[RFC PATCHv2] mm: use stack_depot for recording kmemleak's backtrace

["zhaoyang.huang" <zhaoyang.huang@xxxxxxxxxx>]

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

Using stack_depot to record kmemleak's backtrace which has been implemented
on slub for reducing redundant information.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
changes of v2: fix bugs of stack_depot_init related issue
---
---
 mm/kmemleak.c | 45 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 1eddc01..0f78774 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -79,6 +79,7 @@
 #include <linux/mutex.h>
 #include <linux/rcupdate.h>
 #include <linux/stacktrace.h>
+#include <linux/stackdepot.h>
 #include <linux/cache.h>
 #include <linux/percpu.h>
 #include <linux/memblock.h>
@@ -159,8 +160,7 @@ struct kmemleak_object {
 	u32 checksum;
 	/* memory ranges to be scanned inside an object (empty for all) */
 	struct hlist_head area_list;
-	unsigned long trace[MAX_TRACE];
-	unsigned int trace_len;
+	depot_stack_handle_t trace_handle;
 	unsigned long jiffies;		/* creation timestamp */
 	pid_t pid;			/* pid of the current task */
 	char comm[TASK_COMM_LEN];	/* executable name */
@@ -346,8 +346,11 @@ static void print_unreferenced(struct seq_file *seq,
 			       struct kmemleak_object *object)
 {
 	int i;
+	unsigned long *entries;
+	unsigned int nr_entries;
 	unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
 
+	nr_entries = stack_depot_fetch(object->trace_handle, &entries);
 	warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
 		   object->pointer, object->size);
 	warn_or_seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
@@ -356,10 +359,10 @@ static void print_unreferenced(struct seq_file *seq,
 	hex_dump_object(seq, object);
 	warn_or_seq_printf(seq, "  backtrace:\n");
 
-	for (i = 0; i < object->trace_len; i++) {
-		void *ptr = (void *)object->trace[i];
-		warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
-	}
+       for (i = 0; i < nr_entries; i++) {
+               void *ptr = (void *)entries[i];
+               warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
+       }
 }
 
 /*
@@ -378,7 +381,8 @@ static void dump_object_info(struct kmemleak_object *object)
 	pr_notice("  flags = 0x%x\n", object->flags);
 	pr_notice("  checksum = %u\n", object->checksum);
 	pr_notice("  backtrace:\n");
-	stack_trace_print(object->trace, object->trace_len, 4);
+	if(object->trace_handle)
+		stack_depot_print(object->trace_handle);
 }
 
 /*
@@ -591,6 +595,27 @@ static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int ali
 	return object;
 }
 
+#ifdef CONFIG_STACKDEPOT
+static noinline depot_stack_handle_t set_track_prepare(void)
+{
+	depot_stack_handle_t trace_handle;
+	unsigned long entries[MAX_TRACE];
+	unsigned int nr_entries;
+
+	if (!kmemleak_initialized)
+		stack_depot_init();
+	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
+	trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
+
+	return trace_handle;
+}
+#else
+static inline depot_stack_handle_t set_track_prepare(void)
+{
+	return 0;
+}
+#endif
+
 /*
  * Save stack trace to the given array of MAX_TRACE size.
  */
@@ -654,7 +679,7 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
 	}
 
 	/* kernel backtrace */
-	object->trace_len = __save_stack_trace(object->trace);
+	object->trace_handle = set_track_prepare();
 
 	raw_spin_lock_irqsave(&kmemleak_lock, flags);
 
@@ -694,7 +719,6 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
 	rb_link_node(&object->rb_node, rb_parent, link);
 	rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
 					  &object_tree_root);
-
 	list_add_tail_rcu(&object->object_list, &object_list);
 out:
 	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
@@ -1094,7 +1118,7 @@ void __ref kmemleak_update_trace(const void *ptr)
 	}
 
 	raw_spin_lock_irqsave(&object->lock, flags);
-	object->trace_len = __save_stack_trace(object->trace);
+	object->trace_handle = set_track_prepare();
 	raw_spin_unlock_irqrestore(&object->lock, flags);
 
 	put_object(object);
@@ -2064,6 +2088,7 @@ void __init kmemleak_init(void)
 	if (kmemleak_error)
 		return;
 
+	stack_depot_init();
 	jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
 	jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
 
-- 
1.9.1