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 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 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
  31 unsigned long hugepages_treat_as_movable;
  32
  33 /*
  34  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  35  */
  36 static DEFINE_SPINLOCK(hugetlb_lock);
  37
  38 static void clear_huge_page(struct page *page, unsigned long addr)
  39 {
  40         int i;
  41
  42         might_sleep();
  43         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  44                 cond_resched();
  45                 clear_user_highpage(page + i, addr);
  46         }
  47 }
  48
  49 static void copy_huge_page(struct page *dst, struct page *src,
  50                            unsigned long addr, struct vm_area_struct *vma)
  51 {
  52         int i;
  53
  54         might_sleep();
  55         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  56                 cond_resched();
  57                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
  58         }
  59 }
  60
  61 static void enqueue_huge_page(struct page *page)
  62 {
  63         int nid = page_to_nid(page);
  64         list_add(&page->lru, &hugepage_freelists[nid]);
  65         free_huge_pages++;
  66         free_huge_pages_node[nid]++;
  67 }
  68
  69 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  70                                 unsigned long address)
  71 {
  72         int nid;
  73         struct page *page = NULL;
  74         struct zonelist *zonelist = huge_zonelist(vma, address,
  75                                                 htlb_alloc_mask);
  76         struct zone **z;
  77
  78         for (z = zonelist->zones; *z; z++) {
  79                 nid = zone_to_nid(*z);
  80                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
  81                     !list_empty(&hugepage_freelists[nid])) {
  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                         break;
  88                 }
  89         }
  90         return page;
  91 }
  92
  93 static void free_huge_page(struct page *page)
  94 {
  95         BUG_ON(page_count(page));
  96
  97         INIT_LIST_HEAD(&page->lru);
  98
  99         spin_lock(&hugetlb_lock);
 100         enqueue_huge_page(page);
 101         spin_unlock(&hugetlb_lock);
 102 }
 103
 104 static int alloc_fresh_huge_page(void)
 105 {
 106         static int prev_nid;
 107         struct page *page;
 108         int nid;
 109
 110         /*
 111          * Copy static prev_nid to local nid, work on that, then copy it
 112          * back to prev_nid afterwards: otherwise there's a window in which
 113          * a racer might pass invalid nid MAX_NUMNODES to alloc_pages_node.
 114          * But we don't need to use a spin_lock here: it really doesn't
 115          * matter if occasionally a racer chooses the same nid as we do.
 116          */
 117         nid = next_node(prev_nid, node_online_map);
 118         if (nid == MAX_NUMNODES)
 119                 nid = first_node(node_online_map);
 120         prev_nid = nid;
 121
 122         page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 123                                         HUGETLB_PAGE_ORDER);
 124         if (page) {
 125                 set_compound_page_dtor(page, free_huge_page);
 126                 spin_lock(&hugetlb_lock);
 127                 nr_huge_pages++;
 128                 nr_huge_pages_node[page_to_nid(page)]++;
 129                 spin_unlock(&hugetlb_lock);
 130                 put_page(page); /* free it into the hugepage allocator */
 131                 return 1;
 132         }
 133         return 0;
 134 }
 135
 136 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 137                                     unsigned long addr)
 138 {
 139         struct page *page;
 140
 141         spin_lock(&hugetlb_lock);
 142         if (vma->vm_flags & VM_MAYSHARE)
 143                 resv_huge_pages--;
 144         else if (free_huge_pages <= resv_huge_pages)
 145                 goto fail;
 146
 147         page = dequeue_huge_page(vma, addr);
 148         if (!page)
 149                 goto fail;
 150
 151         spin_unlock(&hugetlb_lock);
 152         set_page_refcounted(page);
 153         return page;
 154
 155 fail:
 156         if (vma->vm_flags & VM_MAYSHARE)
 157                 resv_huge_pages++;
 158         spin_unlock(&hugetlb_lock);
 159         return NULL;
 160 }
 161
 162 static int __init hugetlb_init(void)
 163 {
 164         unsigned long i;
 165
 166         if (HPAGE_SHIFT == 0)
 167                 return 0;
 168
 169         for (i = 0; i < MAX_NUMNODES; ++i)
 170                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 171
 172         for (i = 0; i < max_huge_pages; ++i) {
 173                 if (!alloc_fresh_huge_page())
 174                         break;
 175         }
 176         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 177         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 178         return 0;
