From: Christoph Hellwig <hch@lst.de>
Date: Fri, 19 May 2023 06:40:45 +0200
Subject: [PATCH] blk-mq: reflow blk_insert_flush
Git-commit: c1075e548ce6e6b5c7b71f2b05d344164ebc52bb
Patch-mainline: v6.5-rc1
References: jsc#PED-5728
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>
Acked-by: Hannes Reinecke <hare@suse.com>
---
block/blk-flush.c | 53 +++++++++++++++++++++++------------------------
1 file changed, 26 insertions(+), 27 deletions(-)
diff --git a/block/blk-flush.c b/block/blk-flush.c
index ed37d272f787..d8144f1f6fb1 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -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);
}
/**
--
2.35.3