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   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, reserved_huge_pages;
  26 unsigned long max_huge_pages;
  27 static struct list_head hugepage_freelists[MAX_NUMNODES];
  28 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  29 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  30 /*
  31  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  32  */
  33 static DEFINE_SPINLOCK(hugetlb_lock);
  34
  35 static void clear_huge_page(struct page *page, unsigned long addr)
  36 {
  37         int i;
  38
  39         might_sleep();
  40         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  41                 cond_resched();
  42                 clear_user_highpage(page + i, addr);
  43         }
  44 }
  45
  46 static void copy_huge_page(struct page *dst, struct page *src,
  47                            unsigned long addr)
  48 {
  49         int i;
  50
  51         might_sleep();
  52         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  53                 cond_resched();
  54                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE);
  55         }
  56 }
  57
  58 static void enqueue_huge_page(struct page *page)
  59 {
  60         int nid = page_to_nid(page);
  61         list_add(&page->lru, &hugepage_freelists[nid]);
  62         free_huge_pages++;
  63         free_huge_pages_node[nid]++;
  64 }
  65
  66 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  67                                 unsigned long address)
  68 {
  69         int nid = numa_node_id();
  70         struct page *page = NULL;
  71         struct zonelist *zonelist = huge_zonelist(vma, address);
  72         struct zone **z;
  73
  74         for (z = zonelist->zones; *z; z++) {
  75                 nid = (*z)->zone_pgdat->node_id;
  76                 if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
  77                     !list_empty(&hugepage_freelists[nid]))
  78                         break;
  79         }
  80
  81         if (*z) {
  82                 page = list_entry(hugepage_freelists[nid].next,
  83                                   struct page, lru);
  84                 list_del(&page->lru);
  85                 free_huge_pages--;
  86                 free_huge_pages_node[nid]--;
  87         }
  88         return page;
  89 }
  90
  91 static void free_huge_page(struct page *page)
  92 {
  93         BUG_ON(page_count(page));
  94
  95         INIT_LIST_HEAD(&page->lru);
  96
  97         spin_lock(&hugetlb_lock);
  98         enqueue_huge_page(page);
  99         spin_unlock(&hugetlb_lock);
 100 }
 101
 102 static int alloc_fresh_huge_page(void)
 103 {
 104         static int nid = 0;
 105         struct page *page;
 106         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
 107                                         HUGETLB_PAGE_ORDER);
 108         nid = (nid + 1) % num_online_nodes();
 109         if (page) {
 110                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
 111                 spin_lock(&hugetlb_lock);
 112                 nr_huge_pages++;
 113                 nr_huge_pages_node[page_to_nid(page)]++;
 114                 spin_unlock(&hugetlb_lock);
 115                 put_page(page); /* free it into the hugepage allocator */
 116                 return 1;
 117         }
 118         return 0;
 119 }
 120
 121 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 122                                     unsigned long addr)
 123 {
 124         struct inode *inode = vma->vm_file->f_dentry->d_inode;
 125         struct page *page;
 126         int use_reserve = 0;
 127         unsigned long idx;
 128
 129         spin_lock(&hugetlb_lock);
 130
 131         if (vma->vm_flags & VM_MAYSHARE) {
 132
 133                 /* idx = radix tree index, i.e. offset into file in
 134                  * HPAGE_SIZE units */
 135                 idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
 136                         + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 137
 138                 /* The hugetlbfs specific inode info stores the number
 139                  * of "guaranteed available" (huge) pages.  That is,
 140                  * the first 'prereserved_hpages' pages of the inode
 141                  * are either already instantiated, or have been
 142                  * pre-reserved (by hugetlb_reserve_for_inode()). Here
 143                  * we're in the process of instantiating the page, so
 144                  * we use this to determine whether to draw from the
 145                  * pre-reserved pool or the truly free pool. */
 146                 if (idx < HUGETLBFS_I(inode)->prereserved_hpages)
 147                         use_reserve = 1;
 148         }
 149
 150         if (!use_reserve) {
 151                 if (free_huge_pages <= reserved_huge_pages)
 152                         goto fail;
 153         } else {
 154                 BUG_ON(reserved_huge_pages == 0);
 155                 reserved_huge_pages--;
 156         }
 157
 158         page = dequeue_huge_page(vma, addr);
 159         if (!page)
 160                 goto fail;
 161
 162         spin_unlock(&hugetlb_lock);
 163         set_page_refcounted(page);
 164         return page;
 165
 166  fail:
 167         WARN_ON(use_reserve); /* reserved allocations shouldn't fail */
 168         spin_unlock(&hugetlb_lock);
 169         return NULL;
 170 }
 171
 172 /* hugetlb_extend_reservation()
 173  *
 174  * Ensure that at least 'atleast' hugepages are, and will remain,
 175  * available to instantiate the first 'atleast' pages of the given
 176  * inode.  If the inode doesn't already have this many pages reserved
 177  * or instantiated, set aside some hugepages in the reserved pool to
 178  * satisfy later faults (or fail now if there aren't enough, rather
 179  * than getting the SIGBUS later).
