Commit | Line | Data |
---|---|---|
e43473b7 VG |
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 | ||
14 | /* Max dispatch from a group in 1 round */ | |
15 | static int throtl_grp_quantum = 8; | |
16 | ||
17 | /* Total max dispatch from all groups in one round */ | |
18 | static int throtl_quantum = 32; | |
19 | ||
20 | /* Throttling is performed over 100ms slice and after that slice is renewed */ | |
21 | static unsigned long throtl_slice = HZ/10; /* 100 ms */ | |
22 | ||
450adcbe VG |
23 | /* A workqueue to queue throttle related work */ |
24 | static struct workqueue_struct *kthrotld_workqueue; | |
25 | static void throtl_schedule_delayed_work(struct throtl_data *td, | |
26 | unsigned long delay); | |
27 | ||
e43473b7 VG |
28 | struct throtl_rb_root { |
29 | struct rb_root rb; | |
30 | struct rb_node *left; | |
31 | unsigned int count; | |
32 | unsigned long min_disptime; | |
33 | }; | |
34 | ||
35 | #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \ | |
36 | .count = 0, .min_disptime = 0} | |
37 | ||
38 | #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) | |
39 | ||
40 | struct throtl_grp { | |
41 | /* List of throtl groups on the request queue*/ | |
42 | struct hlist_node tg_node; | |
43 | ||
44 | /* active throtl group service_tree member */ | |
45 | struct rb_node rb_node; | |
46 | ||
47 | /* | |
48 | * Dispatch time in jiffies. This is the estimated time when group | |
49 | * will unthrottle and is ready to dispatch more bio. It is used as | |
50 | * key to sort active groups in service tree. | |
51 | */ | |
52 | unsigned long disptime; | |
53 | ||
54 | struct blkio_group blkg; | |
55 | atomic_t ref; | |
56 | unsigned int flags; | |
57 | ||
58 | /* Two lists for READ and WRITE */ | |
59 | struct bio_list bio_lists[2]; | |
60 | ||
61 | /* Number of queued bios on READ and WRITE lists */ | |
62 | unsigned int nr_queued[2]; | |
63 | ||
64 | /* bytes per second rate limits */ | |
65 | uint64_t bps[2]; | |
66 | ||
8e89d13f VG |
67 | /* IOPS limits */ |
68 | unsigned int iops[2]; | |
69 | ||
e43473b7 VG |
70 | /* Number of bytes disptached in current slice */ |
71 | uint64_t bytes_disp[2]; | |
8e89d13f VG |
72 | /* Number of bio's dispatched in current slice */ |
73 | unsigned int io_disp[2]; | |
e43473b7 VG |
74 | |
75 | /* When did we start a new slice */ | |
76 | unsigned long slice_start[2]; | |
77 | unsigned long slice_end[2]; | |
fe071437 VG |
78 | |
79 | /* Some throttle limits got updated for the group */ | |
6f037937 | 80 | int limits_changed; |
e43473b7 VG |
81 | }; |
82 | ||
83 | struct throtl_data | |
84 | { | |
85 | /* List of throtl groups */ | |
86 | struct hlist_head tg_list; | |
87 | ||
88 | /* service tree for active throtl groups */ | |
89 | struct throtl_rb_root tg_service_tree; | |
90 | ||
91 | struct throtl_grp root_tg; | |
92 | struct request_queue *queue; | |
93 | ||
94 | /* Total Number of queued bios on READ and WRITE lists */ | |
95 | unsigned int nr_queued[2]; | |
96 | ||
97 | /* | |
02977e4a | 98 | * number of total undestroyed groups |
e43473b7 VG |
99 | */ |
100 | unsigned int nr_undestroyed_grps; | |
101 | ||
102 | /* Work for dispatching throttled bios */ | |
103 | struct delayed_work throtl_work; | |
fe071437 | 104 | |
6f037937 | 105 | int limits_changed; |
e43473b7 VG |
106 | }; |
107 | ||
108 | enum tg_state_flags { | |
109 | THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */ | |
110 | }; | |
111 | ||
112 | #define THROTL_TG_FNS(name) \ | |
113 | static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \ | |
114 | { \ | |
115 | (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \ | |
116 | } \ | |
117 | static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \ | |
118 | { \ | |
119 | (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \ | |
120 | } \ | |
121 | static inline int throtl_tg_##name(const struct throtl_grp *tg) \ | |
122 | { \ | |
123 | return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \ | |
124 | } | |
125 | ||
126 | THROTL_TG_FNS(on_rr); | |
127 | ||
128 | #define throtl_log_tg(td, tg, fmt, args...) \ | |
129 | blk_add_trace_msg((td)->queue, "throtl %s " fmt, \ | |
130 | blkg_path(&(tg)->blkg), ##args); \ | |
131 | ||
132 | #define throtl_log(td, fmt, args...) \ | |
133 | blk_add_trace_msg((td)->queue, "throtl " fmt, ##args) | |
134 | ||
135 | static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg) | |
136 | { | |
137 | if (blkg) | |
138 | return container_of(blkg, struct throtl_grp, blkg); | |
139 | ||
140 | return NULL; | |
141 | } | |
142 | ||
143 | static inline int total_nr_queued(struct throtl_data *td) | |
144 | { | |
145 | return (td->nr_queued[0] + td->nr_queued[1]); | |
146 | } | |
147 | ||
148 | static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg) | |
149 | { | |
150 | atomic_inc(&tg->ref); | |
151 | return tg; | |
152 | } | |
153 | ||
154 | static void throtl_put_tg(struct throtl_grp *tg) | |
155 | { | |
156 | BUG_ON(atomic_read(&tg->ref) <= 0); | |
157 | if (!atomic_dec_and_test(&tg->ref)) | |
158 | return; | |
