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