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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: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-7-24fc37ead144@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jeff Layton 2025-06-18 10:24:20 -04:00 committed by Jakub Kicinski
parent 65b584f536
commit d04992dc86
2 changed files with 61 additions and 0 deletions
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11
include/linux/ref_tracker.h
View File

@ -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)
{
}

50
lib/ref_tracker.c
View File

@ -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;
}