To improve readability of ref_tracker printing following changes
have been performed:
- reports are printed per stack_handle - log is more compact,
- added display name for ref_tracker_dir,
- stack trace is printed indented, in the same printk call,
- total number of references is printed every time,
- print info about dropped references.

Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
---
 include/linux/ref_tracker.h | 15 ++++++--
 lib/ref_tracker.c           | 90 +++++++++++++++++++++++++++++++++++++++------
 2 files changed, 91 insertions(+), 14 deletions(-)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index 3e9e9df2a41f5f..a2cf1f6309adb2 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -17,12 +17,19 @@ struct ref_tracker_dir {
 	bool			dead;
 	struct list_head	list; /* List of active trackers */
 	struct list_head	quarantine; /* List of dead trackers */
+	char			name[32];
 #endif
 };
 
 #ifdef CONFIG_REF_TRACKER
-static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
-					unsigned int quarantine_count)
+
+// Temporary allow two and three arguments, until consumers are converted
+#define ref_tracker_dir_init(_d, _q, args...) _ref_tracker_dir_init(_d, _q, ##args, #_d)
+#define _ref_tracker_dir_init(_d, _q, _n, ...) __ref_tracker_dir_init(_d, _q, _n)
+
+static inline void __ref_tracker_dir_init(struct ref_tracker_dir *dir,
+					unsigned int quarantine_count,
+					const char *name)
 {
 	INIT_LIST_HEAD(&dir->list);
 	INIT_LIST_HEAD(&dir->quarantine);
@@ -31,6 +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);
+	strlcpy(dir->name, name, sizeof(dir->name));
 	stack_depot_init();
 }
 
@@ -51,7 +59,8 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
 #else /* CONFIG_REF_TRACKER */
 
 static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
-					unsigned int quarantine_count)
+					unsigned int quarantine_count,
+					...)
 {
 }
 
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index 5e9f90bbf771b0..ab1253fde244ea 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -1,11 +1,16 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
+
+#define pr_fmt(fmt) "ref_tracker: " fmt
+
 #include <linux/export.h>
+#include <linux/list_sort.h>
 #include <linux/ref_tracker.h>
 #include <linux/slab.h>
 #include <linux/stacktrace.h>
 #include <linux/stackdepot.h>
 
 #define REF_TRACKER_STACK_ENTRIES 16
+#define STACK_BUF_SIZE 1024
 
 struct ref_tracker {
 	struct list_head	head;   /* anchor into dir->list or dir->quarantine */
@@ -14,24 +19,87 @@ struct ref_tracker {
 	depot_stack_handle_t	free_stack_handle;
 };
 
-void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
-			   unsigned int display_limit)
+struct ref_tracker_dir_stats {
+	int total;
+	int count;
+	struct {
+		depot_stack_handle_t stack_handle;
+		unsigned int count;
+	} stacks[];
+};
+
+static struct ref_tracker_dir_stats *
+ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
 {
+	struct ref_tracker_dir_stats *stats;
 	struct ref_tracker *tracker;
-	unsigned int i = 0;
 
-	lockdep_assert_held(&dir->lock);
+	stats = kmalloc(struct_size(stats, stacks, limit),
+			GFP_NOWAIT | __GFP_NOWARN);
+	if (!stats)
+		return ERR_PTR(-ENOMEM);
+	stats->total = 0;
+	stats->count = 0;
 
