xref: /openbmc/linux/mm/page_owner.c (revision ec5c05e5ac8bcb4a6bcd92970e15494a85400d34)
1  // SPDX-License-Identifier: GPL-2.0
2  #include <linux/debugfs.h>
3  #include <linux/mm.h>
4  #include <linux/slab.h>
5  #include <linux/uaccess.h>
6  #include <linux/memblock.h>
7  #include <linux/stacktrace.h>
8  #include <linux/page_owner.h>
9  #include <linux/jump_label.h>
10  #include <linux/migrate.h>
11  #include <linux/stackdepot.h>
12  #include <linux/seq_file.h>
13  #include <linux/memcontrol.h>
14  #include <linux/sched/clock.h>
15  
16  #include "internal.h"
17  
18  /*
19   * TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack)
20   * to use off stack temporal storage
21   */
22  #define PAGE_OWNER_STACK_DEPTH (16)
23  
24  struct page_owner {
25  	unsigned short order;
26  	short last_migrate_reason;
27  	gfp_t gfp_mask;
28  	depot_stack_handle_t handle;
29  	depot_stack_handle_t free_handle;
30  	u64 ts_nsec;
31  	u64 free_ts_nsec;
32  	char comm[TASK_COMM_LEN];
33  	pid_t pid;
34  	pid_t tgid;
35  };
36  
37  static bool page_owner_enabled __initdata;
38  DEFINE_STATIC_KEY_FALSE(page_owner_inited);
39  
40  static depot_stack_handle_t dummy_handle;
41  static depot_stack_handle_t failure_handle;
42  static depot_stack_handle_t early_handle;
43  
44  static void init_early_allocated_pages(void);
45  
46  static int __init early_page_owner_param(char *buf)
47  {
48  	int ret = kstrtobool(buf, &page_owner_enabled);
49  
50  	if (page_owner_enabled)
51  		stack_depot_want_early_init();
52  
53  	return ret;
54  }
55  early_param("page_owner", early_page_owner_param);
56  
57  static __init bool need_page_owner(void)
58  {
59  	return page_owner_enabled;
60  }
61  
62  static __always_inline depot_stack_handle_t create_dummy_stack(void)
63  {
64  	unsigned long entries[4];
65  	unsigned int nr_entries;
66  
67  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
68  	return stack_depot_save(entries, nr_entries, GFP_KERNEL);
69  }
70  
71  static noinline void register_dummy_stack(void)
72  {
73  	dummy_handle = create_dummy_stack();
74  }
75  
76  static noinline void register_failure_stack(void)
77  {
78  	failure_handle = create_dummy_stack();
79  }
80  
81  static noinline void register_early_stack(void)
82  {
83  	early_handle = create_dummy_stack();
84  }
85  
86  static __init void init_page_owner(void)
87  {
88  	if (!page_owner_enabled)
89  		return;
90  
91  	register_dummy_stack();
92  	register_failure_stack();
93  	register_early_stack();
94  	static_branch_enable(&page_owner_inited);
95  	init_early_allocated_pages();
96  }
97  
98  struct page_ext_operations page_owner_ops = {
99  	.size = sizeof(struct page_owner),
100  	.need = need_page_owner,
101  	.init = init_page_owner,
102  };
103  
104  static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
105  {
106  	return (void *)page_ext + page_owner_ops.offset;
107  }
108  
109  static noinline depot_stack_handle_t save_stack(gfp_t flags)
110  {
111  	unsigned long entries[PAGE_OWNER_STACK_DEPTH];
112  	depot_stack_handle_t handle;
113  	unsigned int nr_entries;
114  
115  	/*
116  	 * Avoid recursion.
