mm/hugetlb.c

   1 /*
   2  * Generic hugetlb support.
   3  * (C) William Irwin, April 2004
   4  */
   5 #include <linux/gfp.h>
   6 #include <linux/list.h>
   7 #include <linux/init.h>
   8 #include <linux/module.h>
   9 #include <linux/mm.h>
  10 #include <linux/sysctl.h>
  11 #include <linux/highmem.h>
  12 #include <linux/nodemask.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/mempolicy.h>
  15 #include <linux/cpuset.h>
  16 #include <linux/mutex.h>
  17
  18 #include <asm/page.h>
  19 #include <asm/pgtable.h>
  20
  21 #include <linux/hugetlb.h>
  22 #include "internal.h"
  23
  24 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  25 static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
  26 unsigned long max_huge_pages;
  27 static struct list_head hugepage_freelists[MAX_NUMNODES];
  28 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  29 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  30 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
  31 unsigned long hugepages_treat_as_movable;
  32
  33 /*
  34  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  35  */
  36 static DEFINE_SPINLOCK(hugetlb_lock);
  37
  38 static void clear_huge_page(struct page *page, unsigned long addr)
  39 {
  40         int i;
  41
  42         might_sleep();
  43         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  44                 cond_resched();
  45                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
  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 mempolicy *mpol;
  75         struct zonelist *zonelist = huge_zonelist(vma, address,
  76                                         htlb_alloc_mask, &mpol);
  77         struct zone **z;
  78
  79         for (z = zonelist->zones; *z; z++) {
  80                 nid = zone_to_nid(*z);
  81                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
  82                     !list_empty(&hugepage_freelists[nid])) {
  83                         page = list_entry(hugepage_freelists[nid].next,
  84                                           struct page, lru);
  85                         list_del(&page->lru);
  86                         free_huge_pages--;
  87                         free_huge_pages_node[nid]--;
  88                         break;
  89                 }
  90         }
  91         mpol_free(mpol);        /* unref if mpol !NULL */
  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         int nid;
 111
 112         /*
 113          * Copy static prev_nid to local nid, work on that, then copy it
 114          * back to prev_nid afterwards: otherwise there's a window in which
 115          * a racer might pass invalid nid MAX_NUMNODES to alloc_pages_node.
 116          * But we don't need to use a spin_lock here: it really doesn't
 117          * matter if occasionally a racer chooses the same nid as we do.
 118          */
 119         nid = next_node(prev_nid, node_online_map);
 120         if (nid == MAX_NUMNODES)
 121                 nid = first_node(node_online_map);
 122         prev_nid = nid;
 123
 124         page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 125                                         HUGETLB_PAGE_ORDER);
 126         if (page) {
 127                 set_compound_page_dtor(page, free_huge_page);
 128                 spin_lock(&hugetlb_lock);
 129                 nr_huge_pages++;
 130                 nr_huge_pages_node[page_to_nid(page)]++;
 131                 spin_unlock(&hugetlb_lock);
 132                 put_page(page); /* free it into the hugepage allocator */
 133                 return 1;
 134         }
 135         return 0;
 136 }
 137
 138 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 139                                     unsigned long addr)
 140 {
 141         struct page *page;
 142
 143         spin_lock(&hugetlb_lock);
 144         if (vma->vm_flags & VM_MAYSHARE)
 145                 resv_huge_pages--;
 146         else if (free_huge_pages <= resv_huge_pages)
 147                 goto fail;
 148
 149         page = dequeue_huge_page(vma, addr);
 150         if (!page)
 151                 goto fail;
 152
 153         spin_unlock(&hugetlb_lock);
 154         set_page_refcounted(page);
 155         return page;
 156
 157 fail:
 158         if (vma->vm_flags & VM_MAYSHARE)
 159                 resv_huge_pages++;
 160         spin_unlock(&hugetlb_lock);
 161         return NULL;
 162 }
 163
 164 static int __init hugetlb_init(void)
 165 {
 166         unsigned long i;
 167
 168         if (HPAGE_SHIFT == 0)
 169                 return 0;
 170
 171         for (i = 0; i < MAX_NUMNODES; ++i)
 172                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 173
 174         for (i = 0; i < max_huge_pages; ++i) {
 175                 if (!alloc_fresh_huge_page())
 176                         break;
 177         }
 178         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 179         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 180         return 0;
