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         if (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
 336 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 337                             struct vm_area_struct *vma)
 338 {
 339         pte_t *src_pte, *dst_pte, entry;
 340         struct page *ptepage;
 341         unsigned long addr;
 342         int cow;
 343
 344         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 345
 346         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 347                 src_pte = huge_pte_offset(src, addr);
 348                 if (!src_pte)
 349                         continue;
 350                 dst_pte = huge_pte_alloc(dst, addr);
 351                 if (!dst_pte)
 352                         goto nomem;
 353                 spin_lock(&dst->page_table_lock);
 354                 spin_lock(&src->page_table_lock);
 355                 if (!pte_none(*src_pte)) {
 356                         if (cow)
 357                                 ptep_set_wrprotect(src, addr, src_pte);
 358                         entry = *src_pte;
 359                         ptepage = pte_page(entry);
 360                         get_page(ptepage);
 361                         set_huge_pte_at(dst, addr, dst_pte, entry);
 362                 }
 363                 spin_unlock(&src->page_table_lock);
 364                 spin_unlock(&dst->page_table_lock);
 365         }
 366         return 0;
 367
 368 nomem:
 369         return -ENOMEM;
 370 }
 371
 372 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 373                             unsigned long end)
 374 {
 375         struct mm_struct *mm = vma->vm_mm;
 376         unsigned long address;
 377         pte_t *ptep;
 378         pte_t pte;
 379         struct page *page;
 380         struct page *tmp;
 381         /*
 382          * A page gathering list, protected by per file i_mmap_lock. The
 383          * lock is used to avoid list corruption from multiple unmapping
 384          * of the same page since we are using page->lru.
 385          */
 386         LIST_HEAD(page_list);
 387
 388         WARN_ON(!is_vm_hugetlb_page(vma));
 389         BUG_ON(start & ~HPAGE_MASK);
 390         BUG_ON(end & ~HPAGE_MASK);
 391
 392         spin_lock(&mm->page_table_lock);
 393         for (address = start; address < end; address += HPAGE_SIZE) {
 394                 ptep = huge_pte_offset(mm, address);
 395                 if (!ptep)
 396                         continue;
 397
 398                 if (huge_pmd_unshare(mm, &address, ptep))
 399                         continue;
 400
 401                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 402                 if (pte_none(pte))
 403                         continue;
 404
 405                 page = pte_page(pte);
 406                 if (pte_dirty(pte))
 407                         set_page_dirty(page);
 408                 list_add(&page->lru, &page_list);
 409         }
 410         spin_unlock(&mm->page_table_lock);
 411         flush_tlb_range(vma, start, end);
 412         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 413                 list_del(&page->lru);
 414                 put_page(page);
 415         }
 416 }
 417
 418 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 419                           unsigned long end)
 420 {
 421         /*
 422          * It is undesirable to test vma->vm_file as it should be non-null
 423          * for valid hugetlb area. However, vm_file will be NULL in the error
 424          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 425          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 426          * to clean up. Since no pte has actually been setup, it is safe to
 427          * do nothing in this case.
 428          */
 429         if (vma->vm_file) {
 430                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 431                 __unmap_hugepage_range(vma, start, end);
 432                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 433         }
 434 }
 435
 436 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 437                         unsigned long address, pte_t *ptep, pte_t pte)
 438 {
 439         struct page *old_page, *new_page;
 440         int avoidcopy;
 441
 442         old_page = pte_page(pte);
 443
 444         /* If no-one else is actually using this page, avoid the copy
 445          * and just make the page writable */
 446         avoidcopy = (page_count(old_page) == 1);
 447         if (avoidcopy) {
 448                 set_huge_ptep_writable(vma, address, ptep);
 449                 return VM_FAULT_MINOR;
 450         }
 451
 452         page_cache_get(old_page);
 453         new_page = alloc_huge_page(vma, address);
 454
 455         if (!new_page) {
 456                 page_cache_release(old_page);
 457                 return VM_FAULT_OOM;
 458         }
 459
 460         spin_unlock(&mm->page_table_lock);
 461         copy_huge_page(new_page, old_page, address, vma);
 462         spin_lock(&mm->page_table_lock);
 463
 464         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 465         if (likely(pte_same(*ptep, pte))) {
 466                 /* Break COW */
 467                 set_huge_pte_at(mm, address, ptep,
 468                                 make_huge_pte(vma, new_page, 1));
 469                 /* Make the old page be freed below */
 470                 new_page = old_page;
 471         }
 472         page_cache_release(new_page);
 473         page_cache_release(old_page);
 474         return VM_FAULT_MINOR;
 475 }
 476
 477 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 478                         unsigned long address, pte_t *ptep, int write_access)
 479 {
 480         int ret = VM_FAULT_SIGBUS;
 481         unsigned long idx;
 482         unsigned long size;
 483         struct page *page;
 484         struct address_space *mapping;
 485         pte_t new_pte;
 486
 487         mapping = vma->vm_file->f_mapping;
 488         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 489                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 490
 491         /*
 492          * Use page lock to guard against racing truncation
 493          * before we get page_table_lock.