117  	 *
118  	 * Sometimes page metadata allocation tracking requires more
119  	 * memory to be allocated:
120  	 * - when new stack trace is saved to stack depot
121  	 * - when backtrace itself is calculated (ia64)
122  	 */
123  	if (current->in_page_owner)
124  		return dummy_handle;
125  	current->in_page_owner = 1;
126  
127  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
128  	handle = stack_depot_save(entries, nr_entries, flags);
129  	if (!handle)
130  		handle = failure_handle;
131  
132  	current->in_page_owner = 0;
133  	return handle;
134  }
135  
136  void __reset_page_owner(struct page *page, unsigned short order)
137  {
138  	int i;
139  	struct page_ext *page_ext;
140  	depot_stack_handle_t handle;
141  	struct page_owner *page_owner;
142  	u64 free_ts_nsec = local_clock();
143  
144  	page_ext = page_ext_get(page);
145  	if (unlikely(!page_ext))
146  		return;
147  
148  	handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
149  	for (i = 0; i < (1 << order); i++) {
150  		__clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
151  		page_owner = get_page_owner(page_ext);
152  		page_owner->free_handle = handle;
153  		page_owner->free_ts_nsec = free_ts_nsec;
154  		page_ext = page_ext_next(page_ext);
155  	}
156  	page_ext_put(page_ext);
157  }
158  
159  static inline void __set_page_owner_handle(struct page_ext *page_ext,
160  					depot_stack_handle_t handle,
161  					unsigned short order, gfp_t gfp_mask)
162  {
163  	struct page_owner *page_owner;
164  	int i;
165  
166  	for (i = 0; i < (1 << order); i++) {
167  		page_owner = get_page_owner(page_ext);
168  		page_owner->handle = handle;
169  		page_owner->order = order;
170  		page_owner->gfp_mask = gfp_mask;
171  		page_owner->last_migrate_reason = -1;
172  		page_owner->pid = current->pid;
173  		page_owner->tgid = current->tgid;
174  		page_owner->ts_nsec = local_clock();
175  		strscpy(page_owner->comm, current->comm,
176  			sizeof(page_owner->comm));
177  		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
178  		__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
179  
180  		page_ext = page_ext_next(page_ext);
181  	}
182  }
183  
184  noinline void __set_page_owner(struct page *page, unsigned short order,
185  					gfp_t gfp_mask)
186  {
187  	struct page_ext *page_ext;
188  	depot_stack_handle_t handle;
189  
190  	handle = save_stack(gfp_mask);
191  
192  	page_ext = page_ext_get(page);
193  	if (unlikely(!page_ext))
194  		return;
195  	__set_page_owner_handle(page_ext, handle, order, gfp_mask);
196  	page_ext_put(page_ext);
197  }
198  
199  void __set_page_owner_migrate_reason(struct page *page, int reason)
200  {
201  	struct page_ext *page_ext = page_ext_get(page);
202  	struct page_owner *page_owner;
203  
204  	if (unlikely(!page_ext))
205  		return;
206  
207  	page_owner = get_page_owner(page_ext);
208  	page_owner->last_migrate_reason = reason;
209  	page_ext_put(page_ext);
210  }
211  
212  void __split_page_owner(struct page *page, unsigned int nr)
213  {
214  	int i;
215  	struct page_ext *page_ext = page_ext_get(page);
216  	struct page_owner *page_owner;
217  
218  	if (unlikely(!page_ext))
219  		return;
220  
221  	for (i = 0; i < nr; i++) {
222  		page_owner = get_page_owner(page_ext);
223  		page_owner->order = 0;
224  		page_ext = page_ext_next(page_ext);
225  	}
226  	page_ext_put(page_ext);
227  }
228  
229  void __folio_copy_owner(struct folio *newfolio, struct folio *old)
230  {
231  	struct page_ext *old_ext;
232  	struct page_ext *new_ext;
233  	struct page_owner *old_page_owner, *new_page_owner;
234  
235  	old_ext = page_ext_get(&old->page);
236  	if (unlikely(!old_ext))
237  		return;
238  
239  	new_ext = page_ext_get(&newfolio->page);
240  	if (unlikely(!new_ext)) {
241  		page_ext_put(old_ext);
242  		return;
243  	}
244  
245  	old_page_owner = get_page_owner(old_ext);
246  	new_page_owner = get_page_owner(new_ext);
247  	new_page_owner->order = old_page_owner->order;
248  	new_page_owner->gfp_mask = old_page_owner->gfp_mask;
249  	new_page_owner->last_migrate_reason =
250  		old_page_owner->last_migrate_reason;
251  	new_page_owner->handle = old_page_owner->handle;
252  	new_page_owner->pid = old_page_owner->pid;
253  	new_page_owner->tgid = old_page_owner->tgid;
254  	new_page_owner->ts_nsec = old_page_owner->ts_nsec;
255  	new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
256  	strcpy(new_page_owner->comm, old_page_owner->comm);
257  
258  	/*
259  	 * We don't clear the bit on the old folio as it's going to be freed
260  	 * after migration. Until then, the info can be useful in case of
261  	 * a bug, and the overall stats will be off a bit only temporarily.
