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   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                         break;
  83         }
  84
  85         if (*z) {
  86                 page = list_entry(hugepage_freelists[nid].next,
  87                                   struct page, lru);
  88                 list_del(&page->lru);
  89                 free_huge_pages--;
  90                 free_huge_pages_node[nid]--;
  91         }
  92         return page;
  93 }
  94
  95 static void free_huge_page(struct page *page)
  96 {
  97         BUG_ON(page_count(page));
  98
  99         INIT_LIST_HEAD(&page->lru);
 100
 101         spin_lock(&hugetlb_lock);
 102         enqueue_huge_page(page);
 103         spin_unlock(&hugetlb_lock);
 104 }
 105
 106 static int alloc_fresh_huge_page(void)
 107 {
 108         static int prev_nid;
 109         struct page *page;
 110         static DEFINE_SPINLOCK(nid_lock);
 111         int nid;
 112
 113         spin_lock(&nid_lock);
 114         nid = next_node(prev_nid, node_online_map);
 115         if (nid == MAX_NUMNODES)
 116                 nid = first_node(node_online_map);
 117         prev_nid = nid;
 118         spin_unlock(&nid_lock);
 119
 120         page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 121                                         HUGETLB_PAGE_ORDER);
 122         if (page) {
 123                 set_compound_page_dtor(page, free_huge_page);
 124                 spin_lock(&hugetlb_lock);
 125                 nr_huge_pages++;
 126                 nr_huge_pages_node[page_to_nid(page)]++;
 127                 spin_unlock(&hugetlb_lock);
 128                 put_page(page); /* free it into the hugepage allocator */
 129                 return 1;
 130         }
 131         return 0;
 132 }
 133
 134 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 135                                     unsigned long addr)
 136 {
 137         struct page *page;
 138
 139         spin_lock(&hugetlb_lock);
 140         if (vma->vm_flags & VM_MAYSHARE)
 141                 resv_huge_pages--;
 142         else if (free_huge_pages <= resv_huge_pages)
 143                 goto fail;
 144
 145         page = dequeue_huge_page(vma, addr);
 146         if (!page)
 147                 goto fail;
 148
 149         spin_unlock(&hugetlb_lock);
 150         set_page_refcounted(page);
 151         return page;
 152
 153 fail:
 154         if (vma->vm_flags & VM_MAYSHARE)
 155                 resv_huge_pages++;
 156         spin_unlock(&hugetlb_lock);
 157         return NULL;
 158 }
 159
 160 static int __init hugetlb_init(void)
 161 {
 162         unsigned long i;
 163
 164         if (HPAGE_SHIFT == 0)
 165                 return 0;
 166
 167         for (i = 0; i < MAX_NUMNODES; ++i)
 168                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 169
 170         for (i = 0; i < max_huge_pages; ++i) {
 171                 if (!alloc_fresh_huge_page())
 172                         break;
 173         }
 174         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 175         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 176         return 0;
 177 }
 178 module_init(hugetlb_init);
 179
 180 static int __init hugetlb_setup(char *s)
 181 {
 182         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 183                 max_huge_pages = 0;
 184         return 1;
 185 }
 186 __setup("hugepages=", hugetlb_setup);
 187
 188 static unsigned int cpuset_mems_nr(unsigned int *array)
 189 {
 190         int node;
 191         unsigned int nr = 0;
 192
 193         for_each_node_mask(node, cpuset_current_mems_allowed)
 194                 nr += array[node];
 195
 196         return nr;
 197 }
 198
 199 #ifdef CONFIG_SYSCTL
 200 static void update_and_free_page(struct page *page)
 201 {
 202         int i;
 203         nr_huge_pages--;
 204         nr_huge_pages_node[page_to_nid(page)]--;
