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/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/memcontrol.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;
 	u64 free_ts_nsec;
 	char comm[TASK_COMM_LEN];
 	pid_t pid;
 	pid_t tgid;
 };

 static bool page_owner_enabled __initdata;
 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)
 {
 	int ret = kstrtobool(buf, &page_owner_enabled);

 	if (page_owner_enabled)
 		stack_depot_want_early_init();

 	return ret;
 }
 early_param("page_owner", early_page_owner_param);

 static __init 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 __init 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,
 };

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

 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;

 	/*
 	 * Avoid recursion.
 	 *
 	 * Sometimes page metadata allocation tracking requires more
 	 * memory to be allocated:
 	 * - when new stack trace is saved to stack depot
 	 * - when backtrace itself is calculated (ia64)
 	 */
 	if (current->in_page_owner)
 		return dummy_handle;
 	current->in_page_owner = 1;

 	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
 	handle = stack_depot_save(entries, nr_entries, flags);
 	if (!handle)
 		handle = failure_handle;

 	current->in_page_owner = 0;
 	return handle;
 }

 void __reset_page_owner(struct page *page, unsigned short order)
 {
 	int i;
 	struct page_ext *page_ext;
 	depot_stack_handle_t handle;
 	struct page_owner *page_owner;
 	u64 free_ts_nsec = local_clock();

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

 	handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
 	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_owner->free_ts_nsec = free_ts_nsec;
 		page_ext = page_ext_next(page_ext);
 	}
 }

 static inline void __set_page_owner_handle(struct page_ext *page_ext,
 					depot_stack_handle_t handle,
 					unsigned short 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->tgid = current->tgid;
 		page_owner->ts_nsec = local_clock();
 		strscpy(page_owner->comm, current->comm,
 			sizeof(page_owner->comm));
 		__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 short 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 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 __folio_copy_owner(struct folio *newfolio, struct folio *old)
 {
 	struct page_ext *old_ext = lookup_page_ext(&old->page);
 	struct page_ext *new_ext = lookup_page_ext(&newfolio->page);
 	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->tgid = old_page_owner->tgid;
 	new_page_owner->ts_nsec = old_page_owner->ts_nsec;
 	new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
 	strcpy(new_page_owner->comm, old_page_owner->comm);

 	/*
 	 * We don't clear the bit on the old folio as it's going to be freed
 	 * after migration. Until then, the info can be useful in case of
 	 * a bug, and the overall stats will be off a bit only temporarily.
 	 * Also, migrate_misplaced_transhuge_page() can still fail the
 	 * migration and then we want the old folio 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, block_end_pfn;
 	unsigned long end_pfn = zone_end_pfn(zone);
 	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++) {
 			/* 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, '\n');
 }

 /*
  * Looking for memcg information and print it out
  */
 static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret,
 					 struct page *page)
 {
 #ifdef CONFIG_MEMCG
 	unsigned long memcg_data;
 	struct mem_cgroup *memcg;
 	bool online;
 	char name[80];

 	rcu_read_lock();
 	memcg_data = READ_ONCE(page->memcg_data);
 	if (!memcg_data)
 		goto out_unlock;

 	if (memcg_data & MEMCG_DATA_OBJCGS)
 		ret += scnprintf(kbuf + ret, count - ret,
 				"Slab cache page\n");

 	memcg = page_memcg_check(page);
 	if (!memcg)
 		goto out_unlock;

 	online = (memcg->css.flags & CSS_ONLINE);
 	cgroup_name(memcg->css.cgroup, name, sizeof(name));
 	ret += scnprintf(kbuf + ret, count - ret,
 			"Charged %sto %smemcg %s\n",
 			PageMemcgKmem(page) ? "(via objcg) " : "",
 			online ? "" : "offline ",
 			name);
 out_unlock:
 	rcu_read_unlock();
 #endif /* CONFIG_MEMCG */

 	return ret;
 }

 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;
 	char *kbuf;

 	count = min_t(size_t, count, PAGE_SIZE);
 	kbuf = kmalloc(count, GFP_KERNEL);
 	if (!kbuf)
 		return -ENOMEM;

 	ret = scnprintf(kbuf, count,
 			"Page allocated via order %u, mask %#x(%pGg), pid %d, tgid %d (%s), ts %llu ns, free_ts %llu ns\n",
 			page_owner->order, page_owner->gfp_mask,
 			&page_owner->gfp_mask, page_owner->pid,
 			page_owner->tgid, page_owner->comm,
 			page_owner->ts_nsec, page_owner->free_ts_nsec);

