[PATCH 1/3] mm,memory_hotplug: export mhp min alignment

[Max Gurtovoy <mgurtovoy@nvidia.com>]

Hotplugged memory has alignmet restrictions. E.g, it disallows all
operations smaller than a sub-section and only allow operations smaller
than a section for SPARSEMEM_VMEMMAP. Export the alignment restrictions
for mhp users.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
---
 include/linux/memory_hotplug.h |  5 +++++
 mm/memory_hotplug.c            | 33 +++++++++++++++++++--------------
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 28f32fd00fe9..c55a9049b11e 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -76,6 +76,7 @@ struct mhp_params {
 
 bool mhp_range_allowed(u64 start, u64 size, bool need_mapping);
 struct range mhp_get_pluggable_range(bool need_mapping);
+unsigned long mhp_get_min_align(void);
 
 /*
  * Zone resizing functions
@@ -248,6 +249,10 @@ void mem_hotplug_done(void);
 	___page;				\
  })
 
+static inline unsigned long mhp_get_min_align(void)
+{
+	return 0;
+}
 static inline unsigned zone_span_seqbegin(struct zone *zone)
 {
 	return 0;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9e86e9ee0a10..161bb6704a9b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -270,24 +270,29 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
 }
 #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
 
+/*
+ * Disallow all operations smaller than a sub-section and only
+ * allow operations smaller than a section for
+ * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
+ * enforces a larger memory_block_size_bytes() granularity for
+ * memory that will be marked online, so this check should only
+ * fire for direct arch_{add,remove}_memory() users outside of
+ * add_memory_resource().
+ */
+unsigned long mhp_get_min_align(void)
+{
+	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
+		return PAGES_PER_SUBSECTION;
+	return PAGES_PER_SECTION;
+}
+EXPORT_SYMBOL_GPL(mhp_get_min_align);
+
+
 static int check_pfn_span(unsigned long pfn, unsigned long nr_pages,
 		const char *reason)
 {
-	/*
-	 * Disallow all operations smaller than a sub-section and only
-	 * allow operations smaller than a section for
-	 * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
-	 * enforces a larger memory_block_size_bytes() granularity for
-	 * memory that will be marked online, so this check should only
-	 * fire for direct arch_{add,remove}_memory() users outside of
-	 * add_memory_resource().
-	 */
-	unsigned long min_align;
+	unsigned long min_align = mhp_get_min_align();
 
-	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
-		min_align = PAGES_PER_SUBSECTION;
-	else
-		min_align = PAGES_PER_SECTION;
 	if (!IS_ALIGNED(pfn, min_align) || !IS_ALIGNED(nr_pages, min_align)) {
 		WARN(1, "Misaligned __%s_pages min_align: %#lx start: %#lx end: %#lx\n",
 		     reason, min_align, pfn, pfn + nr_pages - 1);
-- 
2.18.1