xref: /openbmc/linux/mm/page_owner.c (revision 60630924bb5af8751adcecc896e7763c3783ca89)
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/sched/clock.h>
14  
15  #include "internal.h"
16  
17  /*
18   * TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack)
19   * to use off stack temporal storage
20   */
21  #define PAGE_OWNER_STACK_DEPTH (16)
22  
23  struct page_owner {
24  	unsigned short order;
25  	short last_migrate_reason;
26  	gfp_t gfp_mask;
27  	depot_stack_handle_t handle;
28  	depot_stack_handle_t free_handle;
29  	u64 ts_nsec;
30  	u64 free_ts_nsec;
31  	pid_t pid;
32  };
33  
34  static bool page_owner_enabled = false;
35  DEFINE_STATIC_KEY_FALSE(page_owner_inited);
36  
37  static depot_stack_handle_t dummy_handle;
38  static depot_stack_handle_t failure_handle;
39  static depot_stack_handle_t early_handle;
40  
41  static void init_early_allocated_pages(void);
42  
43  static int __init early_page_owner_param(char *buf)
44  {
45  	return kstrtobool(buf, &page_owner_enabled);
46  }
47  early_param("page_owner", early_page_owner_param);
48  
49  static bool need_page_owner(void)
50  {
51  	return page_owner_enabled;
52  }
53  
54  static __always_inline depot_stack_handle_t create_dummy_stack(void)
55  {
56  	unsigned long entries[4];
57  	unsigned int nr_entries;
58  
59  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
60  	return stack_depot_save(entries, nr_entries, GFP_KERNEL);
61  }
62  
63  static noinline void register_dummy_stack(void)
64  {
65  	dummy_handle = create_dummy_stack();
66  }
67  
68  static noinline void register_failure_stack(void)
69  {
70  	failure_handle = create_dummy_stack();
71  }
72  
73  static noinline void register_early_stack(void)
74  {
75  	early_handle = create_dummy_stack();
76  }
77  
78  static void init_page_owner(void)
79  {
80  	if (!page_owner_enabled)
81  		return;
82  
83  	register_dummy_stack();
84  	register_failure_stack();
85  	register_early_stack();
86  	static_branch_enable(&page_owner_inited);
87  	init_early_allocated_pages();
88  }
89  
90  struct page_ext_operations page_owner_ops = {
91  	.size = sizeof(struct page_owner),
92  	.need = need_page_owner,
93  	.init = init_page_owner,
94  };
95  
96  static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
97  {
98  	return (void *)page_ext + page_owner_ops.offset;
99  }
100  
101  static noinline depot_stack_handle_t save_stack(gfp_t flags)
102  {
103  	unsigned long entries[PAGE_OWNER_STACK_DEPTH];
104  	depot_stack_handle_t handle;
105  	unsigned int nr_entries;
106  
107  	/*
108  	 * Avoid recursion.
