Re: [PATCH v6 01/10] mm/memory: add memory_block_aligned_range() helper

[Dave Jiang <dave.jiang@intel.com>]

On 6/30/26 2:18 PM, Gregory Price wrote:
> Memory hotplug operations require ranges aligned to memory block
> boundaries.  This is a generic operation for hotplug.
> 
> Add memory_block_aligned_range() as a common helper in <linux/memory.h>
> that aligns the start address up and end address down to memory block
> boundaries.  Guard against end underflow when the range falls below the
> first memory block boundary, returning an empty range instead.
> 
> Update dax/kmem to use this helper.
> 
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  drivers/dax/kmem.c     |  4 +---
>  include/linux/memory.h | 27 +++++++++++++++++++++++++++
>  2 files changed, 28 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index a18e2b968e4d..592171ec10f4 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -33,9 +33,7 @@ static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
>  	struct dev_dax_range *dax_range = &dev_dax->ranges[i];
>  	struct range *range = &dax_range->range;
>  
> -	/* memory-block align the hotplug range */
> -	r->start = ALIGN(range->start, memory_block_size_bytes());
> -	r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
> +	*r = memory_block_aligned_range(range);
>  	if (r->start >= r->end) {
>  		r->start = range->start;
>  		r->end = range->end;
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 463dc02f6cff..1783299073e4 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -20,6 +20,7 @@
>  #include <linux/compiler.h>
>  #include <linux/mutex.h>
>  #include <linux/memory_hotplug.h>
> +#include <linux/range.h>
>  
>  #define MIN_MEMORY_BLOCK_SIZE     (1UL << SECTION_SIZE_BITS)
>  
> @@ -100,6 +101,32 @@ int arch_get_memory_phys_device(unsigned long start_pfn);
>  unsigned long memory_block_size_bytes(void);
>  int set_memory_block_size_order(unsigned int order);
>  
> +/**
> + * memory_block_aligned_range - align a physical address range to memory blocks
> + * @range: the input range to align
> + *
> + * Aligns the start address up and the end address down to memory block
> + * boundaries. This is required for memory hotplug operations which must
> + * operate on memory-block aligned ranges.
> + *
> + * Returns the aligned range. Callers should check that the returned
> + * range is valid (aligned.start < aligned.end) before using it.
> + */
> +static inline struct range memory_block_aligned_range(const struct range *range)
> +{
> +	struct range aligned;
> +
> +	aligned.start = ALIGN(range->start, memory_block_size_bytes());
> +	aligned.end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes());
> +	/* No whole block fits (e.g. range below the first boundary): empty. */
> +	if (aligned.end <= aligned.start)
> +		aligned.start = aligned.end;
> +	else
> +		aligned.end -= 1;
> +
> +	return aligned;
> +}
> +
>  struct memory_notify {
>  	unsigned long start_pfn;
>  	unsigned long nr_pages;