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1/*
2 * Fast and scalable bitmap tagging variant. Uses sparser bitmaps spread
3 * over multiple cachelines to avoid ping-pong between multiple submitters
4 * or submitter and completer. Uses rolling wakeups to avoid falling of
5 * the scaling cliff when we run out of tags and have to start putting
6 * submitters to sleep.
7 *
8 * Uses active queue tracking to support fairer distribution of tags
9 * between multiple submitters when a shared tag map is used.
10 *
11 * Copyright (C) 2013-2014 Jens Axboe
12 */
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/random.h>
16
17#include <linux/blk-mq.h>
18#include "blk.h"
19#include "blk-mq.h"
20#include "blk-mq-tag.h"
21
22static bool bt_has_free_tags(struct blk_mq_bitmap_tags *bt)
23{
24 int i;
25
26 for (i = 0; i < bt->map_nr; i++) {
27 struct blk_align_bitmap *bm = &bt->map[i];
28 int ret;
29
30 ret = find_first_zero_bit(&bm->word, bm->depth);
31 if (ret < bm->depth)
32 return true;
33 }
34
35 return false;
36}
37
38bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
39{
40 if (!tags)
41 return true;
42
43 return bt_has_free_tags(&tags->bitmap_tags);
44}
45
46static inline int bt_index_inc(int index)
47{
48 return (index + 1) & (BT_WAIT_QUEUES - 1);
49}
50
51static inline void bt_index_atomic_inc(atomic_t *index)
52{
53 int old = atomic_read(index);
54 int new = bt_index_inc(old);
55 atomic_cmpxchg(index, old, new);
56}
57
58/*
59 * If a previously inactive queue goes active, bump the active user count.
60 */
61bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
62{
63 if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
64 !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
65 atomic_inc(&hctx->tags->active_queues);
66
67 return true;
68}
69
70/*
71 * Wakeup all potentially sleeping on tags
72 */
73void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
74{
75 struct blk_mq_bitmap_tags *bt;
76 int i, wake_index;
77
78 /*
79 * Make sure all changes prior to this are visible from other CPUs.
80 */
81 smp_mb();
82 bt = &tags->bitmap_tags;
83 wake_index = atomic_read(&bt->wake_index);
84 for (i = 0; i < BT_WAIT_QUEUES; i++) {
85 struct bt_wait_state *bs = &bt->bs[wake_index];
86
87 if (waitqueue_active(&bs->wait))
88 wake_up(&bs->wait);
89
90 wake_index = bt_index_inc(wake_index);
91 }
92
93 if (include_reserve) {
94 bt = &tags->breserved_tags;
95 if (waitqueue_active(&bt->bs[0].wait))
96 wake_up(&bt->bs[0].wait);
97 }
98}
99
100/*
101 * If a previously busy queue goes inactive, potential waiters could now
102 * be allowed to queue. Wake them up and check.
103 */
104void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
105{
106 struct blk_mq_tags *tags = hctx->tags;
107
108 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
109 return;
110
111 atomic_dec(&tags->active_queues);
112
113 blk_mq_tag_wakeup_all(tags, false);
114}
115
116/*
117 * For shared tag users, we track the number of currently active users
118 * and attempt to provide a fair share of the tag depth for each of them.
119 */
120static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
121 struct blk_mq_bitmap_tags *bt)
122{
123 unsigned int depth, users;
124
125 if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
126 return true;
127 if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
128 return true;
129
130 /*
131 * Don't try dividing an ant
132 */
133 if (bt->depth == 1)
134 return true;
135
136 users = atomic_read(&hctx->tags->active_queues);
137 if (!users)
138 return true;
139
140 /*
141 * Allow at least some tags
142 */
143 depth = max((bt->depth + users - 1) / users, 4U);
144 return atomic_read(&hctx->nr_active) < depth;
145}
146
147static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag,
148 bool nowrap)
149{
150 int tag, org_last_tag = last_tag;
151
152 while (1) {
153 tag = find_next_zero_bit(&bm->word, bm->depth, last_tag);
154 if (unlikely(tag >= bm->depth)) {
155 /*
156 * We started with an offset, and we didn't reset the
157 * offset to 0 in a failure case, so start from 0 to
158 * exhaust the map.
