#include <linux/debugfs.h>
  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/uaccess.h>
  #include <linux/bootmem.h>
  #include <linux/stacktrace.h>
  #include <linux/page_owner.h>

  #include <linux/jump_label.h>

  #include <linux/migrate.h>

  #include <linux/stackdepot.h>

  #include "internal.h"

  /*
   * TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack)
   * to use off stack temporal storage
   */
  #define PAGE_OWNER_STACK_DEPTH (16)

  static bool page_owner_disabled = true;

  DEFINE_STATIC_KEY_FALSE(page_owner_inited);

  static depot_stack_handle_t dummy_handle;
  static depot_stack_handle_t failure_handle;

  static void init_early_allocated_pages(void);

  static int early_page_owner_param(char *buf)
  {
  	if (!buf)
  		return -EINVAL;
  
  	if (strcmp(buf, "on") == 0)
  		page_owner_disabled = false;
  
  	return 0;
  }
  early_param("page_owner", early_page_owner_param);
  
  static bool need_page_owner(void)
  {
  	if (page_owner_disabled)
  		return false;
  
  	return true;
  }

  static noinline void register_dummy_stack(void)
  {
  	unsigned long entries[4];
  	struct stack_trace dummy;
  
  	dummy.nr_entries = 0;
  	dummy.max_entries = ARRAY_SIZE(entries);
  	dummy.entries = &entries[0];
  	dummy.skip = 0;
  
  	save_stack_trace(&dummy);
  	dummy_handle = depot_save_stack(&dummy, GFP_KERNEL);
  }
  
  static noinline void register_failure_stack(void)
  {
  	unsigned long entries[4];
  	struct stack_trace failure;
  
  	failure.nr_entries = 0;
  	failure.max_entries = ARRAY_SIZE(entries);
  	failure.entries = &entries[0];
  	failure.skip = 0;
  
  	save_stack_trace(&failure);
  	failure_handle = depot_save_stack(&failure, GFP_KERNEL);
  }

  static void init_page_owner(void)
  {
  	if (page_owner_disabled)
  		return;

  	register_dummy_stack();
  	register_failure_stack();

  	static_branch_enable(&page_owner_inited);

  	init_early_allocated_pages();

  }
  
  struct page_ext_operations page_owner_ops = {
  	.need = need_page_owner,
  	.init = init_page_owner,
  };
  
  void __reset_page_owner(struct page *page, unsigned int order)
  {
  	int i;
  	struct page_ext *page_ext;
  
  	for (i = 0; i < (1 << order); i++) {
  		page_ext = lookup_page_ext(page + i);

  		if (unlikely(!page_ext))
  			continue;

  		__clear_bit(PAGE_EXT_OWNER, &page_ext->flags);
  	}
  }

  static inline bool check_recursive_alloc(struct stack_trace *trace,
  					unsigned long ip)

  {

  	int i, count;
  
  	if (!trace->nr_entries)
  		return false;
  
  	for (i = 0, count = 0; i < trace->nr_entries; i++) {
  		if (trace->entries[i] == ip && ++count == 2)
  			return true;
  	}

  	return false;
  }
  
  static noinline depot_stack_handle_t save_stack(gfp_t flags)
  {
  	unsigned long entries[PAGE_OWNER_STACK_DEPTH];

  	struct stack_trace trace = {
  		.nr_entries = 0,

  		.entries = entries,
  		.max_entries = PAGE_OWNER_STACK_DEPTH,
  		.skip = 0

  	};

  	depot_stack_handle_t handle;
  
  	save_stack_trace(&trace);
  	if (trace.nr_entries != 0 &&
  	    trace.entries[trace.nr_entries-1] == ULONG_MAX)
  		trace.nr_entries--;
  
  	/*
  	 * We need to check recursion here because our request to stackdepot
  	 * could trigger memory allocation to save new entry. New memory
  	 * allocation would reach here and call depot_save_stack() again
  	 * if we don't catch it. There is still not enough memory in stackdepot
  	 * so it would try to allocate memory again and loop forever.
  	 */
  	if (check_recursive_alloc(&trace, _RET_IP_))
  		return dummy_handle;
  
  	handle = depot_save_stack(&trace, flags);
  	if (!handle)
  		handle = failure_handle;
  
  	return handle;
  }
  
  noinline void __set_page_owner(struct page *page, unsigned int order,
  					gfp_t gfp_mask)
  {
  	struct page_ext *page_ext = lookup_page_ext(page);

  	if (unlikely(!page_ext))
  		return;

  	page_ext->handle = save_stack(gfp_mask);

  	page_ext->order = order;
  	page_ext->gfp_mask = gfp_mask;

  	page_ext->last_migrate_reason = -1;

  
  	__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
  }

  void __set_page_owner_migrate_reason(struct page *page, int reason)
  {
  	struct page_ext *page_ext = lookup_page_ext(page);

  	if (unlikely(!page_ext))
  		return;

  
  	page_ext->last_migrate_reason = reason;
  }

  void __split_page_owner(struct page *page, unsigned int order)

