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1/*
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
4 * is used.
5 *
6 * Copyright (C) 2013-2014 Jens Axboe
7 */
8#include <linux/kernel.h>
9#include <linux/module.h>
10
11#include <linux/blk-mq.h>
12#include "blk.h"
13#include "blk-mq.h"
14#include "blk-mq-tag.h"
15
16bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
17{
18 if (!tags)
19 return true;
20
21 return sbitmap_any_bit_clear(&tags->bitmap_tags.sb);
22}
23
24/*
25 * If a previously inactive queue goes active, bump the active user count.
26 */
27bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
28{
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);
32
33 return true;
34}
35
36/*
37 * Wakeup all potentially sleeping on tags
38 */
39void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
40{
41 sbitmap_queue_wake_all(&tags->bitmap_tags);
42 if (include_reserve)
43 sbitmap_queue_wake_all(&tags->breserved_tags);
44}
45
46/*
47 * If a previously busy queue goes inactive, potential waiters could now
48 * be allowed to queue. Wake them up and check.
49 */
50void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
51{
52 struct blk_mq_tags *tags = hctx->tags;
53
54 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
55 return;
56
57 atomic_dec(&tags->active_queues);
58
59 blk_mq_tag_wakeup_all(tags, false);
60}
61
62/*
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.
65 */
66static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
67 struct sbitmap_queue *bt)
68{
69 unsigned int depth, users;
70
71 if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
72 return true;
73 if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
74 return true;
75
76 /*
77 * Don't try dividing an ant
78 */
79 if (bt->sb.depth == 1)
80 return true;
81
82 users = atomic_read(&hctx->tags->active_queues);
83 if (!users)
84 return true;
85
86 /*
87 * Allow at least some tags
88 */
89 depth = max((bt->sb.depth + users - 1) / users, 4U);
90 return atomic_read(&hctx->nr_active) < depth;
91}
92
93static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
94 struct sbitmap_queue *bt)
95{
96 if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
97 !hctx_may_queue(data->hctx, bt))
98 return -1;
99 if (data->shallow_depth)
100 return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
101 else
102 return __sbitmap_queue_get(bt);
103}
104
105unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
106{
107 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
108 struct sbitmap_queue *bt;
109 struct sbq_wait_state *ws;
110 DEFINE_WAIT(wait);
111 unsigned int tag_offset;
112 bool drop_ctx;
113 int tag;
114
115 if (data->flags & BLK_MQ_REQ_RESERVED) {
116 if (unlikely(!tags->nr_reserved_tags)) {
117 WARN_ON_ONCE(1);
118 return BLK_MQ_TAG_FAIL;
119 }
120 bt = &tags->breserved_tags;
121 tag_offset = 0;
122 } else {
123 bt = &tags->bitmap_tags;
124 tag_offset = tags->nr_reserved_tags;
125 }
126
127 tag = __blk_mq_get_tag(data, bt);
128 if (tag != -1)
129 goto found_tag;
130
131 if (data->flags & BLK_MQ_REQ_NOWAIT)
132 return BLK_MQ_TAG_FAIL;
133
134 ws = bt_wait_ptr(bt, data->hctx);
135 drop_ctx = data->ctx == NULL;
136 do {
137 /*
138 * We're out of tags on this hardware queue, kick any
139 * pending IO submits before going to sleep waiting for
140 * some to complete.
141 */
142 blk_mq_run_hw_queue(data->hctx, false);
143
144 /*
145 * Retry tag allocation after running the hardware queue,
146 * as running the queue may also have found completions.