159 */
160 if (org_last_tag && last_tag && !nowrap) {
161 last_tag = org_last_tag = 0;
162 continue;
163 }
164 return -1;
165 }
166
167 if (!test_and_set_bit(tag, &bm->word))
168 break;
169
170 last_tag = tag + 1;
171 if (last_tag >= bm->depth - 1)
172 last_tag = 0;
173 }
174
175 return tag;
176}
177
178#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)
179
180/*
181 * Straight forward bitmap tag implementation, where each bit is a tag
182 * (cleared == free, and set == busy). The small twist is using per-cpu
183 * last_tag caches, which blk-mq stores in the blk_mq_ctx software queue
184 * contexts. This enables us to drastically limit the space searched,
185 * without dirtying an extra shared cacheline like we would if we stored
186 * the cache value inside the shared blk_mq_bitmap_tags structure. On top
187 * of that, each word of tags is in a separate cacheline. This means that
188 * multiple users will tend to stick to different cachelines, at least
189 * until the map is exhausted.
190 */
191static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
192 unsigned int *tag_cache, struct blk_mq_tags *tags)
193{
194 unsigned int last_tag, org_last_tag;
195 int index, i, tag;
196
197 if (!hctx_may_queue(hctx, bt))
198 return -1;
199
200 last_tag = org_last_tag = *tag_cache;
201 index = TAG_TO_INDEX(bt, last_tag);
202
203 for (i = 0; i < bt->map_nr; i++) {
204 tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag),
205 BT_ALLOC_RR(tags));
206 if (tag != -1) {
207 tag += (index << bt->bits_per_word);
208 goto done;
209 }
210
211 /*
212 * Jump to next index, and reset the last tag to be the
213 * first tag of that index
214 */
215 index++;
216 last_tag = (index << bt->bits_per_word);
217
218 if (index >= bt->map_nr) {
219 index = 0;
220 last_tag = 0;
221 }
222 }
223
224 *tag_cache = 0;
225 return -1;
226
227 /*
228 * Only update the cache from the allocation path, if we ended
229 * up using the specific cached tag.
230 */
231done:
232 if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) {
233 last_tag = tag + 1;
234 if (last_tag >= bt->depth - 1)
235 last_tag = 0;
236
237 *tag_cache = last_tag;
238 }
239
240 return tag;
241}
242
243static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
244 struct blk_mq_hw_ctx *hctx)
245{
246 struct bt_wait_state *bs;
247 int wait_index;
248
249 if (!hctx)
250 return &bt->bs[0];
251
252 wait_index = atomic_read(&hctx->wait_index);
253 bs = &bt->bs[wait_index];
254 bt_index_atomic_inc(&hctx->wait_index);
255 return bs;
256}
257
258static int bt_get(struct blk_mq_alloc_data *data,
259 struct blk_mq_bitmap_tags *bt,
260 struct blk_mq_hw_ctx *hctx,
261 unsigned int *last_tag, struct blk_mq_tags *tags)
262{
263 struct bt_wait_state *bs;
264 DEFINE_WAIT(wait);
265 int tag;
266
267 tag = __bt_get(hctx, bt, last_tag, tags);
268 if (tag != -1)
269 return tag;
270
271 if (data->flags & BLK_MQ_REQ_NOWAIT)
272 return -1;
273
274 bs = bt_wait_ptr(bt, hctx);
275 do {
276 prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
277
278 tag = __bt_get(hctx, bt, last_tag, tags);
279 if (tag != -1)
280 break;
281
282 /*
283 * We're out of tags on this hardware queue, kick any
284 * pending IO submits before going to sleep waiting for
285 * some to complete. Note that hctx can be NULL here for
286 * reserved tag allocation.
287 */
288 if (hctx)
289 blk_mq_run_hw_queue(hctx, false);
290
291 /*
292 * Retry tag allocation after running the hardware queue,
293 * as running the queue may also have found completions.
