Re: [PATCH 2/3] mm/memblock: repeat setting reserved region nid if array is doubled

[Mike Rapoport <rppt@kernel.org>]

Hi Wei,

On Wed, Mar 12, 2025 at 01:07:27PM +0000, Wei Yang wrote:
> Commit 61167ad5fecd ("mm: pass nid to reserve_bootmem_region()") introduce
> a way to set nid to all reserved region.
> 
> But there is a corner case it will leave some region with invalid nid.
> When memblock_set_node() doubles the array of memblock.reserved, it may
> lead to a new reserved region before current position. The new region
> will be left with an invalid node id.
> 
> Repeat the process when detecting it.
> 
> Fixes: 61167ad5fecd ("mm: pass nid to reserve_bootmem_region()")
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> CC: Mike Rapoport <rppt@kernel.org>
> CC: Yajun Deng <yajun.deng@linux.dev>
> CC: <stable@vger.kernel.org>
> ---
>  mm/memblock.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 85442f1b7f14..302dd7bc622d 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -2184,7 +2184,10 @@ static void __init memmap_init_reserved_pages(void)
>  	 * set nid on all reserved pages and also treat struct
>  	 * pages for the NOMAP regions as PageReserved
>  	 */
> +repeat:
>  	for_each_mem_region(region) {
> +		unsigned long max = memblock.reserved.max;
> +
>  		nid = memblock_get_region_node(region);
>  		start = region->base;
>  		end = start + region->size;
> @@ -2193,6 +2196,15 @@ static void __init memmap_init_reserved_pages(void)
>  			reserve_bootmem_region(start, end, nid);
>  
>  		memblock_set_node(start, region->size, &memblock.reserved, nid);
> +
> +		/*
> +		 * 'max' is changed means memblock.reserved has been doubled
> +		 * its array, which may result a new reserved region before
> +		 * current 'start'. Now we should repeat the procedure to set
> +		 * its node id.
> +		 */
> +		if (max != memblock.reserved.max)
> +			goto repeat;

This check can be moved outside the loop, can't it?

>  	}
>  
>  	/*
> -- 
> 2.34.1
> 

-- 
Sincerely yours,
Mike.