mm/hugetlb.c

   1 /*
   2  * Generic hugetlb support.
   3  * (C) William Irwin, April 2004
   4  */
   5 #include <linux/gfp.h>
   6 #include <linux/list.h>
   7 #include <linux/init.h>
   8 #include <linux/module.h>
   9 #include <linux/mm.h>
  10 #include <linux/sysctl.h>
  11 #include <linux/highmem.h>
  12 #include <linux/nodemask.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/mempolicy.h>
  15 #include <linux/cpuset.h>
  16 #include <linux/mutex.h>
  17
  18 #include <asm/page.h>
  19 #include <asm/pgtable.h>
  20
  21 #include <linux/hugetlb.h>
  22 #include "internal.h"
  23
  24 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  25 static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
  26 unsigned long max_huge_pages;
  27 static struct list_head hugepage_freelists[MAX_NUMNODES];
  28 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  29 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  30 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
  31 unsigned long hugepages_treat_as_movable;
  32
  33 /*
  34  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  35  */
  36 static DEFINE_SPINLOCK(hugetlb_lock);
  37
  38 static void clear_huge_page(struct page *page, unsigned long addr)
  39 {
  40         int i;
  41
  42         might_sleep();
  43         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  44                 cond_resched();
  45                 clear_user_highpage(page + i, addr);
  46         }
  47 }
  48
  49 static void copy_huge_page(struct page *dst, struct page *src,
  50                            unsigned long addr, struct vm_area_struct *vma)
  51 {
  52         int i;
  53
  54         might_sleep();
  55         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  56                 cond_resched();
  57                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
  58         }
  59 }
  60
  61 static void enqueue_huge_page(struct page *page)
  62 {
  63         int nid = page_to_nid(page);
  64         list_add(&page->lru, &hugepage_freelists[nid]);
  65         free_huge_pages++;
  66         free_huge_pages_node[nid]++;
  67 }
  68
  69 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  70                                 unsigned long address)
  71 {
  72         int nid;
  73         struct page *page = NULL;
  74         struct zonelist *zonelist = huge_zonelist(vma, address,
  75                                                 htlb_alloc_mask);
  76         struct zone **z;
  77
  78         for (z = zonelist->zones; *z; z++) {
  79                 nid = zone_to_nid(*z);
  80                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
  81                     !list_empty(&hugepage_freelists[nid])) {
  82                         page = list_entry(hugepage_freelists[nid].next,
  83                                           struct page, lru);
  84                         list_del(&page->lru);
  85                         free_huge_pages--;
  86                         free_huge_pages_node[nid]--;
  87                 }
  88         }
  89         return page;
  90 }
  91
  92 static void free_huge_page(struct page *page)
  93 {
  94         BUG_ON(page_count(page));
  95
  96         INIT_LIST_HEAD(&page->lru);
  97
  98         spin_lock(&hugetlb_lock);
  99         enqueue_huge_page(page);
 100         spin_unlock(&hugetlb_lock);
 101 }
 102
 103 static int alloc_fresh_huge_page(void)
 104 {
 105         static int prev_nid;
 106         struct page *page;
 107         int nid;
 108
 109         /*
 110          * Copy static prev_nid to local nid, work on that, then copy it
 111          * back to prev_nid afterwards: otherwise there's a window in which
 112          * a racer might pass invalid nid MAX_NUMNODES to alloc_pages_node.
 113          * But we don't need to use a spin_lock here: it really doesn't
 114          * matter if occasionally a racer chooses the same nid as we do.