159 | kfree(tg); | |
160 | } | |
161 | ||
162 | static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td, | |
70087dc3 | 163 | struct blkio_cgroup *blkcg) |
e43473b7 | 164 | { |
e43473b7 VG |
165 | struct throtl_grp *tg = NULL; |
166 | void *key = td; | |
167 | struct backing_dev_info *bdi = &td->queue->backing_dev_info; | |
168 | unsigned int major, minor; | |
169 | ||
170 | /* | |
171 | * TODO: Speed up blkiocg_lookup_group() by maintaining a radix | |
172 | * tree of blkg (instead of traversing through hash list all | |
173 | * the time. | |
174 | */ | |
be2c6b19 VG |
175 | |
176 | /* | |
177 | * This is the common case when there are no blkio cgroups. | |
178 | * Avoid lookup in this case | |
179 | */ | |
180 | if (blkcg == &blkio_root_cgroup) | |
181 | tg = &td->root_tg; | |
182 | else | |
183 | tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key)); | |
e43473b7 VG |
184 | |
185 | /* Fill in device details for root group */ | |
186 | if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) { | |
187 | sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); | |
188 | tg->blkg.dev = MKDEV(major, minor); | |
189 | goto done; | |
190 | } | |
191 | ||
192 | if (tg) | |
193 | goto done; | |
194 | ||
195 | tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node); | |
196 | if (!tg) | |
197 | goto done; | |
198 | ||
199 | INIT_HLIST_NODE(&tg->tg_node); | |
200 | RB_CLEAR_NODE(&tg->rb_node); | |
201 | bio_list_init(&tg->bio_lists[0]); | |
202 | bio_list_init(&tg->bio_lists[1]); | |
de701c74 | 203 | td->limits_changed = false; |
e43473b7 VG |
204 | |
205 | /* | |
206 | * Take the initial reference that will be released on destroy | |
207 | * This can be thought of a joint reference by cgroup and | |
208 | * request queue which will be dropped by either request queue | |
209 | * exit or cgroup deletion path depending on who is exiting first. | |
210 | */ | |
211 | atomic_set(&tg->ref, 1); | |
212 | ||
213 | /* Add group onto cgroup list */ | |
214 | sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); | |
215 | blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td, | |
216 | MKDEV(major, minor), BLKIO_POLICY_THROTL); | |
217 | ||
218 | tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev); | |
219 | tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev); | |
8e89d13f VG |
220 | tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev); |
221 | tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev); | |
e43473b7 VG |
222 | |
223 | hlist_add_head(&tg->tg_node, &td->tg_list); | |
224 | td->nr_undestroyed_grps++; | |
225 | done: | |
226 | return tg; | |
227 | } | |
228 | ||
229 | static struct throtl_grp * throtl_get_tg(struct throtl_data *td) | |
230 | { | |
e43473b7 | 231 | struct throtl_grp *tg = NULL; |
70087dc3 | 232 | struct blkio_cgroup *blkcg; |
e43473b7 VG |
233 | |
234 | rcu_read_lock(); | |
70087dc3 VG |
235 | blkcg = task_blkio_cgroup(current); |
236 | tg = throtl_find_alloc_tg(td, blkcg); | |
e43473b7 VG |
237 | if (!tg) |
238 | tg = &td->root_tg; | |
239 | rcu_read_unlock(); | |
240 | return tg; | |
241 | } | |
242 | ||
243 | static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root) | |
244 | { | |
245 | /* Service tree is empty */ | |
246 | if (!root->count) | |
247 | return NULL; | |
248 | ||
249 | if (!root->left) | |
250 | root->left = rb_first(&root->rb); | |
251 | ||
252 | if (root->left) | |
253 | return rb_entry_tg(root->left); | |
254 | ||
255 | return NULL; | |
256 | } | |
257 | ||
258 | static void rb_erase_init(struct rb_node *n, struct rb_root *root) | |
259 | { | |
260 | rb_erase(n, root); | |
261 | RB_CLEAR_NODE(n); | |
262 | } | |
263 | ||
264 | static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root) | |
265 | { | |
266 | if (root->left == n) | |
267 | root->left = NULL; | |
268 | rb_erase_init(n, &root->rb); | |
269 | --root->count; | |
270 | } | |
271 | ||
272 | static void update_min_dispatch_time(struct throtl_rb_root *st) | |
273 | { | |
274 | struct throtl_grp *tg; | |
275 | ||
276 | tg = throtl_rb_first(st); | |
277 | if (!tg) | |
278 | return; | |
279 | ||
280 | st->min_disptime = tg->disptime; | |
281 | } | |
282 | ||
283 | static void | |
284 | tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) | |
285 | { | |
286 | struct rb_node **node = &st->rb.rb_node; | |
287 | struct rb_node *parent = NULL; | |
288 | struct throtl_grp *__tg; | |
289 | unsigned long key = tg->disptime; | |
290 | int left = 1; | |
291 | ||
292 | while (*node != NULL) { | |
293 | parent = *node; | |
294 | __tg = rb_entry_tg(parent); | |
295 | ||
296 | if (time_before(key, __tg->disptime)) | |
297 | node = &parent->rb_left; | |
298 | else { | |
299 | node = &parent->rb_right; | |
300 | left = 0; | |
301 | } | |
302 | } | |
303 | ||
304 | if (left) | |
305 | st->left = &tg->rb_node; | |
306 | ||
307 | rb_link_node(&tg->rb_node, parent, node); | |
308 | rb_insert_color(&tg->rb_node, &st->rb); | |
309 | } | |
310 | ||
311 | static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
312 | { | |
