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Linux/block/blk-mq-tag.c

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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 
 16 bool 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  */
 27 bool __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  */
 39 void 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  */
 50 void __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  */
 66 static 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 
 93 static 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 
105 unsigned 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 
181 found_tag:
182         return tag + tag_offset;
183 }
184 
185 void 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 
199 struct bt_iter_data {
200         struct blk_mq_hw_ctx *hctx;
201         busy_iter_fn *fn;
202         void *data;
203         bool reserved;
204 };
205 
206 static 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 
227 static 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 
240 struct bt_tags_iter_data {
241         struct blk_mq_tags *tags;
242         busy_tag_iter_fn *fn;
243         void *data;
244         bool reserved;
245 };
246 
247 static 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 
268 static 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 
282 static 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 
290 void 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 }
300 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
301 
302 int 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 
326 out:
327         return ret;
328 }
329 EXPORT_SYMBOL_GPL(blk_mq_tagset_iter);
330 
331 void 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 
355 static 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 
362 static 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;
375 free_bitmap_tags:
376         sbitmap_queue_free(&tags->bitmap_tags);
377 free_tags:
378         kfree(tags);
379         return NULL;
380 }
381 
382 struct 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 
403 void 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 
410 int 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  */
475 u32 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 }
489 EXPORT_SYMBOL(blk_mq_unique_tag);
490 

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