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SubjectRe: [PATCH] virtio_blk: allow 0 as num_request_queues
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On 10/24/2021 4:54 PM, Michael S. Tsirkin wrote:
> The default value is 0 meaning "no limit". However if 0
> is specified on the command line it is instead silently
> converted to 1. Further, the value is already validated
> at point of use, there's no point in duplicating code
> validating the value when it is set.
>
> Simplify the code while making the behaviour more consistent
> by using plain module_param.
>
> Fixes: 1a662cf6cb9a ("virtio-blk: add num_request_queues module parameter")
> Cc: Max Gurtovoy <mgurtovoy@nvidia.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> drivers/block/virtio_blk.c | 14 +-------------
> 1 file changed, 1 insertion(+), 13 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 6318134aab76..c336d9bb9105 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -30,20 +30,8 @@
> #define VIRTIO_BLK_INLINE_SG_CNT 2
> #endif
>
> -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_param(num_request_queues, uint, 0644);

Not the best solution.

You can set the param to 1024 but in practice nr_cpu_ids can be 32 for
example.


> MODULE_PARM_DESC(num_request_queues,
> "Limit the number of request queues to use for blk device. "
> "0 for no limit. "

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