313 | struct throtl_rb_root *st = &td->tg_service_tree; | |
314 | ||
315 | tg_service_tree_add(st, tg); | |
316 | throtl_mark_tg_on_rr(tg); | |
317 | st->count++; | |
318 | } | |
319 | ||
320 | static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
321 | { | |
322 | if (!throtl_tg_on_rr(tg)) | |
323 | __throtl_enqueue_tg(td, tg); | |
324 | } | |
325 | ||
326 | static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
327 | { | |
328 | throtl_rb_erase(&tg->rb_node, &td->tg_service_tree); | |
329 | throtl_clear_tg_on_rr(tg); | |
330 | } | |
331 | ||
332 | static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
333 | { | |
334 | if (throtl_tg_on_rr(tg)) | |
335 | __throtl_dequeue_tg(td, tg); | |
336 | } | |
337 | ||
338 | static void throtl_schedule_next_dispatch(struct throtl_data *td) | |
339 | { | |
340 | struct throtl_rb_root *st = &td->tg_service_tree; | |
341 | ||
342 | /* | |
343 | * If there are more bios pending, schedule more work. | |
344 | */ | |
345 | if (!total_nr_queued(td)) | |
346 | return; | |
347 | ||
348 | BUG_ON(!st->count); | |
349 | ||
350 | update_min_dispatch_time(st); | |
351 | ||
352 | if (time_before_eq(st->min_disptime, jiffies)) | |
450adcbe | 353 | throtl_schedule_delayed_work(td, 0); |
e43473b7 | 354 | else |
450adcbe | 355 | throtl_schedule_delayed_work(td, (st->min_disptime - jiffies)); |
e43473b7 VG |
356 | } |
357 | ||
358 | static inline void | |
359 | throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) | |
360 | { | |
361 | tg->bytes_disp[rw] = 0; | |
8e89d13f | 362 | tg->io_disp[rw] = 0; |
e43473b7 VG |
363 | tg->slice_start[rw] = jiffies; |
364 | tg->slice_end[rw] = jiffies + throtl_slice; | |
365 | throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu", | |
366 | rw == READ ? 'R' : 'W', tg->slice_start[rw], | |
367 | tg->slice_end[rw], jiffies); | |
368 | } | |
369 | ||
d1ae8ffd VG |
370 | static inline void throtl_set_slice_end(struct throtl_data *td, |
371 | struct throtl_grp *tg, bool rw, unsigned long jiffy_end) | |
372 | { | |
373 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); | |
374 | } | |
375 | ||
e43473b7 VG |
376 | static inline void throtl_extend_slice(struct throtl_data *td, |
377 | struct throtl_grp *tg, bool rw, unsigned long jiffy_end) | |
378 | { | |
379 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); | |
380 | throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu", | |
381 | rw == READ ? 'R' : 'W', tg->slice_start[rw], | |
382 | tg->slice_end[rw], jiffies); | |
383 | } | |
384 | ||
385 | /* Determine if previously allocated or extended slice is complete or not */ | |
386 | static bool | |
387 | throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) | |
388 | { | |
389 | if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) | |
390 | return 0; | |
391 | ||
392 | return 1; | |
393 | } | |
394 | ||
395 | /* Trim the used slices and adjust slice start accordingly */ | |
396 | static inline void | |
397 | throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) | |
398 | { | |
3aad5d3e VG |
399 | unsigned long nr_slices, time_elapsed, io_trim; |
400 | u64 bytes_trim, tmp; | |
e43473b7 VG |
401 | |
402 | BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); | |
403 | ||
404 | /* | |
405 | * If bps are unlimited (-1), then time slice don't get | |
406 | * renewed. Don't try to trim the slice if slice is used. A new | |
407 | * slice will start when appropriate. | |
408 | */ | |
409 | if (throtl_slice_used(td, tg, rw)) | |
410 | return; | |
411 | ||
d1ae8ffd VG |
412 | /* |
413 | * A bio has been dispatched. Also adjust slice_end. It might happen | |
414 | * that initially cgroup limit was very low resulting in high | |
415 | * slice_end, but later limit was bumped up and bio was dispached | |
416 | * sooner, then we need to reduce slice_end. A high bogus slice_end | |
417 | * is bad because it does not allow new slice to start. | |
418 | */ | |
419 | ||
420 | throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice); | |
421 | ||
e43473b7 VG |
422 | time_elapsed = jiffies - tg->slice_start[rw]; |
423 | ||
424 | nr_slices = time_elapsed / throtl_slice; | |
425 | ||
426 | if (!nr_slices) | |
427 | return; | |
3aad5d3e VG |
428 | tmp = tg->bps[rw] * throtl_slice * nr_slices; |
429 | do_div(tmp, HZ); | |
430 | bytes_trim = tmp; | |
e43473b7 | 431 | |
8e89d13f | 432 | io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; |
e43473b7 | 433 | |
8e89d13f | 434 | if (!bytes_trim && !io_trim) |
e43473b7 VG |
435 | return; |
436 | ||
437 | if (tg->bytes_disp[rw] >= bytes_trim) | |
438 | tg->bytes_disp[rw] -= bytes_trim; | |
439 | else | |
440 | tg->bytes_disp[rw] = 0; | |
441 | ||
8e89d13f VG |
442 | if (tg->io_disp[rw] >= io_trim) |
443 | tg->io_disp[rw] -= io_trim; | |
444 | else | |
445 | tg->io_disp[rw] = 0; | |
446 | ||
e43473b7 VG |
447 | tg->slice_start[rw] += nr_slices * throtl_slice; |
448 | ||
3aad5d3e | 449 | throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu" |
e43473b7 | 450 | " start=%lu end=%lu jiffies=%lu", |
