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/delay.h>
13#include "blk.h"
14#include "blk-mq.h"
15#include "blk-mq-sched.h"
16
17/*
18 * Recalculate wakeup batch when tag is shared by hctx.
19 */
20static void blk_mq_update_wake_batch(struct blk_mq_tags *tags,
21 unsigned int users)
22{
23 if (!users)
24 return;
25
26 sbitmap_queue_recalculate_wake_batch(sbq: &tags->bitmap_tags,
27 users);
28 sbitmap_queue_recalculate_wake_batch(sbq: &tags->breserved_tags,
29 users);
30}
31
32/*
33 * If a previously inactive queue goes active, bump the active user count.
34 * We need to do this before try to allocate driver tag, then even if fail
35 * to get tag when first time, the other shared-tag users could reserve
36 * budget for it.
37 */
38void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
39{
40 unsigned int users;
41 unsigned long flags;
42 struct blk_mq_tags *tags = hctx->tags;
43
44 /*
45 * calling test_bit() prior to test_and_set_bit() is intentional,
46 * it avoids dirtying the cacheline if the queue is already active.
47 */
48 if (blk_mq_is_shared_tags(flags: hctx->flags)) {
49 struct request_queue *q = hctx->queue;
50
51 if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
52 test_and_set_bit(nr: QUEUE_FLAG_HCTX_ACTIVE, addr: &q->queue_flags))
53 return;
54 } else {
55 if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
56 test_and_set_bit(nr: BLK_MQ_S_TAG_ACTIVE, addr: &hctx->state))
57 return;
58 }
59
60 spin_lock_irqsave(&tags->lock, flags);
61 users = tags->active_queues + 1;
62 WRITE_ONCE(tags->active_queues, users);
63 blk_mq_update_wake_batch(tags, users);
64 spin_unlock_irqrestore(lock: &tags->lock, flags);
65}
66
67/*
68 * Wakeup all potentially sleeping on tags
69 */
70void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
71{
72 sbitmap_queue_wake_all(sbq: &tags->bitmap_tags);
73 if (include_reserve)
74 sbitmap_queue_wake_all(sbq: &tags->breserved_tags);
75}
76
77/*
78 * If a previously busy queue goes inactive, potential waiters could now
79 * be allowed to queue. Wake them up and check.
80 */
81void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
82{
83 struct blk_mq_tags *tags = hctx->tags;
84 unsigned int users;
85
86 if (blk_mq_is_shared_tags(flags: hctx->flags)) {
87 struct request_queue *q = hctx->queue;
88
89 if (!test_and_clear_bit(nr: QUEUE_FLAG_HCTX_ACTIVE,
90 addr: &q->queue_flags))
91 return;
92 } else {
93 if (!test_and_clear_bit(nr: BLK_MQ_S_TAG_ACTIVE, addr: &hctx->state))
94 return;
95 }
96
97 spin_lock_irq(lock: &tags->lock);
98 users = tags->active_queues - 1;
99 WRITE_ONCE(tags->active_queues, users);
100 blk_mq_update_wake_batch(tags, users);
101 spin_unlock_irq(lock: &tags->lock);
102
103 blk_mq_tag_wakeup_all(tags, include_reserve: false);
104}
105
106static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
107 struct sbitmap_queue *bt)
108{
109 if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) &&
110 !hctx_may_queue(hctx: data->hctx, bt))
111 return BLK_MQ_NO_TAG;
