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2023-12-14 982b8cc116118b3463d3f332581945625722acd8 
 kernel/block/blk-mq-sched.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0
12 /*
23  * blk-mq scheduling framework
34  *
....@@ -6,6 +7,7 @@
67 #include <linux/kernel.h>
78 #include <linux/module.h>
89 #include <linux/blk-mq.h>
10
+#include <linux/list_sort.h>
911 
1012 #include <trace/events/block.h>
1113 
....@@ -16,30 +18,22 @@
1618 #include "blk-mq-tag.h"
1719 #include "blk-wbt.h"
1820 
19
-void blk_mq_sched_free_hctx_data(struct request_queue *q,
20
-				 void (*exit)(struct blk_mq_hw_ctx *))
21
-{
22
-	struct blk_mq_hw_ctx *hctx;
23
-	int i;
24
-
25
-	queue_for_each_hw_ctx(q, hctx, i) {
26
-		if (exit && hctx->sched_data)
27
-			exit(hctx);
28
-		kfree(hctx->sched_data);
29
-		hctx->sched_data = NULL;
30
-	}
31
-}
32
-EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
33
-
34
-void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
21
+void blk_mq_sched_assign_ioc(struct request *rq)
3522 {
3623 	struct request_queue *q = rq->q;
37
-	struct io_context *ioc = rq_ioc(bio);
24
+	struct io_context *ioc;
3825 	struct io_cq *icq;
3926 
40
-	spin_lock_irq(q->queue_lock);
27
+	/*
28
+	 * May not have an IO context if it's a passthrough request
29
+	 */
30
+	ioc = current->io_context;
31
+	if (!ioc)
32
+		return;
33
+
34
+	spin_lock_irq(&q->queue_lock);
4135 	icq = ioc_lookup_icq(ioc, q);
42
-	spin_unlock_irq(q->queue_lock);
36
+	spin_unlock_irq(&q->queue_lock);
4337 
4438 	if (!icq) {
4539 		icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
....@@ -51,8 +45,7 @@
5145 }
5246 
5347 /*
54
- * Mark a hardware queue as needing a restart. For shared queues, maintain
55
- * a count of how many hardware queues are marked for restart.
48
+ * Mark a hardware queue as needing a restart.
5649  */
5750 void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
5851 {
....@@ -81,30 +74,85 @@
8174 	blk_mq_run_hw_queue(hctx, true);
8275 }
8376 
77
+static int sched_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
78
+{
79
+	struct request *rqa = container_of(a, struct request, queuelist);
80
+	struct request *rqb = container_of(b, struct request, queuelist);
81
+
82
+	return rqa->mq_hctx > rqb->mq_hctx;
83
+}
84
+
85
+static bool blk_mq_dispatch_hctx_list(struct list_head *rq_list)
86
+{
87
+	struct blk_mq_hw_ctx *hctx =
88
+		list_first_entry(rq_list, struct request, queuelist)->mq_hctx;
89
+	struct request *rq;
90
+	LIST_HEAD(hctx_list);
91
+	unsigned int count = 0;
92
+
93
+	list_for_each_entry(rq, rq_list, queuelist) {
94
+		if (rq->mq_hctx != hctx) {
95
+			list_cut_before(&hctx_list, rq_list, &rq->queuelist);
96
+			goto dispatch;
97
+		}
98
+		count++;
99
+	}
100
+	list_splice_tail_init(rq_list, &hctx_list);
101
+
102
+dispatch:
103
+	return blk_mq_dispatch_rq_list(hctx, &hctx_list, count);
104
+}
105
+
106
+#define BLK_MQ_BUDGET_DELAY	3		/* ms units */
107
+
84108 /*
85109  * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
86110  * its queue by itself in its completion handler, so we don't need to
87
- * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.
111
+ * restart queue if .get_budget() fails to get the budget.
112
+ *
113
+ * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to
114
+ * be run again.  This is necessary to avoid starving flushes.