8e89d13f | 451 | rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, |
e43473b7 VG |
452 | tg->slice_start[rw], tg->slice_end[rw], jiffies); |
453 | } | |
454 | ||
8e89d13f VG |
455 | static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, |
456 | struct bio *bio, unsigned long *wait) | |
e43473b7 VG |
457 | { |
458 | bool rw = bio_data_dir(bio); | |
8e89d13f | 459 | unsigned int io_allowed; |
e43473b7 | 460 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
c49c06e4 | 461 | u64 tmp; |
e43473b7 | 462 | |
8e89d13f | 463 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
e43473b7 | 464 | |
8e89d13f VG |
465 | /* Slice has just started. Consider one slice interval */ |
466 | if (!jiffy_elapsed) | |
467 | jiffy_elapsed_rnd = throtl_slice; | |
468 | ||
469 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); | |
470 | ||
c49c06e4 VG |
471 | /* |
472 | * jiffy_elapsed_rnd should not be a big value as minimum iops can be | |
473 | * 1 then at max jiffy elapsed should be equivalent of 1 second as we | |
474 | * will allow dispatch after 1 second and after that slice should | |
475 | * have been trimmed. | |
476 | */ | |
477 | ||
478 | tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; | |
479 | do_div(tmp, HZ); | |
480 | ||
481 | if (tmp > UINT_MAX) | |
482 | io_allowed = UINT_MAX; | |
483 | else | |
484 | io_allowed = tmp; | |
8e89d13f VG |
485 | |
486 | if (tg->io_disp[rw] + 1 <= io_allowed) { | |
e43473b7 VG |
487 | if (wait) |
488 | *wait = 0; | |
489 | return 1; | |
490 | } | |
491 | ||
8e89d13f VG |
492 | /* Calc approx time to dispatch */ |
493 | jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; | |
494 | ||
495 | if (jiffy_wait > jiffy_elapsed) | |
496 | jiffy_wait = jiffy_wait - jiffy_elapsed; | |
497 | else | |
498 | jiffy_wait = 1; | |
499 | ||
500 | if (wait) | |
501 | *wait = jiffy_wait; | |
502 | return 0; | |
503 | } | |
504 | ||
505 | static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg, | |
506 | struct bio *bio, unsigned long *wait) | |
507 | { | |
508 | bool rw = bio_data_dir(bio); | |
3aad5d3e | 509 | u64 bytes_allowed, extra_bytes, tmp; |
8e89d13f | 510 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
e43473b7 VG |
511 | |
512 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; | |
513 | ||
514 | /* Slice has just started. Consider one slice interval */ | |
515 | if (!jiffy_elapsed) | |
516 | jiffy_elapsed_rnd = throtl_slice; | |
517 | ||
518 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); | |
519 | ||
5e901a2b VG |
520 | tmp = tg->bps[rw] * jiffy_elapsed_rnd; |
521 | do_div(tmp, HZ); | |
3aad5d3e | 522 | bytes_allowed = tmp; |
e43473b7 VG |
523 | |
524 | if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) { | |
525 | if (wait) | |
526 | *wait = 0; | |
527 | return 1; | |
528 | } | |
529 | ||
530 | /* Calc approx time to dispatch */ | |
531 | extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed; | |
532 | jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); | |
533 | ||
534 | if (!jiffy_wait) | |
535 | jiffy_wait = 1; | |
536 | ||
537 | /* | |
538 | * This wait time is without taking into consideration the rounding | |
539 | * up we did. Add that time also. | |
540 | */ | |
541 | jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); | |
e43473b7 VG |
542 | if (wait) |
543 | *wait = jiffy_wait; | |
8e89d13f VG |
544 | return 0; |
545 | } | |
546 | ||
547 | /* | |
548 | * Returns whether one can dispatch a bio or not. Also returns approx number | |
549 | * of jiffies to wait before this bio is with-in IO rate and can be dispatched | |
550 | */ | |
551 | static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, | |
552 | struct bio *bio, unsigned long *wait) | |
553 | { | |
554 | bool rw = bio_data_dir(bio); | |
555 | unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; | |
556 | ||
557 | /* | |
558 | * Currently whole state machine of group depends on first bio | |
559 | * queued in the group bio list. So one should not be calling | |
560 | * this function with a different bio if there are other bios | |
561 | * queued. | |
562 | */ | |
563 | BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw])); | |
e43473b7 | 564 | |
8e89d13f VG |
565 | /* If tg->bps = -1, then BW is unlimited */ |
566 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { | |
567 | if (wait) | |
568 | *wait = 0; | |
569 | return 1; | |
570 | } | |
571 | ||
572 | /* | |
573 | * If previous slice expired, start a new one otherwise renew/extend | |
574 | * existing slice to make sure it is at least throtl_slice interval | |
575 | * long since now. | |
576 | */ | |
577 | if (throtl_slice_used(td, tg, rw)) | |
578 | throtl_start_new_slice(td, tg, rw); | |
579 | else { | |
580 | if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) | |
581 | throtl_extend_slice(td, tg, rw, jiffies + throtl_slice); | |
582 | } | |
583 | ||
584 | if (tg_with_in_bps_limit(td, tg, bio, &bps_wait) | |
585 | && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) { | |
586 | if (wait) | |
587 | *wait = 0; | |
