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-rw-r--r--block/blk-mq-sched.c546
1 files changed, 546 insertions, 0 deletions
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
new file mode 100644
index 000000000..d89a757cb
--- /dev/null
+++ b/block/blk-mq-sched.c
@@ -0,0 +1,546 @@
+/*
+ * blk-mq scheduling framework
+ *
+ * Copyright (C) 2016 Jens Axboe
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/blk-mq.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-mq-tag.h"
+#include "blk-wbt.h"
+
+void blk_mq_sched_free_hctx_data(struct request_queue *q,
+ void (*exit)(struct blk_mq_hw_ctx *))
+{
+ struct blk_mq_hw_ctx *hctx;
+ int i;
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (exit && hctx->sched_data)
+ exit(hctx);
+ kfree(hctx->sched_data);
+ hctx->sched_data = NULL;
+ }
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
+
+void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
+{
+ struct request_queue *q = rq->q;
+ struct io_context *ioc = rq_ioc(bio);
+ struct io_cq *icq;
+
+ spin_lock_irq(q->queue_lock);
+ icq = ioc_lookup_icq(ioc, q);
+ spin_unlock_irq(q->queue_lock);
+
+ if (!icq) {
+ icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
+ if (!icq)
+ return;
+ }
+ get_io_context(icq->ioc);
+ rq->elv.icq = icq;
+}
+
+/*
+ * Mark a hardware queue as needing a restart. For shared queues, maintain
+ * a count of how many hardware queues are marked for 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)
+{
+ if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
+ return;
+ 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);
+}
+
+/*
+ * 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() returns BLK_STS_NO_RESOURCE.
+ */
+static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
+{
+ struct request_queue *q = hctx->queue;
+ struct elevator_queue *e = q->elevator;
+ LIST_HEAD(rq_list);
+
+ do {
+ struct request *rq;
+
+ if (e->type->ops.mq.has_work &&
+ !e->type->ops.mq.has_work(hctx))
+ break;
+
+ if (!blk_mq_get_dispatch_budget(hctx))
+ break;
+
+ rq = e->type->ops.mq.dispatch_request(hctx);
+ if (!rq) {
+ blk_mq_put_dispatch_budget(hctx);
+ break;
+ }
+
+ /*
+ * 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);
+ } while (blk_mq_dispatch_rq_list(q, &rq_list, true));
+}
+
+static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
+ struct blk_mq_ctx *ctx)
+{
+ unsigned idx = ctx->index_hw;
+
+ 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() returns BLK_STS_NO_RESOURCE.
+ */
+static void 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);
+
+ do {
+ struct request *rq;
+
+ if (!sbitmap_any_bit_set(&hctx->ctx_map))
+ break;
+
+ if (!blk_mq_get_dispatch_budget(hctx))
+ break;
+
+ rq = blk_mq_dequeue_from_ctx(hctx, ctx);
+ if (!rq) {
+ blk_mq_put_dispatch_budget(hctx);
+ break;
+ }
+
+ /*
+ * 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(q, &rq_list, true));
+
+ WRITE_ONCE(hctx->dispatch_from, ctx);
+}
+
+void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
+{
+ struct request_queue *q = hctx->queue;
+ struct elevator_queue *e = q->elevator;
+ const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
+ LIST_HEAD(rq_list);
+
+ /* 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++;
+
+ /*
+ * 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(q, &rq_list, false)) {
+ if (has_sched_dispatch)
+ blk_mq_do_dispatch_sched(hctx);
+ else
+ blk_mq_do_dispatch_ctx(hctx);
+ }
+ } else if (has_sched_dispatch) {
+ blk_mq_do_dispatch_sched(hctx);
+ } else if (hctx->dispatch_busy) {
+ /* dequeue request one by one from sw queue if queue is busy */
+ blk_mq_do_dispatch_ctx(hctx);
+ } else {
+ blk_mq_flush_busy_ctxs(hctx, &rq_list);
+ blk_mq_dispatch_rq_list(q, &rq_list, false);
+ }
+}
+
+bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
+ struct request **merged_request)
+{
+ struct request *rq;
+
+ switch (elv_merge(q, &rq, bio)) {
+ case ELEVATOR_BACK_MERGE:
+ if (!blk_mq_sched_allow_merge(q, rq, bio))
+ return false;
+ if (!bio_attempt_back_merge(q, rq, bio))
+ return false;
+ *merged_request = attempt_back_merge(q, rq);
+ if (!*merged_request)
+ elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
+ return true;
+ case ELEVATOR_FRONT_MERGE:
+ if (!blk_mq_sched_allow_merge(q, rq, bio))
+ return false;
+ if (!bio_attempt_front_merge(q, rq, bio))
+ return false;
+ *merged_request = attempt_front_merge(q, rq);
+ if (!*merged_request)
+ elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
+ return true;
+ case ELEVATOR_DISCARD_MERGE:
+ return bio_attempt_discard_merge(q, rq, bio);
+ default:
+ return false;
+ }
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
+
+/*
+ * Iterate list of requests and see if we can merge this bio with any
+ * of them.
