1 // SPDX-License-Identifier: GPL-2.0
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
7 * Copyright (C) 2013-2014 Jens Axboe
9 #include <linux/kernel.h>
10 #include <linux/module.h>
12 #include <linux/blk-mq.h>
13 #include <linux/delay.h>
16 #include "blk-mq-sched.h"
17 #include "blk-mq-tag.h"
20 * Recalculate wakeup batch when tag is shared by hctx.
22 static void blk_mq_update_wake_batch(struct blk_mq_tags *tags,
28 sbitmap_queue_recalculate_wake_batch(&tags->bitmap_tags,
30 sbitmap_queue_recalculate_wake_batch(&tags->breserved_tags,
35 * If a previously inactive queue goes active, bump the active user count.
36 * We need to do this before try to allocate driver tag, then even if fail
37 * to get tag when first time, the other shared-tag users could reserve
40 void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
45 * calling test_bit() prior to test_and_set_bit() is intentional,
46 * it avoids dirtying the cacheline if the queue is already active.
48 if (blk_mq_is_shared_tags(hctx->flags)) {
49 struct request_queue *q = hctx->queue;
51 if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
52 test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
55 if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
56 test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
60 users = atomic_inc_return(&hctx->tags->active_queues);
62 blk_mq_update_wake_batch(hctx->tags, users);
66 * Wakeup all potentially sleeping on tags
68 void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
70 sbitmap_queue_wake_all(&tags->bitmap_tags);
72 sbitmap_queue_wake_all(&tags->breserved_tags);
76 * If a previously busy queue goes inactive, potential waiters could now
77 * be allowed to queue. Wake them up and check.
79 void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
81 struct blk_mq_tags *tags = hctx->tags;
84 if (blk_mq_is_shared_tags(hctx->flags)) {
85 struct request_queue *q = hctx->queue;
87 if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
91 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
95 users = atomic_dec_return(&tags->active_queues);
97 blk_mq_update_wake_batch(tags, users);
99 blk_mq_tag_wakeup_all(tags, false);
102 static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
103 struct sbitmap_queue *bt)
105 if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) &&
106 !hctx_may_queue(data->hctx, bt))
107 return BLK_MQ_NO_TAG;
109 if (data->shallow_depth)
110 return sbitmap_queue_get_shallow(bt, data->shallow_depth);
112 return __sbitmap_queue_get(bt);
115 unsigned long blk_mq_get_tags(struct blk_mq_alloc_data *data, int nr_tags,
116 unsigned int *offset)
118 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
119 struct sbitmap_queue *bt = &tags->bitmap_tags;
122 if (data->shallow_depth ||data->flags & BLK_MQ_REQ_RESERVED ||
123 data->hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
125 ret = __sbitmap_queue_get_batch(bt, nr_tags, offset);
126 *offset += tags->nr_reserved_tags;
130 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
132 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
133 struct sbitmap_queue *bt;
134 struct sbq_wait_state *ws;
135 DEFINE_SBQ_WAIT(wait);
136 unsigned int tag_offset;
139 if (data->flags & BLK_MQ_REQ_RESERVED) {
140 if (unlikely(!tags->nr_reserved_tags)) {
142 return BLK_MQ_NO_TAG;
144 bt = &tags->breserved_tags;
147 bt = &tags->bitmap_tags;
148 tag_offset = tags->nr_reserved_tags;
151 tag = __blk_mq_get_tag(data, bt);
152 if (tag != BLK_MQ_NO_TAG)
155 if (data->flags & BLK_MQ_REQ_NOWAIT)
156 return BLK_MQ_NO_TAG;
158 ws = bt_wait_ptr(bt, data->hctx);
160 struct sbitmap_queue *bt_prev;
163 * We're out of tags on this hardware queue, kick any
164 * pending IO submits before going to sleep waiting for
167 blk_mq_run_hw_queue(data->hctx, false);
170 * Retry tag allocation after running the hardware queue,
171 * as running the queue may also have found completions.
