linux/block/blk-mq-sched.c

582 lines
14 KiB
C

// 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/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 request_queue *q = rq->q;
struct io_context *ioc;
struct io_cq *icq;
/*
* May not have an IO context if it's a passthrough request
*/
ioc = current->io_context;
if (!ioc)
return;
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);
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.has_work && !e->type->ops.has_work(hctx))
break;
if (!blk_mq_get_dispatch_budget(hctx))
break;
rq = e->type->ops.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 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() 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.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,
unsigned int nr_segs, 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(rq, bio, nr_segs))
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(rq, bio, nr_segs))
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, unsigned int nr_segs)
{
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(rq, bio,
nr_segs);
break;
case ELEVATOR_FRONT_MERGE:
if (blk_mq_sched_allow_merge(q, rq, bio))
merged = bio_attempt_front_merge(rq, bio,
nr_segs);
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_hw_ctx *hctx,
struct blk_mq_ctx *ctx, struct bio *bio,
unsigned int nr_segs)
{
enum hctx_type type = hctx->type;
lockdep_assert_held(&ctx->lock);
if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
ctx->rq_merged++;
return true;
}
return false;
}
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 = blk_mq_get_ctx(q);
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
bool ret = false;
enum hctx_type type;
if (e && e->type->ops.bio_merge)
return e->type->ops.bio_merge(hctx, bio, nr_segs);
type = hctx->type;
if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
!list_empty_careful(&ctx->rq_lists[type])) {
/* default per sw-queue merge */
spin_lock(&ctx->lock);
ret = blk_mq_attempt_merge(q, hctx, ctx, bio, nr_segs);
spin_unlock(&ctx->lock);
}
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 = rq->mq_hctx;
/* 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.insert_requests) {
LIST_HEAD(list);
list_add(&rq->queuelist, &list);
e->type->ops.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 blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx,
struct list_head *list, bool run_queue_async)
{
struct elevator_queue *e;
struct request_queue *q = hctx->queue;
/*
* blk_mq_sched_insert_requests() is called from flush plug
* context only, and hold one usage counter to prevent queue
* from being released.
*/
percpu_ref_get(&q->q_usage_counter);
e = hctx->queue->elevator;
if (e && e->type->ops.insert_requests)
e->type->ops.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))
goto out;
}
blk_mq_insert_requests(hctx, ctx, list);
}
blk_mq_run_hw_queue(hctx, run_queue_async);
out:
percpu_ref_put(&q->q_usage_counter);
}
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;
}
/* called in queue's release handler, tagset has gone away */
static void blk_mq_sched_tags_teardown(struct request_queue *q)
{
struct blk_mq_hw_ctx *hctx;
int i;
queue_for_each_hw_ctx(q, hctx, i) {
if (hctx->sched_tags) {
blk_mq_free_rq_map(hctx->sched_tags);
hctx->sched_tags = NULL;
}
}
}
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.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.init_hctx) {
ret = e->ops.init_hctx(hctx, i);
if (ret) {
eq = q->elevator;
blk_mq_sched_free_requests(q);
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_free_requests(q);
blk_mq_sched_tags_teardown(q);
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_requests(struct request_queue *q)
{
struct blk_mq_hw_ctx *hctx;
int i;
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 int i;
queue_for_each_hw_ctx(q, hctx, i) {
blk_mq_debugfs_unregister_sched_hctx(hctx);
if (e->type->ops.exit_hctx && hctx->sched_data) {
e->type->ops.exit_hctx(hctx, i);
hctx->sched_data = NULL;
}
}
blk_mq_debugfs_unregister_sched(q);
if (e->type->ops.exit_sched)
e->type->ops.exit_sched(e);
blk_mq_sched_tags_teardown(q);
q->elevator = NULL;
}