109  	 *
110  	 * Sometimes page metadata allocation tracking requires more
111  	 * memory to be allocated:
112  	 * - when new stack trace is saved to stack depot
113  	 * - when backtrace itself is calculated (ia64)
114  	 */
115  	if (current->in_page_owner)
116  		return dummy_handle;
117  	current->in_page_owner = 1;
118  
119  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
120  	handle = stack_depot_save(entries, nr_entries, flags);
121  	if (!handle)
122  		handle = failure_handle;
123  
124  	current->in_page_owner = 0;
125  	return handle;
126  }
127  
128  void __reset_page_owner(struct page *page, unsigned short order)
129  {
130  	int i;
131  	struct page_ext *page_ext;
132  	depot_stack_handle_t handle;
133  	struct page_owner *page_owner;
134  	u64 free_ts_nsec = local_clock();
135  
136  	page_ext = lookup_page_ext(page);
137  	if (unlikely(!page_ext))
138  		return;
139  
140  	handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
141  	for (i = 0; i < (1 << order); i++) {
142  		__clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
143  		page_owner = get_page_owner(page_ext);
144  		page_owner->free_handle = handle;
145  		page_owner->free_ts_nsec = free_ts_nsec;
146  		page_ext = page_ext_next(page_ext);
147  	}
148  }
149  
150  static inline void __set_page_owner_handle(struct page_ext *page_ext,
151  					depot_stack_handle_t handle,
152  					unsigned short order, gfp_t gfp_mask)
153  {
154  	struct page_owner *page_owner;
155  	int i;
156  
157  	for (i = 0; i < (1 << order); i++) {
158  		page_owner = get_page_owner(page_ext);
159  		page_owner->handle = handle;
160  		page_owner->order = order;
161  		page_owner->gfp_mask = gfp_mask;
162  		page_owner->last_migrate_reason = -1;
163  		page_owner->pid = current->pid;
164  		page_owner->ts_nsec = local_clock();
165  		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
166  		__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
167  
168  		page_ext = page_ext_next(page_ext);
169  	}
170  }
171  
172  noinline void __set_page_owner(struct page *page, unsigned short order,
173  					gfp_t gfp_mask)
174  {
175  	struct page_ext *page_ext = lookup_page_ext(page);
176  	depot_stack_handle_t handle;
177  
178  	if (unlikely(!page_ext))
179  		return;
180  
181  	handle = save_stack(gfp_mask);
182  	__set_page_owner_handle(page_ext, handle, order, gfp_mask);
183  }
184  
185  void __set_page_owner_migrate_reason(struct page *page, int reason)
186  {
187  	struct page_ext *page_ext = lookup_page_ext(page);
188  	struct page_owner *page_owner;
189  
190  	if (unlikely(!page_ext))
191  		return;
192  
193  	page_owner = get_page_owner(page_ext);
194  	page_owner->last_migrate_reason = reason;
195  }
196  
197  void __split_page_owner(struct page *page, unsigned int nr)
198  {
199  	int i;
200  	struct page_ext *page_ext = lookup_page_ext(page);
201  	struct page_owner *page_owner;
202  
203  	if (unlikely(!page_ext))
204  		return;
205  
206  	for (i = 0; i < nr; i++) {
207  		page_owner = get_page_owner(page_ext);
208  		page_owner->order = 0;
209  		page_ext = page_ext_next(page_ext);
210  	}
211  }
212  
213  void __folio_copy_owner(struct folio *newfolio, struct folio *old)
214  {
215  	struct page_ext *old_ext = lookup_page_ext(&old->page);
216  	struct page_ext *new_ext = lookup_page_ext(&newfolio->page);
217  	struct page_owner *old_page_owner, *new_page_owner;
218  
219  	if (unlikely(!old_ext || !new_ext))
220  		return;
221  
222  	old_page_owner = get_page_owner(old_ext);
223  	new_page_owner = get_page_owner(new_ext);
224  	new_page_owner->order = old_page_owner->order;
225  	new_page_owner->gfp_mask = old_page_owner->gfp_mask;
226  	new_page_owner->last_migrate_reason =
227  		old_page_owner->last_migrate_reason;
228  	new_page_owner->handle = old_page_owner->handle;
229  	new_page_owner->pid = old_page_owner->pid;
230  	new_page_owner->ts_nsec = old_page_owner->ts_nsec;
231  	new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
232  
233  	/*
234  	 * We don't clear the bit on the old folio as it's going to be freed
235  	 * after migration. Until then, the info can be useful in case of
236  	 * a bug, and the overall stats will be off a bit only temporarily.
237  	 * Also, migrate_misplaced_transhuge_page() can still fail the
238  	 * migration and then we want the old folio to retain the info. But
239  	 * in that case we also don't need to explicitly clear the info from
240  	 * the new page, which will be freed.
