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