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