 180  */
 181 int hugetlb_extend_reservation(struct hugetlbfs_inode_info *info,
 182                                unsigned long atleast)
 183 {
 184         struct inode *inode = &info->vfs_inode;
 185         unsigned long change_in_reserve = 0;
 186         int ret = 0;
 187
 188         spin_lock(&hugetlb_lock);
 189         read_lock_irq(&inode->i_mapping->tree_lock);
 190
 191         if (info->prereserved_hpages >= atleast)
 192                 goto out;
 193
 194         /* Because we always call this on shared mappings, none of the
 195          * pages beyond info->prereserved_hpages can have been
 196          * instantiated, so we need to reserve all of them now. */
 197         change_in_reserve = atleast - info->prereserved_hpages;
 198
 199         if ((reserved_huge_pages + change_in_reserve) > free_huge_pages) {
 200                 ret = -ENOMEM;
 201                 goto out;
 202         }
 203
 204         reserved_huge_pages += change_in_reserve;
 205         info->prereserved_hpages = atleast;
 206
 207  out:
 208         read_unlock_irq(&inode->i_mapping->tree_lock);
 209         spin_unlock(&hugetlb_lock);
 210
 211         return ret;
 212 }
 213
 214 /* hugetlb_truncate_reservation()
 215  *
 216  * This returns pages reserved for the given inode to the general free
 217  * hugepage pool.  If the inode has any pages prereserved, but not
 218  * instantiated, beyond offset (atmost << HPAGE_SIZE), then release
 219  * them.
 220  */
 221 void hugetlb_truncate_reservation(struct hugetlbfs_inode_info *info,
 222                                   unsigned long atmost)
 223 {
 224         struct inode *inode = &info->vfs_inode;
 225         struct address_space *mapping = inode->i_mapping;
 226         unsigned long idx;
 227         unsigned long change_in_reserve = 0;
 228         struct page *page;
 229
 230         spin_lock(&hugetlb_lock);
 231         read_lock_irq(&inode->i_mapping->tree_lock);
 232
 233         if (info->prereserved_hpages <= atmost)
 234                 goto out;
 235
 236         /* Count pages which were reserved, but not instantiated, and
 237          * which we can now release. */
 238         for (idx = atmost; idx < info->prereserved_hpages; idx++) {
 239                 page = radix_tree_lookup(&mapping->page_tree, idx);
 240                 if (!page)
 241                         /* Pages which are already instantiated can't
 242                          * be unreserved (and in fact have already
 243                          * been removed from the reserved pool) */
 244                         change_in_reserve++;
 245         }
 246
 247         BUG_ON(reserved_huge_pages < change_in_reserve);
 248         reserved_huge_pages -= change_in_reserve;
 249         info->prereserved_hpages = atmost;
 250
 251  out:
 252         read_unlock_irq(&inode->i_mapping->tree_lock);
 253         spin_unlock(&hugetlb_lock);
 254 }
 255
 256 static int __init hugetlb_init(void)
 257 {
 258         unsigned long i;
 259
 260         if (HPAGE_SHIFT == 0)
 261                 return 0;
 262
 263         for (i = 0; i < MAX_NUMNODES; ++i)
 264                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 265
 266         for (i = 0; i < max_huge_pages; ++i) {
 267                 if (!alloc_fresh_huge_page())
 268                         break;
 269         }
 270         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 271         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 272         return 0;
 273 }
 274 module_init(hugetlb_init);
 275
 276 static int __init hugetlb_setup(char *s)
 277 {
 278         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 279                 max_huge_pages = 0;
 280         return 1;
 281 }
 282 __setup("hugepages=", hugetlb_setup);
 283
 284 #ifdef CONFIG_SYSCTL
 285 static void update_and_free_page(struct page *page)
 286 {
 287         int i;
 288         nr_huge_pages--;
 289         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 290         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 291                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 292                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 293                                 1 << PG_private | 1<< PG_writeback);
 294         }
 295         page[1].lru.next = NULL;
 296         set_page_refcounted(page);
 297         __free_pages(page, HUGETLB_PAGE_ORDER);
 298 }
 299
 300 #ifdef CONFIG_HIGHMEM
 301 static void try_to_free_low(unsigned long count)
 302 {
 303         int i, nid;
 304         for (i = 0; i < MAX_NUMNODES; ++i) {
