[deliverable/linux.git] / mm / page_owner.c

#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 "internal.h"

static bool page_owner_disabled = true;
DEFINE_STATIC_KEY_FALSE(page_owner_inited);

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;

	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);
		__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;
	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);

	page_ext->last_migrate_reason = reason;
}

gfp_t __get_page_owner_gfp(struct page *page)
{
	struct page_ext *page_ext = lookup_page_ext(page);

	return page_ext->gfp_mask;
}

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);
	int i;

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

	for (i = 0; i < ARRAY_SIZE(new_ext->trace_entries); i++)
		new_ext->trace_entries[i] = old_ext->trace_entries[i];

	/*
	 * 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)
{
	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 %#x(%pGg)\n",
			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_pfnblock_migratetype(page, pfn);
	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)\n",
			pfn,
			migratetype_names[page_mt],
			pfn >> pageblock_order,
			migratetype_names[pageblock_mt],
			page->flags, &page->flags);

	if (ret >= count)
		goto err;

	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\n",
			migrate_reason_names[page_ext->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 stack_trace trace = {
		.nr_entries = page_ext->nr_entries,
		.entries = &page_ext->trace_entries[0],
	};
	gfp_t gfp_mask = page_ext->gfp_mask;
	int 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;
	}

	pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
		 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\n",
			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;

	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);