88115  */
89
-static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
116
+static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
90117 {
91118 	struct request_queue *q = hctx->queue;
92119 	struct elevator_queue *e = q->elevator;
120
+	bool multi_hctxs = false, run_queue = false;
121
+	bool dispatched = false, busy = false;
122
+	unsigned int max_dispatch;
93123 	LIST_HEAD(rq_list);
124
+	int count = 0;
125
+
126
+	if (hctx->dispatch_busy)
127
+		max_dispatch = 1;
128
+	else
129
+		max_dispatch = hctx->queue->nr_requests;
94130 
95131 	do {
96132 		struct request *rq;
97133 
98
-		if (e->type->ops.mq.has_work &&
99
-				!e->type->ops.mq.has_work(hctx))
134
+		if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
100135 			break;
101136 
102
-		if (!blk_mq_get_dispatch_budget(hctx))
137
+		if (!list_empty_careful(&hctx->dispatch)) {
138
+			busy = true;
139
+			break;
140
+		}
141
+
142
+		if (!blk_mq_get_dispatch_budget(q))
103143 			break;
104144 
105
-		rq = e->type->ops.mq.dispatch_request(hctx);
145
+		rq = e->type->ops.dispatch_request(hctx);
106146 		if (!rq) {
107
-			blk_mq_put_dispatch_budget(hctx);
147
+			blk_mq_put_dispatch_budget(q);
148
+			/*
149
+			 * We're releasing without dispatching. Holding the
150
+			 * budget could have blocked any "hctx"s with the
151
+			 * same queue and if we didn't dispatch then there's
152
+			 * no guarantee anyone will kick the queue.  Kick it
153
+			 * ourselves.
154
+			 */
155
+			run_queue = true;
108156 			break;
109157 		}
110158 
....@@ -113,14 +161,57 @@
113161 		 * if this rq won't be queued to driver via .queue_rq()
114162 		 * in blk_mq_dispatch_rq_list().
115163 		 */
116
-		list_add(&rq->queuelist, &rq_list);
117
-	} while (blk_mq_dispatch_rq_list(q, &rq_list, true));
164
+		list_add_tail(&rq->queuelist, &rq_list);
165
+		if (rq->mq_hctx != hctx)
166
+			multi_hctxs = true;
167
+	} while (++count < max_dispatch);
168
+
169
+	if (!count) {
170
+		if (run_queue)
171
+			blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY);
172
+	} else if (multi_hctxs) {
173
+		/*
174
+		 * Requests from different hctx may be dequeued from some
175
+		 * schedulers, such as bfq and deadline.
176
+		 *
177
+		 * Sort the requests in the list according to their hctx,
178
+		 * dispatch batching requests from same hctx at a time.
179
+		 */
180
+		list_sort(NULL, &rq_list, sched_rq_cmp);
181
+		do {
182
+			dispatched |= blk_mq_dispatch_hctx_list(&rq_list);
183
+		} while (!list_empty(&rq_list));
184
+	} else {
185
+		dispatched = blk_mq_dispatch_rq_list(hctx, &rq_list, count);
186
+	}
187
+
188
+	if (busy)
189
+		return -EAGAIN;
190
+	return !!dispatched;
191
+}
192
+
193
+static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
194
+{
195
+	unsigned long end = jiffies + HZ;
196
+	int ret;
197
+
198
+	do {
199
+		ret = __blk_mq_do_dispatch_sched(hctx);
200
+		if (ret != 1)
201
+			break;
202
+		if (need_resched() || time_is_before_jiffies(end)) {
203
+			blk_mq_delay_run_hw_queue(hctx, 0);
204
+			break;
205
+		}
206
+	} while (1);
207
+
208
+	return ret;
118209 }
119210 
120211 static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
121212 					  struct blk_mq_ctx *ctx)
122213 {
123
-	unsigned idx = ctx->index_hw;
214
+	unsigned short idx = ctx->index_hw[hctx->type];
124215 
125216 	if (++idx == hctx->nr_ctx)
126217 		idx = 0;
....@@ -131,26 +222,42 @@
131222 /*
132223  * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
133224  * its queue by itself in its completion handler, so we don't need to
134
- * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.
