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block: store elevator state in request
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Add an rq private RQF_ELV flag, which tells the block layer that this
request was initialized on a queue that has an IO scheduler attached.
This allows for faster checking in the fast path, rather than having to
deference rq->q later on.

Elevator switching does full quiesce of the queue before detaching an
IO scheduler, so it's safe to cache this in the request itself.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Jens Axboe committed Oct 18, 2021
1 parent 90b8faa commit 2ff0682
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Showing 3 changed files with 29 additions and 20 deletions.
27 changes: 16 additions & 11 deletions block/blk-mq-sched.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,29 +56,34 @@ static inline bool
blk_mq_sched_allow_merge(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct elevator_queue *e = q->elevator;

if (e && e->type->ops.allow_merge)
return e->type->ops.allow_merge(q, rq, bio);
if (rq->rq_flags & RQF_ELV) {
struct elevator_queue *e = q->elevator;

if (e->type->ops.allow_merge)
return e->type->ops.allow_merge(q, rq, bio);
}
return true;
}

static inline void blk_mq_sched_completed_request(struct request *rq, u64 now)
{
struct elevator_queue *e = rq->q->elevator;
if (rq->rq_flags & RQF_ELV) {
struct elevator_queue *e = rq->q->elevator;

if (e && e->type->ops.completed_request)
e->type->ops.completed_request(rq, now);
if (e->type->ops.completed_request)
e->type->ops.completed_request(rq, now);
}
}

static inline void blk_mq_sched_requeue_request(struct request *rq)
{
struct request_queue *q = rq->q;
struct elevator_queue *e = q->elevator;
if (rq->rq_flags & RQF_ELV) {
struct request_queue *q = rq->q;
struct elevator_queue *e = q->elevator;

if ((rq->rq_flags & RQF_ELVPRIV) && e && e->type->ops.requeue_request)
e->type->ops.requeue_request(rq);
if ((rq->rq_flags & RQF_ELVPRIV) && e->type->ops.requeue_request)
e->type->ops.requeue_request(rq);
}
}

static inline bool blk_mq_sched_has_work(struct blk_mq_hw_ctx *hctx)
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20 changes: 11 additions & 9 deletions block/blk-mq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -306,7 +306,7 @@ void blk_mq_wake_waiters(struct request_queue *q)
*/
static inline bool blk_mq_need_time_stamp(struct request *rq)
{
return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS)) || rq->q->elevator;
return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS | RQF_ELV));
}

static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
Expand All @@ -316,9 +316,11 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
struct request *rq = tags->static_rqs[tag];

if (data->q->elevator) {
rq->rq_flags = RQF_ELV;
rq->tag = BLK_MQ_NO_TAG;
rq->internal_tag = tag;
} else {
rq->rq_flags = 0;
rq->tag = tag;
rq->internal_tag = BLK_MQ_NO_TAG;
}
Expand All @@ -327,7 +329,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
rq->q = data->q;
rq->mq_ctx = data->ctx;
rq->mq_hctx = data->hctx;
rq->rq_flags = 0;
rq->cmd_flags = data->cmd_flags;
if (data->flags & BLK_MQ_REQ_PM)
rq->rq_flags |= RQF_PM;
Expand Down Expand Up @@ -363,11 +364,11 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
data->ctx->rq_dispatched[op_is_sync(data->cmd_flags)]++;
refcount_set(&rq->ref, 1);

if (!op_is_flush(data->cmd_flags)) {
if (!op_is_flush(data->cmd_flags) && (rq->rq_flags & RQF_ELV)) {
struct elevator_queue *e = data->q->elevator;

rq->elv.icq = NULL;
if (e && e->type->ops.prepare_request) {
if (e->type->ops.prepare_request) {
if (e->type->icq_cache)
blk_mq_sched_assign_ioc(rq);

Expand Down Expand Up @@ -588,12 +589,13 @@ static void __blk_mq_free_request(struct request *rq)
void blk_mq_free_request(struct request *rq)
{
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;

if (rq->rq_flags & RQF_ELVPRIV) {
if (e && e->type->ops.finish_request)
if (rq->rq_flags & (RQF_ELVPRIV | RQF_ELV)) {
struct elevator_queue *e = q->elevator;

if (e->type->ops.finish_request)
e->type->ops.finish_request(rq);
if (rq->elv.icq) {
put_io_context(rq->elv.icq->ioc);
Expand Down Expand Up @@ -2254,7 +2256,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
goto insert;
}

if (q->elevator && !bypass_insert)
if ((rq->rq_flags & RQF_ELV) && !bypass_insert)
goto insert;

budget_token = blk_mq_get_dispatch_budget(q);
Expand Down Expand Up @@ -2492,7 +2494,7 @@ void blk_mq_submit_bio(struct bio *bio)
}

blk_add_rq_to_plug(plug, rq);
} else if (q->elevator) {
} else if (rq->rq_flags & RQF_ELV) {
/* Insert the request at the IO scheduler queue */
blk_mq_sched_insert_request(rq, false, true, true);
} else if (plug && !blk_queue_nomerges(q)) {
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2 changes: 2 additions & 0 deletions include/linux/blk-mq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,8 @@ typedef __u32 __bitwise req_flags_t;
#define RQF_MQ_POLL_SLEPT ((__force req_flags_t)(1 << 20))
/* ->timeout has been called, don't expire again */
#define RQF_TIMED_OUT ((__force req_flags_t)(1 << 21))
/* queue has elevator attached */
#define RQF_ELV ((__force req_flags_t)(1 << 22))

/* flags that prevent us from merging requests: */
#define RQF_NOMERGE_FLAGS \
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