173 tag = __blk_mq_get_tag(data, bt);
174 if (tag != BLK_MQ_NO_TAG)
177 sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);
179 tag = __blk_mq_get_tag(data, bt);
180 if (tag != BLK_MQ_NO_TAG)
186 sbitmap_finish_wait(bt, ws, &wait);
188 data->ctx = blk_mq_get_ctx(data->q);
189 data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
191 tags = blk_mq_tags_from_data(data);
192 if (data->flags & BLK_MQ_REQ_RESERVED)
193 bt = &tags->breserved_tags;
195 bt = &tags->bitmap_tags;
198 * If destination hw queue is changed, fake wake up on
199 * previous queue for compensating the wake up miss, so
200 * other allocations on previous queue won't be starved.
203 sbitmap_queue_wake_up(bt_prev, 1);
205 ws = bt_wait_ptr(bt, data->hctx);
208 sbitmap_finish_wait(bt, ws, &wait);
212 * Give up this allocation if the hctx is inactive. The caller will
213 * retry on an active hctx.
215 if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
216 blk_mq_put_tag(tags, data->ctx, tag + tag_offset);
217 return BLK_MQ_NO_TAG;
219 return tag + tag_offset;
222 void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
225 if (!blk_mq_tag_is_reserved(tags, tag)) {
226 const int real_tag = tag - tags->nr_reserved_tags;
228 BUG_ON(real_tag >= tags->nr_tags);
229 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
231 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
235 void blk_mq_put_tags(struct blk_mq_tags *tags, int *tag_array, int nr_tags)
237 sbitmap_queue_clear_batch(&tags->bitmap_tags, tags->nr_reserved_tags,
241 struct bt_iter_data {
242 struct blk_mq_hw_ctx *hctx;
243 struct request_queue *q;
244 busy_tag_iter_fn *fn;
249 static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
255 spin_lock_irqsave(&tags->lock, flags);
256 rq = tags->rqs[bitnr];
257 if (!rq || rq->tag != bitnr || !req_ref_inc_not_zero(rq))
259 spin_unlock_irqrestore(&tags->lock, flags);
263 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
265 struct bt_iter_data *iter_data = data;
266 struct blk_mq_hw_ctx *hctx = iter_data->hctx;
267 struct request_queue *q = iter_data->q;
268 struct blk_mq_tag_set *set = q->tag_set;
269 struct blk_mq_tags *tags;
273 if (blk_mq_is_shared_tags(set->flags))
274 tags = set->shared_tags;
278 if (!iter_data->reserved)
279 bitnr += tags->nr_reserved_tags;
281 * We can hit rq == NULL here, because the tagging functions
282 * test and set the bit before assigning ->rqs[].
284 rq = blk_mq_find_and_get_req(tags, bitnr);
288 if (rq->q == q && (!hctx || rq->mq_hctx == hctx))
289 ret = iter_data->fn(rq, iter_data->data);
290 blk_mq_put_rq_ref(rq);
295 * bt_for_each - iterate over the requests associated with a hardware queue
296 * @hctx: Hardware queue to examine.
297 * @q: Request queue to examine.
298 * @bt: sbitmap to examine. This is either the breserved_tags member
299 * or the bitmap_tags member of struct blk_mq_tags.
300 * @fn: Pointer to the function that will be called for each request
301 * associated with @hctx that has been assigned a driver tag.
302 * @fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
303 * where rq is a pointer to a request. Return true to continue
304 * iterating tags, false to stop.
305 * @data: Will be passed as third argument to @fn.
306 * @reserved: Indicates whether @bt is the breserved_tags member or the
307 * bitmap_tags member of struct blk_mq_tags.
309 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct request_queue *q,
310 struct sbitmap_queue *bt, busy_tag_iter_fn *fn,
311 void *data, bool reserved)
313 struct bt_iter_data iter_data = {
317 .reserved = reserved,
321 sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
324 struct bt_tags_iter_data {
325 struct blk_mq_tags *tags;
326 busy_tag_iter_fn *fn;
331 #define BT_TAG_ITER_RESERVED (1 << 0)
332 #define BT_TAG_ITER_STARTED (1 << 1)
333 #define BT_TAG_ITER_STATIC_RQS (1 << 2)
335 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
337 struct bt_tags_iter_data *iter_data = data;
338 struct blk_mq_tags *tags = iter_data->tags;
341 bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS);
343 if (!(iter_data->flags & BT_TAG_ITER_RESERVED))
344 bitnr += tags->nr_reserved_tags;
347 * We can hit rq == NULL here, because the tagging functions
348 * test and set the bit before assigning ->rqs[].