  {

  	int i;

  	struct page_ext *page_ext = lookup_page_ext(page);

  	if (unlikely(!page_ext))

  		return;

  	page_ext->order = 0;
  	for (i = 1; i < (1 << order); i++)
  		__copy_page_owner(page, page + i);

  }

  void __copy_page_owner(struct page *oldpage, struct page *newpage)
  {
  	struct page_ext *old_ext = lookup_page_ext(oldpage);
  	struct page_ext *new_ext = lookup_page_ext(newpage);

  	if (unlikely(!old_ext || !new_ext))
  		return;

  	new_ext->order = old_ext->order;
  	new_ext->gfp_mask = old_ext->gfp_mask;

  	new_ext->last_migrate_reason = old_ext->last_migrate_reason;

  	new_ext->handle = old_ext->handle;

  
  	/*
  	 * We don't clear the bit on the oldpage as it's going to be freed
  	 * after migration. Until then, the info can be useful in case of
  	 * a bug, and the overal stats will be off a bit only temporarily.
  	 * Also, migrate_misplaced_transhuge_page() can still fail the
  	 * migration and then we want the oldpage to retain the info. But
  	 * in that case we also don't need to explicitly clear the info from
  	 * the new page, which will be freed.
  	 */
  	__set_bit(PAGE_EXT_OWNER, &new_ext->flags);
  }

  static ssize_t
  print_page_owner(char __user *buf, size_t count, unsigned long pfn,

  		struct page *page, struct page_ext *page_ext,
  		depot_stack_handle_t handle)

  {
  	int ret;
  	int pageblock_mt, page_mt;
  	char *kbuf;

  	unsigned long entries[PAGE_OWNER_STACK_DEPTH];

  	struct stack_trace trace = {

  		.nr_entries = 0,
  		.entries = entries,
  		.max_entries = PAGE_OWNER_STACK_DEPTH,
  		.skip = 0

  	};

  
  	kbuf = kmalloc(count, GFP_KERNEL);
  	if (!kbuf)
  		return -ENOMEM;
  
  	ret = snprintf(kbuf, count,

  			"Page allocated via order %u, mask %#x(%pGg)
  ",
  			page_ext->order, page_ext->gfp_mask,
  			&page_ext->gfp_mask);

  
  	if (ret >= count)
  		goto err;
  
  	/* Print information relevant to grouping pages by mobility */

  	pageblock_mt = get_pageblock_migratetype(page);

  	page_mt  = gfpflags_to_migratetype(page_ext->gfp_mask);
  	ret += snprintf(kbuf + ret, count - ret,

  			"PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)
  ",

  			pfn,

  			migratetype_names[page_mt],

  			pfn >> pageblock_order,

  			migratetype_names[pageblock_mt],
  			page->flags, &page->flags);

  
  	if (ret >= count)
  		goto err;

  	depot_fetch_stack(handle, &trace);

  	ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0);

  	if (ret >= count)
  		goto err;

  	if (page_ext->last_migrate_reason != -1) {
  		ret += snprintf(kbuf + ret, count - ret,
  			"Page has been migrated, last migrate reason: %s
  ",
  			migrate_reason_names[page_ext->last_migrate_reason]);
  		if (ret >= count)
  			goto err;
  	}

  	ret += snprintf(kbuf + ret, count - ret, "
  ");
  	if (ret >= count)
  		goto err;
  
  	if (copy_to_user(buf, kbuf, ret))
  		ret = -EFAULT;
  
  	kfree(kbuf);
  	return ret;
  
  err:
  	kfree(kbuf);
  	return -ENOMEM;
  }

  void __dump_page_owner(struct page *page)
  {
  	struct page_ext *page_ext = lookup_page_ext(page);

  	unsigned long entries[PAGE_OWNER_STACK_DEPTH];

  	struct stack_trace trace = {

  		.nr_entries = 0,
  		.entries = entries,
  		.max_entries = PAGE_OWNER_STACK_DEPTH,
  		.skip = 0

  	};

  	depot_stack_handle_t handle;

  	gfp_t gfp_mask;
  	int mt;

  	if (unlikely(!page_ext)) {
  		pr_alert("There is not page extension available.
  ");
  		return;
  	}

  	gfp_mask = page_ext->gfp_mask;
  	mt = gfpflags_to_migratetype(gfp_mask);

  	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
  		pr_alert("page_owner info is not active (free page?)
  ");
  		return;
  	}

  	handle = READ_ONCE(page_ext->handle);
  	if (!handle) {
  		pr_alert("page_owner info is not active (free page?)
  ");
  		return;
  	}
  
  	depot_fetch_stack(handle, &trace);

  	pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)
  ",
  		 page_ext->order, migratetype_names[mt], gfp_mask, &gfp_mask);

  	print_stack_trace(&trace, 0);
  
  	if (page_ext->last_migrate_reason != -1)
  		pr_alert("page has been migrated, last migrate reason: %s
  ",
  			migrate_reason_names[page_ext->last_migrate_reason]);
  }

  static ssize_t
  read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  {
  	unsigned long pfn;
  	struct page *page;
  	struct page_ext *page_ext;

  	depot_stack_handle_t handle;

  	if (!static_branch_unlikely(&page_owner_inited))

  		return -EINVAL;
  
  	page = NULL;
  	pfn = min_low_pfn + *ppos;
  