112
113 if (data->shallow_depth)
114 return sbitmap_queue_get_shallow(sbq: bt, shallow_depth: data->shallow_depth);
115 else
116 return __sbitmap_queue_get(sbq: bt);
117}
118
119unsigned long blk_mq_get_tags(struct blk_mq_alloc_data *data, int nr_tags,
120 unsigned int *offset)
121{
122 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
123 struct sbitmap_queue *bt = &tags->bitmap_tags;
124 unsigned long ret;
125
126 if (data->shallow_depth ||data->flags & BLK_MQ_REQ_RESERVED ||
127 data->hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
128 return 0;
129 ret = __sbitmap_queue_get_batch(sbq: bt, nr_tags, offset);
130 *offset += tags->nr_reserved_tags;
131 return ret;
132}
133
134unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
135{
136 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
137 struct sbitmap_queue *bt;
138 struct sbq_wait_state *ws;
139 DEFINE_SBQ_WAIT(wait);
140 unsigned int tag_offset;
141 int tag;
142
143 if (data->flags & BLK_MQ_REQ_RESERVED) {
144 if (unlikely(!tags->nr_reserved_tags)) {
145 WARN_ON_ONCE(1);
146 return BLK_MQ_NO_TAG;
147 }
148 bt = &tags->breserved_tags;
149 tag_offset = 0;
150 } else {
151 bt = &tags->bitmap_tags;
152 tag_offset = tags->nr_reserved_tags;
153 }
154
155 tag = __blk_mq_get_tag(data, bt);
156 if (tag != BLK_MQ_NO_TAG)
157 goto found_tag;
158
159 if (data->flags & BLK_MQ_REQ_NOWAIT)
160 return BLK_MQ_NO_TAG;
161
162 ws = bt_wait_ptr(bt, hctx: data->hctx);
163 do {
164 struct sbitmap_queue *bt_prev;
165
166 /*
167 * We're out of tags on this hardware queue, kick any
168 * pending IO submits before going to sleep waiting for
169 * some to complete.
170 */
171 blk_mq_run_hw_queue(hctx: data->hctx, async: false);
172
173 /*
174 * Retry tag allocation after running the hardware queue,
175 * as running the queue may also have found completions.
176 */
177 tag = __blk_mq_get_tag(data, bt);
178 if (tag != BLK_MQ_NO_TAG)
179 break;
180
181 sbitmap_prepare_to_wait(sbq: bt, ws, sbq_wait: &wait, TASK_UNINTERRUPTIBLE);
182
183 tag = __blk_mq_get_tag(data, bt);
184 if (tag != BLK_MQ_NO_TAG)
185 break;
186
187 bt_prev = bt;
188 io_schedule();
189
190 sbitmap_finish_wait(sbq: bt, ws, sbq_wait: &wait);
191
192 data->ctx = blk_mq_get_ctx(q: data->q);
193 data->hctx = blk_mq_map_queue(opf: data->cmd_flags, ctx: data->ctx);
194 tags = blk_mq_tags_from_data(data);
195 if (data->flags & BLK_MQ_REQ_RESERVED)
196 bt = &tags->breserved_tags;
197 else
198 bt = &tags->bitmap_tags;
199
200 /*
201 * If destination hw queue is changed, fake wake up on
202 * previous queue for compensating the wake up miss, so
203 * other allocations on previous queue won't be starved.
204 */
205 if (bt != bt_prev)
206 sbitmap_queue_wake_up(sbq: bt_prev, nr: 1);
207
208 ws = bt_wait_ptr(bt, hctx: data->hctx);
209 } while (1);
210
211 sbitmap_finish_wait(sbq: bt, ws, sbq_wait: &wait);
212
213found_tag:
214 /*
215 * Give up this allocation if the hctx is inactive. The caller will
216 * retry on an active hctx.