 179 }
 180 module_init(hugetlb_init);
 181
 182 static int __init hugetlb_setup(char *s)
 183 {
 184         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 185                 max_huge_pages = 0;
 186         return 1;
 187 }
 188 __setup("hugepages=", hugetlb_setup);
 189
 190 static unsigned int cpuset_mems_nr(unsigned int *array)
 191 {
 192         int node;
 193         unsigned int nr = 0;
 194
 195         for_each_node_mask(node, cpuset_current_mems_allowed)
 196                 nr += array[node];
 197
 198         return nr;
 199 }
 200
 201 #ifdef CONFIG_SYSCTL
 202 static void update_and_free_page(struct page *page)
 203 {
 204         int i;
 205         nr_huge_pages--;
 206         nr_huge_pages_node[page_to_nid(page)]--;
 207         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 208                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 209                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 210                                 1 << PG_private | 1<< PG_writeback);
 211         }
 212         set_compound_page_dtor(page, NULL);
 213         set_page_refcounted(page);
 214         __free_pages(page, HUGETLB_PAGE_ORDER);
 215 }
 216
 217 #ifdef CONFIG_HIGHMEM
 218 static void try_to_free_low(unsigned long count)
 219 {
 220         int i;
 221
 222         for (i = 0; i < MAX_NUMNODES; ++i) {
 223                 struct page *page, *next;
 224                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 225                         if (PageHighMem(page))
 226                                 continue;
 227                         list_del(&page->lru);
 228                         update_and_free_page(page);
 229                         free_huge_pages--;
 230                         free_huge_pages_node[page_to_nid(page)]--;
 231                         if (count >= nr_huge_pages)
 232                                 return;
 233                 }
 234         }
 235 }
 236 #else
 237 static inline void try_to_free_low(unsigned long count)
 238 {
 239 }
 240 #endif
 241
 242 static unsigned long set_max_huge_pages(unsigned long count)
 243 {
 244         while (count > nr_huge_pages) {
 245                 if (!alloc_fresh_huge_page())
 246                         return nr_huge_pages;
 247         }
 248         if (count >= nr_huge_pages)
 249                 return nr_huge_pages;
 250
 251         spin_lock(&hugetlb_lock);
 252         count = max(count, resv_huge_pages);
 253         try_to_free_low(count);
 254         while (count < nr_huge_pages) {
 255                 struct page *page = dequeue_huge_page(NULL, 0);
 256                 if (!page)
 257                         break;
 258                 update_and_free_page(page);
 259         }
 260         spin_unlock(&hugetlb_lock);
 261         return nr_huge_pages;
 262 }
 263
 264 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 265                            struct file *file, void __user *buffer,
 266                            size_t *length, loff_t *ppos)
 267 {
 268         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 269         max_huge_pages = set_max_huge_pages(max_huge_pages);
 270         return 0;
 271 }
 272
 273 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 274                         struct file *file, void __user *buffer,
 275                         size_t *length, loff_t *ppos)
 276 {
 277         proc_dointvec(table, write, file, buffer, length, ppos);
 278         if (hugepages_treat_as_movable)
 279                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
 280         else
 281                 htlb_alloc_mask = GFP_HIGHUSER;
 282         return 0;
 283 }
 284
 285 #endif /* CONFIG_SYSCTL */
 286
 287 int hugetlb_report_meminfo(char *buf)
 288 {
 289         return sprintf(buf,
 290                         "HugePages_Total: %5lu\n"
 291                         "HugePages_Free:  %5lu\n"
 292                         "HugePages_Rsvd:  %5lu\n"
 293                         "Hugepagesize:    %5lu kB\n",
 294                         nr_huge_pages,
 295                         free_huge_pages,
 296                         resv_huge_pages,
 297                         HPAGE_SIZE/1024);
 298 }
 299
 300 int hugetlb_report_node_meminfo(int nid, char *buf)
 301 {
 302         return sprintf(buf,
 303                 "Node %d HugePages_Total: %5u\n"
 304                 "Node %d HugePages_Free:  %5u\n",
 305                 nid, nr_huge_pages_node[nid],
 306                 nid, free_huge_pages_node[nid]);
 307 }
 308
 309 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 310 unsigned long hugetlb_total_pages(void)
 311 {
 312         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 313 }
 314
 315 /*
 316  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 317  * handle_mm_fault() to try to instantiate regular-sized pages in the
 318  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 319  * this far.
