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
24struct 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 pid_t free_pid;
36 pid_t free_tgid;
37};
38
39struct stack {
40 struct stack_record *stack_record;
41 struct stack *next;
42};
43static struct stack dummy_stack;
44static struct stack failure_stack;
45static struct stack *stack_list;
46static DEFINE_SPINLOCK(stack_list_lock);
47
48static bool page_owner_enabled __initdata;
49DEFINE_STATIC_KEY_FALSE(page_owner_inited);
50
51static depot_stack_handle_t dummy_handle;
52static depot_stack_handle_t failure_handle;
53static depot_stack_handle_t early_handle;
54
55static void init_early_allocated_pages(void);
56
57static inline void set_current_in_page_owner(void)
58{
59 /*
60 * Avoid recursion.
61 *
62 * We might need to allocate more memory from page_owner code, so make
63 * sure to signal it in order to avoid recursion.
64 */
65 current->in_page_owner = 1;
66}
67
68static inline void unset_current_in_page_owner(void)
69{
70 current->in_page_owner = 0;
71}
72
73static int __init early_page_owner_param(char *buf)
74{
75 int ret = kstrtobool(s: buf, res: &page_owner_enabled);
76
77 if (page_owner_enabled)
78 stack_depot_request_early_init();
79
80 return ret;
81}
82early_param("page_owner", early_page_owner_param);
83
84static __init bool need_page_owner(void)
85{
86 return page_owner_enabled;
87}
88
89static __always_inline depot_stack_handle_t create_dummy_stack(void)
90{
91 unsigned long entries[4];
92 unsigned int nr_entries;
93
94 nr_entries = stack_trace_save(store: entries, ARRAY_SIZE(entries), skipnr: 0);
95 return stack_depot_save(entries, nr_entries, GFP_KERNEL);
96}
97
98static noinline void register_dummy_stack(void)
99{
100 dummy_handle = create_dummy_stack();
101}
102
103static noinline void register_failure_stack(void)
104{
105 failure_handle = create_dummy_stack();
106}
107
108static noinline void register_early_stack(void)
109{
110 early_handle = create_dummy_stack();
111}
112
113static __init void init_page_owner(void)
114{
115 if (!page_owner_enabled)
116 return;
117
118 register_dummy_stack();
119 register_failure_stack();
120 register_early_stack();
121 init_early_allocated_pages();
122 /* Initialize dummy and failure stacks and link them to stack_list */
123 dummy_stack.stack_record = __stack_depot_get_stack_record(handle: dummy_handle);
124 failure_stack.stack_record = __stack_depot_get_stack_record(handle: failure_handle);
125 if (dummy_stack.stack_record)
126 refcount_set(r: &dummy_stack.stack_record->count, n: 1);
127 if (failure_stack.stack_record)
128 refcount_set(r: &failure_stack.stack_record->count, n: 1);
129 dummy_stack.next = &failure_stack;
130 stack_list = &dummy_stack;
131 static_branch_enable(&page_owner_inited);
132}
133
134struct page_ext_operations page_owner_ops = {
135 .size = sizeof(struct page_owner),
136 .need = need_page_owner,
137 .init = init_page_owner,
138 .need_shared_flags = true,
139};
140
141static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
142{
143 return page_ext_data(page_ext, ops: &page_owner_ops);
144}
145
146static noinline depot_stack_handle_t save_stack(gfp_t flags)
147{
148 unsigned long entries[PAGE_OWNER_STACK_DEPTH];
149 depot_stack_handle_t handle;
150 unsigned int nr_entries;
151
152 if (current->in_page_owner)
153 return dummy_handle;
154
155 set_current_in_page_owner();
156 nr_entries = stack_trace_save(store: entries, ARRAY_SIZE(entries), skipnr: 2);
157 handle = stack_depot_save(entries, nr_entries, alloc_flags: flags);
158 if (!handle)
159 handle = failure_handle;
160 unset_current_in_page_owner();
161
162 return handle;
163}
164
165static void add_stack_record_to_list(struct stack_record *stack_record,
166 gfp_t gfp_mask)
167{
168 unsigned long flags;
169 struct stack *stack;
170
171 set_current_in_page_owner();
172 stack = kmalloc(sizeof(*stack), gfp_nested_mask(gfp_mask));
173 if (!stack) {
174 unset_current_in_page_owner();
175 return;
176 }
177 unset_current_in_page_owner();
178
179 stack->stack_record = stack_record;
180 stack->next = NULL;
181
182 spin_lock_irqsave(&stack_list_lock, flags);
183 stack->next = stack_list;
184 /*
185 * This pairs with smp_load_acquire() from function
186 * stack_start(). This guarantees that stack_start()
187 * will see an updated stack_list before starting to
188 * traverse the list.
