From: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Wed, 20 Oct 2021 12:49:48 +0000 (-0400)
Subject: maple tree: Support lockdep validation of external locks
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=9738bd0f6816ca04c75c0e8895346cca5ef3f932;p=users%2Fwilly%2Flinux.git

maple tree: Support lockdep validation of external locks

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 7fc49ad3b34d..23b8b6dc658e 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -160,7 +160,12 @@ enum maple_type {
 #define MAPLE_RESERVED_RANGE	4096
 
 struct maple_tree {
-	spinlock_t	ma_lock;
+	union {
+		spinlock_t	ma_lock;
+#ifdef CONFIG_LOCKDEP
+		struct lockdep_map *ma_external_lock;
+#endif
+	};
 	unsigned int	ma_flags;
 	void __rcu      *ma_root;
 };
@@ -172,11 +177,27 @@ struct maple_tree {
 	.ma_root = NULL,						\
 }
 
+#ifdef CONFIG_LOCKDEP
+#define MTREE_INIT_EXT(name, flags, lock) {				\
+	.ma_external_lock = &(lock).dep_map,				\
+	.ma_flags = flags,						\
+	.ma_root = NULL,						\
+}
+#else
+#define MTREE_INIT_EXT(name, flags, lock)	MTREE_INIT(name, flags)
+#endif
+
 #define DEFINE_MTREE(name)						\
 	struct maple_tree name = MTREE_INIT(name, 0)
 
 #define mtree_lock(mt)		spin_lock((&(mt)->ma_lock))
 #define mtree_unlock(mt)	spin_unlock((&(mt)->ma_lock))
+#ifdef CONFIG_LOCKDEP
+#define mt_set_external_lock(mt, lock)					\
+	(mt)->ma_external_lock = &(lock)->dep_map;
+#else
+#define mt_set_external_lock(mt, lock)	do { } while (0)
+#endif
 
 struct maple_node {
 	union {
@@ -388,22 +409,33 @@ static inline void mas_set(struct ma_state *mas, unsigned long index)
 	mas_set_range(mas, index, index);
 }
 
+static inline bool mt_external_lock(const struct maple_tree *mt)
+{
+	return (mt->ma_flags & MT_FLAGS_LOCK_MASK) == MT_FLAGS_LOCK_EXTERN;
+}
+
 /**
  * mt_init_flags() - Initialise an empty maple tree with flags.
  * @mt: Maple Tree
  * @flags: maple tree flags.
  *
- * If you need to initialise a Maple Tree with special falgs (eg, an
+ * If you need to initialise a Maple Tree with special flags (eg, an
  * allocation tree), use this function.
  *
  * Context: Any context.
- *
  */
 static inline void mt_init_flags(struct maple_tree *mt, unsigned int flags)
 {
-	spin_lock_init(&mt->ma_lock);
 	mt->ma_flags = flags;
-	mt->ma_root = NULL;
+	if (mt_external_lock(mt))
+#ifdef CONFIG_LOCKDEP
+		mt->ma_external_lock = NULL;
+#else
+		do { } while (0);
+#endif
+	else
+		spin_lock_init(&mt->ma_lock);
+	rcu_assign_pointer(mt->ma_root, NULL);
 }
 
 /**
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index c9dd1ceb5c67..20ed92e86a55 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -747,14 +747,15 @@ static inline void __rcu **ma_slots(struct maple_node *mn, enum maple_type mt)
 	}
 }
 
-static inline bool mt_external_lock(const struct maple_tree *mt)
-{
-	return (mt->ma_flags & MT_FLAGS_LOCK_MASK) == MT_FLAGS_LOCK_EXTERN;
-}
-
 static inline bool mt_locked(const struct maple_tree *mt)
 {
-	return mt_external_lock(mt) || lockdep_is_held(&mt->ma_lock);
+#ifdef CONFIG_LOCKDEP
+	return mt_external_lock(mt) ?
+		lock_is_held(mt->ma_external_lock) :
+		lockdep_is_held(&mt->ma_lock);
+#else
+	return true;
+#endif
 }
 
 static inline void *mt_slot(const struct maple_tree *mt,
@@ -5451,6 +5452,7 @@ static void **mas_dead_walk(struct ma_state *mas, unsigned char offset)
 
 	return slots;
 }
+
 static void mt_free_walk(struct rcu_head *head)
 {
 	void __rcu **slots;
@@ -5464,7 +5466,7 @@ static void mt_free_walk(struct rcu_head *head)
 	if (ma_is_leaf(node->type))
 		goto free_leaf;
 
-	mtree_init(&mt, node->ma_flags);
+	mt_init_flags(&mt, node->ma_flags);
 	mas_lock(&mas);
 	start = node;
 	mas.node = mt_mk_node(node, node->type);
@@ -5528,7 +5530,7 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
 	if (mte_is_leaf(enode))
 		goto free_leaf;
 
-	mtree_init(&mt, ma_flags);
+	mt_init_flags(&mt, ma_flags);
 	mas_lock(&mas);
 
 	mas.node = start = enode;
@@ -5965,19 +5967,6 @@ void __init maple_tree_init(void)
 			SLAB_PANIC, NULL);
 }
 
-/*
- * mtree_init() - Initialize a maple tree.
- * @mt: The maple tree
- * @ma_flags: The flags to use for the tree.
- */
-void mtree_init(struct maple_tree *mt, unsigned int ma_flags)
-{
-	mt->ma_flags = ma_flags;
-	spin_lock_init(&mt->ma_lock);
-	rcu_assign_pointer(mt->ma_root, NULL);
-}
-EXPORT_SYMBOL(mtree_init);
-
 /*
  * mtree_load() - Load a value stored in a maple tree
  * @mt: The maple tree