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, unsigned long addr)
 128 {
 129         pgd_t *pgd;
 130         pud_t *pud;
 131         pte_t *pte = NULL;
 132
 133         pgd = pgd_offset(mm, addr);
 134         pud = pud_alloc(mm, pgd, addr);
 135         if (pud) {
 136                 if (pud_none(*pud))
 137                         huge_pmd_share(mm, addr, pud);
 138                 pte = (pte_t *) pmd_alloc(mm, pud, addr);
 139         }
 140         BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
 141
 142         return pte;
 143 }
 144
 145 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 146 {
 147         pgd_t *pgd;
 148         pud_t *pud;
 149         pmd_t *pmd = NULL;
 150
 151         pgd = pgd_offset(mm, addr);
 152         if (pgd_present(*pgd)) {
 153                 pud = pud_offset(pgd, addr);
 154                 if (pud_present(*pud))
 155                         pmd = pmd_offset(pud, addr);
 156         }
 157         return (pte_t *) pmd;
 158 }
 159
 160 #if 0   /* This is just for testing */
 161 struct page *
 162 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 163 {
 164         unsigned long start = address;
 165         int length = 1;
 166         int nr;
 167         struct page *page;
 168         struct vm_area_struct *vma;
 169
 170         vma = find_vma(mm, addr);
 171         if (!vma || !is_vm_hugetlb_page(vma))
 172                 return ERR_PTR(-EINVAL);
 173
 174         pte = huge_pte_offset(mm, address);
 175
 176         /* hugetlb should be locked, and hence, prefaulted */
 177         WARN_ON(!pte || pte_none(*pte));
 178
 179         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 180
 181         WARN_ON(!PageHead(page));
 182
 183         return page;
 184 }
 185
 186 int pmd_huge(pmd_t pmd)
 187 {
 188         return 0;
 189 }
 190
 191 struct page *
 192 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 193                 pmd_t *pmd, int write)
 194 {
 195         return NULL;
 196 }
 197
 198 #else
 199
 200 struct page *
 201 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 202 {
 203         return ERR_PTR(-EINVAL);
 204 }
 205
 206 int pmd_huge(pmd_t pmd)
 207 {
 208         return !!(pmd_val(pmd) & _PAGE_PSE);
 209 }
 210
 211 struct page *
 212 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 213                 pmd_t *pmd, int write)
 214 {
 215         struct page *page;
 216
 217         page = pte_page(*(pte_t *)pmd);
 218         if (page)
 219                 page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
 220         return page;
 221 }
 222 #endif
 223
 224 /* x86_64 also uses this file */
 225
 226 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 227 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
 228                 unsigned long addr, unsigned long len,
 229                 unsigned long pgoff, unsigned long flags)
 230 {
 231         struct mm_struct *mm = current->mm;
 232         struct vm_area_struct *vma;
 233         unsigned long start_addr;
 234
 235         if (len > mm->cached_hole_size) {
 236                 start_addr = mm->free_area_cache;
 237         } else {
 238                 start_addr = TASK_UNMAPPED_BASE;
 239                 mm->cached_hole_size = 0;
 240         }
 241
 242 full_search:
 243         addr = ALIGN(start_addr, HPAGE_SIZE);
 244
 245         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
 246                 /* At this point:  (!vma || addr < vma->vm_end). */
 247                 if (TASK_SIZE - len < addr) {
 248                         /*
 249                          * Start a new search - just in case we missed
 250                          * some holes.