 181 }
 182 module_init(hugetlb_init);
 183
 184 static int __init hugetlb_setup(char *s)
 185 {
 186         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 187                 max_huge_pages = 0;
 188         return 1;
 189 }
 190 __setup("hugepages=", hugetlb_setup);
 191
 192 static unsigned int cpuset_mems_nr(unsigned int *array)
 193 {
 194         int node;
 195         unsigned int nr = 0;
 196
 197         for_each_node_mask(node, cpuset_current_mems_allowed)
 198                 nr += array[node];
 199
 200         return nr;
 201 }
 202
 203 #ifdef CONFIG_SYSCTL
 204 static void update_and_free_page(struct page *page)
 205 {
 206         int i;
 207         nr_huge_pages--;
 208         nr_huge_pages_node[page_to_nid(page)]--;
 209         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 210                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 211                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 212                                 1 << PG_private | 1<< PG_writeback);
 213         }
 214         set_compound_page_dtor(page, NULL);
 215         set_page_refcounted(page);
 216         __free_pages(page, HUGETLB_PAGE_ORDER);
 217 }
 218
 219 #ifdef CONFIG_HIGHMEM
 220 static void try_to_free_low(unsigned long count)
 221 {
 222         int i;
 223
 224         for (i = 0; i < MAX_NUMNODES; ++i) {
 225                 struct page *page, *next;
 226                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 227                         if (PageHighMem(page))
 228                                 continue;
 229                         list_del(&page->lru);
 230                         update_and_free_page(page);
 231                         free_huge_pages--;
 232                         free_huge_pages_node[page_to_nid(page)]--;
 233                         if (count >= nr_huge_pages)
 234                                 return;
 235                 }
 236         }
 237 }
 238 #else
 239 static inline void try_to_free_low(unsigned long count)
 240 {
 241 }
 242 #endif
 243
 244 static unsigned long set_max_huge_pages(unsigned long count)
 245 {
 246         while (count > nr_huge_pages) {
 247                 if (!alloc_fresh_huge_page())
 248                         return nr_huge_pages;
 249         }
 250         if (count >= nr_huge_pages)
 251                 return nr_huge_pages;
 252
 253         spin_lock(&hugetlb_lock);
 254         count = max(count, resv_huge_pages);
 255         try_to_free_low(count);
 256         while (count < nr_huge_pages) {
 257                 struct page *page = dequeue_huge_page(NULL, 0);
 258                 if (!page)
 259                         break;
 260                 update_and_free_page(page);
 261         }
 262         spin_unlock(&hugetlb_lock);
 263         return nr_huge_pages;
 264 }
 265
 266 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 267                            struct file *file, void __user *buffer,
 268                            size_t *length, loff_t *ppos)
 269 {
 270         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 271         max_huge_pages = set_max_huge_pages(max_huge_pages);
 272         return 0;
 273 }
 274
 275 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 276                         struct file *file, void __user *buffer,
 277                         size_t *length, loff_t *ppos)
 278 {
 279         proc_dointvec(table, write, file, buffer, length, ppos);
 280         if (hugepages_treat_as_movable)
 281                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
 282         else
 283                 htlb_alloc_mask = GFP_HIGHUSER;
 284         return 0;
 285 }
 286
 287 #endif /* CONFIG_SYSCTL */
 288
 289 int hugetlb_report_meminfo(char *buf)
 290 {
 291         return sprintf(buf,
 292                         "HugePages_Total: %5lu\n"
 293                         "HugePages_Free:  %5lu\n"
 294                         "HugePages_Rsvd:  %5lu\n"
 295                         "Hugepagesize:    %5lu kB\n",
 296                         nr_huge_pages,
 297                         free_huge_pages,
 298                         resv_huge_pages,
 299                         HPAGE_SIZE/1024);
 300 }
 301
 302 int hugetlb_report_node_meminfo(int nid, char *buf)
 303 {
 304         return sprintf(buf,
 305                 "Node %d HugePages_Total: %5u\n"
 306                 "Node %d HugePages_Free:  %5u\n",
 307                 nid, nr_huge_pages_node[nid],
 308                 nid, free_huge_pages_node[nid]);
 309 }
 310
 311 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 312 unsigned long hugetlb_total_pages(void)
 313 {
 314         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 315 }
 316
 317 /*
 318  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 319  * handle_mm_fault() to try to instantiate regular-sized pages in the
 320  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 321  * this far.