588 | return 1; | |
589 | } | |
590 | ||
591 | max_wait = max(bps_wait, iops_wait); | |
592 | ||
593 | if (wait) | |
594 | *wait = max_wait; | |
595 | ||
596 | if (time_before(tg->slice_end[rw], jiffies + max_wait)) | |
597 | throtl_extend_slice(td, tg, rw, jiffies + max_wait); | |
e43473b7 VG |
598 | |
599 | return 0; | |
600 | } | |
601 | ||
602 | static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) | |
603 | { | |
604 | bool rw = bio_data_dir(bio); | |
605 | bool sync = bio->bi_rw & REQ_SYNC; | |
606 | ||
607 | /* Charge the bio to the group */ | |
608 | tg->bytes_disp[rw] += bio->bi_size; | |
8e89d13f | 609 | tg->io_disp[rw]++; |
e43473b7 VG |
610 | |
611 | /* | |
612 | * TODO: This will take blkg->stats_lock. Figure out a way | |
613 | * to avoid this cost. | |
614 | */ | |
615 | blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync); | |
e43473b7 VG |
616 | } |
617 | ||
618 | static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg, | |
619 | struct bio *bio) | |
620 | { | |
621 | bool rw = bio_data_dir(bio); | |
622 | ||
623 | bio_list_add(&tg->bio_lists[rw], bio); | |
624 | /* Take a bio reference on tg */ | |
625 | throtl_ref_get_tg(tg); | |
626 | tg->nr_queued[rw]++; | |
627 | td->nr_queued[rw]++; | |
628 | throtl_enqueue_tg(td, tg); | |
629 | } | |
630 | ||
631 | static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg) | |
632 | { | |
633 | unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; | |
634 | struct bio *bio; | |
635 | ||
636 | if ((bio = bio_list_peek(&tg->bio_lists[READ]))) | |
637 | tg_may_dispatch(td, tg, bio, &read_wait); | |
638 | ||
639 | if ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) | |
640 | tg_may_dispatch(td, tg, bio, &write_wait); | |
641 | ||
642 | min_wait = min(read_wait, write_wait); | |
643 | disptime = jiffies + min_wait; | |
644 | ||
e43473b7 VG |
645 | /* Update dispatch time */ |
646 | throtl_dequeue_tg(td, tg); | |
647 | tg->disptime = disptime; | |
648 | throtl_enqueue_tg(td, tg); | |
649 | } | |
650 | ||
651 | static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, | |
652 | bool rw, struct bio_list *bl) | |
653 | { | |
654 | struct bio *bio; | |
655 | ||
656 | bio = bio_list_pop(&tg->bio_lists[rw]); | |
657 | tg->nr_queued[rw]--; | |
658 | /* Drop bio reference on tg */ | |
659 | throtl_put_tg(tg); | |
660 | ||
661 | BUG_ON(td->nr_queued[rw] <= 0); | |
662 | td->nr_queued[rw]--; | |
663 | ||
664 | throtl_charge_bio(tg, bio); | |
665 | bio_list_add(bl, bio); | |
666 | bio->bi_rw |= REQ_THROTTLED; | |
667 | ||
668 | throtl_trim_slice(td, tg, rw); | |
669 | } | |
670 | ||
671 | static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, | |
672 | struct bio_list *bl) | |
673 | { | |
674 | unsigned int nr_reads = 0, nr_writes = 0; | |
675 | unsigned int max_nr_reads = throtl_grp_quantum*3/4; | |
c2f6805d | 676 | unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; |
e43473b7 VG |
677 | struct bio *bio; |
678 | ||
679 | /* Try to dispatch 75% READS and 25% WRITES */ | |
680 | ||
681 | while ((bio = bio_list_peek(&tg->bio_lists[READ])) | |
682 | && tg_may_dispatch(td, tg, bio, NULL)) { | |
683 | ||
684 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); | |
685 | nr_reads++; | |
686 | ||
687 | if (nr_reads >= max_nr_reads) | |
688 | break; | |
689 | } | |
690 | ||
691 | while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) | |
692 | && tg_may_dispatch(td, tg, bio, NULL)) { | |
693 | ||
694 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); | |
695 | nr_writes++; | |
696 | ||
697 | if (nr_writes >= max_nr_writes) | |
698 | break; | |
699 | } | |
700 | ||
701 | return nr_reads + nr_writes; | |
702 | } | |
703 | ||
704 | static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) | |
705 | { | |
706 | unsigned int nr_disp = 0; | |
707 | struct throtl_grp *tg; | |
708 | struct throtl_rb_root *st = &td->tg_service_tree; | |
709 | ||
710 | while (1) { | |
711 | tg = throtl_rb_first(st); | |
712 | ||
713 | if (!tg) | |
714 | break; | |
715 | ||
716 | if (time_before(jiffies, tg->disptime)) | |
717 | break; | |
718 | ||
719 | throtl_dequeue_tg(td, tg); | |
720 | ||
721 | nr_disp += throtl_dispatch_tg(td, tg, bl); | |
722 | ||
723 | if (tg->nr_queued[0] || tg->nr_queued[1]) { | |
724 | tg_update_disptime(td, tg); | |
725 | throtl_enqueue_tg(td, tg); | |
726 | } | |
727 | ||
728 | if (nr_disp >= throtl_quantum) | |
729 | break; | |
730 | } | |
731 | ||
732 | return nr_disp; | |
733 | } | |
734 | ||
fe071437 VG |
735 | static void throtl_process_limit_change(struct throtl_data *td) |
736 | { | |
737 | struct throtl_grp *tg; | |
738 | struct hlist_node *pos, *n; | |
739 | ||
de701c74 | 740 | if (!td->limits_changed) |
fe071437 VG |
741 | return; |
742 | ||
de701c74 | 743 | xchg(&td->limits_changed, false); |
fe071437 | 744 | |
de701c74 | 745 | throtl_log(td, "limits changed"); |
fe071437 | 746 | |
04a6b516 | 747 | hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { |
de701c74 VG |
748 | if (!tg->limits_changed) |
749 | continue; | |
750 | ||
