2 * Tag allocation using scalable bitmaps. Uses active queue tracking to support
3 * fairer distribution of tags between multiple submitters when a shared tag map
6 * Copyright (C) 2013-2014 Jens Axboe
8 #include <linux/kernel.h>
9 #include <linux/module.h>
11 #include <linux/blk-mq.h>
14 #include "blk-mq-tag.h"
16 bool blk_mq_has_free_tags(struct blk_mq_tags
*tags
)
21 return sbitmap_any_bit_clear(&tags
->bitmap_tags
.sb
);
25 * If a previously inactive queue goes active, bump the active user count.
27 bool __blk_mq_tag_busy(struct blk_mq_hw_ctx
*hctx
)
29 if (!test_bit(BLK_MQ_S_TAG_ACTIVE
, &hctx
->state
) &&
30 !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE
, &hctx
->state
))
31 atomic_inc(&hctx
->tags
->active_queues
);
37 * Wakeup all potentially sleeping on tags
39 void blk_mq_tag_wakeup_all(struct blk_mq_tags
*tags
, bool include_reserve
)
41 sbitmap_queue_wake_all(&tags
->bitmap_tags
);
43 sbitmap_queue_wake_all(&tags
->breserved_tags
);
47 * If a previously busy queue goes inactive, potential waiters could now
48 * be allowed to queue. Wake them up and check.
50 void __blk_mq_tag_idle(struct blk_mq_hw_ctx
*hctx
)
52 struct blk_mq_tags
*tags
= hctx
->tags
;
54 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE
, &hctx
->state
))
57 atomic_dec(&tags
->active_queues
);
59 blk_mq_tag_wakeup_all(tags
, false);
63 * For shared tag users, we track the number of currently active users
64 * and attempt to provide a fair share of the tag depth for each of them.
66 static inline bool hctx_may_queue(struct blk_mq_hw_ctx
*hctx
,
67 struct sbitmap_queue
*bt
)
69 unsigned int depth
, users
;
71 if (!hctx
|| !(hctx
->flags
& BLK_MQ_F_TAG_SHARED
))
73 if (!test_bit(BLK_MQ_S_TAG_ACTIVE
, &hctx
->state
))
77 * Don't try dividing an ant
79 if (bt
->sb
.depth
== 1)
82 users
= atomic_read(&hctx
->tags
->active_queues
);
87 * Allow at least some tags
89 depth
= max((bt
->sb
.depth
+ users
- 1) / users
, 4U);
90 return atomic_read(&hctx
->nr_active
) < depth
;
93 static int __blk_mq_get_tag(struct blk_mq_alloc_data
*data
,
94 struct sbitmap_queue
*bt
)
96 if (!(data
->flags
& BLK_MQ_REQ_INTERNAL
) &&
97 !hctx_may_queue(data
->hctx
, bt
))
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
;
108 unsigned int tag_offset
;
111 if (data
->flags
& BLK_MQ_REQ_RESERVED
) {
112 if (unlikely(!tags
->nr_reserved_tags
)) {
114 return BLK_MQ_TAG_FAIL
;
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
);
127 if (data
->flags
& BLK_MQ_REQ_NOWAIT
)
128 return BLK_MQ_TAG_FAIL
;
130 ws
= bt_wait_ptr(bt
, data
->hctx
);
132 prepare_to_wait(&ws
->wait
, &wait
, TASK_UNINTERRUPTIBLE
);
134 tag
= __blk_mq_get_tag(data
, bt
);
139 * We're out of tags on this hardware queue, kick any
140 * pending IO submits before going to sleep waiting for
143 blk_mq_run_hw_queue(data
->hctx
, false);
146 * Retry tag allocation after running the hardware queue,
147 * as running the queue may also have found completions.
