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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 <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         struct zonelist *zonelist = NODE_DATA(nid)->node_zonelists;
  44         struct zone **z;
  45
  46         for (z = zonelist->zones; *z; z++) {
  47                 nid = (*z)->zone_pgdat->node_id;
  48                 if (!list_empty(&hugepage_freelists[nid]))
  49                         break;
  50         }
  51
  52         if (*z) {
  53                 page = list_entry(hugepage_freelists[nid].next,
  54                                   struct page, lru);
  55                 list_del(&page->lru);
  56                 free_huge_pages--;
  57                 free_huge_pages_node[nid]--;
  58         }
  59         return page;
  60 }
  61
  62 static struct page *alloc_fresh_huge_page(void)
  63 {
  64         static int nid = 0;
  65         struct page *page;
  66         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
  67                                         HUGETLB_PAGE_ORDER);
  68         nid = (nid + 1) % num_online_nodes();
  69         if (page) {
  70                 spin_lock(&hugetlb_lock);
  71                 nr_huge_pages++;
  72                 nr_huge_pages_node[page_to_nid(page)]++;
  73                 spin_unlock(&hugetlb_lock);
  74         }
  75         return page;
  76 }
  77
  78 void free_huge_page(struct page *page)
  79 {
  80         BUG_ON(page_count(page));
  81
  82         INIT_LIST_HEAD(&page->lru);
  83         page[1].mapping = NULL;
  84
  85         spin_lock(&hugetlb_lock);
  86         enqueue_huge_page(page);
  87         spin_unlock(&hugetlb_lock);
  88 }
  89
  90 struct page *alloc_huge_page(void)
  91 {
  92         struct page *page;
  93         int i;
  94
  95         spin_lock(&hugetlb_lock);
  96         page = dequeue_huge_page();
  97         if (!page) {
  98                 spin_unlock(&hugetlb_lock);
  99                 return NULL;
 100         }
 101         spin_unlock(&hugetlb_lock);
 102         set_page_count(page, 1);
 103         page[1].mapping = (void *)free_huge_page;
 104         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
 105                 clear_highpage(&page[i]);
 106         return page;
 107 }
 108
 109 static int __init hugetlb_init(void)
 110 {
 111         unsigned long i;
 112         struct page *page;
 113
 114         if (HPAGE_SHIFT == 0)
 115                 return 0;
 116
 117         for (i = 0; i < MAX_NUMNODES; ++i)
 118                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 119
 120         for (i = 0; i < max_huge_pages; ++i) {
 121                 page = alloc_fresh_huge_page();
 122                 if (!page)
 123                         break;
 124                 spin_lock(&hugetlb_lock);
 125                 enqueue_huge_page(page);
 126                 spin_unlock(&hugetlb_lock);
 127         }
 128         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 129         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 130         return 0;
 131 }
 132 module_init(hugetlb_init);
 133
 134 static int __init hugetlb_setup(char *s)
 135 {
 136         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 137                 max_huge_pages = 0;
 138         return 1;
 139 }
 140 __setup("hugepages=", hugetlb_setup);
 141
 142 #ifdef CONFIG_SYSCTL
 143 static void update_and_free_page(struct page *page)
 144 {
 145         int i;
 146         nr_huge_pages--;
 147         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 148         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 149                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 150                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 151                                 1 << PG_private | 1<< PG_writeback);
 152                 set_page_count(&page[i], 0);
 153         }
 154         set_page_count(page, 1);
 155         __free_pages(page, HUGETLB_PAGE_ORDER);
 156 }
 157
 158 #ifdef CONFIG_HIGHMEM
 159 static void try_to_free_low(unsigned long count)
 160 {
 161         int i, nid;
 162         for (i = 0; i < MAX_NUMNODES; ++i) {
 163                 struct page *page, *next;
 164                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 165                         if (PageHighMem(page))
 166                                 continue;
 167                         list_del(&page->lru);
 168                         update_and_free_page(page);
 169                         nid = page_zone(page)->zone_pgdat->node_id;
 170                         free_huge_pages--;
 171                         free_huge_pages_node[nid]--;
 172                         if (count >= nr_huge_pages)
 173                                 return;
 174                 }
 175         }
 176 }
 177 #else
 178 static inline void try_to_free_low(unsigned long count)
 179 {
 180 }
 181 #endif
 182
 183 static unsigned long set_max_huge_pages(unsigned long count)
 184 {
 185         while (count > nr_huge_pages) {