294 */
295 tag = __bt_get(hctx, bt, last_tag, tags);
296 if (tag != -1)
297 break;
298
299 blk_mq_put_ctx(data->ctx);
300
301 io_schedule();
302
303 data->ctx = blk_mq_get_ctx(data->q);
304 data->hctx = data->q->mq_ops->map_queue(data->q,
305 data->ctx->cpu);
306 if (data->flags & BLK_MQ_REQ_RESERVED) {
307 bt = &data->hctx->tags->breserved_tags;
308 } else {
309 last_tag = &data->ctx->last_tag;
310 hctx = data->hctx;
311 bt = &hctx->tags->bitmap_tags;
312 }
313 finish_wait(&bs->wait, &wait);
314 bs = bt_wait_ptr(bt, hctx);
315 } while (1);
316
317 finish_wait(&bs->wait, &wait);
318 return tag;
319}
320
321static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
322{
323 int tag;
324
325 tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
326 &data->ctx->last_tag, data->hctx->tags);
327 if (tag >= 0)
328 return tag + data->hctx->tags->nr_reserved_tags;
329
330 return BLK_MQ_TAG_FAIL;
331}
332
333static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
334{
335 int tag, zero = 0;
336
337 if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
338 WARN_ON_ONCE(1);
339 return BLK_MQ_TAG_FAIL;
340 }
341
342 tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero,
343 data->hctx->tags);
344 if (tag < 0)
345 return BLK_MQ_TAG_FAIL;
346
347 return tag;
348}
349
350unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
351{
352 if (data->flags & BLK_MQ_REQ_RESERVED)
353 return __blk_mq_get_reserved_tag(data);
354 return __blk_mq_get_tag(data);
355}
356
357static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt)
358{
359 int i, wake_index;
360
361 wake_index = atomic_read(&bt->wake_index);
362 for (i = 0; i < BT_WAIT_QUEUES; i++) {
363 struct bt_wait_state *bs = &bt->bs[wake_index];
364
365 if (waitqueue_active(&bs->wait)) {
366 int o = atomic_read(&bt->wake_index);
367 if (wake_index != o)
368 atomic_cmpxchg(&bt->wake_index, o, wake_index);
369
370 return bs;
371 }
372
373 wake_index = bt_index_inc(wake_index);
374 }
375
376 return NULL;
377}
378
379static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
380{
381 const int index = TAG_TO_INDEX(bt, tag);
382 struct bt_wait_state *bs;
383 int wait_cnt;
384
385 clear_bit(TAG_TO_BIT(bt, tag), &bt->map[index].word);
386
387 /* Ensure that the wait list checks occur after clear_bit(). */
388 smp_mb();
389
390 bs = bt_wake_ptr(bt);
391 if (!bs)
392 return;
393
394 wait_cnt = atomic_dec_return(&bs->wait_cnt);
395 if (unlikely(wait_cnt < 0))
396 wait_cnt = atomic_inc_return(&bs->wait_cnt);
397 if (wait_cnt == 0) {
398 atomic_add(bt->wake_cnt, &bs->wait_cnt);
399 bt_index_atomic_inc(&bt->wake_index);
400 wake_up(&bs->wait);
401 }
402}
403
404void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
405 unsigned int *last_tag)
406{
407 struct blk_mq_tags *tags = hctx->tags;
408
409 if (tag >= tags->nr_reserved_tags) {
410 const int real_tag = tag - tags->nr_reserved_tags;
411
412 BUG_ON(real_tag >= tags->nr_tags);
413 bt_clear_tag(&tags->bitmap_tags, real_tag);
414 if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
415 *last_tag = real_tag;
416 } else {
417 BUG_ON(tag >= tags->nr_reserved_tags);
418 bt_clear_tag(&tags->breserved_tags, tag);
419 }
420}
421
422static void bt_for_each(struct blk_mq_hw_ctx *hctx,
423 struct blk_mq_bitmap_tags *bt, unsigned int off,
424 busy_iter_fn *fn, void *data, bool reserved)
425{
426 struct request *rq;
427 int bit, i;
428
429 for (i = 0; i < bt->map_nr; i++) {
430 struct blk_align_bitmap *bm = &bt->map[i];
431
432 for (bit = find_first_bit(&bm->word, bm->depth);
433 bit < bm->depth;
434 bit = find_next_bit(&bm->word, bm->depth, bit + 1)) {
435 rq = hctx->tags->rqs[off + bit];
436 if (rq->q == hctx->queue)
437 fn(hctx, rq, data, reserved);
438 }
439
440 off += (1 << bt->bits_per_word);
441 }
442}
443
444static void bt_tags_for_each(struct blk_mq_tags *tags,
445 struct blk_mq_bitmap_tags *bt, unsigned int off,
446 busy_tag_iter_fn *fn, void *data, bool reserved)
447{
448 struct request *rq;
449 int bit, i;
450
451 if (!tags->rqs)
452 return;
453 for (i = 0; i < bt->map_nr; i++) {
454 struct blk_align_bitmap *bm = &bt->map[i];
455
456 for (bit = find_first_bit(&bm->word, bm->depth);
457 bit < bm->depth;
458 bit = find_next_bit(&bm->word, bm->depth, bit + 1)) {
459 rq = tags->rqs[off + bit];
460 fn(rq, data, reserved);
461 }
462
463 off += (1 << bt->bits_per_word);
464 }
465}
466
467void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
468 void *priv)
469{
470 if (tags->nr_reserved_tags)
471 bt_tags_for_each(tags, &tags->breserved_tags, 0, fn, priv, true);
472 bt_tags_for_each(tags, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv,
473 false);
474}