 320  */
 321 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 322 {
 323         BUG();
 324         return 0;
 325 }
 326
 327 struct vm_operations_struct hugetlb_vm_ops = {
 328         .fault = hugetlb_vm_op_fault,
 329 };
 330
 331 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 332                                 int writable)
 333 {
 334         pte_t entry;
 335
 336         if (writable) {
 337                 entry =
 338                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 339         } else {
 340                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 341         }
 342         entry = pte_mkyoung(entry);
 343         entry = pte_mkhuge(entry);
 344
 345         return entry;
 346 }
 347
 348 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 349                                    unsigned long address, pte_t *ptep)
 350 {
 351         pte_t entry;
 352
 353         entry = pte_mkwrite(pte_mkdirty(*ptep));
 354         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
 355                 update_mmu_cache(vma, address, entry);
 356                 lazy_mmu_prot_update(entry);
 357         }
 358 }
 359
 360
 361 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 362                             struct vm_area_struct *vma)
 363 {
 364         pte_t *src_pte, *dst_pte, entry;
 365         struct page *ptepage;
 366         unsigned long addr;
 367         int cow;
 368
 369         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 370
 371         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 372                 src_pte = huge_pte_offset(src, addr);
 373                 if (!src_pte)
 374                         continue;
 375                 dst_pte = huge_pte_alloc(dst, addr);
 376                 if (!dst_pte)
 377                         goto nomem;
 378                 spin_lock(&dst->page_table_lock);
 379                 spin_lock(&src->page_table_lock);
 380                 if (!pte_none(*src_pte)) {
 381                         if (cow)
 382                                 ptep_set_wrprotect(src, addr, src_pte);
 383                         entry = *src_pte;
 384                         ptepage = pte_page(entry);
 385                         get_page(ptepage);
 386                         set_huge_pte_at(dst, addr, dst_pte, entry);
 387                 }
 388                 spin_unlock(&src->page_table_lock);
 389                 spin_unlock(&dst->page_table_lock);
 390         }
 391         return 0;
 392
 393 nomem:
 394         return -ENOMEM;
 395 }
 396
 397 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 398                             unsigned long end)
 399 {
 400         struct mm_struct *mm = vma->vm_mm;
 401         unsigned long address;
 402         pte_t *ptep;
 403         pte_t pte;
 404         struct page *page;
 405         struct page *tmp;
 406         /*
 407          * A page gathering list, protected by per file i_mmap_lock. The
 408          * lock is used to avoid list corruption from multiple unmapping
 409          * of the same page since we are using page->lru.
 410          */
 411         LIST_HEAD(page_list);
 412
 413         WARN_ON(!is_vm_hugetlb_page(vma));
 414         BUG_ON(start & ~HPAGE_MASK);
 415         BUG_ON(end & ~HPAGE_MASK);
 416
 417         spin_lock(&mm->page_table_lock);
 418         for (address = start; address < end; address += HPAGE_SIZE) {
 419                 ptep = huge_pte_offset(mm, address);
 420                 if (!ptep)
 421                         continue;
 422
 423                 if (huge_pmd_unshare(mm, &address, ptep))
 424                         continue;
 425
 426                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 427                 if (pte_none(pte))
 428                         continue;
 429
 430                 page = pte_page(pte);
 431                 if (pte_dirty(pte))
 432                         set_page_dirty(page);
 433                 list_add(&page->lru, &page_list);
 434         }
 435         spin_unlock(&mm->page_table_lock);
 436         flush_tlb_range(vma, start, end);
 437         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 438                 list_del(&page->lru);
 439                 put_page(page);
 440         }
 441 }
 442
 443 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 444                           unsigned long end)
 445 {
 446         /*
 447          * It is undesirable to test vma->vm_file as it should be non-null
 448          * for valid hugetlb area. However, vm_file will be NULL in the error
 449          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 450          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 451          * to clean up. Since no pte has actually been setup, it is safe to
 452          * do nothing in this case.