 115          */
 116         nid = next_node(prev_nid, node_online_map);
 117         if (nid == MAX_NUMNODES)
 118                 nid = first_node(node_online_map);
 119         prev_nid = nid;
 120
 121         page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 122                                         HUGETLB_PAGE_ORDER);
 123         if (page) {
 124                 set_compound_page_dtor(page, free_huge_page);
 125                 spin_lock(&hugetlb_lock);
 126                 nr_huge_pages++;
 127                 nr_huge_pages_node[page_to_nid(page)]++;
 128                 spin_unlock(&hugetlb_lock);
 129                 put_page(page); /* free it into the hugepage allocator */
 130                 return 1;
 131         }
 132         return 0;
 133 }
 134
 135 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 136                                     unsigned long addr)
 137 {
 138         struct page *page;
 139
 140         spin_lock(&hugetlb_lock);
 141         if (vma->vm_flags & VM_MAYSHARE)
 142                 resv_huge_pages--;
 143         else if (free_huge_pages <= resv_huge_pages)
 144                 goto fail;
 145
 146         page = dequeue_huge_page(vma, addr);
 147         if (!page)
 148                 goto fail;
 149
 150         spin_unlock(&hugetlb_lock);
 151         set_page_refcounted(page);
 152         return page;
 153
 154 fail:
 155         if (vma->vm_flags & VM_MAYSHARE)
 156                 resv_huge_pages++;
 157         spin_unlock(&hugetlb_lock);
 158         return NULL;
 159 }
 160
 161 static int __init hugetlb_init(void)
 162 {
 163         unsigned long i;
 164
 165         if (HPAGE_SHIFT == 0)
 166                 return 0;
 167
 168         for (i = 0; i < MAX_NUMNODES; ++i)
 169                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 170
 171         for (i = 0; i < max_huge_pages; ++i) {
 172                 if (!alloc_fresh_huge_page())
 173                         break;
 174         }
 175         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 176         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 177         return 0;
 178 }
 179 module_init(hugetlb_init);
 180
 181 static int __init hugetlb_setup(char *s)
 182 {
 183         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 184                 max_huge_pages = 0;
 185         return 1;
 186 }
 187 __setup("hugepages=", hugetlb_setup);
 188
 189 static unsigned int cpuset_mems_nr(unsigned int *array)
 190 {
 191         int node;
 192         unsigned int nr = 0;
 193
 194         for_each_node_mask(node, cpuset_current_mems_allowed)
 195                 nr += array[node];
 196
 197         return nr;
 198 }
 199
 200 #ifdef CONFIG_SYSCTL
 201 static void update_and_free_page(struct page *page)
 202 {
 203         int i;
 204         nr_huge_pages--;
 205         nr_huge_pages_node[page_to_nid(page)]--;
 206         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 207                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 208                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 209                                 1 << PG_private | 1<< PG_writeback);
 210         }
 211         set_compound_page_dtor(page, NULL);
 212         set_page_refcounted(page);
 213         __free_pages(page, HUGETLB_PAGE_ORDER);
 214 }
 215
 216 #ifdef CONFIG_HIGHMEM
 217 static void try_to_free_low(unsigned long count)
 218 {
 219         int i;
 220
 221         for (i = 0; i < MAX_NUMNODES; ++i) {
 222                 struct page *page, *next;
 223                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 224                         if (PageHighMem(page))
 225                                 continue;
 226                         list_del(&page->lru);
 227                         update_and_free_page(page);
 228                         free_huge_pages--;
 229                         free_huge_pages_node[page_to_nid(page)]--;
 230                         if (count >= nr_huge_pages)
 231                                 return;
 232                 }
 233         }
 234 }
 235 #else
 236 static inline void try_to_free_low(unsigned long count)
 237 {
 238 }
 239 #endif
 240
 241 static unsigned long set_max_huge_pages(unsigned long count)
 242 {
 243         while (count > nr_huge_pages) {
 244                 if (!alloc_fresh_huge_page())
 245                         return nr_huge_pages;
 246         }
 247         if (count >= nr_huge_pages)
 248                 return nr_huge_pages;
 249
 250         spin_lock(&hugetlb_lock);
 251         count = max(count, resv_huge_pages);
 252         try_to_free_low(count);
 253         while (count < nr_huge_pages) {
 254                 struct page *page = dequeue_huge_page(NULL, 0);
 255                 if (!page)
 256                         break;
 257                 update_and_free_page(page);
 258         }
 259         spin_unlock(&hugetlb_lock);
 260         return nr_huge_pages;
 261 }
 262
 263 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 264                            struct file *file, void __user *buffer,
