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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 static unsigned long surplus_huge_pages;
  27 unsigned long max_huge_pages;
  28 static struct list_head hugepage_freelists[MAX_NUMNODES];
  29 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  30 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  31 static unsigned int surplus_huge_pages_node[MAX_NUMNODES];
  32 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
  33 unsigned long hugepages_treat_as_movable;
  34 int hugetlb_dynamic_pool;
  35 static int hugetlb_next_nid;
  36
  37 /*
  38  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  39  */
  40 static DEFINE_SPINLOCK(hugetlb_lock);
  41
  42 static void clear_huge_page(struct page *page, unsigned long addr)
  43 {
  44         int i;
  45
  46         might_sleep();
  47         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  48                 cond_resched();
  49                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
  50         }
  51 }
  52
  53 static void copy_huge_page(struct page *dst, struct page *src,
  54                            unsigned long addr, struct vm_area_struct *vma)
  55 {
  56         int i;
  57
  58         might_sleep();
  59         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  60                 cond_resched();
  61                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
  62         }
  63 }
  64
  65 static void enqueue_huge_page(struct page *page)
  66 {
  67         int nid = page_to_nid(page);
  68         list_add(&page->lru, &hugepage_freelists[nid]);
  69         free_huge_pages++;
  70         free_huge_pages_node[nid]++;
  71 }
  72
  73 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  74                                 unsigned long address)
  75 {
  76         int nid;
  77         struct page *page = NULL;
  78         struct mempolicy *mpol;
  79         struct zonelist *zonelist = huge_zonelist(vma, address,
  80                                         htlb_alloc_mask, &mpol);
  81         struct zone **z;
  82
  83         for (z = zonelist->zones; *z; z++) {
  84                 nid = zone_to_nid(*z);
  85                 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
  86                     !list_empty(&hugepage_freelists[nid])) {
  87                         page = list_entry(hugepage_freelists[nid].next,
  88                                           struct page, lru);
  89                         list_del(&page->lru);
  90                         free_huge_pages--;
  91                         free_huge_pages_node[nid]--;
  92                         if (vma && vma->vm_flags & VM_MAYSHARE)
  93                                 resv_huge_pages--;
  94                         break;
  95                 }
  96         }
  97         mpol_free(mpol);        /* unref if mpol !NULL */
  98         return page;
  99 }
 100
 101 static void update_and_free_page(struct page *page)
 102 {
 103         int i;
 104         nr_huge_pages--;
 105         nr_huge_pages_node[page_to_nid(page)]--;
 106         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 107                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 108                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 109                                 1 << PG_private | 1<< PG_writeback);
 110         }
 111         set_compound_page_dtor(page, NULL);
 112         set_page_refcounted(page);
 113         __free_pages(page, HUGETLB_PAGE_ORDER);
 114 }
 115
 116 static void free_huge_page(struct page *page)
 117 {
 118         int nid = page_to_nid(page);
 119         struct address_space *mapping;
 120
 121         mapping = (struct address_space *) page_private(page);
 122         BUG_ON(page_count(page));
 123         INIT_LIST_HEAD(&page->lru);
 124
 125         spin_lock(&hugetlb_lock);
 126         if (surplus_huge_pages_node[nid]) {
 127                 update_and_free_page(page);
 128                 surplus_huge_pages--;
 129                 surplus_huge_pages_node[nid]--;
 130         } else {
 131                 enqueue_huge_page(page);
 132         }
 133         spin_unlock(&hugetlb_lock);
 134         if (mapping)
 135                 hugetlb_put_quota(mapping);
 136         set_page_private(page, 0);
 137 }
 138
 139 /*
 140  * Increment or decrement surplus_huge_pages.  Keep node-specific counters
 141  * balanced by operating on them in a round-robin fashion.
 142  * Returns 1 if an adjustment was made.
