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-tag.h"
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
24 bool __blk_mq_tag_busy(struct blk_mq_hw_ctx
*hctx
)
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
);
34 * Wakeup all potentially sleeping on tags
36 void blk_mq_tag_wakeup_all(struct blk_mq_tags
*tags
, bool include_reserve
)
38 sbitmap_queue_wake_all(&tags
->bitmap_tags
);
40 sbitmap_queue_wake_all(&tags
->breserved_tags
);
44 * If a previously busy queue goes inactive, potential waiters could now
45 * be allowed to queue. Wake them up and check.
47 void __blk_mq_tag_idle(struct blk_mq_hw_ctx
*hctx
)
49 struct blk_mq_tags
*tags
= hctx
->tags
;
51 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE
, &hctx
->state
))
54 atomic_dec(&tags
->active_queues
);
56 blk_mq_tag_wakeup_all(tags
, false);
60 * For shared tag users, we track the number of currently active users
61 * and attempt to provide a fair share of the tag depth for each of them.
63 static inline bool hctx_may_queue(struct blk_mq_hw_ctx
*hctx
,
64 struct sbitmap_queue
*bt
)
66 unsigned int depth
, users
;
68 if (!hctx
|| !(hctx
->flags
& BLK_MQ_F_TAG_SHARED
))
70 if (!test_bit(BLK_MQ_S_TAG_ACTIVE
, &hctx
->state
))
74 * Don't try dividing an ant
76 if (bt
->sb
.depth
== 1)
79 users
= atomic_read(&hctx
->tags
->active_queues
);
84 * Allow at least some tags
86 depth
= max((bt
->sb
.depth
+ users
- 1) / users
, 4U);
87 return atomic_read(&hctx
->nr_active
) < depth
;
90 static int __blk_mq_get_tag(struct blk_mq_alloc_data
*data
,
91 struct sbitmap_queue
*bt
)
93 if (!(data
->flags
& BLK_MQ_REQ_INTERNAL
) &&
94 !hctx_may_queue(data
->hctx
, bt
))
96 if (data
->shallow_depth
)
97 return __sbitmap_queue_get_shallow(bt
, data
->shallow_depth
);
99 return __sbitmap_queue_get(bt
);
102 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data
*data
)
104 struct blk_mq_tags
*tags
= blk_mq_tags_from_data(data
);
105 struct sbitmap_queue
*bt
;
106 struct sbq_wait_state
*ws
;
107 DEFINE_SBQ_WAIT(wait
);
108 unsigned int tag_offset
;
111 if (data
->flags
& BLK_MQ_REQ_RESERVED
) {
112 if (unlikely(!tags
->nr_reserved_tags
)) {
114 return BLK_MQ_NO_TAG
;
116 bt
= &tags
->breserved_tags
;
119 bt
= &tags
->bitmap_tags
;
120 tag_offset
= tags
->nr_reserved_tags
;
123 tag
= __blk_mq_get_tag(data
, bt
);
124 if (tag
!= BLK_MQ_NO_TAG
)
127 if (data
->flags
& BLK_MQ_REQ_NOWAIT
)
128 return BLK_MQ_NO_TAG
;
130 ws
= bt_wait_ptr(bt
, data
->hctx
);
132 struct sbitmap_queue
*bt_prev
;
135 * We're out of tags on this hardware queue, kick any
136 * pending IO submits before going to sleep waiting for
139 blk_mq_run_hw_queue(data
->hctx
, false);
142 * Retry tag allocation after running the hardware queue,
143 * as running the queue may also have found completions.
145 tag
= __blk_mq_get_tag(data
, bt
);
146 if (tag
!= BLK_MQ_NO_TAG
)
149 sbitmap_prepare_to_wait(bt
, ws
, &wait
, TASK_UNINTERRUPTIBLE
);
151 tag
= __blk_mq_get_tag(data
, bt
);
152 if (tag
!= BLK_MQ_NO_TAG
)
158 sbitmap_finish_wait(bt
, ws
, &wait
);
160 data
->ctx
= blk_mq_get_ctx(data
->q
);
161 data
->hctx
= blk_mq_map_queue(data
->q
, data
->cmd_flags
,
163 tags
= blk_mq_tags_from_data(data
);
164 if (data
->flags
& BLK_MQ_REQ_RESERVED
)
165 bt
= &tags
->breserved_tags
;
167 bt
= &tags
->bitmap_tags
;
170 * If destination hw queue is changed, fake wake up on
171 * previous queue for compensating the wake up miss, so
172 * other allocations on previous queue won't be starved.
