Add a new "ref_tracker" directory in debugfs. Each individual refcount
tracker can add a directory or files under there to display info about
currently-held references.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 include/linux/ref_tracker.h |  3 +++
 lib/ref_tracker.c           | 15 +++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index 8eac4f3d52547ccbaf9dcd09962ce80d26fbdff8..16fb6ec0cc7adc24457cfab13ee3994d85c15b39 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -22,6 +22,9 @@ struct ref_tracker_dir {
 };
 
 #ifdef CONFIG_REF_TRACKER
+#ifdef CONFIG_DEBUG_FS
+extern struct dentry *ref_tracker_debug_dir;
+#endif /* CONFIG_DEBUG_FS */
 
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 					unsigned int quarantine_count,
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index cf5609b1ca79361763abe5a3a98484a3ee591ff2..136723eab6b17ae07132c659fd1d8b0690d8c2d9 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -12,6 +12,8 @@
 #define REF_TRACKER_STACK_ENTRIES 16
 #define STACK_BUF_SIZE 1024
 
+struct dentry *ref_tracker_debug_dir;
+
 struct ref_tracker {
 	struct list_head	head;   /* anchor into dir->list or dir->quarantine */
 	bool			dead;
@@ -273,3 +275,16 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ref_tracker_free);
+
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+
+static int __init ref_tracker_debug_init(void)
+{
+	ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL);
+	if (IS_ERR(ref_tracker_debug_dir))
+		return PTR_ERR(ref_tracker_debug_dir);
+	return 0;
+}
+late_initcall(ref_tracker_debug_init);
+#endif /* CONFIG_DEBUG_FS */

-- 
2.49.0

> +static int __init ref_tracker_debug_init(void)
> +{
> +	ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL);
> +	if (IS_ERR(ref_tracker_debug_dir))
> +		return PTR_ERR(ref_tracker_debug_dir);
> +	return 0;

With debugfs you are not supposed to check the return codes. It is
debug, it does not matter if it fails, same way it does not matter if
it is not even part of the kernel. If it does fail, operations which
add to the directory as safe, they will not opps because of a previous
failure.

	Andrew

From: Jeff Layton <jlayton@kernel.org>
Date: Tue, 08 Apr 2025 09:36:37 -0400
> Add a new "ref_tracker" directory in debugfs. Each individual refcount
> tracker can add a directory or files under there to display info about
> currently-held references.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>