__create_object() consists of two part, the first part allocate a
kmemleak object and initialize it, the second part insert it into
object tree. This function need kmemleak_lock but actually only the
second part need lock.

Split it into two functions, the first function __alloc_object only
allocate a kmemleak object, and the second function __link_object()
will initialize the object and insert it into object tree, use the
kmemleak_lock to protect __link_object() only.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
---
 mm/kmemleak.c | 61 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 40 insertions(+), 21 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 289b3be5ee6e..064fc3695c6b 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -623,25 +623,15 @@ static noinline depot_stack_handle_t set_track_prepare(void)
 	return trace_handle;
 }
 
-/*
- * Create the metadata (struct kmemleak_object) corresponding to an allocated
- * memory block and add it to the object_list and object_tree_root (or
- * object_phys_tree_root).
- */
-static void __create_object(unsigned long ptr, size_t size,
-			    int min_count, gfp_t gfp, bool is_phys)
+static struct kmemleak_object * __alloc_object(gfp_t gfp)
 {
-	unsigned long flags;
-	struct kmemleak_object *object, *parent;
-	struct rb_node **link, *rb_parent;
-	unsigned long untagged_ptr;
-	unsigned long untagged_objp;
+	struct kmemleak_object *object;
 
 	object = mem_pool_alloc(gfp);
 	if (!object) {
 		pr_warn("Cannot allocate a kmemleak_object structure\n");
 		kmemleak_disable();
-		return;
+		return NULL;
 	}
 
 	INIT_LIST_HEAD(&object->object_list);
@@ -649,13 +639,8 @@ static void __create_object(unsigned long ptr, size_t size,
 	INIT_HLIST_HEAD(&object->area_list);
 	raw_spin_lock_init(&object->lock);
 	atomic_set(&object->use_count, 1);
-	object->flags = OBJECT_ALLOCATED | (is_phys ? OBJECT_PHYS : 0);
-	object->pointer = ptr;
-	object->size = kfence_ksize((void *)ptr) ?: size;
 	object->excess_ref = 0;
-	object->min_count = min_count;
 	object->count = 0;			/* white color initially */
-	object->jiffies = jiffies;
 	object->checksum = 0;
 	object->del_state = 0;
 
@@ -680,7 +665,23 @@ static void __create_object(unsigned long ptr, size_t size,
 	/* kernel backtrace */
 	object->trace_handle = set_track_prepare();
 
-	raw_spin_lock_irqsave(&kmemleak_lock, flags);
+	return object;
+}
+
+static void __link_object(struct kmemleak_object *object, unsigned long ptr,
+			  size_t size, int min_count, bool is_phys)
+{
+
+	struct kmemleak_object *parent;
+	struct rb_node **link, *rb_parent;
+	unsigned long untagged_ptr;
+	unsigned long untagged_objp;
+
+	object->flags = OBJECT_ALLOCATED | (is_phys ? OBJECT_PHYS : 0);
+	object->pointer = ptr;
+	object->size = kfence_ksize((void *)ptr) ?: size;
+	object->min_count = min_count;
+	object->jiffies = jiffies;
 
 	untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
 	/*
@@ -711,14 +712,32 @@ static void __create_object(unsigned long ptr, size_t size,
 			 */
 			dump_object_info(parent);
 			kmem_cache_free(object_cache, object);
-			goto out;
+			return;
 		}
 	}
 	rb_link_node(&object->rb_node, rb_parent, link);
 	rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
 					  &object_tree_root);
 	list_add_tail_rcu(&object->object_list, &object_list);
-out:
+}
+
+/*
+ * Create the metadata (struct kmemleak_object) corresponding to an allocated
+ * memory block and add it to the object_list and object_tree_root (or
+ * object_phys_tree_root).
+ */
+static void __create_object(unsigned long ptr, size_t size,
+				int min_count, gfp_t gfp, bool is_phys)
+{
+	struct kmemleak_object *object;
+	unsigned long flags;
+
+	object = __alloc_object(gfp);
+	if (!object)
+		return;
+
+	raw_spin_lock_irqsave(&kmemleak_lock, flags);
+	__link_object(object, ptr, size, min_count, is_phys);
 	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
 }
 
-- 
2.25.1

Thanks for this, it looks better.

On Wed, Oct 18, 2023 at 06:29:49PM +0800, Liu Shixin wrote:
> -/*
> - * Create the metadata (struct kmemleak_object) corresponding to an allocated
> - * memory block and add it to the object_list and object_tree_root (or
> - * object_phys_tree_root).
> - */
> -static void __create_object(unsigned long ptr, size_t size,
> -			    int min_count, gfp_t gfp, bool is_phys)
> +static struct kmemleak_object * __alloc_object(gfp_t gfp)
>  {
> -	unsigned long flags;
> -	struct kmemleak_object *object, *parent;
> -	struct rb_node **link, *rb_parent;
> -	unsigned long untagged_ptr;
> -	unsigned long untagged_objp;
> +	struct kmemleak_object *object;
>  
>  	object = mem_pool_alloc(gfp);
>  	if (!object) {
>  		pr_warn("Cannot allocate a kmemleak_object structure\n");
>  		kmemleak_disable();
> -		return;
> +		return NULL;
>  	}
>  
>  	INIT_LIST_HEAD(&object->object_list);
> @@ -649,13 +639,8 @@ static void __create_object(unsigned long ptr, size_t size,
>  	INIT_HLIST_HEAD(&object->area_list);
>  	raw_spin_lock_init(&object->lock);
>  	atomic_set(&object->use_count, 1);
> -	object->flags = OBJECT_ALLOCATED | (is_phys ? OBJECT_PHYS : 0);
> -	object->pointer = ptr;
> -	object->size = kfence_ksize((void *)ptr) ?: size;
>  	object->excess_ref = 0;
> -	object->min_count = min_count;
>  	object->count = 0;			/* white color initially */
> -	object->jiffies = jiffies;
>  	object->checksum = 0;
>  	object->del_state = 0;

I'd keep all the initialisation in one place even if it means passing
more arguments to __alloc_object(). It feels a bit weird and error prone
to split the initialisation in two places. Otherwise I'm fine with the
split.

-- 
Catalin