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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 | /* A workqueue to queue throttle related work */ |
25 | static struct workqueue_struct *kthrotld_workqueue; |
26 | static void throtl_schedule_delayed_work(struct throtl_data *td, |
27 | unsigned long delay); |
28 | |
29 | struct throtl_rb_root { |
30 | struct rb_root rb; |
31 | struct rb_node *left; |
32 | unsigned int count; |
33 | unsigned long min_disptime; |
34 | }; |
35 | |
36 | #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \ |
37 | .count = 0, .min_disptime = 0} |
38 | |
39 | #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) |
40 | |
41 | struct throtl_grp { |
42 | /* List of throtl groups on the request queue*/ |
43 | struct hlist_node tg_node; |
44 | |
45 | /* active throtl group service_tree member */ |
46 | struct rb_node rb_node; |
47 | |
48 | /* |
49 | * Dispatch time in jiffies. This is the estimated time when group |
50 | * will unthrottle and is ready to dispatch more bio. It is used as |
51 | * key to sort active groups in service tree. |
52 | */ |
53 | unsigned long disptime; |
54 | |
55 | struct blkio_group blkg; |
56 | atomic_t ref; |
57 | unsigned int flags; |
58 | |
59 | /* Two lists for READ and WRITE */ |
60 | struct bio_list bio_lists[2]; |
61 | |
62 | /* Number of queued bios on READ and WRITE lists */ |
63 | unsigned int nr_queued[2]; |
64 | |
65 | /* bytes per second rate limits */ |
66 | uint64_t bps[2]; |
67 | |
68 | /* IOPS limits */ |
69 | unsigned int iops[2]; |
70 | |
71 | /* Number of bytes disptached in current slice */ |
72 | uint64_t bytes_disp[2]; |
73 | /* Number of bio's dispatched in current slice */ |
74 | unsigned int io_disp[2]; |
75 | |
76 | /* When did we start a new slice */ |
77 | unsigned long slice_start[2]; |
78 | unsigned long slice_end[2]; |
79 | |
80 | /* Some throttle limits got updated for the group */ |
81 | int limits_changed; |
82 | |
83 | struct rcu_head rcu_head; |
84 | }; |
85 | |
86 | struct throtl_data |
87 | { |
88 | /* List of throtl groups */ |
89 | struct hlist_head tg_list; |
90 | |
91 | /* service tree for active throtl groups */ |
92 | struct throtl_rb_root tg_service_tree; |
93 | |
94 | struct throtl_grp *root_tg; |
95 | struct request_queue *queue; |
96 | |
97 | /* Total Number of queued bios on READ and WRITE lists */ |
98 | unsigned int nr_queued[2]; |
99 | |
100 | /* |
101 | * number of total undestroyed groups |
102 | */ |
103 | unsigned int nr_undestroyed_grps; |
104 | |
105 | /* Work for dispatching throttled bios */ |
106 | struct delayed_work throtl_work; |
107 | |
108 | int limits_changed; |
109 | }; |
110 | |
111 | enum tg_state_flags { |
112 | THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */ |
113 | }; |
114 | |
115 | #define THROTL_TG_FNS(name) \ |
116 | static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \ |
117 | { \ |
118 | (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \ |
119 | } \ |
120 | static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \ |
121 | { \ |
122 | (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \ |
123 | } \ |
124 | static inline int throtl_tg_##name(const struct throtl_grp *tg) \ |
125 | { \ |
126 | return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \ |
127 | } |
128 | |
129 | THROTL_TG_FNS(on_rr); |
130 | |
131 | #define throtl_log_tg(td, tg, fmt, args...) \ |
132 | blk_add_trace_msg((td)->queue, "throtl %s " fmt, \ |
133 | blkg_path(&(tg)->blkg), ##args); \ |
134 | |
135 | #define throtl_log(td, fmt, args...) \ |
136 | blk_add_trace_msg((td)->queue, "throtl " fmt, ##args) |
137 | |
138 | static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg) |
139 | { |
140 | if (blkg) |
141 | return container_of(blkg, struct throtl_grp, blkg); |
142 | |
143 | return NULL; |
144 | } |
145 | |
146 | static inline unsigned int total_nr_queued(struct throtl_data *td) |
147 | { |
148 | return td->nr_queued[0] + td->nr_queued[1]; |
149 | } |
150 | |
151 | static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg) |
152 | { |
153 | atomic_inc(&tg->ref); |
154 | return tg; |
155 | } |
156 | |
157 | static void throtl_free_tg(struct rcu_head *head) |
158 | { |
159 | struct throtl_grp *tg; |
160 | |
161 | tg = container_of(head, struct throtl_grp, rcu_head); |
162 | free_percpu(tg->blkg.stats_cpu); |
163 | kfree(tg); |
164 | } |
165 | |
166 | static void throtl_put_tg(struct throtl_grp *tg) |
167 | { |
168 | BUG_ON(atomic_read(&tg->ref) <= 0); |
169 | if (!atomic_dec_and_test(&tg->ref)) |
170 | return; |
171 | |
172 | /* |
173 | * A group is freed in rcu manner. But having an rcu lock does not |
174 | * mean that one can access all the fields of blkg and assume these |
175 | * are valid. For example, don't try to follow throtl_data and |
176 | * request queue links. |
177 | * |
178 | * Having a reference to blkg under an rcu allows acess to only |
179 | * values local to groups like group stats and group rate limits |
180 | */ |
181 | call_rcu(&tg->rcu_head, throtl_free_tg); |
182 | } |
183 | |
184 | static void throtl_init_group(struct throtl_grp *tg) |
185 | { |
186 | INIT_HLIST_NODE(&tg->tg_node); |
187 | RB_CLEAR_NODE(&tg->rb_node); |
