[PATCH 02/12] dma-buf: add dma_buf_(un)map_attachment_locked variants v3

[Hillf Danton]

On Tue, 16 Apr 2019 20:38:31 +0200 Christian König wrote:
> Add function variants which can be called with the reservation lock
> already held.
> 
> v2: reordered, add lockdep asserts, fix kerneldoc
> v3: rebased on sgt caching
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/dma-buf/dma-buf.c | 63 +++++++++++++++++++++++++++++++++++++++
>  include/linux/dma-buf.h   |  5 ++++
>  2 files changed, 68 insertions(+)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 65161a82d4d5..ef480e5fb239 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -623,6 +623,43 @@ 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

Something is missing; seems to be s/of the/of the dma_buf_ops./
> + *
> + * Returns the scatterlist table of the attachment;
> + * dma_buf_ops.

Oh it is sitting here!

> + * @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.
> + *
EINTR looks impossible in the code.

> + * 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;
> +
> +	might_sleep();
> +	reservation_object_assert_held(attach->dmabuf->resv);
> +
> +	if (attach->sgt)
> +		return attach->sgt;
> +
> +	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);
> +
Best Regards
Hillf