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 <linux/vs_memory.h>
  23 #include "internal.h"
  24
  25 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  26 static unsigned long nr_huge_pages, free_huge_pages, reserved_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 /*
  32  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  33  */
  34 static DEFINE_SPINLOCK(hugetlb_lock);
  35
  36 static void clear_huge_page(struct page *page, unsigned long addr)
  37 {
  38         int i;
  39
  40         might_sleep();
  41         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  42                 cond_resched();
  43                 clear_user_highpage(page + i, addr);
  44         }
  45 }
  46
  47 static void copy_huge_page(struct page *dst, struct page *src,
  48                            unsigned long addr)
  49 {
  50         int i;
  51
  52         might_sleep();
  53         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  54                 cond_resched();
  55                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE);
  56         }
  57 }
  58
  59 static void enqueue_huge_page(struct page *page)
  60 {
  61         int nid = page_to_nid(page);
  62         list_add(&page->lru, &hugepage_freelists[nid]);
  63         free_huge_pages++;
  64         free_huge_pages_node[nid]++;
  65 }
  66
  67 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  68                                 unsigned long address)
  69 {
  70         int nid = numa_node_id();
  71         struct page *page = NULL;
  72         struct zonelist *zonelist = huge_zonelist(vma, address);
  73         struct zone **z;
  74
  75         for (z = zonelist->zones; *z; z++) {
  76                 nid = (*z)->zone_pgdat->node_id;
  77                 if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
  78                     !list_empty(&hugepage_freelists[nid]))
  79                         break;
  80         }
  81
  82         if (*z) {
  83                 page = list_entry(hugepage_freelists[nid].next,
  84                                   struct page, lru);
  85                 list_del(&page->lru);
  86                 free_huge_pages--;
  87                 free_huge_pages_node[nid]--;
  88         }
  89         return page;
  90 }
  91
  92 static void free_huge_page(struct page *page)
  93 {
  94         BUG_ON(page_count(page));
  95
  96         INIT_LIST_HEAD(&page->lru);
  97
  98         spin_lock(&hugetlb_lock);
  99         enqueue_huge_page(page);
 100         spin_unlock(&hugetlb_lock);
 101 }
 102
 103 static int alloc_fresh_huge_page(void)
 104 {
 105         static int nid = 0;
 106         struct page *page;
 107         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
 108                                         HUGETLB_PAGE_ORDER);
 109         nid = next_node(nid, node_online_map);
 110         if (nid == MAX_NUMNODES)
 111                 nid = first_node(node_online_map);
 112         if (page) {
 113                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
 114                 spin_lock(&hugetlb_lock);
 115                 nr_huge_pages++;
 116                 nr_huge_pages_node[page_to_nid(page)]++;
 117                 spin_unlock(&hugetlb_lock);
 118                 put_page(page); /* free it into the hugepage allocator */
 119                 return 1;
 120         }
 121         return 0;
 122 }
 123
 124 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 125                                     unsigned long addr)
 126 {
 127         struct inode *inode = vma->vm_file->f_dentry->d_inode;
 128         struct page *page;
 129         int use_reserve = 0;
 130         unsigned long idx;
