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/*
* 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-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);
static void __blk_mq_sched_assign_ioc(struct request_queue *q,
struct request *rq,
struct bio *bio,
struct io_context *ioc)
{
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;
}
rq->elv.icq = icq;
if (!blk_mq_sched_get_rq_priv(q, rq, bio)) {
rq->rq_flags |= RQF_ELVPRIV;
get_io_context(icq->ioc);
return;
}
rq->elv.icq = NULL;
}
static void blk_mq_sched_assign_ioc(struct request_queue *q,
struct request *rq, struct bio *bio)
{
struct io_context *ioc;
ioc = rq_ioc(bio);
if (ioc)
__blk_mq_sched_assign_ioc(q, rq, bio, ioc);
}
struct request *blk_mq_sched_get_request(struct request_queue *q,
struct bio *bio,
unsigned int op,
struct blk_mq_alloc_data *data)
{
struct elevator_queue *e = q->elevator;
struct request *rq;
blk_queue_enter_live(q);
data->q = q;
if (likely(!data->ctx))
data->ctx = blk_mq_get_ctx(q);
if (likely(!data->hctx))
data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
if (e) {
data->flags |= BLK_MQ_REQ_INTERNAL;
/*
* Flush requests are special and go directly to the
* dispatch list.
*/
if (!op_is_flush(op) && e->type->ops.mq.get_request) {
rq = e->type->ops.mq.get_request(q, op, data);
if (rq)
rq->rq_flags |= RQF_QUEUED;
} else
rq = __blk_mq_alloc_request(data, op);
} else {
rq = __blk_mq_alloc_request(data, op);
}
if (rq) {
if (!op_is_flush(op)) {
rq->elv.icq = NULL;
if (e && e->type->icq_cache)
blk_mq_sched_assign_ioc(q, rq, bio);
}
data->hctx->queued++;
return rq;
}
blk_queue_exit(q);
return NULL;
}
void blk_mq_sched_put_request(struct request *rq)
{
struct request_queue *q = rq->q;
struct elevator_queue *e = q->elevator;
if (rq->rq_flags & RQF_ELVPRIV) {
blk_mq_sched_put_rq_priv(rq->q, rq);
if (rq->elv.icq) {
put_io_context(rq->elv.icq->ioc);
rq->elv.icq = NULL;
}
}
if ((rq->rq_flags & RQF_QUEUED) && e && e->type->ops.mq.put_request)
e->type->ops.mq.put_request(rq);
else
blk_mq_finish_request(rq);
}
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;
bool did_work = false;
LIST_HEAD(rq_list);
if (unlikely(blk_mq_hctx_stopped(hctx)))
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.
*/
if (!list_empty(&rq_list)) {
blk_mq_sched_mark_restart_hctx(hctx);
did_work = blk_mq_dispatch_rq_list(q, &rq_list);
} else if (!has_sched_dispatch) {
blk_mq_flush_busy_ctxs(hctx, &rq_list);
blk_mq_dispatch_rq_list(q, &rq_list);
}
/*
* We want to dispatch from the scheduler if we had no work left
* on the dispatch list, OR if we did have work but weren't able
* to make progress.
*/
if (!did_work && has_sched_dispatch) {
do {
struct request *rq;
rq = e->type->ops.mq.dispatch_request(hctx);
if (!rq)
break;
list_add(&rq->queuelist, &rq_list);
} while (blk_mq_dispatch_rq_list(q, &rq_list));
}
}
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;
default:
return false;
}
}
EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
bool __blk_mq_sched_bio_merge
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