On 4/8/23 08:58, Bart Van Assche wrote:
> Send zoned writes inserted by the device mapper to the I/O scheduler.
> This prevents that zoned writes get reordered if a device mapper driver
> has been stacked on top of a driver for a zoned block device.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
> block/blk-mq.c | 16 +++++++++++++---
> block/blk.h | 19 +++++++++++++++++++
> 2 files changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index db93b1a71157..fefc9a728e0e 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -3008,9 +3008,19 @@ blk_status_t blk_insert_cloned_request(struct request *rq)
> blk_account_io_start(rq);
>
> /*
> - * Since we have a scheduler attached on the top device,
> - * bypass a potential scheduler on the bottom device for
> - * insert.
> + * Send zoned writes to the I/O scheduler if an I/O scheduler has been
> + * attached.
> + */
> + if (q->elevator && blk_rq_is_seq_zoned_write(rq)) {
> + blk_mq_sched_insert_request(rq, /*at_head=*/false,
> + /*run_queue=*/true,
> + /*async=*/false);
> + return BLK_STS_OK;
> + }
Looks OK to me, but as I understand it, this function is used only for request
based device mapper, none of which currently support zoned block devices if I a
not mistaken. So is this change really necessary ?
> +
> + /*
> + * If no I/O scheduler has been attached or if the request is not a
> + * zoned write bypass the I/O scheduler attached to the bottom device.
> */
> blk_mq_run_dispatch_ops(q,
> ret = blk_mq_request_issue_directly(rq, true));
> diff --git a/block/blk.h b/block/blk.h
> index d65d96994a94..4b6f8d7a6b84 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -118,6 +118,25 @@ static inline bool bvec_gap_to_prev(const struct queue_limits *lim,
> return __bvec_gap_to_prev(lim, bprv, offset);
> }
>
> +/**
> + * blk_rq_is_seq_zoned_write() - Whether @rq is a write request for a sequential zone.
> + * @rq: Request to examine.
> + *
> + * In this context sequential zone means either a sequential write required or
> + * to a sequential write preferred zone.
> + */
> +static inline bool blk_rq_is_seq_zoned_write(struct request *rq)
> +{
> + switch (req_op(rq)) {
> + case REQ_OP_WRITE:
> + case REQ_OP_WRITE_ZEROES:
> + return disk_zone_is_seq(rq->q->disk, blk_rq_pos(rq));
> + case REQ_OP_ZONE_APPEND:
> + default:
> + return false;
> + }
> +}
> +
> static inline bool rq_mergeable(struct request *rq)
> {
> if (blk_rq_is_passthrough(rq))