+ */
+bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
+ struct bio *bio)
+{
+ struct request *rq;
+ int checked = 8;
+
+ list_for_each_entry_reverse(rq, list, queuelist) {
+ bool merged = false;
+
+ if (!checked--)
+ break;
+
+ if (!blk_rq_merge_ok(rq, bio))
+ continue;
+
+ switch (blk_try_merge(rq, bio)) {
+ case ELEVATOR_BACK_MERGE:
+ if (blk_mq_sched_allow_merge(q, rq, bio))
+ merged = bio_attempt_back_merge(q, rq, bio);
+ break;
+ case ELEVATOR_FRONT_MERGE:
+ if (blk_mq_sched_allow_merge(q, rq, bio))
+ merged = bio_attempt_front_merge(q, rq, bio);
+ break;
+ case ELEVATOR_DISCARD_MERGE:
+ merged = bio_attempt_discard_merge(q, rq, bio);
+ break;
+ default:
+ continue;
+ }
+
+ return merged;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
+
+/*
+ * 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.
+ */
+static bool blk_mq_attempt_merge(struct request_queue *q,
+ struct blk_mq_ctx *ctx, struct bio *bio)
+{
+ lockdep_assert_held(&ctx->lock);
+
+ if (blk_mq_bio_list_merge(q, &ctx->rq_list, bio)) {
+ ctx->rq_merged++;
+ return true;
+ }
+
+ return false;
+}
+
+bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
+{
+ struct elevator_queue *e = q->elevator;
+ struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
+ bool ret = false;
+
+ if (e && e->type->ops.mq.bio_merge) {
+ blk_mq_put_ctx(ctx);
+ return e->type->ops.mq.bio_merge(hctx, bio);
+ }
+
+ if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
+ !list_empty_careful(&ctx->rq_list)) {
+ /* default per sw-queue merge */
+ spin_lock(&ctx->lock);
+ ret = blk_mq_attempt_merge(q, ctx, bio);
+ spin_unlock(&ctx->lock);
+ }
+
+ blk_mq_put_ctx(ctx);
+ return ret;
+}
+
+bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
+{
+ return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
+
+void blk_mq_sched_request_inserted(struct request *rq)
+{
+ trace_block_rq_insert(rq->q, rq);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
+
+static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
+ bool has_sched,
+ struct request *rq)
+{
+ /* dispatch flush rq directly */
+ if (rq->rq_flags & RQF_FLUSH_SEQ) {
+ spin_lock(&hctx->lock);
+ list_add(&rq->queuelist, &hctx->dispatch);
+ spin_unlock(&hctx->lock);
+ return true;
+ }
+
+ if (has_sched)
+ rq->rq_flags |= RQF_SORTED;
+
+ return false;
+}
+
+void blk_mq_sched_insert_request(struct request *rq, bool at_head,
+ bool run_queue, bool async)
+{
+ struct request_queue *q = rq->q;
+ struct elevator_queue *e = q->elevator;
+ struct blk_mq_ctx *ctx = rq->mq_ctx;
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
+
+ /* flush rq in flush machinery need to be dispatched directly */
+ if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) {
+ blk_insert_flush(rq);
+ goto run;
+ }
+
+ WARN_ON(e && (rq->tag != -1));
+
+ if (blk_mq_sched_bypass_insert(hctx, !!e, rq))
+ goto run;
+
+ if (e && e->type->ops.mq.insert_requests) {
+ LIST_HEAD(list);
+
+ list_add(&rq->queuelist, &list);
+ e->type->ops.mq.insert_requests(hctx, &list, at_head);
+ } else {
+ spin_lock(&ctx->lock);
+ __blk_mq_insert_request(hctx, rq, at_head);
+ spin_unlock(&ctx->lock);
+ }
+
+run:
+ if (run_queue)
+ blk_mq_run_hw_queue(hctx, async);
+}
+
+void blk_mq_sched_insert_requests(struct request_queue *q,
+ struct blk_mq_ctx *ctx,
+ struct list_head *list, bool run_queue_async)
+{
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
+ struct elevator_queue *e = hctx->queue->elevator;
+
+ if (e && e->type->ops.mq.insert_requests)
+ e->type->ops.mq.insert_requests(hctx, list, false);
+ else {
+ /*
+ * try to issue requests directly if the hw queue isn't
+ * busy in case of 'none' scheduler, and this way may save
+ * us one extra enqueue & dequeue to sw queue.