751 | if (!xchg(&tg->limits_changed, false)) | |
752 | continue; | |
753 | ||
754 | throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu" | |
755 | " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE], | |
756 | tg->iops[READ], tg->iops[WRITE]); | |
757 | ||
04521db0 VG |
758 | /* |
759 | * Restart the slices for both READ and WRITES. It | |
760 | * might happen that a group's limit are dropped | |
761 | * suddenly and we don't want to account recently | |
762 | * dispatched IO with new low rate | |
763 | */ | |
764 | throtl_start_new_slice(td, tg, 0); | |
765 | throtl_start_new_slice(td, tg, 1); | |
766 | ||
de701c74 | 767 | if (throtl_tg_on_rr(tg)) |
fe071437 | 768 | tg_update_disptime(td, tg); |
fe071437 | 769 | } |
fe071437 VG |
770 | } |
771 | ||
e43473b7 VG |
772 | /* Dispatch throttled bios. Should be called without queue lock held. */ |
773 | static int throtl_dispatch(struct request_queue *q) | |
774 | { | |
775 | struct throtl_data *td = q->td; | |
776 | unsigned int nr_disp = 0; | |
777 | struct bio_list bio_list_on_stack; | |
778 | struct bio *bio; | |
69d60eb9 | 779 | struct blk_plug plug; |
e43473b7 VG |
780 | |
781 | spin_lock_irq(q->queue_lock); | |
782 | ||
fe071437 VG |
783 | throtl_process_limit_change(td); |
784 | ||
e43473b7 VG |
785 | if (!total_nr_queued(td)) |
786 | goto out; | |
787 | ||
788 | bio_list_init(&bio_list_on_stack); | |
789 | ||
790 | throtl_log(td, "dispatch nr_queued=%lu read=%u write=%u", | |
791 | total_nr_queued(td), td->nr_queued[READ], | |
792 | td->nr_queued[WRITE]); | |
793 | ||
794 | nr_disp = throtl_select_dispatch(td, &bio_list_on_stack); | |
795 | ||
796 | if (nr_disp) | |
797 | throtl_log(td, "bios disp=%u", nr_disp); | |
798 | ||
799 | throtl_schedule_next_dispatch(td); | |
800 | out: | |
801 | spin_unlock_irq(q->queue_lock); | |
802 | ||
803 | /* | |
804 | * If we dispatched some requests, unplug the queue to make sure | |
805 | * immediate dispatch | |
806 | */ | |
807 | if (nr_disp) { | |
69d60eb9 | 808 | blk_start_plug(&plug); |
e43473b7 VG |
809 | while((bio = bio_list_pop(&bio_list_on_stack))) |
810 | generic_make_request(bio); | |
69d60eb9 | 811 | blk_finish_plug(&plug); |
e43473b7 VG |
812 | } |
813 | return nr_disp; | |
814 | } | |
815 | ||
816 | void blk_throtl_work(struct work_struct *work) | |
817 | { | |
818 | struct throtl_data *td = container_of(work, struct throtl_data, | |
819 | throtl_work.work); | |
820 | struct request_queue *q = td->queue; | |
821 | ||
822 | throtl_dispatch(q); | |
823 | } | |
824 | ||
825 | /* Call with queue lock held */ | |
450adcbe VG |
826 | static void |
827 | throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay) | |
e43473b7 VG |
828 | { |
829 | ||
e43473b7 VG |
830 | struct delayed_work *dwork = &td->throtl_work; |
831 | ||
04521db0 VG |
832 | /* schedule work if limits changed even if no bio is queued */ |
833 | if (total_nr_queued(td) > 0 || td->limits_changed) { | |
e43473b7 VG |
834 | /* |
835 | * We might have a work scheduled to be executed in future. | |
836 | * Cancel that and schedule a new one. | |
837 | */ | |
838 | __cancel_delayed_work(dwork); | |
450adcbe | 839 | queue_delayed_work(kthrotld_workqueue, dwork, delay); |
e43473b7 VG |
840 | throtl_log(td, "schedule work. delay=%lu jiffies=%lu", |
841 | delay, jiffies); | |
842 | } | |
843 | } | |
e43473b7 VG |
844 | |
845 | static void | |
846 | throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg) | |
847 | { | |
848 | /* Something wrong if we are trying to remove same group twice */ | |
849 | BUG_ON(hlist_unhashed(&tg->tg_node)); | |
850 | ||
851 | hlist_del_init(&tg->tg_node); | |
852 | ||
853 | /* | |
854 | * Put the reference taken at the time of creation so that when all | |
855 | * queues are gone, group can be destroyed. | |
856 | */ | |
857 | throtl_put_tg(tg); | |
858 | td->nr_undestroyed_grps--; | |
859 | } | |
860 | ||
861 | static void throtl_release_tgs(struct throtl_data *td) | |
862 | { | |
863 | struct hlist_node *pos, *n; | |
864 | struct throtl_grp *tg; | |
865 | ||
866 | hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { | |
867 | /* | |
868 | * If cgroup removal path got to blk_group first and removed | |
869 | * it from cgroup list, then it will take care of destroying | |
870 | * cfqg also. | |
871 | */ | |
872 | if (!blkiocg_del_blkio_group(&tg->blkg)) | |
873 | throtl_destroy_tg(td, tg); | |
874 | } | |
875 | } | |
876 | ||
877 | static void throtl_td_free(struct throtl_data *td) | |
878 | { | |
879 | kfree(td); | |
880 | } | |
881 | ||
882 | /* | |
883 | * Blk cgroup controller notification saying that blkio_group object is being | |
884 | * delinked as associated cgroup object is going away. That also means that | |
885 | * no new IO will come in this group. So get rid of this group as soon as | |
886 | * any pending IO in the group is finished. | |
887 | * | |
888 | * This function is called under rcu_read_lock(). key is the rcu protected | |
889 | * pointer. That means "key" is a valid throtl_data pointer as long as we are | |
