mm/hugetlb.c

   1 /*
   2  * Generic hugetlb support.
   3  * (C) William Irwin, April 2004
   4  */
   5 #include <linux/gfp.h>
   6 #include <linux/list.h>
   7 #include <linux/init.h>
   8 #include <linux/module.h>
   9 #include <linux/mm.h>
  10 #include <linux/sysctl.h>
  11 #include <linux/highmem.h>
  12 #include <linux/nodemask.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/mempolicy.h>
  15 #include <linux/cpuset.h>
  16 #include <linux/mutex.h>
  17
  18 #include <asm/page.h>
  19 #include <asm/pgtable.h>
  20
  21 #include <linux/hugetlb.h>
  22 #include "internal.h"
  23
  24 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  25 static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
  26 static unsigned long surplus_huge_pages;
  27 unsigned long max_huge_pages;
  28 static struct list_head hugepage_freelists[MAX_NUMNODES];
  29 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  30 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  31 static unsigned int surplus_huge_pages_node[MAX_NUMNODES];
  32 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
  33 unsigned long hugepages_treat_as_movable;
  34 unsigned long nr_overcommit_huge_pages;
  35 static int hugetlb_next_nid;
  36
  37 /*
  38  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  39  */
  40 static DEFINE_SPINLOCK(hugetlb_lock);
  41
  42 static void clear_huge_page(struct page *page, unsigned long addr)
  43 {
  44         int i;
  45
  46         might_sleep();
  47         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  48                 cond_resched();
  49                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
  50         }
  51 }
  52
  53 static void copy_huge_page(struct page *dst, struct page *src,
  54                            unsigned long addr, struct vm_area_struct *vma)
  55 {
  56         int i;
  57
  58         might_sleep();
  59         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  60                 cond_resched();
  61                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
  62         }
  63 }
  64
  65 static void enqueue_huge_page(struct page *page)
  66 {
  67         int nid = page_to_nid(page);
  68         list_add(&page->lru, &hugepage_freelists[nid]);
  69         free_huge_pages++;
  70         free_huge_pages_node[nid]++;
  71 }
  72
  73 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  74                                 unsigned long address)
  75 {
  76         int nid;
  77         struct page *page = NULL;
  78         struct mempolicy *mpol;
  79         struct zonelist *zonelist = huge_zonelist(vma, address,
  80                                         htlb_alloc_mask, &mpol);
  81         struct zone **z;
  82
  83         for (z = zonelist->zones; *z; z++) {
  84                 nid = zone_to_nid(*z);
  85                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
  86                     !list_empty(&hugepage_freelists[nid])) {
  87                         page = list_entry(hugepage_freelists[nid].next,
  88                                           struct page, lru);
  89                         list_del(&page->lru);
  90                         free_huge_pages--;
  91                         free_huge_pages_node[nid]--;
  92                         if (vma && vma->vm_flags & VM_MAYSHARE)
  93                                 resv_huge_pages--;
  94                         break;
  95                 }
  96         }
  97         mpol_free(mpol);        /* unref if mpol !NULL */
  98         return page;
  99 }
 100
 101 static void update_and_free_page(struct page *page)
 102 {
 103         int i;
 104         nr_huge_pages--;
 105         nr_huge_pages_node[page_to_nid(page)]--;
 106         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 107                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 108                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 109                                 1 << PG_private | 1<< PG_writeback);
 110         }
 111         set_compound_page_dtor(page, NULL);
 112         set_page_refcounted(page);
 113         __free_pages(page, HUGETLB_PAGE_ORDER);
 114 }
 115
 116 static void free_huge_page(struct page *page)
 117 {
 118         int nid = page_to_nid(page);
 119         struct address_space *mapping;
 120
 121         mapping = (struct address_space *) page_private(page);
 122         BUG_ON(page_count(page));
 123         INIT_LIST_HEAD(&page->lru);
 124
 125         spin_lock(&hugetlb_lock);
 126         if (surplus_huge_pages_node[nid]) {
 127                 update_and_free_page(page);
 128                 surplus_huge_pages--;
 129                 surplus_huge_pages_node[nid]--;
 130         } else {
 131                 enqueue_huge_page(page);
 132         }
 133         spin_unlock(&hugetlb_lock);
 134         if (mapping)
 135                 hugetlb_put_quota(mapping, 1);
 136         set_page_private(page, 0);
 137 }
 138
 139 /*
 140  * Increment or decrement surplus_huge_pages.  Keep node-specific counters
 141  * balanced by operating on them in a round-robin fashion.
 142  * Returns 1 if an adjustment was made.
