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 <asm/page.h>
  15 #include <asm/pgtable.h>
  16
  17 #include <linux/hugetlb.h>
  18
  19 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  20 static unsigned long nr_huge_pages, free_huge_pages;
  21 unsigned long max_huge_pages;
  22 static struct list_head hugepage_freelists[MAX_NUMNODES];
  23 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  24 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  25
  26 /*
  27  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  28  */
  29 static DEFINE_SPINLOCK(hugetlb_lock);
  30
  31 static void enqueue_huge_page(struct page *page)
  32 {
  33         int nid = page_to_nid(page);
  34         list_add(&page->lru, &hugepage_freelists[nid]);
  35         free_huge_pages++;
  36         free_huge_pages_node[nid]++;
  37 }
  38
  39 static struct page *dequeue_huge_page(void)
  40 {
  41         int nid = numa_node_id();
  42         struct page *page = NULL;
  43
  44         if (list_empty(&hugepage_freelists[nid])) {
  45                 for (nid = 0; nid < MAX_NUMNODES; ++nid)
  46                         if (!list_empty(&hugepage_freelists[nid]))
  47                                 break;
  48         }
  49         if (nid >= 0 && nid < MAX_NUMNODES &&
  50             !list_empty(&hugepage_freelists[nid])) {
  51                 page = list_entry(hugepage_freelists[nid].next,
  52                                   struct page, lru);
  53                 list_del(&page->lru);
  54                 free_huge_pages--;
  55                 free_huge_pages_node[nid]--;
  56         }
  57         return page;
  58 }
  59
  60 static struct page *alloc_fresh_huge_page(void)
  61 {
  62         static int nid = 0;
  63         struct page *page;
  64         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
  65                                         HUGETLB_PAGE_ORDER);
  66         nid = (nid + 1) % num_online_nodes();
  67         if (page) {
  68                 spin_lock(&hugetlb_lock);
  69                 nr_huge_pages++;
  70                 nr_huge_pages_node[page_to_nid(page)]++;
  71                 spin_unlock(&hugetlb_lock);
  72         }
  73         return page;
  74 }
  75
  76 void free_huge_page(struct page *page)
  77 {
  78         BUG_ON(page_count(page));
  79
  80         INIT_LIST_HEAD(&page->lru);
  81         page[1].mapping = NULL;
  82
  83         spin_lock(&hugetlb_lock);
  84         enqueue_huge_page(page);
  85         spin_unlock(&hugetlb_lock);
  86 }
  87
  88 struct page *alloc_huge_page(void)
  89 {
  90         struct page *page;
  91         int i;
  92
  93         spin_lock(&hugetlb_lock);
  94         page = dequeue_huge_page();
  95         if (!page) {
  96                 spin_unlock(&hugetlb_lock);
  97                 return NULL;
  98         }
  99         spin_unlock(&hugetlb_lock);
 100         set_page_count(page, 1);
 101         page[1].mapping = (void *)free_huge_page;
 102         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
 103                 clear_highpage(&page[i]);
 104         return page;
 105 }
 106
 107 static int __init hugetlb_init(void)
 108 {
 109         unsigned long i;
 110         struct page *page;
 111
 112         if (HPAGE_SHIFT == 0)
 113                 return 0;
 114
 115         for (i = 0; i < MAX_NUMNODES; ++i)
 116                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 117
 118         for (i = 0; i < max_huge_pages; ++i) {
 119                 page = alloc_fresh_huge_page();
 120                 if (!page)
 121                         break;
 122                 spin_lock(&hugetlb_lock);
 123                 enqueue_huge_page(page);
 124                 spin_unlock(&hugetlb_lock);
 125         }
 126         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 127         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 128         return 0;
 129 }
 130 module_init(hugetlb_init);
 131
 132 static int __init hugetlb_setup(char *s)
 133 {
 134         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 135                 max_huge_pages = 0;
 136         return 1;
 137 }
