2 files changed, 26 insertions, 6 deletions

diff --git a/fs/inode.c b/fs/inode.c
index f643be565df8..04c785bb63c3 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -665,12 +665,17 @@ void unlock_new_inode(struct inode *inode)
         if (inode->i_mode & S_IFDIR) {
                 struct file_system_type *type = inode->i_sb->s_type;
 
-                /*
-                 * ensure nobody is actually holding i_mutex
-                 */
-                mutex_destroy(&inode->i_mutex);
-                mutex_init(&inode->i_mutex);
-                lockdep_set_class(&inode->i_mutex, &type->i_mutex_dir_key);
+                /* Set new key only if filesystem hasn't already changed it */
+                if (!lockdep_match_class(&inode->i_mutex,
+                    &type->i_mutex_key)) {
+                        /*
+                         * ensure nobody is actually holding i_mutex
+                         */
+                        mutex_destroy(&inode->i_mutex);
+                        mutex_init(&inode->i_mutex);
+                        lockdep_set_class(&inode->i_mutex,
+                                          &type->i_mutex_dir_key);
+                }
         }
 #endif
         /*
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index da5a5a1f4cd2..b25d1b53df0d 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -258,6 +258,16 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
 #define lockdep_set_subclass(lock, sub) \
                 lockdep_init_map(&(lock)->dep_map, #lock, \
                                  (lock)->dep_map.key, sub)
+/*
+ * Compare locking classes
+ */
+#define lockdep_match_class(lock, key) lockdep_match_key(&(lock)->dep_map, key)
+
+static inline int lockdep_match_key(struct lockdep_map *lock,
+                                    struct lock_class_key *key)
+{
+        return lock->key == key;
+}
 
 /*
  * Acquire a lock.
@@ -326,6 +336,11 @@ static inline void lockdep_on(void)
 #define lockdep_set_class_and_subclass(lock, key, sub) \
                 do { (void)(key); } while (0)
 #define lockdep_set_subclass(lock, sub)         do { } while (0)
+/*
+ * We don't define lockdep_match_class() and lockdep_match_key() for !LOCKDEP
+ * case since the result is not well defined and the caller should rather
+ * #ifdef the call himself.
+ */
 
 # define INIT_LOCKDEP
 # define lockdep_reset()                do { debug_locks = 1; } while (0)