[PATCH 02/17] locking: Add split_lock

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Bitlocks do not currently participate in lockdep.  Conceptually, a
bit_spinlock is a split lock, eg across each bucket in a hash table.
The struct split_lock gives us somewhere to record the lockdep_map.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/split_lock.h | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 include/linux/split_lock.h

diff --git a/include/linux/split_lock.h b/include/linux/split_lock.h
new file mode 100644
index 000000000000..8d64cfa0bbad
--- /dev/null
+++ b/include/linux/split_lock.h
@@ -0,0 +1,37 @@
+#ifndef _LINUX_SPLIT_LOCK_H
+#define _LINUX_SPLIT_LOCK_H
+
+#include <linux/lockdep_types.h>
+
+struct split_lock {
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map dep_map;
+#endif
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define SPLIT_DEP_MAP_INIT(lockname)					\
+	.dep_map = {							\
+		.name = #lockname,					\
+		.wait_type_inner = LD_WAIT_SPIN,			\
+	}
+#else
+#define SPLIT_DEP_MAP_INIT(lockname)
+#endif
+
+#define DEFINE_SPLIT_LOCK(name)						\
+struct split_lock name = {						\
+	SPLIT_DEP_MAP_INIT(name)					\
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define split_lock_init(_lock) do {					\
+	static struct lock_class_key __key;				\
+	lockdep_init_map_wait(&(_lock)->dep_map, #_lock, &__key, 0,	\
+				LD_WAIT_SPIN);				\
+} while (0)
+#else
+static inline void split_lock_init(struct split_lock *sl) { }
+#endif
+
+#endif /* _LINUX_SPLIT_LOCK_H */
-- 
2.30.2