[RFC PATCH] mm: introduce accounting of page_owner via backtrace

["zhaoyang.huang" <zhaoyang.huang@unisoc.com>]

From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Page_owner could be accounted and sort via its backtrace, which could
simplify the output.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 include/linux/page_owner.h |   7 +++
 mm/page_owner.c            | 113 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)

diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 119a0c9..c86a342 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -3,6 +3,13 @@
 #define __LINUX_PAGE_OWNER_H
 
 #include <linux/jump_label.h>
+#include <linux/stackdepot.h>
+
+struct hash_object {
+	int count;
+	depot_stack_handle_t trace_hash;
+	struct rb_node rb_node;
+};
 
 #ifdef CONFIG_PAGE_OWNER
 extern struct static_key_false page_owner_inited;
diff --git a/mm/page_owner.c b/mm/page_owner.c
index e4c6f3f..3d014fd 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -42,6 +42,12 @@ struct page_owner {
 static depot_stack_handle_t early_handle;
 
 static void init_early_allocated_pages(void);
+static void store_user_hash(depot_stack_handle_t trace_hash, int count);
+static DEFINE_SPINLOCK(stack_hash_lock);
+static struct hash_object ho_pool[8192];
+static int ho_pool_free_count = ARRAY_SIZE(ho_pool);
+struct rb_root user_hash_root = RB_ROOT;
+
 
 static int __init early_page_owner_param(char *buf)
 {
@@ -152,6 +158,8 @@ void __reset_page_owner(struct page *page, unsigned short order)
 		page_owner->free_handle = handle;
 		page_owner->free_ts_nsec = free_ts_nsec;
 		page_ext = page_ext_next(page_ext);
+		if (!i)
+			store_user_hash(page_owner->handle, -(1 << order));
 	}
 }
 
@@ -190,6 +198,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
 		return;
 
 	handle = save_stack(gfp_mask);
+	store_user_hash(handle, 1 << order);
 	__set_page_owner_handle(page_ext, handle, order, gfp_mask);
 }
 
@@ -570,6 +579,105 @@ void __dump_page_owner(const struct page *page)
 	return 0;
 }
 
+static void store_user_hash(depot_stack_handle_t trace_hash, int count)
+{
+	struct rb_node *rb_parent;
+	unsigned int trace_hash_parent;
+	struct rb_node **link = &user_hash_root.rb_node;
+	struct hash_object *hash_parent = NULL;
+	struct hash_object *hash_object = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&stack_hash_lock, flags);
+	while (*link) {
+		rb_parent = *link;
+		hash_parent = rb_entry(rb_parent, struct hash_object, rb_node);
+		trace_hash_parent = hash_parent->trace_hash;
+		if (trace_hash < trace_hash_parent)
+			link = &hash_parent->rb_node.rb_left;
+		else if (trace_hash_parent < trace_hash)
+			link = &hash_parent->rb_node.rb_right;
+		else {
+			hash_object = rb_entry(*link, struct hash_object, rb_node);
+			hash_object->count += count;
+			if (!RB_EMPTY_ROOT(&user_hash_root)
+					&& !hash_object->count) {
+				rb_erase(&hash_object->rb_node, &user_hash_root);
+			}
+			spin_unlock_irqrestore(&stack_hash_lock, flags);
+			return;
+		}
+	}
+	/*
+	 * hash_object is the 1st node represent this trace_hash
+	 * insert it to user_hash_root
+	 */
+	hash_object = ho_pool_free_count ? &ho_pool[--ho_pool_free_count] : NULL;
+	if (!hash_object) {
+		spin_unlock_irqrestore(&stack_hash_lock, flags);
+		return;
+	}
+	hash_object->trace_hash = trace_hash;
+	/* add the node to rb tree*/
+	rb_link_node(&hash_object->rb_node, rb_parent, link);
+	rb_insert_color(&hash_object->rb_node, &user_hash_root);
+	spin_unlock_irqrestore(&stack_hash_lock, flags);
+	return;
+}
+static ssize_t print_owner_stack(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+	struct hash_object *object;
+	struct rb_node *rb;
+	unsigned long *entries;
+	unsigned int nr_entries;
+	char *kbuf;
+	int i, ret = 0;
+	unsigned long flags;
+
+	count = min_t(size_t, count, PAGE_SIZE);
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	rb = file->private_data ? (struct rb_node *)file->private_data : rb_first(&user_hash_root);
+	if(!rb)
+		return 0;
+	spin_lock_irqsave(&stack_hash_lock, flags);
+	object = rb_entry(rb, struct hash_object, rb_node);
+	if (object) {
+		while (!object->trace_hash || object->count <= 0) {
+			rb = rb_next(rb);
+			object = rb ? rb_entry(rb, struct hash_object, rb_node) : NULL;
+			if (!object) {
+				spin_unlock_irqrestore(&stack_hash_lock, flags);
+				kfree(kbuf);
+				return 0;
+			}
+		}
+		nr_entries = stack_depot_fetch(object->trace_hash, &entries);
+		ret += snprintf(kbuf + ret, count - ret, "count %d\n", object->count);
+		if (ret >= count)
+			goto err;
+		for (i = 0; i < nr_entries; i++) {
+			void *ptr = (void *)entries[i];
+			ret += snprintf(kbuf + ret, count - ret, "    [<%p>] %pS\n", ptr, ptr);
+			if (ret >= count)
+				goto err;
+		}
+	}
+	file->private_data = (void *)rb_next(rb);
+	spin_unlock_irqrestore(&stack_hash_lock, flags);
+	if (copy_to_user(buf, kbuf, ret))
+		ret = -EFAULT;
+
+	kfree(kbuf);
+	return ret;
+err:
+	spin_unlock_irqrestore(&stack_hash_lock, flags);
+	kfree(kbuf);
+	return -ENOMEM;
+}
+
 static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 {
 	unsigned long pfn = zone->zone_start_pfn;
@@ -661,6 +769,9 @@ static void init_early_allocated_pages(void)
 static const struct file_operations proc_page_owner_operations = {
 	.read		= read_page_owner,
 };
+static const struct file_operations proc_page_owner_simple_operations = {
+	.read		= print_owner_stack,
+};
 
 static int __init pageowner_init(void)
 {
@@ -671,6 +782,8 @@ static int __init pageowner_init(void)
 
 	debugfs_create_file("page_owner", 0400, NULL, NULL,
 			    &proc_page_owner_operations);
+	debugfs_create_file("page_owner_simple", 0400, NULL, NULL,
+			    &proc_page_owner_simple_operations);
 
 	return 0;
 }
-- 
1.9.1