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

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Message-ID: <YkdlRw/p4WDKZqvg@iweiny-desk3>
Date:   Fri, 1 Apr 2022 13:49:11 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.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,
        outreachy@...ts.linux.dev
Subject: Re: [PATCH] staging: vc04_services: Convert kmap() to
 kmap_local_page()

On Wed, Mar 30, 2022 at 09:14:14PM +0200, 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>

LGTM:

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