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

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Message-ID: <78253f3a-cdca-166a-ee54-e2173b2be5a7@gmail.com>
Date:   Sat, 16 Apr 2022 03:33:37 +0200
From:   Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>
To:     Ira Weiny <ira.weiny@...el.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
Subject: Re: [PATCH] intel: igb: igb_ethtool.c: Convert kmap() to
 kmap_local_page()


On ١٥‏/٤‏/٢٠٢٢ ٢٣:٤٠, Ira Weiny wrote:
> On Fri, Apr 15, 2022 at 10:53:07PM +0200, Alaa Mohamed wrote:
>> The use of kmap() is being deprecated in favor of kmap_local_page()
>> where it is feasible.
>>
>> With kmap_local_page(), the mapping is per thread, CPU local and not
>> globally visible.
>>
>> Signed-off-by: Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>
>> ---
>>   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..ba93aa4ae6a0 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(rx_buffer->page);
> kunmap_local() is different from kunmap().  It takes an address within the
> mapped page.  From the kdoc:
>
> /**
>   * kunmap_local - Unmap a page mapped via kmap_local_page().
>   * @__addr: An address within the page mapped
>   *
>   * @__addr can be any address within the mapped page.  Commonly it is the
>   * address return from kmap_local_page(), but it can also include offsets.
>   *
>   * Unmapping should be done in the reverse order of the mapping.  See
>   * kmap_local_page() for details.
>   */
> #define kunmap_local(__addr)                                    \
> ...
Got it , Thanks
>
>
> Ira
>
>>   
>>   	return match;
>>   }
>> -- 
>> 2.35.2
>>