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, 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 = next_node(nid, node_online_map);
 109         if (nid == MAX_NUMNODES)
 110                 nid = first_node(node_online_map);
 111         if (page) {
 112                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
 113                 spin_lock(&hugetlb_lock);
 114                 nr_huge_pages++;
 115                 nr_huge_pages_node[page_to_nid(page)]++;
 116                 spin_unlock(&hugetlb_lock);
 117                 put_page(page); /* free it into the hugepage allocator */
 118                 return 1;
 119         }
 120         return 0;
 121 }
 122
 123 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 124                                     unsigned long addr)
 125 {
 126         struct inode *inode = vma->vm_file->f_dentry->d_inode;
 127         struct page *page;
 128         int use_reserve = 0;
 129         unsigned long idx;
 130
 131         spin_lock(&hugetlb_lock);
 132
 133         if (vma->vm_flags & VM_MAYSHARE) {
 134
 135                 /* idx = radix tree index, i.e. offset into file in
 136                  * HPAGE_SIZE units */
 137                 idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
 138                         + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 139
 140                 /* The hugetlbfs specific inode info stores the number
 141                  * of "guaranteed available" (huge) pages.  That is,
 142                  * the first 'prereserved_hpages' pages of the inode
 143                  * are either already instantiated, or have been
 144                  * pre-reserved (by hugetlb_reserve_for_inode()). Here
 145                  * we're in the process of instantiating the page, so
 146                  * we use this to determine whether to draw from the
 147                  * pre-reserved pool or the truly free pool. */
 148                 if (idx < HUGETLBFS_I(inode)->prereserved_hpages)
 149                         use_reserve = 1;
 150         }
 151
 152         if (!use_reserve) {
 153                 if (free_huge_pages <= reserved_huge_pages)
 154                         goto fail;
 155         } else {
 156                 BUG_ON(reserved_huge_pages == 0);
 157                 reserved_huge_pages--;
 158         }
 159
 160         page = dequeue_huge_page(vma, addr);
 161         if (!page)
 162                 goto fail;
 163
 164         spin_unlock(&hugetlb_lock);
 165         set_page_refcounted(page);
 166         return page;
 167
 168  fail:
 169         WARN_ON(use_reserve); /* reserved allocations shouldn't fail */
 170         spin_unlock(&hugetlb_lock);
 171         return NULL;
 172 }
 173
 174 /* hugetlb_extend_reservation()
 175  *
 176  * Ensure that at least 'atleast' hugepages are, and will remain,
 177  * available to instantiate the first 'atleast' pages of the given
 178  * inode.  If the inode doesn't already have this many pages reserved
 179  * or instantiated, set aside some hugepages in the reserved pool to
 180  * satisfy later faults (or fail now if there aren't enough, rather
 181  * than getting the SIGBUS later).
 182  */
 183 int hugetlb_extend_reservation(struct hugetlbfs_inode_info *info,
 184                                unsigned long atleast)
 185 {
 186         struct inode *inode = &info->vfs_inode;
 187         unsigned long change_in_reserve = 0;
 188         int ret = 0;
 189
 190         spin_lock(&hugetlb_lock);
 191         read_lock_irq(&inode->i_mapping->tree_lock);
 192
 193         if (info->prereserved_hpages >= atleast)
 194                 goto out;
 195
 196         /* Because we always call this on shared mappings, none of the
 197          * pages beyond info->prereserved_hpages can have been
 198          * instantiated, so we need to reserve all of them now. */
 199         change_in_reserve = atleast - info->prereserved_hpages;
 200
 201         if ((reserved_huge_pages + change_in_reserve) > free_huge_pages) {
 202                 ret = -ENOMEM;
 203                 goto out;
 204         }
 205
 206         reserved_huge_pages += change_in_reserve;
 207         info->prereserved_hpages = atleast;
 208
 209  out:
 210         read_unlock_irq(&inode->i_mapping->tree_lock);
 211         spin_unlock(&hugetlb_lock);
 212
 213         return ret;
 214 }
 215
 216 /* hugetlb_truncate_reservation()
 217  *
 218  * This returns pages reserved for the given inode to the general free
 219  * hugepage pool.  If the inode has any pages prereserved, but not
 220  * instantiated, beyond offset (atmost << HPAGE_SIZE), then release
 221  * them.
