arch/x86/mm/hugetlbpage.c

   1 /*
   2  * IA-32 Huge TLB Page Support for Kernel.
   3  *
   4  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
   5  */
   6
   7 #include <linux/init.h>
   8 #include <linux/fs.h>
   9 #include <linux/mm.h>
  10 #include <linux/hugetlb.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/slab.h>
  13 #include <linux/err.h>
  14 #include <linux/sysctl.h>
  15 #include <asm/mman.h>
  16 #include <asm/tlb.h>
  17 #include <asm/tlbflush.h>
  18 #include <asm/pgalloc.h>
  19
  20 static unsigned long page_table_shareable(struct vm_area_struct *svma,
  21                                 struct vm_area_struct *vma,
  22                                 unsigned long addr, pgoff_t idx)
  23 {
  24         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
  25                                 svma->vm_start;
  26         unsigned long sbase = saddr & PUD_MASK;
  27         unsigned long s_end = sbase + PUD_SIZE;
  28
  29         /*
  30          * match the virtual addresses, permission and the alignment of the
  31          * page table page.
  32          */
  33         if (pmd_index(addr) != pmd_index(saddr) ||
  34             vma->vm_flags != svma->vm_flags ||
  35             sbase < svma->vm_start || svma->vm_end < s_end)
  36                 return 0;
  37
  38         return saddr;
  39 }
  40
  41 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
  42 {
  43         unsigned long base = addr & PUD_MASK;
  44         unsigned long end = base + PUD_SIZE;
  45
  46         /*
  47          * check on proper vm_flags and page table alignment
  48          */
  49         if (vma->vm_flags & VM_MAYSHARE &&
  50             vma->vm_start <= base && end <= vma->vm_end)
  51                 return 1;
  52         return 0;
  53 }
  54
  55 /*
  56  * search for a shareable pmd page for hugetlb.
  57  */
  58 static void huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
  59 {
  60         struct vm_area_struct *vma = find_vma(mm, addr);
  61         struct address_space *mapping = vma->vm_file->f_mapping;
  62         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
  63                         vma->vm_pgoff;
  64         struct prio_tree_iter iter;
  65         struct vm_area_struct *svma;
  66         unsigned long saddr;
  67         pte_t *spte = NULL;
  68
  69         if (!vma_shareable(vma, addr))
  70                 return;
  71
  72         spin_lock(&mapping->i_mmap_lock);
  73         vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) {
  74                 if (svma == vma)
  75                         continue;
  76
  77                 saddr = page_table_shareable(svma, vma, addr, idx);
  78                 if (saddr) {
  79                         spte = huge_pte_offset(svma->vm_mm, saddr);
  80                         if (spte) {
  81                                 get_page(virt_to_page(spte));
  82                                 break;
  83                         }
  84                 }
  85         }
  86
  87         if (!spte)
  88                 goto out;
  89
  90         spin_lock(&mm->page_table_lock);
  91         if (pud_none(*pud))
  92                 pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
  93         else
  94                 put_page(virt_to_page(spte));
  95         spin_unlock(&mm->page_table_lock);
  96 out:
  97         spin_unlock(&mapping->i_mmap_lock);
  98 }
  99
 100 /*
 101  * unmap huge page backed by shared pte.
 102  *
 103  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
 104  * indicated by page_count > 1, unmap is achieved by clearing pud and
 105  * decrementing the ref count. If count == 1, the pte page is not shared.
 106  *
 107  * called with vma->vm_mm->page_table_lock held.