 143  */
 144 static int adjust_pool_surplus(int delta)
 145 {
 146         static int prev_nid;
 147         int nid = prev_nid;
 148         int ret = 0;
 149
 150         VM_BUG_ON(delta != -1 && delta != 1);
 151         do {
 152                 nid = next_node(nid, node_online_map);
 153                 if (nid == MAX_NUMNODES)
 154                         nid = first_node(node_online_map);
 155
 156                 /* To shrink on this node, there must be a surplus page */
 157                 if (delta < 0 && !surplus_huge_pages_node[nid])
 158                         continue;
 159                 /* Surplus cannot exceed the total number of pages */
 160                 if (delta > 0 && surplus_huge_pages_node[nid] >=
 161                                                 nr_huge_pages_node[nid])
 162                         continue;
 163
 164                 surplus_huge_pages += delta;
 165                 surplus_huge_pages_node[nid] += delta;
 166                 ret = 1;
 167                 break;
 168         } while (nid != prev_nid);
 169
 170         prev_nid = nid;
 171         return ret;
 172 }
 173
 174 static struct page *alloc_fresh_huge_page_node(int nid)
 175 {
 176         struct page *page;
 177
 178         page = alloc_pages_node(nid,
 179                 htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|__GFP_NOWARN,
 180                 HUGETLB_PAGE_ORDER);
 181         if (page) {
 182                 set_compound_page_dtor(page, free_huge_page);
 183                 spin_lock(&hugetlb_lock);
 184                 nr_huge_pages++;
 185                 nr_huge_pages_node[nid]++;
 186                 spin_unlock(&hugetlb_lock);
 187                 put_page(page); /* free it into the hugepage allocator */
 188         }
 189
 190         return page;
 191 }
 192
 193 static int alloc_fresh_huge_page(void)
 194 {
 195         struct page *page;
 196         int start_nid;
 197         int next_nid;
 198         int ret = 0;
 199
 200         start_nid = hugetlb_next_nid;
 201
 202         do {
 203                 page = alloc_fresh_huge_page_node(hugetlb_next_nid);
 204                 if (page)
 205                         ret = 1;
 206                 /*
 207                  * Use a helper variable to find the next node and then
 208                  * copy it back to hugetlb_next_nid afterwards:
 209                  * otherwise there's a window in which a racer might
 210                  * pass invalid nid MAX_NUMNODES to alloc_pages_node.
 211                  * But we don't need to use a spin_lock here: it really
 212                  * doesn't matter if occasionally a racer chooses the
 213                  * same nid as we do.  Move nid forward in the mask even
 214                  * if we just successfully allocated a hugepage so that
 215                  * the next caller gets hugepages on the next node.
 216                  */
 217                 next_nid = next_node(hugetlb_next_nid, node_online_map);
 218                 if (next_nid == MAX_NUMNODES)
 219                         next_nid = first_node(node_online_map);
 220                 hugetlb_next_nid = next_nid;
 221         } while (!page && hugetlb_next_nid != start_nid);
 222
 223         return ret;
 224 }
 225
 226 static struct page *alloc_buddy_huge_page(struct vm_area_struct *vma,
 227                                                 unsigned long address)
 228 {
 229         struct page *page;
 230
 231         /* Check if the dynamic pool is enabled */
 232         if (!hugetlb_dynamic_pool)
 233                 return NULL;
 234
 235         page = alloc_pages(htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 236                                         HUGETLB_PAGE_ORDER);
 237         if (page) {
 238                 set_compound_page_dtor(page, free_huge_page);
 239                 spin_lock(&hugetlb_lock);
 240                 nr_huge_pages++;
 241                 nr_huge_pages_node[page_to_nid(page)]++;
 242                 surplus_huge_pages++;
 243                 surplus_huge_pages_node[page_to_nid(page)]++;
 244                 spin_unlock(&hugetlb_lock);
 245         }
 246
 247         return page;
 248 }
 249
 250 /*
 251  * Increase the hugetlb pool such that it can accomodate a reservation
 252  * of size 'delta'.
 253  */
 254 static int gather_surplus_pages(int delta)
 255 {
 256         struct list_head surplus_list;
 257         struct page *page, *tmp;
 258         int ret, i;
 259         int needed, allocated;
 260
 261         needed = (resv_huge_pages + delta) - free_huge_pages;
 262         if (needed <= 0)
 263                 return 0;
 264
 265         allocated = 0;
 266         INIT_LIST_HEAD(&surplus_list);
 267
 268         ret = -ENOMEM;
 269 retry:
 270         spin_unlock(&hugetlb_lock);
 271         for (i = 0; i < needed; i++) {
 272                 page = alloc_buddy_huge_page(NULL, 0);
 273                 if (!page) {
 274                         /*
 275                          * We were not able to allocate enough pages to
 276                          * satisfy the entire reservation so we free what
 277                          * we've allocated so far.
 278                          */
 279                         spin_lock(&hugetlb_lock);
 280                         needed = 0;
 281                         goto free;
 282                 }
 283
 284                 list_add(&page->lru, &surplus_list);
 285         }
 286         allocated += needed;
 287
 288         /*
 289          * After retaking hugetlb_lock, we need to recalculate 'needed'
 290          * because either resv_huge_pages or free_huge_pages may have changed.
