diff options
authorBart Van Assche <bvanassche@acm.org>2021-08-24 10:05:20 -0700
committerJens Axboe <axboe@kernel.dk>2021-08-24 16:18:01 -0600
commitb6d2b054e8baaee53fd2d4854c63cbf0f2c6262a (patch)
parenta9ed27a764156929efe714033edb3e9023c5f321 (diff)
mq-deadline: Fix request accounting
The block layer may call the I/O scheduler .finish_request() callback without having called the .insert_requests() callback. Make sure that the mq-deadline I/O statistics are correct if the block layer inserts an I/O request that bypasses the I/O scheduler. This patch prevents that lower priority I/O is delayed longer than necessary for mixed I/O priority workloads. Cc: Niklas Cassel <Niklas.Cassel@wdc.com> Cc: Damien Le Moal <damien.lemoal@wdc.com> Cc: Hannes Reinecke <hare@suse.de> Reported-by: Niklas Cassel <Niklas.Cassel@wdc.com> Fixes: 08a9ad8bf607 ("block/mq-deadline: Add cgroup support") Signed-off-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20210824170520.1659173-1-bvanassche@acm.org Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com> Tested-by: Niklas Cassel <niklas.cassel@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 files changed, 11 insertions, 5 deletions
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index a09761cbdf12..18dc8efe9652 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -711,6 +711,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
prio = ioprio_class_to_prio[ioprio_class];
dd_count(dd, inserted, prio);
+ rq->elv.priv[0] = (void *)(uintptr_t)1;
if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
@@ -759,12 +760,10 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
- * Nothing to do here. This is defined only to ensure that .finish_request
- * method is called upon request completion.
- */
+/* Callback from inside blk_mq_rq_ctx_init(). */
static void dd_prepare_request(struct request *rq)
+ rq->elv.priv[0] = NULL;
@@ -791,7 +790,14 @@ static void dd_finish_request(struct request *rq)
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
struct dd_per_prio *per_prio = &dd->per_prio[prio];
- dd_count(dd, completed, prio);
+ /*
+ * The block layer core may call dd_finish_request() without having
+ * called dd_insert_requests(). Hence only update statistics for
+ * requests for which dd_insert_requests() has been called. See also
+ * blk_mq_request_bypass_insert().
+ */
+ if (rq->elv.priv[0])
+ dd_count(dd, completed, prio);
if (blk_queue_is_zoned(q)) {
unsigned long flags;

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