 108  *
 109  * returns: 1 successfully unmapped a shared pte page
 110  *          0 the underlying pte page is not shared, or it is the last user
 111  */
 112 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
 113 {
 114         pgd_t *pgd = pgd_offset(mm, *addr);
 115         pud_t *pud = pud_offset(pgd, *addr);
 116
 117         BUG_ON(page_count(virt_to_page(ptep)) == 0);
 118         if (page_count(virt_to_page(ptep)) == 1)
 119                 return 0;
 120
 121         pud_clear(pud);
 122         put_page(virt_to_page(ptep));
 123         *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
 124         return 1;
 125 }
 126
 127 pte_t *huge_pte_alloc(struct mm_struct *mm,
 128                         unsigned long addr, unsigned long sz)
 129 {
 130         pgd_t *pgd;
 131         pud_t *pud;
 132         pte_t *pte = NULL;
 133
 134         pgd = pgd_offset(mm, addr);
 135         pud = pud_alloc(mm, pgd, addr);
 136         if (pud) {
 137                 if (sz == PUD_SIZE) {
 138                         pte = (pte_t *)pud;
 139                 } else {
 140                         BUG_ON(sz != PMD_SIZE);
 141                         if (pud_none(*pud))
 142                                 huge_pmd_share(mm, addr, pud);
 143                         pte = (pte_t *) pmd_alloc(mm, pud, addr);
 144                 }
 145         }
 146         BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
 147
 148         return pte;
 149 }
 150
 151 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 152 {
 153         pgd_t *pgd;
 154         pud_t *pud;
 155         pmd_t *pmd = NULL;
 156
 157         pgd = pgd_offset(mm, addr);
 158         if (pgd_present(*pgd)) {
 159                 pud = pud_offset(pgd, addr);
 160                 if (pud_present(*pud)) {
 161                         if (pud_large(*pud))
 162                                 return (pte_t *)pud;
 163                         pmd = pmd_offset(pud, addr);
 164                 }
 165         }
 166         return (pte_t *) pmd;
 167 }
 168
 169 #if 0   /* This is just for testing */
 170 struct page *
 171 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 172 {
 173         unsigned long start = address;
 174         int length = 1;
 175         int nr;
 176         struct page *page;
 177         struct vm_area_struct *vma;
 178
 179         vma = find_vma(mm, addr);
 180         if (!vma || !is_vm_hugetlb_page(vma))
 181                 return ERR_PTR(-EINVAL);
 182
 183         pte = huge_pte_offset(mm, address);
 184
 185         /* hugetlb should be locked, and hence, prefaulted */
 186         WARN_ON(!pte || pte_none(*pte));
 187
 188         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 189
 190         WARN_ON(!PageHead(page));
 191
 192         return page;
 193 }
 194
 195 int pmd_huge(pmd_t pmd)
 196 {
 197         return 0;
 198 }
 199
 200 int pud_huge(pud_t pud)
 201 {
 202         return 0;
 203 }
 204
 205 struct page *
 206 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 207                 pmd_t *pmd, int write)
 208 {
 209         return NULL;
 210 }
 211
 212 #else
 213
 214 struct page *
 215 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 216 {
 217         return ERR_PTR(-EINVAL);
 218 }
 219
 220 int pmd_huge(pmd_t pmd)
 221 {
 222         return !!(pmd_val(pmd) & _PAGE_PSE);
 223 }
 224
 225 int pud_huge(pud_t pud)
 226 {
 227         return !!(pud_val(pud) & _PAGE_PSE);
 228 }
 229
 230 struct page *
 231 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 232                 pmd_t *pmd, int write)
 233 {
 234         struct page *page;
 235
 236         page = pte_page(*(pte_t *)pmd);
 237         if (page)
 238                 page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
 239         return page;
 240 }
 241
 242 struct page *
 243 follow_huge_pud(struct mm_struct *mm, unsigned long address,
 244                 pud_t *pud, int write)
 245 {
 246         struct page *page;
 247
 248         page = pte_page(*(pte_t *)pud);
 249         if (page)
 250                 page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
 251         return page;
 252 }
 253
 254 #endif
 255
 256 /* x86_64 also uses this file */
 257
 258 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 259 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
 260                 unsigned long addr, unsigned long len,
 261                 unsigned long pgoff, unsigned long flags)
 262 {
 263         struct hstate *h = hstate_file(file);
 264         struct mm_struct *mm = current->mm;
 265         struct vm_area_struct *vma;
 266         unsigned long start_addr;
 267
 268         if (len > mm->cached_hole_size) {
 269                 start_addr = mm->free_area_cache;
 270         } else {
 271                 start_addr = TASK_UNMAPPED_BASE;
 272                 mm->cached_hole_size = 0;
 273         }
 274
 275 full_search:
 276         addr = ALIGN(start_addr, huge_page_size(h));
 277
 278         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
 279                 /* At this point:  (!vma || addr < vma->vm_end). */
 280                 if (TASK_SIZE - len < addr) {
 281                         /*
 282                          * Start a new search - just in case we missed
 283                          * some holes.
