// SPDX-License-Identifier: GPL-2.0

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

  #include <linux/memblock.h>

  #include <linux/stacktrace.h>
  #include <linux/page_owner.h>

  #include <linux/jump_label.h>

  #include <linux/migrate.h>

  #include <linux/stackdepot.h>

  #include <linux/seq_file.h>

  #include <linux/sched/clock.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)

  struct page_owner {

  	unsigned short order;
  	short last_migrate_reason;

  	gfp_t gfp_mask;

  	depot_stack_handle_t handle;

  	depot_stack_handle_t free_handle;

  	u64 ts_nsec;
  	pid_t pid;

  };

  static bool page_owner_enabled = false;

  DEFINE_STATIC_KEY_FALSE(page_owner_inited);

  static depot_stack_handle_t dummy_handle;
  static depot_stack_handle_t failure_handle;

  static depot_stack_handle_t early_handle;

  static void init_early_allocated_pages(void);

  static int __init early_page_owner_param(char *buf)

  {
  	if (!buf)
  		return -EINVAL;
  
  	if (strcmp(buf, "on") == 0)

  		page_owner_enabled = true;

  
  	return 0;
  }
  early_param("page_owner", early_page_owner_param);
  
  static bool need_page_owner(void)
  {

  	return page_owner_enabled;

  }

  static __always_inline depot_stack_handle_t create_dummy_stack(void)

  {
  	unsigned long entries[4];

  	unsigned int nr_entries;

  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
  	return stack_depot_save(entries, nr_entries, GFP_KERNEL);

  }

  static noinline void register_dummy_stack(void)

  {

  	dummy_handle = create_dummy_stack();
  }

  static noinline void register_failure_stack(void)
  {
  	failure_handle = create_dummy_stack();
  }

  static noinline void register_early_stack(void)
  {
  	early_handle = create_dummy_stack();

  }

  static void init_page_owner(void)
  {

  	if (!page_owner_enabled)

  		return;

  	register_dummy_stack();
  	register_failure_stack();

  	register_early_stack();

  	static_branch_enable(&page_owner_inited);

  	init_early_allocated_pages();

  }
  
  struct page_ext_operations page_owner_ops = {

  	.size = sizeof(struct page_owner),

  	.need = need_page_owner,
  	.init = init_page_owner,
  };

  struct page_owner *get_page_owner(struct page_ext *page_ext)

  {
  	return (void *)page_ext + page_owner_ops.offset;
  }

  EXPORT_SYMBOL_GPL(get_page_owner);

  static inline bool check_recursive_alloc(unsigned long *entries,
  					 unsigned int nr_entries,
  					 unsigned long ip)

  {

  	unsigned int i;

  	for (i = 0; i < nr_entries; i++) {
  		if (entries[i] == ip)

  			return true;
  	}

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

  	depot_stack_handle_t handle;

  	unsigned int nr_entries;

  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);

  
  	/*

  	 * 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
  	 * stack_depot_save_entries() 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(entries, nr_entries, _RET_IP_))

  		return dummy_handle;

  	handle = stack_depot_save(entries, nr_entries, flags);

  	if (!handle)
  		handle = failure_handle;
  
  	return handle;
  }

  void __reset_page_owner(struct page *page, unsigned int order)
  {
  	int i;
  	struct page_ext *page_ext;

  	depot_stack_handle_t handle = 0;
  	struct page_owner *page_owner;

  	handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);

  	page_ext = lookup_page_ext(page);
  	if (unlikely(!page_ext))
  		return;

  	for (i = 0; i < (1 << order); i++) {

  		__clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);

  		page_owner = get_page_owner(page_ext);
  		page_owner->free_handle = handle;

  		page_ext = page_ext_next(page_ext);

  	}
  }

  static inline void __set_page_owner_handle(struct page *page,
  	struct page_ext *page_ext, depot_stack_handle_t handle,
  	unsigned int order, gfp_t gfp_mask)

  {

  	struct page_owner *page_owner;

  	int i;

  	for (i = 0; i < (1 << order); i++) {
  		page_owner = get_page_owner(page_ext);
  		page_owner->handle = handle;
  		page_owner->order = order;
  		page_owner->gfp_mask = gfp_mask;
  		page_owner->last_migrate_reason = -1;

  		page_owner->pid = current->pid;
  		page_owner->ts_nsec = local_clock();

  		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);

  		__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);

  		page_ext = page_ext_next(page_ext);

