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