linux-kernel - Re: [PATCH v3 2/6] memory: move conditionally defined enums use inside ifdef tags

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Message-ID: <20250121043355.177611-1-bharata@amd.com>
Date: Tue, 21 Jan 2025 10:03:55 +0530
From: Bharata B Rao <bharata@....com>
To: <gourry@...rry.net>
CC: <abhishekd@...a.com>, <akpm@...ux-foundation.org>, <david@...hat.com>,
	<donettom@...ux.ibm.com>, <feng.tang@...el.com>, <hannes@...xchg.org>,
	<kbusch@...a.com>, <kernel-team@...a.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, <nehagholkar@...a.com>,
	<nphamcs@...il.com>, <ying.huang@...ux.alibaba.com>
Subject: Re: [PATCH v3 2/6] memory: move conditionally defined enums use inside ifdef tags

> NUMA_HINT_FAULTS and NUMA_HINT_FAULTS_LOCAL are only defined if
> CONFIG_NUMA_BALANCING is defined, but are used outside the tags in
> numa_migrate_check().  Fix this.
> 
> TNF_SHARED is only used if CONFIG_NUMA_BALANCING is enabled, so
> moving this line inside the ifdef is also safe - despite use of TNF_*
> elsewhere in the function.  TNF_* are not conditionally defined.
> 
> Signed-off-by: Gregory Price <gourry@...rry.net>
> ---
>  mm/memory.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 9cc93c2f79f3..8d254e97840d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5571,14 +5571,14 @@ int numa_migrate_check(struct folio *folio, struct vm_fault *vmf,
>  	/* Record the current PID acceesing VMA */
>  	vma_set_access_pid_bit(vma);
>  
> -	count_vm_numa_event(NUMA_HINT_FAULTS);
>  #ifdef CONFIG_NUMA_BALANCING
> +	count_vm_numa_event(NUMA_HINT_FAULTS);
>  	count_memcg_folio_events(folio, NUMA_HINT_FAULTS, 1);
> -#endif
>  	if (folio_nid(folio) == numa_node_id()) {
>  		count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
>  		*flags |= TNF_FAULT_LOCAL;
>  	}
> +#endif

I don't think moving count_vm_numa_event() to within
CONFIG_NUMA_BALANCING is necessary as it is defined separately as NOP
for !CONFIG_NUMA_BALANCING.

In fact numa_migrate_check() should be within CONFIG_NUMA_BALANCING as
it should ideally be  called only if NUMA balancing is enabled. The same
could be said for the callers of numa_migrate_check() which are
do_numa_page() and do_huge_pmd_numa_page().

Regards,
Bharata.