Re: [PATCH 1/7] mm: move array mem_section init code out of memory_present()

[Mike Rapoport <rppt@kernel.org>]

On Tue, Mar 26, 2024 at 02:11:27PM +0800, Baoquan He wrote:
> When CONFIG_SPARSEMEM_EXTREME is enabled, mem_section need be initialized
> to point at a two-dimensional array, and its 1st dimension of length
> NR_SECTION_ROOTS will be dynamically allocated. Once the allocation is
> done, it's available for all nodes.
> 
> So take the 1st dimension of mem_section initialization out of
> memory_present()(), and put it into memblocks_present() which is a more
> appripriate place.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  mm/sparse.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index aed0951b87fa..46e88549d1a6 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -226,19 +226,6 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
>  {
>  	unsigned long pfn;
>  
> -#ifdef CONFIG_SPARSEMEM_EXTREME
> -	if (unlikely(!mem_section)) {
> -		unsigned long size, align;
> -
> -		size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> -		align = 1 << (INTERNODE_CACHE_SHIFT);
> -		mem_section = memblock_alloc(size, align);
> -		if (!mem_section)
> -			panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
> -			      __func__, size, align);
> -	}
> -#endif
> -
>  	start &= PAGE_SECTION_MASK;
>  	mminit_validate_memmodel_limits(&start, &end);
>  	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
> @@ -267,6 +254,19 @@ static void __init memblocks_present(void)
>  	unsigned long start, end;
>  	int i, nid;
>  
> +#ifdef CONFIG_SPARSEMEM_EXTREME
> +	if (unlikely(!mem_section)) {

With the new calling sequence sparse_init() -> memblocks_present() ->
allocate mem_section, mem_section here will be NULL, so this if is not
really relevant. We might want to add WARN_ON_ONCE(mem_section) just in
case to catch multiple calls to sparse_init().

> +		unsigned long size, align;
> +
> +		size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> +		align = 1 << (INTERNODE_CACHE_SHIFT);
> +		mem_section = memblock_alloc(size, align);
> +		if (!mem_section)
> +			panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
> +			      __func__, size, align);
> +	}
> +#endif

> +
>  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
>  		memory_present(nid, start, end);
>  }
> -- 
> 2.41.0
> 

-- 
Sincerely yours,
Mike.