262  	 * Also, migrate_misplaced_transhuge_page() can still fail the
263  	 * migration and then we want the old folio to retain the info. But
264  	 * in that case we also don't need to explicitly clear the info from
265  	 * the new page, which will be freed.
266  	 */
267  	__set_bit(PAGE_EXT_OWNER, &new_ext->flags);
268  	__set_bit(PAGE_EXT_OWNER_ALLOCATED, &new_ext->flags);
269  	page_ext_put(new_ext);
270  	page_ext_put(old_ext);
271  }
272  
273  void pagetypeinfo_showmixedcount_print(struct seq_file *m,
274  				       pg_data_t *pgdat, struct zone *zone)
275  {
276  	struct page *page;
277  	struct page_ext *page_ext;
278  	struct page_owner *page_owner;
279  	unsigned long pfn, block_end_pfn;
280  	unsigned long end_pfn = zone_end_pfn(zone);
281  	unsigned long count[MIGRATE_TYPES] = { 0, };
282  	int pageblock_mt, page_mt;
283  	int i;
284  
285  	/* Scan block by block. First and last block may be incomplete */
286  	pfn = zone->zone_start_pfn;
287  
288  	/*
289  	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
290  	 * a zone boundary, it will be double counted between zones. This does
291  	 * not matter as the mixed block count will still be correct
292  	 */
293  	for (; pfn < end_pfn; ) {
294  		page = pfn_to_online_page(pfn);
295  		if (!page) {
296  			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
297  			continue;
298  		}
299  
300  		block_end_pfn = pageblock_end_pfn(pfn);
301  		block_end_pfn = min(block_end_pfn, end_pfn);
302  
303  		pageblock_mt = get_pageblock_migratetype(page);
304  
305  		for (; pfn < block_end_pfn; pfn++) {
306  			/* The pageblock is online, no need to recheck. */
307  			page = pfn_to_page(pfn);
308  
309  			if (page_zone(page) != zone)
310  				continue;
311  
312  			if (PageBuddy(page)) {
313  				unsigned long freepage_order;
314  
315  				freepage_order = buddy_order_unsafe(page);
316  				if (freepage_order < MAX_ORDER)
317  					pfn += (1UL << freepage_order) - 1;
318  				continue;
319  			}
320  
321  			if (PageReserved(page))
322  				continue;
323  
324  			page_ext = page_ext_get(page);
325  			if (unlikely(!page_ext))
326  				continue;
327  
328  			if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
329  				goto ext_put_continue;
330  
331  			page_owner = get_page_owner(page_ext);
332  			page_mt = gfp_migratetype(page_owner->gfp_mask);
333  			if (pageblock_mt != page_mt) {
334  				if (is_migrate_cma(pageblock_mt))
335  					count[MIGRATE_MOVABLE]++;
336  				else
337  					count[pageblock_mt]++;
338  
339  				pfn = block_end_pfn;
340  				page_ext_put(page_ext);
341  				break;
342  			}
343  			pfn += (1UL << page_owner->order) - 1;
344  ext_put_continue:
345  			page_ext_put(page_ext);
346  		}
347  	}
348  
349  	/* Print counts */
350  	seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
351  	for (i = 0; i < MIGRATE_TYPES; i++)
352  		seq_printf(m, "%12lu ", count[i]);
353  	seq_putc(m, '\n');
354  }
355  
356  /*
357   * Looking for memcg information and print it out
358   */
359  static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret,
360  					 struct page *page)
361  {
362  #ifdef CONFIG_MEMCG
363  	unsigned long memcg_data;
364  	struct mem_cgroup *memcg;
365  	bool online;
366  	char name[80];
367  
368  	rcu_read_lock();
369  	memcg_data = READ_ONCE(page->memcg_data);
370  	if (!memcg_data)