 265                            size_t *length, loff_t *ppos)
 266 {
 267         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 268         max_huge_pages = set_max_huge_pages(max_huge_pages);
 269         return 0;
 270 }
 271
 272 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 273                         struct file *file, void __user *buffer,
 274                         size_t *length, loff_t *ppos)
 275 {
 276         proc_dointvec(table, write, file, buffer, length, ppos);
 277         if (hugepages_treat_as_movable)
 278                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
 279         else
 280                 htlb_alloc_mask = GFP_HIGHUSER;
 281         return 0;
 282 }
 283
 284 #endif /* CONFIG_SYSCTL */
 285
 286 int hugetlb_report_meminfo(char *buf)
 287 {
 288         return sprintf(buf,
 289                         "HugePages_Total: %5lu\n"
 290                         "HugePages_Free:  %5lu\n"
 291                         "HugePages_Rsvd:  %5lu\n"
 292                         "Hugepagesize:    %5lu kB\n",
 293                         nr_huge_pages,
 294                         free_huge_pages,
 295                         resv_huge_pages,
 296                         HPAGE_SIZE/1024);
 297 }
 298
 299 int hugetlb_report_node_meminfo(int nid, char *buf)
 300 {
 301         return sprintf(buf,
 302                 "Node %d HugePages_Total: %5u\n"
 303                 "Node %d HugePages_Free:  %5u\n",
 304                 nid, nr_huge_pages_node[nid],
 305                 nid, free_huge_pages_node[nid]);
 306 }
 307
 308 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 309 unsigned long hugetlb_total_pages(void)
 310 {
 311         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 312 }
 313
 314 /*
 315  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 316  * handle_mm_fault() to try to instantiate regular-sized pages in the
 317  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 318  * this far.
 319  */
 320 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 321 {
 322         BUG();
 323         return 0;
 324 }
 325
 326 struct vm_operations_struct hugetlb_vm_ops = {
 327         .fault = hugetlb_vm_op_fault,
 328 };
 329
 330 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 331                                 int writable)
 332 {
 333         pte_t entry;
 334
 335         if (writable) {
 336                 entry =
 337                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 338         } else {
 339                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 340         }
 341         entry = pte_mkyoung(entry);
 342         entry = pte_mkhuge(entry);
 343
 344         return entry;
 345 }
 346
 347 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 348                                    unsigned long address, pte_t *ptep)
 349 {
 350         pte_t entry;
 351
 352         entry = pte_mkwrite(pte_mkdirty(*ptep));
 353         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
 354                 update_mmu_cache(vma, address, entry);
 355                 lazy_mmu_prot_update(entry);
 356         }
 357 }
 358
 359
 360 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 361                             struct vm_area_struct *vma)
 362 {
 363         pte_t *src_pte, *dst_pte, entry;
 364         struct page *ptepage;
 365         unsigned long addr;
 366         int cow;
 367
 368         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 369
 370         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 371                 src_pte = huge_pte_offset(src, addr);
 372                 if (!src_pte)
 373                         continue;
 374                 dst_pte = huge_pte_alloc(dst, addr);
 375                 if (!dst_pte)
 376                         goto nomem;
 377                 spin_lock(&dst->page_table_lock);
 378                 spin_lock(&src->page_table_lock);
 379                 if (!pte_none(*src_pte)) {
 380                         if (cow)
 381                                 ptep_set_wrprotect(src, addr, src_pte);
 382                         entry = *src_pte;
 383                         ptepage = pte_page(entry);
 384                         get_page(ptepage);
 385                         set_huge_pte_at(dst, addr, dst_pte, entry);
 386                 }
 387                 spin_unlock(&src->page_table_lock);
 388                 spin_unlock(&dst->page_table_lock);
 389         }
 390         return 0;
 391
 392 nomem:
 393         return -ENOMEM;
 394 }
 395
 396 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 397                             unsigned long end)
 398 {
 399         struct mm_struct *mm = vma->vm_mm;
 400         unsigned long address;
 401         pte_t *ptep;
 402         pte_t pte;
 403         struct page *page;
 404         struct page *tmp;
 405         /*
 406          * A page gathering list, protected by per file i_mmap_lock. The
 407          * lock is used to avoid list corruption from multiple unmapping
 408          * of the same page since we are using page->lru.