		/*
		 * 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\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;
	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\n");
		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)
Commit	Line	Data
48c96a36 JK	1	#include <linux/debugfs.h>
	2	#include <linux/mm.h>
	3	#include <linux/slab.h>
	4	#include <linux/uaccess.h>
	5	#include <linux/bootmem.h>
	6	#include <linux/stacktrace.h>
	7	#include <linux/page_owner.h>
7dd80b8a	8	#include <linux/jump_label.h>
7cd12b4a	9	#include <linux/migrate.h>
48c96a36 JK	10	#include "internal.h"
	11
	12	static bool page_owner_disabled = true;
7dd80b8a	13	DEFINE_STATIC_KEY_FALSE(page_owner_inited);
48c96a36	14
61cf5feb JK	15	static void init_early_allocated_pages(void);
61cf5feb JK	16
48c96a36 JK	17	static int early_page_owner_param(char *buf)
	18	{
	19	if (!buf)
	20	return -EINVAL;
	21
	22	if (strcmp(buf, "on") == 0)
	23	page_owner_disabled = false;
	24
	25	return 0;
	26	}
	27	early_param("page_owner", early_page_owner_param);
	28
	29	static bool need_page_owner(void)
	30	{
	31	if (page_owner_disabled)
	32	return false;
	33
	34	return true;
	35	}
	36
	37	static void init_page_owner(void)
	38	{
	39	if (page_owner_disabled)
	40	return;
	41
7dd80b8a	42	static_branch_enable(&page_owner_inited);
61cf5feb	43	init_early_allocated_pages();
48c96a36 JK	44	}
	45
	46	struct page_ext_operations page_owner_ops = {
	47	.need = need_page_owner,
	48	.init = init_page_owner,
	49	};
	50
	51	void __reset_page_owner(struct page *page, unsigned int order)
	52	{
	53	int i;
	54	struct page_ext *page_ext;
	55
	56	for (i = 0; i < (1 << order); i++) {
	57	page_ext = lookup_page_ext(page + i);
	58	__clear_bit(PAGE_EXT_OWNER, &page_ext->flags);
	59	}
	60	}
	61
	62	void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
	63	{
94f759d6 SR	64	struct page_ext *page_ext = lookup_page_ext(page);
	65	struct stack_trace trace = {
	66	.nr_entries = 0,
	67	.max_entries = ARRAY_SIZE(page_ext->trace_entries),
	68	.entries = &page_ext->trace_entries[0],
	69	.skip = 3,
	70	};
48c96a36	71
94f759d6	72	save_stack_trace(&trace);
48c96a36 JK	73
	74	page_ext->order = order;
	75	page_ext->gfp_mask = gfp_mask;
94f759d6	76	page_ext->nr_entries = trace.nr_entries;
7cd12b4a	77	page_ext->last_migrate_reason = -1;
48c96a36 JK	78
	79	__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
	80	}
	81
7cd12b4a VB	82	void __set_page_owner_migrate_reason(struct page *page, int reason)
	83	{
	84	struct page_ext *page_ext = lookup_page_ext(page);
	85
	86	page_ext->last_migrate_reason = reason;
	87	}
	88
e2cfc911 JK	89	gfp_t __get_page_owner_gfp(struct page *page)
	90	{
	91	struct page_ext *page_ext = lookup_page_ext(page);
	92
	93	return page_ext->gfp_mask;
	94	}
	95
d435edca VB	96	void __copy_page_owner(struct page oldpage, struct page newpage)
	97	{
	98	struct page_ext *old_ext = lookup_page_ext(oldpage);
	99	struct page_ext *new_ext = lookup_page_ext(newpage);
	100	int i;
	101
	102	new_ext->order = old_ext->order;
	103	new_ext->gfp_mask = old_ext->gfp_mask;
	104	new_ext->nr_entries = old_ext->nr_entries;
	105
	106	for (i = 0; i < ARRAY_SIZE(new_ext->trace_entries); i++)
	107	new_ext->trace_entries[i] = old_ext->trace_entries[i];
	108
	109	/*
	110	* We don't clear the bit on the oldpage as it's going to be freed
	111	* after migration. Until then, the info can be useful in case of
	112	* a bug, and the overal stats will be off a bit only temporarily.
	113	* Also, migrate_misplaced_transhuge_page() can still fail the
	114	* migration and then we want the oldpage to retain the info. But
	115	* in that case we also don't need to explicitly clear the info from
	116	* the new page, which will be freed.
	117	*/
	118	__set_bit(PAGE_EXT_OWNER, &new_ext->flags);
	119	}
	120
48c96a36 JK	121	static ssize_t
	122	print_page_owner(char __user *buf, size_t count, unsigned long pfn,
	123	struct page page, struct page_ext page_ext)
	124	{
	125	int ret;
	126	int pageblock_mt, page_mt;
	127	char *kbuf;
94f759d6 SR	128	struct stack_trace trace = {
	129	.nr_entries = page_ext->nr_entries,
	130	.entries = &page_ext->trace_entries[0],
	131	};
48c96a36 JK	132
	133	kbuf = kmalloc(count, GFP_KERNEL);
	134	if (!kbuf)
	135	return -ENOMEM;
	136
	137	ret = snprintf(kbuf, count,
60f30350 VB	138	"Page allocated via order %u, mask %#x(%pGg)\n",
	139	page_ext->order, page_ext->gfp_mask,
	140	&page_ext->gfp_mask);
48c96a36 JK	141
	142	if (ret >= count)
	143	goto err;
	144
	145	/* Print information relevant to grouping pages by mobility */
	146	pageblock_mt = get_pfnblock_migratetype(page, pfn);
	147	page_mt = gfpflags_to_migratetype(page_ext->gfp_mask);
	148	ret += snprintf(kbuf + ret, count - ret,
60f30350	149	"PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",
48c96a36	150	pfn,
60f30350	151	migratetype_names[page_mt],
48c96a36	152	pfn >> pageblock_order,
60f30350 VB	153	migratetype_names[pageblock_mt],
60f30350 VB	154	page->flags, &page->flags);
48c96a36 JK	155
	156	if (ret >= count)
	157	goto err;
	158
94f759d6	159	ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0);
48c96a36 JK	160	if (ret >= count)
	161	goto err;
	162
7cd12b4a VB	163	if (page_ext->last_migrate_reason != -1) {
	164	ret += snprintf(kbuf + ret, count - ret,
	165	"Page has been migrated, last migrate reason: %s\n",
	166	migrate_reason_names[page_ext->last_migrate_reason]);
	167	if (ret >= count)
	168	goto err;
	169	}
	170
48c96a36 JK	171	ret += snprintf(kbuf + ret, count - ret, "\n");
	172	if (ret >= count)
	173	goto err;
	174
	175	if (copy_to_user(buf, kbuf, ret))
	176	ret = -EFAULT;