 291          */
 292         spin_lock(&hugetlb_lock);
 293         needed = (resv_huge_pages + delta) - (free_huge_pages + allocated);
 294         if (needed > 0)
 295                 goto retry;
 296
 297         /*
 298          * The surplus_list now contains _at_least_ the number of extra pages
 299          * needed to accomodate the reservation.  Add the appropriate number
 300          * of pages to the hugetlb pool and free the extras back to the buddy
 301          * allocator.
 302          */
 303         needed += allocated;
 304         ret = 0;
 305 free:
 306         list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
 307                 list_del(&page->lru);
 308                 if ((--needed) >= 0)
 309                         enqueue_huge_page(page);
 310                 else {
 311                         /*
 312                          * Decrement the refcount and free the page using its
 313                          * destructor.  This must be done with hugetlb_lock
 314                          * unlocked which is safe because free_huge_page takes
 315                          * hugetlb_lock before deciding how to free the page.
 316                          */
 317                         spin_unlock(&hugetlb_lock);
 318                         put_page(page);
 319                         spin_lock(&hugetlb_lock);
 320                 }
 321         }
 322
 323         return ret;
 324 }
 325
 326 /*
 327  * When releasing a hugetlb pool reservation, any surplus pages that were
 328  * allocated to satisfy the reservation must be explicitly freed if they were
 329  * never used.
 330  */
 331 void return_unused_surplus_pages(unsigned long unused_resv_pages)
 332 {
 333         static int nid = -1;
 334         struct page *page;
 335         unsigned long nr_pages;
 336
 337         nr_pages = min(unused_resv_pages, surplus_huge_pages);
 338
 339         while (nr_pages) {
 340                 nid = next_node(nid, node_online_map);
 341                 if (nid == MAX_NUMNODES)
 342                         nid = first_node(node_online_map);
 343
 344                 if (!surplus_huge_pages_node[nid])
 345                         continue;
 346
 347                 if (!list_empty(&hugepage_freelists[nid])) {
 348                         page = list_entry(hugepage_freelists[nid].next,
 349                                           struct page, lru);
 350                         list_del(&page->lru);
 351                         update_and_free_page(page);
 352                         free_huge_pages--;
 353                         free_huge_pages_node[nid]--;
 354                         surplus_huge_pages--;
 355                         surplus_huge_pages_node[nid]--;
 356                         nr_pages--;
 357                 }
 358         }
 359 }
 360
 361
 362 static struct page *alloc_huge_page_shared(struct vm_area_struct *vma,
 363                                                 unsigned long addr)
 364 {
 365         struct page *page;
 366
 367         spin_lock(&hugetlb_lock);
 368         page = dequeue_huge_page(vma, addr);
 369         spin_unlock(&hugetlb_lock);
 370         return page;
 371 }
 372
 373 static struct page *alloc_huge_page_private(struct vm_area_struct *vma,
 374                                                 unsigned long addr)
 375 {
 376         struct page *page = NULL;
 377
 378         spin_lock(&hugetlb_lock);
 379         if (free_huge_pages > resv_huge_pages)
 380                 page = dequeue_huge_page(vma, addr);
 381         spin_unlock(&hugetlb_lock);
 382         if (!page)
 383                 page = alloc_buddy_huge_page(vma, addr);
 384         return page;
 385 }
 386
 387 static struct page *alloc_huge_page(struct vm_area_struct *vma,
 388                                     unsigned long addr)
 389 {
 390         struct page *page;
 391
 392         if (vma->vm_flags & VM_MAYSHARE)
 393                 page = alloc_huge_page_shared(vma, addr);
 394         else
 395                 page = alloc_huge_page_private(vma, addr);
 396         if (page) {
 397                 set_page_refcounted(page);
 398                 set_page_private(page, (unsigned long) vma->vm_file->f_mapping);
 399         }
 400         return page;
 401 }
 402
 403 static int __init hugetlb_init(void)
 404 {
 405         unsigned long i;
 406
 407         if (HPAGE_SHIFT == 0)
 408                 return 0;
 409
 410         for (i = 0; i < MAX_NUMNODES; ++i)
 411                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 412
 413         hugetlb_next_nid = first_node(node_online_map);
 414
 415         for (i = 0; i < max_huge_pages; ++i) {
 416                 if (!alloc_fresh_huge_page())
 417                         break;
 418         }
 419         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 420         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 421         return 0;
 422 }
 423 module_init(hugetlb_init);
 424
 425 static int __init hugetlb_setup(char *s)
 426 {
 427         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 428                 max_huge_pages = 0;
 429         return 1;
 430 }
 431 __setup("hugepages=", hugetlb_setup);
 432
 433 static unsigned int cpuset_mems_nr(unsigned int *array)
 434 {
 435         int node;
 436         unsigned int nr = 0;
 437
 438         for_each_node_mask(node, cpuset_current_mems_allowed)