 131
 132         spin_lock(&hugetlb_lock);
 133
 134         if (vma->vm_flags & VM_MAYSHARE) {
 135
 136                 /* idx = radix tree index, i.e. offset into file in
 137                  * HPAGE_SIZE units */
 138                 idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
 139                         + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 140
 141                 /* The hugetlbfs specific inode info stores the number
 142                  * of "guaranteed available" (huge) pages.  That is,
 143                  * the first 'prereserved_hpages' pages of the inode
 144                  * are either already instantiated, or have been
 145                  * pre-reserved (by hugetlb_reserve_for_inode()). Here
 146                  * we're in the process of instantiating the page, so
 147                  * we use this to determine whether to draw from the
 148                  * pre-reserved pool or the truly free pool. */
 149                 if (idx < HUGETLBFS_I(inode)->prereserved_hpages)
 150                         use_reserve = 1;
 151         }
 152
 153         if (!use_reserve) {
 154                 if (free_huge_pages <= reserved_huge_pages)
 155                         goto fail;
 156         } else {
 157                 BUG_ON(reserved_huge_pages == 0);
 158                 reserved_huge_pages--;
 159         }
 160
 161         page = dequeue_huge_page(vma, addr);
 162         if (!page)
 163                 goto fail;
 164
 165         spin_unlock(&hugetlb_lock);
 166         set_page_refcounted(page);
 167         return page;
 168
 169  fail:
 170         WARN_ON(use_reserve); /* reserved allocations shouldn't fail */
 171         spin_unlock(&hugetlb_lock);
 172         return NULL;
 173 }
 174
 175 /* hugetlb_extend_reservation()
 176  *
 177  * Ensure that at least 'atleast' hugepages are, and will remain,
 178  * available to instantiate the first 'atleast' pages of the given
 179  * inode.  If the inode doesn't already have this many pages reserved
 180  * or instantiated, set aside some hugepages in the reserved pool to
 181  * satisfy later faults (or fail now if there aren't enough, rather
 182  * than getting the SIGBUS later).
 183  */
 184 int hugetlb_extend_reservation(struct hugetlbfs_inode_info *info,
 185                                unsigned long atleast)
 186 {
 187         struct inode *inode = &info->vfs_inode;
 188         unsigned long change_in_reserve = 0;
 189         int ret = 0;
 190
 191         spin_lock(&hugetlb_lock);
 192         read_lock_irq(&inode->i_mapping->tree_lock);
 193
 194         if (info->prereserved_hpages >= atleast)
 195                 goto out;
 196
 197         /* Because we always call this on shared mappings, none of the
 198          * pages beyond info->prereserved_hpages can have been
 199          * instantiated, so we need to reserve all of them now. */
 200         change_in_reserve = atleast - info->prereserved_hpages;
 201
 202         if ((reserved_huge_pages + change_in_reserve) > free_huge_pages) {
 203                 ret = -ENOMEM;
 204                 goto out;
 205         }
 206
 207         reserved_huge_pages += change_in_reserve;
 208         info->prereserved_hpages = atleast;
 209
 210  out:
 211         read_unlock_irq(&inode->i_mapping->tree_lock);
 212         spin_unlock(&hugetlb_lock);
 213
 214         return ret;
 215 }
 216
 217 /* hugetlb_truncate_reservation()
 218  *
 219  * This returns pages reserved for the given inode to the general free
 220  * hugepage pool.  If the inode has any pages prereserved, but not
 221  * instantiated, beyond offset (atmost << HPAGE_SIZE), then release
 222  * them.