  	}

  }

  noinline void __set_page_owner(struct page *page, unsigned int order,
  					gfp_t gfp_mask)
  {
  	struct page_ext *page_ext = lookup_page_ext(page);
  	depot_stack_handle_t handle;
  
  	if (unlikely(!page_ext))
  		return;
  
  	handle = save_stack(gfp_mask);

  	__set_page_owner_handle(page, page_ext, handle, order, gfp_mask);

  }

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

  	struct page_owner *page_owner;

  	if (unlikely(!page_ext))
  		return;

  	page_owner = get_page_owner(page_ext);
  	page_owner->last_migrate_reason = reason;

  }

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

  {

  	int i;

  	struct page_ext *page_ext = lookup_page_ext(page);

  	struct page_owner *page_owner;

  	if (unlikely(!page_ext))

  		return;

  	for (i = 0; i < nr; i++) {

  		page_owner = get_page_owner(page_ext);
  		page_owner->order = 0;

  		page_ext = page_ext_next(page_ext);

  	}

  }

  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);

  	struct page_owner *old_page_owner, *new_page_owner;

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

  	old_page_owner = get_page_owner(old_ext);
  	new_page_owner = get_page_owner(new_ext);
  	new_page_owner->order = old_page_owner->order;
  	new_page_owner->gfp_mask = old_page_owner->gfp_mask;
  	new_page_owner->last_migrate_reason =
  		old_page_owner->last_migrate_reason;
  	new_page_owner->handle = old_page_owner->handle;

  	new_page_owner->pid = old_page_owner->pid;
  	new_page_owner->ts_nsec = old_page_owner->ts_nsec;

  
  	/*
  	 * 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);

  	__set_bit(PAGE_EXT_OWNER_ALLOCATED, &new_ext->flags);

  }

  void pagetypeinfo_showmixedcount_print(struct seq_file *m,
  				       pg_data_t *pgdat, struct zone *zone)
  {
  	struct page *page;
  	struct page_ext *page_ext;

  	struct page_owner *page_owner;

  	unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
  	unsigned long end_pfn = pfn + zone->spanned_pages;
  	unsigned long count[MIGRATE_TYPES] = { 0, };
  	int pageblock_mt, page_mt;
  	int i;
  
  	/* 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; ) {

  		page = pfn_to_online_page(pfn);
  		if (!page) {

  			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);

  		pageblock_mt = get_pageblock_migratetype(page);
  
  		for (; pfn < block_end_pfn; pfn++) {
  			if (!pfn_valid_within(pfn))
  				continue;

  			/* The pageblock is online, no need to recheck. */

  			page = pfn_to_page(pfn);
  
  			if (page_zone(page) != zone)
  				continue;
  
  			if (PageBuddy(page)) {

  				unsigned long freepage_order;

  				freepage_order = buddy_order_unsafe(page);

  				if (freepage_order < MAX_ORDER)
  					pfn += (1UL << freepage_order) - 1;

  				continue;
  			}
  
  			if (PageReserved(page))
  				continue;
  
  			page_ext = lookup_page_ext(page);
  			if (unlikely(!page_ext))
  				continue;

  			if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))

  				continue;

  			page_owner = get_page_owner(page_ext);

  			page_mt = gfp_migratetype(page_owner->gfp_mask);

  			if (pageblock_mt != page_mt) {
  				if (is_migrate_cma(pageblock_mt))
  					count[MIGRATE_MOVABLE]++;
  				else
  					count[pageblock_mt]++;
  
  				pfn = block_end_pfn;
  				break;
  			}

  			pfn += (1UL << page_owner->order) - 1;

  		}
  	}
  
  	/* Print counts */
  	seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
  	for (i = 0; i < MIGRATE_TYPES; i++)
  		seq_printf(m, "%12lu ", count[i]);
  	seq_putc(m, '
  ');
  }

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

  		struct page *page, struct page_owner *page_owner,

  		depot_stack_handle_t handle)

  {

  	int ret, pageblock_mt, page_mt;
  	unsigned long *entries;
  	unsigned int nr_entries;

  	char *kbuf;

  	count = min_t(size_t, count, PAGE_SIZE);

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

  			"Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns
  ",

  			page_owner->order, page_owner->gfp_mask,

  			&page_owner->gfp_mask, page_owner->pid,
  			page_owner->ts_nsec);