189 */
190 smp_store_release(&stack_list, stack);
191 spin_unlock_irqrestore(lock: &stack_list_lock, flags);
192}
193
194static void inc_stack_record_count(depot_stack_handle_t handle, gfp_t gfp_mask,
195 int nr_base_pages)
196{
197 struct stack_record *stack_record = __stack_depot_get_stack_record(handle);
198
199 if (!stack_record)
200 return;
201
202 /*
203 * New stack_record's that do not use STACK_DEPOT_FLAG_GET start
204 * with REFCOUNT_SATURATED to catch spurious increments of their
205 * refcount.
206 * Since we do not use STACK_DEPOT_FLAG_GET API, let us
207 * set a refcount of 1 ourselves.
208 */
209 if (refcount_read(r: &stack_record->count) == REFCOUNT_SATURATED) {
210 int old = REFCOUNT_SATURATED;
211
212 if (atomic_try_cmpxchg_relaxed(v: &stack_record->count.refs, old: &old, new: 1))
213 /* Add the new stack_record to our list */
214 add_stack_record_to_list(stack_record, gfp_mask);
215 }
216 refcount_add(i: nr_base_pages, r: &stack_record->count);
217}
218
219static void dec_stack_record_count(depot_stack_handle_t handle,
220 int nr_base_pages)
221{
222 struct stack_record *stack_record = __stack_depot_get_stack_record(handle);
223
224 if (!stack_record)
225 return;
226
227 if (refcount_sub_and_test(i: nr_base_pages, r: &stack_record->count))
228 pr_warn("%s: refcount went to 0 for %u handle\n", __func__,
229 handle);
230}
231
232static inline void __update_page_owner_handle(struct page *page,
233 depot_stack_handle_t handle,
234 unsigned short order,
235 gfp_t gfp_mask,
236 short last_migrate_reason, u64 ts_nsec,
237 pid_t pid, pid_t tgid, char *comm)
238{
239 struct page_ext_iter iter;
240 struct page_ext *page_ext;
241 struct page_owner *page_owner;
242
243 rcu_read_lock();
244 for_each_page_ext(page, 1 << order, page_ext, iter) {
245 page_owner = get_page_owner(page_ext);
246 page_owner->handle = handle;
247 page_owner->order = order;
248 page_owner->gfp_mask = gfp_mask;
249 page_owner->last_migrate_reason = last_migrate_reason;
250 page_owner->pid = pid;
251 page_owner->tgid = tgid;
252 page_owner->ts_nsec = ts_nsec;
253 strscpy(page_owner->comm, comm,
254 sizeof(page_owner->comm));
255 __set_bit(PAGE_EXT_OWNER, &page_ext->flags);
256 __set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
257 }
258 rcu_read_unlock();
259}
260
261static inline void __update_page_owner_free_handle(struct page *page,
262 depot_stack_handle_t handle,
263 unsigned short order,
264 pid_t pid, pid_t tgid,
265 u64 free_ts_nsec)
266{
267 struct page_ext_iter iter;
268 struct page_ext *page_ext;
269 struct page_owner *page_owner;
270
271 rcu_read_lock();
272 for_each_page_ext(page, 1 << order, page_ext, iter) {
273 page_owner = get_page_owner(page_ext);
274 /* Only __reset_page_owner() wants to clear the bit */
275 if (handle) {
276 __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
277 page_owner->free_handle = handle;
278 }
279 page_owner->free_ts_nsec = free_ts_nsec;
280 page_owner->free_pid = current->pid;
281 page_owner->free_tgid = current->tgid;
282 }
283 rcu_read_unlock();
284}
285
286void __reset_page_owner(struct page *page, unsigned short order)
287{
288 struct page_ext *page_ext;
289 depot_stack_handle_t handle;
290 depot_stack_handle_t alloc_handle;
291 struct page_owner *page_owner;
292 u64 free_ts_nsec = local_clock();
293
