linux-kernel - Re: [PATCH v3] intel: igb: igb_ethtool.c: Convert kmap() to kmap_local

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Message-ID: <alpine.DEB.2.22.394.2204161331080.3501@hadrien>
Date:   Sat, 16 Apr 2022 13:31:56 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>
cc:     outreachy@...ts.linux.dev, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ira.weiny@...el.com
Subject: Re: [PATCH v3] intel: igb: igb_ethtool.c: Convert kmap() to
 kmap_local_page()



On Sat, 16 Apr 2022, Alaa Mohamed wrote:

> Convert kmap() to kmap_local_page()
>
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible.

It's not clearer.  This is a general statement about the function.  You
need to explain why it is appropriate to use it here.  Unless it is the
case that all calls to kmap should be converted to call kmap_local_page.

julia

>
> Signed-off-by: Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>
> ---
> changes in V2:
> 	fix kunmap_local path value to take address of the mapped page.
> ---
> changes in V3:
> 	edit commit message to be clearer
> ---
>  drivers/net/ethernet/intel/igb/igb_ethtool.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_ethtool.c b/drivers/net/ethernet/intel/igb/igb_ethtool.c
> index 2a5782063f4c..c14fc871dd41 100644
> --- a/drivers/net/ethernet/intel/igb/igb_ethtool.c
> +++ b/drivers/net/ethernet/intel/igb/igb_ethtool.c
> @@ -1798,14 +1798,14 @@ static int igb_check_lbtest_frame(struct igb_rx_buffer *rx_buffer,
>
>  	frame_size >>= 1;
>
> -	data = kmap(rx_buffer->page);
> +	data = kmap_local_page(rx_buffer->page);
>
>  	if (data[3] != 0xFF ||
>  	    data[frame_size + 10] != 0xBE ||
>  	    data[frame_size + 12] != 0xAF)
>  		match = false;
>
> -	kunmap(rx_buffer->page);
> +	kunmap_local(data);
>
>  	return match;
>  }
> --
> 2.35.2
>
>
>