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

[Wei Yang <richard.weiyang@gmail.com>]

On Sun, Mar 16, 2025 at 05:32:35PM +0200, Mike Rapoport wrote:
>On Fri, Mar 14, 2025 at 02:03:51AM +0000, Wei Yang wrote:
>> On Thu, Mar 13, 2025 at 05:07:59PM +0200, Mike Rapoport 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?
>> >
>> 
>> We can. You mean something like this?
>
>Yes, something like this.
> 
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index 85442f1b7f14..67fd1695cce4 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -2179,11 +2179,14 @@ static void __init memmap_init_reserved_pages(void)
>>  	struct memblock_region *region;
>>  	phys_addr_t start, end;
>>  	int nid;
>> +	unsigned long max;
>
>maybe max_reserved?

Sure, will update it.

>>  
>>  	/*
>>  	 * set nid on all reserved pages and also treat struct
>>  	 * pages for the NOMAP regions as PageReserved
>>  	 */
>> +repeat:
>> +	max = memblock.reserved.max;
>>  	for_each_mem_region(region) {
>>  		nid = memblock_get_region_node(region);
>>  		start = region->base;
>> @@ -2194,6 +2197,13 @@ static void __init memmap_init_reserved_pages(void)
>>  
>>  		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;
>>  
>>  	/*
>>  	 * initialize struct pages for reserved regions that don't have
>> -- 
>> Wei Yang
>> Help you, Help me
>
>-- 
>Sincerely yours,
>Mike.

-- 
Wei Yang
Help you, Help me