475EXPORT_SYMBOL(blk_mq_all_tag_busy_iter);
476
477void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
478 void *priv)
479{
480 struct blk_mq_hw_ctx *hctx;
481 int i;
482
483
484 queue_for_each_hw_ctx(q, hctx, i) {
485 struct blk_mq_tags *tags = hctx->tags;
486
487 /*
488 * If not software queues are currently mapped to this
489 * hardware queue, there's nothing to check
490 */
491 if (!blk_mq_hw_queue_mapped(hctx))
492 continue;
493
494 if (tags->nr_reserved_tags)
495 bt_for_each(hctx, &tags->breserved_tags, 0, fn, priv, true);
496 bt_for_each(hctx, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv,
497 false);
498 }
499
500}
501
502static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt)
503{
504 unsigned int i, used;
505
506 for (i = 0, used = 0; i < bt->map_nr; i++) {
507 struct blk_align_bitmap *bm = &bt->map[i];
508
509 used += bitmap_weight(&bm->word, bm->depth);
510 }
511
512 return bt->depth - used;
513}
514
515static void bt_update_count(struct blk_mq_bitmap_tags *bt,
516 unsigned int depth)
517{
518 unsigned int tags_per_word = 1U << bt->bits_per_word;
519 unsigned int map_depth = depth;
520
521 if (depth) {
522 int i;
523
524 for (i = 0; i < bt->map_nr; i++) {
525 bt->map[i].depth = min(map_depth, tags_per_word);
526 map_depth -= bt->map[i].depth;
527 }
528 }
529
530 bt->wake_cnt = BT_WAIT_BATCH;
531 if (bt->wake_cnt > depth / BT_WAIT_QUEUES)
532 bt->wake_cnt = max(1U, depth / BT_WAIT_QUEUES);
533
534 bt->depth = depth;
535}
536
537static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
538 int node, bool reserved)
539{
540 int i;
541
542 bt->bits_per_word = ilog2(BITS_PER_LONG);
543
544 /*
545 * Depth can be zero for reserved tags, that's not a failure
546 * condition.
547 */
548 if (depth) {
549 unsigned int nr, tags_per_word;
550
551 tags_per_word = (1 << bt->bits_per_word);
552
553 /*
554 * If the tag space is small, shrink the number of tags
555 * per word so we spread over a few cachelines, at least.
556 * If less than 4 tags, just forget about it, it's not
557 * going to work optimally anyway.
558 */
559 if (depth >= 4) {
560 while (tags_per_word * 4 > depth) {
561 bt->bits_per_word--;
562 tags_per_word = (1 << bt->bits_per_word);
563 }
564 }
565
566 nr = ALIGN(depth, tags_per_word) / tags_per_word;
567 bt->map = kzalloc_node(nr * sizeof(struct blk_align_bitmap),
568 GFP_KERNEL, node);
569 if (!bt->map)
570 return -ENOMEM;
571
572 bt->map_nr = nr;
573 }
574
575 bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL);
576 if (!bt->bs) {
577 kfree(bt->map);
578 bt->map = NULL;
579 return -ENOMEM;
580 }
581
582 bt_update_count(bt, depth);
583
584 for (i = 0; i < BT_WAIT_QUEUES; i++) {
585 init_waitqueue_head(&bt->bs[i].wait);
586 atomic_set(&bt->bs[i].wait_cnt, bt->wake_cnt);
587 }
588
589 return 0;
590}
591
592static void bt_free(struct blk_mq_bitmap_tags *bt)
593{
594 kfree(bt->map);
595 kfree(bt->bs);
596}
597
598static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
599 int node, int alloc_policy)
600{
601 unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
602
603 tags->alloc_policy = alloc_policy;
604
605 if (bt_alloc(&tags->bitmap_tags, depth, node, false))
606 goto enomem;
607 if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
608 goto enomem;
609
610 return tags;
611enomem:
612 bt_free(&tags->bitmap_tags);
613 kfree(tags);
614 return NULL;
615}
616
617struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
618 unsigned int reserved_tags,
619 int node, int alloc_policy)
620{
621 struct blk_mq_tags *tags;
622
623 if (total_tags > BLK_MQ_TAG_MAX) {
624 pr_err("blk-mq: tag depth too large\n");
625 return NULL;
626 }
627
628 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
629 if (!tags)
630 return NULL;
631
632 if (!zalloc_cpumask_var(&tags->cpumask, GFP_KERNEL)) {
633 kfree(tags);
634 return NULL;
635 }
636
637 tags->nr_tags = total_tags;
638 tags->nr_reserved_tags = reserved_tags;
639
640 return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
641}
642
643void blk_mq_free_tags(struct blk_mq_tags *tags)
644{
645 bt_free(&tags->bitmap_tags);
646 bt_free(&tags->breserved_tags);
647 free_cpumask_var(tags->cpumask);
648 kfree(tags);
649}
650
651void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *tag)
652{
653 unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
654
655 *tag = prandom_u32() % depth;
656}
657
658int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
659{
660 tdepth -= tags->nr_reserved_tags;
661 if (tdepth > tags->nr_tags)
662 return -EINVAL;
663
664 /*
665 * Don't need (or can't) update reserved tags here, they remain
666 * static and should never need resizing.
