[PATCH v10 0/9] ref_tracker: add ability to register a debugfs file for a ref_tracker_dir

[PATCH v10 0/9] ref_tracker: add ability to register a debugfs file for a ref_tracker_dir

[Jeff Layton]

Thought I had sent this a week or so ago, but I dropped the ball in the
midst of some travel.

The only difference from v9 is that this posting drops the i915 symlink
patch. I got a CI report [1] that showed some EEXIST errors when trying
to create those symlinks, which tells me that the names are not truly
unique. Since I don't know much about the i915 driver, I'll leave that
as an exercise for that team. It should be fairly simple to add if they
come up with a scheme that gives these object unique names.

[1]: https://patchwork.freedesktop.org/series/148490/

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
Changes in v10:
- drop the i915 symlink patch
- Link to v9: https://lore.kernel.org/r/20250509-reftrack-dbgfs-v9-0-8ab888a4524d@kernel.org

Changes in v9:
- fix typo in ref_tracker_dir_init() kerneldoc header
- Link to v8: https://lore.kernel.org/r/20250507-reftrack-dbgfs-v8-0-607717d3bb98@kernel.org

Changes in v8:
- fix up compiler warnings that the KTR warned about
- ensure builds with CONFIG_DEBUG_FS=n and CONFIG_REF_TRACKER=y work
- Link to v7: https://lore.kernel.org/r/20250505-reftrack-dbgfs-v7-0-f78c5d97bcca@kernel.org

Changes in v7:
- include net->net_cookie in netns symlink name
- add __ostream_printf to ref_tracker_dir_symlink() stub function
- remove unneeded #include of seq_file.h
- Link to v6: https://lore.kernel.org/r/20250430-reftrack-dbgfs-v6-0-867c29aff03a@kernel.org

Changes in v6:
- clean up kerneldoc comment for ref_tracker_dir_debugfs()
- add missing stub function for ref_tracker_dir_symlink()
- temporary __maybe_unused on ref_tracker_dir_seq_print() to silence compiler warning
- Link to v5: https://lore.kernel.org/r/20250428-reftrack-dbgfs-v5-0-1cbbdf2038bd@kernel.org

Changes in v5:
- add class string to each ref_tracker_dir
- auto-register debugfs file for every tracker in ref_tracker_dir_init
- add function to allow adding a symlink for each tracker
- add patches to create symlinks for netns's and i915 entries
- change output format to print class@%p instead of name@%p
- eliminate the name field in ref_tracker_dir
- fix off-by-one bug when NULL terminating name string
- Link to v4: https://lore.kernel.org/r/20250418-reftrack-dbgfs-v4-0-5ca5c7899544@kernel.org

Changes in v4:
- Drop patch to widen ref_tracker_dir_.name, use NAME_MAX+1 (256) instead since this only affects dentry name
- Link to v3: https://lore.kernel.org/r/20250417-reftrack-dbgfs-v3-0-c3159428c8fb@kernel.org

Changes in v3:
- don't overwrite dir->name in ref_tracker_dir_debugfs
- define REF_TRACKER_NAMESZ and use it when setting name
- Link to v2: https://lore.kernel.org/r/20250415-reftrack-dbgfs-v2-0-b18c4abd122f@kernel.org

Changes in v2:
- Add patch to do %pK -> %p conversion in ref_tracker.c
- Pass in output function to pr_ostream() instead of if statement
- Widen ref_tracker_dir.name to 64 bytes to accomodate unique names
- Eliminate error handling with debugfs manipulation
- Incorporate pointer value into netdev name
- Link to v1: https://lore.kernel.org/r/20250414-reftrack-dbgfs-v1-0-f03585832203@kernel.org

---
Jeff Layton (9):
      ref_tracker: don't use %pK in pr_ostream() output
      ref_tracker: add a top level debugfs directory for ref_tracker
      ref_tracker: have callers pass output function to pr_ostream()
      ref_tracker: add a static classname string to each ref_tracker_dir
      ref_tracker: allow pr_ostream() to print directly to a seq_file
      ref_tracker: automatically register a file in debugfs for a ref_tracker_dir
      ref_tracker: add a way to create a symlink to the ref_tracker_dir debugfs file
      net: add symlinks to ref_tracker_dir for netns
      ref_tracker: eliminate the ref_tracker_dir name field

 drivers/gpu/drm/display/drm_dp_tunnel.c |   2 +-
 drivers/gpu/drm/i915/intel_runtime_pm.c |   3 +-
 drivers/gpu/drm/i915/intel_wakeref.c    |   2 +-
 include/linux/ref_tracker.h             |  58 +++++++++-
 lib/ref_tracker.c                       | 190 +++++++++++++++++++++++++++++---
 net/core/dev.c                          |   2 +-
 net/core/net_namespace.c                |  34 +++++-
 7 files changed, 265 insertions(+), 26 deletions(-)
---
base-commit: fefff2755f2aa4125dce2a1edfe7e545c7c621f2
change-id: 20250413-reftrack-dbgfs-3767b303e2fa

Best regards,
-- 
Jeff Layton <jlayton@kernel.org>

[PATCH v10 1/9] ref_tracker: don't use %pK in pr_ostream() output

[Jeff Layton]

As Thomas Weißschuh points out [1], it is now preferable to use %p
instead of hashed pointers with printk(), since raw pointers should no
longer be leaked into the kernel log. Change the ref_tracker
infrastructure to use %p instead of %pK in its formats.

