Have hugetlb_fault() call unlock_page(page) only if it had previously called
lock_page(page).

Signed-off-by: Dean Nelson <dnelson@redhat.com>
CC: stable@kernel.org

---

Setting CONFIG_DEBUG_VM=y and then running the libhugetlbfs test suite,
resulted in the tripping of VM_BUG_ON(!PageLocked(page)) in unlock_page()
having been called by hugetlb_fault() when page == pagecache_page.
This patch remedied the problem.

 mm/hugetlb.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c4a3558..8585524 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2738,7 +2738,8 @@ out_page_table_lock:
 		unlock_page(pagecache_page);
 		put_page(pagecache_page);
 	}
-	unlock_page(page);
+	if (page != pagecache_page)
+		unlock_page(page);
 
 out_mutex:
 	mutex_unlock(&hugetlb_instantiation_mutex);
--
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