371  		goto out_unlock;
372  
373  	if (memcg_data & MEMCG_DATA_OBJCGS)
374  		ret += scnprintf(kbuf + ret, count - ret,
375  				"Slab cache page\n");
376  
377  	memcg = page_memcg_check(page);
378  	if (!memcg)
379  		goto out_unlock;
380  
381  	online = (memcg->css.flags & CSS_ONLINE);
382  	cgroup_name(memcg->css.cgroup, name, sizeof(name));
383  	ret += scnprintf(kbuf + ret, count - ret,
384  			"Charged %sto %smemcg %s\n",
385  			PageMemcgKmem(page) ? "(via objcg) " : "",
386  			online ? "" : "offline ",
387  			name);
388  out_unlock:
389  	rcu_read_unlock();
390  #endif /* CONFIG_MEMCG */
391  
392  	return ret;
393  }
394  
395  static ssize_t
396  print_page_owner(char __user *buf, size_t count, unsigned long pfn,
397  		struct page *page, struct page_owner *page_owner,
398  		depot_stack_handle_t handle)
399  {
400  	int ret, pageblock_mt, page_mt;
401  	char *kbuf;
402  
403  	count = min_t(size_t, count, PAGE_SIZE);
404  	kbuf = kmalloc(count, GFP_KERNEL);
405  	if (!kbuf)
406  		return -ENOMEM;
407  
408  	ret = scnprintf(kbuf, count,
409  			"Page allocated via order %u, mask %#x(%pGg), pid %d, tgid %d (%s), ts %llu ns, free_ts %llu ns\n",
410  			page_owner->order, page_owner->gfp_mask,
411  			&page_owner->gfp_mask, page_owner->pid,
412  			page_owner->tgid, page_owner->comm,
413  			page_owner->ts_nsec, page_owner->free_ts_nsec);
414  
415  	/* Print information relevant to grouping pages by mobility */
416  	pageblock_mt = get_pageblock_migratetype(page);
417  	page_mt  = gfp_migratetype(page_owner->gfp_mask);
418  	ret += scnprintf(kbuf + ret, count - ret,
419  			"PFN %lu type %s Block %lu type %s Flags %pGp\n",
420  			pfn,
421  			migratetype_names[page_mt],
422  			pfn >> pageblock_order,
423  			migratetype_names[pageblock_mt],
424  			&page->flags);
425  
426  	ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
427  	if (ret >= count)
428  		goto err;
429  
430  	if (page_owner->last_migrate_reason != -1) {
431  		ret += scnprintf(kbuf + ret, count - ret,
432  			"Page has been migrated, last migrate reason: %s\n",
433  			migrate_reason_names[page_owner->last_migrate_reason]);
434  	}
435  
436  	ret = print_page_owner_memcg(kbuf, count, ret, page);
437  
438  	ret += snprintf(kbuf + ret, count - ret, "\n");
439  	if (ret >= count)
440  		goto err;
441  
442  	if (copy_to_user(buf, kbuf, ret))
443  		ret = -EFAULT;
444  
445  	kfree(kbuf);
446  	return ret;
447  
448  err:
449  	kfree(kbuf);
450  	return -ENOMEM;
451  }
452  
453  void __dump_page_owner(const struct page *page)
454  {
455  	struct page_ext *page_ext = page_ext_get((void *)page);
456  	struct page_owner *page_owner;
457  	depot_stack_handle_t handle;
458  	gfp_t gfp_mask;
459  	int mt;
460  
461  	if (unlikely(!page_ext)) {
462  		pr_alert("There is not page extension available.\n");
463  		return;
464  	}
465  
466  	page_owner = get_page_owner(page_ext);
467  	gfp_mask = page_owner->gfp_mask;
468  	mt = gfp_migratetype(gfp_mask);
469  
470  	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
471  		pr_alert("page_owner info is not present (never set?)\n");
472  		page_ext_put(page_ext);
473  		return;
474  	}
475  
476  	if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
477  		pr_alert("page_owner tracks the page as allocated\n");
478  	else
479  		pr_alert("page_owner tracks the page as freed\n");