 453          */
 454         if (vma->vm_file) {
 455                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 456                 __unmap_hugepage_range(vma, start, end);
 457                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 458         }
 459 }
 460
 461 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 462                         unsigned long address, pte_t *ptep, pte_t pte)
 463 {
 464         struct page *old_page, *new_page;
 465         int avoidcopy;
 466
 467         old_page = pte_page(pte);
 468
 469         /* If no-one else is actually using this page, avoid the copy
 470          * and just make the page writable */
 471         avoidcopy = (page_count(old_page) == 1);
 472         if (avoidcopy) {
 473                 set_huge_ptep_writable(vma, address, ptep);
 474                 return 0;
 475         }
 476
 477         page_cache_get(old_page);
 478         new_page = alloc_huge_page(vma, address);
 479
 480         if (!new_page) {
 481                 page_cache_release(old_page);
 482                 return VM_FAULT_OOM;
 483         }
 484
 485         spin_unlock(&mm->page_table_lock);
 486         copy_huge_page(new_page, old_page, address, vma);
 487         spin_lock(&mm->page_table_lock);
 488
 489         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 490         if (likely(pte_same(*ptep, pte))) {
 491                 /* Break COW */
 492                 set_huge_pte_at(mm, address, ptep,
 493                                 make_huge_pte(vma, new_page, 1));
 494                 /* Make the old page be freed below */
 495                 new_page = old_page;
 496         }
 497         page_cache_release(new_page);
 498         page_cache_release(old_page);
 499         return 0;
 500 }
 501
 502 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 503                         unsigned long address, pte_t *ptep, int write_access)
 504 {
 505         int ret = VM_FAULT_SIGBUS;
 506         unsigned long idx;
 507         unsigned long size;
 508         struct page *page;
 509         struct address_space *mapping;
 510         pte_t new_pte;
 511
 512         mapping = vma->vm_file->f_mapping;
 513         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 514                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 515
 516         /*
 517          * Use page lock to guard against racing truncation
 518          * before we get page_table_lock.
 519          */
 520 retry:
 521         page = find_lock_page(mapping, idx);
 522         if (!page) {
 523                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 524                 if (idx >= size)
 525                         goto out;
 526                 if (hugetlb_get_quota(mapping))
 527                         goto out;
 528                 page = alloc_huge_page(vma, address);
 529                 if (!page) {
 530                         hugetlb_put_quota(mapping);
 531                         ret = VM_FAULT_OOM;
 532                         goto out;
 533                 }
 534                 clear_huge_page(page, address);
 535
 536                 if (vma->vm_flags & VM_SHARED) {
 537                         int err;
 538
 539                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 540                         if (err) {
 541                                 put_page(page);
 542                                 hugetlb_put_quota(mapping);
 543                                 if (err == -EEXIST)
 544                                         goto retry;
 545                                 goto out;
 546                         }
 547                 } else
 548                         lock_page(page);
 549         }
 550
 551         spin_lock(&mm->page_table_lock);
 552         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 553         if (idx >= size)
 554                 goto backout;
 555
 556         ret = 0;
 557         if (!pte_none(*ptep))
 558                 goto backout;
 559
 560         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 561                                 && (vma->vm_flags & VM_SHARED)));
 562         set_huge_pte_at(mm, address, ptep, new_pte);
 563
 564         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 565                 /* Optimization, do the COW without a second fault */
 566                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 567         }
 568
 569         spin_unlock(&mm->page_table_lock);
 570         unlock_page(page);
 571 out:
 572         return ret;
 573
 574 backout:
 575         spin_unlock(&mm->page_table_lock);
 576         hugetlb_put_quota(mapping);
 577         unlock_page(page);
 578         put_page(page);
 579         goto out;
 580 }
 581
 582 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 583                         unsigned long address, int write_access)
 584 {
 585         pte_t *ptep;
 586         pte_t entry;
 587         int ret;
 588         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 589
 590         ptep = huge_pte_alloc(mm, address);
 591         if (!ptep)
 592                 return VM_FAULT_OOM;
 593
 594         /*
 595          * Serialize hugepage allocation and instantiation, so that we don't
 596          * get spurious allocation failures if two CPUs race to instantiate
 597          * the same page in the page cache.
 598          */
 599         mutex_lock(&hugetlb_instantiation_mutex);
 600         entry = *ptep;
 601         if (pte_none(entry)) {
 602                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 603                 mutex_unlock(&hugetlb_instantiation_mutex);
 604                 return ret;
 605         }
 606
 607         ret = 0;
 608
 609         spin_lock(&mm->page_table_lock);
 610         /* Check for a racing update before calling hugetlb_cow */
 611         if (likely(pte_same(entry, *ptep)))
 612                 if (write_access && !pte_write(entry))
 613                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 614         spin_unlock(&mm->page_table_lock);
 615         mutex_unlock(&hugetlb_instantiation_mutex);
 616
 617         return ret;
 618 }
 619
 620 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 621                         struct page **pages, struct vm_area_struct **vmas,
 622                         unsigned long *position, int *length, int i)
 623 {
 624         unsigned long pfn_offset;
 625         unsigned long vaddr = *position;
 626         int remainder = *length;
 627
 628         spin_lock(&mm->page_table_lock);
 629         while (vaddr < vma->vm_end && remainder) {
 630                 pte_t *pte;
 631                 struct page *page;
 632
 633                 /*
 634                  * Some archs (sparc64, sh*) have multiple pte_ts to
 635                  * each hugepage.  We have to make * sure we get the
 636                  * first, for the page indexing below to work.