 186                 struct page *page = alloc_fresh_huge_page();
 187                 if (!page)
 188                         return nr_huge_pages;
 189                 spin_lock(&hugetlb_lock);
 190                 enqueue_huge_page(page);
 191                 spin_unlock(&hugetlb_lock);
 192         }
 193         if (count >= nr_huge_pages)
 194                 return nr_huge_pages;
 195
 196         spin_lock(&hugetlb_lock);
 197         try_to_free_low(count);
 198         while (count < nr_huge_pages) {
 199                 struct page *page = dequeue_huge_page();
 200                 if (!page)
 201                         break;
 202                 update_and_free_page(page);
 203         }
 204         spin_unlock(&hugetlb_lock);
 205         return nr_huge_pages;
 206 }
 207
 208 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 209                            struct file *file, void __user *buffer,
 210                            size_t *length, loff_t *ppos)
 211 {
 212         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 213         max_huge_pages = set_max_huge_pages(max_huge_pages);
 214         return 0;
 215 }
 216 #endif /* CONFIG_SYSCTL */
 217
 218 int hugetlb_report_meminfo(char *buf)
 219 {
 220         return sprintf(buf,
 221                         "HugePages_Total: %5lu\n"
 222                         "HugePages_Free:  %5lu\n"
 223                         "Hugepagesize:    %5lu kB\n",
 224                         nr_huge_pages,
 225                         free_huge_pages,
 226                         HPAGE_SIZE/1024);
 227 }
 228
 229 int hugetlb_report_node_meminfo(int nid, char *buf)
 230 {
 231         return sprintf(buf,
 232                 "Node %d HugePages_Total: %5u\n"
 233                 "Node %d HugePages_Free:  %5u\n",
 234                 nid, nr_huge_pages_node[nid],
 235                 nid, free_huge_pages_node[nid]);
 236 }
 237
 238 int is_hugepage_mem_enough(size_t size)
 239 {
 240         return (size + ~HPAGE_MASK)/HPAGE_SIZE <= free_huge_pages;
 241 }
 242
 243 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 244 unsigned long hugetlb_total_pages(void)
 245 {
 246         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 247 }
 248
 249 /*
 250  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 251  * handle_mm_fault() to try to instantiate regular-sized pages in the
 252  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 253  * this far.
 254  */
 255 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 256                                 unsigned long address, int *unused)
 257 {
 258         BUG();
 259         return NULL;
 260 }
 261
 262 struct vm_operations_struct hugetlb_vm_ops = {
 263         .nopage = hugetlb_nopage,
 264 };
 265
 266 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 267                                 int writable)
 268 {
 269         pte_t entry;
 270
 271         if (writable) {
 272                 entry =
 273                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 274         } else {
 275                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 276         }
 277         entry = pte_mkyoung(entry);
 278         entry = pte_mkhuge(entry);
 279
 280         return entry;
 281 }
 282
 283 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 284                                    unsigned long address, pte_t *ptep)
 285 {
 286         pte_t entry;
 287
 288         entry = pte_mkwrite(pte_mkdirty(*ptep));
 289         ptep_set_access_flags(vma, address, ptep, entry, 1);
 290         update_mmu_cache(vma, address, entry);
 291         lazy_mmu_prot_update(entry);
 292 }
 293
 294
 295 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 296                             struct vm_area_struct *vma)
 297 {
 298         pte_t *src_pte, *dst_pte, entry;
 299         struct page *ptepage;
 300         unsigned long addr;
 301         int cow;
 302
 303         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 304
 305         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 306                 src_pte = huge_pte_offset(src, addr);
 307                 if (!src_pte)
 308                         continue;
 309                 dst_pte = huge_pte_alloc(dst, addr);
 310                 if (!dst_pte)
 311                         goto nomem;
 312                 spin_lock(&dst->page_table_lock);
 313                 spin_lock(&src->page_table_lock);
 314                 if (!pte_none(*src_pte)) {
 315                         if (cow)
 316                                 ptep_set_wrprotect(src, addr, src_pte);
 317                         entry = *src_pte;
 318                         ptepage = pte_page(entry);
 319                         get_page(ptepage);
 320                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 321                         set_huge_pte_at(dst, addr, dst_pte, entry);
 322                 }
 323                 spin_unlock(&src->page_table_lock);
 324                 spin_unlock(&dst->page_table_lock);