667 */
668 bt_update_count(&tags->bitmap_tags, tdepth);
669 blk_mq_tag_wakeup_all(tags, false);
670 return 0;
671}
672
673/**
674 * blk_mq_unique_tag() - return a tag that is unique queue-wide
675 * @rq: request for which to compute a unique tag
676 *
677 * The tag field in struct request is unique per hardware queue but not over
678 * all hardware queues. Hence this function that returns a tag with the
679 * hardware context index in the upper bits and the per hardware queue tag in
680 * the lower bits.
681 *
682 * Note: When called for a request that is queued on a non-multiqueue request
683 * queue, the hardware context index is set to zero.
684 */
685u32 blk_mq_unique_tag(struct request *rq)
686{
687 struct request_queue *q = rq->q;
688 struct blk_mq_hw_ctx *hctx;
689 int hwq = 0;
690
691 if (q->mq_ops) {
692 hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
693 hwq = hctx->queue_num;
694 }
695
696 return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
697 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
698}
699EXPORT_SYMBOL(blk_mq_unique_tag);
700
701ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
702{
703 char *orig_page = page;
704 unsigned int free, res;
705
706 if (!tags)
707 return 0;
708
709 page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
710 "bits_per_word=%u\n",
711 tags->nr_tags, tags->nr_reserved_tags,
712 tags->bitmap_tags.bits_per_word);
713
714 free = bt_unused_tags(&tags->bitmap_tags);
715 res = bt_unused_tags(&tags->breserved_tags);
716
717 page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res);
718 page += sprintf(page, "active_queues=%u\n", atomic_read(&tags->active_queues));
719
720 return page - orig_page;
721}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tag allocation using scalable bitmaps. Uses active queue tracking to support
4 * fairer distribution of tags between multiple submitters when a shared tag map
5 * is used.
6 *
7 * Copyright (C) 2013-2014 Jens Axboe
8 */
9#include <linux/kernel.h>
10#include <linux/module.h>
11
12#include <linux/blk-mq.h>
13#include <linux/delay.h>
14#include "blk.h"
15#include "blk-mq.h"
16#include "blk-mq-tag.h"
17
18/*
19 * If a previously inactive queue goes active, bump the active user count.
20 * We need to do this before try to allocate driver tag, then even if fail
21 * to get tag when first time, the other shared-tag users could reserve
22 * budget for it.
23 */
24bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
25{
26 if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
27 !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
28 atomic_inc(&hctx->tags->active_queues);
29
30 return true;
31}
32
33/*
34 * Wakeup all potentially sleeping on tags
35 */
36void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
37{
38 sbitmap_queue_wake_all(&tags->bitmap_tags);
39 if (include_reserve)
40 sbitmap_queue_wake_all(&tags->breserved_tags);
41}
42
43/*
44 * If a previously busy queue goes inactive, potential waiters could now
45 * be allowed to queue. Wake them up and check.
46 */
47void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
48{
49 struct blk_mq_tags *tags = hctx->tags;
50
51 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
52 return;
53
54 atomic_dec(&tags->active_queues);
55
56 blk_mq_tag_wakeup_all(tags, false);
57}
58
59static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
60 struct sbitmap_queue *bt)
61{
62 if (!data->q->elevator && !hctx_may_queue(data->hctx, bt))
63 return BLK_MQ_NO_TAG;
64
65 if (data->shallow_depth)
66 return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
67 else
68 return __sbitmap_queue_get(bt);
69}
70
71unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
72{
73 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
74 struct sbitmap_queue *bt;
75 struct sbq_wait_state *ws;
76 DEFINE_SBQ_WAIT(wait);
77 unsigned int tag_offset;
78 int tag;
79
80 if (data->flags & BLK_MQ_REQ_RESERVED) {
81 if (unlikely(!tags->nr_reserved_tags)) {
82 WARN_ON_ONCE(1);
83 return BLK_MQ_NO_TAG;
84 }
85 bt = &tags->breserved_tags;
86 tag_offset = 0;
87 } else {
88 bt = &tags->bitmap_tags;
89 tag_offset = tags->nr_reserved_tags;
90 }
91
92 tag = __blk_mq_get_tag(data, bt);
93 if (tag != BLK_MQ_NO_TAG)
94 goto found_tag;
95
96 if (data->flags & BLK_MQ_REQ_NOWAIT)
97 return BLK_MQ_NO_TAG;
98
99 ws = bt_wait_ptr(bt, data->hctx);
100 do {
101 struct sbitmap_queue *bt_prev;
102
103 /*
104 * We're out of tags on this hardware queue, kick any
105 * pending IO submits before going to sleep waiting for
106 * some to complete.