 222  */
 223 void hugetlb_truncate_reservation(struct hugetlbfs_inode_info *info,
 224                                   unsigned long atmost)
 225 {
 226         struct inode *inode = &info->vfs_inode;
 227         struct address_space *mapping = inode->i_mapping;
 228         unsigned long idx;
 229         unsigned long change_in_reserve = 0;
 230         struct page *page;
 231
 232         spin_lock(&hugetlb_lock);
 233         read_lock_irq(&inode->i_mapping->tree_lock);
 234
 235         if (info->prereserved_hpages <= atmost)
 236                 goto out;
 237
 238         /* Count pages which were reserved, but not instantiated, and
 239          * which we can now release. */
 240         for (idx = atmost; idx < info->prereserved_hpages; idx++) {
 241                 page = radix_tree_lookup(&mapping->page_tree, idx);
 242                 if (!page)
 243                         /* Pages which are already instantiated can't
 244                          * be unreserved (and in fact have already
 245                          * been removed from the reserved pool) */
 246                         change_in_reserve++;
 247         }
 248
 249         BUG_ON(reserved_huge_pages < change_in_reserve);
 250         reserved_huge_pages -= change_in_reserve;
 251         info->prereserved_hpages = atmost;
 252
 253  out:
 254         read_unlock_irq(&inode->i_mapping->tree_lock);
 255         spin_unlock(&hugetlb_lock);
 256 }
 257
 258 static int __init hugetlb_init(void)
 259 {
 260         unsigned long i;
 261
 262         if (HPAGE_SHIFT == 0)
 263                 return 0;
 264
 265         for (i = 0; i < MAX_NUMNODES; ++i)
 266                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 267
 268         for (i = 0; i < max_huge_pages; ++i) {
 269                 if (!alloc_fresh_huge_page())
 270                         break;
 271         }
 272         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 273         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 274         return 0;
 275 }
 276 module_init(hugetlb_init);
 277
 278 static int __init hugetlb_setup(char *s)
 279 {
 280         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 281                 max_huge_pages = 0;
 282         return 1;
 283 }
 284 __setup("hugepages=", hugetlb_setup);
 285
 286 #ifdef CONFIG_SYSCTL
 287 static void update_and_free_page(struct page *page)
 288 {
 289         int i;
 290         nr_huge_pages--;
 291         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 292         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 293                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 294                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 295                                 1 << PG_private | 1<< PG_writeback);
 296         }
 297         page[1].lru.next = NULL;
 298         set_page_refcounted(page);
 299         __free_pages(page, HUGETLB_PAGE_ORDER);
 300 }
 301
 302 #ifdef CONFIG_HIGHMEM
 303 static void try_to_free_low(unsigned long count)
 304 {
 305         int i, nid;
 306         for (i = 0; i < MAX_NUMNODES; ++i) {
 307                 struct page *page, *next;
 308                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 309                         if (PageHighMem(page))
 310                                 continue;
 311                         list_del(&page->lru);
 312                         update_and_free_page(page);
 313                         nid = page_zone(page)->zone_pgdat->node_id;
 314                         free_huge_pages--;
 315                         free_huge_pages_node[nid]--;
 316                         if (count >= nr_huge_pages)
 317                                 return;
 318                 }
 319         }
 320 }
 321 #else
 322 static inline void try_to_free_low(unsigned long count)
 323 {
 324 }
 325 #endif
 326
 327 static unsigned long set_max_huge_pages(unsigned long count)
 328 {
 329         while (count > nr_huge_pages) {
 330                 if (!alloc_fresh_huge_page())
 331                         return nr_huge_pages;
 332         }
 333         if (count >= nr_huge_pages)
 334                 return nr_huge_pages;
 335
 336         spin_lock(&hugetlb_lock);
 337         try_to_free_low(count);
 338         while (count < nr_huge_pages) {
 339                 struct page *page = dequeue_huge_page(NULL, 0);
 340                 if (!page)
 341                         break;
 342                 update_and_free_page(page);
 343         }
 344         spin_unlock(&hugetlb_lock);
 345         return nr_huge_pages;
 346 }
 347
 348 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 349                            struct file *file, void __user *buffer,
 350                            size_t *length, loff_t *ppos)
 351 {
 352         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 353         max_huge_pages = set_max_huge_pages(max_huge_pages);
 354         return 0;
 355 }
 356 #endif /* CONFIG_SYSCTL */
 357
 358 int hugetlb_report_meminfo(char *buf)
 359 {