 143  */
 144 static int adjust_pool_surplus(int delta)
 145 {
 146         static int prev_nid;
 147         int nid = prev_nid;
 148         int ret = 0;
 149
 150         VM_BUG_ON(delta != -1 && delta != 1);
 151         do {
 152                 nid = next_node(nid, node_online_map);
 153                 if (nid == MAX_NUMNODES)
 154                         nid = first_node(node_online_map);
 155
 156                 /* To shrink on this node, there must be a surplus page */
 157                 if (delta < 0 && !surplus_huge_pages_node[nid])
 158                         continue;
 159                 /* Surplus cannot exceed the total number of pages */
 160                 if (delta > 0 && surplus_huge_pages_node[nid] >=
 161                                                 nr_huge_pages_node[nid])
 162                         continue;
 163
 164                 surplus_huge_pages += delta;
 165                 surplus_huge_pages_node[nid] += delta;
 166                 ret = 1;
 167                 break;
 168         } while (nid != prev_nid);
 169
 170         prev_nid = nid;
 171         return ret;
 172 }
 173
 174 static struct page *alloc_fresh_huge_page_node(int nid)
 175 {
 176         struct page *page;
 177
 178         page = alloc_pages_node(nid,
 179                 htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|__GFP_NOWARN,
 180                 HUGETLB_PAGE_ORDER);
 181         if (page) {
 182                 set_compound_page_dtor(page, free_huge_page);
 183                 spin_lock(&hugetlb_lock);
 184                 nr_huge_pages++;
 185                 nr_huge_pages_node[nid]++;
 186                 spin_unlock(&hugetlb_lock);
 187                 put_page(page); /* free it into the hugepage allocator */
 188         }
 189
 190         return page;
 191 }
 192
 193 static int alloc_fresh_huge_page(void)
 194 {
 195         struct page *page;
 196         int start_nid;
 197         int next_nid;
 198         int ret = 0;
 199
 200         start_nid = hugetlb_next_nid;
 201
 202         do {
 203                 page = alloc_fresh_huge_page_node(hugetlb_next_nid);
 204                 if (page)
 205                         ret = 1;
 206                 /*
 207                  * Use a helper variable to find the next node and then
 208                  * copy it back to hugetlb_next_nid afterwards:
 209                  * otherwise there's a window in which a racer might
 210                  * pass invalid nid MAX_NUMNODES to alloc_pages_node.
 211                  * But we don't need to use a spin_lock here: it really
 212                  * doesn't matter if occasionally a racer chooses the
 213                  * same nid as we do.  Move nid forward in the mask even
 214                  * if we just successfully allocated a hugepage so that
 215                  * the next caller gets hugepages on the next node.
 216                  */
 217                 next_nid = next_node(hugetlb_next_nid, node_online_map);
 218                 if (next_nid == MAX_NUMNODES)
 219                         next_nid = first_node(node_online_map);
 220                 hugetlb_next_nid = next_nid;
 221         } while (!page && hugetlb_next_nid != start_nid);
 222
 223         return ret;
 224 }
 225
 226 static struct page *alloc_buddy_huge_page(struct vm_area_struct *vma,
 227                                                 unsigned long address)
 228 {
 229         struct page *page;
 230         unsigned int nid;
 231
 232         /*
 233          * Assume we will successfully allocate the surplus page to
 234          * prevent racing processes from causing the surplus to exceed
 235          * overcommit
 236          *
 237          * This however introduces a different race, where a process B
 238          * tries to grow the static hugepage pool while alloc_pages() is
 239          * called by process A. B will only examine the per-node
 240          * counters in determining if surplus huge pages can be
 241          * converted to normal huge pages in adjust_pool_surplus(). A
 242          * won't be able to increment the per-node counter, until the
 243          * lock is dropped by B, but B doesn't drop hugetlb_lock until
 244          * no more huge pages can be converted from surplus to normal
 245          * state (and doesn't try to convert again). Thus, we have a
 246          * case where a surplus huge page exists, the pool is grown, and
 247          * the surplus huge page still exists after, even though it
 248          * should just have been converted to a normal huge page. This
 249          * does not leak memory, though, as the hugepage will be freed
 250          * once it is out of use. It also does not allow the counters to
 251          * go out of whack in adjust_pool_surplus() as we don't modify
 252          * the node values until we've gotten the hugepage and only the
 253          * per-node value is checked there.
 254          */
 255         spin_lock(&hugetlb_lock);
 256         if (surplus_huge_pages >= nr_overcommit_huge_pages) {
 257                 spin_unlock(&hugetlb_lock);
 258                 return NULL;
 259         } else {
 260                 nr_huge_pages++;
 261                 surplus_huge_pages++;
 262         }
 263         spin_unlock(&hugetlb_lock);
 264
 265         page = alloc_pages(htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 266                                         HUGETLB_PAGE_ORDER);
 267
 268         spin_lock(&hugetlb_lock);
 269         if (page) {
 270                 nid = page_to_nid(page);
 271                 set_compound_page_dtor(page, free_huge_page);
 272                 /*
 273                  * We incremented the global counters already
 274                  */
 275                 nr_huge_pages_node[nid]++;
 276                 surplus_huge_pages_node[nid]++;
 277         } else {
 278                 nr_huge_pages--;
 279                 surplus_huge_pages--;
 280         }
 281         spin_unlock(&hugetlb_lock);
 282
 283         return page;
 284 }
 285
 286 /*
 287  * Increase the hugetlb pool such that it can accomodate a reservation
 288  * of size 'delta'.