107 */
108 blk_mq_run_hw_queue(data->hctx, false);
109
110 /*
111 * Retry tag allocation after running the hardware queue,
112 * as running the queue may also have found completions.
113 */
114 tag = __blk_mq_get_tag(data, bt);
115 if (tag != BLK_MQ_NO_TAG)
116 break;
117
118 sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);
119
120 tag = __blk_mq_get_tag(data, bt);
121 if (tag != BLK_MQ_NO_TAG)
122 break;
123
124 bt_prev = bt;
125 io_schedule();
126
127 sbitmap_finish_wait(bt, ws, &wait);
128
129 data->ctx = blk_mq_get_ctx(data->q);
130 data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
131 data->ctx);
132 tags = blk_mq_tags_from_data(data);
133 if (data->flags & BLK_MQ_REQ_RESERVED)
134 bt = &tags->breserved_tags;
135 else
136 bt = &tags->bitmap_tags;
137
138 /*
139 * If destination hw queue is changed, fake wake up on
140 * previous queue for compensating the wake up miss, so
141 * other allocations on previous queue won't be starved.
142 */
143 if (bt != bt_prev)
144 sbitmap_queue_wake_up(bt_prev);
145
146 ws = bt_wait_ptr(bt, data->hctx);
147 } while (1);
148
149 sbitmap_finish_wait(bt, ws, &wait);
150
151found_tag:
152 /*
153 * Give up this allocation if the hctx is inactive. The caller will
154 * retry on an active hctx.
155 */
156 if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
157 blk_mq_put_tag(tags, data->ctx, tag + tag_offset);
158 return BLK_MQ_NO_TAG;
159 }
160 return tag + tag_offset;
161}
162
163void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
164 unsigned int tag)
165{
166 if (!blk_mq_tag_is_reserved(tags, tag)) {
167 const int real_tag = tag - tags->nr_reserved_tags;
168
169 BUG_ON(real_tag >= tags->nr_tags);
170 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
171 } else {
172 BUG_ON(tag >= tags->nr_reserved_tags);
173 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
174 }
175}
176
177struct bt_iter_data {
178 struct blk_mq_hw_ctx *hctx;
179 busy_iter_fn *fn;
180 void *data;
181 bool reserved;
182};
183
184static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
185{
186 struct bt_iter_data *iter_data = data;
187 struct blk_mq_hw_ctx *hctx = iter_data->hctx;
188 struct blk_mq_tags *tags = hctx->tags;
189 bool reserved = iter_data->reserved;
190 struct request *rq;
191
192 if (!reserved)
193 bitnr += tags->nr_reserved_tags;
194 rq = tags->rqs[bitnr];
195
196 /*
197 * We can hit rq == NULL here, because the tagging functions
198 * test and set the bit before assigning ->rqs[].
199 */
200 if (rq && rq->q == hctx->queue)
201 return iter_data->fn(hctx, rq, iter_data->data, reserved);
202 return true;
203}
204
205/**
206 * bt_for_each - iterate over the requests associated with a hardware queue
207 * @hctx: Hardware queue to examine.
208 * @bt: sbitmap to examine. This is either the breserved_tags member
209 * or the bitmap_tags member of struct blk_mq_tags.
210 * @fn: Pointer to the function that will be called for each request
211 * associated with @hctx that has been assigned a driver tag.
212 * @fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
213 * where rq is a pointer to a request. Return true to continue
214 * iterating tags, false to stop.
215 * @data: Will be passed as third argument to @fn.
216 * @reserved: Indicates whether @bt is the breserved_tags member or the
217 * bitmap_tags member of struct blk_mq_tags.