480  
481  	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",
482  		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
483  		 page_owner->pid, page_owner->tgid, page_owner->comm,
484  		 page_owner->ts_nsec, page_owner->free_ts_nsec);
485  
486  	handle = READ_ONCE(page_owner->handle);
487  	if (!handle)
488  		pr_alert("page_owner allocation stack trace missing\n");
489  	else
490  		stack_depot_print(handle);
491  
492  	handle = READ_ONCE(page_owner->free_handle);
493  	if (!handle) {
494  		pr_alert("page_owner free stack trace missing\n");
495  	} else {
496  		pr_alert("page last free stack trace:\n");
497  		stack_depot_print(handle);
498  	}
499  
500  	if (page_owner->last_migrate_reason != -1)
501  		pr_alert("page has been migrated, last migrate reason: %s\n",
502  			migrate_reason_names[page_owner->last_migrate_reason]);
503  	page_ext_put(page_ext);
504  }
505  
506  static ssize_t
507  read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
508  {
509  	unsigned long pfn;
510  	struct page *page;
511  	struct page_ext *page_ext;
512  	struct page_owner *page_owner;
513  	depot_stack_handle_t handle;
514  
515  	if (!static_branch_unlikely(&page_owner_inited))
516  		return -EINVAL;
517  
518  	page = NULL;
519  	if (*ppos == 0)
520  		pfn = min_low_pfn;
521  	else
522  		pfn = *ppos;
523  	/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
524  	while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
525  		pfn++;
526  
527  	/* Find an allocated page */
528  	for (; pfn < max_pfn; pfn++) {
529  		/*
530  		 * This temporary page_owner is required so
531  		 * that we can avoid the context switches while holding
532  		 * the rcu lock and copying the page owner information to
533  		 * user through copy_to_user() or GFP_KERNEL allocations.
534  		 */
535  		struct page_owner page_owner_tmp;
536  
537  		/*
538  		 * If the new page is in a new MAX_ORDER_NR_PAGES area,
539  		 * validate the area as existing, skip it if not
540  		 */
541  		if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
542  			pfn += MAX_ORDER_NR_PAGES - 1;
543  			continue;
544  		}
545  
546  		page = pfn_to_page(pfn);
547  		if (PageBuddy(page)) {
548  			unsigned long freepage_order = buddy_order_unsafe(page);
549  
550  			if (freepage_order < MAX_ORDER)
551  				pfn += (1UL << freepage_order) - 1;
552  			continue;
553  		}
554  
555  		page_ext = page_ext_get(page);
556  		if (unlikely(!page_ext))
557  			continue;
558  
559  		/*
560  		 * Some pages could be missed by concurrent allocation or free,
561  		 * because we don't hold the zone lock.
562  		 */
563  		if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
564  			goto ext_put_continue;
565  
566  		/*
567  		 * Although we do have the info about past allocation of free
568  		 * pages, it's not relevant for current memory usage.
569  		 */
570  		if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
571  			goto ext_put_continue;
572  
573  		page_owner = get_page_owner(page_ext);
574  
575  		/*
576  		 * Don't print "tail" pages of high-order allocations as that
577  		 * would inflate the stats.
578  		 */
579  		if (!IS_ALIGNED(pfn, 1 << page_owner->order))
580  			goto ext_put_continue;
581  
582  		/*
583  		 * Access to page_ext->handle isn't synchronous so we should
584  		 * be careful to access it.