 637                  */
 638                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 639
 640                 if (!pte || pte_none(*pte)) {
 641                         int ret;
 642
 643                         spin_unlock(&mm->page_table_lock);
 644                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 645                         spin_lock(&mm->page_table_lock);
 646                         if (!(ret & VM_FAULT_ERROR))
 647                                 continue;
 648
 649                         remainder = 0;
 650                         if (!i)
 651                                 i = -EFAULT;
 652                         break;
 653                 }
 654
 655                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 656                 page = pte_page(*pte);
 657 same_page:
 658                 if (pages) {
 659                         get_page(page);
 660                         pages[i] = page + pfn_offset;
 661                 }
 662
 663                 if (vmas)
 664                         vmas[i] = vma;
 665
 666                 vaddr += PAGE_SIZE;
 667                 ++pfn_offset;
 668                 --remainder;
 669                 ++i;
 670                 if (vaddr < vma->vm_end && remainder &&
 671                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 672                         /*
 673                          * We use pfn_offset to avoid touching the pageframes
 674                          * of this compound page.
 675                          */
 676                         goto same_page;
 677                 }
 678         }
 679         spin_unlock(&mm->page_table_lock);
 680         *length = remainder;
 681         *position = vaddr;
 682
 683         return i;
 684 }
 685
 686 void hugetlb_change_protection(struct vm_area_struct *vma,
 687                 unsigned long address, unsigned long end, pgprot_t newprot)
 688 {
 689         struct mm_struct *mm = vma->vm_mm;
 690         unsigned long start = address;
 691         pte_t *ptep;
 692         pte_t pte;
 693
 694         BUG_ON(address >= end);
 695         flush_cache_range(vma, address, end);
 696
 697         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 698         spin_lock(&mm->page_table_lock);
 699         for (; address < end; address += HPAGE_SIZE) {
 700                 ptep = huge_pte_offset(mm, address);
 701                 if (!ptep)
 702                         continue;
 703                 if (huge_pmd_unshare(mm, &address, ptep))
 704                         continue;
 705                 if (!pte_none(*ptep)) {
 706                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 707                         pte = pte_mkhuge(pte_modify(pte, newprot));
 708                         set_huge_pte_at(mm, address, ptep, pte);
 709                         lazy_mmu_prot_update(pte);
 710                 }
 711         }
 712         spin_unlock(&mm->page_table_lock);
 713         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 714
 715         flush_tlb_range(vma, start, end);
 716 }
 717
 718 struct file_region {
 719         struct list_head link;
 720         long from;
 721         long to;
 722 };
 723
 724 static long region_add(struct list_head *head, long f, long t)
 725 {
 726         struct file_region *rg, *nrg, *trg;
 727
 728         /* Locate the region we are either in or before. */
 729         list_for_each_entry(rg, head, link)
 730                 if (f <= rg->to)
 731                         break;
 732
 733         /* Round our left edge to the current segment if it encloses us. */
 734         if (f > rg->from)
 735                 f = rg->from;
 736
 737         /* Check for and consume any regions we now overlap with. */
 738         nrg = rg;
 739         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 740                 if (&rg->link == head)
 741                         break;
 742                 if (rg->from > t)
 743                         break;
 744
 745                 /* If this area reaches higher then extend our area to
 746                  * include it completely.  If this is not the first area
 747                  * which we intend to reuse, free it. */
 748                 if (rg->to > t)
 749                         t = rg->to;
 750                 if (rg != nrg) {
 751                         list_del(&rg->link);
 752                         kfree(rg);
 753                 }
 754         }
 755         nrg->from = f;
 756         nrg->to = t;
 757         return 0;
 758 }
 759
 760 static long region_chg(struct list_head *head, long f, long t)
 761 {
 762         struct file_region *rg, *nrg;
 763         long chg = 0;
 764
 765         /* Locate the region we are before or in. */
 766         list_for_each_entry(rg, head, link)
 767                 if (f <= rg->to)
 768                         break;
 769
 770         /* If we are below the current region then a new region is required.
