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blk-mq: reflow blk_insert_flush 

Use a switch statement to decide on the disposition of a flush request
instead of multiple if statements, out of which one does checks that are
more complex than required.  Also warn on a malformed request early
on instead of doing a BUG_ON later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230519044050.107790-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2023-05-19 06:40:45 +02:00 committed by Jens Axboe
parent 0b573692f1
commit c1075e548c
1 changed files with 26 additions and 27 deletions
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53
block/blk-flush.c
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@ -402,6 +402,9 @@ void blk_insert_flush(struct request *rq)
struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx);
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
/* FLUSH/FUA request must never be merged */
WARN_ON_ONCE(rq->bio != rq->biotail);
/*
* @policy now records what operations need to be done. Adjust
* REQ_PREFLUSH and FUA for the driver.
@ -417,39 +420,35 @@ void blk_insert_flush(struct request *rq)
*/
rq->cmd_flags |= REQ_SYNC;
/*
* An empty flush handed down from a stacking driver may
* translate into nothing if the underlying device does not
* advertise a write-back cache. In this case, simply
* complete the request.
*/
if (!policy) {
switch (policy) {
case 0:
/*
* An empty flush handed down from a stacking driver may
* translate into nothing if the underlying device does not
* advertise a write-back cache. In this case, simply
* complete the request.
*/
blk_mq_end_request(rq, 0);
return;
}
BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */
/*
* If there's data but flush is not necessary, the request can be
* processed directly without going through flush machinery. Queue
* for normal execution.
*/
if ((policy & REQ_FSEQ_DATA) &&
!(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
case REQ_FSEQ_DATA:
/*
* If there's data, but no flush is necessary, the request can
* be processed directly without going through flush machinery.
* Queue for normal execution.
*/
blk_mq_request_bypass_insert(rq, 0);
blk_mq_run_hw_queue(hctx, false);
return;
default:
/*
* Mark the request as part of a flush sequence and submit it
* for further processing to the flush state machine.
*/
blk_rq_init_flush(rq);
spin_lock_irq(&fq->mq_flush_lock);
blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);
spin_unlock_irq(&fq->mq_flush_lock);
}
/*
* @rq should go through flush machinery. Mark it part of flush
* sequence and submit for further processing.
*/
blk_rq_init_flush(rq);
spin_lock_irq(&fq->mq_flush_lock);
blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);
spin_unlock_irq(&fq->mq_flush_lock);
}
/**