 409          */
 410         LIST_HEAD(page_list);
 411
 412         WARN_ON(!is_vm_hugetlb_page(vma));
 413         BUG_ON(start & ~HPAGE_MASK);
 414         BUG_ON(end & ~HPAGE_MASK);
 415
 416         spin_lock(&mm->page_table_lock);
 417         for (address = start; address < end; address += HPAGE_SIZE) {
 418                 ptep = huge_pte_offset(mm, address);
 419                 if (!ptep)
 420                         continue;
 421
 422                 if (huge_pmd_unshare(mm, &address, ptep))
 423                         continue;
 424
 425                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 426                 if (pte_none(pte))
 427                         continue;
 428
 429                 page = pte_page(pte);
 430                 if (pte_dirty(pte))
 431                         set_page_dirty(page);
 432                 list_add(&page->lru, &page_list);
 433         }
 434         spin_unlock(&mm->page_table_lock);
 435         flush_tlb_range(vma, start, end);
 436         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 437                 list_del(&page->lru);
 438                 put_page(page);
 439         }
 440 }
 441
 442 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 443                           unsigned long end)
 444 {
 445         /*
 446          * It is undesirable to test vma->vm_file as it should be non-null
 447          * for valid hugetlb area. However, vm_file will be NULL in the error
 448          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 449          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 450          * to clean up. Since no pte has actually been setup, it is safe to
 451          * do nothing in this case.
 452          */
 453         if (vma->vm_file) {
 454                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 455                 __unmap_hugepage_range(vma, start, end);
 456                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 457         }
 458 }
 459
 460 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 461                         unsigned long address, pte_t *ptep, pte_t pte)
 462 {
 463         struct page *old_page, *new_page;
 464         int avoidcopy;
 465
 466         old_page = pte_page(pte);
 467
 468         /* If no-one else is actually using this page, avoid the copy
 469          * and just make the page writable */
 470         avoidcopy = (page_count(old_page) == 1);
 471         if (avoidcopy) {
 472                 set_huge_ptep_writable(vma, address, ptep);
 473                 return 0;
 474         }
 475
 476         page_cache_get(old_page);
 477         new_page = alloc_huge_page(vma, address);
 478
 479         if (!new_page) {
 480                 page_cache_release(old_page);
 481                 return VM_FAULT_OOM;
 482         }
 483
 484         spin_unlock(&mm->page_table_lock);
 485         copy_huge_page(new_page, old_page, address, vma);
 486         spin_lock(&mm->page_table_lock);
 487
 488         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 489         if (likely(pte_same(*ptep, pte))) {
 490                 /* Break COW */
 491                 set_huge_pte_at(mm, address, ptep,
 492                                 make_huge_pte(vma, new_page, 1));
 493                 /* Make the old page be freed below */
 494                 new_page = old_page;
 495         }
 496         page_cache_release(new_page);
 497         page_cache_release(old_page);
 498         return 0;
 499 }
 500
 501 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 502                         unsigned long address, pte_t *ptep, int write_access)
 503 {
 504         int ret = VM_FAULT_SIGBUS;
 505         unsigned long idx;
 506         unsigned long size;
 507         struct page *page;
 508         struct address_space *mapping;
 509         pte_t new_pte;
 510
 511         mapping = vma->vm_file->f_mapping;
 512         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 513                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 514
 515         /*
 516          * Use page lock to guard against racing truncation
 517          * before we get page_table_lock.