 771          * Subtle, allocate a new region at the position but make it zero
 772          * size such that we can guarentee to record the reservation. */
 773         if (&rg->link == head || t < rg->from) {
 774                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
 775                 if (nrg == 0)
 776                         return -ENOMEM;
 777                 nrg->from = f;
 778                 nrg->to   = f;
 779                 INIT_LIST_HEAD(&nrg->link);
 780                 list_add(&nrg->link, rg->link.prev);
 781
 782                 return t - f;
 783         }
 784
 785         /* Round our left edge to the current segment if it encloses us. */
 786         if (f > rg->from)
 787                 f = rg->from;
 788         chg = t - f;
 789
 790         /* Check for and consume any regions we now overlap with. */
 791         list_for_each_entry(rg, rg->link.prev, link) {
 792                 if (&rg->link == head)
 793                         break;
 794                 if (rg->from > t)
 795                         return chg;
 796
 797                 /* We overlap with this area, if it extends futher than
 798                  * us then we must extend ourselves.  Account for its
 799                  * existing reservation. */
 800                 if (rg->to > t) {
 801                         chg += rg->to - t;
 802                         t = rg->to;
 803                 }
 804                 chg -= rg->to - rg->from;
 805         }
 806         return chg;
 807 }
 808
 809 static long region_truncate(struct list_head *head, long end)
 810 {
 811         struct file_region *rg, *trg;
 812         long chg = 0;
 813
 814         /* Locate the region we are either in or before. */
 815         list_for_each_entry(rg, head, link)
 816                 if (end <= rg->to)
 817                         break;
 818         if (&rg->link == head)
 819                 return 0;
 820
 821         /* If we are in the middle of a region then adjust it. */
 822         if (end > rg->from) {
 823                 chg = rg->to - end;
 824                 rg->to = end;
 825                 rg = list_entry(rg->link.next, typeof(*rg), link);
 826         }
 827
 828         /* Drop any remaining regions. */
 829         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 830                 if (&rg->link == head)
 831                         break;
 832                 chg += rg->to - rg->from;
 833                 list_del(&rg->link);
 834                 kfree(rg);
 835         }
 836         return chg;
 837 }
 838
 839 static int hugetlb_acct_memory(long delta)
 840 {
 841         int ret = -ENOMEM;
 842
 843         spin_lock(&hugetlb_lock);
 844         if ((delta + resv_huge_pages) <= free_huge_pages) {
 845                 resv_huge_pages += delta;
 846                 ret = 0;
 847         }
 848         spin_unlock(&hugetlb_lock);
 849         return ret;
 850 }
 851
 852 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
 853 {
 854         long ret, chg;
 855
 856         chg = region_chg(&inode->i_mapping->private_list, from, to);
 857         if (chg < 0)
 858                 return chg;
 859         /*
 860          * When cpuset is configured, it breaks the strict hugetlb page
 861          * reservation as the accounting is done on a global variable. Such
 862          * reservation is completely rubbish in the presence of cpuset because
 863          * the reservation is not checked against page availability for the
 864          * current cpuset. Application can still potentially OOM'ed by kernel
 865          * with lack of free htlb page in cpuset that the task is in.
 866          * Attempt to enforce strict accounting with cpuset is almost
 867          * impossible (or too ugly) because cpuset is too fluid that
 868          * task or memory node can be dynamically moved between cpusets.
 869          *
 870          * The change of semantics for shared hugetlb mapping with cpuset is
 871          * undesirable. However, in order to preserve some of the semantics,
 872          * we fall back to check against current free page availability as
 873          * a best attempt and hopefully to minimize the impact of changing
 874          * semantics that cpuset has.
 875          */
 876         if (chg > cpuset_mems_nr(free_huge_pages_node))
 877                 return -ENOMEM;
 878
 879         ret = hugetlb_acct_memory(chg);
 880         if (ret < 0)
 881                 return ret;
 882         region_add(&inode->i_mapping->private_list, from, to);
 883         return 0;
 884 }
 885
 886 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 887 {
 888         long chg = region_truncate(&inode->i_mapping->private_list, offset);
 889         hugetlb_acct_memory(freed - chg);
 890 }