 439                 nr += array[node];
 440
 441         return nr;
 442 }
 443
 444 #ifdef CONFIG_SYSCTL
 445 #ifdef CONFIG_HIGHMEM
 446 static void try_to_free_low(unsigned long count)
 447 {
 448         int i;
 449
 450         for (i = 0; i < MAX_NUMNODES; ++i) {
 451                 struct page *page, *next;
 452                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 453                         if (count >= nr_huge_pages)
 454                                 return;
 455                         if (PageHighMem(page))
 456                                 continue;
 457                         list_del(&page->lru);
 458                         update_and_free_page(page);
 459                         free_huge_pages--;
 460                         free_huge_pages_node[page_to_nid(page)]--;
 461                 }
 462         }
 463 }
 464 #else
 465 static inline void try_to_free_low(unsigned long count)
 466 {
 467 }
 468 #endif
 469
 470 #define persistent_huge_pages (nr_huge_pages - surplus_huge_pages)
 471 static unsigned long set_max_huge_pages(unsigned long count)
 472 {
 473         unsigned long min_count, ret;
 474
 475         /*
 476          * Increase the pool size
 477          * First take pages out of surplus state.  Then make up the
 478          * remaining difference by allocating fresh huge pages.
 479          */
 480         spin_lock(&hugetlb_lock);
 481         while (surplus_huge_pages && count > persistent_huge_pages) {
 482                 if (!adjust_pool_surplus(-1))
 483                         break;
 484         }
 485
 486         while (count > persistent_huge_pages) {
 487                 int ret;
 488                 /*
 489                  * If this allocation races such that we no longer need the
 490                  * page, free_huge_page will handle it by freeing the page
 491                  * and reducing the surplus.
 492                  */
 493                 spin_unlock(&hugetlb_lock);
 494                 ret = alloc_fresh_huge_page();
 495                 spin_lock(&hugetlb_lock);
 496                 if (!ret)
 497                         goto out;
 498
 499         }
 500
 501         /*
 502          * Decrease the pool size
 503          * First return free pages to the buddy allocator (being careful
 504          * to keep enough around to satisfy reservations).  Then place
 505          * pages into surplus state as needed so the pool will shrink
 506          * to the desired size as pages become free.
 507          */
 508         min_count = resv_huge_pages + nr_huge_pages - free_huge_pages;
 509         min_count = max(count, min_count);
 510         try_to_free_low(min_count);
 511         while (min_count < persistent_huge_pages) {
 512                 struct page *page = dequeue_huge_page(NULL, 0);
 513                 if (!page)
 514                         break;
 515                 update_and_free_page(page);
 516         }
 517         while (count < persistent_huge_pages) {
 518                 if (!adjust_pool_surplus(1))
 519                         break;
 520         }
 521 out:
 522         ret = persistent_huge_pages;
 523         spin_unlock(&hugetlb_lock);
 524         return ret;
 525 }
 526
 527 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 528                            struct file *file, void __user *buffer,
 529                            size_t *length, loff_t *ppos)
 530 {
 531         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 532         max_huge_pages = set_max_huge_pages(max_huge_pages);
 533         return 0;
 534 }
 535
 536 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 537                         struct file *file, void __user *buffer,
 538                         size_t *length, loff_t *ppos)
 539 {
 540         proc_dointvec(table, write, file, buffer, length, ppos);
 541         if (hugepages_treat_as_movable)
 542                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
 543         else
 544                 htlb_alloc_mask = GFP_HIGHUSER;
 545         return 0;
 546 }
 547
 548 #endif /* CONFIG_SYSCTL */
 549
 550 int hugetlb_report_meminfo(char *buf)
 551 {
 552         return sprintf(buf,
 553                         "HugePages_Total: %5lu\n"
 554                         "HugePages_Free:  %5lu\n"
 555                         "HugePages_Rsvd:  %5lu\n"
 556                         "HugePages_Surp:  %5lu\n"
 557                         "Hugepagesize:    %5lu kB\n",
 558                         nr_huge_pages,
 559                         free_huge_pages,
 560                         resv_huge_pages,
 561                         surplus_huge_pages,
 562                         HPAGE_SIZE/1024);
 563 }
 564
 565 int hugetlb_report_node_meminfo(int nid, char *buf)
 566 {
 567         return sprintf(buf,
 568                 "Node %d HugePages_Total: %5u\n"
 569                 "Node %d HugePages_Free:  %5u\n",
 570                 nid, nr_huge_pages_node[nid],
 571                 nid, free_huge_pages_node[nid]);
 572 }
 573
 574 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 575 unsigned long hugetlb_total_pages(void)
 576 {
 577         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 578 }
 579
 580 /*
 581  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 582  * handle_mm_fault() to try to instantiate regular-sized pages in the
 583  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 584  * this far.
