Page blocks might contain references to the next page block. So
a page block cannot be offlined independently. E.g. on x86: page block
size is 2MB, MAX_ORDER -1 (10) allows 4MB allocations.
-> Right now, __offline_isolated_pages() will mark pages in the following
page block as reserved.
Let document offline_pages() while at it.
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
mm/memory_hotplug.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3a8d56476233..1d6054edc241 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1598,11 +1598,14 @@ static int __ref __offline_pages(unsigned long start_pfn,
struct zone *zone;
struct memory_notify arg;
- /* at least, alignment against pageblock is necessary */
if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
return -EINVAL;
+ if (!IS_ALIGNED(start_pfn, (1 << (MAX_ORDER - 1))))
+ return -EINVAL;
if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
return -EINVAL;
+ if (!IS_ALIGNED(end_pfn, (1 << (MAX_ORDER - 1))))
+ 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))
@@ -1699,7 +1702,22 @@ static int __ref __offline_pages(unsigned long start_pfn,
return ret;
}
-/* Must be protected by mem_hotplug_begin() or a device_lock */
+/**
+ * offline_pages - offline pages in a given range (that are currently online)
+ * @start_pfn: start pfn of the memory range
+ * @nr_pages: the number of pages
+ *
+ * This function tries to offline the given pages. The alignment/size that
+ * can be used is max(pageblock_nr_pages, 1 << (MAX_ORDER - 1)).
+ *
+ * Returns 0 if sucessful, -EBUSY if the pages cannot be offlined and
+ * -EINVAL if start_pfn/nr_pages is not properly aligned or not in a zone.
+ * -EINTR is returned if interrupted by a signal.
+ *
+ * Bad things will happen if pages are already offline.
+ *
+ * Must be protected by mem_hotplug_begin() or a device_lock
+ */
int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
{
return __offline_pages(start_pfn, start_pfn + nr_pages);
--
2.14.3