217 */
218 if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
219 blk_mq_put_tag(tags, ctx: data->ctx, tag: tag + tag_offset);
220 return BLK_MQ_NO_TAG;
221 }
222 return tag + tag_offset;
223}
224
225void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
226 unsigned int tag)
227{
228 if (!blk_mq_tag_is_reserved(tags, tag)) {
229 const int real_tag = tag - tags->nr_reserved_tags;
230
231 BUG_ON(real_tag >= tags->nr_tags);
232 sbitmap_queue_clear(sbq: &tags->bitmap_tags, nr: real_tag, cpu: ctx->cpu);
233 } else {
234 sbitmap_queue_clear(sbq: &tags->breserved_tags, nr: tag, cpu: ctx->cpu);
235 }
236}
237
238void blk_mq_put_tags(struct blk_mq_tags *tags, int *tag_array, int nr_tags)
239{
240 sbitmap_queue_clear_batch(sbq: &tags->bitmap_tags, offset: tags->nr_reserved_tags,
241 tags: tag_array, nr_tags);
242}
243
244struct bt_iter_data {
245 struct blk_mq_hw_ctx *hctx;
246 struct request_queue *q;
247 busy_tag_iter_fn *fn;
248 void *data;
249 bool reserved;
250};
251
252static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
253 unsigned int bitnr)
254{
255 struct request *rq;
256 unsigned long flags;
257
258 spin_lock_irqsave(&tags->lock, flags);
259 rq = tags->rqs[bitnr];
260 if (!rq || rq->tag != bitnr || !req_ref_inc_not_zero(req: rq))
261 rq = NULL;
262 spin_unlock_irqrestore(lock: &tags->lock, flags);
263 return rq;
264}
265
266static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
267{
268 struct bt_iter_data *iter_data = data;
269 struct blk_mq_hw_ctx *hctx = iter_data->hctx;
270 struct request_queue *q = iter_data->q;
271 struct blk_mq_tag_set *set = q->tag_set;
272 struct blk_mq_tags *tags;
273 struct request *rq;
274 bool ret = true;
275
276 if (blk_mq_is_shared_tags(flags: set->flags))
277 tags = set->shared_tags;
278 else
279 tags = hctx->tags;
280
281 if (!iter_data->reserved)
282 bitnr += tags->nr_reserved_tags;
283 /*
284 * We can hit rq == NULL here, because the tagging functions
285 * test and set the bit before assigning ->rqs[].
286 */
287 rq = blk_mq_find_and_get_req(tags, bitnr);
288 if (!rq)
289 return true;
290
291 if (rq->q == q && (!hctx || rq->mq_hctx == hctx))
292 ret = iter_data->fn(rq, iter_data->data);
293 blk_mq_put_rq_ref(rq);
294 return ret;
295}
296
297/**
298 * bt_for_each - iterate over the requests associated with a hardware queue
299 * @hctx: Hardware queue to examine.
300 * @q: Request queue to examine.
301 * @bt: sbitmap to examine. This is either the breserved_tags member
302 * or the bitmap_tags member of struct blk_mq_tags.
303 * @fn: Pointer to the function that will be called for each request
304 * associated with @hctx that has been assigned a driver tag.
305 * @fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
306 * where rq is a pointer to a request. Return true to continue
307 * iterating tags, false to stop.
308 * @data: Will be passed as third argument to @fn.
309 * @reserved: Indicates whether @bt is the breserved_tags member or the
310 * bitmap_tags member of struct blk_mq_tags.
311 */
312static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct request_queue *q,
313 struct sbitmap_queue *bt, busy_tag_iter_fn *fn,
314 void *data, bool reserved)
315{
316 struct bt_iter_data iter_data = {
317 .hctx = hctx,
318 .fn = fn,
319 .data = data,
320 .reserved = reserved,
321 .q = q,
322 };
323
324 sbitmap_for_each_set(sb: &bt->sb, fn: bt_iter, data: &iter_data);
325}
326
327struct bt_tags_iter_data {
328 struct blk_mq_tags *tags;
329 busy_tag_iter_fn *fn;
330 void *data;
331 unsigned int flags;
332};
333
334#define BT_TAG_ITER_RESERVED (1 << 0)
335#define BT_TAG_ITER_STARTED (1 << 1)
336#define BT_TAG_ITER_STATIC_RQS (1 << 2)
337
338static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
339{
340 struct bt_tags_iter_data *iter_data = data;
341 struct blk_mq_tags *tags = iter_data->tags;
342 struct request *rq;
343 bool ret = true;
344 bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS);
345
346 if (!(iter_data->flags & BT_TAG_ITER_RESERVED))
347 bitnr += tags->nr_reserved_tags;
348
349 /*
350 * We can hit rq == NULL here, because the tagging functions
351 * test and set the bit before assigning ->rqs[].
