Re: [PATCH] ixgbe: Don't call kmap() on page allocated with GFP_ATOMIC

[Ira Weiny]

On Mon, Jul 04, 2022 at 04:01:29PM +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.

I'm still not 100% sure where this page gets allocated but AFAICT it is
allocated in ixgbe_alloc_mapped_page() which calls dev_alloc_pages() for the
allocation which is where the GFP_ATOMIC is specified.

I think I would add this detail here.

That said, and assuming my analysis is correct, the code looks fine so:

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

> 
> 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@xxxxxxxxx>
> Suggested-by: Alexander Duyck <alexander.duyck@xxxxxxxxx>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> ---
>  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 628d0eb0599f..71196fd92f81 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> @@ -1966,15 +1966,13 @@ 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;
>  }
>  
> -- 
> 2.36.1
>