 138 __setup("hugepages=", hugetlb_setup);
 139
 140 #ifdef CONFIG_SYSCTL
 141 static void update_and_free_page(struct page *page)
 142 {
 143         int i;
 144         nr_huge_pages--;
 145         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 146         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 147                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 148                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 149                                 1 << PG_private | 1<< PG_writeback);
 150                 set_page_count(&page[i], 0);
 151         }
 152         set_page_count(page, 1);
 153         __free_pages(page, HUGETLB_PAGE_ORDER);
 154 }
 155
 156 #ifdef CONFIG_HIGHMEM
 157 static void try_to_free_low(unsigned long count)
 158 {
 159         int i, nid;
 160         for (i = 0; i < MAX_NUMNODES; ++i) {
 161                 struct page *page, *next;
 162                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 163                         if (PageHighMem(page))
 164                                 continue;
 165                         list_del(&page->lru);
 166                         update_and_free_page(page);
 167                         nid = page_zone(page)->zone_pgdat->node_id;
 168                         free_huge_pages--;
 169                         free_huge_pages_node[nid]--;
 170                         if (count >= nr_huge_pages)
 171                                 return;
 172                 }
 173         }
 174 }
 175 #else
 176 static inline void try_to_free_low(unsigned long count)
 177 {
 178 }
 179 #endif
 180
 181 static unsigned long set_max_huge_pages(unsigned long count)
 182 {
 183         while (count > nr_huge_pages) {
 184                 struct page *page = alloc_fresh_huge_page();
 185                 if (!page)
 186                         return nr_huge_pages;
 187                 spin_lock(&hugetlb_lock);
 188                 enqueue_huge_page(page);
 189                 spin_unlock(&hugetlb_lock);
 190         }
 191         if (count >= nr_huge_pages)
 192                 return nr_huge_pages;
 193
 194         spin_lock(&hugetlb_lock);
 195         try_to_free_low(count);
 196         while (count < nr_huge_pages) {
 197                 struct page *page = dequeue_huge_page();
 198                 if (!page)
 199                         break;
 200                 update_and_free_page(page);
 201         }
 202         spin_unlock(&hugetlb_lock);
 203         return nr_huge_pages;
 204 }
 205
 206 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 207                            struct file *file, void __user *buffer,
 208                            size_t *length, loff_t *ppos)
 209 {
 210         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 211         max_huge_pages = set_max_huge_pages(max_huge_pages);
 212         return 0;
 213 }
 214 #endif /* CONFIG_SYSCTL */
 215
 216 int hugetlb_report_meminfo(char *buf)
 217 {
 218         return sprintf(buf,
 219                         "HugePages_Total: %5lu\n"
 220                         "HugePages_Free:  %5lu\n"
 221                         "Hugepagesize:    %5lu kB\n",
 222                         nr_huge_pages,
 223                         free_huge_pages,
 224                         HPAGE_SIZE/1024);
 225 }
 226
 227 int hugetlb_report_node_meminfo(int nid, char *buf)
 228 {
 229         return sprintf(buf,
 230                 "Node %d HugePages_Total: %5u\n"
 231                 "Node %d HugePages_Free:  %5u\n",
 232                 nid, nr_huge_pages_node[nid],
 233                 nid, free_huge_pages_node[nid]);
 234 }
 235
 236 int is_hugepage_mem_enough(size_t size)
 237 {
 238         return (size + ~HPAGE_MASK)/HPAGE_SIZE <= free_huge_pages;
 239 }
 240
 241 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 242 unsigned long hugetlb_total_pages(void)
 243 {
 244         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 245 }
 246
 247 /*
 248  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 249  * handle_mm_fault() to try to instantiate regular-sized pages in the
 250  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 251  * this far.