 	list_for_each_entry(tracker, &dir->list, head) {
-		if (i < display_limit) {
-			pr_err("leaked reference.\n");
-			if (tracker->alloc_stack_handle)
-				stack_depot_print(tracker->alloc_stack_handle);
-			i++;
-		} else {
-			break;
+		depot_stack_handle_t stack = tracker->alloc_stack_handle;
+		int i;
+
+		++stats->total;
+		for (i = 0; i < stats->count; ++i)
+			if (stats->stacks[i].stack_handle == stack)
+				break;
+		if (i >= limit)
+			continue;
+		if (i >= stats->count) {
+			stats->stacks[i].stack_handle = stack;
+			stats->stacks[i].count = 0;
+			++stats->count;
 		}
+		++stats->stacks[i].count;
+	}
+
+	return stats;
+}
+
+void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
+			   unsigned int display_limit)
+{
+	struct ref_tracker_dir_stats *stats;
+	unsigned int i = 0, skipped;
+	depot_stack_handle_t stack;
+	char *sbuf;
+
+	lockdep_assert_held(&dir->lock);
+
+	if (list_empty(&dir->list))
+		return;
+
+	stats = ref_tracker_get_stats(dir, display_limit);
+	if (IS_ERR(stats)) {
+		pr_err("%s@%pK: couldn't get stats, error %pe\n",
+		       dir->name, dir, stats);
+		return;
 	}
+
+	sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN);
+
+	for (i = 0, skipped = stats->total; i < stats->count; ++i) {
+		stack = stats->stacks[i].stack_handle;
+		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
+			sbuf[0] = 0;
+		pr_err("%s@%pK 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_err("%s@%pK skipped reports about %d/%d users.\n",
+		       dir->name, dir, skipped, stats->total);
+
+	kfree(sbuf);
+
+	kfree(stats);
 }
 EXPORT_SYMBOL(__ref_tracker_dir_print);
 

-- 
2.34.1

Hi Andrzej,

looks good, few comments below,

On Mon, Mar 06, 2023 at 05:31:58PM +0100, Andrzej Hajda wrote:
> To improve readability of ref_tracker printing following changes
> have been performed:
> - reports are printed per stack_handle - log is more compact,
> - added display name for ref_tracker_dir,
> - stack trace is printed indented, in the same printk call,
> - total number of references is printed every time,
> - print info about dropped references.

nit: I think you can do better with the log :)

> Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
> ---
>  include/linux/ref_tracker.h | 15 ++++++--
>  lib/ref_tracker.c           | 90 +++++++++++++++++++++++++++++++++++++++------
>  2 files changed, 91 insertions(+), 14 deletions(-)
> 
> diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
> index 3e9e9df2a41f5f..a2cf1f6309adb2 100644
> --- a/include/linux/ref_tracker.h
> +++ b/include/linux/ref_tracker.h
> @@ -17,12 +17,19 @@ struct ref_tracker_dir {
>  	bool			dead;
>  	struct list_head	list; /* List of active trackers */
>  	struct list_head	quarantine; /* List of dead trackers */
> +	char			name[32];
>  #endif
>  };
>  
>  #ifdef CONFIG_REF_TRACKER
> -static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
> -					unsigned int quarantine_count)
> +
> +// Temporary allow two and three arguments, until consumers are converted

I thought only Linus was allowed to use '//' :)

> +#define ref_tracker_dir_init(_d, _q, args...) _ref_tracker_dir_init(_d, _q, ##args, #_d)
> +#define _ref_tracker_dir_init(_d, _q, _n, ...) __ref_tracker_dir_init(_d, _q, _n)

[...]

> +void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
> +			   unsigned int display_limit)
> +{
> +	struct ref_tracker_dir_stats *stats;
> +	unsigned int i = 0, skipped;
> +	depot_stack_handle_t stack;
> +	char *sbuf;
> +
> +	lockdep_assert_held(&dir->lock);
> +
> +	if (list_empty(&dir->list))
> +		return;
> +
> +	stats = ref_tracker_get_stats(dir, display_limit);
> +	if (IS_ERR(stats)) {
> +		pr_err("%s@%pK: couldn't get stats, error %pe\n",
> +		       dir->name, dir, stats);
> +		return;
>  	}
> +
> +	sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN);
> +
> +	for (i = 0, skipped = stats->total; i < stats->count; ++i) {
> +		stack = stats->stacks[i].stack_handle;
> +		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
> +			sbuf[0] = 0;
> +		pr_err("%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
> +		       stats->stacks[i].count, stats->total, sbuf);

what if sbuf is NULL?

> +		skipped -= stats->stacks[i].count;
> +	}
> +
> +	if (skipped)

is skipped used to double check whether stats->count is equal to
all the stacks[].conunts? What are the cases when skipped is > 0?