147 */
148 tag = __blk_mq_get_tag(data, bt);
149 if (tag != -1)
150 break;
151
152 prepare_to_wait_exclusive(&ws->wait, &wait,
153 TASK_UNINTERRUPTIBLE);
154
155 tag = __blk_mq_get_tag(data, bt);
156 if (tag != -1)
157 break;
158
159 if (data->ctx)
160 blk_mq_put_ctx(data->ctx);
161
162 io_schedule();
163
164 data->ctx = blk_mq_get_ctx(data->q);
165 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
166 tags = blk_mq_tags_from_data(data);
167 if (data->flags & BLK_MQ_REQ_RESERVED)
168 bt = &tags->breserved_tags;
169 else
170 bt = &tags->bitmap_tags;
171
172 finish_wait(&ws->wait, &wait);
173 ws = bt_wait_ptr(bt, data->hctx);
174 } while (1);
175
176 if (drop_ctx && data->ctx)
177 blk_mq_put_ctx(data->ctx);
178
179 finish_wait(&ws->wait, &wait);
180
181found_tag:
182 return tag + tag_offset;
183}
184
185void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
186 struct blk_mq_ctx *ctx, unsigned int tag)
187{
188 if (!blk_mq_tag_is_reserved(tags, tag)) {
189 const int real_tag = tag - tags->nr_reserved_tags;
190
191 BUG_ON(real_tag >= tags->nr_tags);
192 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
193 } else {
194 BUG_ON(tag >= tags->nr_reserved_tags);
195 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
196 }
197}
198
199struct bt_iter_data {
200 struct blk_mq_hw_ctx *hctx;
201 busy_iter_fn *fn;
202 void *data;
203 bool reserved;
204};
205
206static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
207{
208 struct bt_iter_data *iter_data = data;
209 struct blk_mq_hw_ctx *hctx = iter_data->hctx;
210 struct blk_mq_tags *tags = hctx->tags;
211 bool reserved = iter_data->reserved;
212 struct request *rq;
213
214 if (!reserved)
215 bitnr += tags->nr_reserved_tags;
216 rq = tags->rqs[bitnr];
217
218 /*
219 * We can hit rq == NULL here, because the tagging functions
220 * test and set the bit before assining ->rqs[].
221 */
222 if (rq && rq->q == hctx->queue)
223 iter_data->fn(hctx, rq, iter_data->data, reserved);
224 return true;
225}
226
227static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
228 busy_iter_fn *fn, void *data, bool reserved)
229{
230 struct bt_iter_data iter_data = {
231 .hctx = hctx,
232 .fn = fn,
233 .data = data,
234 .reserved = reserved,
235 };
236
237 sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
238}
239
240struct bt_tags_iter_data {
241 struct blk_mq_tags *tags;
242 busy_tag_iter_fn *fn;
243 void *data;
244 bool reserved;
245};
246
247static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
248{
249 struct bt_tags_iter_data *iter_data = data;
250 struct blk_mq_tags *tags = iter_data->tags;
251 bool reserved = iter_data->reserved;
252 struct request *rq;
253
254 if (!reserved)
255 bitnr += tags->nr_reserved_tags;
256
257 /*
258 * We can hit rq == NULL here, because the tagging functions
259 * test and set the bit before assining ->rqs[].