 289  */
 290 static int gather_surplus_pages(int delta)
 291 {
 292         struct list_head surplus_list;
 293         struct page *page, *tmp;
 294         int ret, i;
 295         int needed, allocated;
 296
 297         needed = (resv_huge_pages + delta) - free_huge_pages;
 298         if (needed <= 0)
 299                 return 0;
 300
 301         allocated = 0;
 302         INIT_LIST_HEAD(&surplus_list);
 303
 304         ret = -ENOMEM;
 305 retry:
 306         spin_unlock(&hugetlb_lock);
 307         for (i = 0; i < needed; i++) {
 308                 page = alloc_buddy_huge_page(NULL, 0);
 309                 if (!page) {
 310                         /*
 311                          * We were not able to allocate enough pages to
 312                          * satisfy the entire reservation so we free what
 313                          * we've allocated so far.
 314                          */
 315                         spin_lock(&hugetlb_lock);
 316                         needed = 0;
 317                         goto free;
 318                 }
 319
 320                 list_add(&page->lru, &surplus_list);
 321         }
 322         allocated += needed;
 323
 324         /*
 325          * After retaking hugetlb_lock, we need to recalculate 'needed'
 326          * because either resv_huge_pages or free_huge_pages may have changed.
 327          */
 328         spin_lock(&hugetlb_lock);
 329         needed = (resv_huge_pages + delta) - (free_huge_pages + allocated);
 330         if (needed > 0)
 331                 goto retry;
 332
 333         /*
 334          * The surplus_list now contains _at_least_ the number of extra pages
 335          * needed to accomodate the reservation.  Add the appropriate number
 336          * of pages to the hugetlb pool and free the extras back to the buddy
 337          * allocator.
 338          */
 339         needed += allocated;
 340         ret = 0;
 341 free:
 342         list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
 343                 list_del(&page->lru);
 344                 if ((--needed) >= 0)
 345                         enqueue_huge_page(page);
 346                 else {
 347                         /*
 348                          * Decrement the refcount and free the page using its
 349                          * destructor.  This must be done with hugetlb_lock
 350                          * unlocked which is safe because free_huge_page takes
 351                          * hugetlb_lock before deciding how to free the page.
 352                          */
 353                         spin_unlock(&hugetlb_lock);
 354                         put_page(page);
 355                         spin_lock(&hugetlb_lock);
 356                 }
 357         }
 358
 359         return ret;
 360 }
 361
 362 /*
 363  * When releasing a hugetlb pool reservation, any surplus pages that were
 364  * allocated to satisfy the reservation must be explicitly freed if they were
 365  * never used.
 366  */
 367 static void return_unused_surplus_pages(unsigned long unused_resv_pages)
 368 {
 369         static int nid = -1;
 370         struct page *page;
 371         unsigned long nr_pages;
 372
 373         nr_pages = min(unused_resv_pages, surplus_huge_pages);
 374
 375         while (nr_pages) {
 376                 nid = next_node(nid, node_online_map);
 377                 if (nid == MAX_NUMNODES)
 378                         nid = first_node(node_online_map);
 379
 380                 if (!surplus_huge_pages_node[nid])
 381                         continue;
 382
 383                 if (!list_empty(&hugepage_freelists[nid])) {
 384                         page = list_entry(hugepage_freelists[nid].next,
 385                                           struct page, lru);
 386                         list_del(&page->lru);
 387                         update_and_free_page(page);
 388                         free_huge_pages--;
 389                         free_huge_pages_node[nid]--;
 390                         surplus_huge_pages--;
 391                         surplus_huge_pages_node[nid]--;
 392                         nr_pages--;
 393                 }
 394         }
 395 }
 396
 397
 398 static struct page *alloc_huge_page_shared(struct vm_area_struct *vma,
 399                                                 unsigned long addr)
 400 {
 401         struct page *page;
 402
 403         spin_lock(&hugetlb_lock);
 404         page = dequeue_huge_page(vma, addr);
 405         spin_unlock(&hugetlb_lock);
 406         return page ? page : ERR_PTR(-VM_FAULT_OOM);
 407 }
 408
 409 static struct page *alloc_huge_page_private(struct vm_area_struct *vma,
 410                                                 unsigned long addr)
 411 {
 412         struct page *page = NULL;
 413
 414         if (hugetlb_get_quota(vma->vm_file->f_mapping, 1))
 415                 return ERR_PTR(-VM_FAULT_SIGBUS);
 416
 417         spin_lock(&hugetlb_lock);
 418         if (free_huge_pages > resv_huge_pages)
 419                 page = dequeue_huge_page(vma, addr);
 420         spin_unlock(&hugetlb_lock);
 421         if (!page) {
 422                 page = alloc_buddy_huge_page(vma, addr);
 423                 if (!page) {
 424                         hugetlb_put_quota(vma->vm_file->f_mapping, 1);
