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 #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
  24 struct 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 };
  36
  37 static bool page_owner_enabled = false;
  38 DEFINE_STATIC_KEY_FALSE(page_owner_inited);
  39
  40 static depot_stack_handle_t dummy_handle;
  41 static depot_stack_handle_t failure_handle;
  42 static depot_stack_handle_t early_handle;
  43
  44 static void init_early_allocated_pages(void);
  45
  46 static int __init early_page_owner_param(char *buf)
  47 {
  48         return kstrtobool(buf, &page_owner_enabled);
  49 }
  50 early_param("page_owner", early_page_owner_param);
  51
  52 static __init bool need_page_owner(void)
  53 {
  54         return page_owner_enabled;
  55 }
  56
  57 static __always_inline depot_stack_handle_t create_dummy_stack(void)
  58 {
  59         unsigned long entries[4];
  60         unsigned int nr_entries;
  61
  62         nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
  63         return stack_depot_save(entries, nr_entries, GFP_KERNEL);
  64 }
  65
  66 static noinline void register_dummy_stack(void)
  67 {
  68         dummy_handle = create_dummy_stack();
  69 }
  70
  71 static noinline void register_failure_stack(void)
  72 {
  73         failure_handle = create_dummy_stack();
  74 }
  75
  76 static noinline void register_early_stack(void)
  77 {
  78         early_handle = create_dummy_stack();
  79 }
  80
  81 static __init void init_page_owner(void)
  82 {
  83         if (!page_owner_enabled)
  84                 return;
  85
  86         stack_depot_init();
  87
  88         register_dummy_stack();
  89         register_failure_stack();
  90         register_early_stack();
  91         static_branch_enable(&page_owner_inited);
  92         init_early_allocated_pages();
  93 }
  94
  95 struct page_ext_operations page_owner_ops = {
  96         .size = sizeof(struct page_owner),
  97         .need = need_page_owner,
  98         .init = init_page_owner,
  99 };
 100
 101 static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
 102 {
 103         return (void *)page_ext + page_owner_ops.offset;
 104 }
 105
 106 static noinline depot_stack_handle_t save_stack(gfp_t flags)
 107 {
 108         unsigned long entries[PAGE_OWNER_STACK_DEPTH];
 109         depot_stack_handle_t handle;
 110         unsigned int nr_entries;
 111
 112         /*
 113          * Avoid recursion.
 114          *
 115          * Sometimes page metadata allocation tracking requires more
 116          * memory to be allocated:
 117          * - when new stack trace is saved to stack depot
 118          * - when backtrace itself is calculated (ia64)
 119          */
 120         if (current->in_page_owner)
 121                 return dummy_handle;
 122         current->in_page_owner = 1;
 123
 124         nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
 125         handle = stack_depot_save(entries, nr_entries, flags);
 126         if (!handle)
 127                 handle = failure_handle;
 128
 129         current->in_page_owner = 0;
 130         return handle;
 131 }
 132
 133 void __reset_page_owner(struct page *page, unsigned short order)
 134 {
 135         int i;
 136         struct page_ext *page_ext;
 137         depot_stack_handle_t handle;
 138         struct page_owner *page_owner;
 139         u64 free_ts_nsec = local_clock();
 140
 141         page_ext = lookup_page_ext(page);
 142         if (unlikely(!page_ext))
 143                 return;
 144
 145         handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
 146         for (i = 0; i < (1 << order); i++) {
 147                 __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
 148                 page_owner = get_page_owner(page_ext);
 149                 page_owner->free_handle = handle;
 150                 page_owner->free_ts_nsec = free_ts_nsec;
 151                 page_ext = page_ext_next(page_ext);
 152         }
 153 }
 154
 155 static inline void __set_page_owner_handle(struct page_ext *page_ext,