294 page_ext = page_ext_get(page);
295 if (unlikely(!page_ext))
296 return;
297
298 page_owner = get_page_owner(page_ext);
299 alloc_handle = page_owner->handle;
300 page_ext_put(page_ext);
301
302 /*
303 * Do not specify GFP_NOWAIT to make gfpflags_allow_spinning() == false
304 * to prevent issues in stack_depot_save().
305 * This is similar to alloc_pages_nolock() gfp flags, but only used
306 * to signal stack_depot to avoid spin_locks.
307 */
308 handle = save_stack(__GFP_NOWARN);
309 __update_page_owner_free_handle(page, handle, order, current->pid,
310 current->tgid, free_ts_nsec);
311
312 if (alloc_handle != early_handle)
313 /*
314 * early_handle is being set as a handle for all those
315 * early allocated pages. See init_pages_in_zone().
316 * Since their refcount is not being incremented because
317 * the machinery is not ready yet, we cannot decrement
318 * their refcount either.
319 */
320 dec_stack_record_count(handle: alloc_handle, nr_base_pages: 1 << order);
321}
322
323noinline void __set_page_owner(struct page *page, unsigned short order,
324 gfp_t gfp_mask)
325{
326 u64 ts_nsec = local_clock();
327 depot_stack_handle_t handle;
328
329 handle = save_stack(flags: gfp_mask);
330 __update_page_owner_handle(page, handle, order, gfp_mask, last_migrate_reason: -1,
331 ts_nsec, current->pid, current->tgid,
332 current->comm);
333 inc_stack_record_count(handle, gfp_mask, nr_base_pages: 1 << order);
334}
335
336void __set_page_owner_migrate_reason(struct page *page, int reason)
337{
338 struct page_ext *page_ext = page_ext_get(page);
339 struct page_owner *page_owner;
340
341 if (unlikely(!page_ext))
342 return;
343
344 page_owner = get_page_owner(page_ext);
345 page_owner->last_migrate_reason = reason;
346 page_ext_put(page_ext);
347}
348
349void __split_page_owner(struct page *page, int old_order, int new_order)
350{
351 struct page_ext_iter iter;
352 struct page_ext *page_ext;
353 struct page_owner *page_owner;
354
355 rcu_read_lock();
356 for_each_page_ext(page, 1 << old_order, page_ext, iter) {
357 page_owner = get_page_owner(page_ext);
358 page_owner->order = new_order;
359 }
360 rcu_read_unlock();
361}
362
363void __folio_copy_owner(struct folio *newfolio, struct folio *old)
364{
365 struct page_ext *page_ext;
366 struct page_ext_iter iter;
367 struct page_owner *old_page_owner;
368 struct page_owner *new_page_owner;
369 depot_stack_handle_t migrate_handle;
370
371 page_ext = page_ext_get(page: &old->page);
372 if (unlikely(!page_ext))
373 return;
374
375 old_page_owner = get_page_owner(page_ext);
376 page_ext_put(page_ext);
377
378 page_ext = page_ext_get(page: &newfolio->page);
379 if (unlikely(!page_ext))
380 return;
381
382 new_page_owner = get_page_owner(page_ext);
383 page_ext_put(page_ext);
384
385 migrate_handle = new_page_owner->handle;
386 __update_page_owner_handle(page: &newfolio->page, handle: old_page_owner->handle,
387 order: old_page_owner->order, gfp_mask: old_page_owner->gfp_mask,
388 last_migrate_reason: old_page_owner->last_migrate_reason,
389 ts_nsec: old_page_owner->ts_nsec, pid: old_page_owner->pid,
390 tgid: old_page_owner->tgid, comm: old_page_owner->comm);
391 /*
392 * Do not proactively clear PAGE_EXT_OWNER{_ALLOCATED} bits as the folio
393 * will be freed after migration. Keep them until then as they may be
394 * useful.