 425                         return ERR_PTR(-VM_FAULT_OOM);
 426                 }
 427         }
 428         return page;
 429 }
 430
 431 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 432                                     unsigned long addr)
 433 {
 434         struct page *page;
 435         struct address_space *mapping = vma->vm_file->f_mapping;
 436
 437         if (vma->vm_flags & VM_MAYSHARE)
 438                 page = alloc_huge_page_shared(vma, addr);
 439         else
 440                 page = alloc_huge_page_private(vma, addr);
 441
 442         if (!IS_ERR(page)) {
 443                 set_page_refcounted(page);
 444                 set_page_private(page, (unsigned long) mapping);
 445         }
 446         return page;
 447 }
 448
 449 static int __init hugetlb_init(void)
 450 {
 451         unsigned long i;
 452
 453         if (HPAGE_SHIFT == 0)
 454                 return 0;
 455
 456         for (i = 0; i < MAX_NUMNODES; ++i)
 457                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 458
 459         hugetlb_next_nid = first_node(node_online_map);
 460
 461         for (i = 0; i < max_huge_pages; ++i) {
 462                 if (!alloc_fresh_huge_page())
 463                         break;
 464         }
 465         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 466         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 467         return 0;
 468 }
 469 module_init(hugetlb_init);
 470
 471 static int __init hugetlb_setup(char *s)
 472 {
 473         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 474                 max_huge_pages = 0;
 475         return 1;
 476 }
 477 __setup("hugepages=", hugetlb_setup);
 478
 479 static unsigned int cpuset_mems_nr(unsigned int *array)
 480 {
 481         int node;
 482         unsigned int nr = 0;
 483
 484         for_each_node_mask(node, cpuset_current_mems_allowed)
 485                 nr += array[node];
 486
 487         return nr;
 488 }
 489
 490 #ifdef CONFIG_SYSCTL
 491 #ifdef CONFIG_HIGHMEM
 492 static void try_to_free_low(unsigned long count)
 493 {
 494         int i;
 495
 496         for (i = 0; i < MAX_NUMNODES; ++i) {
 497                 struct page *page, *next;
 498                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 499                         if (count >= nr_huge_pages)
 500                                 return;
 501                         if (PageHighMem(page))
 502                                 continue;
 503                         list_del(&page->lru);
 504                         update_and_free_page(page);
 505                         free_huge_pages--;
 506                         free_huge_pages_node[page_to_nid(page)]--;
 507                 }
 508         }
 509 }
 510 #else
 511 static inline void try_to_free_low(unsigned long count)
 512 {
 513 }
 514 #endif
 515
 516 #define persistent_huge_pages (nr_huge_pages - surplus_huge_pages)
 517 static unsigned long set_max_huge_pages(unsigned long count)
 518 {
 519         unsigned long min_count, ret;
 520
 521         /*
 522          * Increase the pool size
 523          * First take pages out of surplus state.  Then make up the
 524          * remaining difference by allocating fresh huge pages.
 525          *
 526          * We might race with alloc_buddy_huge_page() here and be unable
 527          * to convert a surplus huge page to a normal huge page. That is
 528          * not critical, though, it just means the overall size of the
 529          * pool might be one hugepage larger than it needs to be, but
 530          * within all the constraints specified by the sysctls.
 531          */
 532         spin_lock(&hugetlb_lock);
 533         while (surplus_huge_pages && count > persistent_huge_pages) {
 534                 if (!adjust_pool_surplus(-1))
 535                         break;
 536         }
 537
 538         while (count > persistent_huge_pages) {
 539                 int ret;
 540                 /*
 541                  * If this allocation races such that we no longer need the
 542                  * page, free_huge_page will handle it by freeing the page
 543                  * and reducing the surplus.
 544                  */
 545                 spin_unlock(&hugetlb_lock);
 546                 ret = alloc_fresh_huge_page();
 547                 spin_lock(&hugetlb_lock);
 548                 if (!ret)
 549                         goto out;
 550
 551         }
 552
 553         /*
 554          * Decrease the pool size
 555          * First return free pages to the buddy allocator (being careful
 556          * to keep enough around to satisfy reservations).  Then place
 557          * pages into surplus state as needed so the pool will shrink
 558          * to the desired size as pages become free.
 559          *
 560          * By placing pages into the surplus state independent of the
 561          * overcommit value, we are allowing the surplus pool size to
 562          * exceed overcommit. There are few sane options here. Since
 563          * alloc_buddy_huge_page() is checking the global counter,
 564          * though, we'll note that we're not allowed to exceed surplus
 565          * and won't grow the pool anywhere else. Not until one of the
 566          * sysctls are changed, or the surplus pages go out of use.
