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
early_page_owner_param(char * buf)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
need_page_owner(void)49 static bool need_page_owner(void)
50 {
51 return page_owner_enabled;
52 }
53
create_dummy_stack(void)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
register_dummy_stack(void)63 static noinline void register_dummy_stack(void)
64 {
65 dummy_handle = create_dummy_stack();
66 }
67
register_failure_stack(void)68 static noinline void register_failure_stack(void)
69 {
70 failure_handle = create_dummy_stack();
71 }
72
register_early_stack(void)73 static noinline void register_early_stack(void)
74 {
75 early_handle = create_dummy_stack();
76 }
77
init_page_owner(void)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
get_page_owner(struct page_ext * page_ext)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
save_stack(gfp_t flags)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
__reset_page_owner(struct page * page,unsigned short order)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
__set_page_owner_handle(struct page_ext * page_ext,depot_stack_handle_t handle,unsigned short order,gfp_t gfp_mask)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
__set_page_owner(struct page * page,unsigned short order,gfp_t gfp_mask)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
__set_page_owner_migrate_reason(struct page * page,int reason)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
__split_page_owner(struct page * page,unsigned int nr)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
__folio_copy_owner(struct folio * newfolio,struct folio * old)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
pagetypeinfo_showmixedcount_print(struct seq_file * m,pg_data_t * pgdat,struct zone * zone)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
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)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
__dump_page_owner(const struct page * page)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
read_page_owner(struct file * file,char __user * buf,size_t count,loff_t * ppos)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
init_pages_in_zone(pg_data_t * pgdat,struct zone * zone)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
init_zones_in_node(pg_data_t * pgdat)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
init_early_allocated_pages(void)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
pageowner_init(void)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