[1]: https://lore.kernel.org/netdev/20250414-restricted-pointers-net-v1-0-12af0ce46cdd@linutronix.de/

Cc: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 lib/ref_tracker.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index cf5609b1ca79361763abe5a3a98484a3ee591ff2..de71439e12a3bab6456910986fa611dfbdd97980 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -96,7 +96,7 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 
 	stats = ref_tracker_get_stats(dir, display_limit);
 	if (IS_ERR(stats)) {
-		pr_ostream(s, "%s@%pK: couldn't get stats, error %pe\n",
+		pr_ostream(s, "%s@%p: couldn't get stats, error %pe\n",
 			   dir->name, dir, stats);
 		return;
 	}
@@ -107,13 +107,13 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 		stack = stats->stacks[i].stack_handle;
 		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
 			sbuf[0] = 0;
-		pr_ostream(s, "%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
+		pr_ostream(s, "%s@%p has %d/%d users at\n%s\n", dir->name, dir,
 			   stats->stacks[i].count, stats->total, sbuf);
 		skipped -= stats->stacks[i].count;
 	}
 
 	if (skipped)
-		pr_ostream(s, "%s@%pK skipped reports about %d/%d users.\n",
+		pr_ostream(s, "%s@%p skipped reports about %d/%d users.\n",
 			   dir->name, dir, skipped, stats->total);
 
 	kfree(sbuf);

-- 
2.49.0

[PATCH v10 2/9] ref_tracker: add a top level debugfs directory for ref_tracker

[Jeff Layton]

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

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 lib/ref_tracker.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index de71439e12a3bab6456910986fa611dfbdd97980..34ac37db209077d6771d5f4367e53d19ba3169c6 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -273,3 +273,19 @@ 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 struct dentry *ref_tracker_debug_dir = (struct dentry *)-ENOENT;
+
+static int __init ref_tracker_debugfs_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);
+	return 0;
+}
+late_initcall(ref_tracker_debugfs_init);
+#endif /* CONFIG_DEBUG_FS */

-- 
2.49.0

[PATCH v10 3/9] ref_tracker: have callers pass output function to pr_ostream()

[Jeff Layton]

In a later patch, we'll be adding a 3rd mechanism for outputting
ref_tracker info via seq_file. Instead of a conditional, have the caller
set a pointer to an output function in struct ostream. As part of this,
the log prefix must be explicitly passed in, as it's too late for the
pr_fmt macro.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 include/linux/ref_tracker.h |  2 ++
 lib/ref_tracker.c           | 51 ++++++++++++++++++++++++++++++++-------------
 2 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index 8eac4f3d52547ccbaf9dcd09962ce80d26fbdff8..a0a1ee43724ffa00e60c116be18e481bfe1d1455 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -6,6 +6,8 @@
 #include <linux/spinlock.h>
 #include <linux/stackdepot.h>
 
+#define __ostream_printf __printf(2, 3)
+
 struct ref_tracker;
 
 struct ref_tracker_dir {
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index 34ac37db209077d6771d5f4367e53d19ba3169c6..607718d00ffa74bd6d9abf97e913abcfd56dd1c8 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -63,21 +63,37 @@ ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
 }
 
 struct ostream {
+	void __ostream_printf (*func)(struct ostream *stream, char *fmt, ...);
+	char *prefix;
 	char *buf;
 	int size, used;
 };
 
+static void __ostream_printf pr_ostream_log(struct ostream *stream, char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	vprintk(fmt, args);
+	va_end(args);
+}
+
+static void __ostream_printf pr_ostream_buf(struct ostream *stream, char *fmt, ...)
+{
+	int ret, len = stream->size - stream->used;
+	va_list args;
+
+	va_start(args, fmt);
+	ret = vsnprintf(stream->buf + stream->used, len, fmt, args);
+	va_end(args);
+	stream->used += min(ret, len);
+}
+
 #define pr_ostream(stream, fmt, args...) \
 ({ \
 	struct ostream *_s = (stream); \
 \
-	if (!_s->buf) { \
-		pr_err(fmt, ##args); \
-	} else { \
-		int ret, len = _s->size - _s->used; \
-		ret = snprintf(_s->buf + _s->used, len, pr_fmt(fmt), ##args); \
-		_s->used += min(ret, len); \
-	} \
+	_s->func(_s, fmt, ##args); \
 })
 
 static void
@@ -96,8 +112,8 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 
 	stats = ref_tracker_get_stats(dir, display_limit);
 	if (IS_ERR(stats)) {
-		pr_ostream(s, "%s@%p: couldn't get stats, error %pe\n",
-			   dir->name, dir, stats);
+		pr_ostream(s, "%s%s@%p: couldn't get stats, error %pe\n",
+			   s->prefix, dir->name, dir, stats);
 		return;
 	}
 
@@ -107,14 +123,15 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 		stack = stats->stacks[i].stack_handle;
 		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
 			sbuf[0] = 0;
-		pr_ostream(s, "%s@%p has %d/%d users at\n%s\n", dir->name, dir,
-			   stats->stacks[i].count, stats->total, sbuf);
+		pr_ostream(s, "%s%s@%p has %d/%d users at\n%s\n", s->prefix,
+			   dir->name, dir, stats->stacks[i].count,
+			   stats->total, sbuf);
 		skipped -= stats->stacks[i].count;
 	}
 
 	if (skipped)
-		pr_ostream(s, "%s@%p skipped reports about %d/%d users.\n",
-			   dir->name, dir, skipped, stats->total);
+		pr_ostream(s, "%s%s@%p skipped reports about %d/%d users.\n",
+			   s->prefix, dir->name, dir, skipped, stats->total);
 
 	kfree(sbuf);
 
@@ -124,7 +141,8 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 void ref_tracker_dir_print_locked(struct ref_tracker_dir *dir,
 				  unsigned int display_limit)
 {
-	struct ostream os = {};
+	struct ostream os = { .func = pr_ostream_log,
+			      .prefix = "ref_tracker: " };
 
 	__ref_tracker_dir_pr_ostream(dir, display_limit, &os);
 }
@@ -143,7 +161,10 @@ EXPORT_SYMBOL(ref_tracker_dir_print);
 
 int ref_tracker_dir_snprint(struct ref_tracker_dir *dir, char *buf, size_t size)
 {
-	struct ostream os = { .buf = buf, .size = size };
+	struct ostream os = { .func = pr_ostream_buf,
+			      .prefix = "ref_tracker: ",
+			      .buf = buf,
+			      .size = size };
 	unsigned long flags;
 
 	spin_lock_irqsave(&dir->lock, flags);

-- 
2.49.0

[PATCH v10 4/9] ref_tracker: add a static classname string to each ref_tracker_dir

[Jeff Layton]

A later patch in the series will be adding debugfs files for each
ref_tracker that get created in ref_tracker_dir_init(). The format will
be "class@%px". The current "name" string can vary between
ref_tracker_dir objects of the same type, so it's not suitable for this
purpose.