 518          */
 519 retry:
 520         page = find_lock_page(mapping, idx);
 521         if (!page) {
 522                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 523                 if (idx >= size)
 524                         goto out;
 525                 if (hugetlb_get_quota(mapping))
 526                         goto out;
 527                 page = alloc_huge_page(vma, address);
 528                 if (!page) {
 529                         hugetlb_put_quota(mapping);
 530                         ret = VM_FAULT_OOM;
 531                         goto out;
 532                 }
 533                 clear_huge_page(page, address);
 534
 535                 if (vma->vm_flags & VM_SHARED) {
 536                         int err;
 537
 538                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 539                         if (err) {
 540                                 put_page(page);
 541                                 hugetlb_put_quota(mapping);
 542                                 if (err == -EEXIST)
 543                                         goto retry;
 544                                 goto out;
 545                         }
 546                 } else
 547                         lock_page(page);
 548         }
 549
 550         spin_lock(&mm->page_table_lock);
 551         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 552         if (idx >= size)
 553                 goto backout;
 554
 555         ret = 0;
 556         if (!pte_none(*ptep))
 557                 goto backout;
 558
 559         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 560                                 && (vma->vm_flags & VM_SHARED)));
 561         set_huge_pte_at(mm, address, ptep, new_pte);
 562
 563         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 564                 /* Optimization, do the COW without a second fault */
 565                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 566         }
 567
 568         spin_unlock(&mm->page_table_lock);
 569         unlock_page(page);
 570 out:
 571         return ret;
 572
 573 backout:
 574         spin_unlock(&mm->page_table_lock);
 575         hugetlb_put_quota(mapping);
 576         unlock_page(page);
 577         put_page(page);
 578         goto out;
 579 }
 580
 581 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 582                         unsigned long address, int write_access)
 583 {
 584         pte_t *ptep;
 585         pte_t entry;
 586         int ret;
 587         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 588
 589         ptep = huge_pte_alloc(mm, address);
 590         if (!ptep)
 591                 return VM_FAULT_OOM;
 592
 593         /*
 594          * Serialize hugepage allocation and instantiation, so that we don't
 595          * get spurious allocation failures if two CPUs race to instantiate
 596          * the same page in the page cache.
 597          */
 598         mutex_lock(&hugetlb_instantiation_mutex);
 599         entry = *ptep;
 600         if (pte_none(entry)) {
 601                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 602                 mutex_unlock(&hugetlb_instantiation_mutex);
 603                 return ret;
 604         }
 605
 606         ret = 0;
 607
 608         spin_lock(&mm->page_table_lock);
 609         /* Check for a racing update before calling hugetlb_cow */
 610         if (likely(pte_same(entry, *ptep)))
 611                 if (write_access && !pte_write(entry))
 612                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 613         spin_unlock(&mm->page_table_lock);
 614         mutex_unlock(&hugetlb_instantiation_mutex);
 615
 616         return ret;
 617 }
 618
 619 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 620                         struct page **pages, struct vm_area_struct **vmas,
 621                         unsigned long *position, int *length, int i)
 622 {
 623         unsigned long pfn_offset;
 624         unsigned long vaddr = *position;
 625         int remainder = *length;
 626
 627         spin_lock(&mm->page_table_lock);
 628         while (vaddr < vma->vm_end && remainder) {
 629                 pte_t *pte;
 630                 struct page *page;
 631
 632                 /*
 633                  * Some archs (sparc64, sh*) have multiple pte_ts to
 634                  * each hugepage.  We have to make * sure we get the
 635                  * first, for the page indexing below to work.
