1 files changed, 552 insertions, 0 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
new file mode 100644
index 0000000000..67c95f31b1
--- /dev/null
+++ b/block/blk-mq-sched.c
@@ -0,0 +1,552 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * blk-mq scheduling framework
+ *
+ * Copyright (C) 2016 Jens Axboe
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list_sort.h>
+
+#include <trace/events/block.h>
+
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-debugfs.h"
+#include "blk-mq-sched.h"
+#include "blk-wbt.h"
+
+/*
+ * Mark a hardware queue as needing a restart.
+ */
+void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
+{
+	if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
+		return;
+
+	set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_mark_restart_hctx);
+
+void __blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx)
+{
+	clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
+
+	/*
+	 * Order clearing SCHED_RESTART and list_empty_careful(&hctx->dispatch)
+	 * in blk_mq_run_hw_queue(). Its pair is the barrier in
+	 * blk_mq_dispatch_rq_list(). So dispatch code won't see SCHED_RESTART,
+	 * meantime new request added to hctx->dispatch is missed to check in
+	 * blk_mq_run_hw_queue().
+	 */
+	smp_mb();
+
+	blk_mq_run_hw_queue(hctx, true);
+}
+
+static int sched_rq_cmp(void *priv, const struct list_head *a,
+			const struct list_head *b)
+{
+	struct request *rqa = container_of(a, struct request, queuelist);
+	struct request *rqb = container_of(b, struct request, queuelist);
+
+	return rqa->mq_hctx > rqb->mq_hctx;
+}
+
+static bool blk_mq_dispatch_hctx_list(struct list_head *rq_list)
+{
+	struct blk_mq_hw_ctx *hctx =
+		list_first_entry(rq_list, struct request, queuelist)->mq_hctx;
+	struct request *rq;
+	LIST_HEAD(hctx_list);
+	unsigned int count = 0;
+
+	list_for_each_entry(rq, rq_list, queuelist) {
+		if (rq->mq_hctx != hctx) {
+			list_cut_before(&hctx_list, rq_list, &rq->queuelist);
+			goto dispatch;
+		}
+		count++;
+	}
+	list_splice_tail_init(rq_list, &hctx_list);
+
+dispatch:
+	return blk_mq_dispatch_rq_list(hctx, &hctx_list, count);
+}
+
+#define BLK_MQ_BUDGET_DELAY	3		/* ms units */
+
+/*
+ * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
+ * its queue by itself in its completion handler, so we don't need to
+ * restart queue if .get_budget() fails to get the budget.
+ *
+ * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to
+ * be run again.  This is necessary to avoid starving flushes.
+ */
+static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
+{
+	struct request_queue *q = hctx->queue;
+	struct elevator_queue *e = q->elevator;
+	bool multi_hctxs = false, run_queue = false;
+	bool dispatched = false, busy = false;
+	unsigned int max_dispatch;
+	LIST_HEAD(rq_list);
+	int count = 0;
+
+	if (hctx->dispatch_busy)
+		max_dispatch = 1;
+	else
+		max_dispatch = hctx->queue->nr_requests;
+
+	do {
+		struct request *rq;
+		int budget_token;
+
+		if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
+			break;
+
+		if (!list_empty_careful(&hctx->dispatch)) {
+			busy = true;
+			break;
+		}
+
+		budget_token = blk_mq_get_dispatch_budget(q);
+		if (budget_token < 0)
+			break;
+
+		rq = e->type->ops.dispatch_request(hctx);
+		if (!rq) {
+			blk_mq_put_dispatch_budget(q, budget_token);
+			/*
+			 * We're releasing without dispatching. Holding the
+			 * budget could have blocked any "hctx"s with the
+			 * same queue and if we didn't dispatch then there's
+			 * no guarantee anyone will kick the queue.  Kick it
+			 * ourselves.
+			 */
+			run_queue = true;
+			break;
+		}
+
+		blk_mq_set_rq_budget_token(rq, budget_token);
+
+		/*
+		 * Now this rq owns the budget which has to be released
+		 * if this rq won't be queued to driver via .queue_rq()
+		 * in blk_mq_dispatch_rq_list().