225
+ * restart queue if .get_budget() fails to get the budget.
226
+ *
227
+ * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to
228
+ * be run again.  This is necessary to avoid starving flushes.
135229  */
136
-static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
230
+static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
137231 {
138232 	struct request_queue *q = hctx->queue;
139233 	LIST_HEAD(rq_list);
140234 	struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from);
235
+	int ret = 0;
236
+	struct request *rq;
141237 
142238 	do {
143
-		struct request *rq;
239
+		if (!list_empty_careful(&hctx->dispatch)) {
240
+			ret = -EAGAIN;
241
+			break;
242
+		}
144243 
145244 		if (!sbitmap_any_bit_set(&hctx->ctx_map))
146245 			break;
147246 
148
-		if (!blk_mq_get_dispatch_budget(hctx))
247
+		if (!blk_mq_get_dispatch_budget(q))
149248 			break;
150249 
151250 		rq = blk_mq_dequeue_from_ctx(hctx, ctx);
152251 		if (!rq) {
153
-			blk_mq_put_dispatch_budget(hctx);
252
+			blk_mq_put_dispatch_budget(q);
253
+			/*
254
+			 * We're releasing without dispatching. Holding the
255
+			 * budget could have blocked any "hctx"s with the
256
+			 * same queue and if we didn't dispatch then there's
257
+			 * no guarantee anyone will kick the queue.  Kick it
258
+			 * ourselves.
259
+			 */
260
+			blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY);
154261 			break;
155262 		}
156263 
....@@ -164,23 +271,19 @@
164271 		/* round robin for fair dispatch */
165272 		ctx = blk_mq_next_ctx(hctx, rq->mq_ctx);
166273 
167
-	} while (blk_mq_dispatch_rq_list(q, &rq_list, true));
274
+	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1));
168275 
169276 	WRITE_ONCE(hctx->dispatch_from, ctx);
277
+	return ret;
170278 }
171279 
172
-void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
280
+static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
173281 {
174282 	struct request_queue *q = hctx->queue;
175283 	struct elevator_queue *e = q->elevator;
176
-	const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
284
+	const bool has_sched_dispatch = e && e->type->ops.dispatch_request;
285
+	int ret = 0;
177286 	LIST_HEAD(rq_list);
178
-
179
-	/* RCU or SRCU read lock is needed before checking quiesced flag */
180
-	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
181
-		return;
182
-
183
-	hctx->run++;
184287 
185288 	/*
186289 	 * If we have previous entries on our dispatch list, grab them first for
....@@ -208,136 +311,78 @@
208311 	 */
209312 	if (!list_empty(&rq_list)) {
210313 		blk_mq_sched_mark_restart_hctx(hctx);
211
-		if (blk_mq_dispatch_rq_list(q, &rq_list, false)) {
314
+		if (blk_mq_dispatch_rq_list(hctx, &rq_list, 0)) {
212315 			if (has_sched_dispatch)
213
-				blk_mq_do_dispatch_sched(hctx);
316
+				ret = blk_mq_do_dispatch_sched(hctx);
214317 			else
215
-				blk_mq_do_dispatch_ctx(hctx);
318
+				ret = blk_mq_do_dispatch_ctx(hctx);
216319 		}
217320 	} else if (has_sched_dispatch) {
218
-		blk_mq_do_dispatch_sched(hctx);
321
+		ret = blk_mq_do_dispatch_sched(hctx);
219322 	} else if (hctx->dispatch_busy) {
220323 		/* dequeue request one by one from sw queue if queue is busy */
221
-		blk_mq_do_dispatch_ctx(hctx);
324
+		ret = blk_mq_do_dispatch_ctx(hctx);