351 rq = tags->static_rqs[bitnr];
353 rq = blk_mq_find_and_get_req(tags, bitnr);
357 if (!(iter_data->flags & BT_TAG_ITER_STARTED) ||
358 blk_mq_request_started(rq))
359 ret = iter_data->fn(rq, iter_data->data);
360 if (!iter_static_rqs)
361 blk_mq_put_rq_ref(rq);
366 * bt_tags_for_each - iterate over the requests in a tag map
367 * @tags: Tag map to iterate over.
368 * @bt: sbitmap to examine. This is either the breserved_tags member
369 * or the bitmap_tags member of struct blk_mq_tags.
370 * @fn: Pointer to the function that will be called for each started
371 * request. @fn will be called as follows: @fn(rq, @data,
372 * @reserved) where rq is a pointer to a request. Return true
373 * to continue iterating tags, false to stop.
374 * @data: Will be passed as second argument to @fn.
375 * @flags: BT_TAG_ITER_*
377 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
378 busy_tag_iter_fn *fn, void *data, unsigned int flags)
380 struct bt_tags_iter_data iter_data = {
388 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
391 static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
392 busy_tag_iter_fn *fn, void *priv, unsigned int flags)
394 WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);
396 if (tags->nr_reserved_tags)
397 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv,
398 flags | BT_TAG_ITER_RESERVED);
399 bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, flags);
403 * blk_mq_all_tag_iter - iterate over all requests in a tag map
404 * @tags: Tag map to iterate over.
405 * @fn: Pointer to the function that will be called for each
406 * request. @fn will be called as follows: @fn(rq, @priv,
407 * reserved) where rq is a pointer to a request. 'reserved'
408 * indicates whether or not @rq is a reserved request. Return
409 * true to continue iterating tags, false to stop.
410 * @priv: Will be passed as second argument to @fn.
412 * Caller has to pass the tag map from which requests are allocated.
414 void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
417 __blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
421 * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
422 * @tagset: Tag set to iterate over.
423 * @fn: Pointer to the function that will be called for each started
424 * request. @fn will be called as follows: @fn(rq, @priv,
425 * reserved) where rq is a pointer to a request. 'reserved'
426 * indicates whether or not @rq is a reserved request. Return
427 * true to continue iterating tags, false to stop.
428 * @priv: Will be passed as second argument to @fn.
430 * We grab one request reference before calling @fn and release it after
433 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
434 busy_tag_iter_fn *fn, void *priv)
436 unsigned int flags = tagset->flags;
439 nr_tags = blk_mq_is_shared_tags(flags) ? 1 : tagset->nr_hw_queues;
441 for (i = 0; i < nr_tags; i++) {
442 if (tagset->tags && tagset->tags[i])
443 __blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
444 BT_TAG_ITER_STARTED);
447 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
449 static bool blk_mq_tagset_count_completed_rqs(struct request *rq, void *data)
451 unsigned *count = data;
453 if (blk_mq_request_completed(rq))
459 * blk_mq_tagset_wait_completed_request - Wait until all scheduled request
460 * completions have finished.
461 * @tagset: Tag set to drain completed request
463 * Note: This function has to be run after all IO queues are shutdown
465 void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset)
470 blk_mq_tagset_busy_iter(tagset,
471 blk_mq_tagset_count_completed_rqs, &count);
477 EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request);
480 * blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
481 * @q: Request queue to examine.
482 * @fn: Pointer to the function that will be called for each request
483 * on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
484 * reserved) where rq is a pointer to a request and hctx points
485 * to the hardware queue associated with the request. 'reserved'
486 * indicates whether or not @rq is a reserved request.
487 * @priv: Will be passed as third argument to @fn.
489 * Note: if @q->tag_set is shared with other request queues then @fn will be
490 * called for all requests on all queues that share that tag set and not only
491 * for requests associated with @q.