 205         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 206                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 207                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 208                                 1 << PG_private | 1<< PG_writeback);
 209         }
 210         page[1].lru.next = NULL;
 211         set_page_refcounted(page);
 212         __free_pages(page, HUGETLB_PAGE_ORDER);
 213 }
 214
 215 #ifdef CONFIG_HIGHMEM
 216 static void try_to_free_low(unsigned long count)
 217 {
 218         int i;
 219
 220         for (i = 0; i < MAX_NUMNODES; ++i) {
 221                 struct page *page, *next;
 222                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 223                         if (PageHighMem(page))
 224                                 continue;
 225                         list_del(&page->lru);
 226                         update_and_free_page(page);
 227                         free_huge_pages--;
 228                         free_huge_pages_node[page_to_nid(page)]--;
 229                         if (count >= nr_huge_pages)
 230                                 return;
 231                 }
 232         }
 233 }
 234 #else
 235 static inline void try_to_free_low(unsigned long count)
 236 {
 237 }
 238 #endif
 239
 240 static unsigned long set_max_huge_pages(unsigned long count)
 241 {
 242         while (count > nr_huge_pages) {
 243                 if (!alloc_fresh_huge_page())
 244                         return nr_huge_pages;
 245         }
 246         if (count >= nr_huge_pages)
 247                 return nr_huge_pages;
 248
 249         spin_lock(&hugetlb_lock);
 250         count = max(count, resv_huge_pages);
 251         try_to_free_low(count);
 252         while (count < nr_huge_pages) {
 253                 struct page *page = dequeue_huge_page(NULL, 0);
 254                 if (!page)
 255                         break;
 256                 update_and_free_page(page);
 257         }
 258         spin_unlock(&hugetlb_lock);
 259         return nr_huge_pages;
 260 }
 261
 262 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 263                            struct file *file, void __user *buffer,
 264                            size_t *length, loff_t *ppos)
 265 {
 266         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 267         max_huge_pages = set_max_huge_pages(max_huge_pages);
 268         return 0;
 269 }
 270
 271 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 272                         struct file *file, void __user *buffer,
 273                         size_t *length, loff_t *ppos)
 274 {
 275         proc_dointvec(table, write, file, buffer, length, ppos);
 276         if (hugepages_treat_as_movable)
 277                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
 278         else
 279                 htlb_alloc_mask = GFP_HIGHUSER;
 280         return 0;
 281 }
 282
 283 #endif /* CONFIG_SYSCTL */
 284
 285 int hugetlb_report_meminfo(char *buf)
 286 {
 287         return sprintf(buf,
 288                         "HugePages_Total: %5lu\n"
 289                         "HugePages_Free:  %5lu\n"
 290                         "HugePages_Rsvd:  %5lu\n"
 291                         "Hugepagesize:    %5lu kB\n",
 292                         nr_huge_pages,
 293                         free_huge_pages,
 294                         resv_huge_pages,
 295                         HPAGE_SIZE/1024);
 296 }
 297
 298 int hugetlb_report_node_meminfo(int nid, char *buf)
 299 {
 300         return sprintf(buf,
 301                 "Node %d HugePages_Total: %5u\n"
 302                 "Node %d HugePages_Free:  %5u\n",
 303                 nid, nr_huge_pages_node[nid],
 304                 nid, free_huge_pages_node[nid]);
 305 }
 306
 307 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 308 unsigned long hugetlb_total_pages(void)
 309 {
 310         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 311 }
 312
 313 /*
 314  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 315  * handle_mm_fault() to try to instantiate regular-sized pages in the
 316  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 317  * this far.