 223  */
 224 void hugetlb_truncate_reservation(struct hugetlbfs_inode_info *info,
 225                                   unsigned long atmost)
 226 {
 227         struct inode *inode = &info->vfs_inode;
 228         struct address_space *mapping = inode->i_mapping;
 229         unsigned long idx;
 230         unsigned long change_in_reserve = 0;
 231         struct page *page;
 232
 233         spin_lock(&hugetlb_lock);
 234         read_lock_irq(&inode->i_mapping->tree_lock);
 235
 236         if (info->prereserved_hpages <= atmost)
 237                 goto out;
 238
 239         /* Count pages which were reserved, but not instantiated, and
 240          * which we can now release. */
 241         for (idx = atmost; idx < info->prereserved_hpages; idx++) {
 242                 page = radix_tree_lookup(&mapping->page_tree, idx);
 243                 if (!page)
 244                         /* Pages which are already instantiated can't
 245                          * be unreserved (and in fact have already
 246                          * been removed from the reserved pool) */
 247                         change_in_reserve++;
 248         }
 249
 250         BUG_ON(reserved_huge_pages < change_in_reserve);
 251         reserved_huge_pages -= change_in_reserve;
 252         info->prereserved_hpages = atmost;
 253
 254  out:
 255         read_unlock_irq(&inode->i_mapping->tree_lock);
 256         spin_unlock(&hugetlb_lock);
 257 }
 258
 259 static int __init hugetlb_init(void)
 260 {
 261         unsigned long i;
 262
 263         if (HPAGE_SHIFT == 0)
 264                 return 0;
 265
 266         for (i = 0; i < MAX_NUMNODES; ++i)
 267                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 268
 269         for (i = 0; i < max_huge_pages; ++i) {
 270                 if (!alloc_fresh_huge_page())
 271                         break;
 272         }
 273         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 274         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 275         return 0;
 276 }
 277 module_init(hugetlb_init);
 278
 279 static int __init hugetlb_setup(char *s)
 280 {
 281         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 282                 max_huge_pages = 0;
 283         return 1;
 284 }
 285 __setup("hugepages=", hugetlb_setup);
 286
 287 #ifdef CONFIG_SYSCTL
 288 static void update_and_free_page(struct page *page)
 289 {
 290         int i;
 291         nr_huge_pages--;
 292         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 293         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 294                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 295                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 296                                 1 << PG_private | 1<< PG_writeback);
 297         }
 298         page[1].lru.next = NULL;
 299         set_page_refcounted(page);
 300         __free_pages(page, HUGETLB_PAGE_ORDER);
 301 }
 302
 303 #ifdef CONFIG_HIGHMEM
 304 static void try_to_free_low(unsigned long count)
 305 {
 306         int i, nid;
 307         for (i = 0; i < MAX_NUMNODES; ++i) {
 308                 struct page *page, *next;
 309                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 310                         if (PageHighMem(page))
 311                                 continue;
 312                         list_del(&page->lru);
 313                         update_and_free_page(page);
 314                         nid = page_zone(page)->zone_pgdat->node_id;
 315                         free_huge_pages--;
 316                         free_huge_pages_node[nid]--;
 317                         if (count >= nr_huge_pages)
 318                                 return;
 319                 }
 320         }
 321 }
 322 #else
 323 static inline void try_to_free_low(unsigned long count)
 324 {
 325 }
 326 #endif
 327
 328 static unsigned long set_max_huge_pages(unsigned long count)
 329 {
 330         while (count > nr_huge_pages) {
 331                 if (!alloc_fresh_huge_page())
 332                         return nr_huge_pages;
 333         }
 334         if (count >= nr_huge_pages)
 335                 return nr_huge_pages;
 336
 337         spin_lock(&hugetlb_lock);
 338         count = max(count, reserved_huge_pages);
 339         try_to_free_low(count);
 340         while (count < nr_huge_pages) {
 341                 struct page *page = dequeue_huge_page(NULL, 0);
 342                 if (!page)
 343                         break;
 344                 update_and_free_page(page);
 345         }
 346         spin_unlock(&hugetlb_lock);
 347         return nr_huge_pages;
 348 }
 349
 350 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 351                            struct file *file, void __user *buffer,
 352                            size_t *length, loff_t *ppos)
 353 {
 354         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 355         max_huge_pages = set_max_huge_pages(max_huge_pages);
 356         return 0;
 357 }
 358 #endif /* CONFIG_SYSCTL */
 359
 360 int hugetlb_report_meminfo(char *buf)
 361 {
 362         return sprintf(buf,
 363                         "HugePages_Total: %5lu\n"
 364                         "HugePages_Free:  %5lu\n"
 365                         "HugePages_Rsvd:  %5lu\n"
 366                         "Hugepagesize:    %5lu kB\n",
 367                         nr_huge_pages,
 368                         free_huge_pages,
 369                         reserved_huge_pages,
 370                         HPAGE_SIZE/1024);
 371 }
 372
 373 int hugetlb_report_node_meminfo(int nid, char *buf)
 374 {
 375         return sprintf(buf,
 376                 "Node %d HugePages_Total: %5u\n"
 377                 "Node %d HugePages_Free:  %5u\n",
 378                 nid, nr_huge_pages_node[nid],
 379                 nid, free_huge_pages_node[nid]);
 380 }
 381
 382 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 383 unsigned long hugetlb_total_pages(void)
 384 {
 385         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 386 }
 387
 388 /*
 389  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 390  * handle_mm_fault() to try to instantiate regular-sized pages in the
 391  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 392  * this far.