 360         return sprintf(buf,
 361                         "HugePages_Total: %5lu\n"
 362                         "HugePages_Free:  %5lu\n"
 363                         "HugePages_Rsvd:  %5lu\n"
 364                         "Hugepagesize:    %5lu kB\n",
 365                         nr_huge_pages,
 366                         free_huge_pages,
 367                         reserved_huge_pages,
 368                         HPAGE_SIZE/1024);
 369 }
 370
 371 int hugetlb_report_node_meminfo(int nid, char *buf)
 372 {
 373         return sprintf(buf,
 374                 "Node %d HugePages_Total: %5u\n"
 375                 "Node %d HugePages_Free:  %5u\n",
 376                 nid, nr_huge_pages_node[nid],
 377                 nid, free_huge_pages_node[nid]);
 378 }
 379
 380 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 381 unsigned long hugetlb_total_pages(void)
 382 {
 383         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 384 }
 385
 386 /*
 387  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 388  * handle_mm_fault() to try to instantiate regular-sized pages in the
 389  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 390  * this far.
 391  */
 392 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 393                                 unsigned long address, int *unused)
 394 {
 395         BUG();
 396         return NULL;
 397 }
 398
 399 struct vm_operations_struct hugetlb_vm_ops = {
 400         .nopage = hugetlb_nopage,
 401 };
 402
 403 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 404                                 int writable)
 405 {
 406         pte_t entry;
 407
 408         if (writable) {
 409                 entry =
 410                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 411         } else {
 412                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 413         }
 414         entry = pte_mkyoung(entry);
 415         entry = pte_mkhuge(entry);
 416
 417         return entry;
 418 }
 419
 420 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 421                                    unsigned long address, pte_t *ptep)
 422 {
 423         pte_t entry;
 424
 425         entry = pte_mkwrite(pte_mkdirty(*ptep));
 426         ptep_set_access_flags(vma, address, ptep, entry, 1);
 427         update_mmu_cache(vma, address, entry);
 428         lazy_mmu_prot_update(entry);
 429 }
 430
 431
 432 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 433                             struct vm_area_struct *vma)
 434 {
 435         pte_t *src_pte, *dst_pte, entry;
 436         struct page *ptepage;
 437         unsigned long addr;
 438         int cow;
 439
 440         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 441
 442         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 443                 src_pte = huge_pte_offset(src, addr);
 444                 if (!src_pte)
 445                         continue;
 446                 dst_pte = huge_pte_alloc(dst, addr);
 447                 if (!dst_pte)
 448                         goto nomem;
 449                 spin_lock(&dst->page_table_lock);
 450                 spin_lock(&src->page_table_lock);
 451                 if (!pte_none(*src_pte)) {
 452                         if (cow)
 453                                 ptep_set_wrprotect(src, addr, src_pte);
 454                         entry = *src_pte;
 455                         ptepage = pte_page(entry);
 456                         get_page(ptepage);
 457                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 458                         set_huge_pte_at(dst, addr, dst_pte, entry);
 459                 }
 460                 spin_unlock(&src->page_table_lock);
 461                 spin_unlock(&dst->page_table_lock);
 462         }
 463         return 0;
 464
 465 nomem:
 466         return -ENOMEM;
 467 }
 468
 469 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 470                           unsigned long end)
 471 {
 472         struct mm_struct *mm = vma->vm_mm;
 473         unsigned long address;
 474         pte_t *ptep;
 475         pte_t pte;
 476         struct page *page;
 477
 478         WARN_ON(!is_vm_hugetlb_page(vma));
 479         BUG_ON(start & ~HPAGE_MASK);
 480         BUG_ON(end & ~HPAGE_MASK);
 481
 482         spin_lock(&mm->page_table_lock);
 483
 484         /* Update high watermark before we lower rss */
 485         update_hiwater_rss(mm);
 486
 487         for (address = start; address < end; address += HPAGE_SIZE) {
 488                 ptep = huge_pte_offset(mm, address);
 489                 if (!ptep)
 490                         continue;
 491
 492                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 493                 if (pte_none(pte))
 494                         continue;
 495
 496                 page = pte_page(pte);
 497                 put_page(page);
 498                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 499         }
 500
 501         spin_unlock(&mm->page_table_lock);
 502         flush_tlb_range(vma, start, end);
 503 }
