On Thu, Mar 06, 2025 at 11:03:22AM +0800, Herbert Xu wrote:
> +void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src,
> + unsigned int nbytes)
> +{
> + struct scatter_walk swalk;
> + struct scatter_walk dwalk;
> +
> + if (unlikely(nbytes == 0)) /* in case sg == NULL */
> + return;
> +
> + scatterwalk_start(&swalk, src);
> + scatterwalk_start(&dwalk, dst);
> +
> + do {
> + unsigned int slen, dlen;
> + unsigned int len;
> +
> + slen = scatterwalk_next(&swalk, nbytes);
> + dlen = scatterwalk_next(&dwalk, nbytes);
> + len = min(slen, dlen);
> + memcpy(dwalk.addr, swalk.addr, len);
> + scatterwalk_done_src(&swalk, len);
> + scatterwalk_done_dst(&dwalk, len);
> + nbytes -= len;
> + } while (nbytes);
> +}
> +EXPORT_SYMBOL_GPL(memcpy_sglist);
Local kmaps must be released in reverse order of the mapping, so
scatterwalk_done_dst() must be done before scatterwalk_done_src() above.
- Eric
