Re: [PATCH 2/4] blk-mq: introduce blk_mq_get_queue_depth()

Jens Axboe
2017-04-28T18:23:38Z

On 04/28/2017 09:15 AM, Ming Lei wrote:
> The hardware queue depth can be resized via blk_mq_update_nr_requests(),
> so introduce this helper for retrieving queue's depth easily.
>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> block/blk-mq.c | 12 ++++++++++++
> block/blk-mq.h | 1 +
> 2 files changed, 13 insertions(+)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e530bc54f0d9..04761fb76ab4 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2637,6 +2637,18 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
> }
> EXPORT_SYMBOL(blk_mq_free_tag_set);
>
> +/*
> + * Queue depth can be changed via blk_mq_update_nr_requests(),
> + * so use this helper to retrieve queue's depth.
> + */
> +int blk_mq_get_queue_depth(struct request_queue *q)
> +{
> + /* All queues have same queue depth */
> + struct blk_mq_tags *tags = q->tag_set->tags[0];
> +
> + return tags->bitmap_tags.sb.depth;
> +}

What about the per-hw queue tag space? q->nr_requests is device side,
this might not be.

--
Jens Axboe