 504
 505 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 506                         unsigned long address, pte_t *ptep, pte_t pte)
 507 {
 508         struct page *old_page, *new_page;
 509         int avoidcopy;
 510
 511         old_page = pte_page(pte);
 512
 513         /* If no-one else is actually using this page, avoid the copy
 514          * and just make the page writable */
 515         avoidcopy = (page_count(old_page) == 1);
 516         if (avoidcopy) {
 517                 set_huge_ptep_writable(vma, address, ptep);
 518                 return VM_FAULT_MINOR;
 519         }
 520
 521         page_cache_get(old_page);
 522         new_page = alloc_huge_page(vma, address);
 523
 524         if (!new_page) {
 525                 page_cache_release(old_page);
 526                 return VM_FAULT_OOM;
 527         }
 528
 529         spin_unlock(&mm->page_table_lock);
 530         copy_huge_page(new_page, old_page, address);
 531         spin_lock(&mm->page_table_lock);
 532
 533         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 534         if (likely(pte_same(*ptep, pte))) {
 535                 /* Break COW */
 536                 set_huge_pte_at(mm, address, ptep,
 537                                 make_huge_pte(vma, new_page, 1));
 538                 /* Make the old page be freed below */
 539                 new_page = old_page;
 540         }
 541         page_cache_release(new_page);
 542         page_cache_release(old_page);
 543         return VM_FAULT_MINOR;
 544 }
 545
 546 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 547                         unsigned long address, pte_t *ptep, int write_access)
 548 {
 549         int ret = VM_FAULT_SIGBUS;
 550         unsigned long idx;
 551         unsigned long size;
 552         struct page *page;
 553         struct address_space *mapping;
 554         pte_t new_pte;
 555
 556         mapping = vma->vm_file->f_mapping;
 557         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 558                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 559
 560         /*
 561          * Use page lock to guard against racing truncation
 562          * before we get page_table_lock.
 563          */
 564 retry:
 565         page = find_lock_page(mapping, idx);
 566         if (!page) {
 567                 if (hugetlb_get_quota(mapping))
 568                         goto out;
 569                 page = alloc_huge_page(vma, address);
 570                 if (!page) {
 571                         hugetlb_put_quota(mapping);
 572                         ret = VM_FAULT_OOM;
 573                         goto out;
 574                 }
 575                 clear_huge_page(page, address);
 576
 577                 if (vma->vm_flags & VM_SHARED) {
 578                         int err;
 579
 580                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 581                         if (err) {
 582                                 put_page(page);
 583                                 hugetlb_put_quota(mapping);
 584                                 if (err == -EEXIST)
 585                                         goto retry;
 586                                 goto out;
 587                         }
 588                 } else
 589                         lock_page(page);
 590         }
 591
 592         spin_lock(&mm->page_table_lock);
 593         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 594         if (idx >= size)
 595                 goto backout;
 596
 597         ret = VM_FAULT_MINOR;
 598         if (!pte_none(*ptep))
 599                 goto backout;
 600
 601         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 602         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 603                                 && (vma->vm_flags & VM_SHARED)));
 604         set_huge_pte_at(mm, address, ptep, new_pte);
 605
 606         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 607                 /* Optimization, do the COW without a second fault */
 608                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 609         }
 610
 611         spin_unlock(&mm->page_table_lock);
 612         unlock_page(page);
 613 out:
 614         return ret;
 615
 616 backout:
 617         spin_unlock(&mm->page_table_lock);
 618         hugetlb_put_quota(mapping);
 619         unlock_page(page);
 620         put_page(page);
 621         goto out;
 622 }
 623
 624 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 625                         unsigned long address, int write_access)
 626 {
 627         pte_t *ptep;
 628         pte_t entry;
 629         int ret;
 630         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 631
 632         ptep = huge_pte_alloc(mm, address);
 633         if (!ptep)
 634                 return VM_FAULT_OOM;
 635
 636         /*
 637          * Serialize hugepage allocation and instantiation, so that we don't
 638          * get spurious allocation failures if two CPUs race to instantiate
 639          * the same page in the page cache.