 585  */
 586 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 587 {
 588         BUG();
 589         return 0;
 590 }
 591
 592 struct vm_operations_struct hugetlb_vm_ops = {
 593         .fault = hugetlb_vm_op_fault,
 594 };
 595
 596 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 597                                 int writable)
 598 {
 599         pte_t entry;
 600
 601         if (writable) {
 602                 entry =
 603                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 604         } else {
 605                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 606         }
 607         entry = pte_mkyoung(entry);
 608         entry = pte_mkhuge(entry);
 609
 610         return entry;
 611 }
 612
 613 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 614                                    unsigned long address, pte_t *ptep)
 615 {
 616         pte_t entry;
 617
 618         entry = pte_mkwrite(pte_mkdirty(*ptep));
 619         if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
 620                 update_mmu_cache(vma, address, entry);
 621         }
 622 }
 623
 624
 625 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 626                             struct vm_area_struct *vma)
 627 {
 628         pte_t *src_pte, *dst_pte, entry;
 629         struct page *ptepage;
 630         unsigned long addr;
 631         int cow;
 632
 633         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 634
 635         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 636                 src_pte = huge_pte_offset(src, addr);
 637                 if (!src_pte)
 638                         continue;
 639                 dst_pte = huge_pte_alloc(dst, addr);
 640                 if (!dst_pte)
 641                         goto nomem;
 642                 spin_lock(&dst->page_table_lock);
 643                 spin_lock(&src->page_table_lock);
 644                 if (!pte_none(*src_pte)) {
 645                         if (cow)
 646                                 ptep_set_wrprotect(src, addr, src_pte);
 647                         entry = *src_pte;
 648                         ptepage = pte_page(entry);
 649                         get_page(ptepage);
 650                         set_huge_pte_at(dst, addr, dst_pte, entry);
 651                 }
 652                 spin_unlock(&src->page_table_lock);
 653                 spin_unlock(&dst->page_table_lock);
 654         }
 655         return 0;
 656
 657 nomem:
 658         return -ENOMEM;
 659 }
 660
 661 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 662                             unsigned long end)
 663 {
 664         struct mm_struct *mm = vma->vm_mm;
 665         unsigned long address;
 666         pte_t *ptep;
 667         pte_t pte;
 668         struct page *page;
 669         struct page *tmp;
 670         /*
 671          * A page gathering list, protected by per file i_mmap_lock. The
 672          * lock is used to avoid list corruption from multiple unmapping
 673          * of the same page since we are using page->lru.
 674          */
 675         LIST_HEAD(page_list);
 676
 677         WARN_ON(!is_vm_hugetlb_page(vma));
 678         BUG_ON(start & ~HPAGE_MASK);
 679         BUG_ON(end & ~HPAGE_MASK);
 680
 681         spin_lock(&mm->page_table_lock);
 682         for (address = start; address < end; address += HPAGE_SIZE) {
 683                 ptep = huge_pte_offset(mm, address);
 684                 if (!ptep)
 685                         continue;
 686
 687                 if (huge_pmd_unshare(mm, &address, ptep))
 688                         continue;
 689
 690                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 691                 if (pte_none(pte))
 692                         continue;
 693
 694                 page = pte_page(pte);
 695                 if (pte_dirty(pte))
 696                         set_page_dirty(page);
 697                 list_add(&page->lru, &page_list);
 698         }
 699         spin_unlock(&mm->page_table_lock);
 700         flush_tlb_range(vma, start, end);
 701         list_for_each_entry_safe(page, tmp, &page_list, lru) {
 702                 list_del(&page->lru);
 703                 put_page(page);
 704         }
 705 }
 706
 707 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 708                           unsigned long end)
 709 {
 710         /*
 711          * It is undesirable to test vma->vm_file as it should be non-null
 712          * for valid hugetlb area. However, vm_file will be NULL in the error
 713          * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
 714          * do_mmap_pgoff() nullifies vma->vm_file before calling this function
 715          * to clean up. Since no pte has actually been setup, it is safe to
 716          * do nothing in this case.
