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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 <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 #include "internal.h"
  22
  23 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
  24 static unsigned long nr_huge_pages, free_huge_pages;
  25 unsigned long max_huge_pages;
  26 static struct list_head hugepage_freelists[MAX_NUMNODES];
  27 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
  28 static unsigned int free_huge_pages_node[MAX_NUMNODES];
  29
  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 enqueue_huge_page(struct page *page)
  36 {
  37         int nid = page_to_nid(page);
  38         list_add(&page->lru, &hugepage_freelists[nid]);
  39         free_huge_pages++;
  40         free_huge_pages_node[nid]++;
  41 }
  42
  43 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
  44                                 unsigned long address)
  45 {
  46         int nid = numa_node_id();
  47         struct page *page = NULL;
  48         struct zonelist *zonelist = huge_zonelist(vma, address);
  49         struct zone **z;
  50
  51         for (z = zonelist->zones; *z; z++) {
  52                 nid = (*z)->zone_pgdat->node_id;
  53                 if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
  54                     !list_empty(&hugepage_freelists[nid]))
  55                         break;
  56         }
  57
  58         if (*z) {
  59                 page = list_entry(hugepage_freelists[nid].next,
  60                                   struct page, lru);
  61                 list_del(&page->lru);
  62                 free_huge_pages--;
  63                 free_huge_pages_node[nid]--;
  64         }
  65         return page;
  66 }
  67
  68 static int alloc_fresh_huge_page(void)
  69 {
  70         static int nid = 0;
  71         struct page *page;
  72         page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
  73                                         HUGETLB_PAGE_ORDER);
  74         nid = (nid + 1) % num_online_nodes();
  75         if (page) {
  76                 page[1].lru.next = (void *)free_huge_page;      /* dtor */
  77                 spin_lock(&hugetlb_lock);
  78                 nr_huge_pages++;
  79                 nr_huge_pages_node[page_to_nid(page)]++;
  80                 spin_unlock(&hugetlb_lock);
  81                 put_page(page); /* free it into the hugepage allocator */
  82                 return 1;
  83         }
  84         return 0;
  85 }
  86
  87 void free_huge_page(struct page *page)
  88 {
  89         BUG_ON(page_count(page));
  90
  91         INIT_LIST_HEAD(&page->lru);
  92
  93         spin_lock(&hugetlb_lock);
  94         enqueue_huge_page(page);
  95         spin_unlock(&hugetlb_lock);
  96 }
  97
  98 struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr)
  99 {
 100         struct page *page;
 101         int i;
 102
 103         spin_lock(&hugetlb_lock);
 104         page = dequeue_huge_page(vma, addr);
 105         if (!page) {
 106                 spin_unlock(&hugetlb_lock);
 107                 return NULL;
 108         }
 109         spin_unlock(&hugetlb_lock);
 110         set_page_refcounted(page);
 111         for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
 112                 clear_user_highpage(&page[i], addr);
 113         return page;
 114 }
 115
 116 static int __init hugetlb_init(void)
 117 {
 118         unsigned long i;
 119
 120         if (HPAGE_SHIFT == 0)
 121                 return 0;
 122
 123         for (i = 0; i < MAX_NUMNODES; ++i)
 124                 INIT_LIST_HEAD(&hugepage_freelists[i]);
 125
 126         for (i = 0; i < max_huge_pages; ++i) {
 127                 if (!alloc_fresh_huge_page())
 128                         break;
 129         }
 130         max_huge_pages = free_huge_pages = nr_huge_pages = i;
 131         printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
 132         return 0;
 133 }
 134 module_init(hugetlb_init);
 135
 136 static int __init hugetlb_setup(char *s)
 137 {
 138         if (sscanf(s, "%lu", &max_huge_pages) <= 0)
 139                 max_huge_pages = 0;
 140         return 1;
 141 }
 142 __setup("hugepages=", hugetlb_setup);
 143
 144 #ifdef CONFIG_SYSCTL