188 | bio_list_init(&tg->bio_lists[0]); |
189 | bio_list_init(&tg->bio_lists[1]); |
190 | tg->limits_changed = false; |
191 | |
192 | /* Practically unlimited BW */ |
193 | tg->bps[0] = tg->bps[1] = -1; |
194 | tg->iops[0] = tg->iops[1] = -1; |
195 | |
196 | /* |
197 | * Take the initial reference that will be released on destroy |
198 | * This can be thought of a joint reference by cgroup and |
199 | * request queue which will be dropped by either request queue |
200 | * exit or cgroup deletion path depending on who is exiting first. |
201 | */ |
202 | atomic_set(&tg->ref, 1); |
203 | } |
204 | |
205 | /* Should be called with rcu read lock held (needed for blkcg) */ |
206 | static void |
207 | throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg) |
208 | { |
209 | hlist_add_head(&tg->tg_node, &td->tg_list); |
210 | td->nr_undestroyed_grps++; |
211 | } |
212 | |
213 | static void |
214 | __throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg) |
215 | { |
216 | struct backing_dev_info *bdi = &td->queue->backing_dev_info; |
217 | unsigned int major, minor; |
218 | |
219 | if (!tg || tg->blkg.dev) |
220 | return; |
221 | |
222 | /* |
223 | * Fill in device details for a group which might not have been |
224 | * filled at group creation time as queue was being instantiated |
225 | * and driver had not attached a device yet |
226 | */ |
227 | if (bdi->dev && dev_name(bdi->dev)) { |
228 | sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); |
229 | tg->blkg.dev = MKDEV(major, minor); |
230 | } |
231 | } |
232 | |
233 | /* |
234 | * Should be called with without queue lock held. Here queue lock will be |
235 | * taken rarely. It will be taken only once during life time of a group |
236 | * if need be |
237 | */ |
238 | static void |
239 | throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg) |
240 | { |
241 | if (!tg || tg->blkg.dev) |
242 | return; |
243 | |
244 | spin_lock_irq(td->queue->queue_lock); |
245 | __throtl_tg_fill_dev_details(td, tg); |
246 | spin_unlock_irq(td->queue->queue_lock); |
247 | } |
248 | |
249 | static void throtl_init_add_tg_lists(struct throtl_data *td, |
250 | struct throtl_grp *tg, struct blkio_cgroup *blkcg) |
251 | { |
252 | __throtl_tg_fill_dev_details(td, tg); |
253 | |
254 | /* Add group onto cgroup list */ |
255 | blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td, |
256 | tg->blkg.dev, BLKIO_POLICY_THROTL); |
257 | |
258 | tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev); |
259 | tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev); |
260 | tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev); |
261 | tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev); |
262 | |
263 | throtl_add_group_to_td_list(td, tg); |
264 | } |
265 | |
266 | /* Should be called without queue lock and outside of rcu period */ |
267 | static struct throtl_grp *throtl_alloc_tg(struct throtl_data *td) |
268 | { |
269 | struct throtl_grp *tg = NULL; |
270 | int ret; |
271 | |
272 | tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node); |
273 | if (!tg) |
274 | return NULL; |
275 | |
276 | ret = blkio_alloc_blkg_stats(&tg->blkg); |
277 | |
278 | if (ret) { |
279 | kfree(tg); |
280 | return NULL; |
281 | } |
282 | |
283 | throtl_init_group(tg); |
284 | return tg; |
285 | } |
286 | |
287 | static struct |
288 | throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg) |
289 | { |
290 | struct throtl_grp *tg = NULL; |
291 | void *key = td; |
292 | |
293 | /* |
294 | * This is the common case when there are no blkio cgroups. |
295 | * Avoid lookup in this case |
296 | */ |
297 | if (blkcg == &blkio_root_cgroup) |
298 | tg = td->root_tg; |
299 | else |
300 | tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key)); |
301 | |
302 | __throtl_tg_fill_dev_details(td, tg); |
303 | return tg; |
304 | } |
305 | |
306 | static struct throtl_grp * throtl_get_tg(struct throtl_data *td) |
307 | { |
308 | struct throtl_grp *tg = NULL, *__tg = NULL; |
309 | struct blkio_cgroup *blkcg; |
310 | struct request_queue *q = td->queue; |
311 | |
312 | /* no throttling for dead queue */ |
313 | if (unlikely(blk_queue_dead(q))) |
314 | return NULL; |
315 | |
316 | rcu_read_lock(); |
317 | blkcg = task_blkio_cgroup(current); |
318 | tg = throtl_find_tg(td, blkcg); |
319 | if (tg) { |
320 | rcu_read_unlock(); |
321 | return tg; |
322 | } |
323 | |
324 | /* |
325 | * Need to allocate a group. Allocation of group also needs allocation |
326 | * of per cpu stats which in-turn takes a mutex() and can block. Hence |
327 | * we need to drop rcu lock and queue_lock before we call alloc. |
328 | */ |
329 | rcu_read_unlock(); |
330 | spin_unlock_irq(q->queue_lock); |
331 | |
332 | tg = throtl_alloc_tg(td); |
333 | |
334 | /* Group allocated and queue is still alive. take the lock */ |
335 | spin_lock_irq(q->queue_lock); |
336 | |
337 | /* Make sure @q is still alive */ |
338 | if (unlikely(blk_queue_dead(q))) { |
339 | kfree(tg); |
340 | return NULL; |
341 | } |
342 | |
343 | /* |
344 | * Initialize the new group. After sleeping, read the blkcg again. |
345 | */ |
346 | rcu_read_lock(); |
347 | blkcg = task_blkio_cgroup(current); |
348 | |
349 | /* |
350 | * If some other thread already allocated the group while we were |
