block: store elevator state in request
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>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9cff9e8..28eb1f3c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -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,
@@ -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;
}
@@ -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;
@@ -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);
@@ -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);
@@ -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);
@@ -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)) {