 322  */
 323 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 324 {
 325         BUG();
 326         return 0;
 327 }
 328
 329 struct vm_operations_struct hugetlb_vm_ops = {
 330         .fault = hugetlb_vm_op_fault,
 331 };
 332
 333 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 334                                 int writable)
 335 {
 336         pte_t entry;
 337
 338         if (writable) {
 339                 entry =
 340                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 341         } else {
 342                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 343         }
 344         entry = pte_mkyoung(entry);
 345         entry = pte_mkhuge(entry);
 346
 347         return entry;
 348 }
 349
 350 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 351                                    unsigned long address, pte_t *ptep)
 352 {
 353         pte_t entry;
 354
 355         entry = pte_mkwrite(pte_mkdirty(*ptep));
 356         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
 357                 update_mmu_cache(vma, address, entry);
 358         }
 359 }
 360
 361
 362 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 363                             struct vm_area_struct *vma)
 364 {
 365         pte_t *src_pte, *dst_pte, entry;
 366         struct page *ptepage;
 367         unsigned long addr;
 368         int cow;
 369
 370         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 371
 372         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 373                 src_pte = huge_pte_offset(src, addr);
 374                 if (!src_pte)
 375                         continue;
 376                 dst_pte = huge_pte_alloc(dst, addr);
 377                 if (!dst_pte)
 378                         goto nomem;
 379                 spin_lock(&dst->page_table_lock);
 380                 spin_lock(&src->page_table_lock);
 381                 if (!pte_none(*src_pte)) {
 382                         if (cow)
 383                                 ptep_set_wrprotect(src, addr, src_pte);
 384                         entry = *src_pte;
 385                         ptepage = pte_page(entry);
 386                         get_page(ptepage);
 387                         set_huge_pte_at(dst, addr, dst_pte, entry);
 388                 }
 389                 spin_unlock(&src->page_table_lock);
 390                 spin_unlock(&dst->page_table_lock);
 391         }
 392         return 0;
 393
 394 nomem:
 395         return -ENOMEM;
 396 }
 397
 398 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 399                             unsigned long end)
 400 {
 401         struct mm_struct *mm = vma->vm_mm;
 402         unsigned long address;
 403         pte_t *ptep;
 404         pte_t pte;
 405         struct page *page;
 406         struct page *tmp;
 407         /*
 408          * A page gathering list, protected by per file i_mmap_lock. The
 409          * lock is used to avoid list corruption from multiple unmapping
 410          * of the same page since we are using page->lru.
 411          */
 412         LIST_HEAD(page_list);
 413
 414         WARN_ON(!is_vm_hugetlb_page(vma));
 415         BUG_ON(start & ~HPAGE_MASK);
 416         BUG_ON(end & ~HPAGE_MASK);
 417
 418         spin_lock(&mm->page_table_lock);
 419         for (address = start; address < end; address += HPAGE_SIZE) {
 420                 ptep = huge_pte_offset(mm, address);
 421                 if (!ptep)
 422                         continue;
 423
 424                 if (huge_pmd_unshare(mm, &address, ptep))
 425                         continue;
 426
 427                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 428                 if (pte_none(pte))
 429                         continue;
 430
 431                 page = pte_page(pte);
 432                 if (pte_dirty(pte))
 433                         set_page_dirty(page);
 434                 list_add(&page->lru, &page_list);
 435         }
 436         spin_unlock(&mm->page_table_lock);
 437         flush_tlb_range(vma, start, end);
 438         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 439                 list_del(&page->lru);
 440                 put_page(page);
 441         }
 442 }
 443
 444 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 445                           unsigned long end)
 446 {
 447         /*
 448          * It is undesirable to test vma->vm_file as it should be non-null
 449          * for valid hugetlb area. However, vm_file will be NULL in the error
 450          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 451          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 452          * to clean up. Since no pte has actually been setup, it is safe to
 453          * do nothing in this case.
