Re: [PATCH v4] staging: rts5208: Convert kmap() to kmap_local_page()

Ira Weiny
2022-03-30T21:11:20Z

On Wed, Mar 30, 2022 at 04:33:31PM +0200, Fabio M. De Francesco wrote:
> The use of kmap() is being deprecated in favor of kmap_local_page()
> where it is feasible.
>
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible. Therefore rtsx_stor_access_xfer_buf() is a function
> where the use of kmap_local_page() in place of kmap() is correctly
> suited.
>
> Convert to kmap_local_page() but, instead of open coding it, use the
> helpers memcpy_to_page() and memcpy_from_page().
>
> Make a minor change to a comment related to scatter-gather.
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

Thanks!

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> ---
>
> v1 -> v2: Rework the commit message and use the appropriate helpers
> instead of open coding the use of kmap_local_page()/kunmap_local_page().
> (Thanks to Ira Weiny <ira.weiny@intel.com>).
>
> v2 -> v3: Use memcpy_{to,from}_page() arguments correctly.
> (Thanks to Dan Carpenter <dan.carpenter@oracle.com>).
>
> v3 -> v4: According to a suggestion by Ira Weiny, change the test
> of a comment related to the use of scatter-gather.
>
> drivers/staging/rts5208/rtsx_transport.c | 12 +++++-------
> 1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/staging/rts5208/rtsx_transport.c b/drivers/staging/rts5208/rtsx_transport.c
> index 805dc18fac0a..d5ad49de4c56 100644
> --- a/drivers/staging/rts5208/rtsx_transport.c
> +++ b/drivers/staging/rts5208/rtsx_transport.c
> @@ -55,9 +55,9 @@ unsigned int rtsx_stor_access_xfer_buf(unsigned char *buffer,
> *offset += cnt;
>
> /*
> - * Using scatter-gather. We have to go through the list one entry
> - * at a time. Each s-g entry contains some number of pages, and
> - * each page has to be kmap()'ed separately.
> + * Using scatter-gather. We have to go through the list one entry
> + * at a time. Each s-g entry contains some number of pages which
> + * have to be copied one at a time.
> */
> } else {
> struct scatterlist *sg =
> @@ -92,13 +92,11 @@ unsigned int rtsx_stor_access_xfer_buf(unsigned char *buffer,
> while (sglen > 0) {
> unsigned int plen = min(sglen, (unsigned int)
> PAGE_SIZE - poff);
> - unsigned char *ptr = kmap(page);
>
> if (dir == TO_XFER_BUF)
> - memcpy(ptr + poff, buffer + cnt, plen);
> + memcpy_to_page(page, poff, buffer + cnt, plen);
> else
> - memcpy(buffer + cnt, ptr + poff, plen);
> - kunmap(page);
> + memcpy_from_page(buffer + cnt, page, poff, plen);
>
> /* Start at the beginning of the next page */
> poff = 0;
> --
> 2.34.1
>