175 sbitmap_queue_wake_up(bt_prev
);
177 ws
= bt_wait_ptr(bt
, data
->hctx
);
180 sbitmap_finish_wait(bt
, ws
, &wait
);
184 * Give up this allocation if the hctx is inactive. The caller will
185 * retry on an active hctx.
187 if (unlikely(test_bit(BLK_MQ_S_INACTIVE
, &data
->hctx
->state
))) {
188 blk_mq_put_tag(tags
, data
->ctx
, tag
+ tag_offset
);
189 return BLK_MQ_NO_TAG
;
191 return tag
+ tag_offset
;
194 void blk_mq_put_tag(struct blk_mq_tags
*tags
, struct blk_mq_ctx
*ctx
,
197 if (!blk_mq_tag_is_reserved(tags
, tag
)) {
198 const int real_tag
= tag
- tags
->nr_reserved_tags
;
200 BUG_ON(real_tag
>= tags
->nr_tags
);
201 sbitmap_queue_clear(&tags
->bitmap_tags
, real_tag
, ctx
->cpu
);
203 BUG_ON(tag
>= tags
->nr_reserved_tags
);
204 sbitmap_queue_clear(&tags
->breserved_tags
, tag
, ctx
->cpu
);
208 struct bt_iter_data
{
209 struct blk_mq_hw_ctx
*hctx
;
215 static bool bt_iter(struct sbitmap
*bitmap
, unsigned int bitnr
, void *data
)
217 struct bt_iter_data
*iter_data
= data
;
218 struct blk_mq_hw_ctx
*hctx
= iter_data
->hctx
;
219 struct blk_mq_tags
*tags
= hctx
->tags
;
220 bool reserved
= iter_data
->reserved
;
224 bitnr
+= tags
->nr_reserved_tags
;
225 rq
= tags
->rqs
[bitnr
];
228 * We can hit rq == NULL here, because the tagging functions
229 * test and set the bit before assigning ->rqs[].
231 if (rq
&& rq
->q
== hctx
->queue
)
232 return iter_data
->fn(hctx
, rq
, iter_data
->data
, reserved
);
237 * bt_for_each - iterate over the requests associated with a hardware queue
238 * @hctx: Hardware queue to examine.
239 * @bt: sbitmap to examine. This is either the breserved_tags member
240 * or the bitmap_tags member of struct blk_mq_tags.
241 * @fn: Pointer to the function that will be called for each request
242 * associated with @hctx that has been assigned a driver tag.
243 * @fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
244 * where rq is a pointer to a request. Return true to continue
245 * iterating tags, false to stop.
246 * @data: Will be passed as third argument to @fn.
247 * @reserved: Indicates whether @bt is the breserved_tags member or the
248 * bitmap_tags member of struct blk_mq_tags.
250 static void bt_for_each(struct blk_mq_hw_ctx
*hctx
, struct sbitmap_queue
*bt
,
251 busy_iter_fn
*fn
, void *data
, bool reserved
)
253 struct bt_iter_data iter_data
= {
257 .reserved
= reserved
,
260 sbitmap_for_each_set(&bt
->sb
, bt_iter
, &iter_data
);
263 struct bt_tags_iter_data
{
264 struct blk_mq_tags
*tags
;
265 busy_tag_iter_fn
*fn
;
270 #define BT_TAG_ITER_RESERVED (1 << 0)
271 #define BT_TAG_ITER_STARTED (1 << 1)
273 static bool bt_tags_iter(struct sbitmap
*bitmap
, unsigned int bitnr
, void *data
)
275 struct bt_tags_iter_data
*iter_data
= data
;
276 struct blk_mq_tags
*tags
= iter_data
->tags
;
277 bool reserved
= iter_data
->flags
& BT_TAG_ITER_RESERVED
;
281 bitnr
+= tags
->nr_reserved_tags
;
284 * We can hit rq == NULL here, because the tagging functions
285 * test and set the bit before assining ->rqs[].
287 rq
= tags
->rqs
[bitnr
];
290 if ((iter_data
->flags
& BT_TAG_ITER_STARTED
) &&
291 !blk_mq_request_started(rq
))
293 return iter_data
->fn(rq
, iter_data
->data
, reserved
);
297 * bt_tags_for_each - iterate over the requests in a tag map
298 * @tags: Tag map to iterate over.
299 * @bt: sbitmap to examine. This is either the breserved_tags member
300 * or the bitmap_tags member of struct blk_mq_tags.