 318  */
 319 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 320 {
 321         BUG();
 322         return 0;
 323 }
 324
 325 struct vm_operations_struct hugetlb_vm_ops = {
 326         .fault = hugetlb_vm_op_fault,
 327 };
 328
 329 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 330                                 int writable)
 331 {
 332         pte_t entry;
 333
 334         if (writable) {
 335                 entry =
 336                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 337         } else {
 338                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 339         }
 340         entry = pte_mkyoung(entry);
 341         entry = pte_mkhuge(entry);
 342
 343         return entry;
 344 }
 345
 346 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 347                                    unsigned long address, pte_t *ptep)
 348 {
 349         pte_t entry;
 350
 351         entry = pte_mkwrite(pte_mkdirty(*ptep));
 352         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
 353                 update_mmu_cache(vma, address, entry);
 354                 lazy_mmu_prot_update(entry);
 355         }
 356 }
 357
 358
 359 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 360                             struct vm_area_struct *vma)
 361 {
 362         pte_t *src_pte, *dst_pte, entry;
 363         struct page *ptepage;
 364         unsigned long addr;
 365         int cow;
 366
 367         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 368
 369         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 370                 src_pte = huge_pte_offset(src, addr);
 371                 if (!src_pte)
 372                         continue;
 373                 dst_pte = huge_pte_alloc(dst, addr);
 374                 if (!dst_pte)
 375                         goto nomem;
 376                 spin_lock(&dst->page_table_lock);
 377                 spin_lock(&src->page_table_lock);
 378                 if (!pte_none(*src_pte)) {
 379                         if (cow)
 380                                 ptep_set_wrprotect(src, addr, src_pte);
 381                         entry = *src_pte;
 382                         ptepage = pte_page(entry);
 383                         get_page(ptepage);
 384                         set_huge_pte_at(dst, addr, dst_pte, entry);
 385                 }
 386                 spin_unlock(&src->page_table_lock);
 387                 spin_unlock(&dst->page_table_lock);
 388         }
 389         return 0;
 390
 391 nomem:
 392         return -ENOMEM;
 393 }
 394
 395 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 396                             unsigned long end)
 397 {
 398         struct mm_struct *mm = vma->vm_mm;
 399         unsigned long address;
 400         pte_t *ptep;
 401         pte_t pte;
 402         struct page *page;
 403         struct page *tmp;
 404         /*
 405          * A page gathering list, protected by per file i_mmap_lock. The
 406          * lock is used to avoid list corruption from multiple unmapping
 407          * of the same page since we are using page->lru.
 408          */
 409         LIST_HEAD(page_list);
 410
 411         WARN_ON(!is_vm_hugetlb_page(vma));
 412         BUG_ON(start & ~HPAGE_MASK);
 413         BUG_ON(end & ~HPAGE_MASK);
 414
 415         spin_lock(&mm->page_table_lock);
 416         for (address = start; address < end; address += HPAGE_SIZE) {
 417                 ptep = huge_pte_offset(mm, address);
 418                 if (!ptep)
 419                         continue;
 420
 421                 if (huge_pmd_unshare(mm, &address, ptep))
 422                         continue;
 423
 424                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 425                 if (pte_none(pte))
 426                         continue;
 427
 428                 page = pte_page(pte);
 429                 if (pte_dirty(pte))
 430                         set_page_dirty(page);
 431                 list_add(&page->lru, &page_list);
 432         }
 433         spin_unlock(&mm->page_table_lock);
 434         flush_tlb_range(vma, start, end);
 435         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 436                 list_del(&page->lru);
 437                 put_page(page);
 438         }
 439 }
 440
 441 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 442                           unsigned long end)
 443 {
 444         /*
 445          * It is undesirable to test vma->vm_file as it should be non-null
 446          * for valid hugetlb area. However, vm_file will be NULL in the error
 447          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 448          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 449          * to clean up. Since no pte has actually been setup, it is safe to
 450          * do nothing in this case.
 451          */
 452         if (vma->vm_file) {
 453                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 454                 __unmap_hugepage_range(vma, start, end);
 455                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 456         }
 457 }
 458
 459 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 460                         unsigned long address, pte_t *ptep, pte_t pte)
 461 {
 462         struct page *old_page, *new_page;
 463         int avoidcopy;
 464
 465         old_page = pte_page(pte);
 466
 467         /* If no-one else is actually using this page, avoid the copy
 468          * and just make the page writable */
 469         avoidcopy = (page_count(old_page) == 1);
 470         if (avoidcopy) {
 471                 set_huge_ptep_writable(vma, address, ptep);
 472                 return VM_FAULT_MINOR;
 473         }
 474
 475         page_cache_get(old_page);
 476         new_page = alloc_huge_page(vma, address);
 477
 478         if (!new_page) {
 479                 page_cache_release(old_page);
 480                 return VM_FAULT_OOM;
 481         }
 482
 483         spin_unlock(&mm->page_table_lock);
 484         copy_huge_page(new_page, old_page, address, vma);
 485         spin_lock(&mm->page_table_lock);
 486
 487         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 488         if (likely(pte_same(*ptep, pte))) {
 489                 /* Break COW */
 490                 set_huge_pte_at(mm, address, ptep,
 491                                 make_huge_pte(vma, new_page, 1));
 492                 /* Make the old page be freed below */
 493                 new_page = old_page;
 494         }
 495         page_cache_release(new_page);
 496         page_cache_release(old_page);
 497         return VM_FAULT_MINOR;
 498 }
 499
 500 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 501                         unsigned long address, pte_t *ptep, int write_access)
 502 {
 503         int ret = VM_FAULT_SIGBUS;
 504         unsigned long idx;
 505         unsigned long size;
 506         struct page *page;
 507         struct address_space *mapping;
 508         pte_t new_pte;
 509
 510         mapping = vma->vm_file->f_mapping;
 511         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 512                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 513
 514         /*
 515          * Use page lock to guard against racing truncation
 516          * before we get page_table_lock.
