[PATCH RESEND v3 2/3] lib, stackdepot: Add helper to print stack entries.

[Imran Khan <imran.f.khan@xxxxxxxxxx>]

To print a stack entries, users of stackdepot, first
use stack_depot_fetch to get a list of stack entries
and then use stack_trace_print to print this list.
Provide a helper in stackdepot to print stack entries
based on stackdepot handle.
Also change above mentioned users to use this helper.

Signed-off-by: Imran Khan <imran.f.khan@xxxxxxxxxx>
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
 include/linux/stackdepot.h |  2 ++
 lib/stackdepot.c           | 18 ++++++++++++++++++
 mm/kasan/report.c          | 15 +++------------
 mm/page_owner.c            | 13 ++++---------
 4 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index 6bb4bc1a5f54..d77a30543dd4 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -19,6 +19,8 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
 unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 			       unsigned long **entries);
 
+void stack_depot_print(depot_stack_handle_t stack);
+
 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries);
 
 #ifdef CONFIG_STACKDEPOT
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 67439c082490..354fe1b62017 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -214,6 +214,24 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
 	return NULL;
 }
 
+/**
+ * stack_depot_print - print stack entries from a depot
+ *
+ * @stack:		Stack depot handle which was returned from
+ *			stack_depot_save().
+ *
+ */
+void stack_depot_print(depot_stack_handle_t stack)
+{
+	unsigned long *entries;
+	unsigned int nr_entries;
+
+	nr_entries = stack_depot_fetch(stack, &entries);
+	if (nr_entries > 0)
+		stack_trace_print(entries, nr_entries, 0);
+}
+EXPORT_SYMBOL_GPL(stack_depot_print);
+
 /**
  * stack_depot_fetch - Fetch stack entries from a depot
  *
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 884a950c7026..3239fd8f8747 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -132,20 +132,11 @@ static void end_report(unsigned long *flags, unsigned long addr)
 	kasan_enable_current();
 }
 
-static void print_stack(depot_stack_handle_t stack)
-{
-	unsigned long *entries;
-	unsigned int nr_entries;
-
-	nr_entries = stack_depot_fetch(stack, &entries);
-	stack_trace_print(entries, nr_entries, 0);
-}
-
 static void print_track(struct kasan_track *track, const char *prefix)
 {
 	pr_err("%s by task %u:\n", prefix, track->pid);
 	if (track->stack) {
-		print_stack(track->stack);
+		stack_depot_print(track->stack);
 	} else {
 		pr_err("(stack is not available)\n");
 	}
@@ -214,12 +205,12 @@ static void describe_object_stacks(struct kmem_cache *cache, void *object,
 		return;
 	if (alloc_meta->aux_stack[0]) {
 		pr_err("Last potentially related work creation:\n");
-		print_stack(alloc_meta->aux_stack[0]);
+		stack_depot_print(alloc_meta->aux_stack[0]);
 		pr_err("\n");
 	}
 	if (alloc_meta->aux_stack[1]) {
 		pr_err("Second to last potentially related work creation:\n");
-		print_stack(alloc_meta->aux_stack[1]);
+		stack_depot_print(alloc_meta->aux_stack[1]);
 		pr_err("\n");
 	}
 #endif
diff --git a/mm/page_owner.c b/mm/page_owner.c
index d24ed221357c..7918770c2b2b 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -394,8 +394,6 @@ void __dump_page_owner(const struct page *page)
 	struct page_ext *page_ext = lookup_page_ext(page);
 	struct page_owner *page_owner;
 	depot_stack_handle_t handle;
-	unsigned long *entries;
-	unsigned int nr_entries;
 	gfp_t gfp_mask;
 	int mt;
 
@@ -423,20 +421,17 @@ void __dump_page_owner(const struct page *page)
 		 page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec);
 
 	handle = READ_ONCE(page_owner->handle);
-	if (!handle) {
+	if (!handle)
 		pr_alert("page_owner allocation stack trace missing\n");
-	} else {
-		nr_entries = stack_depot_fetch(handle, &entries);
-		stack_trace_print(entries, nr_entries, 0);
-	}
+	else
+		stack_depot_print(handle);
 
 	handle = READ_ONCE(page_owner->free_handle);
 	if (!handle) {
 		pr_alert("page_owner free stack trace missing\n");
 	} else {
-		nr_entries = stack_depot_fetch(handle, &entries);
 		pr_alert("page last free stack trace:\n");
-		stack_trace_print(entries, nr_entries, 0);
+		stack_depot_print(handle);
 	}
 
 	if (page_owner->last_migrate_reason != -1)
-- 
2.30.2