218 */
219static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
220 busy_iter_fn *fn, void *data, bool reserved)
221{
222 struct bt_iter_data iter_data = {
223 .hctx = hctx,
224 .fn = fn,
225 .data = data,
226 .reserved = reserved,
227 };
228
229 sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
230}
231
232struct bt_tags_iter_data {
233 struct blk_mq_tags *tags;
234 busy_tag_iter_fn *fn;
235 void *data;
236 unsigned int flags;
237};
238
239#define BT_TAG_ITER_RESERVED (1 << 0)
240#define BT_TAG_ITER_STARTED (1 << 1)
241#define BT_TAG_ITER_STATIC_RQS (1 << 2)
242
243static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
244{
245 struct bt_tags_iter_data *iter_data = data;
246 struct blk_mq_tags *tags = iter_data->tags;
247 bool reserved = iter_data->flags & BT_TAG_ITER_RESERVED;
248 struct request *rq;
249
250 if (!reserved)
251 bitnr += tags->nr_reserved_tags;
252
253 /*
254 * We can hit rq == NULL here, because the tagging functions
255 * test and set the bit before assigning ->rqs[].
256 */
257 if (iter_data->flags & BT_TAG_ITER_STATIC_RQS)
258 rq = tags->static_rqs[bitnr];
259 else
260 rq = tags->rqs[bitnr];
261 if (!rq)
262 return true;
263 if ((iter_data->flags & BT_TAG_ITER_STARTED) &&
264 !blk_mq_request_started(rq))
265 return true;
266 return iter_data->fn(rq, iter_data->data, reserved);
267}
268
269/**
270 * bt_tags_for_each - iterate over the requests in a tag map
271 * @tags: Tag map to iterate over.
272 * @bt: sbitmap to examine. This is either the breserved_tags member
273 * or the bitmap_tags member of struct blk_mq_tags.
274 * @fn: Pointer to the function that will be called for each started
275 * request. @fn will be called as follows: @fn(rq, @data,
276 * @reserved) where rq is a pointer to a request. Return true
277 * to continue iterating tags, false to stop.
278 * @data: Will be passed as second argument to @fn.
279 * @flags: BT_TAG_ITER_*
280 */
281static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
282 busy_tag_iter_fn *fn, void *data, unsigned int flags)
283{
284 struct bt_tags_iter_data iter_data = {
285 .tags = tags,
286 .fn = fn,
287 .data = data,
288 .flags = flags,
289 };
290
291 if (tags->rqs)
292 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
293}
294
295static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
296 busy_tag_iter_fn *fn, void *priv, unsigned int flags)
297{
298 WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);
299
300 if (tags->nr_reserved_tags)
301 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv,
302 flags | BT_TAG_ITER_RESERVED);
303 bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, flags);
304}
305
306/**
307 * blk_mq_all_tag_iter - iterate over all requests in a tag map
308 * @tags: Tag map to iterate over.
309 * @fn: Pointer to the function that will be called for each
310 * request. @fn will be called as follows: @fn(rq, @priv,
311 * reserved) where rq is a pointer to a request. 'reserved'
312 * indicates whether or not @rq is a reserved request. Return
313 * true to continue iterating tags, false to stop.
314 * @priv: Will be passed as second argument to @fn.
315 *
316 * Caller has to pass the tag map from which requests are allocated.
317 */
318void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
319 void *priv)
320{
321 __blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
322}
323
324/**
325 * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
326 * @tagset: Tag set to iterate over.
327 * @fn: Pointer to the function that will be called for each started
328 * request. @fn will be called as follows: @fn(rq, @priv,
329 * reserved) where rq is a pointer to a request. 'reserved'
330 * indicates whether or not @rq is a reserved request. Return
331 * true to continue iterating tags, false to stop.
332 * @priv: Will be passed as second argument to @fn.
333 */
334void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
335 busy_tag_iter_fn *fn, void *priv)
336{
337 int i;
338
339 for (i = 0; i < tagset->nr_hw_queues; i++) {
340 if (tagset->tags && tagset->tags[i])
341 __blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
342 BT_TAG_ITER_STARTED);
343 }
344}
345EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
346
347static bool blk_mq_tagset_count_completed_rqs(struct request *rq,
348 void *data, bool reserved)
349{
350 unsigned *count = data;
351
352 if (blk_mq_request_completed(rq))
353 (*count)++;
354 return true;
355}
356
357/**
358 * blk_mq_tagset_wait_completed_request - wait until all completed req's
359 * complete funtion is run
360 * @tagset: Tag set to drain completed request
361 *
362 * Note: This function has to be run after all IO queues are shutdown
363 */
364void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset)
365{
366 while (true) {
367 unsigned count = 0;
368
369 blk_mq_tagset_busy_iter(tagset,
370 blk_mq_tagset_count_completed_rqs, &count);
371 if (!count)
372 break;
373 msleep(5);
374 }
375}
376EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request);
377
378/**
379 * blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
380 * @q: Request queue to examine.
381 * @fn: Pointer to the function that will be called for each request
382 * on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
383 * reserved) where rq is a pointer to a request and hctx points
384 * to the hardware queue associated with the request. 'reserved'
385 * indicates whether or not @rq is a reserved request.
