linux-kernel - Re: [PATCH] staging: vc04_services: Convert kmap() to kmap_local

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Date:   Fri, 1 Apr 2022 11:09:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     Nicolas Saenz Julienne <nsaenz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        ira.weiny@...el.com, outreachy@...ts.linux.dev
Subject: Re: [PATCH] staging: vc04_services: Convert kmap() to
 kmap_local_page()

On Fri, Apr 01, 2022 at 10:07:36AM +0200, Fabio M. De Francesco wrote:
> On mercoledì 30 marzo 2022 21:14:14 CEST Fabio M. De Francesco wrote:
> > The use of kmap() is being deprecated in favor of kmap_local_page()
> > where it is feasible. In file interface/vchiq_arm/vchiq_arm.c,
> > function free_pagelist() calls kmap() / kunmap() from two places.
> > 
> > With kmap_local_page(), the mapping is per thread, CPU local and not
> > globally visible. Therefore, free_pagelist() 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
> > memcpy_to_page() helper.
> > 
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> > ---
> >  .../vc04_services/interface/vchiq_arm/vchiq_arm.c   | 13 +++++--------
> >  1 file changed, 5 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> > index f0bfacfdea80..efb1383b5218 100644
> > --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> > +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> > @@ -431,21 +431,18 @@ free_pagelist(struct vchiq_pagelist_info *pagelistinfo,
> >  			if (head_bytes > actual)
> >  				head_bytes = actual;
> >  
> > -			memcpy((char *)kmap(pages[0]) +
> > +			memcpy_to_page(pages[0],
> >  				pagelist->offset,
> >  				fragments,
> >  				head_bytes);
> > -			kunmap(pages[0]);
> >  		}
> >  		if ((actual >= 0) && (head_bytes < actual) &&
> > -		    (tail_bytes != 0)) {
> > -			memcpy((char *)kmap(pages[num_pages - 1]) +
> > -				((pagelist->offset + actual) &
> > -				(PAGE_SIZE - 1) & ~(g_cache_line_size - 1)),
> > +		    (tail_bytes != 0))
> > +			memcpy_to_page(pages[num_pages - 1],
> > +				(pagelist->offset + actual) &
> > +				(PAGE_SIZE - 1) & ~(g_cache_line_size - 1),
> >  				fragments + g_cache_line_size,
> >  				tail_bytes);
> > -			kunmap(pages[num_pages - 1]);
> > -		}
> >  
> >  		down(&g_free_fragments_mutex);
> >  		*(char **)fragments = g_free_fragments;
> > -- 
> > 2.34.1
> > 
> Hi Greg,
> 
> I've just received a message from you that says that a patch that I sent
> on March 31 has been applied to staging testing. I know that you usually
> apply patches in first come first served fashion (FIFO), therefore I wonder
> why this patch has not yet been applied.
> 
> Please don't misunderstand me: I have no hurry. I'm asking only because 
> I suspect that this patch, sent on March 30th) could have been overlooked 
> since it has the very identical subject of another patch that I sent on 
> the same day (or the day before, I'm not sure about it now) and which has 
> already been applied. Therefore, they may appear to be the same patch,
> because the only difference is that the drivers are different.

I wanted to give others the chance to review this before applying it :)