395 */
396 __update_page_owner_free_handle(page: &newfolio->page, handle: 0, order: old_page_owner->order,
397 pid: old_page_owner->free_pid,
398 tgid: old_page_owner->free_tgid,
399 free_ts_nsec: old_page_owner->free_ts_nsec);
400 /*
401 * We linked the original stack to the new folio, we need to do the same
402 * for the new one and the old folio otherwise there will be an imbalance
403 * when subtracting those pages from the stack.
404 */
405 rcu_read_lock();
406 for_each_page_ext(&old->page, 1 << new_page_owner->order, page_ext, iter) {
407 old_page_owner = get_page_owner(page_ext);
408 old_page_owner->handle = migrate_handle;
409 }
410 rcu_read_unlock();
411}
412
413void pagetypeinfo_showmixedcount_print(struct seq_file *m,
414 pg_data_t *pgdat, struct zone *zone)
415{
416 struct page *page;
417 struct page_ext *page_ext;
418 struct page_owner *page_owner;
419 unsigned long pfn, block_end_pfn;
420 unsigned long end_pfn = zone_end_pfn(zone);
421 unsigned long count[MIGRATE_TYPES] = { 0, };
422 int pageblock_mt, page_mt;
423 int i;
424
425 /* Scan block by block. First and last block may be incomplete */
426 pfn = zone->zone_start_pfn;
427
428 /*
429 * Walk the zone in pageblock_nr_pages steps. If a page block spans
430 * a zone boundary, it will be double counted between zones. This does
431 * not matter as the mixed block count will still be correct
432 */
433 for (; pfn < end_pfn; ) {
434 page = pfn_to_online_page(pfn);
435 if (!page) {
436 pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
437 continue;
438 }
439
440 block_end_pfn = pageblock_end_pfn(pfn);
441 block_end_pfn = min(block_end_pfn, end_pfn);
442
443 pageblock_mt = get_pageblock_migratetype(page);
444
445 for (; pfn < block_end_pfn; pfn++) {
446 /* The pageblock is online, no need to recheck. */
447 page = pfn_to_page(pfn);
448
449 if (page_zone(page) != zone)
450 continue;
451
452 if (PageBuddy(page)) {
453 unsigned long freepage_order;
454
455 freepage_order = buddy_order_unsafe(page);
456 if (freepage_order <= MAX_PAGE_ORDER)
457 pfn += (1UL << freepage_order) - 1;
458 continue;
459 }
460
461 if (PageReserved(page))
462 continue;
463
464 page_ext = page_ext_get(page);
465 if (unlikely(!page_ext))
466 continue;
467
468 if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
469 goto ext_put_continue;
470
471 page_owner = get_page_owner(page_ext);
472 page_mt = gfp_migratetype(gfp_flags: page_owner->gfp_mask);
473 if (pageblock_mt != page_mt) {
474 if (is_migrate_cma(pageblock_mt))
475 count[MIGRATE_MOVABLE]++;
476 else
477 count[pageblock_mt]++;
478
479 pfn = block_end_pfn;
480 page_ext_put(page_ext);
481 break;
482 }
483 pfn += (1UL << page_owner->order) - 1;
484ext_put_continue:
485 page_ext_put(page_ext);
486 }
487 }
488
489 /* Print counts */
490 seq_printf(m, fmt: "Node %d, zone %8s ", pgdat->node_id, zone->name);
491 for (i = 0; i < MIGRATE_TYPES; i++)
492 seq_printf(m, fmt: "%12lu ", count[i]);
493 seq_putc(m, c: '\n');
494}
495
496/*
497 * Looking for memcg information and print it out
498 */
499static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret,
