On luned? 28 marzo 2022 17:41:53 CEST Ira Weiny wrote:
> On Mon, Mar 28, 2022 at 01:24:40PM +0200, Fabio M. De Francesco wrote:
> > The use of kmap() is being deprecated and kmap_local_page() is faster.
> > Use kmap_local_page() in place of kmap().
>
> Thanks for the patch!
Thanks for your review!
> I have just a couple of comments.
>
> kmap_local_page() is not necessarily faster than kmap() but it is more correct
> in this case. You should mention why.
Sure, my mistake. Thomas G. was talking about kmap_atomic() when he wrote that
it is "faster". It does not apply to kmap_local_page().
What could justify the use of kmap_local_page() is that "The mapping is per
thread, CPU local and not globally visible.". Therefore this code is the right
context where to use kmap_local_page() in place of kmap().
At this moment I think that I might change my commit message and write something
like the above.
However, I'll research more information during the next days. In the meantime
I'm also going to take a look at the differences in implementation.
> Also to help with kmap_local_page() there are a number of helpers implemented
> in highmem.h for things like memcpy, memmove, etc.
>
> Check out memcpy_page() for this use case.
Aren't memcpy_to_page() and memcpy_from_page() better suited for the two
different branches of the "if" statement?
Thank you,
Fabio M. De Francesco
>
> Thank you!
> Ira
>
> >
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> > ---
> > drivers/staging/rts5208/rtsx_transport.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/rts5208/rtsx_transport.c b/drivers/staging/rts5208/rtsx_transport.c
> > index 805dc18fac0a..de690d7ee5e3 100644
> > --- a/drivers/staging/rts5208/rtsx_transport.c
> > +++ b/drivers/staging/rts5208/rtsx_transport.c
> > @@ -92,13 +92,13 @@ 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);
> > + unsigned char *ptr = kmap_local_page(page);
> >
> > if (dir == TO_XFER_BUF)
> > memcpy(ptr + poff, buffer + cnt, plen);
> > else
> > memcpy(buffer + cnt, ptr + poff, plen);
> > - kunmap(page);
> > + kunmap_local(ptr);
> >
> > /* Start at the beginning of the next page */
> > poff = 0;
> > --
> > 2.34.1
> >
>
