[PATCH v2 18/20] mm, hugetlb: clean-up error handling in hugetlb_cow()

[Joonsoo Kim <iamjoonsoo.kim@lge.com>]

Current code include 'Caller expects lock to be held' in every error path.
We can clean-up it as we do error handling in one place.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7e9a651..8743e5c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2500,6 +2500,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 	int outside_reserve = 0;
 	long chg;
 	bool use_reserve = false;
+	int ret = 0;
 	unsigned long mmun_start;	/* For mmu_notifiers */
 	unsigned long mmun_end;		/* For mmu_notifiers */
 
@@ -2524,10 +2525,8 @@ retry_avoidcopy:
 	 * anon_vma prepared.
 	 */
 	if (unlikely(anon_vma_prepare(vma))) {
-		page_cache_release(old_page);
-		/* Caller expects lock to be held */
-		spin_lock(&mm->page_table_lock);
-		return VM_FAULT_OOM;
+		ret = VM_FAULT_OOM;
+		goto out_old_page;
 	}
 
 	/*
@@ -2546,11 +2545,8 @@ retry_avoidcopy:
 	if (!outside_reserve) {
 		chg = vma_needs_reservation(h, vma, address);
 		if (chg == -ENOMEM) {
-			page_cache_release(old_page);
-
-			/* Caller expects lock to be held */
-			spin_lock(&mm->page_table_lock);
-			return VM_FAULT_OOM;
+			ret = VM_FAULT_OOM;
+			goto out_old_page;
 		}
 		use_reserve = !chg;
 	}
@@ -2584,9 +2580,8 @@ retry_avoidcopy:
 			WARN_ON_ONCE(1);
 		}
 
-		/* Caller expects lock to be held */
-		spin_lock(&mm->page_table_lock);
-		return VM_FAULT_SIGBUS;
+		ret = VM_FAULT_SIGBUS;
+		goto out_lock;
 	}
 
 	copy_user_huge_page(new_page, old_page, address, vma,
@@ -2617,11 +2612,12 @@ retry_avoidcopy:
 	spin_unlock(&mm->page_table_lock);
 	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 	page_cache_release(new_page);
+out_old_page:
 	page_cache_release(old_page);
-
+out_lock:
 	/* Caller expects lock to be held */
 	spin_lock(&mm->page_table_lock);
-	return 0;
+	return ret;
 }
 
 /* Return the pagecache page at a given address within a VMA */
-- 
1.7.9.5

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