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;
  26 unsigned long max_huge_pages;
  27 static struct list_head hugepage_freelists[MAX_NUMNODES];
  28 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  29 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  30 /*
  31  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  32  */
  33 static DEFINE_SPINLOCK(hugetlb_lock);
  34
  35 static void clear_huge_page(struct page *page, unsigned long addr)
  36 {
  37         int i;
  38
  39         might_sleep();
  40         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
  41                 cond_resched();
  42                 clear_user_highpage(page + i, addr);
  43         }
  44 }
  45
  46 static void copy_huge_page(struct page *dst, struct page *src,
  47                            unsigned long addr)
  48 {
  49         int i;
  50
  51         might_sleep();
  52         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
  53                 cond_resched();
  54                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE);
  55         }
  56 }
  57
  58 static void enqueue_huge_page(struct page *page)
  59 {
  60         int nid = page_to_nid(page);
  61         list_add(&page->lru, &hugepage_freelists[nid]);
  62         free_huge_pages++;
  63         free_huge_pages_node[nid]++;
  64 }
  65
  66 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  67                                 unsigned long address)
  68 {
  69         int nid = numa_node_id();
  70         struct page *page = NULL;
  71         struct zonelist *zonelist = huge_zonelist(vma, address);
  72         struct zone **z;
  73
  74         for (z = zonelist->zones; *z; z++) {
  75                 nid = (*z)->zone_pgdat->node_id;
  76                 if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
  77                     !list_empty(&hugepage_freelists[nid]))
  78                         break;
  79         }
  80
  81         if (*z) {
  82                 page = list_entry(hugepage_freelists[nid].next,
  83                                   struct page, lru);
  84                 list_del(&page->lru);
  85                 free_huge_pages--;
  86                 free_huge_pages_node[nid]--;
  87         }
  88         return page;
  89 }
  90
  91 static int alloc_fresh_huge_page(void)
  92 {
  93         static int nid = 0;
  94         struct page *page;
  95         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
  96                                         HUGETLB_PAGE_ORDER);
  97         nid = (nid + 1) % num_online_nodes();
  98         if (page) {
  99                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
 100                 spin_lock(&hugetlb_lock);
 101                 nr_huge_pages++;
 102                 nr_huge_pages_node[page_to_nid(page)]++;
 103                 spin_unlock(&hugetlb_lock);
 104                 put_page(page); /* free it into the hugepage allocator */
 105                 return 1;
 106         }
 107         return 0;
 108 }
 109
 110 void free_huge_page(struct page *page)
 111 {
 112         BUG_ON(page_count(page));
 113
 114         INIT_LIST_HEAD(&page->lru);
 115
 116         spin_lock(&hugetlb_lock);
 117         enqueue_huge_page(page);
 118         spin_unlock(&hugetlb_lock);
 119 }
 120
 121 struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr)
 122 {
 123         struct page *page;
 124
 125         spin_lock(&hugetlb_lock);
 126         page = dequeue_huge_page(vma, addr);
 127         if (!page) {
 128                 spin_unlock(&hugetlb_lock);
 129                 return NULL;
 130         }
 131         spin_unlock(&hugetlb_lock);
 132         set_page_refcounted(page);
 133         return page;
 134 }
 135
 136 static int __init hugetlb_init(void)
 137 {
 138         unsigned long i;
 139
 140         if (HPAGE_SHIFT == 0)
 141                 return 0;
 142
 143         for (i = 0; i < MAX_NUMNODES; ++i)
 144                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 145
 146         for (i = 0; i < max_huge_pages; ++i) {
 147                 if (!alloc_fresh_huge_page())
 148                         break;
 149         }
 150         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 151         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 152         return 0;
 153 }
 154 module_init(hugetlb_init);
 155
 156 static int __init hugetlb_setup(char *s)
 157 {
 158         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 159                 max_huge_pages = 0;
 160         return 1;
 161 }
 162 __setup("hugepages=", hugetlb_setup);
 163
 164 #ifdef CONFIG_SYSCTL
 165 static void update_and_free_page(struct page *page)
 166 {
 167         int i;
 168         nr_huge_pages--;
