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TOMOYO Linux Cross Reference
Linux/mm/page_owner.c

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  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 

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