Add a new "class" string to the ref_tracker dir that describes the
the type of object (sans any individual info for that object).

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 drivers/gpu/drm/display/drm_dp_tunnel.c | 2 +-
 drivers/gpu/drm/i915/intel_runtime_pm.c | 3 ++-
 drivers/gpu/drm/i915/intel_wakeref.c    | 2 +-
 include/linux/ref_tracker.h             | 4 ++++
 lib/test_ref_tracker.c                  | 2 +-
 net/core/dev.c                          | 2 +-
 net/core/net_namespace.c                | 4 ++--
 7 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_tunnel.c b/drivers/gpu/drm/display/drm_dp_tunnel.c
index 076edf1610480275c62395334ab0536befa42f15..b9c12b8bf2a3e400b6d8e9d184145834c603b9e1 100644
--- a/drivers/gpu/drm/display/drm_dp_tunnel.c
+++ b/drivers/gpu/drm/display/drm_dp_tunnel.c
@@ -1920,7 +1920,7 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
 	}
 
 #ifdef CONFIG_DRM_DISPLAY_DP_TUNNEL_STATE_DEBUG
-	ref_tracker_dir_init(&mgr->ref_tracker, 16, "dptun");
+	ref_tracker_dir_init(&mgr->ref_tracker, 16, "drm_dptun", "dptun");
 #endif
 
 	for (i = 0; i < max_group_count; i++) {
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 8d9f4c410546e4144d4bc8bbc6696f3bd9498848..3fdab3b44c08cea16ac2f73aafc2bea2ffbb19e7 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -59,7 +59,8 @@ static struct drm_i915_private *rpm_to_i915(struct intel_runtime_pm *rpm)
 
 static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
 {
-	ref_tracker_dir_init(&rpm->debug, INTEL_REFTRACK_DEAD_COUNT, dev_name(rpm->kdev));
+	ref_tracker_dir_init(&rpm->debug, INTEL_REFTRACK_DEAD_COUNT,
+			     "intel_runtime_pm", dev_name(rpm->kdev));
 }
 
 static intel_wakeref_t
diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
index 07e81be4d3920febece34709c63a63204a41583c..5269e64c58a49884f5d712557546272bfdeb8417 100644
--- a/drivers/gpu/drm/i915/intel_wakeref.c
+++ b/drivers/gpu/drm/i915/intel_wakeref.c
@@ -114,7 +114,7 @@ void __intel_wakeref_init(struct intel_wakeref *wf,
 			 "wakeref.work", &key->work, 0);
 
 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_WAKEREF)
-	ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, name);
+	ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, "intel_wakeref", name);
 #endif
 }
 
diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index a0a1ee43724ffa00e60c116be18e481bfe1d1455..3968f993db81e95c0d58c81454311841c1b9cd35 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -19,6 +19,7 @@ struct ref_tracker_dir {
 	bool			dead;
 	struct list_head	list; /* List of active trackers */
 	struct list_head	quarantine; /* List of dead trackers */
+	const char		*class; /* object classname */
 	char			name[32];
 #endif
 };
@@ -27,6 +28,7 @@ struct ref_tracker_dir {
 
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 					unsigned int quarantine_count,
+					const char *class,
 					const char *name)
 {
 	INIT_LIST_HEAD(&dir->list);
@@ -36,6 +38,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 	dir->dead = false;
 	refcount_set(&dir->untracked, 1);
 	refcount_set(&dir->no_tracker, 1);
+	dir->class = class;
 	strscpy(dir->name, name, sizeof(dir->name));
 	stack_depot_init();
 }
@@ -60,6 +63,7 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
 
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 					unsigned int quarantine_count,
+					const char *class,
 					const char *name)
 {
 }
diff --git a/lib/test_ref_tracker.c b/lib/test_ref_tracker.c
index b983ceb12afcb84ad60360a1e6fec0072e78ef79..d263502a4c1db248f64a66a468e96c8e4cffab25 100644
--- a/lib/test_ref_tracker.c
+++ b/lib/test_ref_tracker.c
@@ -64,7 +64,7 @@ static int __init test_ref_tracker_init(void)
 {
 	int i;
 
-	ref_tracker_dir_init(&ref_dir, 100, "selftest");
+	ref_tracker_dir_init(&ref_dir, 100, "selftest", "selftest");
 
 	timer_setup(&test_ref_tracker_timer, test_ref_tracker_timer_func, 0);
 	mod_timer(&test_ref_tracker_timer, jiffies + 1);
diff --git a/net/core/dev.c b/net/core/dev.c
index 3eb4e945f3120f26605a0b407cb98b12492bc61e..bac9d29486556023cd99f5101b96b052acb9ba70 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11713,7 +11713,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 
 	dev->priv_len = sizeof_priv;
 
-	ref_tracker_dir_init(&dev->refcnt_tracker, 128, name);
+	ref_tracker_dir_init(&dev->refcnt_tracker, 128, "netdev", name);
 #ifdef CONFIG_PCPU_DEV_REFCNT
 	dev->pcpu_refcnt = alloc_percpu(int);
 	if (!dev->pcpu_refcnt)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 42ee7fce3d95b5a2756d6a3780edba070f01ddb6..8708eb975295ffb78de35fcf4abef7cc281f5a51 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -403,8 +403,8 @@ static __net_init void preinit_net(struct net *net, struct user_namespace *user_
 {
 	refcount_set(&net->passive, 1);
 	refcount_set(&net->ns.count, 1);
-	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net refcnt");
-	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net notrefcnt");
+	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt", "net_refcnt");
+	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt", "net_notrefcnt");
 
 	get_random_bytes(&net->hash_mix, sizeof(u32));
 	net->dev_base_seq = 1;

-- 
2.49.0

[PATCH v10 5/9] ref_tracker: allow pr_ostream() to print directly to a seq_file

[Jeff Layton]