 454          */
 455         if (vma->vm_file) {
 456                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 457                 __unmap_hugepage_range(vma, start, end);
 458                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 459         }
 460 }
 461
 462 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 463                         unsigned long address, pte_t *ptep, pte_t pte)
 464 {
 465         struct page *old_page, *new_page;
 466         int avoidcopy;
 467
 468         old_page = pte_page(pte);
 469
 470         /* If no-one else is actually using this page, avoid the copy
 471          * and just make the page writable */
 472         avoidcopy = (page_count(old_page) == 1);
 473         if (avoidcopy) {
 474                 set_huge_ptep_writable(vma, address, ptep);
 475                 return 0;
 476         }
 477
 478         page_cache_get(old_page);
 479         new_page = alloc_huge_page(vma, address);
 480
 481         if (!new_page) {
 482                 page_cache_release(old_page);
 483                 return VM_FAULT_OOM;
 484         }
 485
 486         spin_unlock(&mm->page_table_lock);
 487         copy_huge_page(new_page, old_page, address, vma);
 488         spin_lock(&mm->page_table_lock);
 489
 490         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 491         if (likely(pte_same(*ptep, pte))) {
 492                 /* Break COW */
 493                 set_huge_pte_at(mm, address, ptep,
 494                                 make_huge_pte(vma, new_page, 1));
 495                 /* Make the old page be freed below */
 496                 new_page = old_page;
 497         }
 498         page_cache_release(new_page);
 499         page_cache_release(old_page);
 500         return 0;
 501 }
 502
 503 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 504                         unsigned long address, pte_t *ptep, int write_access)
 505 {
 506         int ret = VM_FAULT_SIGBUS;
 507         unsigned long idx;
 508         unsigned long size;
 509         struct page *page;
 510         struct address_space *mapping;
 511         pte_t new_pte;
 512
 513         mapping = vma->vm_file->f_mapping;
 514         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 515                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 516
 517         /*
 518          * Use page lock to guard against racing truncation
 519          * before we get page_table_lock.
 520          */
 521 retry:
 522         page = find_lock_page(mapping, idx);
 523         if (!page) {
 524                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 525                 if (idx >= size)
 526                         goto out;
 527                 if (hugetlb_get_quota(mapping))
 528                         goto out;
 529                 page = alloc_huge_page(vma, address);
 530                 if (!page) {
 531                         hugetlb_put_quota(mapping);
 532                         ret = VM_FAULT_OOM;
 533                         goto out;
 534                 }
 535                 clear_huge_page(page, address);
 536
 537                 if (vma->vm_flags & VM_SHARED) {
 538                         int err;
 539
 540                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 541                         if (err) {
 542                                 put_page(page);
 543                                 hugetlb_put_quota(mapping);
 544                                 if (err == -EEXIST)
 545                                         goto retry;
 546                                 goto out;
 547                         }
 548                 } else
 549                         lock_page(page);
 550         }
 551
 552         spin_lock(&mm->page_table_lock);
 553         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 554         if (idx >= size)
 555                 goto backout;
 556
 557         ret = 0;
 558         if (!pte_none(*ptep))
 559                 goto backout;
 560
 561         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 562                                 && (vma->vm_flags & VM_SHARED)));
 563         set_huge_pte_at(mm, address, ptep, new_pte);
 564
 565         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 566                 /* Optimization, do the COW without a second fault */
 567                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 568         }
 569
 570         spin_unlock(&mm->page_table_lock);
 571         unlock_page(page);
 572 out:
 573         return ret;
 574
 575 backout:
 576         spin_unlock(&mm->page_table_lock);
 577         hugetlb_put_quota(mapping);
 578         unlock_page(page);
 579         put_page(page);
 580         goto out;
 581 }
 582
 583 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 584                         unsigned long address, int write_access)
 585 {
 586         pte_t *ptep;
 587         pte_t entry;
 588         int ret;
 589         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 590
 591         ptep = huge_pte_alloc(mm, address);
 592         if (!ptep)
 593                 return VM_FAULT_OOM;
 594
 595         /*
 596          * Serialize hugepage allocation and instantiation, so that we don't
 597          * get spurious allocation failures if two CPUs race to instantiate
 598          * the same page in the page cache.
 599          */
 600         mutex_lock(&hugetlb_instantiation_mutex);
 601         entry = *ptep;
 602         if (pte_none(entry)) {
 603                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 604                 mutex_unlock(&hugetlb_instantiation_mutex);
 605                 return ret;
 606         }
 607
 608         ret = 0;
 609
 610         spin_lock(&mm->page_table_lock);
 611         /* Check for a racing update before calling hugetlb_cow */
 612         if (likely(pte_same(entry, *ptep)))
 613                 if (write_access && !pte_write(entry))
 614                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 615         spin_unlock(&mm->page_table_lock);
 616         mutex_unlock(&hugetlb_instantiation_mutex);
 617
 618         return ret;
 619 }
 620
 621 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 622                         struct page **pages, struct vm_area_struct **vmas,
 623                         unsigned long *position, int *length, int i)
 624 {
 625         unsigned long pfn_offset;
 626         unsigned long vaddr = *position;
 627         int remainder = *length;
 628
 629         spin_lock(&mm->page_table_lock);
 630         while (vaddr < vma->vm_end && remainder) {
 631                 pte_t *pte;
 632                 struct page *page;
 633
 634                 /*
 635                  * Some archs (sparc64, sh*) have multiple pte_ts to
 636                  * each hugepage.  We have to make * sure we get the
 637                  * first, for the page indexing below to work.
