mm/page_owner.c

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