Re: [PATCH v3 1/1] virtio-blk: add num_request_queues module parameter

[Pankaj Gupta <pankaj.gupta.linux@gmail.com>]

> Sometimes a user would like to control the amount of request queues to
> be created for a block device. For example, for limiting the memory
> footprint of virtio-blk devices.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> ---
>
> changes from v2:
>  - renamed num_io_queues to num_request_queues (from Stefan)
>  - added Reviewed-by signatures (from Stefan and Christoph)
>
> changes from v1:
>  - use param_set_uint_minmax (from Christoph)
>  - added "Should > 0" to module description
>
> Note: This commit apply on top of Jens's branch for-5.15/drivers
>
> ---
>  drivers/block/virtio_blk.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 4b49df2dfd23..aaa2833a4734 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -24,6 +24,23 @@
>  /* The maximum number of sg elements that fit into a virtqueue */
>  #define VIRTIO_BLK_MAX_SG_ELEMS 32768
>
> +static int virtblk_queue_count_set(const char *val,
> +               const struct kernel_param *kp)
> +{
> +       return param_set_uint_minmax(val, kp, 1, nr_cpu_ids);
> +}
> +
> +static const struct kernel_param_ops queue_count_ops = {
> +       .set = virtblk_queue_count_set,
> +       .get = param_get_uint,
> +};
> +
> +static unsigned int num_request_queues;
> +module_param_cb(num_request_queues, &queue_count_ops, &num_request_queues,
> +               0644);
> +MODULE_PARM_DESC(num_request_queues,
> +                "Number of request queues to use for blk device. Should > 0");
> +
>  static int major;
>  static DEFINE_IDA(vd_index_ida);
>
> @@ -501,7 +518,9 @@ static int init_vq(struct virtio_blk *vblk)
>         if (err)
>                 num_vqs = 1;
>
> -       num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
> +       num_vqs = min_t(unsigned int,
> +                       min_not_zero(num_request_queues, nr_cpu_ids),
> +                       num_vqs);
>
>         vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL);
>         if (!vblk->vqs)
> --

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>