500 struct page *page)
501{
502#ifdef CONFIG_MEMCG
503 unsigned long memcg_data;
504 struct mem_cgroup *memcg;
505 bool online;
506 char name[80];
507
508 rcu_read_lock();
509 memcg_data = READ_ONCE(page->memcg_data);
510 if (!memcg_data || PageTail(page))
511 goto out_unlock;
512
513 if (memcg_data & MEMCG_DATA_OBJEXTS)
514 ret += scnprintf(buf: kbuf + ret, size: count - ret,
515 fmt: "Slab cache page\n");
516
517 memcg = page_memcg_check(page);
518 if (!memcg)
519 goto out_unlock;
520
521 online = (memcg->css.flags & CSS_ONLINE);
522 cgroup_name(cgrp: memcg->css.cgroup, buf: name, buflen: sizeof(name));
523 ret += scnprintf(buf: kbuf + ret, size: count - ret,
524 fmt: "Charged %sto %smemcg %s\n",
525 PageMemcgKmem(page) ? "(via objcg) " : "",
526 online ? "" : "offline ",
527 name);
528out_unlock:
529 rcu_read_unlock();
530#endif /* CONFIG_MEMCG */
531
532 return ret;
533}
534
535static ssize_t
536print_page_owner(char __user *buf, size_t count, unsigned long pfn,
537 struct page *page, struct page_owner *page_owner,
538 depot_stack_handle_t handle)
539{
540 int ret, pageblock_mt, page_mt;
541 char *kbuf;
542
543 count = min_t(size_t, count, PAGE_SIZE);
544 kbuf = kmalloc(count, GFP_KERNEL);
545 if (!kbuf)
546 return -ENOMEM;
547
548 ret = scnprintf(buf: kbuf, size: count,
549 fmt: "Page allocated via order %u, mask %#x(%pGg), pid %d, tgid %d (%s), ts %llu ns\n",
550 page_owner->order, page_owner->gfp_mask,
551 &page_owner->gfp_mask, page_owner->pid,
552 page_owner->tgid, page_owner->comm,
553 page_owner->ts_nsec);
554
555 /* Print information relevant to grouping pages by mobility */
556 pageblock_mt = get_pageblock_migratetype(page);
557 page_mt = gfp_migratetype(gfp_flags: page_owner->gfp_mask);
558 ret += scnprintf(buf: kbuf + ret, size: count - ret,
559 fmt: "PFN 0x%lx type %s Block %lu type %s Flags %pGp\n",
560 pfn,
561 migratetype_names[page_mt],
562 pfn >> pageblock_order,
563 migratetype_names[pageblock_mt],
564 &page->flags);
565
566 ret += stack_depot_snprint(handle, buf: kbuf + ret, size: count - ret, spaces: 0);
567 if (ret >= count)
568 goto err;
569
570 if (page_owner->last_migrate_reason != -1) {
571 ret += scnprintf(buf: kbuf + ret, size: count - ret,
572 fmt: "Page has been migrated, last migrate reason: %s\n",
573 migrate_reason_names[page_owner->last_migrate_reason]);
574 }
575
576 ret = print_page_owner_memcg(kbuf, count, ret, page);
577
578 ret += snprintf(buf: kbuf + ret, size: count - ret, fmt: "\n");
579 if (ret >= count)
580 goto err;
581
582 if (copy_to_user(to: buf, from: kbuf, n: ret))
583 ret = -EFAULT;
584
585 kfree(objp: kbuf);
586 return ret;
587
588err:
589 kfree(objp: kbuf);
590 return -ENOMEM;
591}
592
593void __dump_page_owner(const struct page *page)
594{
595 struct page_ext *page_ext = page_ext_get(page: (void *)page);
596 struct page_owner *page_owner;
597 depot_stack_handle_t handle;
598 gfp_t gfp_mask;
599 int mt;
600
601 if (unlikely(!page_ext)) {
602 pr_alert("There is not page extension available.\n");
603 return;
604 }
605
606 page_owner = get_page_owner(page_ext);
607 gfp_mask = page_owner->gfp_mask;