351 | * not holding queue lock, free up the group |
352 | */ |
353 | __tg = throtl_find_tg(td, blkcg); |
354 | |
355 | if (__tg) { |
356 | kfree(tg); |
357 | rcu_read_unlock(); |
358 | return __tg; |
359 | } |
360 | |
361 | /* Group allocation failed. Account the IO to root group */ |
362 | if (!tg) { |
363 | tg = td->root_tg; |
364 | return tg; |
365 | } |
366 | |
367 | throtl_init_add_tg_lists(td, tg, blkcg); |
368 | rcu_read_unlock(); |
369 | return tg; |
370 | } |
371 | |
372 | static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root) |
373 | { |
374 | /* Service tree is empty */ |
375 | if (!root->count) |
376 | return NULL; |
377 | |
378 | if (!root->left) |
379 | root->left = rb_first(&root->rb); |
380 | |
381 | if (root->left) |
382 | return rb_entry_tg(root->left); |
383 | |
384 | return NULL; |
385 | } |
386 | |
387 | static void rb_erase_init(struct rb_node *n, struct rb_root *root) |
388 | { |
389 | rb_erase(n, root); |
390 | RB_CLEAR_NODE(n); |
391 | } |
392 | |
393 | static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root) |
394 | { |
395 | if (root->left == n) |
396 | root->left = NULL; |
397 | rb_erase_init(n, &root->rb); |
398 | --root->count; |
399 | } |
400 | |
401 | static void update_min_dispatch_time(struct throtl_rb_root *st) |
402 | { |
403 | struct throtl_grp *tg; |
404 | |
405 | tg = throtl_rb_first(st); |
406 | if (!tg) |
407 | return; |
408 | |
409 | st->min_disptime = tg->disptime; |
410 | } |
411 | |
412 | static void |
413 | tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) |
414 | { |
415 | struct rb_node **node = &st->rb.rb_node; |
416 | struct rb_node *parent = NULL; |
417 | struct throtl_grp *__tg; |
418 | unsigned long key = tg->disptime; |
419 | int left = 1; |
420 | |
421 | while (*node != NULL) { |
422 | parent = *node; |
423 | __tg = rb_entry_tg(parent); |
424 | |
425 | if (time_before(key, __tg->disptime)) |
426 | node = &parent->rb_left; |
427 | else { |
428 | node = &parent->rb_right; |
429 | left = 0; |
430 | } |
431 | } |
432 | |
433 | if (left) |
434 | st->left = &tg->rb_node; |
435 | |
436 | rb_link_node(&tg->rb_node, parent, node); |
437 | rb_insert_color(&tg->rb_node, &st->rb); |
438 | } |
439 | |
440 | static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) |
441 | { |
442 | struct throtl_rb_root *st = &td->tg_service_tree; |
443 | |
444 | tg_service_tree_add(st, tg); |
445 | throtl_mark_tg_on_rr(tg); |
446 | st->count++; |
447 | } |
448 | |
449 | static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) |
450 | { |
451 | if (!throtl_tg_on_rr(tg)) |
452 | __throtl_enqueue_tg(td, tg); |
453 | } |
454 | |
455 | static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) |
456 | { |
457 | throtl_rb_erase(&tg->rb_node, &td->tg_service_tree); |
458 | throtl_clear_tg_on_rr(tg); |
459 | } |
460 | |
461 | static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) |
462 | { |
463 | if (throtl_tg_on_rr(tg)) |
464 | __throtl_dequeue_tg(td, tg); |
465 | } |
466 | |
467 | static void throtl_schedule_next_dispatch(struct throtl_data *td) |
468 | { |
469 | struct throtl_rb_root *st = &td->tg_service_tree; |
470 | |
471 | /* |
472 | * If there are more bios pending, schedule more work. |
473 | */ |
474 | if (!total_nr_queued(td)) |
475 | return; |
476 | |
477 | BUG_ON(!st->count); |
478 | |
479 | update_min_dispatch_time(st); |
480 | |
481 | if (time_before_eq(st->min_disptime, jiffies)) |
482 | throtl_schedule_delayed_work(td, 0); |
483 | else |
484 | throtl_schedule_delayed_work(td, (st->min_disptime - jiffies)); |
485 | } |
486 | |
487 | static inline void |
488 | throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) |
489 | { |
490 | tg->bytes_disp[rw] = 0; |
491 | tg->io_disp[rw] = 0; |
492 | tg->slice_start[rw] = jiffies; |
493 | tg->slice_end[rw] = jiffies + throtl_slice; |
494 | throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu", |
495 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
496 | tg->slice_end[rw], jiffies); |
497 | } |
498 | |
499 | static inline void throtl_set_slice_end(struct throtl_data *td, |
500 | struct throtl_grp *tg, bool rw, unsigned long jiffy_end) |
501 | { |
502 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); |
503 | } |
504 | |
505 | static inline void throtl_extend_slice(struct throtl_data *td, |
506 | struct throtl_grp *tg, bool rw, unsigned long jiffy_end) |
507 | { |
508 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); |
509 | throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu", |
510 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
511 | tg->slice_end[rw], jiffies); |
512 | } |
513 | |
514 | /* Determine if previously allocated or extended slice is complete or not */ |
515 | static bool |
516 | throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) |
517 | { |
518 | if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) |
519 | return 0; |
520 | |
521 | return 1; |
522 | } |
523 | |
524 | /* Trim the used slices and adjust slice start accordingly */ |
525 | static inline void |
526 | throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) |
527 | { |
528 | unsigned long nr_slices, time_elapsed, io_trim; |
