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

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 lib/ref_tracker.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index cf5609b1ca79361763abe5a3a98484a3ee591ff2..c96994134fe1ddfcbf644cc75b36b7e94461ec48 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
 
+static struct dentry *ref_tracker_debug_dir;
+
 struct ref_tracker {
 	struct list_head	head;   /* anchor into dir->list or dir->quarantine */
 	bool			dead;
@@ -273,3 +275,19 @@ 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)) {
+		pr_warn("ref_tracker: unable to create debugfs ref_tracker directory: %pe\n",
+			ref_tracker_debug_dir);
+		ref_tracker_debug_dir = NULL;
+	}
+	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)) {

I'm pretty sure GregKH will tell you not to check the return
code. Nothing bad should happen. Yes, it takes a while to get used to
this, but that is the way debugfs is designed.

> +		pr_warn("ref_tracker: unable to create debugfs ref_tracker directory: %pe\n",
> +			ref_tracker_debug_dir);
> +		ref_tracker_debug_dir = NULL;

No need for this. All debugfs_ functions are happy to accept an err
pointer and do a NOP.

	Andrew