 169         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 170         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 171                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 172                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 173                                 1 << PG_private | 1<< PG_writeback);
 174         }
 175         page[1].lru.next = NULL;
 176         set_page_refcounted(page);
 177         __free_pages(page, HUGETLB_PAGE_ORDER);
 178 }
 179
 180 #ifdef CONFIG_HIGHMEM
 181 static void try_to_free_low(unsigned long count)
 182 {
 183         int i, nid;
 184         for (i = 0; i < MAX_NUMNODES; ++i) {
 185                 struct page *page, *next;
 186                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 187                         if (PageHighMem(page))
 188                                 continue;
 189                         list_del(&page->lru);
 190                         update_and_free_page(page);
 191                         nid = page_zone(page)->zone_pgdat->node_id;
 192                         free_huge_pages--;
 193                         free_huge_pages_node[nid]--;
 194                         if (count >= nr_huge_pages)
 195                                 return;
 196                 }
 197         }
 198 }
 199 #else
 200 static inline void try_to_free_low(unsigned long count)
 201 {
 202 }
 203 #endif
 204
 205 static unsigned long set_max_huge_pages(unsigned long count)
 206 {
 207         while (count > nr_huge_pages) {
 208                 if (!alloc_fresh_huge_page())
 209                         return nr_huge_pages;
 210         }
 211         if (count >= nr_huge_pages)
 212                 return nr_huge_pages;
 213
 214         spin_lock(&hugetlb_lock);
 215         try_to_free_low(count);
 216         while (count < nr_huge_pages) {
 217                 struct page *page = dequeue_huge_page(NULL, 0);
 218                 if (!page)
 219                         break;
 220                 update_and_free_page(page);
 221         }
 222         spin_unlock(&hugetlb_lock);
 223         return nr_huge_pages;
 224 }
 225
 226 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 227                            struct file *file, void __user *buffer,
 228                            size_t *length, loff_t *ppos)
 229 {
 230         proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
 231         max_huge_pages = set_max_huge_pages(max_huge_pages);
 232         return 0;
 233 }
 234 #endif /* CONFIG_SYSCTL */
 235
 236 int hugetlb_report_meminfo(char *buf)
 237 {
 238         return sprintf(buf,
 239                         "HugePages_Total: %5lu\n"
 240                         "HugePages_Free:  %5lu\n"
 241                         "Hugepagesize:    %5lu kB\n",
 242                         nr_huge_pages,
 243                         free_huge_pages,
 244                         HPAGE_SIZE/1024);
 245 }
 246
 247 int hugetlb_report_node_meminfo(int nid, char *buf)
 248 {
 249         return sprintf(buf,
 250                 "Node %d HugePages_Total: %5u\n"
 251                 "Node %d HugePages_Free:  %5u\n",
 252                 nid, nr_huge_pages_node[nid],
 253                 nid, free_huge_pages_node[nid]);
 254 }
 255
 256 int is_hugepage_mem_enough(size_t size)
 257 {
 258         return (size + ~HPAGE_MASK)/HPAGE_SIZE <= free_huge_pages;
 259 }
 260
 261 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 262 unsigned long hugetlb_total_pages(void)
 263 {
 264         return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
 265 }
 266
 267 /*
 268  * We cannot handle pagefaults against hugetlb pages at all.  They cause
 269  * handle_mm_fault() to try to instantiate regular-sized pages in the
 270  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 271  * this far.
 272  */
 273 static struct page *hugetlb_nopage(struct vm_area_struct *vma,
 274                                 unsigned long address, int *unused)
 275 {
 276         BUG();
 277         return NULL;
 278 }
 279
 280 struct vm_operations_struct hugetlb_vm_ops = {
 281         .nopage = hugetlb_nopage,
 282 };
 283
 284 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
 285                                 int writable)
 286 {
 287         pte_t entry;
 288
 289         if (writable) {
 290                 entry =
 291                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 292         } else {
 293                 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
 294         }
 295         entry = pte_mkyoung(entry);
 296         entry = pte_mkhuge(entry);
 297
 298         return entry;
 299 }
 300
 301 static void set_huge_ptep_writable(struct vm_area_struct *vma,
 302                                    unsigned long address, pte_t *ptep)
 303 {
 304         pte_t entry;
 305
 306         entry = pte_mkwrite(pte_mkdirty(*ptep));
 307         ptep_set_access_flags(vma, address, ptep, entry, 1);
 308         update_mmu_cache(vma, address, entry);
 309         lazy_mmu_prot_update(entry);
 310 }