 494          */
 495 retry:
 496         page = find_lock_page(mapping, idx);
 497         if (!page) {
 498                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 499                 if (idx >= size)
 500                         goto out;
 501                 if (hugetlb_get_quota(mapping))
 502                         goto out;
 503                 page = alloc_huge_page(vma, address);
 504                 if (!page) {
 505                         hugetlb_put_quota(mapping);
 506                         ret = VM_FAULT_OOM;
 507                         goto out;
 508                 }
 509                 clear_huge_page(page, address);
 510
 511                 if (vma->vm_flags & VM_SHARED) {
 512                         int err;
 513
 514                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 515                         if (err) {
 516                                 put_page(page);
 517                                 hugetlb_put_quota(mapping);
 518                                 if (err == -EEXIST)
 519                                         goto retry;
 520                                 goto out;
 521                         }
 522                 } else
 523                         lock_page(page);
 524         }
 525
 526         spin_lock(&mm->page_table_lock);
 527         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 528         if (idx >= size)
 529                 goto backout;
 530
 531         ret = VM_FAULT_MINOR;
 532         if (!pte_none(*ptep))
 533                 goto backout;
 534
 535         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 536                                 && (vma->vm_flags & VM_SHARED)));
 537         set_huge_pte_at(mm, address, ptep, new_pte);
 538
 539         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 540                 /* Optimization, do the COW without a second fault */
 541                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 542         }
 543
 544         spin_unlock(&mm->page_table_lock);
 545         unlock_page(page);
 546 out:
 547         return ret;
 548
 549 backout:
 550         spin_unlock(&mm->page_table_lock);
 551         hugetlb_put_quota(mapping);
 552         unlock_page(page);
 553         put_page(page);
 554         goto out;
 555 }
 556
 557 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 558                         unsigned long address, int write_access)
 559 {
 560         pte_t *ptep;
 561         pte_t entry;
 562         int ret;
 563         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 564
 565         ptep = huge_pte_alloc(mm, address);
 566         if (!ptep)
 567                 return VM_FAULT_OOM;
 568
 569         /*
 570          * Serialize hugepage allocation and instantiation, so that we don't
 571          * get spurious allocation failures if two CPUs race to instantiate
 572          * the same page in the page cache.
 573          */
 574         mutex_lock(&hugetlb_instantiation_mutex);
 575         entry = *ptep;
 576         if (pte_none(entry)) {
 577                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 578                 mutex_unlock(&hugetlb_instantiation_mutex);
 579                 return ret;
 580         }
 581
 582         ret = VM_FAULT_MINOR;
 583
 584         spin_lock(&mm->page_table_lock);
 585         /* Check for a racing update before calling hugetlb_cow */
 586         if (likely(pte_same(entry, *ptep)))
 587                 if (write_access && !pte_write(entry))
 588                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 589         spin_unlock(&mm->page_table_lock);
 590         mutex_unlock(&hugetlb_instantiation_mutex);
 591
 592         return ret;
 593 }
 594
 595 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 596                         struct page **pages, struct vm_area_struct **vmas,
 597                         unsigned long *position, int *length, int i)
 598 {
 599         unsigned long pfn_offset;
 600         unsigned long vaddr = *position;
 601         int remainder = *length;
 602
 603         spin_lock(&mm->page_table_lock);
 604         while (vaddr < vma->vm_end && remainder) {
 605                 pte_t *pte;
 606                 struct page *page;
 607
 608                 /*
 609                  * Some archs (sparc64, sh*) have multiple pte_ts to
 610                  * each hugepage.  We have to make * sure we get the
 611                  * first, for the page indexing below to work.