 567          */
 568         min_count = resv_huge_pages + nr_huge_pages - free_huge_pages;
 569         min_count = max(count, min_count);
 570         try_to_free_low(min_count);
 571         while (min_count < persistent_huge_pages) {
 572                 struct page *page = dequeue_huge_page(NULL, 0);
 573                 if (!page)
 574                         break;
 575                 update_and_free_page(page);
 576         }
 577         while (count < persistent_huge_pages) {
 578                 if (!adjust_pool_surplus(1))
 579                         break;
 580         }
 581 out:
 582         ret = persistent_huge_pages;
 583         spin_unlock(&hugetlb_lock);
 584         return ret;
 585 }
 586
 587 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 588                            struct file *file, void __user *buffer,
 589                            size_t *length, loff_t *ppos)
 590 {
 591         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 592         max_huge_pages = set_max_huge_pages(max_huge_pages);
 593         return 0;
 594 }
 595
 596 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 597                         struct file *file, void __user *buffer,
 598                         size_t *length, loff_t *ppos)
 599 {
 600         proc_dointvec(table, write, file, buffer, length, ppos);
 601         if (hugepages_treat_as_movable)
 602                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
 603         else
 604                 htlb_alloc_mask = GFP_HIGHUSER;
 605         return 0;
 606 }
 607
 608 #endif /* CONFIG_SYSCTL */
 609
 610 int hugetlb_report_meminfo(char *buf)
 611 {
 612         return sprintf(buf,
 613                         "HugePages_Total: %5lu\n"
 614                         "HugePages_Free:  %5lu\n"
 615                         "HugePages_Rsvd:  %5lu\n"
 616                         "HugePages_Surp:  %5lu\n"
 617                         "Hugepagesize:    %5lu kB\n",
 618                         nr_huge_pages,
 619                         free_huge_pages,
 620                         resv_huge_pages,
 621                         surplus_huge_pages,
 622                         HPAGE_SIZE/1024);
 623 }
 624
 625 int hugetlb_report_node_meminfo(int nid, char *buf)
 626 {
 627         return sprintf(buf,
 628                 "Node %d HugePages_Total: %5u\n"
 629                 "Node %d HugePages_Free:  %5u\n",
 630                 nid, nr_huge_pages_node[nid],
 631                 nid, free_huge_pages_node[nid]);
 632 }
 633
 634 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 635 unsigned long hugetlb_total_pages(void)
 636 {
 637         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 638 }
 639
 640 /*
 641  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 642  * handle_mm_fault() to try to instantiate regular-sized pages in the
 643  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 644  * this far.
 645  */
 646 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 647 {
 648         BUG();
 649         return 0;
 650 }
 651
 652 struct vm_operations_struct hugetlb_vm_ops = {
 653         .fault = hugetlb_vm_op_fault,
 654 };
 655
 656 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 657                                 int writable)
 658 {
 659         pte_t entry;
 660
 661         if (writable) {
 662                 entry =
 663                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 664         } else {
 665                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 666         }
 667         entry = pte_mkyoung(entry);
 668         entry = pte_mkhuge(entry);
 669
 670         return entry;
 671 }
 672
 673 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 674                                    unsigned long address, pte_t *ptep)
 675 {
 676         pte_t entry;
 677
 678         entry = pte_mkwrite(pte_mkdirty(*ptep));
 679         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
 680                 update_mmu_cache(vma, address, entry);
 681         }
 682 }
 683
 684
 685 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 686                             struct vm_area_struct *vma)
 687 {
 688         pte_t *src_pte, *dst_pte, entry;
 689         struct page *ptepage;
 690         unsigned long addr;
 691         int cow;
 692
 693         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 694
 695         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 696                 src_pte = huge_pte_offset(src, addr);
 697                 if (!src_pte)
 698                         continue;
 699                 dst_pte = huge_pte_alloc(dst, addr);
 700                 if (!dst_pte)
 701                         goto nomem;
 702
 703                 /* If the pagetables are shared don't copy or take references */
 704                 if (dst_pte == src_pte)
 705                         continue;
 706
 707                 spin_lock(&dst->page_table_lock);
 708                 spin_lock(&src->page_table_lock);
 709                 if (!pte_none(*src_pte)) {
 710                         if (cow)
 711                                 ptep_set_wrprotect(src, addr, src_pte);
 712                         entry = *src_pte;
 713                         ptepage = pte_page(entry);
 714                         get_page(ptepage);
 715                         set_huge_pte_at(dst, addr, dst_pte, entry);
 716                 }
 717                 spin_unlock(&src->page_table_lock);
 718                 spin_unlock(&dst->page_table_lock);
 719         }
 720         return 0;
 721
 722 nomem:
 723         return -ENOMEM;
 724 }
 725
 726 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 727                             unsigned long end)
 728 {
 729         struct mm_struct *mm = vma->vm_mm;
 730         unsigned long address;
 731         pte_t *ptep;
 732         pte_t pte;
 733         struct page *page;
 734         struct page *tmp;
 735         /*
 736          * A page gathering list, protected by per file i_mmap_lock. The
 737          * lock is used to avoid list corruption from multiple unmapping
 738          * of the same page since we are using page->lru.
 739          */
 740         LIST_HEAD(page_list);
 741
 742         WARN_ON(!is_vm_hugetlb_page(vma));
 743         BUG_ON(start & ~HPAGE_MASK);
 744         BUG_ON(end & ~HPAGE_MASK);
 745
 746         spin_lock(&mm->page_table_lock);
 747         for (address = start; address < end; address += HPAGE_SIZE) {
 748                 ptep = huge_pte_offset(mm, address);
 749                 if (!ptep)
 750                         continue;
 751
 752                 if (huge_pmd_unshare(mm, &address, ptep))
 753                         continue;
 754
 755                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 756                 if (pte_none(pte))
 757                         continue;
 758
 759                 page = pte_page(pte);
 760                 if (pte_dirty(pte))
 761                         set_page_dirty(page);
 762                 list_add(&page->lru, &page_list);
 763         }
 764         spin_unlock(&mm->page_table_lock);
 765         flush_tlb_range(vma, start, end);
 766         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 767                 list_del(&page->lru);
 768                 put_page(page);
 769         }
 770 }
 771
 772 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 773                           unsigned long end)
 774 {
 775         /*
 776          * It is undesirable to test vma->vm_file as it should be non-null
 777          * for valid hugetlb area. However, vm_file will be NULL in the error
 778          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 779          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 780          * to clean up. Since no pte has actually been setup, it is safe to
 781          * do nothing in this case.