+		 */
+		list_add_tail(&rq->queuelist, &rq_list);
+		count++;
+		if (rq->mq_hctx != hctx)
+			multi_hctxs = true;
+
+		/*
+		 * If we cannot get tag for the request, stop dequeueing
+		 * requests from the IO scheduler. We are unlikely to be able
+		 * to submit them anyway and it creates false impression for
+		 * scheduling heuristics that the device can take more IO.
+		 */
+		if (!blk_mq_get_driver_tag(rq))
+			break;
+	} while (count < max_dispatch);
+
+	if (!count) {
+		if (run_queue)
+			blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY);
+	} else if (multi_hctxs) {
+		/*
+		 * Requests from different hctx may be dequeued from some
+		 * schedulers, such as bfq and deadline.
+		 *
+		 * Sort the requests in the list according to their hctx,
+		 * dispatch batching requests from same hctx at a time.
+		 */
+		list_sort(NULL, &rq_list, sched_rq_cmp);
+		do {
+			dispatched |= blk_mq_dispatch_hctx_list(&rq_list);
+		} while (!list_empty(&rq_list));
+	} else {
+		dispatched = blk_mq_dispatch_rq_list(hctx, &rq_list, count);
+	}
+
+	if (busy)
+		return -EAGAIN;
+	return !!dispatched;
+}
+
+static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
+{
+	unsigned long end = jiffies + HZ;
+	int ret;
+
+	do {
+		ret = __blk_mq_do_dispatch_sched(hctx);
+		if (ret != 1)
+			break;
+		if (need_resched() || time_is_before_jiffies(end)) {
+			blk_mq_delay_run_hw_queue(hctx, 0);
+			break;
+		}
+	} while (1);
+
+	return ret;
+}
+
+static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
+					  struct blk_mq_ctx *ctx)
+{
+	unsigned short idx = ctx->index_hw[hctx->type];
+
+	if (++idx == hctx->nr_ctx)
+		idx = 0;
+
+	return hctx->ctxs[idx];
+}
+
+/*
+ * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
+ * its queue by itself in its completion handler, so we don't need to
+ * restart queue if .get_budget() fails to get the budget.
+ *
+ * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to
+ * be run again.  This is necessary to avoid starving flushes.
+ */
+static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
+{
+	struct request_queue *q = hctx->queue;
+	LIST_HEAD(rq_list);
+	struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from);
+	int ret = 0;
+	struct request *rq;
+
+	do {
+		int budget_token;
+
+		if (!list_empty_careful(&hctx->dispatch)) {
+			ret = -EAGAIN;
+			break;
+		}
+
+		if (!sbitmap_any_bit_set(&hctx->ctx_map))
+			break;
+
+		budget_token = blk_mq_get_dispatch_budget(q);
+		if (budget_token < 0)
+			break;
+
+		rq = blk_mq_dequeue_from_ctx(hctx, ctx);
+		if (!rq) {
+			blk_mq_put_dispatch_budget(q, budget_token);
+			/*
+			 * We're releasing without dispatching. Holding the
+			 * budget could have blocked any "hctx"s with the
+			 * same queue and if we didn't dispatch then there's
+			 * no guarantee anyone will kick the queue.  Kick it
+			 * ourselves.
+			 */
+			blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY);
+			break;
+		}
+
+		blk_mq_set_rq_budget_token(rq, budget_token);
+
+		/*
+		 * Now this rq owns the budget which has to be released
+		 * if this rq won't be queued to driver via .queue_rq()
+		 * in blk_mq_dispatch_rq_list().
+		 */
+		list_add(&rq->queuelist, &rq_list);
+
+		/* round robin for fair dispatch */
+		ctx = blk_mq_next_ctx(hctx, rq->mq_ctx);
+
+	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1));
+
+	WRITE_ONCE(hctx->dispatch_from, ctx);
+	return ret;
+}
+
+static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
+{
+	bool need_dispatch = false;
+	LIST_HEAD(rq_list);
+
+	/*
+	 * If we have previous entries on our dispatch list, grab them first for
+	 * more fair dispatch.