 612                  */
 613                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 614
 615                 if (!pte || pte_none(*pte)) {
 616                         int ret;
 617
 618                         spin_unlock(&mm->page_table_lock);
 619                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 620                         spin_lock(&mm->page_table_lock);
 621                         if (ret == VM_FAULT_MINOR)
 622                                 continue;
 623
 624                         remainder = 0;
 625                         if (!i)
 626                                 i = -EFAULT;
 627                         break;
 628                 }
 629
 630                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 631                 page = pte_page(*pte);
 632 same_page:
 633                 if (pages) {
 634                         get_page(page);
 635                         pages[i] = page + pfn_offset;
 636                 }
 637
 638                 if (vmas)
 639                         vmas[i] = vma;
 640
 641                 vaddr += PAGE_SIZE;
 642                 ++pfn_offset;
 643                 --remainder;
 644                 ++i;
 645                 if (vaddr < vma->vm_end && remainder &&
 646                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 647                         /*
 648                          * We use pfn_offset to avoid touching the pageframes
 649                          * of this compound page.
 650                          */
 651                         goto same_page;
 652                 }
 653         }
 654         spin_unlock(&mm->page_table_lock);
 655         *length = remainder;
 656         *position = vaddr;
 657
 658         return i;
 659 }
 660
 661 void hugetlb_change_protection(struct vm_area_struct *vma,
 662                 unsigned long address, unsigned long end, pgprot_t newprot)
 663 {
 664         struct mm_struct *mm = vma->vm_mm;
 665         unsigned long start = address;
 666         pte_t *ptep;
 667         pte_t pte;
 668
 669         BUG_ON(address >= end);
 670         flush_cache_range(vma, address, end);
 671
 672         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 673         spin_lock(&mm->page_table_lock);
 674         for (; address < end; address += HPAGE_SIZE) {
 675                 ptep = huge_pte_offset(mm, address);
 676                 if (!ptep)
 677                         continue;
 678                 if (huge_pmd_unshare(mm, &address, ptep))
 679                         continue;
 680                 if (!pte_none(*ptep)) {
 681                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 682                         pte = pte_mkhuge(pte_modify(pte, newprot));
 683                         set_huge_pte_at(mm, address, ptep, pte);
 684                         lazy_mmu_prot_update(pte);
 685                 }
 686         }
 687         spin_unlock(&mm->page_table_lock);
 688         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 689
 690         flush_tlb_range(vma, start, end);
 691 }
 692
 693 struct file_region {
 694         struct list_head link;
 695         long from;
 696         long to;
 697 };
 698
 699 static long region_add(struct list_head *head, long f, long t)
 700 {
 701         struct file_region *rg, *nrg, *trg;
 702
 703         /* Locate the region we are either in or before. */
 704         list_for_each_entry(rg, head, link)
 705                 if (f <= rg->to)
 706                         break;
 707
 708         /* Round our left edge to the current segment if it encloses us. */
 709         if (f > rg->from)
 710                 f = rg->from;
 711
 712         /* Check for and consume any regions we now overlap with. */
 713         nrg = rg;
 714         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 715                 if (&rg->link == head)
 716                         break;
 717                 if (rg->from > t)
 718                         break;
 719
 720                 /* If this area reaches higher then extend our area to
 721                  * include it completely.  If this is not the first area
 722                  * which we intend to reuse, free it. */
 723                 if (rg->to > t)
 724                         t = rg->to;
 725                 if (rg != nrg) {
 726                         list_del(&rg->link);
 727                         kfree(rg);
 728                 }
 729         }
 730         nrg->from = f;
 731         nrg->to = t;
 732         return 0;
 733 }
 734
 735 static long region_chg(struct list_head *head, long f, long t)
 736 {
 737         struct file_region *rg, *nrg;
 738         long chg = 0;
 739
 740         /* Locate the region we are before or in. */
 741         list_for_each_entry(rg, head, link)
 742                 if (f <= rg->to)
 743                         break;
 744
 745         /* If we are below the current region then a new region is required.