301 * @fn: Pointer to the function that will be called for each started
302 * request. @fn will be called as follows: @fn(rq, @data,
303 * @reserved) where rq is a pointer to a request. Return true
304 * to continue iterating tags, false to stop.
305 * @data: Will be passed as second argument to @fn.
306 * @flags: BT_TAG_ITER_*
308 static void bt_tags_for_each(struct blk_mq_tags
*tags
, struct sbitmap_queue
*bt
,
309 busy_tag_iter_fn
*fn
, void *data
, unsigned int flags
)
311 struct bt_tags_iter_data iter_data
= {
319 sbitmap_for_each_set(&bt
->sb
, bt_tags_iter
, &iter_data
);
322 static void __blk_mq_all_tag_iter(struct blk_mq_tags
*tags
,
323 busy_tag_iter_fn
*fn
, void *priv
, unsigned int flags
)
325 WARN_ON_ONCE(flags
& BT_TAG_ITER_RESERVED
);
327 if (tags
->nr_reserved_tags
)
328 bt_tags_for_each(tags
, &tags
->breserved_tags
, fn
, priv
,
329 flags
| BT_TAG_ITER_RESERVED
);
330 bt_tags_for_each(tags
, &tags
->bitmap_tags
, fn
, priv
, flags
);
334 * blk_mq_all_tag_iter - iterate over all requests in a tag map
335 * @tags: Tag map to iterate over.
336 * @fn: Pointer to the function that will be called for each
337 * request. @fn will be called as follows: @fn(rq, @priv,
338 * reserved) where rq is a pointer to a request. 'reserved'
339 * indicates whether or not @rq is a reserved request. Return
340 * true to continue iterating tags, false to stop.
341 * @priv: Will be passed as second argument to @fn.
343 void blk_mq_all_tag_iter(struct blk_mq_tags
*tags
, busy_tag_iter_fn
*fn
,
346 return __blk_mq_all_tag_iter(tags
, fn
, priv
, 0);
350 * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
351 * @tagset: Tag set to iterate over.
352 * @fn: Pointer to the function that will be called for each started
353 * request. @fn will be called as follows: @fn(rq, @priv,
354 * reserved) where rq is a pointer to a request. 'reserved'
355 * indicates whether or not @rq is a reserved request. Return
356 * true to continue iterating tags, false to stop.
357 * @priv: Will be passed as second argument to @fn.
359 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set
*tagset
,
360 busy_tag_iter_fn
*fn
, void *priv
)
364 for (i
= 0; i
< tagset
->nr_hw_queues
; i
++) {
365 if (tagset
->tags
&& tagset
->tags
[i
])
366 __blk_mq_all_tag_iter(tagset
->tags
[i
], fn
, priv
,
367 BT_TAG_ITER_STARTED
);
370 EXPORT_SYMBOL(blk_mq_tagset_busy_iter
);
372 static bool blk_mq_tagset_count_completed_rqs(struct request
*rq
,
373 void *data
, bool reserved
)
375 unsigned *count
= data
;
377 if (blk_mq_request_completed(rq
))
383 * blk_mq_tagset_wait_completed_request - wait until all completed req's
384 * complete funtion is run
385 * @tagset: Tag set to drain completed request
387 * Note: This function has to be run after all IO queues are shutdown
389 void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set
*tagset
)
394 blk_mq_tagset_busy_iter(tagset
,
395 blk_mq_tagset_count_completed_rqs
, &count
);
401 EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request
);
404 * blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
405 * @q: Request queue to examine.
406 * @fn: Pointer to the function that will be called for each request
407 * on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
408 * reserved) where rq is a pointer to a request and hctx points
409 * to the hardware queue associated with the request. 'reserved'
410 * indicates whether or not @rq is a reserved request.
411 * @priv: Will be passed as third argument to @fn.
413 * Note: if @q->tag_set is shared with other request queues then @fn will be
414 * called for all requests on all queues that share that tag set and not only
415 * for requests associated with @q.
