[PATCH 1/2] maple_tree: Be more strict about locking

[Liam R. Howlett]

Use lockdep to check the write path in the maple tree holds the lock in
write mode.

Introduce mt_write_lock_is_held() to check if the lock is held for
writing.  Update the necessary checks for rcu_dereference_protected() to
use the new write lock check.

Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
 include/linux/maple_tree.h | 12 ++++++++++--
 lib/maple_tree.c           | 10 ++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 295548cca8b3..f856d67a5d7c 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -184,12 +184,20 @@ enum maple_type {
=20
 #ifdef CONFIG_LOCKDEP
 typedef struct lockdep_map *lockdep_map_p;
-#define mt_lock_is_held(mt)	lock_is_held(mt->ma_external_lock)
+#define mt_write_lock_is_held(mt)					\
+	(!(mt)->ma_external_lock ||					\
+	 lock_is_held_type((mt)->ma_external_lock, 0))
+
+#define mt_lock_is_held(mt)						\
+	(!(mt)->ma_external_lock ||					\
+	 lock_is_held((mt)->ma_external_lock))
+
 #define mt_set_external_lock(mt, lock)					\
 	(mt)->ma_external_lock =3D &(lock)->dep_map
 #else
 typedef struct { /* nothing */ } lockdep_map_p;
-#define mt_lock_is_held(mt)	1
+#define mt_lock_is_held(mt)		1
+#define mt_write_lock_is_held(mt)	1
 #define mt_set_external_lock(mt, lock)	do { } while (0)
 #endif
=20
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index bfffbb7cab26..1c9eab89e34b 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -804,6 +804,12 @@ static inline void __rcu **ma_slots(struct maple_node =
*mn, enum maple_type mt)
 	}
 }
=20
+static inline bool mt_write_locked(const struct maple_tree *mt)
+{
+	return mt_external_lock(mt) ? mt_write_lock_is_held(mt) :
+		lockdep_is_held(&mt->ma_lock);
+}
+
 static inline bool mt_locked(const struct maple_tree *mt)
 {
 	return mt_external_lock(mt) ? mt_lock_is_held(mt) :
@@ -819,7 +825,7 @@ static inline void *mt_slot(const struct maple_tree *mt=
,
 static inline void *mt_slot_locked(struct maple_tree *mt, void __rcu **slo=
ts,
 				   unsigned char offset)
 {
-	return rcu_dereference_protected(slots[offset], mt_locked(mt));
+	return rcu_dereference_protected(slots[offset], mt_write_locked(mt));
 }
 /*
  * mas_slot_locked() - Get the slot value when holding the maple tree lock=
.
@@ -862,7 +868,7 @@ static inline void *mas_root(struct ma_state *mas)
=20
 static inline void *mt_root_locked(struct maple_tree *mt)
 {
-	return rcu_dereference_protected(mt->ma_root, mt_locked(mt));
+	return rcu_dereference_protected(mt->ma_root, mt_write_locked(mt));
 }
=20
 /*
--=20
2.39.2


--qfieyirchnpfqrjg
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="0002-mm-mmap-Change-detached-vma-locking-scheme.patch"
Content-Transfer-Encoding: quoted-printable