Subject: Re: [PATCH v2 2/3] nvme: implement DMA_ATTR_NO_WARN

From: Masayoshi Mizuma <[email-masked]>
Date: Fri, 8 Jul 2016 16:54:50 +0900

On Thu, 7 Jul 2016 09:45:08 -0300 Mauricio Faria De Oliveira wrote:
> Use the DMA_ATTR_NO_WARN attribute on dma_map_sg() calls of nvme driver.
>
> Signed-off-by: Mauricio Faria de Oliveira <[email-masked]>
> Reviewed-by: Gabriel Krisman Bertazi <[email-masked]>
> ---
> Changelog:
>   v2:
>    - address warnings from checkpatch.pl (line wrapping and typos)
>
>   drivers/nvme/host/pci.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index d1a8259..a7ccad8 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -18,6 +18,7 @@
>   #include <linux/blk-mq.h>
>   #include <linux/cpu.h>
>   #include <linux/delay.h>
> +#include <linux/dma-attrs.h>
>   #include <linux/errno.h>
>   #include <linux/fs.h>
>   #include <linux/genhd.h>
> @@ -65,6 +66,8 @@ MODULE_PARM_DESC(use_cmb_sqes, "use controller's memory buffer for I/O SQes");
>
>   static struct workqueue_struct *nvme_workq;
>
> +static DEFINE_DMA_ATTRS(nvme_dma_attrs);
> +
>   struct nvme_dev;
>   struct nvme_queue;
>
> @@ -498,7 +501,8 @@ static int nvme_map_data(struct nvme_dev *dev, struct request *req,
>   		goto out;
>
>   	ret = BLK_MQ_RQ_QUEUE_BUSY;
> -	if (!dma_map_sg(dev->dev, iod->sg, iod->nents, dma_dir))
> +	if (!dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, dma_dir,
> +				&nvme_dma_attrs))

This change is OK because the return value of nvme_map_data() is
BLK_MQ_RQ_QUEUE_BUSY, so the IO will be requeued.

>   		goto out;
>
>   	if (!nvme_setup_prps(dev, req, size))
> @@ -516,7 +520,8 @@ static int nvme_map_data(struct nvme_dev *dev, struct request *req,
>   		if (rq_data_dir(req))
>   			nvme_dif_remap(req, nvme_dif_prep);
>
> -		if (!dma_map_sg(dev->dev, &iod->meta_sg, 1, dma_dir))
> +		if (!dma_map_sg_attrs(dev->dev, &iod->meta_sg, 1, dma_dir,
> +					&nvme_dma_attrs))

Here, I think the error messages should not be suppressed because
the return value of nvme_map_data() is BLK_MQ_RQ_QUEUE_ERROR, so
the IO returns as -EIO.

- Masayoshi Mizuma

>   			goto out_unmap;
>   	}
>
> @@ -2118,6 +2123,9 @@ static int __init nvme_init(void)
>   	result = pci_register_driver(&nvme_driver);
>   	if (result)
>   		destroy_workqueue(nvme_workq);
> +
> +	dma_set_attr(DMA_ATTR_NO_WARN, &nvme_dma_attrs);
> +
>   	return result;
>   }
>
>