 305                 struct page *page, *next;
 306                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 307                         if (PageHighMem(page))
 308                                 continue;
 309                         list_del(&page->lru);
 310                         update_and_free_page(page);
 311                         nid = page_zone(page)->zone_pgdat->node_id;
 312                         free_huge_pages--;
 313                         free_huge_pages_node[nid]--;
 314                         if (count >= nr_huge_pages)
 315                                 return;
 316                 }
 317         }
 318 }
 319 #else
 320 static inline void try_to_free_low(unsigned long count)
 321 {
 322 }
 323 #endif
 324
 325 static unsigned long set_max_huge_pages(unsigned long count)
 326 {
 327         while (count > nr_huge_pages) {
 328                 if (!alloc_fresh_huge_page())
 329                         return nr_huge_pages;
 330         }
 331         if (count >= nr_huge_pages)
 332                 return nr_huge_pages;
 333
 334         spin_lock(&hugetlb_lock);
 335         try_to_free_low(count);
 336         while (count < nr_huge_pages) {
 337                 struct page *page = dequeue_huge_page(NULL, 0);
 338                 if (!page)
 339                         break;
 340                 update_and_free_page(page);
 341         }
 342         spin_unlock(&hugetlb_lock);
 343         return nr_huge_pages;
 344 }
 345
 346 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 347                            struct file *file, void __user *buffer,
 348                            size_t *length, loff_t *ppos)
 349 {
 350         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 351         max_huge_pages = set_max_huge_pages(max_huge_pages);
 352         return 0;
 353 }
 354 #endif /* CONFIG_SYSCTL */
 355
 356 int hugetlb_report_meminfo(char *buf)
 357 {
 358         return sprintf(buf,
 359                         "HugePages_Total: %5lu\n"
 360                         "HugePages_Free:  %5lu\n"
 361                         "HugePages_Rsvd:  %5lu\n"
 362                         "Hugepagesize:    %5lu kB\n",
 363                         nr_huge_pages,
 364                         free_huge_pages,
 365                         reserved_huge_pages,
 366                         HPAGE_SIZE/1024);
 367 }
 368
 369 int hugetlb_report_node_meminfo(int nid, char *buf)
 370 {
 371         return sprintf(buf,
 372                 "Node %d HugePages_Total: %5u\n"
 373                 "Node %d HugePages_Free:  %5u\n",
 374                 nid, nr_huge_pages_node[nid],
 375                 nid, free_huge_pages_node[nid]);
 376 }
 377
 378 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 379 unsigned long hugetlb_total_pages(void)
 380 {
 381         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 382 }
 383
 384 /*
 385  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 386  * handle_mm_fault() to try to instantiate regular-sized pages in the
 387  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 388  * this far.
 389  */
 390 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 391                                 unsigned long address, int *unused)
 392 {
 393         BUG();
 394         return NULL;
 395 }
 396
 397 struct vm_operations_struct hugetlb_vm_ops = {
 398         .nopage = hugetlb_nopage,
 399 };
 400
 401 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 402                                 int writable)
 403 {
 404         pte_t entry;
 405
 406         if (writable) {
 407                 entry =
 408                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 409         } else {
 410                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 411         }
 412         entry = pte_mkyoung(entry);
 413         entry = pte_mkhuge(entry);
 414
 415         return entry;
 416 }
 417
 418 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 419                                    unsigned long address, pte_t *ptep)
 420 {
 421         pte_t entry;
 422
 423         entry = pte_mkwrite(pte_mkdirty(*ptep));
 424         ptep_set_access_flags(vma, address, ptep, entry, 1);
 425         update_mmu_cache(vma, address, entry);
 426         lazy_mmu_prot_update(entry);
 427 }
 428
 429
 430 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 431                             struct vm_area_struct *vma)
 432 {
 433         pte_t *src_pte, *dst_pte, entry;
 434         struct page *ptepage;
 435         unsigned long addr;
 436         int cow;
 437