241  	 */
242  	__set_bit(PAGE_EXT_OWNER, &new_ext->flags);
243  	__set_bit(PAGE_EXT_OWNER_ALLOCATED, &new_ext->flags);
244  }
245  
246  void pagetypeinfo_showmixedcount_print(struct seq_file *m,
247  				       pg_data_t *pgdat, struct zone *zone)
248  {
249  	struct page *page;
250  	struct page_ext *page_ext;
251  	struct page_owner *page_owner;
252  	unsigned long pfn, block_end_pfn;
253  	unsigned long end_pfn = zone_end_pfn(zone);
254  	unsigned long count[MIGRATE_TYPES] = { 0, };
255  	int pageblock_mt, page_mt;
256  	int i;
257  
258  	/* Scan block by block. First and last block may be incomplete */
259  	pfn = zone->zone_start_pfn;
260  
261  	/*
262  	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
263  	 * a zone boundary, it will be double counted between zones. This does
264  	 * not matter as the mixed block count will still be correct
265  	 */
266  	for (; pfn < end_pfn; ) {
267  		page = pfn_to_online_page(pfn);
268  		if (!page) {
269  			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
270  			continue;
271  		}
272  
273  		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
274  		block_end_pfn = min(block_end_pfn, end_pfn);
275  
276  		pageblock_mt = get_pageblock_migratetype(page);
277  
278  		for (; pfn < block_end_pfn; pfn++) {
279  			/* The pageblock is online, no need to recheck. */
280  			page = pfn_to_page(pfn);
281  
282  			if (page_zone(page) != zone)
283  				continue;
284  
285  			if (PageBuddy(page)) {
286  				unsigned long freepage_order;
287  
288  				freepage_order = buddy_order_unsafe(page);
289  				if (freepage_order < MAX_ORDER)
290  					pfn += (1UL << freepage_order) - 1;
291  				continue;
292  			}
293  
294  			if (PageReserved(page))
295  				continue;
296  
297  			page_ext = lookup_page_ext(page);
298  			if (unlikely(!page_ext))
299  				continue;
300  
301  			if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
302  				continue;
303  
304  			page_owner = get_page_owner(page_ext);
305  			page_mt = gfp_migratetype(page_owner->gfp_mask);
306  			if (pageblock_mt != page_mt) {
307  				if (is_migrate_cma(pageblock_mt))
308  					count[MIGRATE_MOVABLE]++;
309  				else
310  					count[pageblock_mt]++;
311  
312  				pfn = block_end_pfn;
313  				break;
314  			}
315  			pfn += (1UL << page_owner->order) - 1;
316  		}
317  	}
318  
319  	/* Print counts */
320  	seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
321  	for (i = 0; i < MIGRATE_TYPES; i++)
322  		seq_printf(m, "%12lu ", count[i]);
323  	seq_putc(m, '\n');
324  }
325  
326  static ssize_t
327  print_page_owner(char __user *buf, size_t count, unsigned long pfn,
328  		struct page *page, struct page_owner *page_owner,
329  		depot_stack_handle_t handle)
330  {
331  	int ret, pageblock_mt, page_mt;
332  	char *kbuf;
333  
334  	count = min_t(size_t, count, PAGE_SIZE);
335  	kbuf = kmalloc(count, GFP_KERNEL);
336  	if (!kbuf)
337  		return -ENOMEM;
338  
339  	ret = snprintf(kbuf, count,
340  			"Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_ts %llu ns\n",
341  			page_owner->order, page_owner->gfp_mask,
342  			&page_owner->gfp_mask, page_owner->pid,
343  			page_owner->ts_nsec, page_owner->free_ts_nsec);
344  
345  	if (ret >= count)
346  		goto err;
347  
348  	/* Print information relevant to grouping pages by mobility */
349  	pageblock_mt = get_pageblock_migratetype(page);
350  	page_mt  = gfp_migratetype(page_owner->gfp_mask);
351  	ret += snprintf(kbuf + ret, count - ret,
352  			"PFN %lu type %s Block %lu type %s Flags %pGp\n",
353  			pfn,
354  			migratetype_names[page_mt],
355  			pfn >> pageblock_order,
356  			migratetype_names[pageblock_mt],
357  			&page->flags);
358  
359  	if (ret >= count)
360  		goto err;
361  