 145 static void update_and_free_page(struct page *page)
 146 {
 147         int i;
 148         nr_huge_pages--;
 149         nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
 150         for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 151                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 152                                 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
 153                                 1 << PG_private | 1<< PG_writeback);
 154         }
 155         page[1].lru.next = NULL;
 156         set_page_refcounted(page);
 157         __free_pages(page, HUGETLB_PAGE_ORDER);
 158 }
 159
 160 #ifdef CONFIG_HIGHMEM
 161 static void try_to_free_low(unsigned long count)
 162 {
 163         int i, nid;
 164         for (i = 0; i < MAX_NUMNODES; ++i) {
 165                 struct page *page, *next;
 166                 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
 167                         if (PageHighMem(page))
 168                                 continue;
 169                         list_del(&page->lru);
 170                         update_and_free_page(page);
 171                         nid = page_zone(page)->zone_pgdat->node_id;
 172                         free_huge_pages--;
 173                         free_huge_pages_node[nid]--;
 174                         if (count >= nr_huge_pages)
 175                                 return;
 176                 }
 177         }
 178 }
 179 #else
 180 static inline void try_to_free_low(unsigned long count)
 181 {
 182 }
 183 #endif
 184
 185 static unsigned long set_max_huge_pages(unsigned long count)
 186 {
 187         while (count > nr_huge_pages) {
 188                 if (!alloc_fresh_huge_page())
 189                         return nr_huge_pages;
 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(NULL, 0);
 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 int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 367                         unsigned long address, pte_t *ptep, pte_t pte)
 368 {
 369         struct page *old_page, *new_page;
 370         int i, avoidcopy;
 371
 372         old_page = pte_page(pte);
 373
 374         /* If no-one else is actually using this page, avoid the copy
 375          * and just make the page writable */
 376         avoidcopy = (page_count(old_page) == 1);
 377         if (avoidcopy) {
 378                 set_huge_ptep_writable(vma, address, ptep);
 379                 return VM_FAULT_MINOR;
 380         }
 381
 382         page_cache_get(old_page);
 383         new_page = alloc_huge_page(vma, address);
 384
 385         if (!new_page) {
 386                 page_cache_release(old_page);
 387                 return VM_FAULT_OOM;
 388         }
 389
 390         spin_unlock(&mm->page_table_lock);
 391         for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++)
 392                 copy_user_highpage(new_page + i, old_page + i,
 393                                    address + i*PAGE_SIZE);
 394         spin_lock(&mm->page_table_lock);
 395
 396         ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 397         if (likely(pte_same(*ptep, pte))) {
 398                 /* Break COW */
 399                 set_huge_pte_at(mm, address, ptep,
 400                                 make_huge_pte(vma, new_page, 1));
 401                 /* Make the old page be freed below */
 402                 new_page = old_page;
 403         }
 404         page_cache_release(new_page);
 405         page_cache_release(old_page);
 406         return VM_FAULT_MINOR;
 407 }
 408
 409 int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 410                         unsigned long address, pte_t *ptep, int write_access)
 411 {
 412         int ret = VM_FAULT_SIGBUS;
 413         unsigned long idx;
 414         unsigned long size;
 415         struct page *page;
 416         struct address_space *mapping;
 417         pte_t new_pte;
 418
 419         mapping = vma->vm_file->f_mapping;
 420         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
 421                 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 422
 423         /*
 424          * Use page lock to guard against racing truncation
 425          * before we get page_table_lock.