 438         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 439
 440         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 441                 src_pte = huge_pte_offset(src, addr);
 442                 if (!src_pte)
 443                         continue;
 444                 dst_pte = huge_pte_alloc(dst, addr);
 445                 if (!dst_pte)
 446                         goto nomem;
 447                 spin_lock(&dst->page_table_lock);
 448                 spin_lock(&src->page_table_lock);
 449                 if (!pte_none(*src_pte)) {
 450                         if (cow)
 451                                 ptep_set_wrprotect(src, addr, src_pte);
 452                         entry = *src_pte;
 453                         ptepage = pte_page(entry);
 454                         get_page(ptepage);
 455                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 456                         set_huge_pte_at(dst, addr, dst_pte, entry);
 457                 }
 458                 spin_unlock(&src->page_table_lock);
 459                 spin_unlock(&dst->page_table_lock);
 460         }
 461         return 0;
 462
 463 nomem:
 464         return -ENOMEM;
 465 }
 466
 467 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 468                           unsigned long end)
 469 {
 470         struct mm_struct *mm = vma->vm_mm;
 471         unsigned long address;
 472         pte_t *ptep;
 473         pte_t pte;
 474         struct page *page;
 475
 476         WARN_ON(!is_vm_hugetlb_page(vma));
 477         BUG_ON(start & ~HPAGE_MASK);
 478         BUG_ON(end & ~HPAGE_MASK);
 479
 480         spin_lock(&mm->page_table_lock);
 481
 482         /* Update high watermark before we lower rss */
 483         update_hiwater_rss(mm);
 484
 485         for (address = start; address < end; address += HPAGE_SIZE) {
 486                 ptep = huge_pte_offset(mm, address);
 487                 if (!ptep)
 488                         continue;
 489
 490                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 491                 if (pte_none(pte))
 492                         continue;
 493
 494                 page = pte_page(pte);
 495                 put_page(page);
 496                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 497         }
 498
 499         spin_unlock(&mm->page_table_lock);
 500         flush_tlb_range(vma, start, end);
 501 }
 502
 503 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 504                         unsigned long address, pte_t *ptep, pte_t pte)
 505 {
 506         struct page *old_page, *new_page;
 507         int avoidcopy;
 508
 509         old_page = pte_page(pte);
 510
 511         /* If no-one else is actually using this page, avoid the copy
 512          * and just make the page writable */
 513         avoidcopy = (page_count(old_page) == 1);
 514         if (avoidcopy) {
 515                 set_huge_ptep_writable(vma, address, ptep);
 516                 return VM_FAULT_MINOR;
 517         }
 518
 519         page_cache_get(old_page);
 520         new_page = alloc_huge_page(vma, address);
 521
 522         if (!new_page) {
 523                 page_cache_release(old_page);
 524                 return VM_FAULT_OOM;
 525         }
 526
 527         spin_unlock(&mm->page_table_lock);
 528         copy_huge_page(new_page, old_page, address);
 529         spin_lock(&mm->page_table_lock);
 530
 531         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 532         if (likely(pte_same(*ptep, pte))) {
 533                 /* Break COW */
 534                 set_huge_pte_at(mm, address, ptep,
 535                                 make_huge_pte(vma, new_page, 1));
 536                 /* Make the old page be freed below */
 537                 new_page = old_page;
 538         }
 539         page_cache_release(new_page);
 540         page_cache_release(old_page);
 541         return VM_FAULT_MINOR;
 542 }
 543
 544 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 545                         unsigned long address, pte_t *ptep, int write_access)
 546 {
 547         int ret = VM_FAULT_SIGBUS;
 548         unsigned long idx;
 549         unsigned long size;
 550         struct page *page;
 551         struct address_space *mapping;
 552         pte_t new_pte;
 553
 554         mapping = vma->vm_file->f_mapping;
 555         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 556                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 557
 558         /*
 559          * Use page lock to guard against racing truncation
 560          * before we get page_table_lock.