Allow pr_ostream to also output directly to a seq_file without an
intermediate buffer. The first caller of +ref_tracker_dir_seq_print()
will come in a later patch, so mark that __maybe_unused for now. That
designation will be removed once it is used.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 lib/ref_tracker.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index 607718d00ffa74bd6d9abf97e913abcfd56dd1c8..6e85e7eb347d86775ba38a72dad7159f9ac41ed9 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -8,6 +8,7 @@
 #include <linux/slab.h>
 #include <linux/stacktrace.h>
 #include <linux/stackdepot.h>
+#include <linux/seq_file.h>
 
 #define REF_TRACKER_STACK_ENTRIES 16
 #define STACK_BUF_SIZE 1024
@@ -66,6 +67,7 @@ struct ostream {
 	void __ostream_printf (*func)(struct ostream *stream, char *fmt, ...);
 	char *prefix;
 	char *buf;
+	struct seq_file *seq;
 	int size, used;
 };
 
@@ -300,6 +302,30 @@ EXPORT_SYMBOL_GPL(ref_tracker_free);
 
 static struct dentry *ref_tracker_debug_dir = (struct dentry *)-ENOENT;
 
+static void __ostream_printf pr_ostream_seq(struct ostream *stream, char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	seq_vprintf(stream->seq, fmt, args);
+	va_end(args);
+}
+
+static __maybe_unused int
+ref_tracker_dir_seq_print(struct ref_tracker_dir *dir, struct seq_file *seq)
+{
+	struct ostream os = { .func = pr_ostream_seq,
+			      .prefix = "",
+			      .seq = seq };
+	unsigned long flags;
+
+	spin_lock_irqsave(&dir->lock, flags);
+	__ref_tracker_dir_pr_ostream(dir, 16, &os);
+	spin_unlock_irqrestore(&dir->lock, flags);
+
+	return os.used;
+}
+
 static int __init ref_tracker_debugfs_init(void)
 {
 	ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL);

-- 
2.49.0

[PATCH v10 6/9] ref_tracker: automatically register a file in debugfs for a ref_tracker_dir

[Jeff Layton]

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 <jlayton@kernel.org>
---
 include/linux/ref_tracker.h | 23 ++++++++++++++
 lib/ref_tracker.c           | 73 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 94 insertions(+), 2 deletions(-)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index 3968f993db81e95c0d58c81454311841c1b9cd35..dd289fdda12b1a10197912f5796f97002e785aaf 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -20,12 +20,27 @@ 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
 
+#ifdef CONFIG_DEBUG_FS
+
+void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir);
+
+#else /* CONFIG_DEBUG_FS */
+
+static inline void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir)
+{
+}
+
+#endif /* CONFIG_DEBUG_FS */
+
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 					unsigned int quarantine_count,
 					const char *class,
@@ -39,7 +54,11 @@ 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();
 }
 
@@ -68,6 +87,10 @@ 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 6e85e7eb347d86775ba38a72dad7159f9ac41ed9..1df12625d80cc7cff65d9f6be89e1dd5c5ffb7f6 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -29,6 +29,14 @@ 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)
 {
@@ -184,6 +192,7 @@ 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);
@@ -311,8 +320,7 @@ static void __ostream_printf pr_ostream_seq(struct ostream *stream, char *fmt, .
 	va_end(args);
 }
 
-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 = "",
@@ -326,6 +334,67 @@ 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);

-- 
2.49.0

[PATCH v10 7/9] ref_tracker: add a way to create a symlink to the ref_tracker_dir debugfs file

[Jeff Layton]

Add the ability for a subsystem to add a user-friendly symlink that
points to a ref_tracker_dir's debugfs file.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 include/linux/ref_tracker.h | 13 +++++++++++++
 lib/ref_tracker.c           | 28 ++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index dd289fdda12b1a10197912f5796f97002e785aaf..ddc5a7b2bd84692bbc1e1ae67674ec2c6857e1ec 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -22,6 +22,7 @@ struct ref_tracker_dir {
 	const char		*class; /* object classname */
 #ifdef CONFIG_DEBUG_FS
 	struct dentry		*dentry;
+	struct dentry		*symlink;
 #endif
 	char			name[32];
 #endif
@@ -32,6 +33,7 @@ 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 */
 
@@ -39,6 +41,11 @@ 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,
@@ -56,6 +63,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 	dir->class = class;
 #ifdef CONFIG_DEBUG_FS
 	dir->dentry = NULL;
+	dir->symlink = NULL;
 #endif
 	strscpy(dir->name, name, sizeof(dir->name));
 	ref_tracker_dir_debugfs(dir);
@@ -91,6 +99,11 @@ 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 1df12625d80cc7cff65d9f6be89e1dd5c5ffb7f6..5e84e5fd78e147a036d4adb511e657da07866a55 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -390,8 +390,36 @@ 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];
+	va_list args;
+	int ret;
+
+	/* Already created, or dentry doesn't exist? Do nothing */
+	if (!IS_ERR_OR_NULL(dir->symlink) || IS_ERR_OR_NULL(dir->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))
+		dir->symlink = debugfs_create_symlink(name, ref_tracker_debug_dir,
+						      dir->dentry->d_name.name);
+	else
+		dir->symlink = ERR_PTR(-ENAMETOOLONG);
+
+	if (IS_ERR(dir->symlink))
+		pr_warn("ref_tracker: unable to create debugfs symlink for %s: %pe\n",
+			name, dir->symlink);
+}
+EXPORT_SYMBOL(ref_tracker_dir_symlink);
+
 static void ref_tracker_debugfs_remove(struct ref_tracker_dir *dir)
 {
+	debugfs_remove(dir->symlink);
 	debugfs_remove(dir->dentry);
 }
 

-- 
2.49.0

[PATCH v10 8/9] net: add symlinks to ref_tracker_dir for netns

[Jeff Layton]

After assigning the inode number to the namespace, use it to create a
unique name for each netns refcount tracker with the ns.inum and
net_cookie values in it, and register a symlink to the debugfs file for
it.