362  	ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
363  	if (ret >= count)
364  		goto err;
365  
366  	if (page_owner->last_migrate_reason != -1) {
367  		ret += snprintf(kbuf + ret, count - ret,
368  			"Page has been migrated, last migrate reason: %s\n",
369  			migrate_reason_names[page_owner->last_migrate_reason]);
370  		if (ret >= count)
371  			goto err;
372  	}
373  
374  	ret += snprintf(kbuf + ret, count - ret, "\n");
375  	if (ret >= count)
376  		goto err;
377  
378  	if (copy_to_user(buf, kbuf, ret))
379  		ret = -EFAULT;
380  
381  	kfree(kbuf);
382  	return ret;
383  
384  err:
385  	kfree(kbuf);
386  	return -ENOMEM;
387  }
388  
389  void __dump_page_owner(const struct page *page)
390  {
391  	struct page_ext *page_ext = lookup_page_ext(page);
392  	struct page_owner *page_owner;
393  	depot_stack_handle_t handle;
394  	gfp_t gfp_mask;
395  	int mt;
396  
397  	if (unlikely(!page_ext)) {
398  		pr_alert("There is not page extension available.\n");
399  		return;
400  	}
401  
402  	page_owner = get_page_owner(page_ext);
403  	gfp_mask = page_owner->gfp_mask;
404  	mt = gfp_migratetype(gfp_mask);
405  
406  	if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
407  		pr_alert("page_owner info is not present (never set?)\n");
408  		return;
409  	}
410  
411  	if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
412  		pr_alert("page_owner tracks the page as allocated\n");
413  	else
414  		pr_alert("page_owner tracks the page as freed\n");
415  
416  	pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, ts %llu, free_ts %llu\n",
417  		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
418  		 page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec);
419  
420  	handle = READ_ONCE(page_owner->handle);
421  	if (!handle)
422  		pr_alert("page_owner allocation stack trace missing\n");
423  	else
424  		stack_depot_print(handle);
425  
426  	handle = READ_ONCE(page_owner->free_handle);
427  	if (!handle) {
428  		pr_alert("page_owner free stack trace missing\n");
429  	} else {
430  		pr_alert("page last free stack trace:\n");
431  		stack_depot_print(handle);
432  	}
433  
434  	if (page_owner->last_migrate_reason != -1)
435  		pr_alert("page has been migrated, last migrate reason: %s\n",
436  			migrate_reason_names[page_owner->last_migrate_reason]);
437  }
438  
439  static ssize_t
440  read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
441  {
442  	unsigned long pfn;
443  	struct page *page;
444  	struct page_ext *page_ext;
445  	struct page_owner *page_owner;
446  	depot_stack_handle_t handle;
447  
448  	if (!static_branch_unlikely(&page_owner_inited))
449  		return -EINVAL;
450  
451  	page = NULL;
452  	pfn = min_low_pfn + *ppos;
453  
454  	/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
455  	while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
456  		pfn++;
457  
458  	drain_all_pages(NULL);
459  
460  	/* Find an allocated page */
461  	for (; pfn < max_pfn; pfn++) {
462  		/*
463  		 * If the new page is in a new MAX_ORDER_NR_PAGES area,
464  		 * validate the area as existing, skip it if not
465  		 */
466  		if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
467  			pfn += MAX_ORDER_NR_PAGES - 1;
468  			continue;
469  		}
470  
471  		page = pfn_to_page(pfn);
472  		if (PageBuddy(page)) {
473  			unsigned long freepage_order = buddy_order_unsafe(page);
474  
475  			if (freepage_order < MAX_ORDER)
476  				pfn += (1UL << freepage_order) - 1;
477  			continue;
478  		}
479  
480  		page_ext = lookup_page_ext(page);
481  		if (unlikely(!page_ext))
482  			continue;
483  
484  		/*
485  		 * Some pages could be missed by concurrent allocation or free,
486  		 * because we don't hold the zone lock.