 156                                         depot_stack_handle_t handle,
 157                                         unsigned short order, gfp_t gfp_mask)
 158 {
 159         struct page_owner *page_owner;
 160         int i;
 161
 162         for (i = 0; i < (1 << order); i++) {
 163                 page_owner = get_page_owner(page_ext);
 164                 page_owner->handle = handle;
 165                 page_owner->order = order;
 166                 page_owner->gfp_mask = gfp_mask;
 167                 page_owner->last_migrate_reason = -1;
 168                 page_owner->pid = current->pid;
 169                 page_owner->tgid = current->tgid;
 170                 page_owner->ts_nsec = local_clock();
 171                 strlcpy(page_owner->comm, current->comm,
 172                         sizeof(page_owner->comm));
 173                 __set_bit(PAGE_EXT_OWNER, &page_ext->flags);
 174                 __set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
 175
 176                 page_ext = page_ext_next(page_ext);
 177         }
 178 }
 179
 180 noinline void __set_page_owner(struct page *page, unsigned short order,
 181                                         gfp_t gfp_mask)
 182 {
 183         struct page_ext *page_ext = lookup_page_ext(page);
 184         depot_stack_handle_t handle;
 185
 186         if (unlikely(!page_ext))
 187                 return;
 188
 189         handle = save_stack(gfp_mask);
 190         __set_page_owner_handle(page_ext, handle, order, gfp_mask);
 191 }
 192
 193 void __set_page_owner_migrate_reason(struct page *page, int reason)
 194 {
 195         struct page_ext *page_ext = lookup_page_ext(page);
 196         struct page_owner *page_owner;
 197
 198         if (unlikely(!page_ext))
 199                 return;
 200
 201         page_owner = get_page_owner(page_ext);
 202         page_owner->last_migrate_reason = reason;
 203 }
 204
 205 void __split_page_owner(struct page *page, unsigned int nr)
 206 {
 207         int i;
 208         struct page_ext *page_ext = lookup_page_ext(page);
 209         struct page_owner *page_owner;
 210
 211         if (unlikely(!page_ext))
 212                 return;
 213
 214         for (i = 0; i < nr; i++) {
 215                 page_owner = get_page_owner(page_ext);
 216                 page_owner->order = 0;
 217                 page_ext = page_ext_next(page_ext);
 218         }
 219 }
 220
 221 void __folio_copy_owner(struct folio *newfolio, struct folio *old)
 222 {
 223         struct page_ext *old_ext = lookup_page_ext(&old->page);
 224         struct page_ext *new_ext = lookup_page_ext(&newfolio->page);
 225         struct page_owner *old_page_owner, *new_page_owner;
 226
 227         if (unlikely(!old_ext || !new_ext))
 228                 return;
 229
 230         old_page_owner = get_page_owner(old_ext);
 231         new_page_owner = get_page_owner(new_ext);
 232         new_page_owner->order = old_page_owner->order;
 233         new_page_owner->gfp_mask = old_page_owner->gfp_mask;
 234         new_page_owner->last_migrate_reason =
 235                 old_page_owner->last_migrate_reason;
 236         new_page_owner->handle = old_page_owner->handle;
 237         new_page_owner->pid = old_page_owner->pid;
 238         new_page_owner->tgid = old_page_owner->tgid;
 239         new_page_owner->ts_nsec = old_page_owner->ts_nsec;
 240         new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
 241         strcpy(new_page_owner->comm, old_page_owner->comm);
 242
 243         /*
 244          * We don't clear the bit on the old folio as it's going to be freed
 245          * after migration. Until then, the info can be useful in case of
 246          * a bug, and the overall stats will be off a bit only temporarily.
 247          * Also, migrate_misplaced_transhuge_page() can still fail the
 248          * migration and then we want the old folio to retain the info. But
 249          * in that case we also don't need to explicitly clear the info from
 250          * the new page, which will be freed.