890 | * rcu read lock. | |
891 | * | |
892 | * "key" was fetched from blkio_group under blkio_cgroup->lock. That means | |
893 | * it should not be NULL as even if queue was going away, cgroup deltion | |
894 | * path got to it first. | |
895 | */ | |
896 | void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg) | |
897 | { | |
898 | unsigned long flags; | |
899 | struct throtl_data *td = key; | |
900 | ||
901 | spin_lock_irqsave(td->queue->queue_lock, flags); | |
902 | throtl_destroy_tg(td, tg_of_blkg(blkg)); | |
903 | spin_unlock_irqrestore(td->queue->queue_lock, flags); | |
904 | } | |
905 | ||
de701c74 VG |
906 | static void throtl_update_blkio_group_common(struct throtl_data *td, |
907 | struct throtl_grp *tg) | |
908 | { | |
909 | xchg(&tg->limits_changed, true); | |
910 | xchg(&td->limits_changed, true); | |
911 | /* Schedule a work now to process the limit change */ | |
912 | throtl_schedule_delayed_work(td, 0); | |
913 | } | |
914 | ||
fe071437 VG |
915 | /* |
916 | * For all update functions, key should be a valid pointer because these | |
917 | * update functions are called under blkcg_lock, that means, blkg is | |
25985edc | 918 | * valid and in turn key is valid. queue exit path can not race because |
fe071437 VG |
919 | * of blkcg_lock |
920 | * | |
921 | * Can not take queue lock in update functions as queue lock under blkcg_lock | |
922 | * is not allowed. Under other paths we take blkcg_lock under queue_lock. | |
923 | */ | |
924 | static void throtl_update_blkio_group_read_bps(void *key, | |
925 | struct blkio_group *blkg, u64 read_bps) | |
e43473b7 | 926 | { |
fe071437 | 927 | struct throtl_data *td = key; |
de701c74 | 928 | struct throtl_grp *tg = tg_of_blkg(blkg); |
fe071437 | 929 | |
de701c74 VG |
930 | tg->bps[READ] = read_bps; |
931 | throtl_update_blkio_group_common(td, tg); | |
e43473b7 VG |
932 | } |
933 | ||
fe071437 VG |
934 | static void throtl_update_blkio_group_write_bps(void *key, |
935 | struct blkio_group *blkg, u64 write_bps) | |
e43473b7 | 936 | { |
fe071437 | 937 | struct throtl_data *td = key; |
de701c74 | 938 | struct throtl_grp *tg = tg_of_blkg(blkg); |
fe071437 | 939 | |
de701c74 VG |
940 | tg->bps[WRITE] = write_bps; |
941 | throtl_update_blkio_group_common(td, tg); | |
e43473b7 VG |
942 | } |
943 | ||
fe071437 VG |
944 | static void throtl_update_blkio_group_read_iops(void *key, |
945 | struct blkio_group *blkg, unsigned int read_iops) | |
8e89d13f | 946 | { |
fe071437 | 947 | struct throtl_data *td = key; |
de701c74 | 948 | struct throtl_grp *tg = tg_of_blkg(blkg); |
fe071437 | 949 | |
de701c74 VG |
950 | tg->iops[READ] = read_iops; |
951 | throtl_update_blkio_group_common(td, tg); | |
8e89d13f VG |
952 | } |
953 | ||
fe071437 VG |
954 | static void throtl_update_blkio_group_write_iops(void *key, |
955 | struct blkio_group *blkg, unsigned int write_iops) | |
8e89d13f | 956 | { |
fe071437 | 957 | struct throtl_data *td = key; |
de701c74 | 958 | struct throtl_grp *tg = tg_of_blkg(blkg); |
fe071437 | 959 | |
de701c74 VG |
960 | tg->iops[WRITE] = write_iops; |
961 | throtl_update_blkio_group_common(td, tg); | |
8e89d13f VG |
962 | } |
963 | ||
da527770 | 964 | static void throtl_shutdown_wq(struct request_queue *q) |
e43473b7 VG |
965 | { |
966 | struct throtl_data *td = q->td; | |
967 | ||
968 | cancel_delayed_work_sync(&td->throtl_work); | |
969 | } | |
970 | ||
971 | static struct blkio_policy_type blkio_policy_throtl = { | |
972 | .ops = { | |
973 | .blkio_unlink_group_fn = throtl_unlink_blkio_group, | |
974 | .blkio_update_group_read_bps_fn = | |
975 | throtl_update_blkio_group_read_bps, | |
976 | .blkio_update_group_write_bps_fn = | |
977 | throtl_update_blkio_group_write_bps, | |
8e89d13f VG |
978 | .blkio_update_group_read_iops_fn = |
979 | throtl_update_blkio_group_read_iops, | |
980 | .blkio_update_group_write_iops_fn = | |
981 | throtl_update_blkio_group_write_iops, | |
e43473b7 | 982 | }, |
8e89d13f | 983 | .plid = BLKIO_POLICY_THROTL, |
e43473b7 VG |
984 | }; |
985 | ||
986 | int blk_throtl_bio(struct request_queue *q, struct bio **biop) | |
987 | { | |
988 | struct throtl_data *td = q->td; | |
989 | struct throtl_grp *tg; | |
990 | struct bio *bio = *biop; | |
991 | bool rw = bio_data_dir(bio), update_disptime = true; | |
992 | ||
993 | if (bio->bi_rw & REQ_THROTTLED) { | |
994 | bio->bi_rw &= ~REQ_THROTTLED; | |
995 | return 0; | |
996 | } | |
997 | ||
998 | spin_lock_irq(q->queue_lock); | |
999 | tg = throtl_get_tg(td); | |
1000 | ||
1001 | if (tg->nr_queued[rw]) { | |
1002 | /* | |
1003 | * There is already another bio queued in same dir. No | |
1004 | * need to update dispatch time. | |
1005 | */ | |
231d704b | 1006 | update_disptime = false; |
e43473b7 | 1007 | goto queue_bio; |
de701c74 | 1008 | |
e43473b7 VG |
1009 | } |
1010 | ||
1011 | /* Bio is with-in rate limit of group */ | |
1012 | if (tg_may_dispatch(td, tg, bio, NULL)) { | |
1013 | throtl_charge_bio(tg, bio); | |
04521db0 VG |
1014 | |
1015 | /* | |
1016 | * We need to trim slice even when bios are not being queued | |
