[PATCH 2/8] mm/memory: add memory_block_align_range() helper

Gregory Price
2026-03-21T15:04:13Z

Memory hotplug operations require ranges aligned to memory block
boundaries. This is a generic operation for hotplug.

Add memory_block_align_range() as a common helper in <linux/memory.h>
that aligns the start address up and end address down to memory block
boundaries.

Update dax/kmem to use this helper.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
drivers/dax/kmem.c | 4 +---
include/linux/memory.h | 22 ++++++++++++++++++++++
2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index eb693a581961..798f389df992 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -26,9 +26,7 @@ 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_align_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 5bb5599c6b2b..17cdf6ba3823 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 +101,27 @@ 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_align_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_align_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()) - 1;
+
+ return aligned;
+}
+
struct memory_notify {
unsigned long start_pfn;
unsigned long nr_pages;
--
2.53.0