 782          */
 783         if (vma->vm_file) {
 784                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 785                 __unmap_hugepage_range(vma, start, end);
 786                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 787         }
 788 }
 789
 790 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 791                         unsigned long address, pte_t *ptep, pte_t pte)
 792 {
 793         struct page *old_page, *new_page;
 794         int avoidcopy;
 795
 796         old_page = pte_page(pte);
 797
 798         /* If no-one else is actually using this page, avoid the copy
 799          * and just make the page writable */
 800         avoidcopy = (page_count(old_page) == 1);
 801         if (avoidcopy) {
 802                 set_huge_ptep_writable(vma, address, ptep);
 803                 return 0;
 804         }
 805
 806         page_cache_get(old_page);
 807         new_page = alloc_huge_page(vma, address);
 808
 809         if (IS_ERR(new_page)) {
 810                 page_cache_release(old_page);
 811                 return -PTR_ERR(new_page);
 812         }
 813
 814         spin_unlock(&mm->page_table_lock);
 815         copy_huge_page(new_page, old_page, address, vma);
 816         __SetPageUptodate(new_page);
 817         spin_lock(&mm->page_table_lock);
 818
 819         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 820         if (likely(pte_same(*ptep, pte))) {
 821                 /* Break COW */
 822                 set_huge_pte_at(mm, address, ptep,
 823                                 make_huge_pte(vma, new_page, 1));
 824                 /* Make the old page be freed below */
 825                 new_page = old_page;
 826         }
 827         page_cache_release(new_page);
 828         page_cache_release(old_page);
 829         return 0;
 830 }
 831
 832 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 833                         unsigned long address, pte_t *ptep, int write_access)
 834 {
 835         int ret = VM_FAULT_SIGBUS;
 836         unsigned long idx;
 837         unsigned long size;
 838         struct page *page;
 839         struct address_space *mapping;
 840         pte_t new_pte;
 841
 842         mapping = vma->vm_file->f_mapping;
 843         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 844                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 845
 846         /*
 847          * Use page lock to guard against racing truncation
 848          * before we get page_table_lock.
 849          */
 850 retry:
 851         page = find_lock_page(mapping, idx);
 852         if (!page) {
 853                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 854                 if (idx >= size)
 855                         goto out;
 856                 page = alloc_huge_page(vma, address);
 857                 if (IS_ERR(page)) {
 858                         ret = -PTR_ERR(page);
 859                         goto out;
 860                 }
 861                 clear_huge_page(page, address);
 862                 __SetPageUptodate(page);
 863
 864                 if (vma->vm_flags & VM_SHARED) {
 865                         int err;
 866                         struct inode *inode = mapping->host;
 867
 868                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 869                         if (err) {
 870                                 put_page(page);
 871                                 if (err == -EEXIST)
 872                                         goto retry;
 873                                 goto out;
 874                         }
 875
 876                         spin_lock(&inode->i_lock);
 877                         inode->i_blocks += BLOCKS_PER_HUGEPAGE;
 878                         spin_unlock(&inode->i_lock);
 879                 } else
 880                         lock_page(page);
 881         }
 882
 883         spin_lock(&mm->page_table_lock);
 884         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 885         if (idx >= size)
 886                 goto backout;
 887
 888         ret = 0;
 889         if (!pte_none(*ptep))
 890                 goto backout;
 891
 892         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 893                                 && (vma->vm_flags & VM_SHARED)));
 894         set_huge_pte_at(mm, address, ptep, new_pte);
 895
 896         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 897                 /* Optimization, do the COW without a second fault */
 898                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 899         }
 900
 901         spin_unlock(&mm->page_table_lock);
 902         unlock_page(page);
 903 out:
 904         return ret;
 905
 906 backout:
 907         spin_unlock(&mm->page_table_lock);
 908         unlock_page(page);
 909         put_page(page);
 910         goto out;
 911 }
 912
 913 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 914                         unsigned long address, int write_access)
 915 {
 916         pte_t *ptep;
 917         pte_t entry;
 918         int ret;
 919         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 920
 921         ptep = huge_pte_alloc(mm, address);
 922         if (!ptep)
 923                 return VM_FAULT_OOM;
 924
 925         /*
 926          * Serialize hugepage allocation and instantiation, so that we don't
 927          * get spurious allocation failures if two CPUs race to instantiate
 928          * the same page in the page cache.
