[PATCH v3 3/4] blk-iocost: account zone append completions in latency stats

[Tao Cui <cui.tao@linux.dev>]

From: Tao Cui <cuitao@kylinos.cn>

ioc_rqos_done() only accounts READ and WRITE completions, so zone
append completions are excluded from the latency window: the vrate
feedback loop cannot see ZA-induced latency, leaving it unable to
respond to device saturation caused by zone appends.  Similarly,
calc_size_vtime_cost_builtin() does not classify zone append as a
write operation.

Charging (the cost model) and feedback (the latency window) are
separate mechanisms, so this is not covered by the previous patch
that prices zone appends.

Treat zone append as WRITE for both latency accounting and cost
classification.

Fixes: 0512a75b98f8 ("block: Introduce REQ_OP_ZONE_APPEND")
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-iocost.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 7ce68e2c2e1a..ec10028249fb 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2609,6 +2609,7 @@ static void calc_size_vtime_cost_builtin(struct request *rq, struct ioc *ioc,
 	case REQ_OP_READ:
 		*costp = pages * ioc->params.lcoefs[LCOEF_RPAGE];
 		break;
+	case REQ_OP_ZONE_APPEND:
 	case REQ_OP_WRITE:
 		*costp = pages * ioc->params.lcoefs[LCOEF_WPAGE];
 		break;
@@ -2879,6 +2880,7 @@ static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
 		pidx = QOS_RLAT;
 		rw = READ;
 		break;
+	case REQ_OP_ZONE_APPEND:
 	case REQ_OP_WRITE:
 		pidx = QOS_WLAT;
 		rw = WRITE;
-- 
2.43.0