260 */
261 rq = tags->rqs[bitnr];
262 if (rq)
263 iter_data->fn(rq, iter_data->data, reserved);
264
265 return true;
266}
267
268static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
269 busy_tag_iter_fn *fn, void *data, bool reserved)
270{
271 struct bt_tags_iter_data iter_data = {
272 .tags = tags,
273 .fn = fn,
274 .data = data,
275 .reserved = reserved,
276 };
277
278 if (tags->rqs)
279 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
280}
281
282static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
283 busy_tag_iter_fn *fn, void *priv)
284{
285 if (tags->nr_reserved_tags)
286 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
287 bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
288}
289
290void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
291 busy_tag_iter_fn *fn, void *priv)
292{
293 int i;
294
295 for (i = 0; i < tagset->nr_hw_queues; i++) {
296 if (tagset->tags && tagset->tags[i])
297 blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
298 }
299}
300EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
301
302int blk_mq_tagset_iter(struct blk_mq_tag_set *set, void *data,
303 int (fn)(void *, struct request *))
304{
305 int i, j, ret = 0;
306
307 if (WARN_ON_ONCE(!fn))
308 goto out;
309
310 for (i = 0; i < set->nr_hw_queues; i++) {
311 struct blk_mq_tags *tags = set->tags[i];
312
313 if (!tags)
314 continue;
315
316 for (j = 0; j < tags->nr_tags; j++) {
317 if (!tags->static_rqs[j])
318 continue;
319
320 ret = fn(data, tags->static_rqs[j]);
321 if (ret)
322 goto out;
323 }
324 }
325
326out:
327 return ret;
328}
329EXPORT_SYMBOL_GPL(blk_mq_tagset_iter);
330
331void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
332 void *priv)
333{
334 struct blk_mq_hw_ctx *hctx;
335 int i;
336
337
338 queue_for_each_hw_ctx(q, hctx, i) {
339 struct blk_mq_tags *tags = hctx->tags;
340
341 /*
342 * If not software queues are currently mapped to this
343 * hardware queue, there's nothing to check
344 */
345 if (!blk_mq_hw_queue_mapped(hctx))
346 continue;
347
348 if (tags->nr_reserved_tags)
349 bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
350 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
351 }
352
353}
354
355static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
356 bool round_robin, int node)
357{
358 return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
359 node);
360}
361
362static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
363 int node, int alloc_policy)
364{
365 unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
366 bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
367
368 if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
369 goto free_tags;
370 if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
371 node))
372 goto free_bitmap_tags;
373
374 return tags;
375free_bitmap_tags:
376 sbitmap_queue_free(&tags->bitmap_tags);
377free_tags:
378 kfree(tags);
379 return NULL;
380}
381
382struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
383 unsigned int reserved_tags,
384 int node, int alloc_policy)
385{
386 struct blk_mq_tags *tags;
387
388 if (total_tags > BLK_MQ_TAG_MAX) {
389 pr_err("blk-mq: tag depth too large\n");
390 return NULL;
391 }
392
393 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
394 if (!tags)
395 return NULL;
396
397 tags->nr_tags = total_tags;
398 tags->nr_reserved_tags = reserved_tags;
399
400 return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
401}
402
403void blk_mq_free_tags(struct blk_mq_tags *tags)
404{
405 sbitmap_queue_free(&tags->bitmap_tags);
406 sbitmap_queue_free(&tags->breserved_tags);
407 kfree(tags);
408}
409
410int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
411 struct blk_mq_tags **tagsptr, unsigned int tdepth,
412 bool can_grow)
413{
414 struct blk_mq_tags *tags = *tagsptr;
415
416 if (tdepth <= tags->nr_reserved_tags)
417 return -EINVAL;
418
419 tdepth -= tags->nr_reserved_tags;
420
421 /*
422 * If we are allowed to grow beyond the original size, allocate
423 * a new set of tags before freeing the old one.
424 */
425 if (tdepth > tags->nr_tags) {
426 struct blk_mq_tag_set *set = hctx->queue->tag_set;
427 struct blk_mq_tags *new;
428 bool ret;
429
430 if (!can_grow)
431 return -EINVAL;
432
433 /*
434 * We need some sort of upper limit, set it high enough that
435 * no valid use cases should require more.
436 */
437 if (tdepth > 16 * BLKDEV_MAX_RQ)
438 return -EINVAL;
439
440 new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth, 0);
441 if (!new)
442 return -ENOMEM;
443 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
444 if (ret) {
445 blk_mq_free_rq_map(new);
446 return -ENOMEM;
447 }
448
449 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
450 blk_mq_free_rq_map(*tagsptr);
451 *tagsptr = new;
452 } else {
453 /*
454 * Don't need (or can't) update reserved tags here, they
455 * remain static and should never need resizing.
