[PATCH 3/3] maple_tree: assert static storage for DEFINE_MTREE()

[Yury Norov]

DEFINE_MTREE() uses MTREE_INIT(), which initializes the tree's embedded
lock with a static spinlock initializer. If the tree is an automatic
local object, lockdep rejects its address as a non-static class key and
disables locking validation on the first lock acquisition.

Apply ASSERT_STATIC_STORAGE() to DEFINE_MTREE() to catch automatic
local definitions at compile time. For example:

  void example(void)
  {
          DEFINE_MTREE(mt);
          mtree_destroy(&mt);
  }

GCC reports:

  error: initializer element is not constant
    name##_storage_check = &(name)
                           ^
  note: in expansion of macro 'ASSERT_STATIC_STORAGE'
    ASSERT_STATIC_STORAGE(name)
  note: in expansion of macro 'DEFINE_MTREE'
    DEFINE_MTREE(mt);

File-scope definitions and static local trees remain valid. Automatic
local trees must instead use mt_init() or mt_init_flags(). Direct uses of
MTREE_INIT() and MTREE_INIT_EXT() are unchanged.

Replace the local DEFINE_MTREE() in the interval-tree span test with a
plain declaration; the test already initializes the tree with
mt_init_flags() before use. Convert the three local Maple Trees in the
userspace radix-tree tests to mt_init().

Validated file-scope and static local definitions with a kernel object
build, and confirmed that an automatic local definition fails to compile.
The Maple Tree test and region allocation benchmark objects also build
with lockdep enabled.

Signed-off-by: Yury Norov <ynorov@xxxxxxxxxx>
---
 include/linux/maple_tree.h       |  4 +++-
 lib/interval_tree_test.c         |  2 +-
 tools/testing/radix-tree/maple.c | 12 +++++++++---
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index e595ae5cd0ee..e30e57f5f3df 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -9,6 +9,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/compiler.h>
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>
 
@@ -297,7 +298,8 @@ struct maple_tree {
 #endif
 
 #define DEFINE_MTREE(name)						\
-	struct maple_tree name = MTREE_INIT(name, 0)
+	struct maple_tree name = MTREE_INIT(name, 0);		\
+	ASSERT_STATIC_STORAGE(name)
 
 #define mtree_lock(mt)		spin_lock((&(mt)->ma_lock))
 #define mtree_lock_nested(mas, subclass) \
diff --git a/lib/interval_tree_test.c b/lib/interval_tree_test.c
index b0b07270ce7c..06f77fb3179f 100644
--- a/lib/interval_tree_test.c
+++ b/lib/interval_tree_test.c
@@ -244,7 +244,7 @@ static int span_iteration_check(void)
 	unsigned long start, last;
 	struct interval_tree_span_iter span, mas_span;
 
-	DEFINE_MTREE(tree);
+	struct maple_tree tree;
 
 	MA_STATE(mas, &tree, 0, 0);
 
diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index d967e76a3c06..bfe4b8626c42 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -36022,10 +36022,12 @@ static noinline void __init check_erase_rebalance(struct maple_tree *mt)
 
 static noinline void __init check_mtree_dup(struct maple_tree *mt)
 {
-	DEFINE_MTREE(new);
+	struct maple_tree new;
 	int i, j, ret, count = 0;
 	unsigned int rand_seed = 17, rand;
 
+	mt_init(&new);
+
 	/* store a value at [0, 0] */
 	mt_init_flags(mt, 0);
 	mtree_store_range(mt, 0, 0, xa_mk_value(0), GFP_KERNEL);
@@ -36319,7 +36321,9 @@ static inline int check_vma_modification(struct maple_tree *mt)
 void farmer_tests(void)
 {
 	struct maple_node *node;
-	DEFINE_MTREE(tree);
+	struct maple_tree tree;
+
+	mt_init(&tree);
 
 	mt_dump(&tree, mt_dump_dec);
 
@@ -36432,9 +36436,11 @@ static unsigned long get_last_index(struct ma_state *mas)
 static void test_spanning_store_regression(void)
 {
 	unsigned long from = 0, to = 0;
-	DEFINE_MTREE(tree);
+	struct maple_tree tree;
 	MA_STATE(mas, &tree, 0, 0);
 
+	mt_init(&tree);
+
 	/*
 	 * Build a 3-level tree. We require a parent node below the root node
 	 * and 2 leaf nodes under it, so we can span the entirety of the right
-- 
2.53.0