529 | u64 bytes_trim, tmp; |
530 | |
531 | BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); |
532 | |
533 | /* |
534 | * If bps are unlimited (-1), then time slice don't get |
535 | * renewed. Don't try to trim the slice if slice is used. A new |
536 | * slice will start when appropriate. |
537 | */ |
538 | if (throtl_slice_used(td, tg, rw)) |
539 | return; |
540 | |
541 | /* |
542 | * A bio has been dispatched. Also adjust slice_end. It might happen |
543 | * that initially cgroup limit was very low resulting in high |
544 | * slice_end, but later limit was bumped up and bio was dispached |
545 | * sooner, then we need to reduce slice_end. A high bogus slice_end |
546 | * is bad because it does not allow new slice to start. |
547 | */ |
548 | |
549 | throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice); |
550 | |
551 | time_elapsed = jiffies - tg->slice_start[rw]; |
552 | |
553 | nr_slices = time_elapsed / throtl_slice; |
554 | |
555 | if (!nr_slices) |
556 | return; |
557 | tmp = tg->bps[rw] * throtl_slice * nr_slices; |
558 | do_div(tmp, HZ); |
559 | bytes_trim = tmp; |
560 | |
561 | io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; |
562 | |
563 | if (!bytes_trim && !io_trim) |
564 | return; |
565 | |
566 | if (tg->bytes_disp[rw] >= bytes_trim) |
567 | tg->bytes_disp[rw] -= bytes_trim; |
568 | else |
569 | tg->bytes_disp[rw] = 0; |
570 | |
571 | if (tg->io_disp[rw] >= io_trim) |
572 | tg->io_disp[rw] -= io_trim; |
573 | else |
574 | tg->io_disp[rw] = 0; |
575 | |
576 | tg->slice_start[rw] += nr_slices * throtl_slice; |
577 | |
578 | throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu" |
579 | " start=%lu end=%lu jiffies=%lu", |
580 | rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, |
581 | tg->slice_start[rw], tg->slice_end[rw], jiffies); |
582 | } |
583 | |
584 | static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, |
585 | struct bio *bio, unsigned long *wait) |
586 | { |
587 | bool rw = bio_data_dir(bio); |
588 | unsigned int io_allowed; |
589 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
590 | u64 tmp; |
591 | |
592 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
593 | |
594 | /* Slice has just started. Consider one slice interval */ |
595 | if (!jiffy_elapsed) |
596 | jiffy_elapsed_rnd = throtl_slice; |
597 | |
598 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); |
599 | |
600 | /* |
601 | * jiffy_elapsed_rnd should not be a big value as minimum iops can be |
602 | * 1 then at max jiffy elapsed should be equivalent of 1 second as we |
603 | * will allow dispatch after 1 second and after that slice should |
604 | * have been trimmed. |
605 | */ |
606 | |
607 | tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; |
608 | do_div(tmp, HZ); |
609 | |
610 | if (tmp > UINT_MAX) |
611 | io_allowed = UINT_MAX; |
612 | else |
613 | io_allowed = tmp; |
614 | |
615 | if (tg->io_disp[rw] + 1 <= io_allowed) { |
616 | if (wait) |
617 | *wait = 0; |
618 | return 1; |
619 | } |
620 | |
621 | /* Calc approx time to dispatch */ |
622 | jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; |
623 | |
624 | if (jiffy_wait > jiffy_elapsed) |
625 | jiffy_wait = jiffy_wait - jiffy_elapsed; |
626 | else |
627 | jiffy_wait = 1; |
628 | |
629 | if (wait) |
630 | *wait = jiffy_wait; |
631 | return 0; |
632 | } |
633 | |
634 | static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg, |
635 | struct bio *bio, unsigned long *wait) |
636 | { |
637 | bool rw = bio_data_dir(bio); |
638 | u64 bytes_allowed, extra_bytes, tmp; |
639 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
640 | |
641 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
642 | |
643 | /* Slice has just started. Consider one slice interval */ |
644 | if (!jiffy_elapsed) |
645 | jiffy_elapsed_rnd = throtl_slice; |
646 | |
647 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); |
648 | |
649 | tmp = tg->bps[rw] * jiffy_elapsed_rnd; |
650 | do_div(tmp, HZ); |
651 | bytes_allowed = tmp; |
652 | |
653 | if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) { |
654 | if (wait) |
655 | *wait = 0; |
656 | return 1; |
657 | } |
658 | |
659 | /* Calc approx time to dispatch */ |
660 | extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed; |
661 | jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); |
662 | |
663 | if (!jiffy_wait) |
664 | jiffy_wait = 1; |
665 | |
666 | /* |
667 | * This wait time is without taking into consideration the rounding |
668 | * up we did. Add that time also. |
669 | */ |
670 | jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); |
671 | if (wait) |
672 | *wait = jiffy_wait; |
673 | return 0; |
674 | } |
675 | |
676 | static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) { |
677 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) |
678 | return 1; |
679 | return 0; |
680 | } |
681 | |
682 | /* |
683 | * Returns whether one can dispatch a bio or not. Also returns approx number |
684 | * of jiffies to wait before this bio is with-in IO rate and can be dispatched |
685 | */ |
686 | static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, |
687 | struct bio *bio, unsigned long *wait) |
688 | { |
689 | bool rw = bio_data_dir(bio); |