417 void blk_mq_queue_tag_busy_iter(struct request_queue
*q
, busy_iter_fn
*fn
,
420 struct blk_mq_hw_ctx
*hctx
;
424 * __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
425 * while the queue is frozen. So we can use q_usage_counter to avoid
426 * racing with it. __blk_mq_update_nr_hw_queues() uses
427 * synchronize_rcu() to ensure this function left the critical section
430 if (!percpu_ref_tryget(&q
->q_usage_counter
))
433 queue_for_each_hw_ctx(q
, hctx
, i
) {
434 struct blk_mq_tags
*tags
= hctx
->tags
;
437 * If no software queues are currently mapped to this
438 * hardware queue, there's nothing to check
440 if (!blk_mq_hw_queue_mapped(hctx
))
443 if (tags
->nr_reserved_tags
)
444 bt_for_each(hctx
, &tags
->breserved_tags
, fn
, priv
, true);
445 bt_for_each(hctx
, &tags
->bitmap_tags
, fn
, priv
, false);
450 static int bt_alloc(struct sbitmap_queue
*bt
, unsigned int depth
,
451 bool round_robin
, int node
)
453 return sbitmap_queue_init_node(bt
, depth
, -1, round_robin
, GFP_KERNEL
,
457 static struct blk_mq_tags
*blk_mq_init_bitmap_tags(struct blk_mq_tags
*tags
,
458 int node
, int alloc_policy
)
460 unsigned int depth
= tags
->nr_tags
- tags
->nr_reserved_tags
;
461 bool round_robin
= alloc_policy
== BLK_TAG_ALLOC_RR
;
463 if (bt_alloc(&tags
->bitmap_tags
, depth
, round_robin
, node
))
465 if (bt_alloc(&tags
->breserved_tags
, tags
->nr_reserved_tags
, round_robin
,
467 goto free_bitmap_tags
;
471 sbitmap_queue_free(&tags
->bitmap_tags
);
477 struct blk_mq_tags
*blk_mq_init_tags(unsigned int total_tags
,
478 unsigned int reserved_tags
,
479 int node
, int alloc_policy
)
481 struct blk_mq_tags
*tags
;
483 if (total_tags
> BLK_MQ_TAG_MAX
) {
484 pr_err("blk-mq: tag depth too large\n");
488 tags
= kzalloc_node(sizeof(*tags
), GFP_KERNEL
, node
);
492 tags
->nr_tags
= total_tags
;
493 tags
->nr_reserved_tags
= reserved_tags
;
495 return blk_mq_init_bitmap_tags(tags
, node
, alloc_policy
);
498 void blk_mq_free_tags(struct blk_mq_tags
*tags
)
500 sbitmap_queue_free(&tags
->bitmap_tags
);
501 sbitmap_queue_free(&tags
->breserved_tags
);
505 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx
*hctx
,
506 struct blk_mq_tags
**tagsptr
, unsigned int tdepth
,
509 struct blk_mq_tags
*tags
= *tagsptr
;
511 if (tdepth
<= tags
->nr_reserved_tags
)
515 * If we are allowed to grow beyond the original size, allocate
516 * a new set of tags before freeing the old one.
518 if (tdepth
> tags
->nr_tags
) {
519 struct blk_mq_tag_set
*set
= hctx
->queue
->tag_set
;
520 struct blk_mq_tags
*new;
527 * We need some sort of upper limit, set it high enough that
528 * no valid use cases should require more.
530 if (tdepth
> 16 * BLKDEV_MAX_RQ
)
533 new = blk_mq_alloc_rq_map(set
, hctx
->queue_num
, tdepth
,
534 tags
->nr_reserved_tags
);
537 ret
= blk_mq_alloc_rqs(set
, new, hctx
->queue_num
, tdepth
);
539 blk_mq_free_rq_map(new);
543 blk_mq_free_rqs(set
, *tagsptr
, hctx
->queue_num
);
544 blk_mq_free_rq_map(*tagsptr
);
548 * Don't need (or can't) update reserved tags here, they
549 * remain static and should never need resizing.
551 sbitmap_queue_resize(&tags
->bitmap_tags
,
552 tdepth
- tags
->nr_reserved_tags
);
559 * blk_mq_unique_tag() - return a tag that is unique queue-wide
560 * @rq: request for which to compute a unique tag
562 * The tag field in struct request is unique per hardware queue but not over
563 * all hardware queues. Hence this function that returns a tag with the
564 * hardware context index in the upper bits and the per hardware queue tag in
567 * Note: When called for a request that is queued on a non-multiqueue request
568 * queue, the hardware context index is set to zero.
570 u32
blk_mq_unique_tag(struct request
*rq
)
572 return (rq
->mq_hctx
->queue_num
<< BLK_MQ_UNIQUE_TAG_BITS
) |
573 (rq
->tag
& BLK_MQ_UNIQUE_TAG_MASK
);
575 EXPORT_SYMBOL(blk_mq_unique_tag
);