 929          */
 930         mutex_lock(&hugetlb_instantiation_mutex);
 931         entry = *ptep;
 932         if (pte_none(entry)) {
 933                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 934                 mutex_unlock(&hugetlb_instantiation_mutex);
 935                 return ret;
 936         }
 937
 938         ret = 0;
 939
 940         spin_lock(&mm->page_table_lock);
 941         /* Check for a racing update before calling hugetlb_cow */
 942         if (likely(pte_same(entry, *ptep)))
 943                 if (write_access && !pte_write(entry))
 944                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 945         spin_unlock(&mm->page_table_lock);
 946         mutex_unlock(&hugetlb_instantiation_mutex);
 947
 948         return ret;
 949 }
 950
 951 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 952                         struct page **pages, struct vm_area_struct **vmas,
 953                         unsigned long *position, int *length, int i,
 954                         int write)
 955 {
 956         unsigned long pfn_offset;
 957         unsigned long vaddr = *position;
 958         int remainder = *length;
 959
 960         spin_lock(&mm->page_table_lock);
 961         while (vaddr < vma->vm_end && remainder) {
 962                 pte_t *pte;
 963                 struct page *page;
 964
 965                 /*
 966                  * Some archs (sparc64, sh*) have multiple pte_ts to
 967                  * each hugepage.  We have to make * sure we get the
 968                  * first, for the page indexing below to work.
 969                  */
 970                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 971
 972                 if (!pte || pte_none(*pte) || (write && !pte_write(*pte))) {
 973                         int ret;
 974
 975                         spin_unlock(&mm->page_table_lock);
 976                         ret = hugetlb_fault(mm, vma, vaddr, write);
 977                         spin_lock(&mm->page_table_lock);
 978                         if (!(ret & VM_FAULT_ERROR))
 979                                 continue;
 980
 981                         remainder = 0;
 982                         if (!i)
 983                                 i = -EFAULT;
 984                         break;
 985                 }
 986
 987                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 988                 page = pte_page(*pte);
 989 same_page:
 990                 if (pages) {
 991                         get_page(page);
 992                         pages[i] = page + pfn_offset;
 993                 }
 994
 995                 if (vmas)
 996                         vmas[i] = vma;
 997
 998                 vaddr += PAGE_SIZE;
 999                 ++pfn_offset;
1000                 --remainder;
1001                 ++i;
1002                 if (vaddr < vma->vm_end && remainder &&
1003                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
1004                         /*
1005                          * We use pfn_offset to avoid touching the pageframes
1006                          * of this compound page.
1007                          */
1008                         goto same_page;
1009                 }
1010         }
1011         spin_unlock(&mm->page_table_lock);
1012         *length = remainder;
1013         *position = vaddr;
1014
1015         return i;
1016 }
1017
1018 void hugetlb_change_protection(struct vm_area_struct *vma,
1019                 unsigned long address, unsigned long end, pgprot_t newprot)
1020 {
1021         struct mm_struct *mm = vma->vm_mm;
1022         unsigned long start = address;
1023         pte_t *ptep;
1024         pte_t pte;
1025
1026         BUG_ON(address >= end);
1027         flush_cache_range(vma, address, end);
1028
1029         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
1030         spin_lock(&mm->page_table_lock);
1031         for (; address < end; address += HPAGE_SIZE) {
1032                 ptep = huge_pte_offset(mm, address);
1033                 if (!ptep)
1034                         continue;
1035                 if (huge_pmd_unshare(mm, &address, ptep))
1036                         continue;
1037                 if (!pte_none(*ptep)) {
1038                         pte = huge_ptep_get_and_clear(mm, address, ptep);
1039                         pte = pte_mkhuge(pte_modify(pte, newprot));
1040                         set_huge_pte_at(mm, address, ptep, pte);
1041                 }
1042         }
1043         spin_unlock(&mm->page_table_lock);
1044         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
1045
1046         flush_tlb_range(vma, start, end);
1047 }
1048
1049 struct file_region {
1050         struct list_head link;
1051         long from;
1052         long to;
1053 };
1054
1055 static long region_add(struct list_head *head, long f, long t)
1056 {
1057         struct file_region *rg, *nrg, *trg;
1058
1059         /* Locate the region we are either in or before. */
1060         list_for_each_entry(rg, head, link)
1061                 if (f <= rg->to)
1062                         break;
1063
1064         /* Round our left edge to the current segment if it encloses us. */
1065         if (f > rg->from)
1066                 f = rg->from;
1067
1068         /* Check for and consume any regions we now overlap with. */
1069         nrg = rg;
1070         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1071                 if (&rg->link == head)
1072                         break;
1073                 if (rg->from > t)
1074                         break;
1075
1076                 /* If this area reaches higher then extend our area to
1077                  * include it completely.  If this is not the first area
1078                  * which we intend to reuse, free it. */
1079                 if (rg->to > t)
1080                         t = rg->to;
1081                 if (rg != nrg) {
1082                         list_del(&rg->link);
1083                         kfree(rg);
1084                 }
1085         }
1086         nrg->from = f;
1087         nrg->to = t;
1088         return 0;
1089 }
1090
1091 static long region_chg(struct list_head *head, long f, long t)
1092 {
1093         struct file_region *rg, *nrg;
1094         long chg = 0;
1095
1096         /* Locate the region we are before or in. */
1097         list_for_each_entry(rg, head, link)
1098                 if (f <= rg->to)
1099                         break;
1100
1101         /* If we are below the current region then a new region is required.