  	/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
  	while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
  		pfn++;
  
  	drain_all_pages(NULL);
  
  	/* Find an allocated page */
  	for (; pfn < max_pfn; pfn++) {
  		/*
  		 * If the new page is in a new MAX_ORDER_NR_PAGES area,
  		 * validate the area as existing, skip it if not
  		 */
  		if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
  			pfn += MAX_ORDER_NR_PAGES - 1;
  			continue;
  		}
  
  		/* Check for holes within a MAX_ORDER area */
  		if (!pfn_valid_within(pfn))
  			continue;
  
  		page = pfn_to_page(pfn);
  		if (PageBuddy(page)) {
  			unsigned long freepage_order = page_order_unsafe(page);
  
  			if (freepage_order < MAX_ORDER)
  				pfn += (1UL << freepage_order) - 1;
  			continue;
  		}
  
  		page_ext = lookup_page_ext(page);

  		if (unlikely(!page_ext))
  			continue;

  
  		/*

  		 * Some pages could be missed by concurrent allocation or free,
  		 * because we don't hold the zone lock.

  		 */
  		if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
  			continue;

  		/*
  		 * Access to page_ext->handle isn't synchronous so we should
  		 * be careful to access it.
  		 */
  		handle = READ_ONCE(page_ext->handle);
  		if (!handle)
  			continue;

  		/* Record the next PFN to read in the file offset */
  		*ppos = (pfn - min_low_pfn) + 1;

  		return print_page_owner(buf, count, pfn, page,
  				page_ext, handle);

  	}
  
  	return 0;
  }

  static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
  {
  	struct page *page;
  	struct page_ext *page_ext;
  	unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
  	unsigned long end_pfn = pfn + zone->spanned_pages;
  	unsigned long count = 0;
  
  	/* Scan block by block. First and last block may be incomplete */
  	pfn = zone->zone_start_pfn;
  
  	/*
  	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
  	 * a zone boundary, it will be double counted between zones. This does
  	 * not matter as the mixed block count will still be correct
  	 */
  	for (; pfn < end_pfn; ) {
  		if (!pfn_valid(pfn)) {
  			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
  			continue;
  		}
  
  		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
  		block_end_pfn = min(block_end_pfn, end_pfn);
  
  		page = pfn_to_page(pfn);
  
  		for (; pfn < block_end_pfn; pfn++) {
  			if (!pfn_valid_within(pfn))
  				continue;
  
  			page = pfn_to_page(pfn);

  			if (page_zone(page) != zone)
  				continue;

  			/*
  			 * We are safe to check buddy flag and order, because
  			 * this is init stage and only single thread runs.
  			 */
  			if (PageBuddy(page)) {
  				pfn += (1UL << page_order(page)) - 1;
  				continue;
  			}
  
  			if (PageReserved(page))
  				continue;
  
  			page_ext = lookup_page_ext(page);

  			if (unlikely(!page_ext))
  				continue;

  
  			/* Maybe overraping zone */
  			if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
  				continue;
  
  			/* Found early allocated page */
  			set_page_owner(page, 0, 0);
  			count++;
  		}
  	}
  
  	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages
  ",
  		pgdat->node_id, zone->name, count);
  }
  
  static void init_zones_in_node(pg_data_t *pgdat)
  {
  	struct zone *zone;
  	struct zone *node_zones = pgdat->node_zones;
  	unsigned long flags;
  
  	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
  		if (!populated_zone(zone))
  			continue;
  
  		spin_lock_irqsave(&zone->lock, flags);
  		init_pages_in_zone(pgdat, zone);
  		spin_unlock_irqrestore(&zone->lock, flags);
  	}
  }
  
  static void init_early_allocated_pages(void)
  {
  	pg_data_t *pgdat;
  
  	drain_all_pages(NULL);
  	for_each_online_pgdat(pgdat)
  		init_zones_in_node(pgdat);
  }

  static const struct file_operations proc_page_owner_operations = {
  	.read		= read_page_owner,
  };
  
  static int __init pageowner_init(void)
  {
  	struct dentry *dentry;

  	if (!static_branch_unlikely(&page_owner_inited)) {

  		pr_info("page_owner is disabled
  ");
  		return 0;
  	}
  
  	dentry = debugfs_create_file("page_owner", S_IRUSR, NULL,
  			NULL, &proc_page_owner_operations);
  	if (IS_ERR(dentry))
  		return PTR_ERR(dentry);
  
  	return 0;
  }

  late_initcall(pageowner_init)