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blk-mq: streamline blk_mq_make_request

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Turn the different ways of merging or issuing I/O into a series of if/else
statements instead of the current maze of gotos.  Note that this means we
pin the CPU a little longer for some cases as the CTX put is moved to
common code at the end of the function.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2017-03-22 15:01:53 -04:00 committed by Jens Axboe
parent 2299722c4b
commit a4d907b6a3
1 changed files with 16 additions and 37 deletions
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53
block/blk-mq.c
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@ -1531,16 +1531,17 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
cookie = request_to_qc_t(data.hctx, rq);
if (unlikely(is_flush_fua)) {
if (q->elevator)
goto elv_insert;
blk_mq_bio_to_request(rq, bio);
blk_insert_flush(rq);
goto run_queue;
}
plug = current->plug;
if (plug && q->nr_hw_queues == 1) {
if (unlikely(is_flush_fua)) {
blk_mq_bio_to_request(rq, bio);
if (q->elevator) {
blk_mq_sched_insert_request(rq, false, true, true,
true);
} else {
blk_insert_flush(rq);
blk_mq_run_hw_queue(data.hctx, true);
}
} else if (plug && q->nr_hw_queues == 1) {
struct request *last = NULL;
blk_mq_bio_to_request(rq, bio);
@ -1559,8 +1560,6 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
else
last = list_entry_rq(plug->mq_list.prev);
blk_mq_put_ctx(data.ctx);
if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
blk_flush_plug_list(plug, false);
@ -1568,7 +1567,6 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
}
list_add_tail(&rq->queuelist, &plug->mq_list);
goto done;
} else if (plug && !blk_queue_nomerges(q)) {
blk_mq_bio_to_request(rq, bio);
@ -1585,39 +1583,20 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
list_del_init(&same_queue_rq->queuelist);
list_add_tail(&rq->queuelist, &plug->mq_list);
blk_mq_put_ctx(data.ctx);
if (same_queue_rq)
blk_mq_try_issue_directly(data.hctx, same_queue_rq,
&cookie);
goto done;
} else if (is_sync) {
} else if (q->nr_hw_queues > 1 && is_sync) {
blk_mq_bio_to_request(rq, bio);
blk_mq_put_ctx(data.ctx);
blk_mq_try_issue_directly(data.hctx, rq, &cookie);
goto done;
} else if (q->elevator) {
blk_mq_bio_to_request(rq, bio);
blk_mq_sched_insert_request(rq, false, true, true, true);
} else if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
blk_mq_run_hw_queue(data.hctx, true);
}
if (q->elevator) {
elv_insert:
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
blk_mq_sched_insert_request(rq, false, true,
!is_sync || is_flush_fua, true);
goto done;
}
if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
/*
* For a SYNC request, send it to the hardware immediately. For
* an ASYNC request, just ensure that we run it later on. The
* latter allows for merging opportunities and more efficient
* dispatching.
*/
run_queue:
blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
}
blk_mq_put_ctx(data.ctx);
done:
return cookie;
}