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Subject[PATCH v10 2/8] mm,memory_hotplug: Relax fully spanned sections check
Date
We want {online,offline}_pages to operate on whole memblocks, but
memmap_on_memory will poke pageblock_nr_pages aligned holes in the
beginning, which is a special case we want to allow.
Relax the check to account for that case.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
mm/memory_hotplug.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0cdbbfbc5757..e6aafd17a01a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -838,9 +838,16 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
int ret;
struct memory_notify arg;

- /* We can only online full sections (e.g., SECTION_IS_ONLINE) */
+ /*
+ * {on,off}lining is constrained to full memory sections (or more
+ * precisly to memory blocks from the user space POV).
+ * memmap_on_memory is an exception because it reserves initial part
+ * of the physical memory space for vmemmaps. That space is pageblock
+ * aligned.
+ */
if (WARN_ON_ONCE(!nr_pages ||
- !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
+ !IS_ALIGNED(pfn, pageblock_nr_pages) ||
+ !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
return -EINVAL;

mem_hotplug_begin();
@@ -1573,9 +1580,16 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
int ret, node;
char *reason;

- /* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
+ /*
+ * {on,off}lining is constrained to full memory sections (or more
+ * precisly to memory blocks from the user space POV).
+ * memmap_on_memory is an exception because it reserves initial part
+ * of the physical memory space for vmemmaps. That space is pageblock
+ * aligned.
+ */
if (WARN_ON_ONCE(!nr_pages ||
- !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
+ !IS_ALIGNED(start_pfn, pageblock_nr_pages) ||
+ !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
return -EINVAL;

mem_hotplug_begin();
--
2.16.3
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