+ */
+ if (!hctx->dispatch_busy && !e && !run_queue_async) {
+ blk_mq_try_issue_list_directly(hctx, list);
+ if (list_empty(list))
+ return;
+ }
+ blk_mq_insert_requests(hctx, ctx, list);
+ }
+
+ blk_mq_run_hw_queue(hctx, run_queue_async);
+}
+
+static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
+ struct blk_mq_hw_ctx *hctx,
+ unsigned int hctx_idx)
+{
+ if (hctx->sched_tags) {
+ blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
+ blk_mq_free_rq_map(hctx->sched_tags);
+ hctx->sched_tags = NULL;
+ }
+}
+
+static int blk_mq_sched_alloc_tags(struct request_queue *q,
+ struct blk_mq_hw_ctx *hctx,
+ unsigned int hctx_idx)
+{
+ struct blk_mq_tag_set *set = q->tag_set;
+ int ret;
+
+ hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
+ set->reserved_tags);
+ if (!hctx->sched_tags)
+ return -ENOMEM;
+
+ ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
+ if (ret)
+ blk_mq_sched_free_tags(set, hctx, hctx_idx);
+
+ return ret;
+}
+
+static void blk_mq_sched_tags_teardown(struct request_queue *q)
+{
+ struct blk_mq_tag_set *set = q->tag_set;
+ struct blk_mq_hw_ctx *hctx;
+ int i;
+
+ queue_for_each_hw_ctx(q, hctx, i)
+ blk_mq_sched_free_tags(set, hctx, i);
+}
+
+int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
+{
+ struct blk_mq_hw_ctx *hctx;
+ struct elevator_queue *eq;
+ unsigned int i;
+ int ret;
+
+ if (!e) {
+ q->elevator = NULL;
+ q->nr_requests = q->tag_set->queue_depth;
+ return 0;
+ }
+
+ /*
+ * 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_MAX_RQ);
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ ret = blk_mq_sched_alloc_tags(q, hctx, i);
+ if (ret)
+ goto err;
+ }
+
+ ret = e->ops.mq.init_sched(q, e);
+ if (ret)
+ goto err;
+
+ blk_mq_debugfs_register_sched(q);
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (e->ops.mq.init_hctx) {
+ ret = e->ops.mq.init_hctx(hctx, i);
+ if (ret) {
+ eq = q->elevator;
+ blk_mq_exit_sched(q, eq);
+ kobject_put(&eq->kobj);
+ return ret;
+ }
+ }
+ blk_mq_debugfs_register_sched_hctx(q, hctx);
+ }
+
+ return 0;
+
+err:
+ blk_mq_sched_tags_teardown(q);
+ q->elevator = NULL;
+ return ret;
+}
+
+void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ blk_mq_debugfs_unregister_sched_hctx(hctx);
+ if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
+ e->type->ops.mq.exit_hctx(hctx, i);
+ hctx->sched_data = NULL;
+ }
+ }
+ blk_mq_debugfs_unregister_sched(q);
+ if (e->type->ops.mq.exit_sched)
+ e->type->ops.mq.exit_sched(e);
+ blk_mq_sched_tags_teardown(q);
+ q->elevator = NULL;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-04 07:59:58 +0000