linux-kernel - Re: [RFC 4/7] scsi_lib_dma: Add _attrs variant of scsi_dma

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Message-ID: <20240823100853.6cab2245@meshulam.tesarici.cz>
Date: Fri, 23 Aug 2024 10:08:53 +0200
From: Petr Tesařík <petr@...arici.cz>
To: mhkelley58@...il.com
Cc: mhklinux@...look.com, kbusch@...nel.org, axboe@...nel.dk,
 sagi@...mberg.me, James.Bottomley@...senPartnership.com,
 martin.petersen@...cle.com, kys@...rosoft.com, haiyangz@...rosoft.com,
 wei.liu@...nel.org, decui@...rosoft.com, robin.murphy@....com, hch@....de,
 m.szyprowski@...sung.com, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
 linux-scsi@...r.kernel.org, linux-hyperv@...r.kernel.org,
 linux-coco@...ts.linux.dev
Subject: Re: [RFC 4/7] scsi_lib_dma: Add _attrs variant of scsi_dma_map()

On Thu, 22 Aug 2024 11:37:15 -0700
mhkelley58@...il.com wrote:

> From: Michael Kelley <mhklinux@...look.com>
> 
> Extend the SCSI DMA mapping interfaces by adding the "_attrs" variant
> of scsi_dma_map(). This variant allows passing DMA_ATTR_* values, such
> as is needed to support swiotlb throttling. The existing scsi_dma_map()
> interface is unchanged, so no incompatibilities are introduced.
> 
> Signed-off-by: Michael Kelley <mhklinux@...look.com>

LGTM.

Reviewed-by: Petr Tesarik <ptesarik@...e.com>

Petr T

> ---
>  drivers/scsi/scsi_lib_dma.c | 13 +++++++------
>  include/scsi/scsi_cmnd.h    |  7 +++++--
>  2 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_lib_dma.c b/drivers/scsi/scsi_lib_dma.c
> index 5723915275ad..34453a79be97 100644
> --- a/drivers/scsi/scsi_lib_dma.c
> +++ b/drivers/scsi/scsi_lib_dma.c
> @@ -14,30 +14,31 @@
>  #include <scsi/scsi_host.h>
>  
>  /**
> - * scsi_dma_map - perform DMA mapping against command's sg lists
> + * scsi_dma_map_attrs - perform DMA mapping against command's sg lists
>   * @cmd:	scsi command
> + * @attrs:	DMA attribute flags
>   *
>   * Returns the number of sg lists actually used, zero if the sg lists
>   * is NULL, or -ENOMEM if the mapping failed.
>   */
> -int scsi_dma_map(struct scsi_cmnd *cmd)
> +int scsi_dma_map_attrs(struct scsi_cmnd *cmd, unsigned long attrs)
>  {
>  	int nseg = 0;
>  
>  	if (scsi_sg_count(cmd)) {
>  		struct device *dev = cmd->device->host->dma_dev;
>  
> -		nseg = dma_map_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
> -				  cmd->sc_data_direction);
> +		nseg = dma_map_sg_attrs(dev, scsi_sglist(cmd),
> +			scsi_sg_count(cmd), cmd->sc_data_direction, attrs);
>  		if (unlikely(!nseg))
>  			return -ENOMEM;
>  	}
>  	return nseg;
>  }
> -EXPORT_SYMBOL(scsi_dma_map);
> +EXPORT_SYMBOL(scsi_dma_map_attrs);
>  
>  /**
> - * scsi_dma_unmap - unmap command's sg lists mapped by scsi_dma_map
> + * scsi_dma_unmap - unmap command's sg lists mapped by scsi_dma_map_attrs
>   * @cmd:	scsi command
>   */
>  void scsi_dma_unmap(struct scsi_cmnd *cmd)
> diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
> index 45c40d200154..6603003bc588 100644
> --- a/include/scsi/scsi_cmnd.h
> +++ b/include/scsi/scsi_cmnd.h
> @@ -170,11 +170,14 @@ extern void scsi_kunmap_atomic_sg(void *virt);
>  blk_status_t scsi_alloc_sgtables(struct scsi_cmnd *cmd);
>  void scsi_free_sgtables(struct scsi_cmnd *cmd);
>  
> +#define scsi_dma_map(cmd) scsi_dma_map_attrs(cmd, 0)
> +
>  #ifdef CONFIG_SCSI_DMA
> -extern int scsi_dma_map(struct scsi_cmnd *cmd);
> +extern int scsi_dma_map_attrs(struct scsi_cmnd *cmd, unsigned long attrs);
>  extern void scsi_dma_unmap(struct scsi_cmnd *cmd);
>  #else /* !CONFIG_SCSI_DMA */
> -static inline int scsi_dma_map(struct scsi_cmnd *cmd) { return -ENOSYS; }
> +static inline int scsi_dma_map_attrs(struct scsi_cmnd *cmd, unsigned long attrs)
> +						{ return -ENOSYS; }
>  static inline void scsi_dma_unmap(struct scsi_cmnd *cmd) { }
>  #endif /* !CONFIG_SCSI_DMA */
>