 517          */
 518 retry:
 519         page = find_lock_page(mapping, idx);
 520         if (!page) {
 521                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 522                 if (idx >= size)
 523                         goto out;
 524                 if (hugetlb_get_quota(mapping))
 525                         goto out;
 526                 page = alloc_huge_page(vma, address);
 527                 if (!page) {
 528                         hugetlb_put_quota(mapping);
 529                         ret = VM_FAULT_OOM;
 530                         goto out;
 531                 }
 532                 clear_huge_page(page, address);
 533
 534                 if (vma->vm_flags & VM_SHARED) {
 535                         int err;
 536
 537                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 538                         if (err) {
 539                                 put_page(page);
 540                                 hugetlb_put_quota(mapping);
 541                                 if (err == -EEXIST)
 542                                         goto retry;
 543                                 goto out;
 544                         }
 545                 } else
 546                         lock_page(page);
 547         }
 548
 549         spin_lock(&mm->page_table_lock);
 550         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 551         if (idx >= size)
 552                 goto backout;
 553
 554         ret = VM_FAULT_MINOR;
 555         if (!pte_none(*ptep))
 556                 goto backout;
 557
 558         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 559                                 && (vma->vm_flags & VM_SHARED)));
 560         set_huge_pte_at(mm, address, ptep, new_pte);
 561
 562         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 563                 /* Optimization, do the COW without a second fault */
 564                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 565         }
 566
 567         spin_unlock(&mm->page_table_lock);
 568         unlock_page(page);
 569 out:
 570         return ret;
 571
 572 backout:
 573         spin_unlock(&mm->page_table_lock);
 574         hugetlb_put_quota(mapping);
 575         unlock_page(page);
 576         put_page(page);
 577         goto out;
 578 }
 579
 580 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 581                         unsigned long address, int write_access)
 582 {
 583         pte_t *ptep;
 584         pte_t entry;
 585         int ret;
 586         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 587
 588         ptep = huge_pte_alloc(mm, address);
 589         if (!ptep)
 590                 return VM_FAULT_OOM;
 591
 592         /*
 593          * Serialize hugepage allocation and instantiation, so that we don't
 594          * get spurious allocation failures if two CPUs race to instantiate
 595          * the same page in the page cache.
 596          */
 597         mutex_lock(&hugetlb_instantiation_mutex);
 598         entry = *ptep;
 599         if (pte_none(entry)) {
 600                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 601                 mutex_unlock(&hugetlb_instantiation_mutex);
 602                 return ret;
 603         }
 604
 605         ret = VM_FAULT_MINOR;
 606
 607         spin_lock(&mm->page_table_lock);
 608         /* Check for a racing update before calling hugetlb_cow */
 609         if (likely(pte_same(entry, *ptep)))
 610                 if (write_access && !pte_write(entry))
 611                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 612         spin_unlock(&mm->page_table_lock);
 613         mutex_unlock(&hugetlb_instantiation_mutex);
 614
 615         return ret;
 616 }
 617
 618 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 619                         struct page **pages, struct vm_area_struct **vmas,
 620                         unsigned long *position, int *length, int i)
 621 {
 622         unsigned long pfn_offset;
 623         unsigned long vaddr = *position;
 624         int remainder = *length;
 625
 626         spin_lock(&mm->page_table_lock);
 627         while (vaddr < vma->vm_end && remainder) {
 628                 pte_t *pte;
 629                 struct page *page;
 630
 631                 /*
 632                  * Some archs (sparc64, sh*) have multiple pte_ts to
 633                  * each hugepage.  We have to make * sure we get the
 634                  * first, for the page indexing below to work.