 426          */
 427 retry:
 428         page = find_lock_page(mapping, idx);
 429         if (!page) {
 430                 if (hugetlb_get_quota(mapping))
 431                         goto out;
 432                 page = alloc_huge_page(vma, address);
 433                 if (!page) {
 434                         hugetlb_put_quota(mapping);
 435                         ret = VM_FAULT_OOM;
 436                         goto out;
 437                 }
 438
 439                 if (vma->vm_flags & VM_SHARED) {
 440                         int err;
 441
 442                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
 443                         if (err) {
 444                                 put_page(page);
 445                                 hugetlb_put_quota(mapping);
 446                                 if (err == -EEXIST)
 447                                         goto retry;
 448                                 goto out;
 449                         }
 450                 } else
 451                         lock_page(page);
 452         }
 453
 454         spin_lock(&mm->page_table_lock);
 455         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
 456         if (idx >= size)
 457                 goto backout;
 458
 459         ret = VM_FAULT_MINOR;
 460         if (!pte_none(*ptep))
 461                 goto backout;
 462
 463         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
 464         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 465                                 && (vma->vm_flags & VM_SHARED)));
 466         set_huge_pte_at(mm, address, ptep, new_pte);
 467
 468         if (write_access && !(vma->vm_flags & VM_SHARED)) {
 469                 /* Optimization, do the COW without a second fault */
 470                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
 471         }
 472
 473         spin_unlock(&mm->page_table_lock);
 474         unlock_page(page);
 475 out:
 476         return ret;
 477
 478 backout:
 479         spin_unlock(&mm->page_table_lock);
 480         hugetlb_put_quota(mapping);
 481         unlock_page(page);
 482         put_page(page);
 483         goto out;
 484 }
 485
 486 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 487                         unsigned long address, int write_access)
 488 {
 489         pte_t *ptep;
 490         pte_t entry;
 491         int ret;
 492
 493         ptep = huge_pte_alloc(mm, address);
 494         if (!ptep)
 495                 return VM_FAULT_OOM;
 496
 497         entry = *ptep;
 498         if (pte_none(entry))
 499                 return hugetlb_no_page(mm, vma, address, ptep, write_access);
 500
 501         ret = VM_FAULT_MINOR;
 502
 503         spin_lock(&mm->page_table_lock);
 504         /* Check for a racing update before calling hugetlb_cow */
 505         if (likely(pte_same(entry, *ptep)))
 506                 if (write_access && !pte_write(entry))
 507                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
 508         spin_unlock(&mm->page_table_lock);
 509
 510         return ret;
 511 }
 512
 513 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 514                         struct page **pages, struct vm_area_struct **vmas,
 515                         unsigned long *position, int *length, int i)
 516 {
 517         unsigned long vpfn, vaddr = *position;
 518         int remainder = *length;
 519
 520         vpfn = vaddr/PAGE_SIZE;
 521         spin_lock(&mm->page_table_lock);
 522         while (vaddr < vma->vm_end && remainder) {
 523                 pte_t *pte;
 524                 struct page *page;
 525
 526                 /*
 527                  * Some archs (sparc64, sh*) have multiple pte_ts to
 528                  * each hugepage.  We have to make * sure we get the
 529                  * first, for the page indexing below to work.
 530                  */
 531                 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
 532
 533                 if (!pte || pte_none(*pte)) {
 534                         int ret;
 535
 536                         spin_unlock(&mm->page_table_lock);
 537                         ret = hugetlb_fault(mm, vma, vaddr, 0);
 538                         spin_lock(&mm->page_table_lock);
 539                         if (ret == VM_FAULT_MINOR)
 540                                 continue;
 541
 542                         remainder = 0;
 543                         if (!i)
 544                                 i = -EFAULT;
 545                         break;
 546                 }
 547
 548                 if (pages) {
 549                         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 550                         get_page(page);
 551                         pages[i] = page;
 552                 }
 553
 554                 if (vmas)
 555                         vmas[i] = vma;
 556
 557                 vaddr += PAGE_SIZE;
 558                 ++vpfn;
 559                 --remainder;
 560                 ++i;
 561         }
 562         spin_unlock(&mm->page_table_lock);
 563         *length = remainder;
 564         *position = vaddr;
 565
 566         return i;
 567 }