487  		 */
488  		if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
489  			continue;
490  
491  		/*
492  		 * Although we do have the info about past allocation of free
493  		 * pages, it's not relevant for current memory usage.
494  		 */
495  		if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
496  			continue;
497  
498  		page_owner = get_page_owner(page_ext);
499  
500  		/*
501  		 * Don't print "tail" pages of high-order allocations as that
502  		 * would inflate the stats.
503  		 */
504  		if (!IS_ALIGNED(pfn, 1 << page_owner->order))
505  			continue;
506  
507  		/*
508  		 * Access to page_ext->handle isn't synchronous so we should
509  		 * be careful to access it.
510  		 */
511  		handle = READ_ONCE(page_owner->handle);
512  		if (!handle)
513  			continue;
514  
515  		/* Record the next PFN to read in the file offset */
516  		*ppos = (pfn - min_low_pfn) + 1;
517  
518  		return print_page_owner(buf, count, pfn, page,
519  				page_owner, handle);
520  	}
521  
522  	return 0;
523  }
524  
525  static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
526  {
527  	unsigned long pfn = zone->zone_start_pfn;
528  	unsigned long end_pfn = zone_end_pfn(zone);
529  	unsigned long count = 0;
530  
531  	/*
532  	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
533  	 * a zone boundary, it will be double counted between zones. This does
534  	 * not matter as the mixed block count will still be correct
535  	 */
536  	for (; pfn < end_pfn; ) {
537  		unsigned long block_end_pfn;
538  
539  		if (!pfn_valid(pfn)) {
540  			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
541  			continue;
542  		}
543  
544  		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
545  		block_end_pfn = min(block_end_pfn, end_pfn);
546  
547  		for (; pfn < block_end_pfn; pfn++) {
548  			struct page *page = pfn_to_page(pfn);
549  			struct page_ext *page_ext;
550  
551  			if (page_zone(page) != zone)
552  				continue;
553  
554  			/*
555  			 * To avoid having to grab zone->lock, be a little
556  			 * careful when reading buddy page order. The only
557  			 * danger is that we skip too much and potentially miss
558  			 * some early allocated pages, which is better than
559  			 * heavy lock contention.
560  			 */
561  			if (PageBuddy(page)) {
562  				unsigned long order = buddy_order_unsafe(page);
563  
564  				if (order > 0 && order < MAX_ORDER)
565  					pfn += (1UL << order) - 1;
566  				continue;
567  			}
568  
569  			if (PageReserved(page))
570  				continue;
571  
572  			page_ext = lookup_page_ext(page);
573  			if (unlikely(!page_ext))
574  				continue;
575  
576  			/* Maybe overlapping zone */
577  			if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
578  				continue;
579  
580  			/* Found early allocated page */
581  			__set_page_owner_handle(page_ext, early_handle,
582  						0, 0);
583  			count++;
584  		}
585  		cond_resched();
586  	}
587  
588  	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
589  		pgdat->node_id, zone->name, count);
590  }
591  
592  static void init_zones_in_node(pg_data_t *pgdat)
593  {
594  	struct zone *zone;
595  	struct zone *node_zones = pgdat->node_zones;
596  
597  	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
598  		if (!populated_zone(zone))
599  			continue;
600  
601  		init_pages_in_zone(pgdat, zone);
602  	}
603  }
604  
605  static void init_early_allocated_pages(void)
606  {
607  	pg_data_t *pgdat;
608  
609  	for_each_online_pgdat(pgdat)
610  		init_zones_in_node(pgdat);
611  }
612  
613  static const struct file_operations proc_page_owner_operations = {
614  	.read		= read_page_owner,
615  };
616  
617  static int __init pageowner_init(void)
618  {
619  	if (!static_branch_unlikely(&page_owner_inited)) {
620  		pr_info("page_owner is disabled\n");
621  		return 0;
622  	}
623  
624  	debugfs_create_file("page_owner", 0400, NULL, NULL,
625  			    &proc_page_owner_operations);
626  
627  	return 0;
628  }
629  late_initcall(pageowner_init)
630