root/mm/page_owner.c

DEFINITIONS

1. early_page_owner_param
2. need_page_owner
3. create_dummy_stack
4. register_dummy_stack
5. register_failure_stack
6. register_early_stack
7. init_page_owner
8. get_page_owner
9. check_recursive_alloc
10. save_stack
11. __reset_page_owner
12. __set_page_owner_handle
13. __set_page_owner
14. __set_page_owner_migrate_reason
15. __split_page_owner
16. __copy_page_owner
17. pagetypeinfo_showmixedcount_print
18. print_page_owner
19. __dump_page_owner
20. read_page_owner
21. init_pages_in_zone
22. init_zones_in_node
23. init_early_allocated_pages
24. pageowner_init

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