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path: root/block/blk-mq-tag.c (plain)
blob: 4bc701b32ce24c6ddda10fcbb266e5d07f41cd74
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 __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt)
94{
95 if (!hctx_may_queue(hctx, bt))
96 return -1;
97 return __sbitmap_queue_get(bt);
98}
99
100static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt,
101 struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags)
102{
103 struct sbq_wait_state *ws;
104 DEFINE_WAIT(wait);
105 int tag;
106
107 tag = __bt_get(hctx, bt);
108 if (tag != -1)
109 return tag;
110
111 if (data->flags & BLK_MQ_REQ_NOWAIT)
112 return -1;
113
114 ws = bt_wait_ptr(bt, hctx);
115 do {
116 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
117
118 tag = __bt_get(hctx, bt);
119 if (tag != -1)
120 break;
121
122 /*
123 * We're out of tags on this hardware queue, kick any
124 * pending IO submits before going to sleep waiting for
125 * some to complete. Note that hctx can be NULL here for
126 * reserved tag allocation.
127 */
128 if (hctx)
129 blk_mq_run_hw_queue(hctx, false);
130
131 /*
132 * Retry tag allocation after running the hardware queue,
133 * as running the queue may also have found completions.
134 */
135 tag = __bt_get(hctx, bt);
136 if (tag != -1)
137 break;
138
139 blk_mq_put_ctx(data->ctx);
140
141 io_schedule();
142
143 data->ctx = blk_mq_get_ctx(data->q);
144 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
145 if (data->flags & BLK_MQ_REQ_RESERVED) {
146 bt = &data->hctx->tags->breserved_tags;
147 } else {
148 hctx = data->hctx;
149 bt = &hctx->tags->bitmap_tags;
150 }
151 finish_wait(&ws->wait, &wait);
152 ws = bt_wait_ptr(bt, hctx);
153 } while (1);
154
155 finish_wait(&ws->wait, &wait);
156 return tag;
157}
158
159static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
160{
161 int tag;
162
163 tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
164 data->hctx->tags);
165 if (tag >= 0)
166 return tag + data->hctx->tags->nr_reserved_tags;
167
168 return BLK_MQ_TAG_FAIL;
169}
170
171static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
172{
173 int tag;
174
175 if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
176 WARN_ON_ONCE(1);
177 return BLK_MQ_TAG_FAIL;
178 }
179
180 tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL,
181 data->hctx->tags);
182 if (tag < 0)
183 return BLK_MQ_TAG_FAIL;
184
185 return tag;
186}
187
188unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
189{
190 if (data->flags & BLK_MQ_REQ_RESERVED)
191 return __blk_mq_get_reserved_tag(data);
192 return __blk_mq_get_tag(data);
193}
194
195void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
196 unsigned int tag)
197{
198 struct blk_mq_tags *tags = hctx->tags;
199
200 if (tag >= tags->nr_reserved_tags) {
201 const int real_tag = tag - tags->nr_reserved_tags;
202
203 BUG_ON(real_tag >= tags->nr_tags);
204 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
205 } else {
206 BUG_ON(tag >= tags->nr_reserved_tags);
207 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
208 }
209}
210
211struct bt_iter_data {
212 struct blk_mq_hw_ctx *hctx;
213 busy_iter_fn *fn;
214 void *data;
215 bool reserved;
216};
217
218static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
219{
220 struct bt_iter_data *iter_data = data;
221 struct blk_mq_hw_ctx *hctx = iter_data->hctx;
222 struct blk_mq_tags *tags = hctx->tags;
223 bool reserved = iter_data->reserved;
224 struct request *rq;
225
226 if (!reserved)
227 bitnr += tags->nr_reserved_tags;
228 rq = tags->rqs[bitnr];
229
230 if (rq->q == hctx->queue)
231 iter_data->fn(hctx, rq, iter_data->data, reserved);
232 return true;
233}
234
235static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
236 busy_iter_fn *fn, void *data, bool reserved)
237{
238 struct bt_iter_data iter_data = {
239 .hctx = hctx,
240 .fn = fn,
241 .data = data,
242 .reserved = reserved,
243 };
244
245 sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
246}
247
248struct bt_tags_iter_data {
249 struct blk_mq_tags *tags;
250 busy_tag_iter_fn *fn;
251 void *data;
252 bool reserved;
253};
254
255static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
256{
257 struct bt_tags_iter_data *iter_data = data;
258 struct blk_mq_tags *tags = iter_data->tags;
259 bool reserved = iter_data->reserved;
260 struct request *rq;
261
262 if (!reserved)
263 bitnr += tags->nr_reserved_tags;
264 rq = tags->rqs[bitnr];
265
266 iter_data->fn(rq, iter_data->data, reserved);
267 return true;
268}
269
270static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
271 busy_tag_iter_fn *fn, void *data, bool reserved)
272{
273 struct bt_tags_iter_data iter_data = {
274 .tags = tags,
275 .fn = fn,
276 .data = data,
277 .reserved = reserved,
278 };
279
280 if (tags->rqs)
281 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
282}
283
284static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
285 busy_tag_iter_fn *fn, void *priv)
286{
287 if (tags->nr_reserved_tags)
288 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
289 bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