456 */
457 sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
458 }
459
460 return 0;
461}
462
463/**
464 * blk_mq_unique_tag() - return a tag that is unique queue-wide
465 * @rq: request for which to compute a unique tag
466 *
467 * The tag field in struct request is unique per hardware queue but not over
468 * all hardware queues. Hence this function that returns a tag with the
469 * hardware context index in the upper bits and the per hardware queue tag in
470 * the lower bits.
471 *
472 * Note: When called for a request that is queued on a non-multiqueue request
473 * queue, the hardware context index is set to zero.
474 */
475u32 blk_mq_unique_tag(struct request *rq)
476{
477 struct request_queue *q = rq->q;
478 struct blk_mq_hw_ctx *hctx;
479 int hwq = 0;
480
481 if (q->mq_ops) {
482 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
483 hwq = hctx->queue_num;
484 }
485
486 return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
487 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
488}
489EXPORT_SYMBOL(blk_mq_unique_tag);
1#include <linux/kernel.h>
2#include <linux/module.h>
3#include <linux/percpu_ida.h>
4
5#include <linux/blk-mq.h>
6#include "blk.h"
7#include "blk-mq.h"
8#include "blk-mq-tag.h"
9
10/*
11 * Per tagged queue (tag address space) map
12 */
13struct blk_mq_tags {
14 unsigned int nr_tags;
15 unsigned int nr_reserved_tags;
16 unsigned int nr_batch_move;
17 unsigned int nr_max_cache;
18
19 struct percpu_ida free_tags;
20 struct percpu_ida reserved_tags;
21};
22
23void blk_mq_wait_for_tags(struct blk_mq_tags *tags)
24{
25 int tag = blk_mq_get_tag(tags, __GFP_WAIT, false);
26 blk_mq_put_tag(tags, tag);
27}
28
29bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
30{
31 return !tags ||
32 percpu_ida_free_tags(&tags->free_tags, nr_cpu_ids) != 0;
33}
34
35static unsigned int __blk_mq_get_tag(struct blk_mq_tags *tags, gfp_t gfp)
36{
37 int tag;
38
39 tag = percpu_ida_alloc(&tags->free_tags, (gfp & __GFP_WAIT) ?
40 TASK_UNINTERRUPTIBLE : TASK_RUNNING);
41 if (tag < 0)
42 return BLK_MQ_TAG_FAIL;
43 return tag + tags->nr_reserved_tags;
44}
45
46static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_tags *tags,
47 gfp_t gfp)
48{
49 int tag;
50
51 if (unlikely(!tags->nr_reserved_tags)) {
52 WARN_ON_ONCE(1);
53 return BLK_MQ_TAG_FAIL;
54 }
55
56 tag = percpu_ida_alloc(&tags->reserved_tags, (gfp & __GFP_WAIT) ?
57 TASK_UNINTERRUPTIBLE : TASK_RUNNING);
58 if (tag < 0)
59 return BLK_MQ_TAG_FAIL;
60 return tag;
61}
62
63unsigned int blk_mq_get_tag(struct blk_mq_tags *tags, gfp_t gfp, bool reserved)
64{
65 if (!reserved)
66 return __blk_mq_get_tag(tags, gfp);
67
68 return __blk_mq_get_reserved_tag(tags, gfp);
69}
70
71static void __blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag)
72{
73 BUG_ON(tag >= tags->nr_tags);
74
75 percpu_ida_free(&tags->free_tags, tag - tags->nr_reserved_tags);
76}
77
78static void __blk_mq_put_reserved_tag(struct blk_mq_tags *tags,
79 unsigned int tag)
80{
81 BUG_ON(tag >= tags->nr_reserved_tags);
82
83 percpu_ida_free(&tags->reserved_tags, tag);
84}
85
86void blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag)
87{