 640          */
 641         mutex_lock(&hugetlb_instantiation_mutex);
 642         entry = *ptep;
 643         if (pte_none(entry)) {
 644                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 645                 mutex_unlock(&hugetlb_instantiation_mutex);
 646                 return ret;
 647         }
 648
 649         ret = VM_FAULT_MINOR;
 650
 651         spin_lock(&mm->page_table_lock);
 652         /* Check for a racing update before calling hugetlb_cow */
 653         if (likely(pte_same(entry, *ptep)))
 654                 if (write_access && !pte_write(entry))
 655                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 656         spin_unlock(&mm->page_table_lock);
 657         mutex_unlock(&hugetlb_instantiation_mutex);
 658
 659         return ret;
 660 }
 661
 662 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 663                         struct page **pages, struct vm_area_struct **vmas,
 664                         unsigned long *position, int *length, int i)
 665 {
 666         unsigned long pfn_offset;
 667         unsigned long vaddr = *position;
 668         int remainder = *length;
 669
 670         spin_lock(&mm->page_table_lock);
 671         while (vaddr < vma->vm_end && remainder) {
 672                 pte_t *pte;
 673                 struct page *page;
 674
 675                 /*
 676                  * Some archs (sparc64, sh*) have multiple pte_ts to
 677                  * each hugepage.  We have to make * sure we get the
 678                  * first, for the page indexing below to work.
 679                  */
 680                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 681
 682                 if (!pte || pte_none(*pte)) {
 683                         int ret;
 684
 685                         spin_unlock(&mm->page_table_lock);
 686                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 687                         spin_lock(&mm->page_table_lock);
 688                         if (ret == VM_FAULT_MINOR)
 689                                 continue;
 690
 691                         remainder = 0;
 692                         if (!i)
 693                                 i = -EFAULT;
 694                         break;
 695                 }
 696
 697                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 698                 page = pte_page(*pte);
 699 same_page:
 700                 get_page(page);
 701                 if (pages)
 702                         pages[i] = page + pfn_offset;
 703
 704                 if (vmas)
 705                         vmas[i] = vma;
 706
 707                 vaddr += PAGE_SIZE;
 708                 ++pfn_offset;
 709                 --remainder;
 710                 ++i;
 711                 if (vaddr < vma->vm_end && remainder &&
 712                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 713                         /*
 714                          * We use pfn_offset to avoid touching the pageframes
 715                          * of this compound page.
 716                          */
 717                         goto same_page;
 718                 }
 719         }
 720         spin_unlock(&mm->page_table_lock);
 721         *length = remainder;
 722         *position = vaddr;
 723
 724         return i;
 725 }
 726
 727 void hugetlb_change_protection(struct vm_area_struct *vma,
 728                 unsigned long address, unsigned long end, pgprot_t newprot)
 729 {
 730         struct mm_struct *mm = vma->vm_mm;
 731         unsigned long start = address;
 732         pte_t *ptep;
 733         pte_t pte;
 734
 735         BUG_ON(address >= end);
 736         flush_cache_range(vma, address, end);
 737
 738         spin_lock(&mm->page_table_lock);
 739         for (; address < end; address += HPAGE_SIZE) {
 740                 ptep = huge_pte_offset(mm, address);
 741                 if (!ptep)
 742                         continue;
 743                 if (!pte_none(*ptep)) {
 744                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 745                         pte = pte_mkhuge(pte_modify(pte, newprot));
 746                         set_huge_pte_at(mm, address, ptep, pte);
 747                         lazy_mmu_prot_update(pte);
 748                 }
 749         }
 750         spin_unlock(&mm->page_table_lock);
 751
 752         flush_tlb_range(vma, start, end);
 753 }
 754