 635                  */
 636                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 637
 638                 if (!pte || pte_none(*pte)) {
 639                         int ret;
 640
 641                         spin_unlock(&mm->page_table_lock);
 642                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 643                         spin_lock(&mm->page_table_lock);
 644                         if (ret == VM_FAULT_MINOR)
 645                                 continue;
 646
 647                         remainder = 0;
 648                         if (!i)
 649                                 i = -EFAULT;
 650                         break;
 651                 }
 652
 653                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 654                 page = pte_page(*pte);
 655 same_page:
 656                 if (pages) {
 657                         get_page(page);
 658                         pages[i] = page + pfn_offset;
 659                 }
 660
 661                 if (vmas)
 662                         vmas[i] = vma;
 663
 664                 vaddr += PAGE_SIZE;
 665                 ++pfn_offset;
 666                 --remainder;
 667                 ++i;
 668                 if (vaddr < vma->vm_end && remainder &&
 669                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 670                         /*
 671                          * We use pfn_offset to avoid touching the pageframes
 672                          * of this compound page.
 673                          */
 674                         goto same_page;
 675                 }
 676         }
 677         spin_unlock(&mm->page_table_lock);
 678         *length = remainder;
 679         *position = vaddr;
 680
 681         return i;
 682 }
 683
 684 void hugetlb_change_protection(struct vm_area_struct *vma,
 685                 unsigned long address, unsigned long end, pgprot_t newprot)
 686 {
 687         struct mm_struct *mm = vma->vm_mm;
 688         unsigned long start = address;
 689         pte_t *ptep;
 690         pte_t pte;
 691
 692         BUG_ON(address >= end);
 693         flush_cache_range(vma, address, end);
 694
 695         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 696         spin_lock(&mm->page_table_lock);
 697         for (; address < end; address += HPAGE_SIZE) {
 698                 ptep = huge_pte_offset(mm, address);
 699                 if (!ptep)
 700                         continue;
 701                 if (huge_pmd_unshare(mm, &address, ptep))
 702                         continue;
 703                 if (!pte_none(*ptep)) {
 704                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 705                         pte = pte_mkhuge(pte_modify(pte, newprot));
 706                         set_huge_pte_at(mm, address, ptep, pte);
 707                         lazy_mmu_prot_update(pte);
 708                 }
 709         }
 710         spin_unlock(&mm->page_table_lock);
 711         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 712
 713         flush_tlb_range(vma, start, end);
 714 }
 715
 716 struct file_region {
 717         struct list_head link;
 718         long from;
 719         long to;
 720 };
 721
 722 static long region_add(struct list_head *head, long f, long t)
 723 {
 724         struct file_region *rg, *nrg, *trg;
 725
 726         /* Locate the region we are either in or before. */
 727         list_for_each_entry(rg, head, link)
 728                 if (f <= rg->to)
 729                         break;
 730
 731         /* Round our left edge to the current segment if it encloses us. */
 732         if (f > rg->from)
 733                 f = rg->from;
 734
 735         /* Check for and consume any regions we now overlap with. */
 736         nrg = rg;
 737         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 738                 if (&rg->link == head)
 739                         break;
 740                 if (rg->from > t)
 741                         break;
 742
 743                 /* If this area reaches higher then extend our area to
 744                  * include it completely.  If this is not the first area
 745                  * which we intend to reuse, free it. */
 746                 if (rg->to > t)
 747                         t = rg->to;
 748                 if (rg != nrg) {
 749                         list_del(&rg->link);
 750                         kfree(rg);
 751                 }
 752         }
 753         nrg->from = f;
 754         nrg->to = t;
 755         return 0;
 756 }
 757
 758 static long region_chg(struct list_head *head, long f, long t)
 759 {
 760         struct file_region *rg, *nrg;
 761         long chg = 0;
 762
 763         /* Locate the region we are before or in. */
 764         list_for_each_entry(rg, head, link)
 765                 if (f <= rg->to)
 766                         break;
 767
 768         /* If we are below the current region then a new region is required.