 251                          */
 252                         if (start_addr != TASK_UNMAPPED_BASE) {
 253                                 start_addr = TASK_UNMAPPED_BASE;
 254                                 mm->cached_hole_size = 0;
 255                                 goto full_search;
 256                         }
 257                         return -ENOMEM;
 258                 }
 259                 if (!vma || addr + len <= vma->vm_start) {
 260                         mm->free_area_cache = addr + len;
 261                         return addr;
 262                 }
 263                 if (addr + mm->cached_hole_size < vma->vm_start)
 264                         mm->cached_hole_size = vma->vm_start - addr;
 265                 addr = ALIGN(vma->vm_end, HPAGE_SIZE);
 266         }
 267 }
 268
 269 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 270                 unsigned long addr0, unsigned long len,
 271                 unsigned long pgoff, unsigned long flags)
 272 {
 273         struct mm_struct *mm = current->mm;
 274         struct vm_area_struct *vma, *prev_vma;
 275         unsigned long base = mm->mmap_base, addr = addr0;
 276         unsigned long largest_hole = mm->cached_hole_size;
 277         int first_time = 1;
 278
 279         /* don't allow allocations above current base */
 280         if (mm->free_area_cache > base)
 281                 mm->free_area_cache = base;
 282
 283         if (len <= largest_hole) {
 284                 largest_hole = 0;
 285                 mm->free_area_cache  = base;
 286         }
 287 try_again:
 288         /* make sure it can fit in the remaining address space */
 289         if (mm->free_area_cache < len)
 290                 goto fail;
 291
 292         /* either no address requested or cant fit in requested address hole */
 293         addr = (mm->free_area_cache - len) & HPAGE_MASK;
 294         do {
 295                 /*
 296                  * Lookup failure means no vma is above this address,
 297                  * i.e. return with success:
 298                  */
 299                 if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
 300                         return addr;
 301
 302                 /*
 303                  * new region fits between prev_vma->vm_end and
 304                  * vma->vm_start, use it:
 305                  */
 306                 if (addr + len <= vma->vm_start &&
 307                             (!prev_vma || (addr >= prev_vma->vm_end))) {
 308                         /* remember the address as a hint for next time */
 309                         mm->cached_hole_size = largest_hole;
 310                         return (mm->free_area_cache = addr);
 311                 } else {
 312                         /* pull free_area_cache down to the first hole */
 313                         if (mm->free_area_cache == vma->vm_end) {
 314                                 mm->free_area_cache = vma->vm_start;
 315                                 mm->cached_hole_size = largest_hole;
 316                         }
 317                 }
 318
 319                 /* remember the largest hole we saw so far */
 320                 if (addr + largest_hole < vma->vm_start)
 321                         largest_hole = vma->vm_start - addr;
 322
 323                 /* try just below the current vma->vm_start */
 324                 addr = (vma->vm_start - len) & HPAGE_MASK;
 325         } while (len <= vma->vm_start);
 326
 327 fail:
 328         /*
 329          * if hint left us with no space for the requested
 330          * mapping then try again:
 331          */
 332         if (first_time) {
 333                 mm->free_area_cache = base;
 334                 largest_hole = 0;
 335                 first_time = 0;
 336                 goto try_again;
 337         }
 338         /*
 339          * A failed mmap() very likely causes application failure,
 340          * so fall back to the bottom-up function here. This scenario
 341          * can happen with large stack limits and large mmap()
 342          * allocations.
 343          */
 344         mm->free_area_cache = TASK_UNMAPPED_BASE;
 345         mm->cached_hole_size = ~0UL;
 346         addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
 347                         len, pgoff, flags);
 348
 349         /*
 350          * Restore the topdown base:
 351          */
 352         mm->free_area_cache = base;
 353         mm->cached_hole_size = ~0UL;
 354
 355         return addr;
 356 }
 357
 358 unsigned long
 359 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 360                 unsigned long len, unsigned long pgoff, unsigned long flags)
 361 {
 362         struct mm_struct *mm = current->mm;
 363         struct vm_area_struct *vma;
 364
 365         if (len & ~HPAGE_MASK)
 366                 return -EINVAL;
 367         if (len > TASK_SIZE)
 368                 return -ENOMEM;
 369
 370         if (flags & MAP_FIXED) {
 371                 if (prepare_hugepage_range(addr, len))
 372                         return -EINVAL;
 373                 return addr;
 374         }
 375
 376         if (addr) {
 377                 addr = ALIGN(addr, HPAGE_SIZE);
 378                 vma = find_vma(mm, addr);
 379                 if (TASK_SIZE - len >= addr &&
 380                     (!vma || addr + len <= vma->vm_start))
 381                         return addr;
 382         }
 383         if (mm->get_unmapped_area == arch_get_unmapped_area)
 384                 return hugetlb_get_unmapped_area_bottomup(file, addr, len,
 385                                 pgoff, flags);
 386         else
 387                 return hugetlb_get_unmapped_area_topdown(file, addr, len,
 388                                 pgoff, flags);
 389 }
 390
 391 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
 392