1102          * Subtle, allocate a new region at the position but make it zero
1103          * size such that we can guarantee to record the reservation. */
1104         if (&rg->link == head || t < rg->from) {
1105                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
1106                 if (!nrg)
1107                         return -ENOMEM;
1108                 nrg->from = f;
1109                 nrg->to   = f;
1110                 INIT_LIST_HEAD(&nrg->link);
1111                 list_add(&nrg->link, rg->link.prev);
1112
1113                 return t - f;
1114         }
1115
1116         /* Round our left edge to the current segment if it encloses us. */
1117         if (f > rg->from)
1118                 f = rg->from;
1119         chg = t - f;
1120
1121         /* Check for and consume any regions we now overlap with. */
1122         list_for_each_entry(rg, rg->link.prev, link) {
1123                 if (&rg->link == head)
1124                         break;
1125                 if (rg->from > t)
1126                         return chg;
1127
1128                 /* We overlap with this area, if it extends futher than
1129                  * us then we must extend ourselves.  Account for its
1130                  * existing reservation. */
1131                 if (rg->to > t) {
1132                         chg += rg->to - t;
1133                         t = rg->to;
1134                 }
1135                 chg -= rg->to - rg->from;
1136         }
1137         return chg;
1138 }
1139
1140 static long region_truncate(struct list_head *head, long end)
1141 {
1142         struct file_region *rg, *trg;
1143         long chg = 0;
1144
1145         /* Locate the region we are either in or before. */
1146         list_for_each_entry(rg, head, link)
1147                 if (end <= rg->to)
1148                         break;
1149         if (&rg->link == head)
1150                 return 0;
1151
1152         /* If we are in the middle of a region then adjust it. */
1153         if (end > rg->from) {
1154                 chg = rg->to - end;
1155                 rg->to = end;
1156                 rg = list_entry(rg->link.next, typeof(*rg), link);
1157         }
1158
1159         /* Drop any remaining regions. */
1160         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1161                 if (&rg->link == head)
1162                         break;
1163                 chg += rg->to - rg->from;
1164                 list_del(&rg->link);
1165                 kfree(rg);
1166         }
1167         return chg;
1168 }
1169
1170 static int hugetlb_acct_memory(long delta)
1171 {
1172         int ret = -ENOMEM;
1173
1174         spin_lock(&hugetlb_lock);
1175         /*
1176          * When cpuset is configured, it breaks the strict hugetlb page
1177          * reservation as the accounting is done on a global variable. Such
1178          * reservation is completely rubbish in the presence of cpuset because
1179          * the reservation is not checked against page availability for the
1180          * current cpuset. Application can still potentially OOM'ed by kernel
1181          * with lack of free htlb page in cpuset that the task is in.
1182          * Attempt to enforce strict accounting with cpuset is almost
1183          * impossible (or too ugly) because cpuset is too fluid that
1184          * task or memory node can be dynamically moved between cpusets.
1185          *
1186          * The change of semantics for shared hugetlb mapping with cpuset is
1187          * undesirable. However, in order to preserve some of the semantics,
1188          * we fall back to check against current free page availability as
1189          * a best attempt and hopefully to minimize the impact of changing
1190          * semantics that cpuset has.
1191          */
1192         if (delta > 0) {
1193                 if (gather_surplus_pages(delta) < 0)
1194                         goto out;
1195
1196                 if (delta > cpuset_mems_nr(free_huge_pages_node))
1197                         goto out;
1198         }
1199
1200         ret = 0;
1201         resv_huge_pages += delta;
1202         if (delta < 0)
1203                 return_unused_surplus_pages((unsigned long) -delta);
1204
1205 out:
1206         spin_unlock(&hugetlb_lock);
1207         return ret;
1208 }
1209
1210 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
1211 {
1212         long ret, chg;
1213
1214         chg = region_chg(&inode->i_mapping->private_list, from, to);
1215         if (chg < 0)
1216                 return chg;
1217
1218         if (hugetlb_get_quota(inode->i_mapping, chg))
1219                 return -ENOSPC;
1220         ret = hugetlb_acct_memory(chg);
1221         if (ret < 0) {
1222                 hugetlb_put_quota(inode->i_mapping, chg);
1223                 return ret;
1224         }
1225         region_add(&inode->i_mapping->private_list, from, to);
1226         return 0;
1227 }
1228
1229 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
1230 {
1231         long chg = region_truncate(&inode->i_mapping->private_list, offset);
1232
1233         spin_lock(&inode->i_lock);
1234         inode->i_blocks -= BLOCKS_PER_HUGEPAGE * freed;
1235         spin_unlock(&inode->i_lock);
1236
1237         hugetlb_put_quota(inode->i_mapping, (chg - freed));
1238         hugetlb_acct_memory(-(chg - freed));
1239 }