608 mt = gfp_migratetype(gfp_flags: gfp_mask);
609
610 if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
611 pr_alert("page_owner info is not present (never set?)\n");
612 page_ext_put(page_ext);
613 return;
614 }
615
616 if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
617 pr_alert("page_owner tracks the page as allocated\n");
618 else
619 pr_alert("page_owner tracks the page as freed\n");
620
621 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",
622 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
623 page_owner->pid, page_owner->tgid, page_owner->comm,
624 page_owner->ts_nsec, page_owner->free_ts_nsec);
625
626 handle = READ_ONCE(page_owner->handle);
627 if (!handle)
628 pr_alert("page_owner allocation stack trace missing\n");
629 else
630 stack_depot_print(stack: handle);
631
632 handle = READ_ONCE(page_owner->free_handle);
633 if (!handle) {
634 pr_alert("page_owner free stack trace missing\n");
635 } else {
636 pr_alert("page last free pid %d tgid %d stack trace:\n",
637 page_owner->free_pid, page_owner->free_tgid);
638 stack_depot_print(stack: handle);
639 }
640
641 if (page_owner->last_migrate_reason != -1)
642 pr_alert("page has been migrated, last migrate reason: %s\n",
643 migrate_reason_names[page_owner->last_migrate_reason]);
644 page_ext_put(page_ext);
645}
646
647static ssize_t
648read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
649{
650 unsigned long pfn;
651 struct page *page;
652 struct page_ext *page_ext;
653 struct page_owner *page_owner;
654 depot_stack_handle_t handle;
655
656 if (!static_branch_unlikely(&page_owner_inited))
657 return -EINVAL;
658
659 page = NULL;
660 if (*ppos == 0)
661 pfn = min_low_pfn;
662 else
663 pfn = *ppos;
664 /* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
665 while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
666 pfn++;
667
668 /* Find an allocated page */
669 for (; pfn < max_pfn; pfn++) {
670 /*
671 * This temporary page_owner is required so
672 * that we can avoid the context switches while holding
673 * the rcu lock and copying the page owner information to
674 * user through copy_to_user() or GFP_KERNEL allocations.
675 */
676 struct page_owner page_owner_tmp;
677
678 /*
679 * If the new page is in a new MAX_ORDER_NR_PAGES area,
680 * validate the area as existing, skip it if not
681 */
682 if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
683 pfn += MAX_ORDER_NR_PAGES - 1;
684 continue;
685 }
686
687 page = pfn_to_page(pfn);
688 if (PageBuddy(page)) {
689 unsigned long freepage_order = buddy_order_unsafe(page);
690
691 if (freepage_order <= MAX_PAGE_ORDER)
692 pfn += (1UL << freepage_order) - 1;
693 continue;
694 }
695
696 page_ext = page_ext_get(page);
697 if (unlikely(!page_ext))
698 continue;
699
700 /*
701 * Some pages could be missed by concurrent allocation or free,
702 * because we don't hold the zone lock.
703 */
704 if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
705 goto ext_put_continue;
706
707 /*
708 * Although we do have the info about past allocation of free
709 * pages, it's not relevant for current memory usage.