690 | unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; |
691 | |
692 | /* |
693 | * Currently whole state machine of group depends on first bio |
694 | * queued in the group bio list. So one should not be calling |
695 | * this function with a different bio if there are other bios |
696 | * queued. |
697 | */ |
698 | BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw])); |
699 | |
700 | /* If tg->bps = -1, then BW is unlimited */ |
701 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { |
702 | if (wait) |
703 | *wait = 0; |
704 | return 1; |
705 | } |
706 | |
707 | /* |
708 | * If previous slice expired, start a new one otherwise renew/extend |
709 | * existing slice to make sure it is at least throtl_slice interval |
710 | * long since now. |
711 | */ |
712 | if (throtl_slice_used(td, tg, rw)) |
713 | throtl_start_new_slice(td, tg, rw); |
714 | else { |
715 | if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) |
716 | throtl_extend_slice(td, tg, rw, jiffies + throtl_slice); |
717 | } |
718 | |
719 | if (tg_with_in_bps_limit(td, tg, bio, &bps_wait) |
720 | && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) { |
721 | if (wait) |
722 | *wait = 0; |
723 | return 1; |
724 | } |
725 | |
726 | max_wait = max(bps_wait, iops_wait); |
727 | |
728 | if (wait) |
729 | *wait = max_wait; |
730 | |
731 | if (time_before(tg->slice_end[rw], jiffies + max_wait)) |
732 | throtl_extend_slice(td, tg, rw, jiffies + max_wait); |
733 | |
734 | return 0; |
735 | } |
736 | |
737 | static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) |
738 | { |
739 | bool rw = bio_data_dir(bio); |
740 | bool sync = rw_is_sync(bio->bi_rw); |
741 | |
742 | /* Charge the bio to the group */ |
743 | tg->bytes_disp[rw] += bio->bi_size; |
744 | tg->io_disp[rw]++; |
745 | |
746 | blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync); |
747 | } |
748 | |
749 | static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg, |
750 | struct bio *bio) |
751 | { |
752 | bool rw = bio_data_dir(bio); |
753 | |
754 | bio_list_add(&tg->bio_lists[rw], bio); |
755 | /* Take a bio reference on tg */ |
756 | throtl_ref_get_tg(tg); |
757 | tg->nr_queued[rw]++; |
758 | td->nr_queued[rw]++; |
759 | throtl_enqueue_tg(td, tg); |
760 | } |
761 | |
762 | static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg) |
763 | { |
764 | unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; |
765 | struct bio *bio; |
766 | |
767 | if ((bio = bio_list_peek(&tg->bio_lists[READ]))) |
768 | tg_may_dispatch(td, tg, bio, &read_wait); |
769 | |
770 | if ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) |
771 | tg_may_dispatch(td, tg, bio, &write_wait); |
772 | |
773 | min_wait = min(read_wait, write_wait); |
774 | disptime = jiffies + min_wait; |
775 | |
776 | /* Update dispatch time */ |
777 | throtl_dequeue_tg(td, tg); |
778 | tg->disptime = disptime; |
779 | throtl_enqueue_tg(td, tg); |
780 | } |
781 | |
782 | static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, |
783 | bool rw, struct bio_list *bl) |
784 | { |
785 | struct bio *bio; |
786 | |
787 | bio = bio_list_pop(&tg->bio_lists[rw]); |
788 | tg->nr_queued[rw]--; |
789 | /* Drop bio reference on tg */ |
790 | throtl_put_tg(tg); |
791 | |
792 | BUG_ON(td->nr_queued[rw] <= 0); |
793 | td->nr_queued[rw]--; |
794 | |
795 | throtl_charge_bio(tg, bio); |
796 | bio_list_add(bl, bio); |
797 | bio->bi_rw |= REQ_THROTTLED; |
798 | |
799 | throtl_trim_slice(td, tg, rw); |
800 | } |
801 | |
802 | static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, |
803 | struct bio_list *bl) |
804 | { |
805 | unsigned int nr_reads = 0, nr_writes = 0; |
806 | unsigned int max_nr_reads = throtl_grp_quantum*3/4; |
807 | unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; |
808 | struct bio *bio; |
809 | |
810 | /* Try to dispatch 75% READS and 25% WRITES */ |
811 | |
812 | while ((bio = bio_list_peek(&tg->bio_lists[READ])) |
813 | && tg_may_dispatch(td, tg, bio, NULL)) { |
814 | |
815 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); |
816 | nr_reads++; |
817 | |
818 | if (nr_reads >= max_nr_reads) |
819 | break; |
820 | } |
821 | |
822 | while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) |
823 | && tg_may_dispatch(td, tg, bio, NULL)) { |
824 | |
825 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); |
826 | nr_writes++; |
827 | |
828 | if (nr_writes >= max_nr_writes) |
829 | break; |
830 | } |
831 | |
832 | return nr_reads + nr_writes; |
833 | } |
834 | |
835 | static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) |
836 | { |
837 | unsigned int nr_disp = 0; |
838 | struct throtl_grp *tg; |
839 | struct throtl_rb_root *st = &td->tg_service_tree; |
840 | |
841 | while (1) { |
842 | tg = throtl_rb_first(st); |
843 | |
844 | if (!tg) |
845 | break; |
846 | |
847 | if (time_before(jiffies, tg->disptime)) |
848 | break; |
849 | |
850 | throtl_dequeue_tg(td, tg); |
851 | |
852 | nr_disp += throtl_dispatch_tg(td, tg, bl); |
853 | |
854 | if (tg->nr_queued[0] || tg->nr_queued[1]) { |
855 | tg_update_disptime(td, tg); |
856 | throtl_enqueue_tg(td, tg); |
857 | } |
858 | |
859 | if (nr_disp >= throtl_quantum) |
860 | break; |
861 | } |
862 | |
863 | return nr_disp; |
864 | } |