222325 	} else {
223326 		blk_mq_flush_busy_ctxs(hctx, &rq_list);
224
-		blk_mq_dispatch_rq_list(q, &rq_list, false);
327
+		blk_mq_dispatch_rq_list(hctx, &rq_list, 0);
225328 	}
329
+
330
+	return ret;
226331 }
227332 
228
-bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
229
-			    struct request **merged_request)
333
+void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
230334 {
231
-	struct request *rq;
335
+	struct request_queue *q = hctx->queue;
232336 
233
-	switch (elv_merge(q, &rq, bio)) {
234
-	case ELEVATOR_BACK_MERGE:
235
-		if (!blk_mq_sched_allow_merge(q, rq, bio))
236
-			return false;
237
-		if (!bio_attempt_back_merge(q, rq, bio))
238
-			return false;
239
-		*merged_request = attempt_back_merge(q, rq);
240
-		if (!*merged_request)
241
-			elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
242
-		return true;
243
-	case ELEVATOR_FRONT_MERGE:
244
-		if (!blk_mq_sched_allow_merge(q, rq, bio))
245
-			return false;
246
-		if (!bio_attempt_front_merge(q, rq, bio))
247
-			return false;
248
-		*merged_request = attempt_front_merge(q, rq);
249
-		if (!*merged_request)
250
-			elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
251
-		return true;
252
-	case ELEVATOR_DISCARD_MERGE:
253
-		return bio_attempt_discard_merge(q, rq, bio);
254
-	default:
255
-		return false;
337
+	/* RCU or SRCU read lock is needed before checking quiesced flag */
338
+	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
339
+		return;
340
+
341
+	hctx->run++;
342
+
343
+	/*
344
+	 * A return of -EAGAIN is an indication that hctx->dispatch is not
345
+	 * empty and we must run again in order to avoid starving flushes.
346
+	 */
347
+	if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) {
348
+		if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN)
349
+			blk_mq_run_hw_queue(hctx, true);
256350 	}
257351 }
258
-EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
259352 
260
-/*
261
- * Iterate list of requests and see if we can merge this bio with any
262
- * of them.
263
- */
264
-bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
265
-			   struct bio *bio)
266
-{
267
-	struct request *rq;
268
-	int checked = 8;
269
-
270
-	list_for_each_entry_reverse(rq, list, queuelist) {
271
-		bool merged = false;
272
-
273
-		if (!checked--)
274
-			break;
275
-
276
-		if (!blk_rq_merge_ok(rq, bio))
277
-			continue;
278
-
279
-		switch (blk_try_merge(rq, bio)) {
280
-		case ELEVATOR_BACK_MERGE:
281
-			if (blk_mq_sched_allow_merge(q, rq, bio))
282
-				merged = bio_attempt_back_merge(q, rq, bio);
283
-			break;
284
-		case ELEVATOR_FRONT_MERGE:
285
-			if (blk_mq_sched_allow_merge(q, rq, bio))
286
-				merged = bio_attempt_front_merge(q, rq, bio);
287
-			break;
288
-		case ELEVATOR_DISCARD_MERGE:
289
-			merged = bio_attempt_discard_merge(q, rq, bio);
290
-			break;
291
-		default:
292
-			continue;
293
-		}
294
-
295
-		return merged;
296
-	}
297
-
298
-	return false;
299
-}
300
-EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
301
-
302
-/*
303
- * Reverse check our software queue for entries that we could potentially
304
- * merge with. Currently includes a hand-wavy stop count of 8, to not spend
305
- * too much time checking for merges.
