X-Git-Url: http://review.tizen.org/git/?a=blobdiff_plain;f=mm%2Fhugetlb.c;h=49e693b7fd0c695aeced27be87ab7ed0ae98e8d0;hb=ef009b25f4f8a77d2b32067d424d5ac757dcdc5b;hp=7acd12503f734bfcaff2c4fed244e594952962ea;hpb=979ecef5b89a8003902299566d9cdc08de34a3ee;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7acd125..49e693b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2349,6 +2349,9 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
 
 /*
  * Hugetlb_cow() should be called with page lock of the original hugepage held.
+ * Called with hugetlb_instantiation_mutex held and pte_page locked so we
+ * cannot race with other handlers or page migration.
+ * Keep the pte_same checks anyway to make transition from the mutex easier.
  */
 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pte_t *ptep, pte_t pte,
@@ -2408,7 +2411,14 @@ retry_avoidcopy:
 				BUG_ON(page_count(old_page) != 1);
 				BUG_ON(huge_pte_none(pte));
 				spin_lock(&mm->page_table_lock);
-				goto retry_avoidcopy;
+				ptep = huge_pte_offset(mm, address & huge_page_mask(h));
+				if (likely(pte_same(huge_ptep_get(ptep), pte)))
+					goto retry_avoidcopy;
+				/*
+				 * race occurs while re-acquiring page_table_lock, and
+				 * our job is done.
+				 */
+				return 0;
 			}
 			WARN_ON_ONCE(1);
 		}