 311
 312
 313 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 314                             struct vm_area_struct *vma)
 315 {
 316         pte_t *src_pte, *dst_pte, entry;
 317         struct page *ptepage;
 318         unsigned long addr;
 319         int cow;
 320
 321         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 322
 323         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
 324                 src_pte = huge_pte_offset(src, addr);
 325                 if (!src_pte)
 326                         continue;
 327                 dst_pte = huge_pte_alloc(dst, addr);
 328                 if (!dst_pte)
 329                         goto nomem;
 330                 spin_lock(&dst->page_table_lock);
 331                 spin_lock(&src->page_table_lock);
 332                 if (!pte_none(*src_pte)) {
 333                         if (cow)
 334                                 ptep_set_wrprotect(src, addr, src_pte);
 335                         entry = *src_pte;
 336                         ptepage = pte_page(entry);
 337                         get_page(ptepage);
 338                         add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
 339                         set_huge_pte_at(dst, addr, dst_pte, entry);
 340                 }
 341                 spin_unlock(&src->page_table_lock);
 342                 spin_unlock(&dst->page_table_lock);
 343         }
 344         return 0;
 345
 346 nomem:
 347         return -ENOMEM;
 348 }
 349
 350 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 351                           unsigned long end)
 352 {
 353         struct mm_struct *mm = vma->vm_mm;
 354         unsigned long address;
 355         pte_t *ptep;
 356         pte_t pte;
 357         struct page *page;
 358
 359         WARN_ON(!is_vm_hugetlb_page(vma));
 360         BUG_ON(start & ~HPAGE_MASK);
 361         BUG_ON(end & ~HPAGE_MASK);
 362
 363         spin_lock(&mm->page_table_lock);
 364
 365         /* Update high watermark before we lower rss */
 366         update_hiwater_rss(mm);
 367
 368         for (address = start; address < end; address += HPAGE_SIZE) {
 369                 ptep = huge_pte_offset(mm, address);
 370                 if (!ptep)
 371                         continue;
 372
 373                 pte = huge_ptep_get_and_clear(mm, address, ptep);
 374                 if (pte_none(pte))
 375                         continue;
 376
 377                 page = pte_page(pte);
 378                 put_page(page);
 379                 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 380         }
 381
 382         spin_unlock(&mm->page_table_lock);
 383         flush_tlb_range(vma, start, end);
 384 }
 385
 386 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 387                         unsigned long address, pte_t *ptep, pte_t pte)
 388 {
 389         struct page *old_page, *new_page;
 390         int avoidcopy;
 391
 392         old_page = pte_page(pte);
 393
 394         /* If no-one else is actually using this page, avoid the copy
 395          * and just make the page writable */
 396         avoidcopy = (page_count(old_page) == 1);
 397         if (avoidcopy) {
 398                 set_huge_ptep_writable(vma, address, ptep);
 399                 return VM_FAULT_MINOR;
 400         }
 401
 402         page_cache_get(old_page);
 403         new_page = alloc_huge_page(vma, address);
 404
 405         if (!new_page) {
 406                 page_cache_release(old_page);
 407                 return VM_FAULT_OOM;
 408         }
 409
 410         spin_unlock(&mm->page_table_lock);
 411         copy_huge_page(new_page, old_page, address);
 412         spin_lock(&mm->page_table_lock);
 413
 414         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 415         if (likely(pte_same(*ptep, pte))) {
 416                 /* Break COW */
 417                 set_huge_pte_at(mm, address, ptep,
 418                                 make_huge_pte(vma, new_page, 1));
 419                 /* Make the old page be freed below */
 420                 new_page = old_page;
 421         }
 422         page_cache_release(new_page);
 423         page_cache_release(old_page);
 424         return VM_FAULT_MINOR;
 425 }
 426
 427 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 428                         unsigned long address, pte_t *ptep, int write_access)
 429 {
 430         int ret = VM_FAULT_SIGBUS;
 431         unsigned long idx;
 432         unsigned long size;
 433         struct page *page;
 434         struct address_space *mapping;
 435         pte_t new_pte;
 436
 437         mapping = vma->vm_file->f_mapping;
 438         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 439                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 440
 441         /*
 442          * Use page lock to guard against racing truncation
 443          * before we get page_table_lock.