493 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_tag_iter_fn *fn,
497 * __blk_mq_update_nr_hw_queues() updates nr_hw_queues and hctx_table
498 * while the queue is frozen. So we can use q_usage_counter to avoid
501 if (!percpu_ref_tryget(&q->q_usage_counter))
504 if (blk_mq_is_shared_tags(q->tag_set->flags)) {
505 struct blk_mq_tags *tags = q->tag_set->shared_tags;
506 struct sbitmap_queue *bresv = &tags->breserved_tags;
507 struct sbitmap_queue *btags = &tags->bitmap_tags;
509 if (tags->nr_reserved_tags)
510 bt_for_each(NULL, q, bresv, fn, priv, true);
511 bt_for_each(NULL, q, btags, fn, priv, false);
513 struct blk_mq_hw_ctx *hctx;
516 queue_for_each_hw_ctx(q, hctx, i) {
517 struct blk_mq_tags *tags = hctx->tags;
518 struct sbitmap_queue *bresv = &tags->breserved_tags;
519 struct sbitmap_queue *btags = &tags->bitmap_tags;
522 * If no software queues are currently mapped to this
523 * hardware queue, there's nothing to check
525 if (!blk_mq_hw_queue_mapped(hctx))
528 if (tags->nr_reserved_tags)
529 bt_for_each(hctx, q, bresv, fn, priv, true);
530 bt_for_each(hctx, q, btags, fn, priv, false);
536 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
537 bool round_robin, int node)
539 return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
543 int blk_mq_init_bitmaps(struct sbitmap_queue *bitmap_tags,
544 struct sbitmap_queue *breserved_tags,
545 unsigned int queue_depth, unsigned int reserved,
546 int node, int alloc_policy)
548 unsigned int depth = queue_depth - reserved;
549 bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
551 if (bt_alloc(bitmap_tags, depth, round_robin, node))
553 if (bt_alloc(breserved_tags, reserved, round_robin, node))
554 goto free_bitmap_tags;
559 sbitmap_queue_free(bitmap_tags);
563 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
564 unsigned int reserved_tags,
565 int node, int alloc_policy)
567 struct blk_mq_tags *tags;
569 if (total_tags > BLK_MQ_TAG_MAX) {
570 pr_err("blk-mq: tag depth too large\n");
574 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
578 tags->nr_tags = total_tags;
579 tags->nr_reserved_tags = reserved_tags;
580 spin_lock_init(&tags->lock);
582 if (blk_mq_init_bitmaps(&tags->bitmap_tags, &tags->breserved_tags,
583 total_tags, reserved_tags, node,
591 void blk_mq_free_tags(struct blk_mq_tags *tags)
593 sbitmap_queue_free(&tags->bitmap_tags);
594 sbitmap_queue_free(&tags->breserved_tags);
598 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
599 struct blk_mq_tags **tagsptr, unsigned int tdepth,
602 struct blk_mq_tags *tags = *tagsptr;
604 if (tdepth <= tags->nr_reserved_tags)
608 * If we are allowed to grow beyond the original size, allocate
609 * a new set of tags before freeing the old one.
611 if (tdepth > tags->nr_tags) {
612 struct blk_mq_tag_set *set = hctx->queue->tag_set;
613 struct blk_mq_tags *new;
619 * We need some sort of upper limit, set it high enough that
620 * no valid use cases should require more.
622 if (tdepth > MAX_SCHED_RQ)
626 * Only the sbitmap needs resizing since we allocated the max
629 if (blk_mq_is_shared_tags(set->flags))
632 new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
636 blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
640 * Don't need (or can't) update reserved tags here, they
641 * remain static and should never need resizing.
643 sbitmap_queue_resize(&tags->bitmap_tags,
644 tdepth - tags->nr_reserved_tags);
650 void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set, unsigned int size)
652 struct blk_mq_tags *tags = set->shared_tags;
654 sbitmap_queue_resize(&tags->bitmap_tags, size - set->reserved_tags);
657 void blk_mq_tag_update_sched_shared_tags(struct request_queue *q)
659 sbitmap_queue_resize(&q->sched_shared_tags->bitmap_tags,
660 q->nr_requests - q->tag_set->reserved_tags);
664 * blk_mq_unique_tag() - return a tag that is unique queue-wide
665 * @rq: request for which to compute a unique tag
667 * The tag field in struct request is unique per hardware queue but not over
668 * all hardware queues. Hence this function that returns a tag with the
669 * hardware context index in the upper bits and the per hardware queue tag in
672 * Note: When called for a request that is queued on a non-multiqueue request
673 * queue, the hardware context index is set to zero.
675 u32 blk_mq_unique_tag(struct request *rq)
677 return (rq->mq_hctx->queue_num << BLK_MQ_UNIQUE_TAG_BITS) |
678 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
680 EXPORT_SYMBOL(blk_mq_unique_tag);