Andi

> +		pr_err("%s@%pK skipped reports about %d/%d users.\n",
> +		       dir->name, dir, skipped, stats->total);
> +
> +	kfree(sbuf);
> +
> +	kfree(stats);
>  }
>  EXPORT_SYMBOL(__ref_tracker_dir_print);
>  
> 
> -- 
> 2.34.1

On 20.03.2023 00:11, Andi Shyti wrote:
> Hi Andrzej,
> 
> looks good, few comments below,
> 
> On Mon, Mar 06, 2023 at 05:31:58PM +0100, Andrzej Hajda wrote:
>> To improve readability of ref_tracker printing following changes
>> have been performed:
>> - reports are printed per stack_handle - log is more compact,
>> - added display name for ref_tracker_dir,
>> - stack trace is printed indented, in the same printk call,
>> - total number of references is printed every time,
>> - print info about dropped references.
> 
> nit: I think you can do better with the log :)
> 
>> Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
>> ---
>>   include/linux/ref_tracker.h | 15 ++++++--
>>   lib/ref_tracker.c           | 90 +++++++++++++++++++++++++++++++++++++++------
>>   2 files changed, 91 insertions(+), 14 deletions(-)
>>
>> diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
>> index 3e9e9df2a41f5f..a2cf1f6309adb2 100644
>> --- a/include/linux/ref_tracker.h
>> +++ b/include/linux/ref_tracker.h
>> @@ -17,12 +17,19 @@ struct ref_tracker_dir {
>>   	bool			dead;
>>   	struct list_head	list; /* List of active trackers */
>>   	struct list_head	quarantine; /* List of dead trackers */
>> +	char			name[32];
>>   #endif
>>   };
>>   
>>   #ifdef CONFIG_REF_TRACKER
>> -static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
>> -					unsigned int quarantine_count)
>> +
>> +// Temporary allow two and three arguments, until consumers are converted
> 
> I thought only Linus was allowed to use '//' :)
> 
>> +#define ref_tracker_dir_init(_d, _q, args...) _ref_tracker_dir_init(_d, _q, ##args, #_d)
>> +#define _ref_tracker_dir_init(_d, _q, _n, ...) __ref_tracker_dir_init(_d, _q, _n)
> 
> [...]
> 
>> +void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
>> +			   unsigned int display_limit)
>> +{
>> +	struct ref_tracker_dir_stats *stats;
>> +	unsigned int i = 0, skipped;
>> +	depot_stack_handle_t stack;
>> +	char *sbuf;
>> +
>> +	lockdep_assert_held(&dir->lock);
>> +
>> +	if (list_empty(&dir->list))
>> +		return;
>> +
>> +	stats = ref_tracker_get_stats(dir, display_limit);
>> +	if (IS_ERR(stats)) {
>> +		pr_err("%s@%pK: couldn't get stats, error %pe\n",
>> +		       dir->name, dir, stats);
>> +		return;
>>   	}
>> +
>> +	sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN);
>> +
>> +	for (i = 0, skipped = stats->total; i < stats->count; ++i) {
>> +		stack = stats->stacks[i].stack_handle;
>> +		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
>> +			sbuf[0] = 0;
>> +		pr_err("%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
>> +		       stats->stacks[i].count, stats->total, sbuf);
> 
> what if sbuf is NULL?

Then "(NULL)" will be printed, I suspect it will occur only on very rare 
occasions.

> 
>> +		skipped -= stats->stacks[i].count;
>> +	}
>> +
>> +	if (skipped)
> 
> is skipped used to double check whether stats->count is equal to
> all the stacks[].conunts? What are the cases when skipped is > 0?

There is display_limit parameter, so the function prints up to 
display_limit reports, and brief summary on remaining ones - the skipped 
ones.

Regards
Andrzej


> 
> Andi
> 
>> +		pr_err("%s@%pK skipped reports about %d/%d users.\n",
>> +		       dir->name, dir, skipped, stats->total);
>> +
>> +	kfree(sbuf);
>> +
>> +	kfree(stats);
>>   }
>>   EXPORT_SYMBOL(__ref_tracker_dir_print);
>>   
>>
>> -- 
>> 2.34.1