 393  */
 394 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 395                                 unsigned long address, int *unused)
 396 {
 397         BUG();
 398         return NULL;
 399 }
 400
 401 struct vm_operations_struct hugetlb_vm_ops = {
 402         .nopage = hugetlb_nopage,
 403 };
 404
 405 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 406                                 int writable)
 407 {
 408         pte_t entry;
 409
 410         if (writable) {
 411                 entry =
 412                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 413         } else {
 414                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 415         }
 416         entry = pte_mkyoung(entry);
 417         entry = pte_mkhuge(entry);
 418
 419         return entry;
 420 }
 421
 422 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 423                                    unsigned long address, pte_t *ptep)
 424 {
 425         pte_t entry;
 426
 427         entry = pte_mkwrite(pte_mkdirty(*ptep));
 428         ptep_set_access_flags(vma, address, ptep, entry, 1);
 429         update_mmu_cache(vma, address, entry);
 430         lazy_mmu_prot_update(entry);
 431 }
 432
 433
 434 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 435                             struct vm_area_struct *vma)
 436 {
 437         pte_t *src_pte, *dst_pte, entry;
 438         struct page *ptepage;
 439         unsigned long addr;
 440         int cow;
 441
 442         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 443
 444         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 445                 src_pte = huge_pte_offset(src, addr);
 446                 if (!src_pte)
 447                         continue;
 448                 dst_pte = huge_pte_alloc(dst, addr);
 449                 if (!dst_pte)
 450                         goto nomem;
 451                 spin_lock(&dst->page_table_lock);
 452                 spin_lock(&src->page_table_lock);
 453                 if (!pte_none(*src_pte)) {
 454                         if (cow)
 455                                 ptep_set_wrprotect(src, addr, src_pte);
 456                         entry = *src_pte;
 457                         ptepage = pte_page(entry);
 458                         get_page(ptepage);
 459                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 460                         set_huge_pte_at(dst, addr, dst_pte, entry);
 461                 }
 462                 spin_unlock(&src->page_table_lock);
 463                 spin_unlock(&dst->page_table_lock);
 464         }
 465         return 0;
 466
 467 nomem:
 468         return -ENOMEM;
 469 }
 470
 471 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 472                           unsigned long end)
 473 {
 474         struct mm_struct *mm = vma->vm_mm;
 475         unsigned long address;
 476         pte_t *ptep;
 477         pte_t pte;
 478         struct page *page;
 479
 480         WARN_ON(!is_vm_hugetlb_page(vma));
 481         BUG_ON(start & ~HPAGE_MASK);
 482         BUG_ON(end & ~HPAGE_MASK);
 483
 484         spin_lock(&mm->page_table_lock);
 485
 486         /* Update high watermark before we lower rss */
 487         update_hiwater_rss(mm);
 488
 489         for (address = start; address < end; address += HPAGE_SIZE) {
 490                 ptep = huge_pte_offset(mm, address);
 491                 if (!ptep)
 492                         continue;
 493
 494                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 495                 if (pte_none(pte))
 496                         continue;
 497
 498                 page = pte_page(pte);
 499                 put_page(page);
 500                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 501         }
 502
 503         spin_unlock(&mm->page_table_lock);
 504         flush_tlb_range(vma, start, end);
 505 }
 506
 507 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 508                         unsigned long address, pte_t *ptep, pte_t pte)
 509 {
 510         struct page *old_page, *new_page;
 511         int avoidcopy;
 512
 513         old_page = pte_page(pte);
 514
 515         /* If no-one else is actually using this page, avoid the copy
 516          * and just make the page writable */
 517         avoidcopy = (page_count(old_page) == 1);
 518         if (avoidcopy) {
 519                 set_huge_ptep_writable(vma, address, ptep);
 520                 return VM_FAULT_MINOR;