 746          * Subtle, allocate a new region at the position but make it zero
 747          * size such that we can guarentee to record the reservation. */
 748         if (&rg->link == head || t < rg->from) {
 749                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
 750                 if (nrg == 0)
 751                         return -ENOMEM;
 752                 nrg->from = f;
 753                 nrg->to   = f;
 754                 INIT_LIST_HEAD(&nrg->link);
 755                 list_add(&nrg->link, rg->link.prev);
 756
 757                 return t - f;
 758         }
 759
 760         /* Round our left edge to the current segment if it encloses us. */
 761         if (f > rg->from)
 762                 f = rg->from;
 763         chg = t - f;
 764
 765         /* Check for and consume any regions we now overlap with. */
 766         list_for_each_entry(rg, rg->link.prev, link) {
 767                 if (&rg->link == head)
 768                         break;
 769                 if (rg->from > t)
 770                         return chg;
 771
 772                 /* We overlap with this area, if it extends futher than
 773                  * us then we must extend ourselves.  Account for its
 774                  * existing reservation. */
 775                 if (rg->to > t) {
 776                         chg += rg->to - t;
 777                         t = rg->to;
 778                 }
 779                 chg -= rg->to - rg->from;
 780         }
 781         return chg;
 782 }
 783
 784 static long region_truncate(struct list_head *head, long end)
 785 {
 786         struct file_region *rg, *trg;
 787         long chg = 0;
 788
 789         /* Locate the region we are either in or before. */
 790         list_for_each_entry(rg, head, link)
 791                 if (end <= rg->to)
 792                         break;
 793         if (&rg->link == head)
 794                 return 0;
 795
 796         /* If we are in the middle of a region then adjust it. */
 797         if (end > rg->from) {
 798                 chg = rg->to - end;
 799                 rg->to = end;
 800                 rg = list_entry(rg->link.next, typeof(*rg), link);
 801         }
 802
 803         /* Drop any remaining regions. */
 804         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 805                 if (&rg->link == head)
 806                         break;
 807                 chg += rg->to - rg->from;
 808                 list_del(&rg->link);
 809                 kfree(rg);
 810         }
 811         return chg;
 812 }
 813
 814 static int hugetlb_acct_memory(long delta)
 815 {
 816         int ret = -ENOMEM;
 817
 818         spin_lock(&hugetlb_lock);
 819         if ((delta + resv_huge_pages) <= free_huge_pages) {
 820                 resv_huge_pages += delta;
 821                 ret = 0;
 822         }
 823         spin_unlock(&hugetlb_lock);
 824         return ret;
 825 }
 826
 827 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
 828 {
 829         long ret, chg;
 830
 831         chg = region_chg(&inode->i_mapping->private_list, from, to);
 832         if (chg < 0)
 833                 return chg;
 834         /*
 835          * When cpuset is configured, it breaks the strict hugetlb page
 836          * reservation as the accounting is done on a global variable. Such
 837          * reservation is completely rubbish in the presence of cpuset because
 838          * the reservation is not checked against page availability for the
 839          * current cpuset. Application can still potentially OOM'ed by kernel
 840          * with lack of free htlb page in cpuset that the task is in.
 841          * Attempt to enforce strict accounting with cpuset is almost
 842          * impossible (or too ugly) because cpuset is too fluid that
 843          * task or memory node can be dynamically moved between cpusets.
 844          *
 845          * The change of semantics for shared hugetlb mapping with cpuset is
 846          * undesirable. However, in order to preserve some of the semantics,
 847          * we fall back to check against current free page availability as
 848          * a best attempt and hopefully to minimize the impact of changing
 849          * semantics that cpuset has.
 850          */
 851         if (chg > cpuset_mems_nr(free_huge_pages_node))
 852                 return -ENOMEM;
 853
 854         ret = hugetlb_acct_memory(chg);
 855         if (ret < 0)
 856                 return ret;
 857         region_add(&inode->i_mapping->private_list, from, to);
 858         return 0;
 859 }
 860
 861 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 862 {
 863         long chg = region_truncate(&inode->i_mapping->private_list, offset);
 864         hugetlb_acct_memory(freed - chg);
 865 }