1017 | * otherwise it might happen that a bio is not queued for | |
1018 | * a long time and slice keeps on extending and trim is not | |
1019 | * called for a long time. Now if limits are reduced suddenly | |
1020 | * we take into account all the IO dispatched so far at new | |
1021 | * low rate and * newly queued IO gets a really long dispatch | |
1022 | * time. | |
1023 | * | |
1024 | * So keep on trimming slice even if bio is not queued. | |
1025 | */ | |
1026 | throtl_trim_slice(td, tg, rw); | |
e43473b7 VG |
1027 | goto out; |
1028 | } | |
1029 | ||
1030 | queue_bio: | |
8e89d13f VG |
1031 | throtl_log_tg(td, tg, "[%c] bio. bdisp=%u sz=%u bps=%llu" |
1032 | " iodisp=%u iops=%u queued=%d/%d", | |
1033 | rw == READ ? 'R' : 'W', | |
e43473b7 | 1034 | tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], |
8e89d13f | 1035 | tg->io_disp[rw], tg->iops[rw], |
e43473b7 VG |
1036 | tg->nr_queued[READ], tg->nr_queued[WRITE]); |
1037 | ||
1038 | throtl_add_bio_tg(q->td, tg, bio); | |
1039 | *biop = NULL; | |
1040 | ||
1041 | if (update_disptime) { | |
1042 | tg_update_disptime(td, tg); | |
1043 | throtl_schedule_next_dispatch(td); | |
1044 | } | |
1045 | ||
1046 | out: | |
1047 | spin_unlock_irq(q->queue_lock); | |
1048 | return 0; | |
1049 | } | |
1050 | ||
1051 | int blk_throtl_init(struct request_queue *q) | |
1052 | { | |
1053 | struct throtl_data *td; | |
1054 | struct throtl_grp *tg; | |
1055 | ||
1056 | td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); | |
1057 | if (!td) | |
1058 | return -ENOMEM; | |
1059 | ||
1060 | INIT_HLIST_HEAD(&td->tg_list); | |
1061 | td->tg_service_tree = THROTL_RB_ROOT; | |
de701c74 | 1062 | td->limits_changed = false; |
e43473b7 VG |
1063 | |
1064 | /* Init root group */ | |
1065 | tg = &td->root_tg; | |
1066 | INIT_HLIST_NODE(&tg->tg_node); | |
1067 | RB_CLEAR_NODE(&tg->rb_node); | |
1068 | bio_list_init(&tg->bio_lists[0]); | |
1069 | bio_list_init(&tg->bio_lists[1]); | |
1070 | ||
1071 | /* Practically unlimited BW */ | |
1072 | tg->bps[0] = tg->bps[1] = -1; | |
8e89d13f | 1073 | tg->iops[0] = tg->iops[1] = -1; |
de701c74 | 1074 | td->limits_changed = false; |
02977e4a VG |
1075 | |
1076 | /* | |
1077 | * Set root group reference to 2. One reference will be dropped when | |
1078 | * all groups on tg_list are being deleted during queue exit. Other | |
1079 | * reference will remain there as we don't want to delete this group | |
1080 | * as it is statically allocated and gets destroyed when throtl_data | |
1081 | * goes away. | |
1082 | */ | |
1083 | atomic_set(&tg->ref, 2); | |
1084 | hlist_add_head(&tg->tg_node, &td->tg_list); | |
1085 | td->nr_undestroyed_grps++; | |
e43473b7 VG |
1086 | |
1087 | INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work); | |
1088 | ||
1089 | rcu_read_lock(); | |
1090 | blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td, | |
1091 | 0, BLKIO_POLICY_THROTL); | |
1092 | rcu_read_unlock(); | |
1093 | ||
1094 | /* Attach throtl data to request queue */ | |
1095 | td->queue = q; | |
1096 | q->td = td; | |
1097 | return 0; | |
1098 | } | |
1099 | ||
1100 | void blk_throtl_exit(struct request_queue *q) | |
1101 | { | |
1102 | struct throtl_data *td = q->td; | |
1103 | bool wait = false; | |
1104 | ||
1105 | BUG_ON(!td); | |
1106 | ||
da527770 | 1107 | throtl_shutdown_wq(q); |
e43473b7 VG |
1108 | |
1109 | spin_lock_irq(q->queue_lock); | |
1110 | throtl_release_tgs(td); | |
e43473b7 VG |
1111 | |
1112 | /* If there are other groups */ | |
02977e4a | 1113 | if (td->nr_undestroyed_grps > 0) |
e43473b7 VG |
1114 | wait = true; |
1115 | ||
1116 | spin_unlock_irq(q->queue_lock); | |
1117 | ||
1118 | /* | |
1119 | * Wait for tg->blkg->key accessors to exit their grace periods. | |
1120 | * Do this wait only if there are other undestroyed groups out | |
1121 | * there (other than root group). This can happen if cgroup deletion | |
1122 | * path claimed the responsibility of cleaning up a group before | |
1123 | * queue cleanup code get to the group. | |
1124 | * | |
1125 | * Do not call synchronize_rcu() unconditionally as there are drivers | |
1126 | * which create/delete request queue hundreds of times during scan/boot | |
1127 | * and synchronize_rcu() can take significant time and slow down boot. | |
1128 | */ | |
1129 | if (wait) | |
1130 | synchronize_rcu(); | |
fe071437 VG |
1131 | |
1132 | /* | |
1133 | * Just being safe to make sure after previous flush if some body did | |
1134 | * update limits through cgroup and another work got queued, cancel | |
1135 | * it. | |
1136 | */ | |
da527770 | 1137 | throtl_shutdown_wq(q); |
e43473b7 VG |
1138 | throtl_td_free(td); |
1139 | } | |
1140 | ||
1141 | static int __init throtl_init(void) | |
1142 | { | |
450adcbe VG |
1143 | kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); |
1144 | if (!kthrotld_workqueue) | |
1145 | panic("Failed to create kthrotld\n"); | |
1146 | ||
e43473b7 VG |
1147 | blkio_policy_register(&blkio_policy_throtl); |
1148 | return 0; | |
1149 | } | |
1150 | ||
1151 | module_init(throtl_init); |