[PATCH v2 3/4] blk-iocost: account zone append completions in latency stats

[Tao Cui]

From: Tao Cui <cuitao@xxxxxxxxxx>

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.

This is not covered by the patch that prices zone appends: charging
goes through the cost model, while the latency window is the feedback
path the vrate controller watches.

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

Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
Signed-off-by: Tao Cui <cuitao@xxxxxxxxxx>
---
 block/blk-iocost.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 2e4e9ce2c9359..ef1b7e65455e2 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