Re: [PATCH] nvme: determine the number of IO queues

Edmund Nadolski (Microsoft)
2019-04-17T21:30:22Z

On 4/17/19 7:12 AM, Aaron Ma wrote:
> Some controllers support limited IO queues, when over set
> the number, it will return invalid field error.
> Then NVME will be removed by driver.
>
> Find the max number of IO queues that controller supports.
> When it still got invalid result, set 1 IO queue at least to
> bring NVME online.
>
> Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
> ---
> drivers/nvme/host/core.c | 29 ++++++++++++++++++-----------
> 1 file changed, 18 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 2c43e12b70af..fb7f05c310c8 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -1134,14 +1134,24 @@ static int nvme_set_features(struct nvme_ctrl *dev, unsigned fid, unsigned dword
>
> int nvme_set_queue_count(struct nvme_ctrl *ctrl, int *count)
> {
> - u32 q_count = (*count - 1) | ((*count - 1) << 16);
> + u32 q_count;
> u32 result;
> - int status, nr_io_queues;
> -
> - status = nvme_set_features(ctrl, NVME_FEAT_NUM_QUEUES, q_count, NULL, 0,
> - &result);
> - if (status < 0)
> - return status;
> + int status = -1;
> + int nr_io_queues;
> + int try_count;
> +
> + for (try_count = *count; try_count > 0; try_count--) {
> + q_count = (try_count - 1) | ((try_count - 1) << 16);

A macro here might help readability.

> + status = nvme_set_features(ctrl, NVME_FEAT_NUM_QUEUES,
> + q_count, NULL, 0, &result);
> + if (status < 0)
> + return status;
> + else if (status == 0) {

else following return is not needed.

> + nr_io_queues = min(result & 0xffff, result >> 16) + 1;

Likewise, a macro as above.

Ed

> + *count = min(try_count, nr_io_queues);
> + break;
> + }
> + }
>
> /*
> * Degraded controllers might return an error when setting the queue
> @@ -1150,10 +1160,7 @@ int nvme_set_queue_count(struct nvme_ctrl *ctrl, int *count)
> */
> if (status > 0) {
> dev_err(ctrl->device, "Could not set queue count (%d)\n", status);
> - *count = 0;
> - } else {
> - nr_io_queues = min(result & 0xffff, result >> 16) + 1;
> - *count = min(*count, nr_io_queues);
> + *count = 1;
> }
>
> return 0;
>