 636                  */
 637                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 638
 639                 if (!pte || pte_none(*pte)) {
 640                         int ret;
 641
 642                         spin_unlock(&mm->page_table_lock);
 643                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 644                         spin_lock(&mm->page_table_lock);
 645                         if (!(ret & VM_FAULT_MAJOR))
 646                                 continue;
 647
 648                         remainder = 0;
 649                         if (!i)
 650                                 i = -EFAULT;
 651                         break;
 652                 }
 653
 654                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 655                 page = pte_page(*pte);
 656 same_page:
 657                 if (pages) {
 658                         get_page(page);
 659                         pages[i] = page + pfn_offset;
 660                 }
 661
 662                 if (vmas)
 663                         vmas[i] = vma;
 664
 665                 vaddr += PAGE_SIZE;
 666                 ++pfn_offset;
 667                 --remainder;
 668                 ++i;
 669                 if (vaddr < vma->vm_end && remainder &&
 670                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 671                         /*
 672                          * We use pfn_offset to avoid touching the pageframes
 673                          * of this compound page.
 674                          */
 675                         goto same_page;
 676                 }
 677         }
 678         spin_unlock(&mm->page_table_lock);
 679         *length = remainder;
 680         *position = vaddr;
 681
 682         return i;
 683 }
 684
 685 void hugetlb_change_protection(struct vm_area_struct *vma,
 686                 unsigned long address, unsigned long end, pgprot_t newprot)
 687 {
 688         struct mm_struct *mm = vma->vm_mm;
 689         unsigned long start = address;
 690         pte_t *ptep;
 691         pte_t pte;
 692
 693         BUG_ON(address >= end);
 694         flush_cache_range(vma, address, end);
 695
 696         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 697         spin_lock(&mm->page_table_lock);
 698         for (; address < end; address += HPAGE_SIZE) {
 699                 ptep = huge_pte_offset(mm, address);
 700                 if (!ptep)
 701                         continue;
 702                 if (huge_pmd_unshare(mm, &address, ptep))
 703                         continue;
 704                 if (!pte_none(*ptep)) {
 705                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 706                         pte = pte_mkhuge(pte_modify(pte, newprot));
 707                         set_huge_pte_at(mm, address, ptep, pte);
 708                         lazy_mmu_prot_update(pte);
 709                 }
 710         }
 711         spin_unlock(&mm->page_table_lock);
 712         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 713
 714         flush_tlb_range(vma, start, end);
 715 }
 716
 717 struct file_region {
 718         struct list_head link;
 719         long from;
 720         long to;
 721 };
 722
 723 static long region_add(struct list_head *head, long f, long t)
 724 {
 725         struct file_region *rg, *nrg, *trg;
 726
 727         /* Locate the region we are either in or before. */
 728         list_for_each_entry(rg, head, link)
 729                 if (f <= rg->to)
 730                         break;
 731
 732         /* Round our left edge to the current segment if it encloses us. */
 733         if (f > rg->from)
 734                 f = rg->from;
 735
 736         /* Check for and consume any regions we now overlap with. */
 737         nrg = rg;
 738         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 739                 if (&rg->link == head)
 740                         break;
 741                 if (rg->from > t)
 742                         break;
 743
 744                 /* If this area reaches higher then extend our area to
 745                  * include it completely.  If this is not the first area
 746                  * which we intend to reuse, free it. */
 747                 if (rg->to > t)
 748                         t = rg->to;
 749                 if (rg != nrg) {
 750                         list_del(&rg->link);
 751                         kfree(rg);
 752                 }
 753         }
 754         nrg->from = f;
 755         nrg->to = t;
 756         return 0;
 757 }
 758
 759 static long region_chg(struct list_head *head, long f, long t)
 760 {
 761         struct file_region *rg, *nrg;
 762         long chg = 0;
 763
 764         /* Locate the region we are before or in. */
 765         list_for_each_entry(rg, head, link)
 766                 if (f <= rg->to)
 767                         break;
 768
 769         /* If we are below the current region then a new region is required.