 251          */
 252         __set_bit(PAGE_EXT_OWNER, &new_ext->flags);
 253         __set_bit(PAGE_EXT_OWNER_ALLOCATED, &new_ext->flags);
 254 }
 255
 256 void pagetypeinfo_showmixedcount_print(struct seq_file *m,
 257                                        pg_data_t *pgdat, struct zone *zone)
 258 {
 259         struct page *page;
 260         struct page_ext *page_ext;
 261         struct page_owner *page_owner;
 262         unsigned long pfn, block_end_pfn;
 263         unsigned long end_pfn = zone_end_pfn(zone);
 264         unsigned long count[MIGRATE_TYPES] = { 0, };
 265         int pageblock_mt, page_mt;
 266         int i;
 267
 268         /* Scan block by block. First and last block may be incomplete */
 269         pfn = zone->zone_start_pfn;
 270
 271         /*
 272          * Walk the zone in pageblock_nr_pages steps. If a page block spans
 273          * a zone boundary, it will be double counted between zones. This does
 274          * not matter as the mixed block count will still be correct
 275          */
 276         for (; pfn < end_pfn; ) {
 277                 page = pfn_to_online_page(pfn);
 278                 if (!page) {
 279                         pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
 280                         continue;
 281                 }
 282
 283                 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 284                 block_end_pfn = min(block_end_pfn, end_pfn);
 285
 286                 pageblock_mt = get_pageblock_migratetype(page);
 287
 288                 for (; pfn < block_end_pfn; pfn++) {
 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 = buddy_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 = gfp_migratetype(page_owner->gfp_mask);
 316                         if (pageblock_mt != page_mt) {
 317                                 if (is_migrate_cma(pageblock_mt))
 318                                         count[MIGRATE_MOVABLE]++;
 319                                 else
 320                                         count[pageblock_mt]++;
 321
 322                                 pfn = block_end_pfn;
 323                                 break;
 324                         }
 325                         pfn += (1UL << page_owner->order) - 1;
 326                 }
 327         }
 328
 329         /* Print counts */
 330         seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
 331         for (i = 0; i < MIGRATE_TYPES; i++)
 332                 seq_printf(m, "%12lu ", count[i]);
 333         seq_putc(m, '\n');
 334 }
 335
 336 /*
 337  * Looking for memcg information and print it out
 338  */
 339 static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret,
 340                                          struct page *page)
 341 {
 342 #ifdef CONFIG_MEMCG
 343         unsigned long memcg_data;
 344         struct mem_cgroup *memcg;
 345         bool online;
 346         char name[80];
 347
 348         rcu_read_lock();
 349         memcg_data = READ_ONCE(page->memcg_data);
 350         if (!memcg_data)
 351                 goto out_unlock;
 352
 353         if (memcg_data & MEMCG_DATA_OBJCGS)
 354                 ret += scnprintf(kbuf + ret, count - ret,
 355                                 "Slab cache page\n");
 356
 357         memcg = page_memcg_check(page);
 358         if (!memcg)
 359                 goto out_unlock;
 360
 361         online = (memcg->css.flags & CSS_ONLINE);
 362         cgroup_name(memcg->css.cgroup, name, sizeof(name));
 363         ret += scnprintf(kbuf + ret, count - ret,
 364                         "Charged %sto %smemcg %s\n",
 365                         PageMemcgKmem(page) ? "(via objcg) " : "",
 366                         online ? "" : "offline ",
 367                         name);
 368 out_unlock:
 369         rcu_read_unlock();
 370 #endif /* CONFIG_MEMCG */
 371
 372         return ret;
 373 }
 374
 375 static ssize_t
 376 print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 377                 struct page *page, struct page_owner *page_owner,
 378                 depot_stack_handle_t handle)
 379 {
 380         int ret, pageblock_mt, page_mt;
 381         char *kbuf;
 382
 383         count = min_t(size_t, count, PAGE_SIZE);
 384         kbuf = kmalloc(count, GFP_KERNEL);
 385         if (!kbuf)
 386                 return -ENOMEM;
 387
 388         ret = scnprintf(kbuf, count,
 389                         "Page allocated via order %u, mask %#x(%pGg), pid %d, tgid %d (%s), ts %llu ns, free_ts %llu ns\n",
 390                         page_owner->order, page_owner->gfp_mask,
 391                         &page_owner->gfp_mask, page_owner->pid,
 392                         page_owner->tgid, page_owner->comm,
 393                         page_owner->ts_nsec, page_owner->free_ts_nsec);
 394
 395         /* Print information relevant to grouping pages by mobility */
 396         pageblock_mt = get_pageblock_migratetype(page);
 397         page_mt  = gfp_migratetype(page_owner->gfp_mask);
 398         ret += scnprintf(kbuf + ret, count - ret,