865 | |
866 | static void throtl_process_limit_change(struct throtl_data *td) |
867 | { |
868 | struct throtl_grp *tg; |
869 | struct hlist_node *pos, *n; |
870 | |
871 | if (!td->limits_changed) |
872 | return; |
873 | |
874 | xchg(&td->limits_changed, false); |
875 | |
876 | throtl_log(td, "limits changed"); |
877 | |
878 | hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { |
879 | if (!tg->limits_changed) |
880 | continue; |
881 | |
882 | if (!xchg(&tg->limits_changed, false)) |
883 | continue; |
884 | |
885 | throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu" |
886 | " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE], |
887 | tg->iops[READ], tg->iops[WRITE]); |
888 | |
889 | /* |
890 | * Restart the slices for both READ and WRITES. It |
891 | * might happen that a group's limit are dropped |
892 | * suddenly and we don't want to account recently |
893 | * dispatched IO with new low rate |
894 | */ |
895 | throtl_start_new_slice(td, tg, 0); |
896 | throtl_start_new_slice(td, tg, 1); |
897 | |
898 | if (throtl_tg_on_rr(tg)) |
899 | tg_update_disptime(td, tg); |
900 | } |
901 | } |
902 | |
903 | /* Dispatch throttled bios. Should be called without queue lock held. */ |
904 | static int throtl_dispatch(struct request_queue *q) |
905 | { |
906 | struct throtl_data *td = q->td; |
907 | unsigned int nr_disp = 0; |
908 | struct bio_list bio_list_on_stack; |
909 | struct bio *bio; |
910 | struct blk_plug plug; |
911 | |
912 | spin_lock_irq(q->queue_lock); |
913 | |
914 | throtl_process_limit_change(td); |
915 | |
916 | if (!total_nr_queued(td)) |
917 | goto out; |
918 | |
919 | bio_list_init(&bio_list_on_stack); |
920 | |
921 | throtl_log(td, "dispatch nr_queued=%u read=%u write=%u", |
922 | total_nr_queued(td), td->nr_queued[READ], |
923 | td->nr_queued[WRITE]); |
924 | |
925 | nr_disp = throtl_select_dispatch(td, &bio_list_on_stack); |
926 | |
927 | if (nr_disp) |
928 | throtl_log(td, "bios disp=%u", nr_disp); |
929 | |
930 | throtl_schedule_next_dispatch(td); |
931 | out: |
932 | spin_unlock_irq(q->queue_lock); |
933 | |
934 | /* |
935 | * If we dispatched some requests, unplug the queue to make sure |
936 | * immediate dispatch |
937 | */ |
938 | if (nr_disp) { |
939 | blk_start_plug(&plug); |
940 | while((bio = bio_list_pop(&bio_list_on_stack))) |
941 | generic_make_request(bio); |
942 | blk_finish_plug(&plug); |
943 | } |
944 | return nr_disp; |
945 | } |
946 | |
947 | void blk_throtl_work(struct work_struct *work) |
948 | { |
949 | struct throtl_data *td = container_of(work, struct throtl_data, |
950 | throtl_work.work); |
951 | struct request_queue *q = td->queue; |
952 | |
953 | throtl_dispatch(q); |
954 | } |
955 | |
956 | /* Call with queue lock held */ |
957 | static void |
958 | throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay) |
959 | { |
960 | |
961 | struct delayed_work *dwork = &td->throtl_work; |
962 | |
963 | /* schedule work if limits changed even if no bio is queued */ |
964 | if (total_nr_queued(td) || td->limits_changed) { |
965 | /* |
966 | * We might have a work scheduled to be executed in future. |
967 | * Cancel that and schedule a new one. |
968 | */ |
969 | __cancel_delayed_work(dwork); |
970 | queue_delayed_work(kthrotld_workqueue, dwork, delay); |
971 | throtl_log(td, "schedule work. delay=%lu jiffies=%lu", |
972 | delay, jiffies); |
973 | } |
974 | } |
975 | |
976 | static void |
977 | throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg) |
978 | { |
979 | /* Something wrong if we are trying to remove same group twice */ |
980 | BUG_ON(hlist_unhashed(&tg->tg_node)); |
981 | |
982 | hlist_del_init(&tg->tg_node); |
983 | |
984 | /* |
985 | * Put the reference taken at the time of creation so that when all |
986 | * queues are gone, group can be destroyed. |
987 | */ |
988 | throtl_put_tg(tg); |
989 | td->nr_undestroyed_grps--; |
990 | } |
991 | |
992 | static void throtl_release_tgs(struct throtl_data *td) |
993 | { |
994 | struct hlist_node *pos, *n; |
995 | struct throtl_grp *tg; |
996 | |
997 | hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { |
998 | /* |
999 | * If cgroup removal path got to blk_group first and removed |
1000 | * it from cgroup list, then it will take care of destroying |
1001 | * cfqg also. |
1002 | */ |
1003 | if (!blkiocg_del_blkio_group(&tg->blkg)) |
1004 | throtl_destroy_tg(td, tg); |
1005 | } |
1006 | } |
1007 | |
1008 | /* |
1009 | * Blk cgroup controller notification saying that blkio_group object is being |
1010 | * delinked as associated cgroup object is going away. That also means that |
1011 | * no new IO will come in this group. So get rid of this group as soon as |
1012 | * any pending IO in the group is finished. |
1013 | * |
1014 | * This function is called under rcu_read_lock(). key is the rcu protected |
1015 | * pointer. That means "key" is a valid throtl_data pointer as long as we are |
1016 | * rcu read lock. |
1017 | * |
1018 | * "key" was fetched from blkio_group under blkio_cgroup->lock. That means |
1019 | * it should not be NULL as even if queue was going away, cgroup deltion |
1020 | * path got to it first. |
1021 | */ |
1022 | void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg) |