 717          */
 718         if (vma->vm_file) {
 719                 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 720                 __unmap_hugepage_range(vma, start, end);
 721                 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 722         }
 723 }
 724
 725 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 726                         unsigned long address, pte_t *ptep, pte_t pte)
 727 {
 728         struct page *old_page, *new_page;
 729         int avoidcopy;
 730
 731         old_page = pte_page(pte);
 732
 733         /* If no-one else is actually using this page, avoid the copy
 734          * and just make the page writable */
 735         avoidcopy = (page_count(old_page) == 1);
 736         if (avoidcopy) {
 737                 set_huge_ptep_writable(vma, address, ptep);
 738                 return 0;
 739         }
 740         if (hugetlb_get_quota(vma->vm_file->f_mapping))
 741                 return VM_FAULT_SIGBUS;
 742
 743         page_cache_get(old_page);
 744         new_page = alloc_huge_page(vma, address);
 745
 746         if (!new_page) {
 747                 page_cache_release(old_page);
 748                 return VM_FAULT_OOM;
 749         }
 750
 751         spin_unlock(&mm->page_table_lock);
 752         copy_huge_page(new_page, old_page, address, vma);
 753         spin_lock(&mm->page_table_lock);
 754
 755         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 756         if (likely(pte_same(*ptep, pte))) {
 757                 /* Break COW */
 758                 set_huge_pte_at(mm, address, ptep,
 759                                 make_huge_pte(vma, new_page, 1));
 760                 /* Make the old page be freed below */
 761                 new_page = old_page;
 762         }
 763         page_cache_release(new_page);
 764         page_cache_release(old_page);
 765         return 0;
 766 }
 767
 768 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 769                         unsigned long address, pte_t *ptep, int write_access)
 770 {
 771         int ret = VM_FAULT_SIGBUS;
 772         unsigned long idx;
 773         unsigned long size;
 774         struct page *page;
 775         struct address_space *mapping;
 776         pte_t new_pte;
 777
 778         mapping = vma->vm_file->f_mapping;
 779         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 780                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 781
 782         /*
 783          * Use page lock to guard against racing truncation
 784          * before we get page_table_lock.
 785          */
 786 retry:
 787         page = find_lock_page(mapping, idx);
 788         if (!page) {
 789                 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 790                 if (idx >= size)
 791                         goto out;
 792                 if (hugetlb_get_quota(mapping))
 793                         goto out;
 794                 page = alloc_huge_page(vma, address);
 795                 if (!page) {
 796                         hugetlb_put_quota(mapping);
 797                         ret = VM_FAULT_OOM;
 798                         goto out;
 799                 }
 800                 clear_huge_page(page, address);
 801
 802                 if (vma->vm_flags & VM_SHARED) {
 803                         int err;
 804
 805                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 806                         if (err) {
 807                                 put_page(page);
 808                                 if (err == -EEXIST)
 809                                         goto retry;
 810                                 goto out;
 811                         }
 812                 } else
 813                         lock_page(page);
 814         }
 815
 816         spin_lock(&mm->page_table_lock);
 817         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 818         if (idx >= size)
 819                 goto backout;
 820
 821         ret = 0;
 822         if (!pte_none(*ptep))
 823                 goto backout;
 824
 825         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 826                                 && (vma->vm_flags & VM_SHARED)));
 827         set_huge_pte_at(mm, address, ptep, new_pte);
 828
 829         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 830                 /* Optimization, do the COW without a second fault */
 831                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 832         }
 833
 834         spin_unlock(&mm->page_table_lock);
 835         unlock_page(page);
 836 out:
 837         return ret;
 838
 839 backout:
 840         spin_unlock(&mm->page_table_lock);
 841         unlock_page(page);
 842         put_page(page);
 843         goto out;
 844 }
 845
 846 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 847                         unsigned long address, int write_access)
 848 {
 849         pte_t *ptep;
 850         pte_t entry;
 851         int ret;
 852         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 853
 854         ptep = huge_pte_alloc(mm, address);
 855         if (!ptep)
 856                 return VM_FAULT_OOM;
 857
 858         /*
 859          * Serialize hugepage allocation and instantiation, so that we don't
 860          * get spurious allocation failures if two CPUs race to instantiate
 861          * the same page in the page cache.
