From 0332d1bd067112143fcc7c997835268c0dd909c0 Mon Sep 17 00:00:00 2001
From: Nick Piggin <npiggin@kernel.dk>
Date: Fri, 7 Jan 2011 17:49:44 +1100
Subject: [PATCH] --- yaml --- r: 226716 b: refs/heads/master c:
 a734eb458ab2bd11479a27dd54f48e1b26a55845 h: refs/heads/master v: v3

---
 [refs]            |  2 +-
 trunk/fs/dcache.c | 21 ++++++++++++---------
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/[refs] b/[refs]
index d8cc70e99f98..1a8da51dd54d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: dc0474be3e27463d4d4a2793f82366eed906f223
+refs/heads/master: a734eb458ab2bd11479a27dd54f48e1b26a55845
diff --git a/trunk/fs/dcache.c b/trunk/fs/dcache.c
index b4d2e28eef5b..a8f89765d602 100644
--- a/trunk/fs/dcache.c
+++ b/trunk/fs/dcache.c
@@ -446,24 +446,27 @@ struct dentry *dget_parent(struct dentry *dentry)
 	struct dentry *ret;
 
 repeat:
-	spin_lock(&dentry->d_lock);
+	/*
+	 * Don't need rcu_dereference because we re-check it was correct under
+	 * the lock.
+	 */
+	rcu_read_lock();
 	ret = dentry->d_parent;
-	if (!ret)
-		goto out;
-	if (dentry == ret) {
-		ret->d_count++;
+	if (!ret) {
+		rcu_read_unlock();
 		goto out;
 	}
-	if (!spin_trylock(&ret->d_lock)) {
-		spin_unlock(&dentry->d_lock);
-		cpu_relax();
+	spin_lock(&ret->d_lock);
+	if (unlikely(ret != dentry->d_parent)) {
+		spin_unlock(&ret->d_lock);
+		rcu_read_unlock();
 		goto repeat;
 	}
+	rcu_read_unlock();
 	BUG_ON(!ret->d_count);
 	ret->d_count++;
 	spin_unlock(&ret->d_lock);
 out:
-	spin_unlock(&dentry->d_lock);
 	return ret;
 }
 EXPORT_SYMBOL(dget_parent);