 638                  */
 639                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 640
 641                 if (!pte || pte_none(*pte)) {
 642                         int ret;
 643
 644                         spin_unlock(&mm->page_table_lock);
 645                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 646                         spin_lock(&mm->page_table_lock);
 647                         if (!(ret & VM_FAULT_ERROR))
 648                                 continue;
 649
 650                         remainder = 0;
 651                         if (!i)
 652                                 i = -EFAULT;
 653                         break;
 654                 }
 655
 656                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 657                 page = pte_page(*pte);
 658 same_page:
 659                 if (pages) {
 660                         get_page(page);
 661                         pages[i] = page + pfn_offset;
 662                 }
 663
 664                 if (vmas)
 665                         vmas[i] = vma;
 666
 667                 vaddr += PAGE_SIZE;
 668                 ++pfn_offset;
 669                 --remainder;
 670                 ++i;
 671                 if (vaddr < vma->vm_end && remainder &&
 672                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 673                         /*
 674                          * We use pfn_offset to avoid touching the pageframes
 675                          * of this compound page.
 676                          */
 677                         goto same_page;
 678                 }
 679         }
 680         spin_unlock(&mm->page_table_lock);
 681         *length = remainder;
 682         *position = vaddr;
 683
 684         return i;
 685 }
 686
 687 void hugetlb_change_protection(struct vm_area_struct *vma,
 688                 unsigned long address, unsigned long end, pgprot_t newprot)
 689 {
 690         struct mm_struct *mm = vma->vm_mm;
 691         unsigned long start = address;
 692         pte_t *ptep;
 693         pte_t pte;
 694
 695         BUG_ON(address >= end);
 696         flush_cache_range(vma, address, end);
 697
 698         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 699         spin_lock(&mm->page_table_lock);
 700         for (; address < end; address += HPAGE_SIZE) {
 701                 ptep = huge_pte_offset(mm, address);
 702                 if (!ptep)
 703                         continue;
 704                 if (huge_pmd_unshare(mm, &address, ptep))
 705                         continue;
 706                 if (!pte_none(*ptep)) {
 707                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 708                         pte = pte_mkhuge(pte_modify(pte, newprot));
 709                         set_huge_pte_at(mm, address, ptep, pte);
 710                 }
 711         }
 712         spin_unlock(&mm->page_table_lock);
 713         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 714
 715         flush_tlb_range(vma, start, end);
 716 }
 717
 718 struct file_region {
 719         struct list_head link;
 720         long from;
 721         long to;
 722 };
 723
 724 static long region_add(struct list_head *head, long f, long t)
 725 {
 726         struct file_region *rg, *nrg, *trg;
 727
 728         /* Locate the region we are either in or before. */
 729         list_for_each_entry(rg, head, link)
 730                 if (f <= rg->to)
 731                         break;
 732
 733         /* Round our left edge to the current segment if it encloses us. */
 734         if (f > rg->from)
 735                 f = rg->from;
 736
 737         /* Check for and consume any regions we now overlap with. */
 738         nrg = rg;
 739         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 740                 if (&rg->link == head)
 741                         break;
 742                 if (rg->from > t)
 743                         break;
 744
 745                 /* If this area reaches higher then extend our area to
 746                  * include it completely.  If this is not the first area
 747                  * which we intend to reuse, free it. */
 748                 if (rg->to > t)
 749                         t = rg->to;
 750                 if (rg != nrg) {
 751                         list_del(&rg->link);
 752                         kfree(rg);
 753                 }
 754         }
 755         nrg->from = f;
 756         nrg->to = t;
 757         return 0;
 758 }
 759
 760 static long region_chg(struct list_head *head, long f, long t)
 761 {
 762         struct file_region *rg, *nrg;
 763         long chg = 0;
 764
 765         /* Locate the region we are before or in. */
 766         list_for_each_entry(rg, head, link)
 767                 if (f <= rg->to)
 768                         break;
 769
 770         /* If we are below the current region then a new region is required.