init_net is registered before the ref_tracker dir is created, so add a
late_initcall() to register its files and symlinks.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 net/core/net_namespace.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 8708eb975295ffb78de35fcf4abef7cc281f5a51..39b01af90d240df48827e5c3159c3e2253e0a44d 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -791,12 +791,40 @@ struct net *get_net_ns_by_pid(pid_t pid)
 }
 EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
 
+#ifdef CONFIG_NET_NS_REFCNT_TRACKER
+static void net_ns_net_debugfs(struct net *net)
+{
+	ref_tracker_dir_symlink(&net->refcnt_tracker, "netns--%lx-%u-refcnt",
+				net->net_cookie, net->ns.inum);
+	ref_tracker_dir_symlink(&net->notrefcnt_tracker, "netns-%lx-%u-notrefcnt",
+				net->net_cookie, net->ns.inum);
+}
+
+static int __init init_net_debugfs(void)
+{
+	ref_tracker_dir_debugfs(&init_net.refcnt_tracker);
+	ref_tracker_dir_debugfs(&init_net.notrefcnt_tracker);
+	net_ns_net_debugfs(&init_net);
+	return 0;
+}
+late_initcall(init_net_debugfs);
+#else
+static void net_ns_net_debugfs(struct net *net)
+{
+}
+#endif
+
 static __net_init int net_ns_net_init(struct net *net)
 {
+	int ret;
+
 #ifdef CONFIG_NET_NS
 	net->ns.ops = &netns_operations;
 #endif
-	return ns_alloc_inum(&net->ns);
+	ret = ns_alloc_inum(&net->ns);
+	if (!ret)
+		net_ns_net_debugfs(net);
+	return ret;
 }
 
 static __net_exit void net_ns_net_exit(struct net *net)

-- 
2.49.0

[PATCH v10 9/9] ref_tracker: eliminate the ref_tracker_dir name field

[Jeff Layton]

Now that we have dentries and the ability to create meaningful symlinks
to them, don't keep a name string in each tracker. Switch the output
format to print "class@address", and drop the name field.

Also, add a kerneldoc header for ref_tracker_dir_init().

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 drivers/gpu/drm/display/drm_dp_tunnel.c |  2 +-
 drivers/gpu/drm/i915/intel_runtime_pm.c |  2 +-
 drivers/gpu/drm/i915/intel_wakeref.c    |  2 +-
 include/linux/ref_tracker.h             | 20 ++++++++++++++------
 lib/ref_tracker.c                       |  6 +++---
 lib/test_ref_tracker.c                  |  2 +-
 net/core/dev.c                          |  2 +-
 net/core/net_namespace.c                |  4 ++--
 8 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_tunnel.c b/drivers/gpu/drm/display/drm_dp_tunnel.c
index b9c12b8bf2a3e400b6d8e9d184145834c603b9e1..1205a4432eb4142344fb6eed1cb5ba5b21ec6953 100644
--- a/drivers/gpu/drm/display/drm_dp_tunnel.c
+++ b/drivers/gpu/drm/display/drm_dp_tunnel.c
@@ -1920,7 +1920,7 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
 	}
 
 #ifdef CONFIG_DRM_DISPLAY_DP_TUNNEL_STATE_DEBUG
-	ref_tracker_dir_init(&mgr->ref_tracker, 16, "drm_dptun", "dptun");
+	ref_tracker_dir_init(&mgr->ref_tracker, 16, "drm_dptun");
 #endif
 
 	for (i = 0; i < max_group_count; i++) {
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 3fdab3b44c08cea16ac2f73aafc2bea2ffbb19e7..c12b5d0e16fa363f3caede372e7a2031676aa7b5 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -60,7 +60,7 @@ static struct drm_i915_private *rpm_to_i915(struct intel_runtime_pm *rpm)
 static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
 {
 	ref_tracker_dir_init(&rpm->debug, INTEL_REFTRACK_DEAD_COUNT,
-			     "intel_runtime_pm", dev_name(rpm->kdev));
+			     "intel_runtime_pm");
 }
 
 static intel_wakeref_t
diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
index 5269e64c58a49884f5d712557546272bfdeb8417..615fb77809291be34d94600fdd4d919461a22720 100644
--- a/drivers/gpu/drm/i915/intel_wakeref.c
+++ b/drivers/gpu/drm/i915/intel_wakeref.c
@@ -114,7 +114,7 @@ void __intel_wakeref_init(struct intel_wakeref *wf,
 			 "wakeref.work", &key->work, 0);
 
 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_WAKEREF)
-	ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, "intel_wakeref", name);
+	ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, "intel_wakeref");
 #endif
 }
 
diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index ddc5a7b2bd84692bbc1e1ae67674ec2c6857e1ec..5878e7fce712930700054033ff5f21547e75224f 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -24,7 +24,6 @@ struct ref_tracker_dir {
 	struct dentry		*dentry;
 	struct dentry		*symlink;
 #endif
-	char			name[32];
 #endif
 };
 
@@ -48,10 +47,21 @@ void ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...)
 
 #endif /* CONFIG_DEBUG_FS */
 
+/**
+ * ref_tracker_dir_init - initialize a ref_tracker dir
+ * @dir: ref_tracker_dir to be initialized
+ * @quarantine_count: max number of entries to be tracked
+ * @class: pointer to static string that describes object type
+ *
+ * Initialize a ref_tracker_dir. If debugfs is configured, then a file
+ * will also be created for it under the top-level ref_tracker debugfs
+ * directory.
+ *
+ * Note that @class must point to a static string.
+ */
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 					unsigned int quarantine_count,
-					const char *class,
-					const char *name)
+					const char *class)
 {
 	INIT_LIST_HEAD(&dir->list);
 	INIT_LIST_HEAD(&dir->quarantine);
@@ -65,7 +75,6 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 	dir->dentry = NULL;
 	dir->symlink = NULL;
 #endif
-	strscpy(dir->name, name, sizeof(dir->name));
 	ref_tracker_dir_debugfs(dir);
 	stack_depot_init();
 }
@@ -90,8 +99,7 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
 