 769          * Subtle, allocate a new region at the position but make it zero
 770          * size such that we can guarentee to record the reservation. */
 771         if (&rg->link == head || t < rg->from) {
 772                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
 773                 if (nrg == 0)
 774                         return -ENOMEM;
 775                 nrg->from = f;
 776                 nrg->to   = f;
 777                 INIT_LIST_HEAD(&nrg->link);
 778                 list_add(&nrg->link, rg->link.prev);
 779
 780                 return t - f;
 781         }
 782
 783         /* Round our left edge to the current segment if it encloses us. */
 784         if (f > rg->from)
 785                 f = rg->from;
 786         chg = t - f;
 787
 788         /* Check for and consume any regions we now overlap with. */
 789         list_for_each_entry(rg, rg->link.prev, link) {
 790                 if (&rg->link == head)
 791                         break;
 792                 if (rg->from > t)
 793                         return chg;
 794
 795                 /* We overlap with this area, if it extends futher than
 796                  * us then we must extend ourselves.  Account for its
 797                  * existing reservation. */
 798                 if (rg->to > t) {
 799                         chg += rg->to - t;
 800                         t = rg->to;
 801                 }
 802                 chg -= rg->to - rg->from;
 803         }
 804         return chg;
 805 }
 806
 807 static long region_truncate(struct list_head *head, long end)
 808 {
 809         struct file_region *rg, *trg;
 810         long chg = 0;
 811
 812         /* Locate the region we are either in or before. */
 813         list_for_each_entry(rg, head, link)
 814                 if (end <= rg->to)
 815                         break;
 816         if (&rg->link == head)
 817                 return 0;
 818
 819         /* If we are in the middle of a region then adjust it. */
 820         if (end > rg->from) {
 821                 chg = rg->to - end;
 822                 rg->to = end;
 823                 rg = list_entry(rg->link.next, typeof(*rg), link);
 824         }
 825
 826         /* Drop any remaining regions. */
 827         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 828                 if (&rg->link == head)
 829                         break;
 830                 chg += rg->to - rg->from;
 831                 list_del(&rg->link);
 832                 kfree(rg);
 833         }
 834         return chg;
 835 }
 836
 837 static int hugetlb_acct_memory(long delta)
 838 {
 839         int ret = -ENOMEM;
 840
 841         spin_lock(&hugetlb_lock);
 842         if ((delta + resv_huge_pages) <= free_huge_pages) {
 843                 resv_huge_pages += delta;
 844                 ret = 0;
 845         }
 846         spin_unlock(&hugetlb_lock);
 847         return ret;
 848 }
 849
 850 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
 851 {
 852         long ret, chg;
 853
 854         chg = region_chg(&inode->i_mapping->private_list, from, to);
 855         if (chg < 0)
 856                 return chg;
 857         /*
 858          * When cpuset is configured, it breaks the strict hugetlb page
 859          * reservation as the accounting is done on a global variable. Such
 860          * reservation is completely rubbish in the presence of cpuset because
 861          * the reservation is not checked against page availability for the
 862          * current cpuset. Application can still potentially OOM'ed by kernel
 863          * with lack of free htlb page in cpuset that the task is in.
 864          * Attempt to enforce strict accounting with cpuset is almost
 865          * impossible (or too ugly) because cpuset is too fluid that
 866          * task or memory node can be dynamically moved between cpusets.
 867          *
 868          * The change of semantics for shared hugetlb mapping with cpuset is
 869          * undesirable. However, in order to preserve some of the semantics,
 870          * we fall back to check against current free page availability as
 871          * a best attempt and hopefully to minimize the impact of changing
 872          * semantics that cpuset has.
 873          */
 874         if (chg > cpuset_mems_nr(free_huge_pages_node))
 875                 return -ENOMEM;
 876
 877         ret = hugetlb_acct_memory(chg);
 878         if (ret < 0)
 879                 return ret;
 880         region_add(&inode->i_mapping->private_list, from, to);
 881         return 0;
 882 }
 883
 884 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 885 {
 886         long chg = region_truncate(&inode->i_mapping->private_list, offset);
 887         hugetlb_acct_memory(freed - chg);
 888 }