 561          */
 562 retry:
 563         page = find_lock_page(mapping, idx);
 564         if (!page) {
 565                 if (hugetlb_get_quota(mapping))
 566                         goto out;
 567                 page = alloc_huge_page(vma, address);
 568                 if (!page) {
 569                         hugetlb_put_quota(mapping);
 570                         ret = VM_FAULT_OOM;
 571                         goto out;
 572                 }
 573                 clear_huge_page(page, address);
 574
 575                 if (vma->vm_flags & VM_SHARED) {
 576                         int err;
 577
 578                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 579                         if (err) {
 580                                 put_page(page);
 581                                 hugetlb_put_quota(mapping);
 582                                 if (err == -EEXIST)
 583                                         goto retry;
 584                                 goto out;
 585                         }
 586                 } else
 587                         lock_page(page);
 588         }
 589
 590         spin_lock(&mm->page_table_lock);
 591         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 592         if (idx >= size)
 593                 goto backout;
 594
 595         ret = VM_FAULT_MINOR;
 596         if (!pte_none(*ptep))
 597                 goto backout;
 598
 599         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 600         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 601                                 && (vma->vm_flags & VM_SHARED)));
 602         set_huge_pte_at(mm, address, ptep, new_pte);
 603
 604         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 605                 /* Optimization, do the COW without a second fault */
 606                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 607         }
 608
 609         spin_unlock(&mm->page_table_lock);
 610         unlock_page(page);
 611 out:
 612         return ret;
 613
 614 backout:
 615         spin_unlock(&mm->page_table_lock);
 616         hugetlb_put_quota(mapping);
 617         unlock_page(page);
 618         put_page(page);
 619         goto out;
 620 }
 621
 622 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 623                         unsigned long address, int write_access)
 624 {
 625         pte_t *ptep;
 626         pte_t entry;
 627         int ret;
 628         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 629
 630         ptep = huge_pte_alloc(mm, address);
 631         if (!ptep)
 632                 return VM_FAULT_OOM;
 633
 634         /*
 635          * Serialize hugepage allocation and instantiation, so that we don't
 636          * get spurious allocation failures if two CPUs race to instantiate
 637          * the same page in the page cache.
 638          */
 639         mutex_lock(&hugetlb_instantiation_mutex);
 640         entry = *ptep;
 641         if (pte_none(entry)) {
 642                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 643                 mutex_unlock(&hugetlb_instantiation_mutex);
 644                 return ret;
 645         }
 646
 647         ret = VM_FAULT_MINOR;
 648
 649         spin_lock(&mm->page_table_lock);
 650         /* Check for a racing update before calling hugetlb_cow */
 651         if (likely(pte_same(entry, *ptep)))
 652                 if (write_access && !pte_write(entry))
 653                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 654         spin_unlock(&mm->page_table_lock);
 655         mutex_unlock(&hugetlb_instantiation_mutex);
 656
 657         return ret;
 658 }
 659
 660 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 661                         struct page **pages, struct vm_area_struct **vmas,
 662                         unsigned long *position, int *length, int i)
 663 {
 664         unsigned long vpfn, vaddr = *position;
 665         int remainder = *length;
 666
 667         vpfn = vaddr/PAGE_SIZE;
 668         spin_lock(&mm->page_table_lock);
 669         while (vaddr < vma->vm_end && remainder) {
 670                 pte_t *pte;
 671                 struct page *page;
 672
 673                 /*
 674                  * Some archs (sparc64, sh*) have multiple pte_ts to
 675                  * each hugepage.  We have to make * sure we get the
 676                  * first, for the page indexing below to work.
 677                  */
 678                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 679
 680                 if (!pte || pte_none(*pte)) {
 681                         int ret;
 682
 683                         spin_unlock(&mm->page_table_lock);
 684                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 685                         spin_lock(&mm->page_table_lock);
 686                         if (ret == VM_FAULT_MINOR)
 687                                 continue;
 688
 689                         remainder = 0;
 690                         if (!i)
 691                                 i = -EFAULT;
 692                         break;
 693                 }
 694
 695                 if (pages) {
 696                         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 697                         get_page(page);
 698                         pages[i] = page;
 699                 }
 700
 701                 if (vmas)
 702                         vmas[i] = vma;
 703
 704                 vaddr += PAGE_SIZE;
 705                 ++vpfn;
 706                 --remainder;
 707                 ++i;
 708         }
 709         spin_unlock(&mm->page_table_lock);
 710         *length = remainder;
 711         *position = vaddr;
 712
 713         return i;
 714 }
 715
 716 void hugetlb_change_protection(struct vm_area_struct *vma,
 717                 unsigned long address, unsigned long end, pgprot_t newprot)
 718 {
 719         struct mm_struct *mm = vma->vm_mm;
 720         unsigned long start = address;
 721         pte_t *ptep;
 722         pte_t pte;
 723
 724         BUG_ON(address >= end);
 725         flush_cache_range(vma, address, end);
 726
 727         spin_lock(&mm->page_table_lock);
 728         for (; address < end; address += HPAGE_SIZE) {
 729                 ptep = huge_pte_offset(mm, address);
 730                 if (!ptep)
 731                         continue;
 732                 if (!pte_none(*ptep)) {
 733                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 734                         pte = pte_mkhuge(pte_modify(pte, newprot));
 735                         set_huge_pte_at(mm, address, ptep, pte);
 736                         lazy_mmu_prot_update(pte);
 737                 }
 738         }
 739         spin_unlock(&mm->page_table_lock);
 740
 741         flush_tlb_range(vma, start, end);
 742 }
 743