149 tag
= __blk_mq_get_tag(data
, bt
);
153 blk_mq_put_ctx(data
->ctx
);
157 data
->ctx
= blk_mq_get_ctx(data
->q
);
158 data
->hctx
= blk_mq_map_queue(data
->q
, data
->ctx
->cpu
);
159 tags
= blk_mq_tags_from_data(data
);
160 if (data
->flags
& BLK_MQ_REQ_RESERVED
)
161 bt
= &tags
->breserved_tags
;
163 bt
= &tags
->bitmap_tags
;
165 finish_wait(&ws
->wait
, &wait
);
166 ws
= bt_wait_ptr(bt
, data
->hctx
);
169 finish_wait(&ws
->wait
, &wait
);
172 return tag
+ tag_offset
;
175 void blk_mq_put_tag(struct blk_mq_hw_ctx
*hctx
, struct blk_mq_tags
*tags
,
176 struct blk_mq_ctx
*ctx
, unsigned int tag
)
178 if (tag
>= tags
->nr_reserved_tags
) {
179 const int real_tag
= tag
- tags
->nr_reserved_tags
;
181 BUG_ON(real_tag
>= tags
->nr_tags
);
182 sbitmap_queue_clear(&tags
->bitmap_tags
, real_tag
, ctx
->cpu
);
184 BUG_ON(tag
>= tags
->nr_reserved_tags
);
185 sbitmap_queue_clear(&tags
->breserved_tags
, tag
, ctx
->cpu
);
189 struct bt_iter_data
{
190 struct blk_mq_hw_ctx
*hctx
;
196 static bool bt_iter(struct sbitmap
*bitmap
, unsigned int bitnr
, void *data
)
198 struct bt_iter_data
*iter_data
= data
;
199 struct blk_mq_hw_ctx
*hctx
= iter_data
->hctx
;
200 struct blk_mq_tags
*tags
= hctx
->tags
;
201 bool reserved
= iter_data
->reserved
;
205 bitnr
+= tags
->nr_reserved_tags
;
206 rq
= tags
->rqs
[bitnr
];
208 if (rq
->q
== hctx
->queue
)
209 iter_data
->fn(hctx
, rq
, iter_data
->data
, reserved
);
213 static void bt_for_each(struct blk_mq_hw_ctx
*hctx
, struct sbitmap_queue
*bt
,
214 busy_iter_fn
*fn
, void *data
, bool reserved
)
216 struct bt_iter_data iter_data
= {
220 .reserved
= reserved
,
223 sbitmap_for_each_set(&bt
->sb
, bt_iter
, &iter_data
);
226 struct bt_tags_iter_data
{
227 struct blk_mq_tags
*tags
;
228 busy_tag_iter_fn
*fn
;
233 static bool bt_tags_iter(struct sbitmap
*bitmap
, unsigned int bitnr
, void *data
)
235 struct bt_tags_iter_data
*iter_data
= data
;
236 struct blk_mq_tags
*tags
= iter_data
->tags
;
237 bool reserved
= iter_data
->reserved
;
241 bitnr
+= tags
->nr_reserved_tags
;
242 rq
= tags
->rqs
[bitnr
];
244 iter_data
->fn(rq
, iter_data
->data
, reserved
);
248 static void bt_tags_for_each(struct blk_mq_tags
*tags
, struct sbitmap_queue
*bt
,
249 busy_tag_iter_fn
*fn
, void *data
, bool reserved
)
251 struct bt_tags_iter_data iter_data
= {
255 .reserved
= reserved
,
259 sbitmap_for_each_set(&bt
->sb
, bt_tags_iter
, &iter_data
);
262 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags
*tags
,
263 busy_tag_iter_fn
*fn
, void *priv
)
265 if (tags
->nr_reserved_tags
)
266 bt_tags_for_each(tags
, &tags
->breserved_tags
, fn
, priv
, true);
267 bt_tags_for_each(tags
, &tags
->bitmap_tags
, fn
, priv
, false);
270 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set
*tagset
,
271 busy_tag_iter_fn
*fn
, void *priv
)
275 for (i
= 0; i
< tagset
->nr_hw_queues
; i
++) {
276 if (tagset
->tags
&& tagset
->tags
[i
])
277 blk_mq_all_tag_busy_iter(tagset
->tags
[i
], fn
, priv
);
280 EXPORT_SYMBOL(blk_mq_tagset_busy_iter
);
282 int blk_mq_reinit_tagset(struct blk_mq_tag_set
*set
)
286 if (!set
->ops
->reinit_request
)
289 for (i
= 0; i
< set
->nr_hw_queues
; i
++) {
290 struct blk_mq_tags
*tags
= set
->tags
[i
];
292 for (j
= 0; j
< tags
->nr_tags
; j
++) {
293 if (!tags
->static_rqs
[j
])
296 ret
= set
->ops
->reinit_request(set
->driver_data
,
297 tags
->static_rqs
[j
]);
306 EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset
);
308 void blk_mq_queue_tag_busy_iter(struct request_queue
*q
, busy_iter_fn
*fn
,
311 struct blk_mq_hw_ctx
*hctx
;
315 queue_for_each_hw_ctx(q
, hctx
, i
) {
316 struct blk_mq_tags
*tags
= hctx
->tags
;
319 * If not software queues are currently mapped to this
320 * hardware queue, there's nothing to check
322 if (!blk_mq_hw_queue_mapped(hctx
))
325 if (tags
->nr_reserved_tags
)
326 bt_for_each(hctx
, &tags
->breserved_tags
, fn
, priv
, true);
327 bt_for_each(hctx
, &tags