352 */
353 if (iter_static_rqs)
354 rq = tags->static_rqs[bitnr];
355 else
356 rq = blk_mq_find_and_get_req(tags, bitnr);
357 if (!rq)
358 return true;
359
360 if (!(iter_data->flags & BT_TAG_ITER_STARTED) ||
361 blk_mq_request_started(rq))
362 ret = iter_data->fn(rq, iter_data->data);
363 if (!iter_static_rqs)
364 blk_mq_put_rq_ref(rq);
365 return ret;
366}
367
368/**
369 * bt_tags_for_each - iterate over the requests in a tag map
370 * @tags: Tag map to iterate over.
371 * @bt: sbitmap to examine. This is either the breserved_tags member
372 * or the bitmap_tags member of struct blk_mq_tags.
373 * @fn: Pointer to the function that will be called for each started
374 * request. @fn will be called as follows: @fn(rq, @data,
375 * @reserved) where rq is a pointer to a request. Return true
376 * to continue iterating tags, false to stop.
377 * @data: Will be passed as second argument to @fn.
378 * @flags: BT_TAG_ITER_*
379 */
380static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
381 busy_tag_iter_fn *fn, void *data, unsigned int flags)
382{
383 struct bt_tags_iter_data iter_data = {
384 .tags = tags,
385 .fn = fn,
386 .data = data,
387 .flags = flags,
388 };
389
390 if (tags->rqs)
391 sbitmap_for_each_set(sb: &bt->sb, fn: bt_tags_iter, data: &iter_data);
392}
393
394static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
395 busy_tag_iter_fn *fn, void *priv, unsigned int flags)
396{
397 WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);
398
399 if (tags->nr_reserved_tags)
400 bt_tags_for_each(tags, bt: &tags->breserved_tags, fn, data: priv,
401 flags: flags | BT_TAG_ITER_RESERVED);
402 bt_tags_for_each(tags, bt: &tags->bitmap_tags, fn, data: priv, flags);
403}
404
405/**
406 * blk_mq_all_tag_iter - iterate over all requests in a tag map
407 * @tags: Tag map to iterate over.
408 * @fn: Pointer to the function that will be called for each
409 * request. @fn will be called as follows: @fn(rq, @priv,
410 * reserved) where rq is a pointer to a request. 'reserved'
411 * indicates whether or not @rq is a reserved request. Return
412 * true to continue iterating tags, false to stop.
413 * @priv: Will be passed as second argument to @fn.
414 *
415 * Caller has to pass the tag map from which requests are allocated.
416 */
417void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
418 void *priv)
419{
420 __blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
421}
422
423/**
424 * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
425 * @tagset: Tag set to iterate over.
426 * @fn: Pointer to the function that will be called for each started
427 * request. @fn will be called as follows: @fn(rq, @priv,
428 * reserved) where rq is a pointer to a request. 'reserved'
429 * indicates whether or not @rq is a reserved request. Return
430 * true to continue iterating tags, false to stop.
431 * @priv: Will be passed as second argument to @fn.
432 *
433 * We grab one request reference before calling @fn and release it after
434 * @fn returns.
