[PATCH v3 11/14] mm, hugetlb: move up anon_vma_prepare()

[Joonsoo Kim]

If we fail with a allocated hugepage, we need some effort to recover
properly. So, it is better not to allocate a hugepage as much as possible.
So move up anon_vma_prepare() which can be failed in OOM situation.

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 03ab285..1817720 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2597,6 +2597,17 @@ retry_avoidcopy:
 	spin_unlock(ptl);
 
 	/*
+	 * When the original hugepage is shared one, it does not have
+	 * anon_vma prepared.
+	 */
+	if (unlikely(anon_vma_prepare(vma))) {
+		page_cache_release(old_page);
+		/* Caller expects lock to be held */
+		spin_lock(ptl);
+		return VM_FAULT_OOM;
+	}
+
+	/*
 	 * If the process that created a MAP_PRIVATE mapping is about to
 	 * perform a COW due to a shared page count, attempt to satisfy
 	 * the allocation without using the existing reserves. The pagecache
@@ -2655,18 +2666,6 @@ retry_avoidcopy:
 		return VM_FAULT_SIGBUS;
 	}
 
-	/*
-	 * When the original hugepage is shared one, it does not have
-	 * anon_vma prepared.
-	 */
-	if (unlikely(anon_vma_prepare(vma))) {
-		page_cache_release(new_page);
-		page_cache_release(old_page);
-		/* Caller expects lock to be held */
-		spin_lock(ptl);
-		return VM_FAULT_OOM;
-	}
-
 	copy_user_huge_page(new_page, old_page, address, vma,
 			    pages_per_huge_page(h));
 	__SetPageUptodate(new_page);
-- 
1.7.9.5

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