#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 "internal.h"
  
  static bool page_owner_disabled = true;
  bool page_owner_inited __read_mostly;
  
  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 void init_page_owner(void)
  {
  	if (page_owner_disabled)
  		return;
  
  	page_owner_inited = true;
  	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);
  		__clear_bit(PAGE_EXT_OWNER, &page_ext->flags);
  	}
  }
  
  void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
  {
  	struct page_ext *page_ext = lookup_page_ext(page);
  	struct stack_trace trace = {
  		.nr_entries = 0,
  		.max_entries = ARRAY_SIZE(page_ext->trace_entries),
  		.entries = &page_ext->trace_entries[0],
  		.skip = 3,
  	};
  
  	save_stack_trace(&trace);
  
  	page_ext->order = order;
  	page_ext->gfp_mask = gfp_mask;
  	page_ext->nr_entries = trace.nr_entries;
  
  	__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
  }
  
  gfp_t __get_page_owner_gfp(struct page *page)
  {
  	struct page_ext *page_ext = lookup_page_ext(page);
  
  	return page_ext->gfp_mask;
  }
  
  static ssize_t
  print_page_owner(char __user *buf, size_t count, unsigned long pfn,
  		struct page *page, struct page_ext *page_ext)
  {
  	int ret;
  	int pageblock_mt, page_mt;
  	char *kbuf;
  	struct stack_trace trace = {
  		.nr_entries = page_ext->nr_entries,
  		.entries = &page_ext->trace_entries[0],
  	};
  
  	kbuf = kmalloc(count, GFP_KERNEL);
  	if (!kbuf)
  		return -ENOMEM;
  
  	ret = snprintf(kbuf, count,
  			"Page allocated via order %u, mask 0x%x
  ",
  			page_ext->order, page_ext->gfp_mask);
  
  	if (ret >= count)
  		goto err;
  
  	/* Print information relevant to grouping pages by mobility */
  	pageblock_mt = get_pfnblock_migratetype(page, pfn);
  	page_mt  = gfpflags_to_migratetype(page_ext->gfp_mask);
  	ret += snprintf(kbuf + ret, count - ret,
  			"PFN %lu Block %lu type %d %s Flags %s%s%s%s%s%s%s%s%s%s%s%s
  ",
  			pfn,
  			pfn >> pageblock_order,
  			pageblock_mt,
  			pageblock_mt != page_mt ? "Fallback" : "        ",
  			PageLocked(page)	? "K" : " ",
  			PageError(page)		? "E" : " ",
  			PageReferenced(page)	? "R" : " ",
  			PageUptodate(page)	? "U" : " ",
  			PageDirty(page)		? "D" : " ",
  			PageLRU(page)		? "L" : " ",
  			PageActive(page)	? "A" : " ",
  			PageSlab(page)		? "S" : " ",
  			PageWriteback(page)	? "W" : " ",
  			PageCompound(page)	? "C" : " ",
  			PageSwapCache(page)	? "B" : " ",
  			PageMappedToDisk(page)	? "M" : " ");
  
  	if (ret >= count)
  		goto err;
  
  	ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0);
  	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;
  }
  
  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;
  
  	if (!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);
  
  		/*
  		 * 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;
  
  		/* 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);
  	}
  
  	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);
  
  			/*
  			 * 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);
  
  			/* 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 (!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)