 862          */
 863         mutex_lock(&hugetlb_instantiation_mutex);
 864         entry = *ptep;
 865         if (pte_none(entry)) {
 866                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 867                 mutex_unlock(&hugetlb_instantiation_mutex);
 868                 return ret;
 869         }
 870
 871         ret = 0;
 872
 873         spin_lock(&mm->page_table_lock);
 874         /* Check for a racing update before calling hugetlb_cow */
 875         if (likely(pte_same(entry, *ptep)))
 876                 if (write_access && !pte_write(entry))
 877                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 878         spin_unlock(&mm->page_table_lock);
 879         mutex_unlock(&hugetlb_instantiation_mutex);
 880
 881         return ret;
 882 }
 883
 884 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 885                         struct page **pages, struct vm_area_struct **vmas,
 886                         unsigned long *position, int *length, int i,
 887                         int write)
 888 {
 889         unsigned long pfn_offset;
 890         unsigned long vaddr = *position;
 891         int remainder = *length;
 892
 893         spin_lock(&mm->page_table_lock);
 894         while (vaddr < vma->vm_end && remainder) {
 895                 pte_t *pte;
 896                 struct page *page;
 897
 898                 /*
 899                  * Some archs (sparc64, sh*) have multiple pte_ts to
 900                  * each hugepage.  We have to make * sure we get the
 901                  * first, for the page indexing below to work.
 902                  */
 903                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 904
 905                 if (!pte || pte_none(*pte)) {
 906                         int ret;
 907
 908                         spin_unlock(&mm->page_table_lock);
 909                         ret = hugetlb_fault(mm, vma, vaddr, write);
 910                         spin_lock(&mm->page_table_lock);
 911                         if (!(ret & VM_FAULT_ERROR))
 912                                 continue;
 913
 914                         remainder = 0;
 915                         if (!i)
 916                                 i = -EFAULT;
 917                         break;
 918                 }
 919
 920                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
 921                 page = pte_page(*pte);
 922 same_page:
 923                 if (pages) {
 924                         get_page(page);
 925                         pages[i] = page + pfn_offset;
 926                 }
 927
 928                 if (vmas)
 929                         vmas[i] = vma;
 930
 931                 vaddr += PAGE_SIZE;
 932                 ++pfn_offset;
 933                 --remainder;
 934                 ++i;
 935                 if (vaddr < vma->vm_end && remainder &&
 936                                 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
 937                         /*
 938                          * We use pfn_offset to avoid touching the pageframes
 939                          * of this compound page.
 940                          */
 941                         goto same_page;
 942                 }
 943         }
 944         spin_unlock(&mm->page_table_lock);
 945         *length = remainder;
 946         *position = vaddr;
 947
 948         return i;
 949 }
 950
 951 void hugetlb_change_protection(struct vm_area_struct *vma,
 952                 unsigned long address, unsigned long end, pgprot_t newprot)
 953 {
 954         struct mm_struct *mm = vma->vm_mm;
 955         unsigned long start = address;
 956         pte_t *ptep;
 957         pte_t pte;
 958
 959         BUG_ON(address >= end);
 960         flush_cache_range(vma, address, end);
 961
 962         spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
 963         spin_lock(&mm->page_table_lock);
 964         for (; address < end; address += HPAGE_SIZE) {
 965                 ptep = huge_pte_offset(mm, address);
 966                 if (!ptep)
 967                         continue;
 968                 if (huge_pmd_unshare(mm, &address, ptep))
 969                         continue;
 970                 if (!pte_none(*ptep)) {
 971                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 972                         pte = pte_mkhuge(pte_modify(pte, newprot));
 973                         set_huge_pte_at(mm, address, ptep, pte);
 974                 }
 975         }
 976         spin_unlock(&mm->page_table_lock);
 977         spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
 978
 979         flush_tlb_range(vma, start, end);
 980 }
 981
 982 struct file_region {
 983         struct list_head link;
 984         long from;
 985         long to;
 986 };
 987
 988 static long region_add(struct list_head *head, long f, long t)
 989 {
 990         struct file_region *rg, *nrg, *trg;
 991
 992         /* Locate the region we are either in or before. */
 993         list_for_each_entry(rg, head, link)
 994                 if (f <= rg->to)
 995                         break;
 996
 997         /* Round our left edge to the current segment if it encloses us. */
 998         if (f > rg->from)
 999                 f = rg->from;
1000
1001         /* Check for and consume any regions we now overlap with. */
1002         nrg = rg;
1003         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1004                 if (&rg->link == head)
1005                         break;
1006                 if (rg->from > t)
1007                         break;
1008
1009                 /* If this area reaches higher then extend our area to
1010                  * include it completely.  If this is not the first area
1011                  * which we intend to reuse, free it. */
1012                 if (rg->to > t)
1013                         t = rg->to;
1014                 if (rg != nrg) {
1015                         list_del(&rg->link);
1016                         kfree(rg);
1017                 }
1018         }
1019         nrg->from = f;
1020         nrg->to = t;
1021         return 0;
1022 }
1023
1024 static long region_chg(struct list_head *head, long f, long t)
1025 {
1026         struct file_region *rg, *nrg;
1027         long chg = 0;
1028
1029         /* Locate the region we are before or in. */
1030         list_for_each_entry(rg, head, link)
1031                 if (f <= rg->to)
1032                         break;
1033
1034         /* If we are below the current region then a new region is required.
