[PATCH v1 3/5] mm/memory_hotplug: check if sections are already online/offline

[David Hildenbrand]

Let's add some more sanity checking now that onlining/offlining code
works completely on section basis. This will make sure that we will
never try to online/offline sections that are already (or partially) in
the desired state.

Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 include/linux/mmzone.h |  2 ++
 mm/memory_hotplug.c    |  5 +++++
 mm/sparse.c            | 28 ++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 0859130e4db8..addfa41c047a 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1228,6 +1228,8 @@ static inline int online_section_nr(unsigned long nr)
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
+bool mem_sections_online(unsigned long pfn, unsigned long end_pfn);
+bool mem_sections_offline(unsigned long pfn, unsigned long end_pfn);
 void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
 #ifdef CONFIG_MEMORY_HOTREMOVE
 void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 30d2fa42b0bb..3dc6d2a309c2 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -901,6 +901,8 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 		return -EINVAL;
 	if (!IS_ALIGNED(nr_pages, PAGES_PER_SECTION))
 		return -EINVAL;
+	if (!mem_sections_offline(pfn, pfn + nr_pages))
+		return -EINVAL;
 
 	/*
 	 * We can't use pfn_to_nid() because nid might be stored in struct page
@@ -1609,6 +1611,9 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 		return -EINVAL;
 	if (!IS_ALIGNED(nr_pages, PAGES_PER_SECTION))
 		return -EINVAL;
+	if (!mem_sections_online(start_pfn, end_pfn))
+		return -EINVAL;
+
 	/* This makes hotplug much easier...and readable.
 	   we assume this for now. .*/
 	if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end))
diff --git a/mm/sparse.c b/mm/sparse.c
index 10b07eea9a6e..44693cf38ca9 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -520,6 +520,34 @@ void __init sparse_init(void)
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 
+/* check if all mem sections are online */
+bool mem_sections_online(unsigned long pfn, unsigned long end_pfn)
+{
+	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		unsigned long section_nr = pfn_to_section_nr(pfn);
+
+		if (WARN_ON(!valid_section_nr(section_nr)))
+			continue;
+		if (!online_section_nr(section_nr))
+			return false;
+	}
+	return true;
+}
+
+/* check if all mem sections are offline */
+bool mem_sections_offline(unsigned long pfn, unsigned long end_pfn)
+{
+	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		unsigned long section_nr = pfn_to_section_nr(pfn);
+
+		if (WARN_ON(!valid_section_nr(section_nr)))
+			continue;
+		if (online_section_nr(section_nr))
+			return false;
+	}
+	return true;
+}
+
 /* Mark all memory sections within the pfn range as online */
 void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
 {
-- 
2.17.1