435 */
436void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
437 busy_tag_iter_fn *fn, void *priv)
438{
439 unsigned int flags = tagset->flags;
440 int i, nr_tags;
441
442 nr_tags = blk_mq_is_shared_tags(flags) ? 1 : tagset->nr_hw_queues;
443
444 for (i = 0; i < nr_tags; i++) {
445 if (tagset->tags && tagset->tags[i])
446 __blk_mq_all_tag_iter(tags: tagset->tags[i], fn, priv,
447 BT_TAG_ITER_STARTED);
448 }
449}
450EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
451
452static bool blk_mq_tagset_count_completed_rqs(struct request *rq, void *data)
453{
454 unsigned *count = data;
455
456 if (blk_mq_request_completed(rq))
457 (*count)++;
458 return true;
459}
460
461/**
462 * blk_mq_tagset_wait_completed_request - Wait until all scheduled request
463 * completions have finished.
464 * @tagset: Tag set to drain completed request
465 *
466 * Note: This function has to be run after all IO queues are shutdown
467 */
468void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset)
469{
470 while (true) {
471 unsigned count = 0;
472
473 blk_mq_tagset_busy_iter(tagset,
474 blk_mq_tagset_count_completed_rqs, &count);
475 if (!count)
476 break;
477 msleep(msecs: 5);
478 }
479}
480EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request);
481
482/**
483 * blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
484 * @q: Request queue to examine.
485 * @fn: Pointer to the function that will be called for each request
486 * on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
487 * reserved) where rq is a pointer to a request and hctx points
488 * to the hardware queue associated with the request. 'reserved'
489 * indicates whether or not @rq is a reserved request.
490 * @priv: Will be passed as third argument to @fn.
491 *
492 * Note: if @q->tag_set is shared with other request queues then @fn will be
493 * called for all requests on all queues that share that tag set and not only
494 * for requests associated with @q.
495 */
496void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_tag_iter_fn *fn,
497 void *priv)
498{
499 /*
500 * __blk_mq_update_nr_hw_queues() updates nr_hw_queues and hctx_table
501 * while the queue is frozen. So we can use q_usage_counter to avoid
502 * racing with it.
503 */
504 if (!percpu_ref_tryget(ref: &q->q_usage_counter))
505 return;
506
507 if (blk_mq_is_shared_tags(flags: q->tag_set->flags)) {
508 struct blk_mq_tags *tags = q->tag_set->shared_tags;
509 struct sbitmap_queue *bresv = &tags->breserved_tags;
510 struct sbitmap_queue *btags = &tags->bitmap_tags;
511
512 if (tags->nr_reserved_tags)
513 bt_for_each(NULL, q, bt: bresv, fn, data: priv, reserved: true);
514 bt_for_each(NULL, q, bt: btags, fn, data: priv, reserved: false);
515 } else {
516 struct blk_mq_hw_ctx *hctx;
517 unsigned long i;
518
519 queue_for_each_hw_ctx(q, hctx, i) {
520 struct blk_mq_tags *tags = hctx->tags;
521 struct sbitmap_queue *bresv = &tags->breserved_tags;
522 struct sbitmap_queue *btags = &tags->bitmap_tags;
523
524 /*
525 * If no software queues are currently mapped to this
526 * hardware queue, there's nothing to check
527 */
528 if (!blk_mq_hw_queue_mapped(hctx))
529 continue;
530
531 if (tags->nr_reserved_tags)
532 bt_for_each(hctx, q, bt: bresv, fn, data: priv, reserved: true);
533 bt_for_each(hctx, q, bt: btags, fn, data: priv, reserved: false);
534 }
535 }
536 blk_queue_exit(q);
537}
538
539static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
540 bool round_robin, int node)
541{
542 return sbitmap_queue_init_node(sbq: bt, depth, shift: -1, round_robin, GFP_KERNEL,
543 node);
544}
545
546struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