	177
	178	kfree(kbuf);
	179	return ret;
	180
	181	err:
	182	kfree(kbuf);
	183	return -ENOMEM;
	184	}
	185
4e462112 VB	186	void __dump_page_owner(struct page *page)
	187	{
	188	struct page_ext *page_ext = lookup_page_ext(page);
	189	struct stack_trace trace = {
	190	.nr_entries = page_ext->nr_entries,
	191	.entries = &page_ext->trace_entries[0],
	192	};
	193	gfp_t gfp_mask = page_ext->gfp_mask;
	194	int mt = gfpflags_to_migratetype(gfp_mask);
	195
	196	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
	197	pr_alert("page_owner info is not active (free page?)\n");
	198	return;
	199	}
	200
756a025f JP	201	pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
756a025f JP	202	page_ext->order, migratetype_names[mt], gfp_mask, &gfp_mask);
4e462112 VB	203	print_stack_trace(&trace, 0);
	204
	205	if (page_ext->last_migrate_reason != -1)
	206	pr_alert("page has been migrated, last migrate reason: %s\n",
	207	migrate_reason_names[page_ext->last_migrate_reason]);
	208	}
	209
48c96a36 JK	210	static ssize_t
	211	read_page_owner(struct file file, char __user buf, size_t count, loff_t *ppos)
	212	{
	213	unsigned long pfn;
	214	struct page *page;
	215	struct page_ext *page_ext;
	216
7dd80b8a	217	if (!static_branch_unlikely(&page_owner_inited))
48c96a36 JK	218	return -EINVAL;
	219
	220	page = NULL;
	221	pfn = min_low_pfn + *ppos;
	222
	223	/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
	224	while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
	225	pfn++;
	226
	227	drain_all_pages(NULL);
	228
	229	/* Find an allocated page */
	230	for (; pfn < max_pfn; pfn++) {
	231	/*
	232	* If the new page is in a new MAX_ORDER_NR_PAGES area,
	233	* validate the area as existing, skip it if not
	234	*/
	235	if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
	236	pfn += MAX_ORDER_NR_PAGES - 1;
	237	continue;
	238	}
	239
	240	/* Check for holes within a MAX_ORDER area */
	241	if (!pfn_valid_within(pfn))
	242	continue;
	243
	244	page = pfn_to_page(pfn);
	245	if (PageBuddy(page)) {
	246	unsigned long freepage_order = page_order_unsafe(page);
	247
	248	if (freepage_order < MAX_ORDER)
	249	pfn += (1UL << freepage_order) - 1;
	250	continue;
	251	}
	252
	253	page_ext = lookup_page_ext(page);
	254
	255	/*
61cf5feb JK	256	* Some pages could be missed by concurrent allocation or free,
61cf5feb JK	257	* because we don't hold the zone lock.
48c96a36 JK	258	*/
	259	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
	260	continue;
	261
	262	/* Record the next PFN to read in the file offset */
	263	*ppos = (pfn - min_low_pfn) + 1;
	264
	265	return print_page_owner(buf, count, pfn, page, page_ext);
	266	}
	267
	268	return 0;
	269	}
	270
61cf5feb JK	271	static void init_pages_in_zone(pg_data_t pgdat, struct zone zone)
	272	{
	273	struct page *page;
	274	struct page_ext *page_ext;
	275	unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
	276	unsigned long end_pfn = pfn + zone->spanned_pages;
	277	unsigned long count = 0;
	278
	279	/* Scan block by block. First and last block may be incomplete */
	280	pfn = zone->zone_start_pfn;
	281
	282	/*
	283	* Walk the zone in pageblock_nr_pages steps. If a page block spans
	284	* a zone boundary, it will be double counted between zones. This does
	285	* not matter as the mixed block count will still be correct
	286	*/
	287	for (; pfn < end_pfn; ) {
	288	if (!pfn_valid(pfn)) {
	289	pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
	290	continue;
	291	}
	292
	293	block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
	294	block_end_pfn = min(block_end_pfn, end_pfn);
	295
	296	page = pfn_to_page(pfn);
	297
	298	for (; pfn < block_end_pfn; pfn++) {
	299	if (!pfn_valid_within(pfn))
	300	continue;
	301
	302	page = pfn_to_page(pfn);
	303
	304	/*
	305	* We are safe to check buddy flag and order, because
	306	* this is init stage and only single thread runs.
	307	*/
	308	if (PageBuddy(page)) {
	309	pfn += (1UL << page_order(page)) - 1;
	310	continue;
	311	}
	312
	313	if (PageReserved(page))
	314	continue;
	315
	316	page_ext = lookup_page_ext(page);
	317
	318	/* Maybe overraping zone */
	319	if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
	320	continue;
	321
	322	/* Found early allocated page */
	323	set_page_owner(page, 0, 0);
	324	count++;
	325	}
	326	}
	327
	328	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
	329	pgdat->node_id, zone->name, count);
	330	}
	331
	332	static void init_zones_in_node(pg_data_t *pgdat)
	333	{
	334	struct zone *zone;
335	struct zone *node_zones = pgdat->node_zones;
336	unsigned long flags;
337
338	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
339	if (!populated_zone(zone))
340	continue;
341
342	spin_lock_irqsave(&zone->lock, flags);
343	init_pages_in_zone(pgdat, zone);
344	spin_unlock_irqrestore(&zone->lock, flags);
345	}
346	}
347
348	static void init_early_allocated_pages(void)
349	{
350	pg_data_t *pgdat;
351
352	drain_all_pages(NULL);
353	for_each_online_pgdat(pgdat)
354	init_zones_in_node(pgdat);
355	}
356
48c96a36 JK	357	static const struct file_operations proc_page_owner_operations = {
	358	.read = read_page_owner,
	359	};
	360
	361	static int __init pageowner_init(void)
	362	{
	363	struct dentry *dentry;
	364
7dd80b8a	365	if (!static_branch_unlikely(&page_owner_inited)) {
48c96a36 JK	366	pr_info("page_owner is disabled\n");
	367	return 0;
	368	}
	369
	370	dentry = debugfs_create_file("page_owner", S_IRUSR, NULL,
	371	NULL, &proc_page_owner_operations);
	372	if (IS_ERR(dentry))
	373	return PTR_ERR(dentry);
	374
	375	return 0;
	376	}
44c5af96	377	late_initcall(pageowner_init)