585  		 */
586  		handle = READ_ONCE(page_owner->handle);
587  		if (!handle)
588  			goto ext_put_continue;
589  
590  		/* Record the next PFN to read in the file offset */
591  		*ppos = pfn + 1;
592  
593  		page_owner_tmp = *page_owner;
594  		page_ext_put(page_ext);
595  		return print_page_owner(buf, count, pfn, page,
596  				&page_owner_tmp, handle);
597  ext_put_continue:
598  		page_ext_put(page_ext);
599  	}
600  
601  	return 0;
602  }
603  
604  static loff_t lseek_page_owner(struct file *file, loff_t offset, int orig)
605  {
606  	switch (orig) {
607  	case SEEK_SET:
608  		file->f_pos = offset;
609  		break;
610  	case SEEK_CUR:
611  		file->f_pos += offset;
612  		break;
613  	default:
614  		return -EINVAL;
615  	}
616  	return file->f_pos;
617  }
618  
619  static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
620  {
621  	unsigned long pfn = zone->zone_start_pfn;
622  	unsigned long end_pfn = zone_end_pfn(zone);
623  	unsigned long count = 0;
624  
625  	/*
626  	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
627  	 * a zone boundary, it will be double counted between zones. This does
628  	 * not matter as the mixed block count will still be correct
629  	 */
630  	for (; pfn < end_pfn; ) {
631  		unsigned long block_end_pfn;
632  
633  		if (!pfn_valid(pfn)) {
634  			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
635  			continue;
636  		}
637  
638  		block_end_pfn = pageblock_end_pfn(pfn);
639  		block_end_pfn = min(block_end_pfn, end_pfn);
640  
641  		for (; pfn < block_end_pfn; pfn++) {
642  			struct page *page = pfn_to_page(pfn);
643  			struct page_ext *page_ext;
644  
645  			if (page_zone(page) != zone)
646  				continue;
647  
648  			/*
649  			 * To avoid having to grab zone->lock, be a little
650  			 * careful when reading buddy page order. The only
651  			 * danger is that we skip too much and potentially miss
652  			 * some early allocated pages, which is better than
653  			 * heavy lock contention.
654  			 */
655  			if (PageBuddy(page)) {
656  				unsigned long order = buddy_order_unsafe(page);
657  
658  				if (order > 0 && order < MAX_ORDER)
659  					pfn += (1UL << order) - 1;
660  				continue;
661  			}
662  
663  			if (PageReserved(page))
664  				continue;
665  
666  			page_ext = page_ext_get(page);
667  			if (unlikely(!page_ext))
668  				continue;
669  
670  			/* Maybe overlapping zone */
671  			if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
672  				goto ext_put_continue;
673  
674  			/* Found early allocated page */
675  			__set_page_owner_handle(page_ext, early_handle,
676  						0, 0);
677  			count++;
678  ext_put_continue:
679  			page_ext_put(page_ext);
680  		}
681  		cond_resched();
682  	}
683  
684  	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
685  		pgdat->node_id, zone->name, count);
686  }
687  
688  static void init_zones_in_node(pg_data_t *pgdat)
689  {
690  	struct zone *zone;
691  	struct zone *node_zones = pgdat->node_zones;
692  
693  	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
694  		if (!populated_zone(zone))
695  			continue;
696  
697  		init_pages_in_zone(pgdat, zone);
698  	}
699  }
700  
701  static void init_early_allocated_pages(void)
702  {
703  	pg_data_t *pgdat;
704  
705  	for_each_online_pgdat(pgdat)
706  		init_zones_in_node(pgdat);
707  }
708  
709  static const struct file_operations proc_page_owner_operations = {
710  	.read		= read_page_owner,
711  	.llseek		= lseek_page_owner,
712  };
713  
714  static int __init pageowner_init(void)
715  {
716  	if (!static_branch_unlikely(&page_owner_inited)) {
717  		pr_info("page_owner is disabled\n");
718  		return 0;
719  	}
720  
721  	debugfs_create_file("page_owner", 0400, NULL, NULL,
722  			    &proc_page_owner_operations);
723  
724  	return 0;
725  }
726  late_initcall(pageowner_init)
727