+	 */
+	if (!list_empty_careful(&hctx->dispatch)) {
+		spin_lock(&hctx->lock);
+		if (!list_empty(&hctx->dispatch))
+			list_splice_init(&hctx->dispatch, &rq_list);
+		spin_unlock(&hctx->lock);
+	}
+
+	/*
+	 * Only ask the scheduler for requests, if we didn't have residual
+	 * requests from the dispatch list. This is to avoid the case where
+	 * we only ever dispatch a fraction of the requests available because
+	 * of low device queue depth. Once we pull requests out of the IO
+	 * scheduler, we can no longer merge or sort them. So it's best to
+	 * leave them there for as long as we can. Mark the hw queue as
+	 * needing a restart in that case.
+	 *
+	 * We want to dispatch from the scheduler if there was nothing
+	 * on the dispatch list or we were able to dispatch from the
+	 * dispatch list.
+	 */
+	if (!list_empty(&rq_list)) {
+		blk_mq_sched_mark_restart_hctx(hctx);
+		if (!blk_mq_dispatch_rq_list(hctx, &rq_list, 0))
+			return 0;
+		need_dispatch = true;
+	} else {
+		need_dispatch = hctx->dispatch_busy;
+	}
+
+	if (hctx->queue->elevator)
+		return blk_mq_do_dispatch_sched(hctx);
+
+	/* dequeue request one by one from sw queue if queue is busy */
+	if (need_dispatch)
+		return blk_mq_do_dispatch_ctx(hctx);
+	blk_mq_flush_busy_ctxs(hctx, &rq_list);
+	blk_mq_dispatch_rq_list(hctx, &rq_list, 0);
+	return 0;
+}
+
+void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
+{
+	struct request_queue *q = hctx->queue;
+
+	/* RCU or SRCU read lock is needed before checking quiesced flag */
+	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
+		return;
+
+	hctx->run++;
+
+	/*
+	 * A return of -EAGAIN is an indication that hctx->dispatch is not
+	 * empty and we must run again in order to avoid starving flushes.
+	 */
+	if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) {
+		if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN)
+			blk_mq_run_hw_queue(hctx, true);
+	}
+}
+
+bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+		unsigned int nr_segs)
+{
+	struct elevator_queue *e = q->elevator;
+	struct blk_mq_ctx *ctx;
+	struct blk_mq_hw_ctx *hctx;
+	bool ret = false;
+	enum hctx_type type;
+
+	if (e && e->type->ops.bio_merge) {
+		ret = e->type->ops.bio_merge(q, bio, nr_segs);
+		goto out_put;
+	}
+
+	ctx = blk_mq_get_ctx(q);
+	hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
+	type = hctx->type;
+	if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE) ||
+	    list_empty_careful(&ctx->rq_lists[type]))
+		goto out_put;
+
+	/* default per sw-queue merge */
+	spin_lock(&ctx->lock);
+	/*
+	 * Reverse check our software queue for entries that we could
+	 * potentially merge with. Currently includes a hand-wavy stop
+	 * count of 8, to not spend too much time checking for merges.
+	 */
+	if (blk_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs))
+		ret = true;
+
+	spin_unlock(&ctx->lock);
+out_put:
+	return ret;
+}
+
+bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq,
+				   struct list_head *free)
+{
+	return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
+
+static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
+					  struct blk_mq_hw_ctx *hctx,
+					  unsigned int hctx_idx)
+{
+	if (blk_mq_is_shared_tags(q->tag_set->flags)) {
+		hctx->sched_tags = q->sched_shared_tags;
+		return 0;
+	}
+
+	hctx->sched_tags = blk_mq_alloc_map_and_rqs(q->tag_set, hctx_idx,
+						    q->nr_requests);
+
+	if (!hctx->sched_tags)
+		return -ENOMEM;
+	return 0;
+}
+
+static void blk_mq_exit_sched_shared_tags(struct request_queue *queue)
+{
+	blk_mq_free_rq_map(queue->sched_shared_tags);
+	queue->sched_shared_tags = NULL;
+}
+
+/* called in queue's release handler, tagset has gone away */
+static void blk_mq_sched_tags_teardown(struct request_queue *q, unsigned int flags)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (hctx->sched_tags) {
+			if (!blk_mq_is_shared_tags(flags))
+				blk_mq_free_rq_map(hctx->sched_tags);
+			hctx->sched_tags = NULL;
+		}
+	}
+
+	if (blk_mq_is_shared_tags(flags))
+		blk_mq_exit_sched_shared_tags(q);
+}
+
+static int blk_mq_init_sched_shared_tags(struct request_queue *queue)
+{
+	struct blk_mq_tag_set *set = queue->tag_set;
+
+	/*
+	 * Set initial depth at max so that we don't need to reallocate for
+	 * updating nr_requests.
