Re: [PATCH] mm/sparse: remove unnecessary NULL check before allocating mem_section

[Mike Rapoport <rppt@kernel.org>]

Hi,

On Sun, Apr 19, 2026 at 11:42:25PM +0900, Sang-Heon Jeon wrote:
> Commit 850ed20539a4 ("mm: move array mem_section init code out
> of memory_present()") moved mem_section allocation logic
> into memblocks_present().
> 
> Before that move, memory_present() could be called multiple times, so
> unlikely() matched the common case, where most calls found mem_section
> already allocated.
> 
> After that move, memblocks_present() is called exactly once from
> sparse_init(). Under CONFIG_SPARSEMEM_EXTREME, mem_section is always
> NULL when it is called.
> 
> So remove unnecessary NULL check before allocating mem_section. No
> functional change.
> 
> Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
> Hello, 
> 
> While looking into boot information, I found a minor enhancement point.
> If I misunderstood anything, please feel free to let me know.

I would say it's more a cleanup than enhancement :)
 
> Thank you for taking valuable time to review this work.
> 
> Best Regards,
> Sang-Heon Jeon
> ---
>  mm/sparse.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index effdac6b0ab1..e13f9f5fa090 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -201,13 +201,11 @@ static void __init memblocks_present(void)
>  	int i, nid;
>  
>  #ifdef CONFIG_SPARSEMEM_EXTREME
> -	if (unlikely(!mem_section)) {
> -		unsigned long size, align;
> +	unsigned long size, align;
>  
> -		size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> -		align = 1 << (INTERNODE_CACHE_SHIFT);
> -		mem_section = memblock_alloc_or_panic(size, align);
> -	}
> +	size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> +	align = 1 << (INTERNODE_CACHE_SHIFT);
> +	mem_section = memblock_alloc_or_panic(size, align);
>  #endif
>  
>  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
> -- 
> 2.43.0
> 

-- 
Sincerely yours,
Mike.