 399                         "PFN %lu type %s Block %lu type %s Flags %pGp\n",
 400                         pfn,
 401                         migratetype_names[page_mt],
 402                         pfn >> pageblock_order,
 403                         migratetype_names[pageblock_mt],
 404                         &page->flags);
 405
 406         ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
 407         if (ret >= count)
 408                 goto err;
 409
 410         if (page_owner->last_migrate_reason != -1) {
 411                 ret += scnprintf(kbuf + ret, count - ret,
 412                         "Page has been migrated, last migrate reason: %s\n",
 413                         migrate_reason_names[page_owner->last_migrate_reason]);
 414         }
 415
 416         ret = print_page_owner_memcg(kbuf, count, ret, page);
 417
 418         ret += snprintf(kbuf + ret, count - ret, "\n");
 419         if (ret >= count)
 420                 goto err;
 421
 422         if (copy_to_user(buf, kbuf, ret))
 423                 ret = -EFAULT;
 424
 425         kfree(kbuf);
 426         return ret;
 427
 428 err:
 429         kfree(kbuf);
 430         return -ENOMEM;
 431 }
 432
 433 void __dump_page_owner(const struct page *page)
 434 {
 435         struct page_ext *page_ext = lookup_page_ext(page);
 436         struct page_owner *page_owner;
 437         depot_stack_handle_t handle;
 438         gfp_t gfp_mask;
 439         int mt;
 440
 441         if (unlikely(!page_ext)) {
 442                 pr_alert("There is not page extension available.\n");
 443                 return;
 444         }
 445
 446         page_owner = get_page_owner(page_ext);
 447         gfp_mask = page_owner->gfp_mask;
 448         mt = gfp_migratetype(gfp_mask);
 449
 450         if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
 451                 pr_alert("page_owner info is not present (never set?)\n");
 452                 return;
 453         }
 454
 455         if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
 456                 pr_alert("page_owner tracks the page as allocated\n");
 457         else
 458                 pr_alert("page_owner tracks the page as freed\n");
 459
 460         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",
 461                  page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
 462                  page_owner->pid, page_owner->tgid, page_owner->comm,
 463                  page_owner->ts_nsec, page_owner->free_ts_nsec);
 464
 465         handle = READ_ONCE(page_owner->handle);
 466         if (!handle)
 467                 pr_alert("page_owner allocation stack trace missing\n");
 468         else
 469                 stack_depot_print(handle);
 470
 471         handle = READ_ONCE(page_owner->free_handle);
 472         if (!handle) {
 473                 pr_alert("page_owner free stack trace missing\n");
 474         } else {
 475                 pr_alert("page last free stack trace:\n");
 476                 stack_depot_print(handle);
 477         }
 478
 479         if (page_owner->last_migrate_reason != -1)
 480                 pr_alert("page has been migrated, last migrate reason: %s\n",
 481                         migrate_reason_names[page_owner->last_migrate_reason]);
 482 }
 483
 484 static ssize_t
 485 read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 486 {
 487         unsigned long pfn;
 488         struct page *page;
 489         struct page_ext *page_ext;
 490         struct page_owner *page_owner;
 491         depot_stack_handle_t handle;
 492
 493         if (!static_branch_unlikely(&page_owner_inited))
 494                 return -EINVAL;
 495
 496         page = NULL;
 497         pfn = min_low_pfn + *ppos;
 498
 499         /* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
 500         while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
 501                 pfn++;
 502
 503         drain_all_pages(NULL);
 504
 505         /* Find an allocated page */
 506         for (; pfn < max_pfn; pfn++) {
 507                 /*
 508                  * If the new page is in a new MAX_ORDER_NR_PAGES area,
 509                  * validate the area as existing, skip it if not
 510                  */
 511                 if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
 512                         pfn += MAX_ORDER_NR_PAGES - 1;
 513                         continue;
 514                 }
 515
 516                 page = pfn_to_page(pfn);
 517                 if (PageBuddy(page)) {
 518                         unsigned long freepage_order = buddy_order_unsafe(page);
 519
 520                         if (freepage_order < MAX_ORDER)
 521                                 pfn += (1UL << freepage_order) - 1;
 522                         continue;
 523                 }
 524
 525                 page_ext = lookup_page_ext(page);
 526                 if (unlikely(!page_ext))
 527                         continue;
 528
 529                 /*
 530                  * Some pages could be missed by concurrent allocation or free,
 531                  * because we don't hold the zone lock.
