One of the optimizations in the block layer is that blk_mq_run_hw_queues()
only calls blk_mq_run_hw_queue() for a single hardware queue for single
queue I/O schedulers instead of for all hardware queues. Disable this
optimization if ELEVATOR_FLAG_SUPPORTS_ZONED_WRITE_PIPELINING has been
set. This patch prepares for adding write pipelining support in the
mq-deadline I/O scheduler.
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/blk-mq.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index e2d3239aacbc..33b639653b5d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2387,8 +2387,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
EXPORT_SYMBOL(blk_mq_run_hw_queue);
/*
- * Return prefered queue to dispatch from (if any) for non-mq aware IO
- * scheduler.
+ * Return preferred queue to dispatch from for single-queue IO schedulers.
*/
static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
{
@@ -2398,6 +2397,11 @@ static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
if (!blk_queue_sq_sched(q))
return NULL;
+ if (blk_queue_is_zoned(q) && blk_pipeline_zwr(q) &&
+ test_bit(ELEVATOR_FLAG_SUPPORTS_ZONED_WRITE_PIPELINING,
+ &q->elevator->flags))
+ return NULL;
+
ctx = blk_mq_get_ctx(q);
/*
* If the IO scheduler does not respect hardware queues when
