[PATCH v7 2/8] block: Add copy offload support infrastructure

[Minwoo Im]

> +/*
> + * @bdev_in:	source block device
> + * @pos_in:	source offset
> + * @bdev_out:	destination block device
> + * @pos_out:	destination offset

@len is missing here.

> + * @end_io:	end_io function to be called on completion of copy operation,
> + *		for synchronous operation this should be NULL
> + * @private:	end_io function will be called with this private data, should be
> + *		NULL, if operation is synchronous in nature
> + * @gfp_mask:   memory allocation flags (for bio_alloc)
> + *
> + * Returns the length of bytes copied or a negative error value
> + *
> + * Description:
> + *	Copy source offset from source block device to destination block
> + *	device. length of a source range cannot be zero. Max total length of
> + *	copy is limited to MAX_COPY_TOTAL_LENGTH
> + */
> +int blkdev_issue_copy(struct block_device *bdev_in, loff_t pos_in,
> +		      struct block_device *bdev_out, loff_t pos_out, size_t len,
> +		      cio_iodone_t end_io, void *private, gfp_t gfp_mask)