+	 */
+	queue->sched_shared_tags = blk_mq_alloc_map_and_rqs(set,
+						BLK_MQ_NO_HCTX_IDX,
+						MAX_SCHED_RQ);
+	if (!queue->sched_shared_tags)
+		return -ENOMEM;
+
+	blk_mq_tag_update_sched_shared_tags(queue);
+
+	return 0;
+}
+
+/* caller must have a reference to @e, will grab another one if successful */
+int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
+{
+	unsigned int flags = q->tag_set->flags;
+	struct blk_mq_hw_ctx *hctx;
+	struct elevator_queue *eq;
+	unsigned long i;
+	int ret;
+
+	/*
+	 * Default to double of smaller one between hw queue_depth and 128,
+	 * since we don't split into sync/async like the old code did.
+	 * Additionally, this is a per-hw queue depth.
+	 */
+	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
+				   BLKDEV_DEFAULT_RQ);
+
+	if (blk_mq_is_shared_tags(flags)) {
+		ret = blk_mq_init_sched_shared_tags(q);
+		if (ret)
+			return ret;
+	}
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
+		if (ret)
+			goto err_free_map_and_rqs;
+	}
+
+	ret = e->ops.init_sched(q, e);
+	if (ret)
+		goto err_free_map_and_rqs;
+
+	mutex_lock(&q->debugfs_mutex);
+	blk_mq_debugfs_register_sched(q);
+	mutex_unlock(&q->debugfs_mutex);
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (e->ops.init_hctx) {
+			ret = e->ops.init_hctx(hctx, i);
+			if (ret) {
+				eq = q->elevator;
+				blk_mq_sched_free_rqs(q);
+				blk_mq_exit_sched(q, eq);
+				kobject_put(&eq->kobj);
+				return ret;
+			}
+		}
+		mutex_lock(&q->debugfs_mutex);
+		blk_mq_debugfs_register_sched_hctx(q, hctx);
+		mutex_unlock(&q->debugfs_mutex);
+	}
+
+	return 0;
+
+err_free_map_and_rqs:
+	blk_mq_sched_free_rqs(q);
+	blk_mq_sched_tags_teardown(q, flags);
+
+	q->elevator = NULL;
+	return ret;
+}
+
+/*
+ * called in either blk_queue_cleanup or elevator_switch, tagset
+ * is required for freeing requests
+ */
+void blk_mq_sched_free_rqs(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	if (blk_mq_is_shared_tags(q->tag_set->flags)) {
+		blk_mq_free_rqs(q->tag_set, q->sched_shared_tags,
+				BLK_MQ_NO_HCTX_IDX);
+	} else {
+		queue_for_each_hw_ctx(q, hctx, i) {
+			if (hctx->sched_tags)
+				blk_mq_free_rqs(q->tag_set,
+						hctx->sched_tags, i);
+		}
+	}
+}
+
+void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+	unsigned int flags = 0;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		mutex_lock(&q->debugfs_mutex);
+		blk_mq_debugfs_unregister_sched_hctx(hctx);
+		mutex_unlock(&q->debugfs_mutex);
+
+		if (e->type->ops.exit_hctx && hctx->sched_data) {
+			e->type->ops.exit_hctx(hctx, i);
+			hctx->sched_data = NULL;
+		}
+		flags = hctx->flags;
+	}
+
+	mutex_lock(&q->debugfs_mutex);
+	blk_mq_debugfs_unregister_sched(q);
+	mutex_unlock(&q->debugfs_mutex);
+
+	if (e->type->ops.exit_sched)
+		e->type->ops.exit_sched(e);
+	blk_mq_sched_tags_teardown(q, flags);
+	q->elevator = NULL;
+}