710 */
711 if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
712 goto ext_put_continue;
713
714 page_owner = get_page_owner(page_ext);
715
716 /*
717 * Don't print "tail" pages of high-order allocations as that
718 * would inflate the stats.
719 */
720 if (!IS_ALIGNED(pfn, 1 << page_owner->order))
721 goto ext_put_continue;
722
723 /*
724 * Access to page_ext->handle isn't synchronous so we should
725 * be careful to access it.
726 */
727 handle = READ_ONCE(page_owner->handle);
728 if (!handle)
729 goto ext_put_continue;
730
731 /* Record the next PFN to read in the file offset */
732 *ppos = pfn + 1;
733
734 page_owner_tmp = *page_owner;
735 page_ext_put(page_ext);
736 return print_page_owner(buf, count, pfn, page,
737 page_owner: &page_owner_tmp, handle);
738ext_put_continue:
739 page_ext_put(page_ext);
740 }
741
742 return 0;
743}
744
745static loff_t lseek_page_owner(struct file *file, loff_t offset, int orig)
746{
747 switch (orig) {
748 case SEEK_SET:
749 file->f_pos = offset;
750 break;
751 case SEEK_CUR:
752 file->f_pos += offset;
753 break;
754 default:
755 return -EINVAL;
756 }
757 return file->f_pos;
758}
759
760static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
761{
762 unsigned long pfn = zone->zone_start_pfn;
763 unsigned long end_pfn = zone_end_pfn(zone);
764 unsigned long count = 0;
765
766 /*
767 * Walk the zone in pageblock_nr_pages steps. If a page block spans
768 * a zone boundary, it will be double counted between zones. This does
769 * not matter as the mixed block count will still be correct
770 */
771 for (; pfn < end_pfn; ) {
772 unsigned long block_end_pfn;
773
774 if (!pfn_valid(pfn)) {
775 pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
776 continue;
777 }
778
779 block_end_pfn = pageblock_end_pfn(pfn);
780 block_end_pfn = min(block_end_pfn, end_pfn);
781
782 for (; pfn < block_end_pfn; pfn++) {
783 struct page *page = pfn_to_page(pfn);
784 struct page_ext *page_ext;
785
786 if (page_zone(page) != zone)
787 continue;
788
789 /*
790 * To avoid having to grab zone->lock, be a little
791 * careful when reading buddy page order. The only
792 * danger is that we skip too much and potentially miss
793 * some early allocated pages, which is better than
794 * heavy lock contention.
795 */
796 if (PageBuddy(page)) {
797 unsigned long order = buddy_order_unsafe(page);
798
799 if (order > 0 && order <= MAX_PAGE_ORDER)
800 pfn += (1UL << order) - 1;
801 continue;
802 }
803
804 if (PageReserved(page))
805 continue;
806
807 page_ext = page_ext_get(page);
808 if (unlikely(!page_ext))
809 continue;
810
811 /* Maybe overlapping zone */
812 if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
813 goto ext_put_continue;
814
815 /* Found early allocated page */
816 __update_page_owner_handle(page, handle: early_handle, order: 0, gfp_mask: 0,
817 last_migrate_reason: -1, ts_nsec: local_clock(), current->pid,
818 current->tgid, current->comm);
819 count++;
820ext_put_continue:
821 page_ext_put(page_ext);
822 }
823 cond_resched();
824 }
825
826 pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
827 pgdat->node_id, zone->name, count);
828}
829
830static void init_zones_in_node(pg_data_t *pgdat)
831{
832 struct zone *zone;
833 struct zone *node_zones = pgdat->node_zones;
834
835 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
836 if (!populated_zone(zone))
837 continue;
838
839 init_pages_in_zone(pgdat, zone);
840 }
841}
842
843static void init_early_allocated_pages(void)
844{
845 pg_data_t *pgdat;
846
847 for_each_online_pgdat(pgdat)
848 init_zones_in_node(pgdat);
849}
850
851static const struct file_operations proc_page_owner_operations = {
852 .read = read_page_owner,
853 .llseek = lseek_page_owner,
854};
855
856static void *stack_start(struct seq_file *m, loff_t *ppos)
857{
858 struct stack *stack;
859
860 if (*ppos == -1UL)
861 return NULL;
862
863 if (!*ppos) {
864 /*
865 * This pairs with smp_store_release() from function
866 * add_stack_record_to_list(), so we get a consistent
867 * value of stack_list.
