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 <[email protected]>
> Acked-by: David Hildenbrand (Arm) <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
> ---
> 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;
