linux-kernel - Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac

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Message-ID: <c786a345-9ec4-4e41-8e69-506239db291c@stanley.mountain>
Date: Fri, 23 Aug 2024 12:10:40 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] idpf: Slightly simplify memory management in
 idpf_add_del_mac_filters()

On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:
> In idpf_add_del_mac_filters(), filters are chunked up into multiple
> messages to avoid sending a control queue message buffer that is too large.
> 
> Each chunk has up to IDPF_NUM_FILTERS_PER_MSG entries. So except for the
> last iteration which can be smaller, space for exactly
> IDPF_NUM_FILTERS_PER_MSG entries is allocated.
> 
> There is no need to free and reallocate a smaller array just for the last
> iteration.
> 
> This slightly simplifies the code and avoid an (unlikely) memory allocation
> failure.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>  drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> index 70986e12da28..b6f4b58e1094 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> @@ -3669,12 +3669,15 @@ int idpf_add_del_mac_filters(struct idpf_vport *vport,
>  		entries_size = sizeof(struct virtchnl2_mac_addr) * num_entries;
>  		buf_size = struct_size(ma_list, mac_addr_list, num_entries);
>  
> -		if (!ma_list || num_entries != IDPF_NUM_FILTERS_PER_MSG) {
> -			kfree(ma_list);
> +		if (!ma_list) {
>  			ma_list = kzalloc(buf_size, GFP_ATOMIC);
>  			if (!ma_list)
>  				return -ENOMEM;
>  		} else {
> +			/* ma_list was allocated in the first iteration
> +			 * so IDPF_NUM_FILTERS_PER_MSG entries are
> +			 * available
> +			 */
>  			memset(ma_list, 0, buf_size);
>  		}

It would be even nicer to move the ma_list allocation outside the loop:

        buf_size = struct_size(ma_list, mac_addr_list, IDPF_NUM_FILTERS_PER_MSG);
        ma_list = kmalloc(buf_size, GFP_ATOMIC);

regards,
dan carpenter