[RFC PATCH 3/5] mm/hotplug: Simplify the handling of MHP_MEMMAP_ON_MEMORY flag

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Instead of checking for memmap on memory feature enablement within the
functions checking for alignment, use the kernel parameter to control the
memory hotplug flags. The generic kernel now enables memmap on memory
feature if the hotplug flag request for the same.

The ACPI code now can pass the flag unconditionally because the kernel will
fallback to not using the feature if the alignment rules are not met.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 drivers/acpi/acpi_memhotplug.c |  3 +--
 include/linux/memory_hotplug.h | 14 ++++++++++++++
 mm/memory_hotplug.c            | 19 ++++---------------
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 24f662d8bd39..4d0096fc4cc2 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -211,8 +211,7 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 		if (!info->length)
 			continue;
 
-		if (mhp_supports_memmap_on_memory(info->length))
-			mhp_flags |= MHP_MEMMAP_ON_MEMORY;
+		mhp_flags |= get_memmap_on_memory_flags();
 		result = __add_memory(mgid, info->start_addr, info->length,
 				      mhp_flags);
 
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 2387391ee93a..add3e7829c80 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -362,4 +362,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size);
 bool __mhp_supports_memmap_on_memory(unsigned long size);
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
+#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
+extern bool memmap_on_memory;
+static inline unsigned long get_memmap_on_memory_flags(void)
+{
+	if (memmap_on_memory)
+		return MHP_MEMMAP_ON_MEMORY;
+	return 0;
+}
+#else
+static inline unsigned long get_memmap_on_memory_flags(void)
+{
+	return 0;
+}
+#endif
 #endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 7cb112fb4996..9cfa6fa31df5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -46,19 +46,9 @@
 /*
  * memory_hotplug.memmap_on_memory parameter
  */
-static bool memmap_on_memory __ro_after_init;
+bool memmap_on_memory __ro_after_init;
 module_param(memmap_on_memory, bool, 0444);
 MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
-
-static inline bool mhp_memmap_on_memory(void)
-{
-	return memmap_on_memory;
-}
-#else
-static inline bool mhp_memmap_on_memory(void)
-{
-	return false;
-}
 #endif
 
 enum {
@@ -1317,10 +1307,9 @@ bool __mhp_supports_memmap_on_memory(unsigned long size)
 	 *       altmap as an alternative source of memory, and we do not exactly
 	 *       populate a single PMD.
 	 */
-	return mhp_memmap_on_memory() &&
-	       size == memory_block_size_bytes() &&
-	       IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
-	       IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
+	return size == memory_block_size_bytes() &&
+		IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
+		IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
 }
 
 bool __weak mhp_supports_memmap_on_memory(unsigned long size)
-- 
2.41.0