 	/* Print information relevant to grouping pages by mobility */
 	pageblock_mt = get_pageblock_migratetype(page);
 	page_mt  = gfp_migratetype(page_owner->gfp_mask);
 	ret += scnprintf(kbuf + ret, count - ret,
 			"PFN %lu type %s Block %lu type %s Flags %pGp\n",
 			pfn,
 			migratetype_names[page_mt],
 			pfn >> pageblock_order,
 			migratetype_names[pageblock_mt],
 			&page->flags);

 	ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
 	if (ret >= count)
 		goto err;

 	if (page_owner->last_migrate_reason != -1) {
 		ret += scnprintf(kbuf + ret, count - ret,
 			"Page has been migrated, last migrate reason: %s\n",
 			migrate_reason_names[page_owner->last_migrate_reason]);
 	}

 	ret = print_page_owner_memcg(kbuf, count, ret, page);

 	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(const struct page *page)
 {
 	struct page_ext *page_ext = lookup_page_ext(page);
 	struct page_owner *page_owner;
 	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 = gfp_migratetype(gfp_mask);

 	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
 		pr_alert("page_owner info is not present (never set?)\n");
 		return;
 	}

 	if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
 		pr_alert("page_owner tracks the page as allocated\n");
 	else
 		pr_alert("page_owner tracks the page as freed\n");

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

 	handle = READ_ONCE(page_owner->handle);
 	if (!handle)
 		pr_alert("page_owner allocation stack trace missing\n");
 	else
 		stack_depot_print(handle);

 	handle = READ_ONCE(page_owner->free_handle);
 	if (!handle) {
 		pr_alert("page_owner free stack trace missing\n");
 	} else {
 		pr_alert("page last free stack trace:\n");
 		stack_depot_print(handle);
 	}

 	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;
 		}

 		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 = pfn_to_page(pfn);
 			struct page_ext *page_ext;

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

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

 	return 0;
 }
 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/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/memcontrol.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;
	u64 free_ts_nsec;
	char comm[TASK_COMM_LEN];
	pid_t pid;
	pid_t tgid;
	};

	static bool page_owner_enabled __initdata;
	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)
	{
	int ret = kstrtobool(buf, &page_owner_enabled);

	if (page_owner_enabled)
	stack_depot_want_early_init();

	return ret;
	}
	early_param("page_owner", early_page_owner_param);

	static __init 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 __init 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,
	};

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

	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;

	/*
	* Avoid recursion.
	*
	* Sometimes page metadata allocation tracking requires more
	* memory to be allocated:
	* - when new stack trace is saved to stack depot
	* - when backtrace itself is calculated (ia64)
	*/
	if (current->in_page_owner)
	return dummy_handle;
	current->in_page_owner = 1;

	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
	handle = stack_depot_save(entries, nr_entries, flags);
	if (!handle)
	handle = failure_handle;

	current->in_page_owner = 0;
	return handle;
	}

	void __reset_page_owner(struct page *page, unsigned short order)
	{
	int i;
	struct page_ext *page_ext;
	depot_stack_handle_t handle;
	struct page_owner *page_owner;
	u64 free_ts_nsec = local_clock();

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

	handle = save_stack(GFP_NOWAIT \| __GFP_NOWARN);
	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_owner->free_ts_nsec = free_ts_nsec;
	page_ext = page_ext_next(page_ext);
	}
	}

	static inline void __set_page_owner_handle(struct page_ext *page_ext,
	depot_stack_handle_t handle,
	unsigned short 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->tgid = current->tgid;
	page_owner->ts_nsec = local_clock();
	strscpy(page_owner->comm, current->comm,
	sizeof(page_owner->comm));
	__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 short 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 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 __folio_copy_owner(struct folio newfolio, struct folio old)
	{
	struct page_ext *old_ext = lookup_page_ext(&old->page);
	struct page_ext *new_ext = lookup_page_ext(&newfolio->page);
	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->tgid = old_page_owner->tgid;
	new_page_owner->ts_nsec = old_page_owner->ts_nsec;
	new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
	strcpy(new_page_owner->comm, old_page_owner->comm);