88 if (tag >= tags->nr_reserved_tags)
89 __blk_mq_put_tag(tags, tag);
90 else
91 __blk_mq_put_reserved_tag(tags, tag);
92}
93
94static int __blk_mq_tag_iter(unsigned id, void *data)
95{
96 unsigned long *tag_map = data;
97 __set_bit(id, tag_map);
98 return 0;
99}
100
101void blk_mq_tag_busy_iter(struct blk_mq_tags *tags,
102 void (*fn)(void *, unsigned long *), void *data)
103{
104 unsigned long *tag_map;
105 size_t map_size;
106
107 map_size = ALIGN(tags->nr_tags, BITS_PER_LONG) / BITS_PER_LONG;
108 tag_map = kzalloc(map_size * sizeof(unsigned long), GFP_ATOMIC);
109 if (!tag_map)
110 return;
111
112 percpu_ida_for_each_free(&tags->free_tags, __blk_mq_tag_iter, tag_map);
113 if (tags->nr_reserved_tags)
114 percpu_ida_for_each_free(&tags->reserved_tags, __blk_mq_tag_iter,
115 tag_map);
116
117 fn(data, tag_map);
118 kfree(tag_map);
119}
120
121struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
122 unsigned int reserved_tags, int node)
123{
124 unsigned int nr_tags, nr_cache;
125 struct blk_mq_tags *tags;
126 int ret;
127
128 if (total_tags > BLK_MQ_TAG_MAX) {
129 pr_err("blk-mq: tag depth too large\n");
130 return NULL;
131 }
132
133 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
134 if (!tags)
135 return NULL;
136
137 nr_tags = total_tags - reserved_tags;
138 nr_cache = nr_tags / num_possible_cpus();
139
140 if (nr_cache < BLK_MQ_TAG_CACHE_MIN)
141 nr_cache = BLK_MQ_TAG_CACHE_MIN;
142 else if (nr_cache > BLK_MQ_TAG_CACHE_MAX)
143 nr_cache = BLK_MQ_TAG_CACHE_MAX;
144
145 tags->nr_tags = total_tags;
146 tags->nr_reserved_tags = reserved_tags;
147 tags->nr_max_cache = nr_cache;
148 tags->nr_batch_move = max(1u, nr_cache / 2);
149
150 ret = __percpu_ida_init(&tags->free_tags, tags->nr_tags -
151 tags->nr_reserved_tags,
152 tags->nr_max_cache,
153 tags->nr_batch_move);
154 if (ret)
155 goto err_free_tags;
156
157 if (reserved_tags) {
158 /*
159 * With max_cahe and batch set to 1, the allocator fallbacks to
160 * no cached. It's fine reserved tags allocation is slow.
161 */
162 ret = __percpu_ida_init(&tags->reserved_tags, reserved_tags,
163 1, 1);
164 if (ret)
165 goto err_reserved_tags;
166 }
167
168 return tags;
169
170err_reserved_tags:
171 percpu_ida_destroy(&tags->free_tags);
172err_free_tags:
173 kfree(tags);
174 return NULL;
175}
176
177void blk_mq_free_tags(struct blk_mq_tags *tags)
178{
179 percpu_ida_destroy(&tags->free_tags);
180 percpu_ida_destroy(&tags->reserved_tags);
181 kfree(tags);
182}
183
184ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
185{
186 char *orig_page = page;
187 unsigned int cpu;
188
189 if (!tags)
190 return 0;
191
192 page += sprintf(page, "nr_tags=%u, reserved_tags=%u, batch_move=%u,"
193 " max_cache=%u\n", tags->nr_tags, tags->nr_reserved_tags,
194 tags->nr_batch_move, tags->nr_max_cache);
195
196 page += sprintf(page, "nr_free=%u, nr_reserved=%u\n",
197 percpu_ida_free_tags(&tags->free_tags, nr_cpu_ids),
198 percpu_ida_free_tags(&tags->reserved_tags, nr_cpu_ids));
199
200 for_each_possible_cpu(cpu) {
201 page += sprintf(page, " cpu%02u: nr_free=%u\n", cpu,
202 percpu_ida_free_tags(&tags->free_tags, cpu));
203 }
204
205 return page - orig_page;
206}