1023 | { |
1024 | unsigned long flags; |
1025 | struct throtl_data *td = key; |
1026 | |
1027 | spin_lock_irqsave(td->queue->queue_lock, flags); |
1028 | throtl_destroy_tg(td, tg_of_blkg(blkg)); |
1029 | spin_unlock_irqrestore(td->queue->queue_lock, flags); |
1030 | } |
1031 | |
1032 | static void throtl_update_blkio_group_common(struct throtl_data *td, |
1033 | struct throtl_grp *tg) |
1034 | { |
1035 | xchg(&tg->limits_changed, true); |
1036 | xchg(&td->limits_changed, true); |
1037 | /* Schedule a work now to process the limit change */ |
1038 | throtl_schedule_delayed_work(td, 0); |
1039 | } |
1040 | |
1041 | /* |
1042 | * For all update functions, key should be a valid pointer because these |
1043 | * update functions are called under blkcg_lock, that means, blkg is |
1044 | * valid and in turn key is valid. queue exit path can not race because |
1045 | * of blkcg_lock |
1046 | * |
1047 | * Can not take queue lock in update functions as queue lock under blkcg_lock |
1048 | * is not allowed. Under other paths we take blkcg_lock under queue_lock. |
1049 | */ |
1050 | static void throtl_update_blkio_group_read_bps(void *key, |
1051 | struct blkio_group *blkg, u64 read_bps) |
1052 | { |
1053 | struct throtl_data *td = key; |
1054 | struct throtl_grp *tg = tg_of_blkg(blkg); |
1055 | |
1056 | tg->bps[READ] = read_bps; |
1057 | throtl_update_blkio_group_common(td, tg); |
1058 | } |
1059 | |
1060 | static void throtl_update_blkio_group_write_bps(void *key, |
1061 | struct blkio_group *blkg, u64 write_bps) |
1062 | { |
1063 | struct throtl_data *td = key; |
1064 | struct throtl_grp *tg = tg_of_blkg(blkg); |
1065 | |
1066 | tg->bps[WRITE] = write_bps; |
1067 | throtl_update_blkio_group_common(td, tg); |
1068 | } |
1069 | |
1070 | static void throtl_update_blkio_group_read_iops(void *key, |
1071 | struct blkio_group *blkg, unsigned int read_iops) |
1072 | { |
1073 | struct throtl_data *td = key; |
1074 | struct throtl_grp *tg = tg_of_blkg(blkg); |
1075 | |
1076 | tg->iops[READ] = read_iops; |
1077 | throtl_update_blkio_group_common(td, tg); |
1078 | } |
1079 | |
1080 | static void throtl_update_blkio_group_write_iops(void *key, |
1081 | struct blkio_group *blkg, unsigned int write_iops) |
1082 | { |
1083 | struct throtl_data *td = key; |
1084 | struct throtl_grp *tg = tg_of_blkg(blkg); |
1085 | |
1086 | tg->iops[WRITE] = write_iops; |
1087 | throtl_update_blkio_group_common(td, tg); |
1088 | } |
1089 | |
1090 | static void throtl_shutdown_wq(struct request_queue *q) |
1091 | { |
1092 | struct throtl_data *td = q->td; |
1093 | |
1094 | cancel_delayed_work_sync(&td->throtl_work); |
1095 | } |
1096 | |
1097 | static struct blkio_policy_type blkio_policy_throtl = { |
1098 | .ops = { |
1099 | .blkio_unlink_group_fn = throtl_unlink_blkio_group, |
1100 | .blkio_update_group_read_bps_fn = |
1101 | throtl_update_blkio_group_read_bps, |
1102 | .blkio_update_group_write_bps_fn = |
1103 | throtl_update_blkio_group_write_bps, |
1104 | .blkio_update_group_read_iops_fn = |
1105 | throtl_update_blkio_group_read_iops, |
1106 | .blkio_update_group_write_iops_fn = |
1107 | throtl_update_blkio_group_write_iops, |
1108 | }, |
1109 | .plid = BLKIO_POLICY_THROTL, |
1110 | }; |
1111 | |
1112 | bool blk_throtl_bio(struct request_queue *q, struct bio *bio) |
1113 | { |
1114 | struct throtl_data *td = q->td; |
1115 | struct throtl_grp *tg; |
1116 | bool rw = bio_data_dir(bio), update_disptime = true; |
1117 | struct blkio_cgroup *blkcg; |
1118 | bool throttled = false; |
1119 | |
1120 | if (bio->bi_rw & REQ_THROTTLED) { |
1121 | bio->bi_rw &= ~REQ_THROTTLED; |
1122 | goto out; |
1123 | } |
1124 | |
1125 | /* |
1126 | * A throtl_grp pointer retrieved under rcu can be used to access |
1127 | * basic fields like stats and io rates. If a group has no rules, |
1128 | * just update the dispatch stats in lockless manner and return. |
1129 | */ |
1130 | |
1131 | rcu_read_lock(); |
1132 | blkcg = task_blkio_cgroup(current); |
1133 | tg = throtl_find_tg(td, blkcg); |
1134 | if (tg) { |
1135 | throtl_tg_fill_dev_details(td, tg); |
1136 | |
1137 | if (tg_no_rule_group(tg, rw)) { |
1138 | blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, |
1139 | rw, rw_is_sync(bio->bi_rw)); |
1140 | rcu_read_unlock(); |
1141 | goto out; |
1142 | } |
1143 | } |
1144 | rcu_read_unlock(); |
1145 | |
1146 | /* |
1147 | * Either group has not been allocated yet or it is not an unlimited |
1148 | * IO group |
1149 | */ |
1150 | spin_lock_irq(q->queue_lock); |
1151 | tg = throtl_get_tg(td); |
1152 | if (unlikely(!tg)) |
1153 | goto out_unlock; |
1154 | |
1155 | if (tg->nr_queued[rw]) { |
1156 | /* |
1157 | * There is already another bio queued in same dir. No |
1158 | * need to update dispatch time. |
1159 | */ |
1160 | update_disptime = false; |
1161 | goto queue_bio; |
1162 | |
1163 | } |
1164 | |
1165 | /* Bio is with-in rate limit of group */ |
1166 | if (tg_may_dispatch(td, tg, bio, NULL)) { |
1167 | throtl_charge_bio(tg, bio); |
1168 | |
1169 | /* |
1170 | * We need to trim slice even when bios are not being queued |
1171 | * otherwise it might happen that a bio is not queued for |
1172 | * a long time and slice keeps on extending and trim is not |
