On Wed, 30 Apr 2025, Jeff Layton <jlay...@kernel.org> wrote:
> Currently, there is no convenient way to see the info that the
> ref_tracking infrastructure collects. Attempt to create a file in
> debugfs when called from ref_tracker_dir_init().
>
> The file is given the name "class@%px", as having the unmodified address
> is helpful for debugging. This should be safe since this directory is only
> accessible by root
>
> If debugfs file creation fails, a pr_warn will be isssued.
>
> Signed-off-by: Jeff Layton <jlay...@kernel.org>
> ---
> include/linux/ref_tracker.h | 14 +++++++++
> lib/ref_tracker.c | 73
> +++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 85 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
> index
> 2adae128d4b5e45f156af4775a1d184bb596fa91..c6e65d7ef4d4fc74c60fcabd19166c131d4173e2
> 100644
> --- a/include/linux/ref_tracker.h
> +++ b/include/linux/ref_tracker.h
> @@ -5,6 +5,7 @@
> #include <linux/types.h>
> #include <linux/spinlock.h>
> #include <linux/stackdepot.h>
> +#include <linux/seq_file.h>
Nothing here requires seq_file.h as far as I can tell. Please avoid
superfluous header dependencies.
BR,
Jani.
>
> struct ref_tracker;
>
> @@ -18,12 +19,17 @@ struct ref_tracker_dir {
> struct list_head list; /* List of active trackers */
> struct list_head quarantine; /* List of dead trackers */
> const char *class; /* object classname */
> +#ifdef CONFIG_DEBUG_FS
> + struct dentry *dentry;
> +#endif
> char name[32];
> #endif
> };
>
> #ifdef CONFIG_REF_TRACKER
>
> +void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir);
> +
> static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
> unsigned int quarantine_count,
> const char *class,
> @@ -37,7 +43,11 @@ static inline void ref_tracker_dir_init(struct
> ref_tracker_dir *dir,
> refcount_set(&dir->untracked, 1);
> refcount_set(&dir->no_tracker, 1);
> dir->class = class;
> +#ifdef CONFIG_DEBUG_FS
> + dir->dentry = NULL;
> +#endif
> strscpy(dir->name, name, sizeof(dir->name));
> + ref_tracker_dir_debugfs(dir);
> stack_depot_init();
> }
>
> @@ -66,6 +76,10 @@ static inline void ref_tracker_dir_init(struct
> ref_tracker_dir *dir,
> {
> }
>
> +static inline void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir)
> +{
> +}
> +
> 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
> b69c11e83c18c19aaa2dc23f802291d4a7e82a66..3ee4fd0f33407881cfa140dcb7d8b40e3c2722de
> 100644
> --- a/lib/ref_tracker.c
> +++ b/lib/ref_tracker.c
> @@ -31,6 +31,14 @@ struct ref_tracker_dir_stats {
> } stacks[];
> };
>
> +#ifdef CONFIG_DEBUG_FS
> +static void ref_tracker_debugfs_remove(struct ref_tracker_dir *dir);
> +#else
> +static inline void ref_tracker_debugfs_remove(struct ref_tracker_dir *dir)
> +{
> +}
> +#endif
> +
> static struct ref_tracker_dir_stats *
> ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
> {
> @@ -197,6 +205,7 @@ void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
> bool leak = false;
>
> dir->dead = true;
> + ref_tracker_debugfs_remove(dir);
> spin_lock_irqsave(&dir->lock, flags);
> list_for_each_entry_safe(tracker, n, &dir->quarantine, head) {
> list_del(&tracker->head);
> @@ -313,8 +322,7 @@ EXPORT_SYMBOL_GPL(ref_tracker_free);
> #ifdef CONFIG_DEBUG_FS
> #include <linux/debugfs.h>
>
> -static __maybe_unused int
> -ref_tracker_dir_seq_print(struct ref_tracker_dir *dir, struct seq_file *seq)
> +static int ref_tracker_dir_seq_print(struct ref_tracker_dir *dir, struct
> seq_file *seq)
> {
> struct ostream os = { .func = pr_ostream_seq,
> .prefix = "",
> @@ -328,6 +336,67 @@ ref_tracker_dir_seq_print(struct ref_tracker_dir *dir,
> struct seq_file *seq)
> return os.used;
> }
>
> +static int ref_tracker_debugfs_show(struct seq_file *f, void *v)
> +{
> + struct ref_tracker_dir *dir = f->private;
> +
> + return ref_tracker_dir_seq_print(dir, f);
> +}
> +
> +static int ref_tracker_debugfs_open(struct inode *inode, struct file *filp)
> +{
> + struct ref_tracker_dir *dir = inode->i_private;
> +
> + return single_open(filp, ref_tracker_debugfs_show, dir);
> +}
> +
> +static const struct file_operations ref_tracker_debugfs_fops = {
> + .owner = THIS_MODULE,
> + .open = ref_tracker_debugfs_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +/**
> + * ref_tracker_dir_debugfs - create debugfs file for ref_tracker_dir
> + * @dir: ref_tracker_dir to be associated with debugfs file
> + *
> + * In most cases, a debugfs file will be created automatically for every
> + * ref_tracker_dir. If the object was created before debugfs is brought up
> + * then that may fail. In those cases, it is safe to call this at a later
> + * time to create the file.
> + */
> +void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir)
> +{
> + char name[NAME_MAX + 1];
> + int ret;
> +
> + /* No-op if already created */
> + if (!IS_ERR_OR_NULL(dir->dentry))
> + return;
> +
> + ret = snprintf(name, sizeof(name), "%s@%px", dir->class, dir);
> + name[sizeof(name) - 1] = '\0';
> +
> + if (ret < sizeof(name))
> + dir->dentry = debugfs_create_file(name, S_IFREG | 0400,
> + ref_tracker_debug_dir, dir,
> + &ref_tracker_debugfs_fops);
> + else
> + dir->dentry = ERR_PTR(-ENAMETOOLONG);
> +
> + if (IS_ERR(dir->dentry))
> + pr_warn("ref_tracker: unable to create debugfs file for %s:
> %pe\n",
> + name, dir->dentry);
> +}
> +EXPORT_SYMBOL(ref_tracker_dir_debugfs);
> +
> +static void ref_tracker_debugfs_remove(struct ref_tracker_dir *dir)
> +{
> + debugfs_remove(dir->dentry);
> +}
> +
> static int __init ref_tracker_debugfs_init(void)
> {
> ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL);
--
Jani Nikula, Intel
