From d04992dc86a6c77b7d39a1ee10013aed7111e855 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 18 Jun 2025 10:24:20 -0400 Subject: [PATCH] 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 Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-7-24fc37ead144@kernel.org Signed-off-by: Jakub Kicinski --- include/linux/ref_tracker.h | 11 ++++++++ lib/ref_tracker.c | 50 +++++++++++++++++++++++++++++++++++++ 2 files changed, 61 insertions(+) diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h index 28bbf436a8f46..e1323de93bf6b 100644 --- a/include/linux/ref_tracker.h +++ b/include/linux/ref_tracker.h @@ -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) { } diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c index c938ef56954b2..6608520d61186 100644 --- a/lib/ref_tracker.c +++ b/lib/ref_tracker.c @@ -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; } -- 2.47.2