306
- */
307
-static bool blk_mq_attempt_merge(struct request_queue *q,
308
-				 struct blk_mq_ctx *ctx, struct bio *bio)
309
-{
310
-	lockdep_assert_held(&ctx->lock);
311
-
312
-	if (blk_mq_bio_list_merge(q, &ctx->rq_list, bio)) {
313
-		ctx->rq_merged++;
314
-		return true;
315
-	}
316
-
317
-	return false;
318
-}
319
-
320
-bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
353
+bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
354
+		unsigned int nr_segs)
321355 {
322356 	struct elevator_queue *e = q->elevator;
323
-	struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
324
-	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
357
+	struct blk_mq_ctx *ctx;
358
+	struct blk_mq_hw_ctx *hctx;
325359 	bool ret = false;
360
+	enum hctx_type type;
326361 
327
-	if (e && e->type->ops.mq.bio_merge) {
328
-		blk_mq_put_ctx(ctx);
329
-		return e->type->ops.mq.bio_merge(hctx, bio);
362
+	if (e && e->type->ops.bio_merge)
363
+		return e->type->ops.bio_merge(q, bio, nr_segs);
364
+
365
+	ctx = blk_mq_get_ctx(q);
366
+	hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
367
+	type = hctx->type;
368
+	if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE) ||
369
+	    list_empty_careful(&ctx->rq_lists[type]))
370
+		return false;
371
+
372
+	/* default per sw-queue merge */
373
+	spin_lock(&ctx->lock);
374
+	/*
375
+	 * Reverse check our software queue for entries that we could
376
+	 * potentially merge with. Currently includes a hand-wavy stop
377
+	 * count of 8, to not spend too much time checking for merges.
378
+	 */
379
+	if (blk_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
380
+		ctx->rq_merged++;
381
+		ret = true;
330382 	}
331383 
332
-	if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
333
-			!list_empty_careful(&ctx->rq_list)) {
334
-		/* default per sw-queue merge */
335
-		spin_lock(&ctx->lock);
336
-		ret = blk_mq_attempt_merge(q, ctx, bio);
337
-		spin_unlock(&ctx->lock);
338
-	}
384
+	spin_unlock(&ctx->lock);
339385 
340
-	blk_mq_put_ctx(ctx);
341386 	return ret;
342387 }
343388 
....@@ -357,13 +402,19 @@
357402 				       bool has_sched,
358403 				       struct request *rq)
359404 {
360
-	/* dispatch flush rq directly */
361
-	if (rq->rq_flags & RQF_FLUSH_SEQ) {
362
-		spin_lock(&hctx->lock);
363
-		list_add(&rq->queuelist, &hctx->dispatch);
364
-		spin_unlock(&hctx->lock);
405
+	/*
406
+	 * dispatch flush and passthrough rq directly
407
+	 *
408
+	 * passthrough request has to be added to hctx->dispatch directly.
409
+	 * For some reason, device may be in one situation which can't
410
+	 * handle FS request, so STS_RESOURCE is always returned and the
411
+	 * FS request will be added to hctx->dispatch. However passthrough
412
+	 * request may be required at that time for fixing the problem. If
413
+	 * passthrough request is added to scheduler queue, there isn't any
414
+	 * chance to dispatch it given we prioritize requests in hctx->dispatch.
415
+	 */
416
+	if ((rq->rq_flags & RQF_FLUSH_SEQ) || blk_rq_is_passthrough(rq))
365417 		return true;
366
-	}
367418 
368419 	if (has_sched)
369420 		rq->rq_flags |= RQF_SORTED;
....@@ -377,24 +428,42 @@
377428 	struct request_queue *q = rq->q;
378429 	struct elevator_queue *e = q->elevator;
379430 	struct blk_mq_ctx *ctx = rq->mq_ctx;
380
-	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
431
+	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
381432 
382
-	/* flush rq in flush machinery need to be dispatched directly */
383
-	if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) {
384
-		blk_insert_flush(rq);
433
+	WARN_ON(e && (rq->tag != BLK_MQ_NO_TAG));
434
+
435
+	if (blk_mq_sched_bypass_insert(hctx, !!e, rq)) {
436
+		/*
437
+		 * Firstly normal IO request is inserted to scheduler queue or
438
+		 * sw queue, meantime we add flush request to dispatch queue(
439
+		 * hctx->dispatch) directly and there is at most one in-flight
440
+		 * flush request for each hw queue, so it doesn't matter to add
441
+		 * flush request to tail or front of the dispatch queue.
