /* finally, transfer bios from top-level tg's into the td */
1540         tg_drain_bios(&td->service_queue);
1541 
1542         rcu_read_unlock();
1543         spin_unlock_irq(q->queue_lock);
1544 
1545         /* all bios now should be in td->service_queue, issue them */
1546         for (rw = READ; rw <= WRITE; rw++)
1547                 while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
1548                                                 NULL)))
1549                         generic_make_request(bio);
1550 
1551         spin_lock_irq(q->queue_lock);
1552 }
1553 
1554 int blk_throtl_init(struct request_queue *q)
1555 {
1556         struct throtl_data *td;
1557         int ret;
1558 
1559         td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1560         if (!td)
1561                 return -ENOMEM;
1562 
1563         INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
1564         throtl_service_queue_init(&td->service_queue);
1565 
1566         q->td = td;
1567         td->queue = q;
1568 
1569         /* activate policy */
1570         ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1571         if (ret)
1572                 kfree(td);
1573         return ret;
1574 }
1575 
1576 void blk_throtl_exit(struct request_queue *q)
1577 {
1578         BUG_ON(!q->td);
1579         throtl_shutdown_wq(q);
1580         blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1581         kfree(q->td);
1582 }
1583 
1584 static int __init throtl_init(void)
1585 {
1586         kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1587         if (!kthrotld_workqueue)
1588                 panic("Failed to create kthrotld\n");
1589 
1590         return blkcg_policy_register(&blkcg_policy_throtl);
1591 }
1592 
1593 module_init(throtl_init);
1594 

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