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

  	pageblock_mt = get_pageblock_migratetype(page);

  	page_mt  = gfp_migratetype(page_owner->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;

  	nr_entries = stack_depot_fetch(handle, &entries);
  	ret += stack_trace_snprint(kbuf + ret, count - ret, entries, nr_entries, 0);

  	if (ret >= count)
  		goto err;

  	if (page_owner->last_migrate_reason != -1) {

  		ret += snprintf(kbuf + ret, count - ret,
  			"Page has been migrated, last migrate reason: %s
  ",

  			migrate_reason_names[page_owner->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);

  	struct page_owner *page_owner;

  	depot_stack_handle_t handle;

  	unsigned long *entries;
  	unsigned int nr_entries;

  	gfp_t gfp_mask;
  	int mt;

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

  
  	page_owner = get_page_owner(page_ext);
  	gfp_mask = page_owner->gfp_mask;

  	mt = gfp_migratetype(gfp_mask);

  	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {

  		pr_alert("page_owner info is not present (never set?)
  ");

  		return;
  	}

  	if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))

  		pr_alert("page_owner tracks the page as allocated
  ");
  	else
  		pr_alert("page_owner tracks the page as freed
  ");

  	pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, ts %llu
  ",
  		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
  		 page_owner->pid, page_owner->ts_nsec);

  	handle = READ_ONCE(page_owner->handle);

  	if (!handle) {

  		pr_alert("page_owner allocation stack trace missing
  ");
  	} else {
  		nr_entries = stack_depot_fetch(handle, &entries);
  		stack_trace_print(entries, nr_entries, 0);

  	}

  	handle = READ_ONCE(page_owner->free_handle);
  	if (!handle) {
  		pr_alert("page_owner free stack trace missing
  ");
  	} else {
  		nr_entries = stack_depot_fetch(handle, &entries);
  		pr_alert("page last free stack trace:
  ");
  		stack_trace_print(entries, nr_entries, 0);
  	}

  	if (page_owner->last_migrate_reason != -1)

  		pr_alert("page has been migrated, last migrate reason: %s
  ",

  			migrate_reason_names[page_owner->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;

  	struct page_owner *page_owner;

  	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 = buddy_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;

  		/*
  		 * Although we do have the info about past allocation of free
  		 * pages, it's not relevant for current memory usage.
  		 */

  		if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))

  			continue;

  		page_owner = get_page_owner(page_ext);

  		/*

  		 * Don't print "tail" pages of high-order allocations as that
  		 * would inflate the stats.
  		 */
  		if (!IS_ALIGNED(pfn, 1 << page_owner->order))
  			continue;
  
  		/*

  		 * Access to page_ext->handle isn't synchronous so we should
  		 * be careful to access it.
  		 */

  		handle = READ_ONCE(page_owner->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_owner, handle);

  	}
  
  	return 0;
  }

  static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
  {

  	unsigned long pfn = zone->zone_start_pfn;
  	unsigned long end_pfn = zone_end_pfn(zone);

  	unsigned long count = 0;

  	/*
  	 * 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; ) {

  		unsigned long block_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);

  		for (; pfn < block_end_pfn; pfn++) {

  			struct page *page;
  			struct page_ext *page_ext;

  			if (!pfn_valid_within(pfn))
  				continue;
  
  			page = pfn_to_page(pfn);

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

  			/*

  			 * To avoid having to grab zone->lock, be a little
  			 * careful when reading buddy page order. The only
  			 * danger is that we skip too much and potentially miss
  			 * some early allocated pages, which is better than
  			 * heavy lock contention.

  			 */
  			if (PageBuddy(page)) {

  				unsigned long order = buddy_order_unsafe(page);

  
  				if (order > 0 && order < MAX_ORDER)
  					pfn += (1UL << order) - 1;

  				continue;
  			}
  
  			if (PageReserved(page))
  				continue;
  
  			page_ext = lookup_page_ext(page);

  			if (unlikely(!page_ext))
  				continue;

  			/* Maybe overlapping zone */

  			if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
  				continue;
  
  			/* Found early allocated page */

  			__set_page_owner_handle(page, page_ext, early_handle,
  						0, 0);

  			count++;
  		}

  		cond_resched();

  	}
  
  	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;

  
  	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
  		if (!populated_zone(zone))
  			continue;

  		init_pages_in_zone(pgdat, zone);

  	}
  }
  
  static void init_early_allocated_pages(void)
  {
  	pg_data_t *pgdat;

  	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)
  {

  	if (!static_branch_unlikely(&page_owner_inited)) {

  		pr_info("page_owner is disabled
  ");
  		return 0;
  	}

  	debugfs_create_file("page_owner", 0400, NULL, NULL,
  			    &proc_page_owner_operations);

  	return 0;

  }

  late_initcall(pageowner_init)