Re: [PATCH 2/2] base/node: Use curr_node_memblock_intersect_memory_block to Get Memory Block NID if CONFIG_DEFERRED_STRUCT_PAGE_INIT is Set

[Mike Rapoport <rppt@kernel.org>]

On Wed, Apr 09, 2025 at 10:57:57AM +0530, Donet Tom wrote:
> In the current implementation, when CONFIG_DEFERRED_STRUCT_PAGE_INIT is
> set, we iterate over all PFNs in the memory block and use
> early_pfn_to_nid to find the NID until a match is found.
> 
> This patch we are using curr_node_memblock_intersect_memory_block() to
> check if the current node's memblock intersects with the memory block
> passed when CONFIG_DEFERRED_STRUCT_PAGE_INIT is set. If an intersection
> is found, the memory block is added to the current node.
> 
> If CONFIG_DEFERRED_STRUCT_PAGE_INIT is not set, the existing mechanism
> for finding the NID will continue to be used.

I don't think we really need different mechanisms for different settings of
CONFIG_DEFERRED_STRUCT_PAGE_INIT. 

node_dev_init() runs after all struct pages are already initialized and can
always use pfn_to_nid().

kernel_init_freeable() ->
	page_alloc_init_late(); /* completes initialization of deferred pages */
	...
	do_basic_setup() ->
		driver_init() ->
			node_dev_init();

The next step could be refactoring register_mem_block_under_node_early() to
loop over memblock regions rather than over pfns.
 
> Signed-off-by: Donet Tom <donettom@linux.ibm.com>
> ---
>  drivers/base/node.c | 37 +++++++++++++++++++++++++++++--------
>  1 file changed, 29 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index cd13ef287011..5c5dd02b8bdd 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -20,6 +20,8 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/swap.h>
>  #include <linux/slab.h>
> +#include <linux/memblock.h>
> +
>  
>  static const struct bus_type node_subsys = {
>  	.name = "node",
> @@ -782,16 +784,19 @@ static void do_register_memory_block_under_node(int nid,
>  				    ret);
>  }
>  
> -/* register memory section under specified node if it spans that node */
> -static int register_mem_block_under_node_early(struct memory_block *mem_blk,
> -					       void *arg)
> +static int register_mem_block_early_if_dfer_page_init(struct memory_block *mem_blk,
> +				unsigned long start_pfn, unsigned long end_pfn, int nid)
>  {
> -	unsigned long memory_block_pfns = memory_block_size_bytes() / PAGE_SIZE;
> -	unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
> -	unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
> -	int nid = *(int *)arg;
> -	unsigned long pfn;
>  
> +	if (curr_node_memblock_intersect_memory_block(start_pfn, end_pfn, nid))
> +		do_register_memory_block_under_node(nid, mem_blk, MEMINIT_EARLY);
> +	return 0;
> +}
> +
> +static int register_mem_block_early__normal(struct memory_block *mem_blk,
> +				unsigned long start_pfn, unsigned long end_pfn, int nid)
> +{
> +	unsigned long pfn;
>  	for (pfn = start_pfn; pfn <= end_pfn; pfn++) {
>  		int page_nid;
>  
> @@ -821,6 +826,22 @@ static int register_mem_block_under_node_early(struct memory_block *mem_blk,
>  	/* mem section does not span the specified node */
>  	return 0;
>  }
> +/* register memory section under specified node if it spans that node */
> +static int register_mem_block_under_node_early(struct memory_block *mem_blk,
> +					       void *arg)
> +{
> +	unsigned long memory_block_pfns = memory_block_size_bytes() / PAGE_SIZE;
> +	unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
> +	unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
> +	int nid = *(int *)arg;
> +
> +#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> +	if (system_state < SYSTEM_RUNNING)
> +		return register_mem_block_early_if_dfer_page_init(mem_blk, start_pfn, end_pfn, nid);
> +#endif
> +	return register_mem_block_early__normal(mem_blk, start_pfn, end_pfn, nid);
> +
> +}
>  
>  /*
>   * During hotplug we know that all pages in the memory block belong to the same
> -- 
> 2.48.1
> 

-- 
Sincerely yours,
Mike.