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 					unsigned int quarantine_count,
-					const char *class,
-					const char *name)
+					const char *class)
 {
 }
 
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index 5e84e5fd78e147a036d4adb511e657da07866a55..5fb384dd919e1f1ad632eaf595b954118bcfddab 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -123,7 +123,7 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 	stats = ref_tracker_get_stats(dir, display_limit);
 	if (IS_ERR(stats)) {
 		pr_ostream(s, "%s%s@%p: couldn't get stats, error %pe\n",
-			   s->prefix, dir->name, dir, stats);
+			   s->prefix, dir->class, dir, stats);
 		return;
 	}
 
@@ -134,14 +134,14 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
 			sbuf[0] = 0;
 		pr_ostream(s, "%s%s@%p has %d/%d users at\n%s\n", s->prefix,
-			   dir->name, dir, stats->stacks[i].count,
+			   dir->class, dir, stats->stacks[i].count,
 			   stats->total, sbuf);
 		skipped -= stats->stacks[i].count;
 	}
 
 	if (skipped)
 		pr_ostream(s, "%s%s@%p skipped reports about %d/%d users.\n",
-			   s->prefix, dir->name, dir, skipped, stats->total);
+			   s->prefix, dir->class, dir, skipped, stats->total);
 
 	kfree(sbuf);
 
diff --git a/lib/test_ref_tracker.c b/lib/test_ref_tracker.c
index d263502a4c1db248f64a66a468e96c8e4cffab25..b983ceb12afcb84ad60360a1e6fec0072e78ef79 100644
--- a/lib/test_ref_tracker.c
+++ b/lib/test_ref_tracker.c
@@ -64,7 +64,7 @@ static int __init test_ref_tracker_init(void)
 {
 	int i;
 
-	ref_tracker_dir_init(&ref_dir, 100, "selftest", "selftest");
+	ref_tracker_dir_init(&ref_dir, 100, "selftest");
 
 	timer_setup(&test_ref_tracker_timer, test_ref_tracker_timer_func, 0);
 	mod_timer(&test_ref_tracker_timer, jiffies + 1);
diff --git a/net/core/dev.c b/net/core/dev.c
index bac9d29486556023cd99f5101b96b052acb9ba70..a062912525ee573504a9cc252f71aed22693d24f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11713,7 +11713,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 
 	dev->priv_len = sizeof_priv;
 
-	ref_tracker_dir_init(&dev->refcnt_tracker, 128, "netdev", name);
+	ref_tracker_dir_init(&dev->refcnt_tracker, 128, "netdev");
 #ifdef CONFIG_PCPU_DEV_REFCNT
 	dev->pcpu_refcnt = alloc_percpu(int);
 	if (!dev->pcpu_refcnt)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 39b01af90d240df48827e5c3159c3e2253e0a44d..c03757e39c8a334d307fa1b5cc8f03ad3a8df0e0 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -403,8 +403,8 @@ static __net_init void preinit_net(struct net *net, struct user_namespace *user_
 {
 	refcount_set(&net->passive, 1);
 	refcount_set(&net->ns.count, 1);
-	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt", "net_refcnt");
-	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt", "net_notrefcnt");
+	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt");
+	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt");
 
 	get_random_bytes(&net->hash_mix, sizeof(u32));
 	net->dev_base_seq = 1;

-- 
2.49.0

Re: [PATCH v10 8/9] net: add symlinks to ref_tracker_dir for netns

[Eric Dumazet]

On Tue, May 27, 2025 at 4:34 AM Jeff Layton <jlayton@kernel.org> wrote:
>
> After assigning the inode number to the namespace, use it to create a
> unique name for each netns refcount tracker with the ns.inum and
> net_cookie values in it, and register a symlink to the debugfs file for
> it.
>
> init_net is registered before the ref_tracker dir is created, so add a
> late_initcall() to register its files and symlinks.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  net/core/net_namespace.c | 30 +++++++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 8708eb975295ffb78de35fcf4abef7cc281f5a51..39b01af90d240df48827e5c3159c3e2253e0a44d 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -791,12 +791,40 @@ struct net *get_net_ns_by_pid(pid_t pid)
>  }
>  EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
>
> +#ifdef CONFIG_NET_NS_REFCNT_TRACKER
> +static void net_ns_net_debugfs(struct net *net)
> +{
> +       ref_tracker_dir_symlink(&net->refcnt_tracker, "netns--%lx-%u-refcnt",
> +                               net->net_cookie, net->ns.inum);

With proper annotations, you should be able to catch format error as in:

warning: format ‘%lx’ expects argument of type ‘long unsigned int’,
but argument x has type ‘u64’ {aka ‘long long unsigned int’}
[-Wformat=]

Re: [PATCH v10 8/9] net: add symlinks to ref_tracker_dir for netns

[Eric Dumazet]

On Tue, May 27, 2025 at 6:35 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Tue, May 27, 2025 at 4:34 AM Jeff Layton <jlayton@kernel.org> wrote:
> >
> > After assigning the inode number to the namespace, use it to create a
> > unique name for each netns refcount tracker with the ns.inum and
> > net_cookie values in it, and register a symlink to the debugfs file for
> > it.
> >
> > init_net is registered before the ref_tracker dir is created, so add a
> > late_initcall() to register its files and symlinks.
> >
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  net/core/net_namespace.c | 30 +++++++++++++++++++++++++++++-
> >  1 file changed, 29 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> > index 8708eb975295ffb78de35fcf4abef7cc281f5a51..39b01af90d240df48827e5c3159c3e2253e0a44d 100644
> > --- a/net/core/net_namespace.c
> > +++ b/net/core/net_namespace.c
> > @@ -791,12 +791,40 @@ struct net *get_net_ns_by_pid(pid_t pid)
> >  }
> >  EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
> >
> > +#ifdef CONFIG_NET_NS_REFCNT_TRACKER
> > +static void net_ns_net_debugfs(struct net *net)
> > +{
> > +       ref_tracker_dir_symlink(&net->refcnt_tracker, "netns--%lx-%u-refcnt",
> > +                               net->net_cookie, net->ns.inum);
>
> With proper annotations, you should be able to catch format error as in:
>
> warning: format ‘%lx’ expects argument of type ‘long unsigned int’,
> but argument x has type ‘u64’ {aka ‘long long unsigned int’}
> [-Wformat=]