 521         }
 522
 523         page_cache_get(old_page);
 524         new_page = alloc_huge_page(vma, address);
 525
 526         if (!new_page) {
 527                 page_cache_release(old_page);
 528                 return VM_FAULT_OOM;
 529         }
 530
 531         spin_unlock(&mm->page_table_lock);
 532         copy_huge_page(new_page, old_page, address);
 533         spin_lock(&mm->page_table_lock);
 534
 535         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 536         if (likely(pte_same(*ptep, pte))) {
 537                 /* Break COW */
 538                 set_huge_pte_at(mm, address, ptep,
 539                                 make_huge_pte(vma, new_page, 1));
 540                 /* Make the old page be freed below */
 541                 new_page = old_page;
 542         }
 543         page_cache_release(new_page);
 544         page_cache_release(old_page);
 545         return VM_FAULT_MINOR;
 546 }
 547
 548 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 549                         unsigned long address, pte_t *ptep, int write_access)
 550 {
 551         int ret = VM_FAULT_SIGBUS;
 552         unsigned long idx;
 553         unsigned long size;
 554         struct page *page;
 555         struct address_space *mapping;
 556         pte_t new_pte;
 557
 558         mapping = vma->vm_file->f_mapping;
 559         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 560                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 561
 562         /*
 563          * Use page lock to guard against racing truncation
 564          * before we get page_table_lock.
 565          */
 566 retry:
 567         page = find_lock_page(mapping, idx);
 568         if (!page) {
 569                 if (hugetlb_get_quota(mapping))
 570                         goto out;
 571                 page = alloc_huge_page(vma, address);
 572                 if (!page) {
 573                         hugetlb_put_quota(mapping);
 574                         ret = VM_FAULT_OOM;
 575                         goto out;
 576                 }
 577                 clear_huge_page(page, address);
 578
 579                 if (vma->vm_flags & VM_SHARED) {
 580                         int err;
 581
 582                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 583                         if (err) {
 584                                 put_page(page);
 585                                 hugetlb_put_quota(mapping);
 586                                 if (err == -EEXIST)
 587                                         goto retry;
 588                                 goto out;
 589                         }
 590                 } else
 591                         lock_page(page);
 592         }
 593
 594         spin_lock(&mm->page_table_lock);
 595         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 596         if (idx >= size)
 597                 goto backout;
 598
 599         ret = VM_FAULT_MINOR;
 600         if (!pte_none(*ptep))
 601                 goto backout;
 602
 603         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 604         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 605                                 && (vma->vm_flags & VM_SHARED)));
 606         set_huge_pte_at(mm, address, ptep, new_pte);
 607
 608         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 609                 /* Optimization, do the COW without a second fault */
 610                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 611         }
 612
 613         spin_unlock(&mm->page_table_lock);
 614         unlock_page(page);
 615 out:
 616         return ret;
 617
 618 backout:
 619         spin_unlock(&mm->page_table_lock);
 620         hugetlb_put_quota(mapping);
 621         unlock_page(page);
 622         put_page(page);
 623         goto out;
 624 }
 625
 626 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 627                         unsigned long address, int write_access)
 628 {
 629         pte_t *ptep;
 630         pte_t entry;
 631         int ret;
 632         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 633
 634         ptep = huge_pte_alloc(mm, address);
 635         if (!ptep)
 636                 return VM_FAULT_OOM;
 637
 638         /*
 639          * Serialize hugepage allocation and instantiation, so that we don't
 640          * get spurious allocation failures if two CPUs race to instantiate
 641          * the same page in the page cache.