868 */
869 stack = smp_load_acquire(&stack_list);
870 m->private = stack;
871 } else {
872 stack = m->private;
873 }
874
875 return stack;
876}
877
878static void *stack_next(struct seq_file *m, void *v, loff_t *ppos)
879{
880 struct stack *stack = v;
881
882 stack = stack->next;
883 *ppos = stack ? *ppos + 1 : -1UL;
884 m->private = stack;
885
886 return stack;
887}
888
889static unsigned long page_owner_pages_threshold;
890
891static int stack_print(struct seq_file *m, void *v)
892{
893 int i, nr_base_pages;
894 struct stack *stack = v;
895 unsigned long *entries;
896 unsigned long nr_entries;
897 struct stack_record *stack_record = stack->stack_record;
898
899 if (!stack->stack_record)
900 return 0;
901
902 nr_entries = stack_record->size;
903 entries = stack_record->entries;
904 nr_base_pages = refcount_read(r: &stack_record->count) - 1;
905
906 if (nr_base_pages < 1 || nr_base_pages < page_owner_pages_threshold)
907 return 0;
908
909 for (i = 0; i < nr_entries; i++)
910 seq_printf(m, fmt: " %pS\n", (void *)entries[i]);
911 seq_printf(m, fmt: "nr_base_pages: %d\n\n", nr_base_pages);
912
913 return 0;
914}
915
916static void stack_stop(struct seq_file *m, void *v)
917{
918}
919
920static const struct seq_operations page_owner_stack_op = {
921 .start = stack_start,
922 .next = stack_next,
923 .stop = stack_stop,
924 .show = stack_print
925};
926
927static int page_owner_stack_open(struct inode *inode, struct file *file)
928{
929 return seq_open_private(file, &page_owner_stack_op, 0);
930}
931
932static const struct file_operations page_owner_stack_operations = {
933 .open = page_owner_stack_open,
934 .read = seq_read,
935 .llseek = seq_lseek,
936 .release = seq_release,
937};
938
939static int page_owner_threshold_get(void *data, u64 *val)
940{
941 *val = READ_ONCE(page_owner_pages_threshold);
942 return 0;
943}
944
945static int page_owner_threshold_set(void *data, u64 val)
946{
947 WRITE_ONCE(page_owner_pages_threshold, val);
948 return 0;
949}
950
951DEFINE_SIMPLE_ATTRIBUTE(proc_page_owner_threshold, &page_owner_threshold_get,
952 &page_owner_threshold_set, "%llu");
953
954
955static int __init pageowner_init(void)
956{
957 struct dentry *dir;
958
959 if (!static_branch_unlikely(&page_owner_inited)) {
960 pr_info("page_owner is disabled\n");
961 return 0;
962 }
963
964 debugfs_create_file("page_owner", 0400, NULL, NULL,
965 &proc_page_owner_operations);
966 dir = debugfs_create_dir(name: "page_owner_stacks", NULL);
967 debugfs_create_file("show_stacks", 0400, dir, NULL,
968 &page_owner_stack_operations);
969 debugfs_create_file("count_threshold", 0600, dir, NULL,
970 &proc_page_owner_threshold);
971
972 return 0;
973}
974late_initcall(pageowner_init)
975

source code of linux/mm/page_owner.c