[PATCH] mm,memory_hotplug: Explicitly pass the head to isolate_huge_page

[Oscar Salvador]

isolate_huge_page() expects we pass the head of hugetlb page to it:

bool isolate_huge_page(...)
{
        ...
        VM_BUG_ON_PAGE(!PageHead(page), page);
        ...
}

While I really cannot think of any situation where we end up with a
non-head page between hands in do_migrate_range(), let us make sure
the code is as sane as possible by explicitly passing the Head.
Since we already got the pointer, it does not take us extra effort.

Signed-off-by: Oscar Salvador <osalva...@suse.de>
---
 mm/memory_hotplug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 656ff386ac15..d5f7afda67db 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1378,12 +1378,12 @@ do_migrate_range(unsigned long start_pfn, unsigned long 
end_pfn)
 
                if (PageHuge(page)) {
                        struct page *head = compound_head(page);
-                       pfn = page_to_pfn(head) + (1<<compound_order(head)) - 1;
                        if (compound_order(head) > PFN_SECTION_SHIFT) {
                                ret = -EBUSY;
                                break;
                        }
-                       isolate_huge_page(page, &source);
+                       pfn = page_to_pfn(head) + (1<<compound_order(head)) - 1;
+                       isolate_huge_page(head, &source);
                        continue;
                } else if (PageTransHuge(page))
                        pfn = page_to_pfn(compound_head(page))
-- 
2.13.7