Commit d04992dc authored by Jeff Layton's avatar Jeff Layton Committed by Jakub Kicinski
Browse files

ref_tracker: add a way to create a symlink to the ref_tracker_dir debugfs file 



Add the ability for a subsystem to add a user-friendly symlink that
points to a ref_tracker_dir's debugfs file. Add a separate
debugfs_symlinks xarray and use that to track symlinks. The reaper
workqueue job will remove symlinks before their corresponding dentries.

Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-7-24fc37ead144@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 65b584f5

include/linux/ref_tracker.h

+11 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ struct ref_tracker_dir { 
#ifdef CONFIG_DEBUG_FS



void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir);

void ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...);



#else /* CONFIG_DEBUG_FS */
@@ -36,6 +37,11 @@ static inline void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir) 
{

}



static inline __ostream_printf

void ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...)

{

}



#endif /* CONFIG_DEBUG_FS */



static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
@@ -85,6 +91,11 @@ static inline void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir) 
{

}



static inline __ostream_printf

void ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...)

{

}



static inline void ref_tracker_dir_exit(struct ref_tracker_dir *dir)

{

}

lib/ref_tracker.c

+50 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ struct ref_tracker_dir_stats { 
 * dentries asynchronously.

 */

static struct xarray		debugfs_dentries;

static struct xarray		debugfs_symlinks;

static struct work_struct	debugfs_reap_worker;



#define REF_TRACKER_DIR_DEAD	XA_MARK_0
@@ -55,6 +56,10 @@ static inline void ref_tracker_debugfs_mark(struct ref_tracker_dir *dir) 
	__xa_set_mark(&debugfs_dentries, (unsigned long)dir, REF_TRACKER_DIR_DEAD);

	xa_unlock_irqrestore(&debugfs_dentries, flags);



	xa_lock_irqsave(&debugfs_symlinks, flags);

	__xa_set_mark(&debugfs_symlinks, (unsigned long)dir, REF_TRACKER_DIR_DEAD);

	xa_unlock_irqrestore(&debugfs_symlinks, flags);



	schedule_work(&debugfs_reap_worker);

}

#else
@@ -451,6 +456,45 @@ void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir) 
}

EXPORT_SYMBOL(ref_tracker_dir_debugfs);



void __ostream_printf ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...)

{

	char name[NAME_MAX + 1];

	struct dentry *symlink, *dentry;

	va_list args;

	int ret;



	symlink = xa_load(&debugfs_symlinks, (unsigned long)dir);

	dentry = xa_load(&debugfs_dentries, (unsigned long)dir);



	/* Already created?*/

	if (symlink && !xa_is_err(symlink))

		return;



	if (!dentry || xa_is_err(dentry))

		return;



	va_start(args, fmt);

	ret = vsnprintf(name, sizeof(name), fmt, args);

	va_end(args);

	name[sizeof(name) - 1] = '\0';



	if (ret < sizeof(name)) {

		symlink = debugfs_create_symlink(name, ref_tracker_debug_dir,

						 dentry->d_name.name);

		if (!IS_ERR(symlink)) {

			void *old;



			old = xa_store_irq(&debugfs_symlinks, (unsigned long)dir,

					   symlink, GFP_KERNEL);

			if (xa_is_err(old))

				debugfs_remove(symlink);

			else

				WARN_ON_ONCE(old);

		}

	}

}

EXPORT_SYMBOL(ref_tracker_dir_symlink);



static void debugfs_reap_work(struct work_struct *work)

{

	struct dentry *dentry;
@@ -459,6 +503,11 @@ static void debugfs_reap_work(struct work_struct *work) 


	do {

		reaped = false;

		xa_for_each_marked(&debugfs_symlinks, index, dentry, REF_TRACKER_DIR_DEAD) {

			xa_erase_irq(&debugfs_symlinks, index);

			debugfs_remove(dentry);

			reaped = true;

		}

		xa_for_each_marked(&debugfs_dentries, index, dentry, REF_TRACKER_DIR_DEAD) {

			xa_erase_irq(&debugfs_dentries, index);

			debugfs_remove(dentry);
@@ -471,6 +520,7 @@ static int __init ref_tracker_debugfs_init(void) 
{

	INIT_WORK(&debugfs_reap_worker, debugfs_reap_work);

	xa_init_flags(&debugfs_dentries, XA_FLAGS_LOCK_IRQ);

	xa_init_flags(&debugfs_symlinks, XA_FLAGS_LOCK_IRQ);

	ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL);

	return 0;

}