1173 | * called for a long time. Now if limits are reduced suddenly |
1174 | * we take into account all the IO dispatched so far at new |
1175 | * low rate and * newly queued IO gets a really long dispatch |
1176 | * time. |
1177 | * |
1178 | * So keep on trimming slice even if bio is not queued. |
1179 | */ |
1180 | throtl_trim_slice(td, tg, rw); |
1181 | goto out_unlock; |
1182 | } |
1183 | |
1184 | queue_bio: |
1185 | throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu" |
1186 | " iodisp=%u iops=%u queued=%d/%d", |
1187 | rw == READ ? 'R' : 'W', |
1188 | tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], |
1189 | tg->io_disp[rw], tg->iops[rw], |
1190 | tg->nr_queued[READ], tg->nr_queued[WRITE]); |
1191 | |
1192 | throtl_add_bio_tg(q->td, tg, bio); |
1193 | throttled = true; |
1194 | |
1195 | if (update_disptime) { |
1196 | tg_update_disptime(td, tg); |
1197 | throtl_schedule_next_dispatch(td); |
1198 | } |
1199 | |
1200 | out_unlock: |
1201 | spin_unlock_irq(q->queue_lock); |
1202 | out: |
1203 | return throttled; |
1204 | } |
1205 | |
1206 | /** |
1207 | * blk_throtl_drain - drain throttled bios |
1208 | * @q: request_queue to drain throttled bios for |
1209 | * |
1210 | * Dispatch all currently throttled bios on @q through ->make_request_fn(). |
1211 | */ |
1212 | void blk_throtl_drain(struct request_queue *q) |
1213 | __releases(q->queue_lock) __acquires(q->queue_lock) |
1214 | { |
1215 | struct throtl_data *td = q->td; |
1216 | struct throtl_rb_root *st = &td->tg_service_tree; |
1217 | struct throtl_grp *tg; |
1218 | struct bio_list bl; |
1219 | struct bio *bio; |
1220 | |
1221 | WARN_ON_ONCE(!queue_is_locked(q)); |
1222 | |
1223 | bio_list_init(&bl); |
1224 | |
1225 | while ((tg = throtl_rb_first(st))) { |
1226 | throtl_dequeue_tg(td, tg); |
1227 | |
1228 | while ((bio = bio_list_peek(&tg->bio_lists[READ]))) |
1229 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl); |
1230 | while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) |
1231 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl); |
1232 | } |
1233 | spin_unlock_irq(q->queue_lock); |
1234 | |
1235 | while ((bio = bio_list_pop(&bl))) |
1236 | generic_make_request(bio); |
1237 | |
1238 | spin_lock_irq(q->queue_lock); |
1239 | } |
1240 | |
1241 | int blk_throtl_init(struct request_queue *q) |
1242 | { |
1243 | struct throtl_data *td; |
1244 | struct throtl_grp *tg; |
1245 | |
1246 | td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); |
1247 | if (!td) |
1248 | return -ENOMEM; |
1249 | |
1250 | INIT_HLIST_HEAD(&td->tg_list); |
1251 | td->tg_service_tree = THROTL_RB_ROOT; |
1252 | td->limits_changed = false; |
1253 | INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work); |
1254 | |
1255 | /* alloc and Init root group. */ |
1256 | td->queue = q; |
1257 | tg = throtl_alloc_tg(td); |
1258 | |
1259 | if (!tg) { |
1260 | kfree(td); |
1261 | return -ENOMEM; |
1262 | } |
1263 | |
1264 | td->root_tg = tg; |
1265 | |
1266 | rcu_read_lock(); |
1267 | throtl_init_add_tg_lists(td, tg, &blkio_root_cgroup); |
1268 | rcu_read_unlock(); |
1269 | |
1270 | /* Attach throtl data to request queue */ |
1271 | q->td = td; |
1272 | return 0; |
1273 | } |
1274 | |
1275 | void blk_throtl_exit(struct request_queue *q) |
1276 | { |
1277 | struct throtl_data *td = q->td; |
1278 | bool wait = false; |
1279 | |
1280 | BUG_ON(!td); |
1281 | |
1282 | throtl_shutdown_wq(q); |
1283 | |
1284 | spin_lock_irq(q->queue_lock); |
1285 | throtl_release_tgs(td); |
1286 | |
1287 | /* If there are other groups */ |
1288 | if (td->nr_undestroyed_grps > 0) |
1289 | wait = true; |
1290 | |
1291 | spin_unlock_irq(q->queue_lock); |
1292 | |
1293 | /* |
1294 | * Wait for tg->blkg->key accessors to exit their grace periods. |
1295 | * Do this wait only if there are other undestroyed groups out |
1296 | * there (other than root group). This can happen if cgroup deletion |
1297 | * path claimed the responsibility of cleaning up a group before |
1298 | * queue cleanup code get to the group. |
1299 | * |
1300 | * Do not call synchronize_rcu() unconditionally as there are drivers |
1301 | * which create/delete request queue hundreds of times during scan/boot |
1302 | * and synchronize_rcu() can take significant time and slow down boot. |
1303 | */ |
1304 | if (wait) |
1305 | synchronize_rcu(); |
1306 | |
1307 | /* |
1308 | * Just being safe to make sure after previous flush if some body did |
1309 | * update limits through cgroup and another work got queued, cancel |
1310 | * it. |
1311 | */ |
1312 | throtl_shutdown_wq(q); |
1313 | } |
1314 | |
1315 | void blk_throtl_release(struct request_queue *q) |
1316 | { |
1317 | kfree(q->td); |
1318 | } |
1319 | |
1320 | static int __init throtl_init(void) |
1321 | { |
1322 | kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); |
1323 | if (!kthrotld_workqueue) |
1324 | panic("Failed to create kthrotld\n"); |
1325 | |
1326 | blkio_policy_register(&blkio_policy_throtl); |
1327 | return 0; |
1328 | } |
1329 | |
1330 | module_init(throtl_init); |
1331 |
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Tags:
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v2.6.34-rc5
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