 444          */
 445 retry:
 446         page = find_lock_page(mapping, idx);
 447         if (!page) {
 448                 if (hugetlb_get_quota(mapping))
 449                         goto out;
 450                 page = alloc_huge_page(vma, address);
 451                 if (!page) {
 452                         hugetlb_put_quota(mapping);
 453                         ret = VM_FAULT_OOM;
 454                         goto out;
 455                 }
 456                 clear_huge_page(page, address);
 457
 458                 if (vma->vm_flags & VM_SHARED) {
 459                         int err;
 460
 461                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 462                         if (err) {
 463                                 put_page(page);
 464                                 hugetlb_put_quota(mapping);
 465                                 if (err == -EEXIST)
 466                                         goto retry;
 467                                 goto out;
 468                         }
 469                 } else
 470                         lock_page(page);
 471         }
 472
 473         spin_lock(&mm->page_table_lock);
 474         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 475         if (idx >= size)
 476                 goto backout;
 477
 478         ret = VM_FAULT_MINOR;
 479         if (!pte_none(*ptep))
 480                 goto backout;
 481
 482         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 483         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 484                                 && (vma->vm_flags & VM_SHARED)));
 485         set_huge_pte_at(mm, address, ptep, new_pte);
 486
 487         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 488                 /* Optimization, do the COW without a second fault */
 489                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 490         }
 491
 492         spin_unlock(&mm->page_table_lock);
 493         unlock_page(page);
 494 out:
 495         return ret;
 496
 497 backout:
 498         spin_unlock(&mm->page_table_lock);
 499         hugetlb_put_quota(mapping);
 500         unlock_page(page);
 501         put_page(page);
 502         goto out;
 503 }
 504
 505 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 506                         unsigned long address, int write_access)
 507 {
 508         pte_t *ptep;
 509         pte_t entry;
 510         int ret;
 511         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 512
 513         ptep = huge_pte_alloc(mm, address);
 514         if (!ptep)
 515                 return VM_FAULT_OOM;
 516
 517         /*
 518          * Serialize hugepage allocation and instantiation, so that we don't
 519          * get spurious allocation failures if two CPUs race to instantiate
 520          * the same page in the page cache.
 521          */
 522         mutex_lock(&hugetlb_instantiation_mutex);
 523         entry = *ptep;
 524         if (pte_none(entry)) {
 525                 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
 526                 mutex_unlock(&hugetlb_instantiation_mutex);
 527                 return ret;
 528         }
 529
 530         ret = VM_FAULT_MINOR;
 531
 532         spin_lock(&mm->page_table_lock);
 533         /* Check for a racing update before calling hugetlb_cow */
 534         if (likely(pte_same(entry, *ptep)))
 535                 if (write_access && !pte_write(entry))
 536                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 537         spin_unlock(&mm->page_table_lock);
 538         mutex_unlock(&hugetlb_instantiation_mutex);
 539
 540         return ret;
 541 }
 542
 543 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 544                         struct page **pages, struct vm_area_struct **vmas,
 545                         unsigned long *position, int *length, int i)
 546 {
 547         unsigned long vpfn, vaddr = *position;
 548         int remainder = *length;
 549
 550         vpfn = vaddr/PAGE_SIZE;
 551         spin_lock(&mm->page_table_lock);
 552         while (vaddr < vma->vm_end && remainder) {
 553                 pte_t *pte;
 554                 struct page *page;
 555
 556                 /*
 557                  * Some archs (sparc64, sh*) have multiple pte_ts to
 558                  * each hugepage.  We have to make * sure we get the
 559                  * first, for the page indexing below to work.
 560                  */
 561                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 562
 563                 if (!pte || pte_none(*pte)) {
 564                         int ret;
 565
 566                         spin_unlock(&mm->page_table_lock);
 567                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 568                         spin_lock(&mm->page_table_lock);
 569                         if (ret == VM_FAULT_MINOR)
 570                                 continue;
 571
 572                         remainder = 0;
 573                         if (!i)
 574                                 i = -EFAULT;
 575                         break;
 576                 }
 577
 578                 if (pages) {
 579                         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 580                         get_page(page);
 581                         pages[i] = page;
 582                 }
 583
 584                 if (vmas)
 585                         vmas[i] = vma;
 586
 587                 vaddr += PAGE_SIZE;
 588                 ++vpfn;
 589                 --remainder;
 590                 ++i;
 591         }
 592         spin_unlock(&mm->page_table_lock);
 593         *length = remainder;
 594         *position = vaddr;
 595
 596         return i;
 597 }
 598
 599 void hugetlb_change_protection(struct vm_area_struct *vma,
 600                 unsigned long address, unsigned long end, pgprot_t newprot)
 601 {
 602         struct mm_struct *mm = vma->vm_mm;
 603         unsigned long start = address;
 604         pte_t *ptep;
 605         pte_t pte;
 606
 607         BUG_ON(address >= end);
 608         flush_cache_range(vma, address, end);
 609
 610         spin_lock(&mm->page_table_lock);
 611         for (; address < end; address += HPAGE_SIZE) {
 612                 ptep = huge_pte_offset(mm, address);
 613                 if (!ptep)
 614                         continue;
 615                 if (!pte_none(*ptep)) {
 616                         pte = huge_ptep_get_and_clear(mm, address, ptep);
 617                         pte = pte_mkhuge(pte_modify(pte, newprot));
 618                         set_huge_pte_at(mm, address, ptep, pte);
 619                         lazy_mmu_prot_update(pte);
 620                 }
 621         }
 622         spin_unlock(&mm->page_table_lock);
 623
 624         flush_tlb_range(vma, start, end);
 625 }
 626