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