547 unsigned int reserved_tags, unsigned int flags, int node)
548{
549 unsigned int depth = total_tags - reserved_tags;
550 bool round_robin = flags & BLK_MQ_F_TAG_RR;
551 struct blk_mq_tags *tags;
552
553 if (total_tags > BLK_MQ_TAG_MAX) {
554 pr_err("blk-mq: tag depth too large\n");
555 return NULL;
556 }
557
558 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
559 if (!tags)
560 return NULL;
561
562 tags->nr_tags = total_tags;
563 tags->nr_reserved_tags = reserved_tags;
564 spin_lock_init(&tags->lock);
565 if (bt_alloc(bt: &tags->bitmap_tags, depth, round_robin, node))
566 goto out_free_tags;
567 if (bt_alloc(bt: &tags->breserved_tags, depth: reserved_tags, round_robin, node))
568 goto out_free_bitmap_tags;
569
570 return tags;
571
572out_free_bitmap_tags:
573 sbitmap_queue_free(sbq: &tags->bitmap_tags);
574out_free_tags:
575 kfree(objp: tags);
576 return NULL;
577}
578
579void blk_mq_free_tags(struct blk_mq_tags *tags)
580{
581 sbitmap_queue_free(sbq: &tags->bitmap_tags);
582 sbitmap_queue_free(sbq: &tags->breserved_tags);
583 kfree(objp: tags);
584}
585
586int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
587 struct blk_mq_tags **tagsptr, unsigned int tdepth,
588 bool can_grow)
589{
590 struct blk_mq_tags *tags = *tagsptr;
591
592 if (tdepth <= tags->nr_reserved_tags)
593 return -EINVAL;
594
595 /*
596 * If we are allowed to grow beyond the original size, allocate
597 * a new set of tags before freeing the old one.
598 */
599 if (tdepth > tags->nr_tags) {
600 struct blk_mq_tag_set *set = hctx->queue->tag_set;
601 struct blk_mq_tags *new;
602
603 if (!can_grow)
604 return -EINVAL;
605
606 /*
607 * We need some sort of upper limit, set it high enough that
608 * no valid use cases should require more.
609 */
610 if (tdepth > MAX_SCHED_RQ)
611 return -EINVAL;
612
613 /*
614 * Only the sbitmap needs resizing since we allocated the max
615 * initially.
616 */
617 if (blk_mq_is_shared_tags(flags: set->flags))
618 return 0;
619
620 new = blk_mq_alloc_map_and_rqs(set, hctx_idx: hctx->queue_num, depth: tdepth);
621 if (!new)
622 return -ENOMEM;
623
624 blk_mq_free_map_and_rqs(set, tags: *tagsptr, hctx_idx: hctx->queue_num);
625 *tagsptr = new;
626 } else {
627 /*
628 * Don't need (or can't) update reserved tags here, they
629 * remain static and should never need resizing.
630 */
631 sbitmap_queue_resize(sbq: &tags->bitmap_tags,
632 depth: tdepth - tags->nr_reserved_tags);
633 }
634
635 return 0;
636}
637
638void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set, unsigned int size)
639{
640 struct blk_mq_tags *tags = set->shared_tags;
641
642 sbitmap_queue_resize(sbq: &tags->bitmap_tags, depth: size - set->reserved_tags);
643}
644
645void blk_mq_tag_update_sched_shared_tags(struct request_queue *q)
646{
647 sbitmap_queue_resize(sbq: &q->sched_shared_tags->bitmap_tags,
648 depth: q->nr_requests - q->tag_set->reserved_tags);
649}
650
651/**
652 * blk_mq_unique_tag() - return a tag that is unique queue-wide
653 * @rq: request for which to compute a unique tag
654 *
655 * The tag field in struct request is unique per hardware queue but not over
656 * all hardware queues. Hence this function that returns a tag with the
657 * hardware context index in the upper bits and the per hardware queue tag in
658 * the lower bits.
659 *
660 * Note: When called for a request that is queued on a non-multiqueue request
661 * queue, the hardware context index is set to zero.
662 */
663u32 blk_mq_unique_tag(struct request *rq)
664{
665 return (rq->mq_hctx->queue_num << BLK_MQ_UNIQUE_TAG_BITS) |
666 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
667}
668EXPORT_SYMBOL(blk_mq_unique_tag);
669

source code of linux/block/blk-mq-tag.c