From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/hugetlb.c |    5 +++++
 1 files changed, 5 insertions(+)

diff -puN mm/hugetlb.c~__unmap_hugepage_range-add-comment mm/hugetlb.c
--- a/mm/hugetlb.c~__unmap_hugepage_range-add-comment
+++ a/mm/hugetlb.c
@@ -365,6 +365,11 @@ void __unmap_hugepage_range(struct vm_ar
 	pte_t pte;
 	struct page *page;
 	struct page *tmp;
+	/*
+	 * A page gathering list, protected by per file i_mmap_lock. The
+	 * lock is used to avoid list corruption from multiple unmapping
+	 * of the same page since we are using page->lru.
+	 */
 	LIST_HEAD(page_list);
 
 	WARN_ON(!is_vm_hugetlb_page(vma));
_