1035          * Subtle, allocate a new region at the position but make it zero
1036          * size such that we can guarantee to record the reservation. */
1037         if (&rg->link == head || t < rg->from) {
1038                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
1039                 if (!nrg)
1040                         return -ENOMEM;
1041                 nrg->from = f;
1042                 nrg->to   = f;
1043                 INIT_LIST_HEAD(&nrg->link);
1044                 list_add(&nrg->link, rg->link.prev);
1045
1046                 return t - f;
1047         }
1048
1049         /* Round our left edge to the current segment if it encloses us. */
1050         if (f > rg->from)
1051                 f = rg->from;
1052         chg = t - f;
1053
1054         /* Check for and consume any regions we now overlap with. */
1055         list_for_each_entry(rg, rg->link.prev, link) {
1056                 if (&rg->link == head)
1057                         break;
1058                 if (rg->from > t)
1059                         return chg;
1060
1061                 /* We overlap with this area, if it extends futher than
1062                  * us then we must extend ourselves.  Account for its
1063                  * existing reservation. */
1064                 if (rg->to > t) {
1065                         chg += rg->to - t;
1066                         t = rg->to;
1067                 }
1068                 chg -= rg->to - rg->from;
1069         }
1070         return chg;
1071 }
1072
1073 static long region_truncate(struct list_head *head, long end)
1074 {
1075         struct file_region *rg, *trg;
1076         long chg = 0;
1077
1078         /* Locate the region we are either in or before. */
1079         list_for_each_entry(rg, head, link)
1080                 if (end <= rg->to)
1081                         break;
1082         if (&rg->link == head)
1083                 return 0;
1084
1085         /* If we are in the middle of a region then adjust it. */
1086         if (end > rg->from) {
1087                 chg = rg->to - end;
1088                 rg->to = end;
1089                 rg = list_entry(rg->link.next, typeof(*rg), link);
1090         }
1091
1092         /* Drop any remaining regions. */
1093         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1094                 if (&rg->link == head)
1095                         break;
1096                 chg += rg->to - rg->from;
1097                 list_del(&rg->link);
1098                 kfree(rg);
1099         }
1100         return chg;
1101 }
1102
1103 static int hugetlb_acct_memory(long delta)
1104 {
1105         int ret = -ENOMEM;
1106
1107         spin_lock(&hugetlb_lock);
1108         /*
1109          * When cpuset is configured, it breaks the strict hugetlb page
1110          * reservation as the accounting is done on a global variable. Such
1111          * reservation is completely rubbish in the presence of cpuset because
1112          * the reservation is not checked against page availability for the
1113          * current cpuset. Application can still potentially OOM'ed by kernel
1114          * with lack of free htlb page in cpuset that the task is in.
1115          * Attempt to enforce strict accounting with cpuset is almost
1116          * impossible (or too ugly) because cpuset is too fluid that
1117          * task or memory node can be dynamically moved between cpusets.
1118          *
1119          * The change of semantics for shared hugetlb mapping with cpuset is
1120          * undesirable. However, in order to preserve some of the semantics,
1121          * we fall back to check against current free page availability as
1122          * a best attempt and hopefully to minimize the impact of changing
1123          * semantics that cpuset has.
1124          */
1125         if (delta > 0) {
1126                 if (gather_surplus_pages(delta) < 0)
1127                         goto out;
1128
1129                 if (delta > cpuset_mems_nr(free_huge_pages_node))
1130                         goto out;
1131         }
1132
1133         ret = 0;
1134         resv_huge_pages += delta;
1135         if (delta < 0)
1136                 return_unused_surplus_pages((unsigned long) -delta);
1137
1138 out:
1139         spin_unlock(&hugetlb_lock);
1140         return ret;
1141 }
1142
1143 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
1144 {
1145         long ret, chg;
1146
1147         chg = region_chg(&inode->i_mapping->private_list, from, to);
1148         if (chg < 0)
1149                 return chg;
1150
1151         ret = hugetlb_acct_memory(chg);
1152         if (ret < 0)
1153                 return ret;
1154         region_add(&inode->i_mapping->private_list, from, to);
1155         return 0;
1156 }
1157
1158 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
1159 {
1160         long chg = region_truncate(&inode->i_mapping->private_list, offset);
1161         hugetlb_acct_memory(freed - chg);
1162 }