Reference:

include/linux/compiler_attributes.h:158:#define __printf(a, b)
         __attribute__((__format__(printf, a, b)))

Re: [PATCH v10 9/9] ref_tracker: eliminate the ref_tracker_dir name field

[Jeff Layton]

On Tue, 2025-05-27 at 07:33 -0400, Jeff Layton wrote:
> Now that we have dentries and the ability to create meaningful symlinks
> to them, don't keep a name string in each tracker. Switch the output
> format to print "class@address", and drop the name field.
> 
> Also, add a kerneldoc header for ref_tracker_dir_init().
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  drivers/gpu/drm/display/drm_dp_tunnel.c |  2 +-
>  drivers/gpu/drm/i915/intel_runtime_pm.c |  2 +-
>  drivers/gpu/drm/i915/intel_wakeref.c    |  2 +-
>  include/linux/ref_tracker.h             | 20 ++++++++++++++------
>  lib/ref_tracker.c                       |  6 +++---
>  lib/test_ref_tracker.c                  |  2 +-
>  net/core/dev.c                          |  2 +-
>  net/core/net_namespace.c                |  4 ++--
>  8 files changed, 24 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_tunnel.c b/drivers/gpu/drm/display/drm_dp_tunnel.c
> index b9c12b8bf2a3e400b6d8e9d184145834c603b9e1..1205a4432eb4142344fb6eed1cb5ba5b21ec6953 100644
> --- a/drivers/gpu/drm/display/drm_dp_tunnel.c
> +++ b/drivers/gpu/drm/display/drm_dp_tunnel.c
> @@ -1920,7 +1920,7 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
>  	}
>  
>  #ifdef CONFIG_DRM_DISPLAY_DP_TUNNEL_STATE_DEBUG
> -	ref_tracker_dir_init(&mgr->ref_tracker, 16, "drm_dptun", "dptun");
> +	ref_tracker_dir_init(&mgr->ref_tracker, 16, "drm_dptun");
>  #endif
>  
>  	for (i = 0; i < max_group_count; i++) {
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 3fdab3b44c08cea16ac2f73aafc2bea2ffbb19e7..c12b5d0e16fa363f3caede372e7a2031676aa7b5 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -60,7 +60,7 @@ static struct drm_i915_private *rpm_to_i915(struct intel_runtime_pm *rpm)
>  static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
>  {
>  	ref_tracker_dir_init(&rpm->debug, INTEL_REFTRACK_DEAD_COUNT,
> -			     "intel_runtime_pm", dev_name(rpm->kdev));
> +			     "intel_runtime_pm");
>  }
>  

I got a warning from the intel graphics CI that this was causing these
warnings:

<3> [513.235988] debugfs: File 'intel_runtime_pm@ff110001461f98a8' in directory 'ref_tracker' already present!
<4> [513.236073] ref_tracker: ref_tracker: unable to create debugfs file for intel_runtime_pm@ff110001461f98a8: -EEXIST
<3> [513.242646] debugfs: File 'intel_wakeref@ff1100016ee7d790' in directory 'ref_tracker' already present!
<4> [513.242724] ref_tracker: ref_tracker: unable to create debugfs file for intel_wakeref@ff1100016ee7d790: -EEXIST

I suspect these are existing bugs which are causing these ref_trackers
to be initialized more than once. If there were references taken
between these two initializations, then that could leak memory (or
worse). I think we need to ensure that these ref_trackers are only
initialized once.

I'll see if I can make a patch that does that, but if the i915 devs
want to do fix this up instead, I won't complain.


