netdev - Re: [RESEND PATCH] ixgbe: Don't call kmap() on page allocated with GFP

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Date:   Thu, 15 Sep 2022 09:57:52 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>
CC:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "Jesper Dangaard Brouer" <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        "Jean Delvare" <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
        <linux-hwmon@...r.kernel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Gurucharan <gurucharanx.g@...el.com>
Subject: Re: [RESEND PATCH] ixgbe: Don't call kmap() on page allocated with
 GFP_ATOMIC

On Thu, Sep 15, 2022 at 02:40:12PM +0200, Fabio M. De Francesco wrote:
> Pages allocated with GFP_ATOMIC cannot come from Highmem. This is why
> there is no need to call kmap() on them.
> 
> Therefore, don't call kmap() on rx_buffer->page() and instead use a
> plain page_address() to get the kernel address.
> 
> Suggested-by: Ira Weiny <ira.weiny@...el.com>
> Suggested-by: Alexander Duyck <alexander.duyck@...il.com>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Reviewed-by: Alexander Duyck <alexander.duyck@...il.com>
> Tested-by: Gurucharan <gurucharanx.g@...el.com>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
> 
> I send again this patch because it was submitted more than two months ago,
> Monday 4th July 2022, but for one or more (good?) reasons it has not yet
> reached Linus' tree. In the meantime I am also forwarding two "Reviewed-by"
> and one "Tested-by" tags (thanks a lot to Ira, Alexander, Gurucharan).
> Obviously I have not made any changes to the code.

I see this applied by Tony Nguyen in linux-next:

03f51719df03 ixgbe: Don't call kmap() on page allocated with GFP_ATOMIC

So I assume it will land in the next merge window?

Move Tony to the To line.

Ira

> 
>  drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> index 04f453eabef6..cb5c707538a5 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> @@ -1964,15 +1964,13 @@ static bool ixgbe_check_lbtest_frame(struct ixgbe_rx_buffer *rx_buffer,
>  
>  	frame_size >>= 1;
>  
> -	data = kmap(rx_buffer->page) + rx_buffer->page_offset;
> +	data = page_address(rx_buffer->page) + rx_buffer->page_offset;
>  
>  	if (data[3] != 0xFF ||
>  	    data[frame_size + 10] != 0xBE ||
>  	    data[frame_size + 12] != 0xAF)
>  		match = false;
>  
> -	kunmap(rx_buffer->page);
> -
>  	return match;
>  }
>  
> -- 
> 2.37.2
>