442
+		 *
443
+		 * Secondly in case of NCQ, flush request belongs to non-NCQ
444
+		 * command, and queueing it will fail when there is any
445
+		 * in-flight normal IO request(NCQ command). When adding flush
446
+		 * rq to the front of hctx->dispatch, it is easier to introduce
447
+		 * extra time to flush rq's latency because of S_SCHED_RESTART
448
+		 * compared with adding to the tail of dispatch queue, then
449
+		 * chance of flush merge is increased, and less flush requests
450
+		 * will be issued to controller. It is observed that ~10% time
451
+		 * is saved in blktests block/004 on disk attached to AHCI/NCQ
452
+		 * drive when adding flush rq to the front of hctx->dispatch.
453
+		 *
454
+		 * Simply queue flush rq to the front of hctx->dispatch so that
455
+		 * intensive flush workloads can benefit in case of NCQ HW.
456
+		 */
457
+		at_head = (rq->rq_flags & RQF_FLUSH_SEQ) ? true : at_head;
458
+		blk_mq_request_bypass_insert(rq, at_head, false);
385459 		goto run;
386460 	}
387461 
388
-	WARN_ON(e && (rq->tag != -1));
389
-
390
-	if (blk_mq_sched_bypass_insert(hctx, !!e, rq))
391
-		goto run;
392
-
393
-	if (e && e->type->ops.mq.insert_requests) {
462
+	if (e && e->type->ops.insert_requests) {
394463 		LIST_HEAD(list);
395464 
396465 		list_add(&rq->queuelist, &list);
397
-		e->type->ops.mq.insert_requests(hctx, &list, at_head);
466
+		e->type->ops.insert_requests(hctx, &list, at_head);
398467 	} else {
399468 		spin_lock(&ctx->lock);
400469 		__blk_mq_insert_request(hctx, rq, at_head);
....@@ -406,15 +475,23 @@
406475 		blk_mq_run_hw_queue(hctx, async);
407476 }
408477 
409
-void blk_mq_sched_insert_requests(struct request_queue *q,
478
+void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx,
410479 				  struct blk_mq_ctx *ctx,
411480 				  struct list_head *list, bool run_queue_async)
412481 {
413
-	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
414
-	struct elevator_queue *e = hctx->queue->elevator;
482
+	struct elevator_queue *e;
483
+	struct request_queue *q = hctx->queue;
415484 
416
-	if (e && e->type->ops.mq.insert_requests)
417
-		e->type->ops.mq.insert_requests(hctx, list, false);
485
+	/*
486
+	 * blk_mq_sched_insert_requests() is called from flush plug
487
+	 * context only, and hold one usage counter to prevent queue
488
+	 * from being released.
489
+	 */
490
+	percpu_ref_get(&q->q_usage_counter);
491
+
492
+	e = hctx->queue->elevator;
493
+	if (e && e->type->ops.insert_requests)
494
+		e->type->ops.insert_requests(hctx, list, false);
418495 	else {
419496 		/*
420497 		 * try to issue requests directly if the hw queue isn't
....@@ -424,21 +501,25 @@
424501 		if (!hctx->dispatch_busy && !e && !run_queue_async) {
425502 			blk_mq_try_issue_list_directly(hctx, list);
426503 			if (list_empty(list))
427
-				return;
504
+				goto out;
428505 		}
429506 		blk_mq_insert_requests(hctx, ctx, list);
430507 	}
431508 
432509 	blk_mq_run_hw_queue(hctx, run_queue_async);
510
+ out:
511
+	percpu_ref_put(&q->q_usage_counter);
433512 }
434513 
435514 static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
436515 				   struct blk_mq_hw_ctx *hctx,
437516 				   unsigned int hctx_idx)
438517 {
518
+	unsigned int flags = set->flags & ~BLK_MQ_F_TAG_HCTX_SHARED;
519
+
439520 	if (hctx->sched_tags) {
440521 		blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