 642          */
 643         mutex_lock(&hugetlb_instantiation_mutex);
 644         entry = *ptep;
 645         if (pte_none(entry)) {
 646                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 647                 mutex_unlock(&hugetlb_instantiation_mutex);
 648                 return ret;
 649         }
 650
 651         ret = VM_FAULT_MINOR;
 652
 653         spin_lock(&mm->page_table_lock);
 654         /* Check for a racing update before calling hugetlb_cow */
 655         if (likely(pte_same(entry, *ptep)))
 656                 if (write_access && !pte_write(entry))
 657                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 658         spin_unlock(&mm->page_table_lock);
 659         mutex_unlock(&hugetlb_instantiation_mutex);
 660
 661         return ret;
 662 }
 663
 664 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 665                         struct page **pages, struct vm_area_struct **vmas,
 666                         unsigned long *position, int *length, int i)
 667 {
 668         unsigned long pfn_offset;
 669         unsigned long vaddr = *position;
 670         int remainder = *length;
 671
 672         spin_lock(&mm->page_table_lock);
 673         while (vaddr < vma->vm_end && remainder) {
 674                 pte_t *pte;
 675                 struct page *page;
 676
 677                 /*
 678                  * Some archs (sparc64, sh*) have multiple pte_ts to
 679                  * each hugepage.  We have to make * sure we get the
 680                  * first, for the page indexing below to work.
 681                  */
 682                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 683
 684                 if (!pte || pte_none(*pte)) {
 685                         int ret;
 686
 687                         spin_unlock(&mm->page_table_lock);
 688                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 689                         spin_lock(&mm->page_table_lock);
 690                         if (ret == VM_FAULT_MINOR)
 691                                 continue;
 692
 693                         remainder = 0;
 694                         if (!i)
 695                                 i = -EFAULT;
 696                         break;
 697                 }
 698
 699                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 700                 page = pte_page(*pte);
 701 same_page:
 702                 if (pages) {
 703                         get_page(page);
 704                         pages[i] = page + pfn_offset;
 705                 }
 706
 707                 if (vmas)
 708                         vmas[i] = vma;
 709
 710                 vaddr += PAGE_SIZE;
 711                 ++pfn_offset;
 712                 --remainder;
 713                 ++i;
 714                 if (vaddr < vma->vm_end && remainder &&
 715                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 716                         /*
 717                          * We use pfn_offset to avoid touching the pageframes
 718                          * of this compound page.
 719                          */
 720                         goto same_page;
 721                 }
 722         }
 723         spin_unlock(&mm->page_table_lock);
 724         *length = remainder;
 725         *position = vaddr;
 726
 727         return i;
 728 }
 729
 730 void hugetlb_change_protection(struct vm_area_struct *vma,
 731                 unsigned long address, unsigned long end, pgprot_t newprot)
 732 {
 733         struct mm_struct *mm = vma->vm_mm;
 734         unsigned long start = address;
 735         pte_t *ptep;
 736         pte_t pte;
 737
 738         BUG_ON(address >= end);
 739         flush_cache_range(vma, address, end);
 740
 741         spin_lock(&mm->page_table_lock);
 742         for (; address < end; address += HPAGE_SIZE) {
 743                 ptep = huge_pte_offset(mm, address);
 744                 if (!ptep)
 745                         continue;
 746                 if (!pte_none(*ptep)) {
 747                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 748                         pte = pte_mkhuge(pte_modify(pte, newprot));
 749                         set_huge_pte_at(mm, address, ptep, pte);
 750                         lazy_mmu_prot_update(pte);
 751                 }
 752         }
 753         spin_unlock(&mm->page_table_lock);
 754
 755         flush_tlb_range(vma, start, end);
 756 }
 757