Re: [PATCH 1/4] dma-buf: add dma_buf_(un)map_attachment_locked variants v2

["Zhang, Jerry (Junwei)" <Jerry.Zhang@amd.com>]

On 06/22/2018 10:11 PM, Christian König wrote:
> Add function variants which can be called with the reservation lock
> already held.
>
> v2: reordered, add lockdep asserts, fix kerneldoc
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>   drivers/dma-buf/dma-buf.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/dma-buf.h   |  5 +++++
>   2 files changed, 62 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 852a3928ee71..dc94e76e2e2a 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -606,6 +606,40 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
>   }
>   EXPORT_SYMBOL_GPL(dma_buf_detach);
>
> +/**
> + * dma_buf_map_attachment_locked - Maps the buffer into _device_ address space
> + * with the reservation lock held. Is a wrapper for map_dma_buf() of the
> + *
> + * Returns the scatterlist table of the attachment;
> + * dma_buf_ops.
> + * @attach:	[in]	attachment whose scatterlist is to be returned
> + * @direction:	[in]	direction of DMA transfer
> + *
> + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> + * on error. May return -EINTR if it is interrupted by a signal.
> + *
> + * A mapping must be unmapped by using dma_buf_unmap_attachment_locked(). Note
> + * that the underlying backing storage is pinned for as long as a mapping
> + * exists, therefore users/importers should not hold onto a mapping for undue
> + * amounts of time.
> + */
> +struct sg_table *
> +dma_buf_map_attachment_locked(struct dma_buf_attachment *attach,
> +			      enum dma_data_direction direction)
> +{
> +	struct sg_table *sg_table;
> +

Perhaps better to add some error check, like dma_buf_map_attachment()

WARN_ON(!attach || !attach->dmabuf)

Apart from that, it's
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>

Jerry

> +	might_sleep();
> +	reservation_object_assert_held(attach->dmabuf->resv);
> +
> +	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> +	if (!sg_table)
> +		sg_table = ERR_PTR(-ENOMEM);
> +
> +	return sg_table;
> +}
> +EXPORT_SYMBOL_GPL(dma_buf_map_attachment_locked);
> +
>   /**
>    * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
>    * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
> @@ -639,6 +673,29 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>   }
>   EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
>
> +/**
> + * dma_buf_unmap_attachment_locked - unmaps the buffer with reservation lock
> + * held, should deallocate the associated scatterlist. Is a wrapper for
> + * unmap_dma_buf() of dma_buf_ops.
> + * @attach:	[in]	attachment to unmap buffer from
> + * @sg_table:	[in]	scatterlist info of the buffer to unmap
> + * @direction:  [in]    direction of DMA transfer
> + *
> + * This unmaps a DMA mapping for @attached obtained by
> + * dma_buf_map_attachment_locked().
> + */
> +void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *attach,
> +				     struct sg_table *sg_table,
> +				     enum dma_data_direction direction)
> +{
> +	might_sleep();
> +	reservation_object_assert_held(attach->dmabuf->resv);
> +
> +	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
> +						direction);
> +}
> +EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment_locked);
> +
>   /**
>    * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
>    * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 991787a03199..a25e754ae2f7 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -384,8 +384,13 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags);
>   struct dma_buf *dma_buf_get(int fd);
>   void dma_buf_put(struct dma_buf *dmabuf);
>
> +struct sg_table *dma_buf_map_attachment_locked(struct dma_buf_attachment *,
> +					       enum dma_data_direction);
>   struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
>   					enum dma_data_direction);
> +void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *,
> +				     struct sg_table *,
> +				     enum dma_data_direction);
>   void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
>   				enum dma_data_direction);
>   int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
>
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