 325         }
 326         return 0;
 327
 328 nomem:
 329         return -ENOMEM;
 330 }
 331
 332 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 333                           unsigned long end)
 334 {
 335         struct mm_struct *mm = vma->vm_mm;
 336         unsigned long address;
 337         pte_t *ptep;
 338         pte_t pte;
 339         struct page *page;
 340
 341         WARN_ON(!is_vm_hugetlb_page(vma));
 342         BUG_ON(start & ~HPAGE_MASK);
 343         BUG_ON(end & ~HPAGE_MASK);
 344
 345         spin_lock(&mm->page_table_lock);
 346
 347         /* Update high watermark before we lower rss */
 348         update_hiwater_rss(mm);
 349
 350         for (address = start; address < end; address += HPAGE_SIZE) {
 351                 ptep = huge_pte_offset(mm, address);
 352                 if (!ptep)
 353                         continue;
 354
 355                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 356                 if (pte_none(pte))
 357                         continue;
 358
 359                 page = pte_page(pte);
 360                 put_page(page);
 361                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 362         }
 363
 364         spin_unlock(&mm->page_table_lock);
 365         flush_tlb_range(vma, start, end);
 366 }
 367
 368 static struct page *find_or_alloc_huge_page(struct address_space *mapping,
 369                                 unsigned long idx, int shared)
 370 {
 371         struct page *page;
 372         int err;
 373
 374 retry:
 375         page = find_lock_page(mapping, idx);
 376         if (page)
 377                 goto out;
 378
 379         if (hugetlb_get_quota(mapping))
 380                 goto out;
 381         page = alloc_huge_page();
 382         if (!page) {
 383                 hugetlb_put_quota(mapping);
 384                 goto out;
 385         }
 386
 387         if (shared) {
 388                 err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 389                 if (err) {
 390                         put_page(page);
 391                         hugetlb_put_quota(mapping);
 392                         if (err == -EEXIST)
 393                                 goto retry;
 394                         page = NULL;
 395                 }
 396         } else {
 397                 /* Caller expects a locked page */
 398                 lock_page(page);
 399         }
 400 out:
 401         return page;
 402 }
 403
 404 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 405                         unsigned long address, pte_t *ptep, pte_t pte)
 406 {
 407         struct page *old_page, *new_page;
 408         int i, avoidcopy;
 409
 410         old_page = pte_page(pte);
 411
 412         /* If no-one else is actually using this page, avoid the copy
 413          * and just make the page writable */
 414         avoidcopy = (page_count(old_page) == 1);
 415         if (avoidcopy) {
 416                 set_huge_ptep_writable(vma, address, ptep);
 417                 return VM_FAULT_MINOR;
 418         }
 419
 420         page_cache_get(old_page);
 421         new_page = alloc_huge_page();
 422
 423         if (!new_page) {
 424                 page_cache_release(old_page);
 425
 426                 /* Logically this is OOM, not a SIGBUS, but an OOM
 427                  * could cause the kernel to go killing other
 428                  * processes which won't help the hugepage situation
 429                  * at all (?) */
 430                 return VM_FAULT_SIGBUS;
 431         }
 432
 433         spin_unlock(&mm->page_table_lock);
 434         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++)
 435                 copy_user_highpage(new_page + i, old_page + i,
 436                                    address + i*PAGE_SIZE);
 437         spin_lock(&mm->page_table_lock);
 438
 439         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 440         if (likely(pte_same(*ptep, pte))) {
 441                 /* Break COW */
 442                 set_huge_pte_at(mm, address, ptep,
 443                                 make_huge_pte(vma, new_page, 1));
 444                 /* Make the old page be freed below */
 445                 new_page = old_page;
 446         }
 447         page_cache_release(new_page);
 448         page_cache_release(old_page);
 449         return VM_FAULT_MINOR;
 450 }
 451
 452 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 453                         unsigned long address, pte_t *ptep, int write_access)
 454 {
 455         int ret = VM_FAULT_SIGBUS;
 456         unsigned long idx;
 457         unsigned long size;
 458         struct page *page;
 459         struct address_space *mapping;
 460         pte_t new_pte;
 461
 462         mapping = vma->vm_file->f_mapping;
 463         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 464                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 465
 466         /*
 467          * Use page lock to guard against racing truncation
 468          * before we get page_table_lock.
