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