mm/page_owner.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 #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 <linux/seq_file.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;
 };

 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 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_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 __always_inline depot_stack_handle_t create_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);
 	return depot_save_stack(&dummy, 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_disabled)
 		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,
 };

 static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
 {
 	return (void *)page_ext + page_owner_ops.offset;
 }

 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;

 	if (!trace->nr_entries)
 		return false;

 	for (i = 0; i < trace->nr_entries; i++) {
 		if (trace->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];
 	struct stack_trace trace = {
 		.nr_entries = 0,
 		.entries = entries,
 		.max_entries = PAGE_OWNER_STACK_DEPTH,
 		.skip = 2
 	};
 	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;
 }

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

 	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;

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

 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_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 order)
 {
 	int i;
 	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->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);
 	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;

 	/*
 	 * 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);
 }

 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; ) {
 		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);
 		pageblock_mt = get_pageblock_migratetype(page);

 		for (; pfn < block_end_pfn; pfn++) {
 			if (!pfn_valid_within(pfn))
 				continue;

 			page = pfn_to_page(pfn);

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

 			if (PageBuddy(page)) {
 				unsigned long freepage_order;

 				freepage_order = page_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, &page_ext->flags))
 				continue;

 			page_owner = get_page_owner(page_ext);
 			page_mt = gfpflags_to_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, '\n');
 }

 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;
 	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)\n",
 			page_owner->order, page_owner->gfp_mask,
 			&page_owner->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_owner->gfp_mask);
 	ret += snprintf(kbuf + ret, count - ret,
 			"PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",
 			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_owner->last_migrate_reason != -1) {
 		ret += snprintf(kbuf + ret, count - ret,
 			"Page has been migrated, last migrate reason: %s\n",
 			migrate_reason_names[page_owner->last_migrate_reason]);
 		if (ret >= count)
 			goto err;
 	}

 	ret += snprintf(kbuf + ret, count - ret, "\n");
 	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;
 	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.\n");
 		return;
 	}

 	page_owner = get_page_owner(page_ext);
 	gfp_mask = page_owner->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?)\n");
 		return;
 	}

 	handle = READ_ONCE(page_owner->handle);
 	if (!handle) {
 		pr_alert("page_owner info is not active (free page?)\n");
 		return;
 	}

 	depot_fetch_stack(handle, &trace);
 	pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
 		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask);
 	print_stack_trace(&trace, 0);

 	if (page_owner->last_migrate_reason != -1)
 		pr_alert("page has been migrated, last migrate reason: %s\n",
 			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 = 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;

 		page_owner = get_page_owner(page_ext);

 		/*
 		 * 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 = page_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_ext, early_handle, 0, 0);
 			count++;
 		}
 		cond_resched();
 	}

 	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
 		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)
 {
 	struct dentry *dentry;

 	if (!static_branch_unlikely(&page_owner_inited)) {
 		pr_info("page_owner is disabled\n");
 		return 0;
 	}

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

 	return PTR_ERR_OR_ZERO(dentry);
 }
 late_initcall(pageowner_init)
	// SPDX-License-Identifier: GPL-2.0
	#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 <linux/seq_file.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;
	};

	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 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_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 __always_inline depot_stack_handle_t create_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);
	return depot_save_stack(&dummy, 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_disabled)
	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,
	};

	static inline struct page_owner get_page_owner(struct page_ext page_ext)
	{
	return (void *)page_ext + page_owner_ops.offset;
	}

	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;

	if (!trace->nr_entries)
	return false;

	for (i = 0; i < trace->nr_entries; i++) {
	if (trace->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];
	struct stack_trace trace = {
	.nr_entries = 0,
	.entries = entries,
	.max_entries = PAGE_OWNER_STACK_DEPTH,
	.skip = 2
	};
	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;
	}

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

	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;

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

	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_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 order)
	{
	int i;
	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->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);
	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;

	/*
	* 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);
	}

	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; ) {
	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);
	pageblock_mt = get_pageblock_migratetype(page);

	for (; pfn < block_end_pfn; pfn++) {
	if (!pfn_valid_within(pfn))
	continue;

	page = pfn_to_page(pfn);

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

	if (PageBuddy(page)) {
	unsigned long freepage_order;

	freepage_order = page_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, &page_ext->flags))
	continue;

	page_owner = get_page_owner(page_ext);
	page_mt = gfpflags_to_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, '\n');
	}

	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;
	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)\n",
	page_owner->order, page_owner->gfp_mask,
	&page_owner->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_owner->gfp_mask);
	ret += snprintf(kbuf + ret, count - ret,
	"PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",
	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_owner->last_migrate_reason != -1) {
	ret += snprintf(kbuf + ret, count - ret,
	"Page has been migrated, last migrate reason: %s\n",
	migrate_reason_names[page_owner->last_migrate_reason]);
	if (ret >= count)
	goto err;
	}

	ret += snprintf(kbuf + ret, count - ret, "\n");
	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;
	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.\n");
	return;
	}

	page_owner = get_page_owner(page_ext);
	gfp_mask = page_owner->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?)\n");
	return;
	}

	handle = READ_ONCE(page_owner->handle);
	if (!handle) {
	pr_alert("page_owner info is not active (free page?)\n");
	return;
	}

	depot_fetch_stack(handle, &trace);
	pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
	page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask);
	print_stack_trace(&trace, 0);

	if (page_owner->last_migrate_reason != -1)
	pr_alert("page has been migrated, last migrate reason: %s\n",
	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 = 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;

	page_owner = get_page_owner(page_ext);

	/*
	* 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 = page_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_ext, early_handle, 0, 0);
	count++;
	}
	cond_resched();
	}

	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
	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)
	{
	struct dentry *dentry;

	if (!static_branch_unlikely(&page_owner_inited)) {
	pr_info("page_owner is disabled\n");
	return 0;
	}

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

	return PTR_ERR_OR_ZERO(dentry);
	}
	late_initcall(pageowner_init)