>  static intel_wakeref_t
> diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
> index 5269e64c58a49884f5d712557546272bfdeb8417..615fb77809291be34d94600fdd4d919461a22720 100644
> --- a/drivers/gpu/drm/i915/intel_wakeref.c
> +++ b/drivers/gpu/drm/i915/intel_wakeref.c
> @@ -114,7 +114,7 @@ void __intel_wakeref_init(struct intel_wakeref *wf,
>  			 "wakeref.work", &key->work, 0);
>  
>  #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_WAKEREF)
> -	ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, "intel_wakeref", name);
> +	ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, "intel_wakeref");
>  #endif
>  }
>  
> diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
> index ddc5a7b2bd84692bbc1e1ae67674ec2c6857e1ec..5878e7fce712930700054033ff5f21547e75224f 100644
> --- a/include/linux/ref_tracker.h
> +++ b/include/linux/ref_tracker.h
> @@ -24,7 +24,6 @@ struct ref_tracker_dir {
>  	struct dentry		*dentry;
>  	struct dentry		*symlink;
>  #endif
> -	char			name[32];
>  #endif
>  };
>  
> @@ -48,10 +47,21 @@ void ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...)
>  
>  #endif /* CONFIG_DEBUG_FS */
>  
> +/**
> + * ref_tracker_dir_init - initialize a ref_tracker dir
> + * @dir: ref_tracker_dir to be initialized
> + * @quarantine_count: max number of entries to be tracked
> + * @class: pointer to static string that describes object type
> + *
> + * Initialize a ref_tracker_dir. If debugfs is configured, then a file
> + * will also be created for it under the top-level ref_tracker debugfs
> + * directory.
> + *
> + * Note that @class must point to a static string.
> + */
>  static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
>  					unsigned int quarantine_count,
> -					const char *class,
> -					const char *name)
> +					const char *class)
>  {
>  	INIT_LIST_HEAD(&dir->list);
>  	INIT_LIST_HEAD(&dir->quarantine);
> @@ -65,7 +75,6 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
>  	dir->dentry = NULL;
>  	dir->symlink = NULL;
>  #endif
> -	strscpy(dir->name, name, sizeof(dir->name));
>  	ref_tracker_dir_debugfs(dir);
>  	stack_depot_init();
>  }
> @@ -90,8 +99,7 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
>  
>  static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
>  					unsigned int quarantine_count,
> -					const char *class,
> -					const char *name)
> +					const char *class)
>  {
>  }
>  
> diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
> index 5e84e5fd78e147a036d4adb511e657da07866a55..5fb384dd919e1f1ad632eaf595b954118bcfddab 100644
> --- a/lib/ref_tracker.c
> +++ b/lib/ref_tracker.c
> @@ -123,7 +123,7 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
>  	stats = ref_tracker_get_stats(dir, display_limit);
>  	if (IS_ERR(stats)) {
>  		pr_ostream(s, "%s%s@%p: couldn't get stats, error %pe\n",
> -			   s->prefix, dir->name, dir, stats);
> +			   s->prefix, dir->class, dir, stats);
>  		return;
>  	}
>  
> @@ -134,14 +134,14 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
>  		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
>  			sbuf[0] = 0;
>  		pr_ostream(s, "%s%s@%p has %d/%d users at\n%s\n", s->prefix,
> -			   dir->name, dir, stats->stacks[i].count,
> +			   dir->class, dir, stats->stacks[i].count,
>  			   stats->total, sbuf);
>  		skipped -= stats->stacks[i].count;
>  	}
>  
>  	if (skipped)
>  		pr_ostream(s, "%s%s@%p skipped reports about %d/%d users.\n",
> -			   s->prefix, dir->name, dir, skipped, stats->total);
> +			   s->prefix, dir->class, dir, skipped, stats->total);
>  
>  	kfree(sbuf);
>  
> diff --git a/lib/test_ref_tracker.c b/lib/test_ref_tracker.c
> index d263502a4c1db248f64a66a468e96c8e4cffab25..b983ceb12afcb84ad60360a1e6fec0072e78ef79 100644
> --- a/lib/test_ref_tracker.c
> +++ b/lib/test_ref_tracker.c
> @@ -64,7 +64,7 @@ static int __init test_ref_tracker_init(void)
>  {
>  	int i;
>  
> -	ref_tracker_dir_init(&ref_dir, 100, "selftest", "selftest");
> +	ref_tracker_dir_init(&ref_dir, 100, "selftest");
>  
>  	timer_setup(&test_ref_tracker_timer, test_ref_tracker_timer_func, 0);
>  	mod_timer(&test_ref_tracker_timer, jiffies + 1);
> diff --git a/net/core/dev.c b/net/core/dev.c
> index bac9d29486556023cd99f5101b96b052acb9ba70..a062912525ee573504a9cc252f71aed22693d24f 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -11713,7 +11713,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
>  
>  	dev->priv_len = sizeof_priv;
>  
> -	ref_tracker_dir_init(&dev->refcnt_tracker, 128, "netdev", name);
> +	ref_tracker_dir_init(&dev->refcnt_tracker, 128, "netdev");
>  #ifdef CONFIG_PCPU_DEV_REFCNT
>  	dev->pcpu_refcnt = alloc_percpu(int);
>  	if (!dev->pcpu_refcnt)
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 39b01af90d240df48827e5c3159c3e2253e0a44d..c03757e39c8a334d307fa1b5cc8f03ad3a8df0e0 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -403,8 +403,8 @@ static __net_init void preinit_net(struct net *net, struct user_namespace *user_
>  {
>  	refcount_set(&net->passive, 1);
>  	refcount_set(&net->ns.count, 1);
> -	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt", "net_refcnt");
> -	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt", "net_notrefcnt");
> +	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt");
> +	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt");
>  
>  	get_random_bytes(&net->hash_mix, sizeof(u32));
>  	net->dev_base_seq = 1;

-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH v10 8/9] net: add symlinks to ref_tracker_dir for netns

[Jeff Layton]

On Tue, 2025-05-27 at 06:37 -0700, Eric Dumazet wrote:
> On Tue, May 27, 2025 at 6:35 AM Eric Dumazet <edumazet@google.com> wrote:
> > 
> > On Tue, May 27, 2025 at 4:34 AM Jeff Layton <jlayton@kernel.org> wrote:
> > > 
> > > After assigning the inode number to the namespace, use it to create a
> > > unique name for each netns refcount tracker with the ns.inum and
> > > net_cookie values in it, and register a symlink to the debugfs file for
> > > it.
> > > 
> > > init_net is registered before the ref_tracker dir is created, so add a
> > > late_initcall() to register its files and symlinks.
> > > 
> > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > ---
> > >  net/core/net_namespace.c | 30 +++++++++++++++++++++++++++++-
> > >  1 file changed, 29 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> > > index 8708eb975295ffb78de35fcf4abef7cc281f5a51..39b01af90d240df48827e5c3159c3e2253e0a44d 100644
> > > --- a/net/core/net_namespace.c
> > > +++ b/net/core/net_namespace.c
> > > @@ -791,12 +791,40 @@ struct net *get_net_ns_by_pid(pid_t pid)
> > >  }
> > >  EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
> > > 
> > > +#ifdef CONFIG_NET_NS_REFCNT_TRACKER
> > > +static void net_ns_net_debugfs(struct net *net)
> > > +{
> > > +       ref_tracker_dir_symlink(&net->refcnt_tracker, "netns--%lx-%u-refcnt",
> > > +                               net->net_cookie, net->ns.inum);
> > 
> > With proper annotations, you should be able to catch format error as in:
> > 
> > warning: format ‘%lx’ expects argument of type ‘long unsigned int’,
> > but argument x has type ‘u64’ {aka ‘long long unsigned int’}
> > [-Wformat=]
> 
> Reference:
> 
> include/linux/compiler_attributes.h:158:#define __printf(a, b)
>          __attribute__((__format__(printf, a, b)))


I have __printf annotations on that function:

    #define __ostream_printf __printf(2, 3)

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

That warning is complaining that I'm trying to pass off a u64 as a
long. I guess that means that the format needs to be 
"netns-%llx-%u-refcnt" ?

I'll fix that and send in the next version, once I sort out the i915
mess.
-- 
Jeff Layton <jlayton@kernel.org>