 252  */
 253 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 254                                 unsigned long address, int *unused)
 255 {
 256         BUG();
 257         return NULL;
 258 }
 259
 260 struct vm_operations_struct hugetlb_vm_ops = {
 261         .nopage = hugetlb_nopage,
 262 };
 263
 264 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 265                                 int writable)
 266 {
 267         pte_t entry;
 268
 269         if (writable) {
 270                 entry =
 271                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 272         } else {
 273                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 274         }
 275         entry = pte_mkyoung(entry);
 276         entry = pte_mkhuge(entry);
 277
 278         return entry;
 279 }
 280
 281 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 282                                    unsigned long address, pte_t *ptep)
 283 {
 284         pte_t entry;
 285
 286         entry = pte_mkwrite(pte_mkdirty(*ptep));
 287         ptep_set_access_flags(vma, address, ptep, entry, 1);
 288         update_mmu_cache(vma, address, entry);
 289         lazy_mmu_prot_update(entry);
 290 }
 291
 292
 293 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 294                             struct vm_area_struct *vma)
 295 {
 296         pte_t *src_pte, *dst_pte, entry;
 297         struct page *ptepage;
 298         unsigned long addr;
 299         int cow;
 300
 301         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 302
 303         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 304                 src_pte = huge_pte_offset(src, addr);
 305                 if (!src_pte)
 306                         continue;
 307                 dst_pte = huge_pte_alloc(dst, addr);
 308                 if (!dst_pte)
 309                         goto nomem;
 310                 spin_lock(&dst->page_table_lock);
 311                 spin_lock(&src->page_table_lock);
 312                 if (!pte_none(*src_pte)) {
 313                         if (cow)
 314                                 ptep_set_wrprotect(src, addr, src_pte);
 315                         entry = *src_pte;
 316                         ptepage = pte_page(entry);
 317                         get_page(ptepage);
 318                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 319                         set_huge_pte_at(dst, addr, dst_pte, entry);
 320                 }
 321                 spin_unlock(&src->page_table_lock);
 322                 spin_unlock(&dst->page_table_lock);
 323         }
 324         return 0;
 325
 326 nomem:
 327         return -ENOMEM;
 328 }
 329
 330 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 331                           unsigned long end)
 332 {
 333         struct mm_struct *mm = vma->vm_mm;
 334         unsigned long address;
 335         pte_t *ptep;
 336         pte_t pte;
 337         struct page *page;
 338
 339         WARN_ON(!is_vm_hugetlb_page(vma));
 340         BUG_ON(start & ~HPAGE_MASK);
 341         BUG_ON(end & ~HPAGE_MASK);
 342
 343         spin_lock(&mm->page_table_lock);
 344
 345         /* Update high watermark before we lower rss */
 346         update_hiwater_rss(mm);
 347
 348         for (address = start; address < end; address += HPAGE_SIZE) {
 349                 ptep = huge_pte_offset(mm, address);
 350                 if (!ptep)
 351                         continue;
 352
 353                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 354                 if (pte_none(pte))
 355                         continue;
 356
 357                 page = pte_page(pte);
 358                 put_page(page);
 359                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 360         }
 361
 362         spin_unlock(&mm->page_table_lock);
 363         flush_tlb_range(vma, start, end);
 364 }
 365
 366 static struct page *find_or_alloc_huge_page(struct address_space *mapping,
 367                                 unsigned long idx, int shared)
 368 {
 369         struct page *page;
 370         int err;
 371
 372 retry:
 373         page = find_lock_page(mapping, idx);
 374         if (page)
 375                 goto out;
 376
 377         if (hugetlb_get_quota(mapping))
 378                 goto out;
 379         page = alloc_huge_page();
 380         if (!page) {
 381                 hugetlb_put_quota(mapping);
 382                 goto out;
 383         }
 384
 385         if (shared) {
 386                 err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 387                 if (err) {
 388                         put_page(page);
 389                         hugetlb_put_quota(mapping);
 390                         if (err == -EEXIST)
 391                                 goto retry;
 392                         page = NULL;
 393                 }
 394         } else {
 395                 /* Caller expects a locked page */
 396                 lock_page(page);
 397         }
 398 out:
 399         return page;
 400 }
 401
 402 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 403                         unsigned long address, pte_t *ptep, pte_t pte)
 404 {
 405         struct page *old_page, *new_page;
 406         int i, avoidcopy;
 407
 408         old_page = pte_page(pte);
 409
 410         /* If no-one else is actually using this page, avoid the copy
 411          * and just make the page writable */
 412         avoidcopy = (page_count(old_page) == 1);
 413         if (avoidcopy) {
 414                 set_huge_ptep_writable(vma, address, ptep);
 415                 return VM_FAULT_MINOR;
 416         }
 417
 418         page_cache_get(old_page);
 419         new_page = alloc_huge_page();
 420
 421         if (!new_page) {
 422                 page_cache_release(old_page);
 423
 424                 /* Logically this is OOM, not a SIGBUS, but an OOM
 425                  * could cause the kernel to go killing other
 426                  * processes which won't help the hugepage situation
 427                  * at all (?) */
 428                 return VM_FAULT_SIGBUS;
 429         }
 430
 431         spin_unlock(&mm->page_table_lock);
 432         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++)
 433                 copy_user_highpage(new_page + i, old_page + i,
 434                                    address + i*PAGE_SIZE);
 435         spin_lock(&mm->page_table_lock);
 436
 437         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 438         if (likely(pte_same(*ptep, pte))) {
 439                 /* Break COW */
 440                 set_huge_pte_at(mm, address, ptep,
 441                                 make_huge_pte(vma, new_page, 1));
 442                 /* Make the old page be freed below */
 443                 new_page = old_page;
 444         }
 445         page_cache_release(new_page);
 446         page_cache_release(old_page);
 447         return VM_FAULT_MINOR;
 448 }
 449
 450 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 451                         unsigned long address, pte_t *ptep, int write_access)
 452 {
 453         int ret = VM_FAULT_SIGBUS;
 454         unsigned long idx;
 455         unsigned long size;
 456         struct page *page;
 457         struct address_space *mapping;
 458         pte_t new_pte;
 459
 460         mapping = vma->vm_file->f_mapping;
 461         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 462                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 463
 464         /*
 465          * Use page lock to guard against racing truncation
 466          * before we get page_table_lock.