441
-		blk_mq_free_rq_map(hctx->sched_tags);
522
+		blk_mq_free_rq_map(hctx->sched_tags, flags);
442523 		hctx->sched_tags = NULL;
443524 	}
444525 }
....@@ -448,10 +529,12 @@
448529 				   unsigned int hctx_idx)
449530 {
450531 	struct blk_mq_tag_set *set = q->tag_set;
532
+	/* Clear HCTX_SHARED so tags are init'ed */
533
+	unsigned int flags = set->flags & ~BLK_MQ_F_TAG_HCTX_SHARED;
451534 	int ret;
452535 
453536 	hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
454
-					       set->reserved_tags);
537
+					       set->reserved_tags, flags);
455538 	if (!hctx->sched_tags)
456539 		return -ENOMEM;
457540 
....@@ -462,14 +545,21 @@
462545 	return ret;
463546 }
464547 
548
+/* called in queue's release handler, tagset has gone away */
465549 static void blk_mq_sched_tags_teardown(struct request_queue *q)
466550 {
467
-	struct blk_mq_tag_set *set = q->tag_set;
468551 	struct blk_mq_hw_ctx *hctx;
469552 	int i;
470553 
471
-	queue_for_each_hw_ctx(q, hctx, i)
472
-		blk_mq_sched_free_tags(set, hctx, i);
554
+	queue_for_each_hw_ctx(q, hctx, i) {
555
+		/* Clear HCTX_SHARED so tags are freed */
556
+		unsigned int flags = hctx->flags & ~BLK_MQ_F_TAG_HCTX_SHARED;
557
+
558
+		if (hctx->sched_tags) {
559
+			blk_mq_free_rq_map(hctx->sched_tags, flags);
560
+			hctx->sched_tags = NULL;
561
+		}
562
+	}
473563 }
474564 
475565 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
....@@ -499,17 +589,18 @@
499589 			goto err;
500590 	}
501591 
502
-	ret = e->ops.mq.init_sched(q, e);
592
+	ret = e->ops.init_sched(q, e);
503593 	if (ret)
504594 		goto err;
505595 
506596 	blk_mq_debugfs_register_sched(q);
507597 
508598 	queue_for_each_hw_ctx(q, hctx, i) {
509
-		if (e->ops.mq.init_hctx) {
510
-			ret = e->ops.mq.init_hctx(hctx, i);
599
+		if (e->ops.init_hctx) {
600
+			ret = e->ops.init_hctx(hctx, i);
511601 			if (ret) {
512602 				eq = q->elevator;
603
+				blk_mq_sched_free_requests(q);
513604 				blk_mq_exit_sched(q, eq);
514605 				kobject_put(&eq->kobj);
515606 				return ret;
....@@ -521,9 +612,25 @@
521612 	return 0;
522613 
523614 err:
615
+	blk_mq_sched_free_requests(q);
524616 	blk_mq_sched_tags_teardown(q);
525617 	q->elevator = NULL;
526618 	return ret;
619
+}
620
+
621
+/*
622
+ * called in either blk_queue_cleanup or elevator_switch, tagset
623
+ * is required for freeing requests
624
+ */
625
+void blk_mq_sched_free_requests(struct request_queue *q)
626
+{
627
+	struct blk_mq_hw_ctx *hctx;
628
+	int i;
629
+
630
+	queue_for_each_hw_ctx(q, hctx, i) {
631
+		if (hctx->sched_tags)
632
+			blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i);
633
+	}
527634 }
528635 
529636 void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
....@@ -533,14 +640,14 @@
533640 
534641 	queue_for_each_hw_ctx(q, hctx, i) {
535642 		blk_mq_debugfs_unregister_sched_hctx(hctx);
536
-		if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
537
-			e->type->ops.mq.exit_hctx(hctx, i);
643
+		if (e->type->ops.exit_hctx && hctx->sched_data) {
644
+			e->type->ops.exit_hctx(hctx, i);
538645 			hctx->sched_data = NULL;
539646 		}
540647 	}
541648 	blk_mq_debugfs_unregister_sched(q);
542
-	if (e->type->ops.mq.exit_sched)
543
-		e->type->ops.mq.exit_sched(e);
649
+	if (e->type->ops.exit_sched)
650
+		e->type->ops.exit_sched(e);
544651 	blk_mq_sched_tags_teardown(q);
545652 	q->elevator = NULL;
546653 }