 469          */
 470         page = find_or_alloc_huge_page(mapping, idx,
 471                         vma->vm_flags & VM_SHARED);
 472         if (!page)
 473                 goto out;
 474
 475         BUG_ON(!PageLocked(page));
 476
 477         spin_lock(&mm->page_table_lock);
 478         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 479         if (idx >= size)
 480                 goto backout;
 481
 482         ret = VM_FAULT_MINOR;
 483         if (!pte_none(*ptep))
 484                 goto backout;
 485
 486         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 487         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 488                                 && (vma->vm_flags & VM_SHARED)));
 489         set_huge_pte_at(mm, address, ptep, new_pte);
 490
 491         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 492                 /* Optimization, do the COW without a second fault */
 493                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 494         }
 495
 496         spin_unlock(&mm->page_table_lock);
 497         unlock_page(page);
 498 out:
 499         return ret;
 500
 501 backout:
 502         spin_unlock(&mm->page_table_lock);
 503         hugetlb_put_quota(mapping);
 504         unlock_page(page);
 505         put_page(page);
 506         goto out;
 507 }
 508
 509 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 510                         unsigned long address, int write_access)
 511 {
 512         pte_t *ptep;
 513         pte_t entry;
 514         int ret;
 515
 516         ptep = huge_pte_alloc(mm, address);
 517         if (!ptep)
 518                 return VM_FAULT_OOM;
 519
 520         entry = *ptep;
 521         if (pte_none(entry))
 522                 return hugetlb_no_page(mm, vma, address, ptep, write_access);
 523
 524         ret = VM_FAULT_MINOR;
 525
 526         spin_lock(&mm->page_table_lock);
 527         /* Check for a racing update before calling hugetlb_cow */
 528         if (likely(pte_same(entry, *ptep)))
 529                 if (write_access && !pte_write(entry))
 530                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 531         spin_unlock(&mm->page_table_lock);
 532
 533         return ret;
 534 }
 535
 536 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 537                         struct page **pages, struct vm_area_struct **vmas,
 538                         unsigned long *position, int *length, int i)
 539 {
 540         unsigned long vpfn, vaddr = *position;
 541         int remainder = *length;
 542
 543         vpfn = vaddr/PAGE_SIZE;
 544         spin_lock(&mm->page_table_lock);
 545         while (vaddr < vma->vm_end && remainder) {
 546                 pte_t *pte;
 547                 struct page *page;
 548
 549                 /*
 550                  * Some archs (sparc64, sh*) have multiple pte_ts to
 551                  * each hugepage.  We have to make * sure we get the
 552                  * first, for the page indexing below to work.
 553                  */
 554                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 555
 556                 if (!pte || pte_none(*pte)) {
 557                         int ret;
 558
 559                         spin_unlock(&mm->page_table_lock);
 560                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 561                         spin_lock(&mm->page_table_lock);
 562                         if (ret == VM_FAULT_MINOR)
 563                                 continue;
 564
 565                         remainder = 0;
 566                         if (!i)
 567                                 i = -EFAULT;
 568                         break;
 569                 }
 570
 571                 if (pages) {
 572                         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 573                         get_page(page);
 574                         pages[i] = page;
 575                 }
 576
 577                 if (vmas)
 578                         vmas[i] = vma;
 579
 580                 vaddr += PAGE_SIZE;
 581                 ++vpfn;
 582                 --remainder;
 583                 ++i;
 584         }
 585         spin_unlock(&mm->page_table_lock);
 586         *length = remainder;
 587         *position = vaddr;
 588
 589         return i;
 590 }