On Wed, Aug 15, 2018 at 3:25 PM, Jianchao Wang
<jianchao.w.wang@xxxxxxxxxx> wrote:
> Kyber depends on the mapping between cpu and nr_hw_queues. When
> update nr_hw_queues, elevator_type->ops.mq.init_hctx will be
> invoked before the mapping is adapted correctly, this would cause
> terrible result. A simply way to fix this is switch the io scheduler
> to none before update the nr_hw_queues, and then get it back after
> update nr_hw_queues. To achieve this, we add a new member elv_type
> in request_queue to save the original elevator and adapt and export
> elevator_switch_mq.
>
> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
> ---
> block/blk-mq.c | 37 +++++++++++++++++++++++++++++--------
> block/blk.h | 2 ++
> block/elevator.c | 20 ++++++++++++--------
> include/linux/blkdev.h | 3 +++
> 4 files changed, 46 insertions(+), 16 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 5efd789..89904cc 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -112,6 +112,7 @@ void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
> struct mq_inflight mi = { .part = part, .inflight = inflight, };
>
> inflight[0] = inflight[1] = 0;
> +
Not necessary to do that.
> blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
> }
>
> @@ -2147,8 +2148,6 @@ static void blk_mq_exit_hctx(struct request_queue *q,
> if (set->ops->exit_request)
> set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
>
> - blk_mq_sched_exit_hctx(q, hctx, hctx_idx);
> -
> if (set->ops->exit_hctx)
> set->ops->exit_hctx(hctx, hctx_idx);
>
> @@ -2216,12 +2215,9 @@ static int blk_mq_init_hctx(struct request_queue *q,
> set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
> goto free_bitmap;
>
> - if (blk_mq_sched_init_hctx(q, hctx, hctx_idx))
> - goto exit_hctx;
> -
> hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);
> if (!hctx->fq)
> - goto sched_exit_hctx;
> + goto exit_hctx;
>
> if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx, node))
> goto free_fq;
> @@ -2235,8 +2231,6 @@ static int blk_mq_init_hctx(struct request_queue *q,
>
> free_fq:
> kfree(hctx->fq);
> - sched_exit_hctx:
> - blk_mq_sched_exit_hctx(q, hctx, hctx_idx);
Seems both blk_mq_sched_init_hctx() and blk_mq_sched_exit_hctx() may be
removed now.
> exit_hctx:
> if (set->ops->exit_hctx)
> set->ops->exit_hctx(hctx, hctx_idx);
> @@ -2913,6 +2907,25 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
> list_for_each_entry(q, &set->tag_list, tag_set_list)
> blk_mq_freeze_queue(q);
>
> + /*
> + * switch io scheduler to NULL to clean up the data in it.
> + * will get it back after update mapping between cpu and hw queues.
> + */
> + list_for_each_entry(q, &set->tag_list, tag_set_list) {
> + if (!q->elevator) {
> + q->elv_type = NULL;
> + continue;
> + }
> + q->elv_type = q->elevator->type;
> + mutex_lock(&q->sysfs_lock);
> + /*
> + * elevator_release will put it.
> + */
> + __module_get(q->elv_type->elevator_owner);
> + elevator_switch_mq(q, NULL);
> + mutex_unlock(&q->sysfs_lock);
> + }
> +
> set->nr_hw_queues = nr_hw_queues;
> blk_mq_update_queue_map(set);
> list_for_each_entry(q, &set->tag_list, tag_set_list) {
> @@ -2920,6 +2933,14 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
> blk_mq_queue_reinit(q);
> }
>
> + list_for_each_entry(q, &set->tag_list, tag_set_list) {
> + if (!q->elv_type)
> + continue;
> +
> + mutex_lock(&q->sysfs_lock);
> + elevator_switch_mq(q, q->elv_type);
> + mutex_unlock(&q->sysfs_lock);
> + }
BFQ defines .init_hctx() too, so seems this generic approach is correct way for
this issue.
thanks,
Ming Lei