 284                          */
 285                         if (start_addr != TASK_UNMAPPED_BASE) {
 286                                 start_addr = TASK_UNMAPPED_BASE;
 287                                 mm->cached_hole_size = 0;
 288                                 goto full_search;
 289                         }
 290                         return -ENOMEM;
 291                 }
 292                 if (!vma || addr + len <= vma->vm_start) {
 293                         mm->free_area_cache = addr + len;
 294                         return addr;
 295                 }
 296                 if (addr + mm->cached_hole_size < vma->vm_start)
 297                         mm->cached_hole_size = vma->vm_start - addr;
 298                 addr = ALIGN(vma->vm_end, huge_page_size(h));
 299         }
 300 }
 301
 302 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 303                 unsigned long addr0, unsigned long len,
 304                 unsigned long pgoff, unsigned long flags)
 305 {
 306         struct hstate *h = hstate_file(file);
 307         struct mm_struct *mm = current->mm;
 308         struct vm_area_struct *vma, *prev_vma;
 309         unsigned long base = mm->mmap_base, addr = addr0;
 310         unsigned long largest_hole = mm->cached_hole_size;
 311         int first_time = 1;
 312
 313         /* don't allow allocations above current base */
 314         if (mm->free_area_cache > base)
 315                 mm->free_area_cache = base;
 316
 317         if (len <= largest_hole) {
 318                 largest_hole = 0;
 319                 mm->free_area_cache  = base;
 320         }
 321 try_again:
 322         /* make sure it can fit in the remaining address space */
 323         if (mm->free_area_cache < len)
 324                 goto fail;
 325
 326         /* either no address requested or cant fit in requested address hole */
 327         addr = (mm->free_area_cache - len) & huge_page_mask(h);
 328         do {
 329                 /*
 330                  * Lookup failure means no vma is above this address,
 331                  * i.e. return with success:
 332                  */
 333                 if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
 334                         return addr;
 335
 336                 /*
 337                  * new region fits between prev_vma->vm_end and
 338                  * vma->vm_start, use it:
 339                  */
 340                 if (addr + len <= vma->vm_start &&
 341                             (!prev_vma || (addr >= prev_vma->vm_end))) {
 342                         /* remember the address as a hint for next time */
 343                         mm->cached_hole_size = largest_hole;
 344                         return (mm->free_area_cache = addr);
 345                 } else {
 346                         /* pull free_area_cache down to the first hole */
 347                         if (mm->free_area_cache == vma->vm_end) {
 348                                 mm->free_area_cache = vma->vm_start;
 349                                 mm->cached_hole_size = largest_hole;
 350                         }
 351                 }
 352
 353                 /* remember the largest hole we saw so far */
 354                 if (addr + largest_hole < vma->vm_start)
 355                         largest_hole = vma->vm_start - addr;
 356
 357                 /* try just below the current vma->vm_start */
 358                 addr = (vma->vm_start - len) & huge_page_mask(h);
 359         } while (len <= vma->vm_start);
 360
 361 fail:
 362         /*
 363          * if hint left us with no space for the requested
 364          * mapping then try again:
 365          */
 366         if (first_time) {
 367                 mm->free_area_cache = base;
 368                 largest_hole = 0;
 369                 first_time = 0;
 370                 goto try_again;
 371         }
 372         /*
 373          * A failed mmap() very likely causes application failure,
 374          * so fall back to the bottom-up function here. This scenario
 375          * can happen with large stack limits and large mmap()
 376          * allocations.
 377          */
 378         mm->free_area_cache = TASK_UNMAPPED_BASE;
 379         mm->cached_hole_size = ~0UL;
 380         addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
 381                         len, pgoff, flags);
 382
 383         /*
 384          * Restore the topdown base:
 385          */
 386         mm->free_area_cache = base;
 387         mm->cached_hole_size = ~0UL;
 388
 389         return addr;
 390 }
 391
 392 unsigned long
 393 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 394                 unsigned long len, unsigned long pgoff, unsigned long flags)
 395 {
 396         struct hstate *h = hstate_file(file);
 397         struct mm_struct *mm = current->mm;
 398         struct vm_area_struct *vma;
 399
 400         if (len & ~huge_page_mask(h))
 401                 return -EINVAL;
 402         if (len > TASK_SIZE)
 403                 return -ENOMEM;
 404
 405         if (flags & MAP_FIXED) {
 406                 if (prepare_hugepage_range(file, addr, len))
 407                         return -EINVAL;
 408                 return addr;
 409         }
 410
 411         if (addr) {
 412                 addr = ALIGN(addr, huge_page_size(h));
 413                 vma = find_vma(mm, addr);
 414                 if (TASK_SIZE - len >= addr &&
 415                     (!vma || addr + len <= vma->vm_start))
 416                         return addr;
 417         }
 418         if (mm->get_unmapped_area == arch_get_unmapped_area)
 419                 return hugetlb_get_unmapped_area_bottomup(file, addr, len,
 420                                 pgoff, flags);
 421         else
 422                 return hugetlb_get_unmapped_area_topdown(file, addr, len,
 423                                 pgoff, flags);
 424 }
 425
 426 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
 427
 428 #ifdef CONFIG_X86_64
 429 static __init int setup_hugepagesz(char *opt)
 430 {
 431         unsigned long ps = memparse(opt, &opt);
 432         if (ps == PMD_SIZE) {
 433                 hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
 434         } else if (ps == PUD_SIZE && cpu_has_gbpages) {
 435                 hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
 436         } else {
 437                 printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
 438                         ps >> 20);
 439                 return 0;
 440         }
 441         return 1;
 442 }
 443 __setup("hugepagesz=", setup_hugepagesz);
 444 #endif