290}
291
292void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
293 busy_tag_iter_fn *fn, void *priv)
294{
295 int i;
296
297 for (i = 0; i < tagset->nr_hw_queues; i++) {
298 if (tagset->tags && tagset->tags[i])
299 blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
300 }
301}
302EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
303
304int blk_mq_reinit_tagset(struct blk_mq_tag_set *set)
305{
306 int i, j, ret = 0;
307
308 if (!set->ops->reinit_request)
309 goto out;
310
311 for (i = 0; i < set->nr_hw_queues; i++) {
312 struct blk_mq_tags *tags = set->tags[i];
313
314 if (!tags)
315 continue;
316
317 for (j = 0; j < tags->nr_tags; j++) {
318 if (!tags->rqs[j])
319 continue;
320
321 ret = set->ops->reinit_request(set->driver_data,
322 tags->rqs[j]);
323 if (ret)
324 goto out;
325 }
326 }
327
328out:
329 return ret;
330}
331EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset);
332
333void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
334 void *priv)
335{
336 struct blk_mq_hw_ctx *hctx;
337 int i;
338
339
340 queue_for_each_hw_ctx(q, hctx, i) {
341 struct blk_mq_tags *tags = hctx->tags;
342
343 /*
344 * If not software queues are currently mapped to this
345 * hardware queue, there's nothing to check
346 */
347 if (!blk_mq_hw_queue_mapped(hctx))
348 continue;
349
350 if (tags->nr_reserved_tags)
351 bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
352 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
353 }
354
355}
356
357static unsigned int bt_unused_tags(const struct sbitmap_queue *bt)
358{
359 return bt->sb.depth - sbitmap_weight(&bt->sb);
360}
361
362static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
363 bool round_robin, int node)
364{
365 return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
366 node);
367}
368
369static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
370 int node, int alloc_policy)
371{
372 unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
373 bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
374
375 if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
376 goto free_tags;
377 if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
378 node))
379 goto free_bitmap_tags;
380
381 return tags;
382free_bitmap_tags:
383 sbitmap_queue_free(&tags->bitmap_tags);
384free_tags:
385 kfree(tags);
386 return NULL;
387}
388
389struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
390 unsigned int reserved_tags,
391 int node, int alloc_policy)
392{
393 struct blk_mq_tags *tags;
394
395 if (total_tags > BLK_MQ_TAG_MAX) {
396 pr_err("blk-mq: tag depth too large\n");
397 return NULL;
398 }
399
400 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
401 if (!tags)
402 return NULL;
403
404 tags->nr_tags = total_tags;
405 tags->nr_reserved_tags = reserved_tags;
406
407 return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
408}
409
410void blk_mq_free_tags(struct blk_mq_tags *tags)
411{
412 sbitmap_queue_free(&tags->bitmap_tags);
413 sbitmap_queue_free(&tags->breserved_tags);
414 kfree(tags);
415}
416
417int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
418{
419 tdepth -= tags->nr_reserved_tags;
420 if (tdepth > tags->nr_tags)
421 return -EINVAL;
422
423 /*
424 * Don't need (or can't) update reserved tags here, they remain
425 * static and should never need resizing.
426 */
427 sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
428
429 blk_mq_tag_wakeup_all(tags, false);
430 return 0;
431}
432
433/**
434 * blk_mq_unique_tag() - return a tag that is unique queue-wide
435 * @rq: request for which to compute a unique tag
436 *
437 * The tag field in struct request is unique per hardware queue but not over
438 * all hardware queues. Hence this function that returns a tag with the
439 * hardware context index in the upper bits and the per hardware queue tag in
440 * the lower bits.
441 *
442 * Note: When called for a request that is queued on a non-multiqueue request
443 * queue, the hardware context index is set to zero.
444 */
445u32 blk_mq_unique_tag(struct request *rq)
446{
447 struct request_queue *q = rq->q;
448 struct blk_mq_hw_ctx *hctx;
449 int hwq = 0;
450
451 if (q->mq_ops) {
452 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
453 hwq = hctx->queue_num;
454 }
455
456 return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
457 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
458}
459EXPORT_SYMBOL(blk_mq_unique_tag);
460
461ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
462{
463 char *orig_page = page;
464 unsigned int free, res;
465
466 if (!tags)
467 return 0;
468
469 page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
470 "bits_per_word=%u\n",
471 tags->nr_tags, tags->nr_reserved_tags,
472 1U << tags->bitmap_tags.sb.shift);
473
474 free = bt_unused_tags(&tags->bitmap_tags);
475 res = bt_unused_tags(&tags->breserved_tags);
476
477 page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res);
478 page += sprintf(page, "active_queues=%u\n", atomic_read(&tags->active_queues));
479
480 return page - orig_page;
481}
482
generated by cgit at 2024-05-18 16:37:56 (GMT)