	/*
	* We don't clear the bit on the old folio as it's going to be freed
	* after migration. Until then, the info can be useful in case of
	* a bug, and the overall stats will be off a bit only temporarily.
	* Also, migrate_misplaced_transhuge_page() can still fail the
	* migration and then we want the old folio 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, block_end_pfn;
	unsigned long end_pfn = zone_end_pfn(zone);
	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++) {
	/* 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, '\n');
	}

	/*
	* Looking for memcg information and print it out
	*/
	static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret,
	struct page *page)
	{
	#ifdef CONFIG_MEMCG
	unsigned long memcg_data;
	struct mem_cgroup *memcg;
	bool online;
	char name[80];

	rcu_read_lock();
	memcg_data = READ_ONCE(page->memcg_data);
	if (!memcg_data)
	goto out_unlock;

	if (memcg_data & MEMCG_DATA_OBJCGS)
	ret += scnprintf(kbuf + ret, count - ret,
	"Slab cache page\n");

	memcg = page_memcg_check(page);
	if (!memcg)
	goto out_unlock;

	online = (memcg->css.flags & CSS_ONLINE);
	cgroup_name(memcg->css.cgroup, name, sizeof(name));
	ret += scnprintf(kbuf + ret, count - ret,
	"Charged %sto %smemcg %s\n",
	PageMemcgKmem(page) ? "(via objcg) " : "",
	online ? "" : "offline ",
	name);
	out_unlock:
	rcu_read_unlock();
	#endif /* CONFIG_MEMCG */

	return ret;
	}

	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;
	char *kbuf;

	count = min_t(size_t, count, PAGE_SIZE);
	kbuf = kmalloc(count, GFP_KERNEL);
	if (!kbuf)
	return -ENOMEM;

	ret = scnprintf(kbuf, count,
	"Page allocated via order %u, mask %#x(%pGg), pid %d, tgid %d (%s), ts %llu ns, free_ts %llu ns\n",
	page_owner->order, page_owner->gfp_mask,
	&page_owner->gfp_mask, page_owner->pid,
	page_owner->tgid, page_owner->comm,
	page_owner->ts_nsec, page_owner->free_ts_nsec);

	/* Print information relevant to grouping pages by mobility */
	pageblock_mt = get_pageblock_migratetype(page);
	page_mt = gfp_migratetype(page_owner->gfp_mask);
	ret += scnprintf(kbuf + ret, count - ret,
	"PFN %lu type %s Block %lu type %s Flags %pGp\n",
	pfn,
	migratetype_names[page_mt],
	pfn >> pageblock_order,
	migratetype_names[pageblock_mt],
	&page->flags);

	ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
	if (ret >= count)
	goto err;

	if (page_owner->last_migrate_reason != -1) {
	ret += scnprintf(kbuf + ret, count - ret,
	"Page has been migrated, last migrate reason: %s\n",
	migrate_reason_names[page_owner->last_migrate_reason]);
	}

	ret = print_page_owner_memcg(kbuf, count, ret, page);

	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(const struct page *page)
	{
	struct page_ext *page_ext = lookup_page_ext(page);
	struct page_owner *page_owner;
	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 = gfp_migratetype(gfp_mask);

	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
	pr_alert("page_owner info is not present (never set?)\n");
	return;
	}

	if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
	pr_alert("page_owner tracks the page as allocated\n");
	else
	pr_alert("page_owner tracks the page as freed\n");

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

	handle = READ_ONCE(page_owner->handle);
	if (!handle)
	pr_alert("page_owner allocation stack trace missing\n");
	else
	stack_depot_print(handle);

	handle = READ_ONCE(page_owner->free_handle);
	if (!handle) {
	pr_alert("page_owner free stack trace missing\n");
	} else {
	pr_alert("page last free stack trace:\n");
	stack_depot_print(handle);
	}

	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;
	}

	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 = pfn_to_page(pfn);
	struct page_ext *page_ext;

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

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

	return 0;
	}
	late_initcall(pageowner_init)