netdev - Re: [PATCH] enic: fix build warning without CONFIG_CPUMASK

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Date:   Thu, 7 Mar 2019 08:14:37 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Christian Benvenuti <benve@...co.com>,
        Govindarajulu Varadarajan <_govind@....com>,
        Parvi Kaustubhi <pkaustub@...co.com>,
        "David S. Miller" <davem@...emloft.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] enic: fix build warning without CONFIG_CPUMASK_OFFSTACK

On Thu, Mar 07, 2019 at 10:33:02AM +0100, Arnd Bergmann wrote:
> The enic driver relies on the CONFIG_CPUMASK_OFFSTACK feature to
> dynamically allocate a struct member, but this is normally intended for
> local variables.
> 
> Building with clang, I get a warning for a few locations that check the
> address of the cpumask_var_t:
> 
> drivers/net/ethernet/cisco/enic/enic_main.c:122:22: error: address of array 'enic->msix[i].affinity_mask' will always evaluate to 'true' [-Werror,-Wpointer-bool-conversion]
> 
> As far as I can tell, the code is still correct, as the truth value of
> the pointer is what we need in this configuration.  To get rid of the
> warning, I split out the check into a separate function, and hide that
> portion if CONFIG_CPUMASK_OFFSTACK is disabled.
> 
> Fixes: 322cf7e3a4e8 ("enic: assign affinity hint to interrupts")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/ethernet/cisco/enic/enic_main.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c b/drivers/net/ethernet/cisco/enic/enic_main.c
> index 9a7f70db20c7..f652a8bd163e 100644
> --- a/drivers/net/ethernet/cisco/enic/enic_main.c
> +++ b/drivers/net/ethernet/cisco/enic/enic_main.c
> @@ -112,6 +112,15 @@ static struct enic_intr_mod_range mod_range[ENIC_MAX_LINK_SPEEDS] = {
>  	{3,  6}, /* 10 - 40 Gbps */
>  };
>  
> +static inline int enic_affinity_mask_empty(struct enic *enic, int i)
> +{
> +#ifdef CONFIG_CPUMASK_OFFSTACK
> +	if (!enic->msix[i].affinity_mask)
> +		return 1;
> +#endif
> +	return cpumask_empty(enic->msix[i].affinity_mask);
> +}
> +
>  static void enic_init_affinity_hint(struct enic *enic)
>  {
>  	int numa_node = dev_to_node(&enic->pdev->dev);
> @@ -119,8 +128,7 @@ static void enic_init_affinity_hint(struct enic *enic)
>  
>  	for (i = 0; i < enic->intr_count; i++) {
>  		if (enic_is_err_intr(enic, i) || enic_is_notify_intr(enic, i) ||
> -		    (enic->msix[i].affinity_mask &&
> -		     !cpumask_empty(enic->msix[i].affinity_mask)))
> +		    !enic_affinity_mask_empty(enic, i))
>  			continue;
>  		if (zalloc_cpumask_var(&enic->msix[i].affinity_mask,
>  				       GFP_KERNEL))
> @@ -148,8 +156,7 @@ static void enic_set_affinity_hint(struct enic *enic)
>  	for (i = 0; i < enic->intr_count; i++) {
>  		if (enic_is_err_intr(enic, i)		||
>  		    enic_is_notify_intr(enic, i)	||
> -		    !enic->msix[i].affinity_mask	||
> -		    cpumask_empty(enic->msix[i].affinity_mask))
> +		    enic_affinity_mask_empty(enic, i))
>  			continue;
>  		err = irq_set_affinity_hint(enic->msix_entry[i].vector,
>  					    enic->msix[i].affinity_mask);
> @@ -161,8 +168,7 @@ static void enic_set_affinity_hint(struct enic *enic)
>  	for (i = 0; i < enic->wq_count; i++) {
>  		int wq_intr = enic_msix_wq_intr(enic, i);
>  
> -		if (enic->msix[wq_intr].affinity_mask &&
> -		    !cpumask_empty(enic->msix[wq_intr].affinity_mask))
> +		if (!enic_affinity_mask_empty(enic, wq_intr))
>  			netif_set_xps_queue(enic->netdev,
>  					    enic->msix[wq_intr].affinity_mask,
>  					    i);
> -- 
> 2.20.0
> 

A slightly less intrusive change would be using cpumask_available, which
was specifically introduced for this purpose in commit f7e30f01a9e2
("cpumask: Add helper cpumask_available()").