 771          * Subtle, allocate a new region at the position but make it zero
 772          * size such that we can guarentee to record the reservation. */
 773         if (&rg->link == head || t < rg->from) {
 774                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
 775                 if (nrg == 0)
 776                         return -ENOMEM;
 777                 nrg->from = f;
 778                 nrg->to   = f;
 779                 INIT_LIST_HEAD(&nrg->link);
 780                 list_add(&nrg->link, rg->link.prev);
 781
 782                 return t - f;
 783         }
 784
 785         /* Round our left edge to the current segment if it encloses us. */
 786         if (f > rg->from)
 787                 f = rg->from;
 788         chg = t - f;
 789
 790         /* Check for and consume any regions we now overlap with. */
 791         list_for_each_entry(rg, rg->link.prev, link) {
 792                 if (&rg->link == head)
 793                         break;
 794                 if (rg->from > t)
 795                         return chg;
 796
 797                 /* We overlap with this area, if it extends futher than
 798                  * us then we must extend ourselves.  Account for its
 799                  * existing reservation. */
 800                 if (rg->to > t) {
 801                         chg += rg->to - t;
 802                         t = rg->to;
 803                 }
 804                 chg -= rg->to - rg->from;
 805         }
 806         return chg;
 807 }
 808
 809 static long region_truncate(struct list_head *head, long end)
 810 {
 811         struct file_region *rg, *trg;
 812         long chg = 0;
 813
 814         /* Locate the region we are either in or before. */
 815         list_for_each_entry(rg, head, link)
 816                 if (end <= rg->to)
 817                         break;
 818         if (&rg->link == head)
 819                 return 0;
 820
 821         /* If we are in the middle of a region then adjust it. */
 822         if (end > rg->from) {
 823                 chg = rg->to - end;
 824                 rg->to = end;
 825                 rg = list_entry(rg->link.next, typeof(*rg), link);
 826         }
 827
 828         /* Drop any remaining regions. */
 829         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 830                 if (&rg->link == head)
 831                         break;
 832                 chg += rg->to - rg->from;
 833                 list_del(&rg->link);
 834                 kfree(rg);
 835         }
 836         return chg;
 837 }
 838
 839 static int hugetlb_acct_memory(long delta)
 840 {
 841         int ret = -ENOMEM;
 842
 843         spin_lock(&hugetlb_lock);
 844         if ((delta + resv_huge_pages) <= free_huge_pages) {
 845                 resv_huge_pages += delta;
 846                 ret = 0;
 847         }
 848         spin_unlock(&hugetlb_lock);
 849         return ret;
 850 }
 851
 852 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
 853 {
 854         long ret, chg;
 855
 856         chg = region_chg(&inode->i_mapping->private_list, from, to);
 857         if (chg < 0)
 858                 return chg;
 859         /*
 860          * When cpuset is configured, it breaks the strict hugetlb page
 861          * reservation as the accounting is done on a global variable. Such
 862          * reservation is completely rubbish in the presence of cpuset because
 863          * the reservation is not checked against page availability for the
 864          * current cpuset. Application can still potentially OOM'ed by kernel
 865          * with lack of free htlb page in cpuset that the task is in.
 866          * Attempt to enforce strict accounting with cpuset is almost
 867          * impossible (or too ugly) because cpuset is too fluid that
 868          * task or memory node can be dynamically moved between cpusets.
 869          *
 870          * The change of semantics for shared hugetlb mapping with cpuset is
 871          * undesirable. However, in order to preserve some of the semantics,
 872          * we fall back to check against current free page availability as
 873          * a best attempt and hopefully to minimize the impact of changing
 874          * semantics that cpuset has.
 875          */
 876         if (chg > cpuset_mems_nr(free_huge_pages_node))
 877                 return -ENOMEM;
 878
 879         ret = hugetlb_acct_memory(chg);
 880         if (ret < 0)
 881                 return ret;
 882         region_add(&inode->i_mapping->private_list, from, to);
 883         return 0;
 884 }
 885
 886 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 887 {
 888         long chg = region_truncate(&inode->i_mapping->private_list, offset);
 889         hugetlb_acct_memory(freed - chg);
 890 }