Expand comments, no functional change.

Signed-off-by: Mike Kravetz <redacted>
---
  include/linux/hugetlb.h | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index cccd1aab69dd..c0467a7a1fe0 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h

@@ -476,6 +476,9 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
   * huegtlb page specific state flags.  These flags are located in page.private
   * of the hugetlb head page.  Functions created via the below macros should be
   * used to manipulate these flags.
+ * Note: The hugetlb page subpool pointer previously located at page.private
+ * was moved to page[1].private to make room for flags in the head page.  See
+ * hugetlb_page_subpool().
   *
   * HPG_restore_reserve - Set when a hugetlb page consumes a reservation at
   *	allocation time.  Cleared when page is fully instantiated.  Free