->bitmap_tags
, fn
, priv
, false);
332 static unsigned int bt_unused_tags(const struct sbitmap_queue
*bt
)
334 return bt
->sb
.depth
- sbitmap_weight(&bt
->sb
);
337 static int bt_alloc(struct sbitmap_queue
*bt
, unsigned int depth
,
338 bool round_robin
, int node
)
340 return sbitmap_queue_init_node(bt
, depth
, -1, round_robin
, GFP_KERNEL
,
344 static struct blk_mq_tags
*blk_mq_init_bitmap_tags(struct blk_mq_tags
*tags
,
345 int node
, int alloc_policy
)
347 unsigned int depth
= tags
->nr_tags
- tags
->nr_reserved_tags
;
348 bool round_robin
= alloc_policy
== BLK_TAG_ALLOC_RR
;
350 if (bt_alloc(&tags
->bitmap_tags
, depth
, round_robin
, node
))
352 if (bt_alloc(&tags
->breserved_tags
, tags
->nr_reserved_tags
, round_robin
,
354 goto free_bitmap_tags
;
358 sbitmap_queue_free(&tags
->bitmap_tags
);
364 struct blk_mq_tags
*blk_mq_init_tags(unsigned int total_tags
,
365 unsigned int reserved_tags
,
366 int node
, int alloc_policy
)
368 struct blk_mq_tags
*tags
;
370 if (total_tags
> BLK_MQ_TAG_MAX
) {
371 pr_err("blk-mq: tag depth too large\n");
375 tags
= kzalloc_node(sizeof(*tags
), GFP_KERNEL
, node
);
379 tags
->nr_tags
= total_tags
;
380 tags
->nr_reserved_tags
= reserved_tags
;
382 return blk_mq_init_bitmap_tags(tags
, node
, alloc_policy
);
385 void blk_mq_free_tags(struct blk_mq_tags
*tags
)
387 sbitmap_queue_free(&tags
->bitmap_tags
);
388 sbitmap_queue_free(&tags
->breserved_tags
);
392 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx
*hctx
,
393 struct blk_mq_tags
**tagsptr
, unsigned int tdepth
,
396 struct blk_mq_tags
*tags
= *tagsptr
;
398 if (tdepth
<= tags
->nr_reserved_tags
)
401 tdepth
-= tags
->nr_reserved_tags
;
404 * If we are allowed to grow beyond the original size, allocate
405 * a new set of tags before freeing the old one.
407 if (tdepth
> tags
->nr_tags
) {
408 struct blk_mq_tag_set
*set
= hctx
->queue
->tag_set
;
409 struct blk_mq_tags
*new;
416 * We need some sort of upper limit, set it high enough that
417 * no valid use cases should require more.
419 if (tdepth
> 16 * BLKDEV_MAX_RQ
)
422 new = blk_mq_alloc_rq_map(set
, hctx
->queue_num
, tdepth
, 0);
425 ret
= blk_mq_alloc_rqs(set
, new, hctx
->queue_num
, tdepth
);
427 blk_mq_free_rq_map(new);
431 blk_mq_free_rqs(set
, *tagsptr
, hctx
->queue_num
);
432 blk_mq_free_rq_map(*tagsptr
);
436 * Don't need (or can't) update reserved tags here, they
437 * remain static and should never need resizing.
439 sbitmap_queue_resize(&tags
->bitmap_tags
, tdepth
);
446 * blk_mq_unique_tag() - return a tag that is unique queue-wide
447 * @rq: request for which to compute a unique tag
449 * The tag field in struct request is unique per hardware queue but not over
450 * all hardware queues. Hence this function that returns a tag with the
451 * hardware context index in the upper bits and the per hardware queue tag in
454 * Note: When called for a request that is queued on a non-multiqueue request
455 * queue, the hardware context index is set to zero.
457 u32
blk_mq_unique_tag(struct request
*rq
)
459 struct request_queue
*q
= rq
->q
;
460 struct blk_mq_hw_ctx
*hctx
;
464 hctx
= blk_mq_map_queue(q
, rq
->mq_ctx
->cpu
);
465 hwq
= hctx
->queue_num
;
468 return (hwq
<< BLK_MQ_UNIQUE_TAG_BITS
) |
469 (rq
->tag
& BLK_MQ_UNIQUE_TAG_MASK
);
471 EXPORT_SYMBOL(blk_mq_unique_tag
);
473 ssize_t
blk_mq_tag_sysfs_show(struct blk_mq_tags
*tags
, char *page
)
475 char *orig_page
= page
;
476 unsigned int free
, res
;
481 page
+= sprintf(page
, "nr_tags=%u, reserved_tags=%u, "
482 "bits_per_word=%u\n",
483 tags
->nr_tags
, tags
->nr_reserved_tags
,
484 1U << tags
->bitmap_tags
.sb
.shift
);
486 free
= bt_unused_tags(&tags
->bitmap_tags
);
487 res
= bt_unused_tags(&tags
->breserved_tags
);
489 page
+= sprintf(page
, "nr_free=%u, nr_reserved=%u\n", free
, res
);
490 page
+= sprintf(page
, "active_queues=%u\n", atomic_read(&tags
->active_queues
));
492 return page
- orig_page
;