 532                  */
 533                 if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
 534                         continue;
 535
 536                 /*
 537                  * Although we do have the info about past allocation of free
 538                  * pages, it's not relevant for current memory usage.
 539                  */
 540                 if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
 541                         continue;
 542
 543                 page_owner = get_page_owner(page_ext);
 544
 545                 /*
 546                  * Don't print "tail" pages of high-order allocations as that
 547                  * would inflate the stats.
 548                  */
 549                 if (!IS_ALIGNED(pfn, 1 << page_owner->order))
 550                         continue;
 551
 552                 /*
 553                  * Access to page_ext->handle isn't synchronous so we should
 554                  * be careful to access it.
 555                  */
 556                 handle = READ_ONCE(page_owner->handle);
 557                 if (!handle)
 558                         continue;
 559
 560                 /* Record the next PFN to read in the file offset */
 561                 *ppos = (pfn - min_low_pfn) + 1;
 562
 563                 return print_page_owner(buf, count, pfn, page,
 564                                 page_owner, handle);
 565         }
 566
 567         return 0;
 568 }
 569
 570 static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 571 {
 572         unsigned long pfn = zone->zone_start_pfn;
 573         unsigned long end_pfn = zone_end_pfn(zone);
 574         unsigned long count = 0;
 575
 576         /*
 577          * Walk the zone in pageblock_nr_pages steps. If a page block spans
 578          * a zone boundary, it will be double counted between zones. This does
 579          * not matter as the mixed block count will still be correct
 580          */
 581         for (; pfn < end_pfn; ) {
 582                 unsigned long block_end_pfn;
 583
 584                 if (!pfn_valid(pfn)) {
 585                         pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
 586                         continue;
 587                 }
 588
 589                 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 590                 block_end_pfn = min(block_end_pfn, end_pfn);
 591
 592                 for (; pfn < block_end_pfn; pfn++) {
 593                         struct page *page = pfn_to_page(pfn);
 594                         struct page_ext *page_ext;
 595
 596                         if (page_zone(page) != zone)
 597                                 continue;
 598
 599                         /*
 600                          * To avoid having to grab zone->lock, be a little
 601                          * careful when reading buddy page order. The only
 602                          * danger is that we skip too much and potentially miss
 603                          * some early allocated pages, which is better than
 604                          * heavy lock contention.
 605                          */
 606                         if (PageBuddy(page)) {
 607                                 unsigned long order = buddy_order_unsafe(page);
 608
 609                                 if (order > 0 && order < MAX_ORDER)
 610                                         pfn += (1UL << order) - 1;
 611                                 continue;
 612                         }
 613
 614                         if (PageReserved(page))
 615                                 continue;
 616
 617                         page_ext = lookup_page_ext(page);
 618                         if (unlikely(!page_ext))
 619                                 continue;
 620
 621                         /* Maybe overlapping zone */
 622                         if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
 623                                 continue;
 624
 625                         /* Found early allocated page */
 626                         __set_page_owner_handle(page_ext, early_handle,
 627                                                 0, 0);
 628                         count++;
 629                 }
 630                 cond_resched();
 631         }
 632
 633         pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
 634                 pgdat->node_id, zone->name, count);
 635 }
 636
 637 static void init_zones_in_node(pg_data_t *pgdat)
 638 {
 639         struct zone *zone;
 640         struct zone *node_zones = pgdat->node_zones;
 641
 642         for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
 643                 if (!populated_zone(zone))
 644                         continue;
 645
 646                 init_pages_in_zone(pgdat, zone);
 647         }
 648 }
 649
 650 static void init_early_allocated_pages(void)
 651 {
 652         pg_data_t *pgdat;
 653
 654         for_each_online_pgdat(pgdat)
 655                 init_zones_in_node(pgdat);
 656 }
 657
 658 static const struct file_operations proc_page_owner_operations = {
 659         .read           = read_page_owner,
 660 };
 661
 662 static int __init pageowner_init(void)
 663 {
 664         if (!static_branch_unlikely(&page_owner_inited)) {
 665                 pr_info("page_owner is disabled\n");
 666                 return 0;
 667         }
 668
 669         debugfs_create_file("page_owner", 0400, NULL, NULL,
 670                             &proc_page_owner_operations);
 671
 672         return 0;
 673 }
 674 late_initcall(pageowner_init)