 467          */
 468         page = find_or_alloc_huge_page(mapping, idx,
 469                         vma->vm_flags & VM_SHARED);
 470         if (!page)
 471                 goto out;
 472
 473         BUG_ON(!PageLocked(page));
 474
 475         spin_lock(&mm->page_table_lock);
 476         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 477         if (idx >= size)
 478                 goto backout;
 479
 480         ret = VM_FAULT_MINOR;
 481         if (!pte_none(*ptep))
 482                 goto backout;
 483
 484         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 485         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 486                                 && (vma->vm_flags & VM_SHARED)));
 487         set_huge_pte_at(mm, address, ptep, new_pte);
 488
 489         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 490                 /* Optimization, do the COW without a second fault */
 491                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 492         }
 493
 494         spin_unlock(&mm->page_table_lock);
 495         unlock_page(page);
 496 out:
 497         return ret;
 498
 499 backout:
 500         spin_unlock(&mm->page_table_lock);
 501         hugetlb_put_quota(mapping);
 502         unlock_page(page);
 503         put_page(page);
 504         goto out;
 505 }
 506
 507 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 508                         unsigned long address, int write_access)
 509 {
 510         pte_t *ptep;
 511         pte_t entry;
 512         int ret;
 513
 514         ptep = huge_pte_alloc(mm, address);
 515         if (!ptep)
 516                 return VM_FAULT_OOM;
 517
 518         entry = *ptep;
 519         if (pte_none(entry))
 520                 return hugetlb_no_page(mm, vma, address, ptep, write_access);
 521
 522         ret = VM_FAULT_MINOR;
 523
 524         spin_lock(&mm->page_table_lock);
 525         /* Check for a racing update before calling hugetlb_cow */
 526         if (likely(pte_same(entry, *ptep)))
 527                 if (write_access && !pte_write(entry))
 528                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 529         spin_unlock(&mm->page_table_lock);
 530
 531         return ret;
 532 }
 533
 534 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 535                         struct page **pages, struct vm_area_struct **vmas,
 536                         unsigned long *position, int *length, int i)
 537 {
 538         unsigned long vpfn, vaddr = *position;
 539         int remainder = *length;
 540
 541         vpfn = vaddr/PAGE_SIZE;
 542         spin_lock(&mm->page_table_lock);
 543         while (vaddr < vma->vm_end && remainder) {
 544                 pte_t *pte;
 545                 struct page *page;
 546
 547                 /*
 548                  * Some archs (sparc64, sh*) have multiple pte_ts to
 549                  * each hugepage.  We have to make * sure we get the
 550                  * first, for the page indexing below to work.
 551                  */
 552                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 553
 554                 if (!pte || pte_none(*pte)) {
 555                         int ret;
 556
 557                         spin_unlock(&mm->page_table_lock);
 558                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 559                         spin_lock(&mm->page_table_lock);
 560                         if (ret == VM_FAULT_MINOR)
 561                                 continue;
 562
 563                         remainder = 0;
 564                         if (!i)
 565                                 i = -EFAULT;
 566                         break;
 567                 }
 568
 569                 if (pages) {
 570                         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 571                         get_page(page);
 572                         pages[i] = page;
 573                 }
 574
 575                 if (vmas)
 576                         vmas[i] = vma;
 577
 578                 vaddr += PAGE_SIZE;
 579                 ++vpfn;
 580                 --remainder;
 581                 ++i;
 582         }
 583         spin_unlock(&mm->page_table_lock);
 584         *length = remainder;
 585         *position = vaddr;
 586
 587         return i;
 588 }