386 * @priv: Will be passed as third argument to @fn.
387 *
388 * Note: if @q->tag_set is shared with other request queues then @fn will be
389 * called for all requests on all queues that share that tag set and not only
390 * for requests associated with @q.
391 */
392void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
393 void *priv)
394{
395 struct blk_mq_hw_ctx *hctx;
396 int i;
397
398 /*
399 * __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
400 * while the queue is frozen. So we can use q_usage_counter to avoid
401 * racing with it. __blk_mq_update_nr_hw_queues() uses
402 * synchronize_rcu() to ensure this function left the critical section
403 * below.
404 */
405 if (!percpu_ref_tryget(&q->q_usage_counter))
406 return;
407
408 queue_for_each_hw_ctx(q, hctx, i) {
409 struct blk_mq_tags *tags = hctx->tags;
410
411 /*
412 * If no software queues are currently mapped to this
413 * hardware queue, there's nothing to check
414 */
415 if (!blk_mq_hw_queue_mapped(hctx))
416 continue;
417
418 if (tags->nr_reserved_tags)
419 bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
420 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
421 }
422 blk_queue_exit(q);
423}
424
425static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
426 bool round_robin, int node)
427{
428 return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
429 node);
430}
431
432static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
433 int node, int alloc_policy)
434{
435 unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
436 bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
437
438 if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
439 goto free_tags;
440 if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
441 node))
442 goto free_bitmap_tags;
443
444 return tags;
445free_bitmap_tags:
446 sbitmap_queue_free(&tags->bitmap_tags);
447free_tags:
448 kfree(tags);
449 return NULL;
450}
451
452struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
453 unsigned int reserved_tags,
454 int node, int alloc_policy)
455{
456 struct blk_mq_tags *tags;
457
458 if (total_tags > BLK_MQ_TAG_MAX) {
459 pr_err("blk-mq: tag depth too large\n");
460 return NULL;
461 }
462
463 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
464 if (!tags)
465 return NULL;
466
467 tags->nr_tags = total_tags;
468 tags->nr_reserved_tags = reserved_tags;
469
470 return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
471}
472
473void blk_mq_free_tags(struct blk_mq_tags *tags)
474{
475 sbitmap_queue_free(&tags->bitmap_tags);
476 sbitmap_queue_free(&tags->breserved_tags);
477 kfree(tags);
478}
479
480int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
481 struct blk_mq_tags **tagsptr, unsigned int tdepth,
482 bool can_grow)
483{
484 struct blk_mq_tags *tags = *tagsptr;
485
486 if (tdepth <= tags->nr_reserved_tags)
487 return -EINVAL;
488
489 /*
490 * If we are allowed to grow beyond the original size, allocate
491 * a new set of tags before freeing the old one.
492 */
493 if (tdepth > tags->nr_tags) {
494 struct blk_mq_tag_set *set = hctx->queue->tag_set;
495 struct blk_mq_tags *new;
496 bool ret;
497
498 if (!can_grow)
499 return -EINVAL;
500
501 /*
502 * We need some sort of upper limit, set it high enough that
503 * no valid use cases should require more.
504 */
505 if (tdepth > 16 * BLKDEV_MAX_RQ)
506 return -EINVAL;
507
508 new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
509 tags->nr_reserved_tags);
510 if (!new)
511 return -ENOMEM;
512 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
513 if (ret) {
514 blk_mq_free_rq_map(new);
515 return -ENOMEM;
516 }
517
518 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
519 blk_mq_free_rq_map(*tagsptr);
520 *tagsptr = new;
521 } else {
522 /*
523 * Don't need (or can't) update reserved tags here, they
524 * remain static and should never need resizing.
525 */
526 sbitmap_queue_resize(&tags->bitmap_tags,
527 tdepth - tags->nr_reserved_tags);
528 }
529
530 return 0;
531}
532
533/**
534 * blk_mq_unique_tag() - return a tag that is unique queue-wide
535 * @rq: request for which to compute a unique tag
536 *
537 * The tag field in struct request is unique per hardware queue but not over
538 * all hardware queues. Hence this function that returns a tag with the
539 * hardware context index in the upper bits and the per hardware queue tag in
540 * the lower bits.
541 *
542 * Note: When called for a request that is queued on a non-multiqueue request
543 * queue, the hardware context index is set to zero.
544 */
545u32 blk_mq_unique_tag(struct request *rq)
546{
547 return (rq->mq_hctx->queue_num << BLK_MQ_UNIQUE_TAG_BITS) |
548 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
549}
550EXPORT_SYMBOL(blk_mq_unique_tag);