 770          * Subtle, allocate a new region at the position but make it zero
 771          * size such that we can guarentee to record the reservation. */
 772         if (&rg->link == head || t < rg->from) {
 773                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
 774                 if (nrg == 0)
 775                         return -ENOMEM;
 776                 nrg->from = f;
 777                 nrg->to   = f;
 778                 INIT_LIST_HEAD(&nrg->link);
 779                 list_add(&nrg->link, rg->link.prev);
 780
 781                 return t - f;
 782         }
 783
 784         /* Round our left edge to the current segment if it encloses us. */
 785         if (f > rg->from)
 786                 f = rg->from;
 787         chg = t - f;
 788
 789         /* Check for and consume any regions we now overlap with. */
 790         list_for_each_entry(rg, rg->link.prev, link) {
 791                 if (&rg->link == head)
 792                         break;
 793                 if (rg->from > t)
 794                         return chg;
 795
 796                 /* We overlap with this area, if it extends futher than
 797                  * us then we must extend ourselves.  Account for its
 798                  * existing reservation. */
 799                 if (rg->to > t) {
 800                         chg += rg->to - t;
 801                         t = rg->to;
 802                 }
 803                 chg -= rg->to - rg->from;
 804         }
 805         return chg;
 806 }
 807
 808 static long region_truncate(struct list_head *head, long end)
 809 {
 810         struct file_region *rg, *trg;
 811         long chg = 0;
 812
 813         /* Locate the region we are either in or before. */
 814         list_for_each_entry(rg, head, link)
 815                 if (end <= rg->to)
 816                         break;
 817         if (&rg->link == head)
 818                 return 0;
 819
 820         /* If we are in the middle of a region then adjust it. */
 821         if (end > rg->from) {
 822                 chg = rg->to - end;
 823                 rg->to = end;
 824                 rg = list_entry(rg->link.next, typeof(*rg), link);
 825         }
 826
 827         /* Drop any remaining regions. */
 828         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
 829                 if (&rg->link == head)
 830                         break;
 831                 chg += rg->to - rg->from;
 832                 list_del(&rg->link);
 833                 kfree(rg);
 834         }
 835         return chg;
 836 }
 837
 838 static int hugetlb_acct_memory(long delta)
 839 {
 840         int ret = -ENOMEM;
 841
 842         spin_lock(&hugetlb_lock);
 843         if ((delta + resv_huge_pages) <= free_huge_pages) {
 844                 resv_huge_pages += delta;
 845                 ret = 0;
 846         }
 847         spin_unlock(&hugetlb_lock);
 848         return ret;
 849 }
 850
 851 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
 852 {
 853         long ret, chg;
 854
 855         chg = region_chg(&inode->i_mapping->private_list, from, to);
 856         if (chg < 0)
 857                 return chg;
 858         /*
 859          * When cpuset is configured, it breaks the strict hugetlb page
 860          * reservation as the accounting is done on a global variable. Such
 861          * reservation is completely rubbish in the presence of cpuset because
 862          * the reservation is not checked against page availability for the
 863          * current cpuset. Application can still potentially OOM'ed by kernel
 864          * with lack of free htlb page in cpuset that the task is in.
 865          * Attempt to enforce strict accounting with cpuset is almost
 866          * impossible (or too ugly) because cpuset is too fluid that
 867          * task or memory node can be dynamically moved between cpusets.
 868          *
 869          * The change of semantics for shared hugetlb mapping with cpuset is
 870          * undesirable. However, in order to preserve some of the semantics,
 871          * we fall back to check against current free page availability as
 872          * a best attempt and hopefully to minimize the impact of changing
 873          * semantics that cpuset has.
 874          */
 875         if (chg > cpuset_mems_nr(free_huge_pages_node))
 876                 return -ENOMEM;
 877
 878         ret = hugetlb_acct_memory(chg);
 879         if (ret < 0)
 880                 return ret;
 881         region_add(&inode->i_mapping->private_list, from, to);
 882         return 0;
 883 }
 884
 885 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 886 {
 887         long chg = region_truncate(&inode->i_mapping->private_list, offset);
 888         hugetlb_acct_memory(freed - chg);
 889 }