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/err.h>
  13 #include <linux/sysctl.h>
  14 #include <asm/mman.h>
  15 #include <asm/tlb.h>
  16 #include <asm/tlbflush.h>
  17 #include <asm/pgalloc.h>
  18
  19 static unsigned long page_table_shareable(struct vm_area_struct *svma,
  20                                 struct vm_area_struct *vma,
  21                                 unsigned long addr, pgoff_t idx)
  22 {
  23         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
  24                                 svma->vm_start;
  25         unsigned long sbase = saddr & PUD_MASK;
  26         unsigned long s_end = sbase + PUD_SIZE;
  27
  28         /* Allow segments to share if only one is marked locked */
  29         unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
  30         unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;
  31
  32         /*
  33          * match the virtual addresses, permission and the alignment of the
  34          * page table page.
  35          */
  36         if (pmd_index(addr) != pmd_index(saddr) ||
  37             vm_flags != svm_flags ||
  38             sbase < svma->vm_start || svma->vm_end < s_end)
  39                 return 0;
  40
  41         return saddr;
  42 }
  43
  44 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
  45 {
  46         unsigned long base = addr & PUD_MASK;
  47         unsigned long end = base + PUD_SIZE;
  48
  49         /*
  50          * check on proper vm_flags and page table alignment
  51          */
  52         if (vma->vm_flags & VM_MAYSHARE &&
  53             vma->vm_start <= base && end <= vma->vm_end)
  54                 return 1;
  55         return 0;
  56 }
  57
  58 /*
  59  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
  60  * and returns the corresponding pte. While this is not necessary for the
  61  * !shared pmd case because we can allocate the pmd later as well, it makes the
  62  * code much cleaner. pmd allocation is essential for the shared case because
  63  * pud has to be populated inside the same i_mmap_mutex section - otherwise
  64  * racing tasks could either miss the sharing (see huge_pte_offset) or select a
  65  * bad pmd for sharing.
  66  */
  67 static pte_t *
  68 huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
  69 {
  70         struct vm_area_struct *vma = find_vma(mm, addr);
  71         struct address_space *mapping = vma->vm_file->f_mapping;
  72         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
  73                         vma->vm_pgoff;
  74         struct vm_area_struct *svma;
  75         unsigned long saddr;
  76         pte_t *spte = NULL;
  77         pte_t *pte;
  78
  79         if (!vma_shareable(vma, addr))
  80                 return (pte_t *)pmd_alloc(mm, pud, addr);
  81
  82         mutex_lock(&mapping->i_mmap_mutex);
  83         vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
  84                 if (svma == vma)
  85                         continue;
  86
  87                 saddr = page_table_shareable(svma, vma, addr, idx);
  88                 if (saddr) {
  89                         spte = huge_pte_offset(svma->vm_mm, saddr);
  90                         if (spte) {
  91                                 get_page(virt_to_page(spte));
  92                                 break;
  93                         }
  94                 }
  95         }
  96
  97         if (!spte)
  98                 goto out;
  99
 100         spin_lock(&mm->page_table_lock);
 101         if (pud_none(*pud))
 102                 pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
 103         else
 104                 put_page(virt_to_page(spte));
 105         spin_unlock(&mm->page_table_lock);
 106 out:
 107         pte = (pte_t *)pmd_alloc(mm, pud, addr);
 108         mutex_unlock(&mapping->i_mmap_mutex);
 109         return pte;
 110 }
 111
 112 /*
 113  * unmap huge page backed by shared pte.
 114  *
 115  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
 116  * indicated by page_count > 1, unmap is achieved by clearing pud and
 117  * decrementing the ref count. If count == 1, the pte page is not shared.
 118  *
 119  * called with vma->vm_mm->page_table_lock held.
 120  *
 121  * returns: 1 successfully unmapped a shared pte page
 122  *          0 the underlying pte page is not shared, or it is the last user
 123  */
 124 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
 125 {
 126         pgd_t *pgd = pgd_offset(mm, *addr);
 127         pud_t *pud = pud_offset(pgd, *addr);
 128
 129         BUG_ON(page_count(virt_to_page(ptep)) == 0);
 130         if (page_count(virt_to_page(ptep)) == 1)
 131                 return 0;
 132
 133         pud_clear(pud);
 134         put_page(virt_to_page(ptep));
 135         *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
 136         return 1;
 137 }
 138
 139 pte_t *huge_pte_alloc(struct mm_struct *mm,
 140                         unsigned long addr, unsigned long sz)
 141 {
 142         pgd_t *pgd;
 143         pud_t *pud;
 144         pte_t *pte = NULL;
 145
 146         pgd = pgd_offset(mm, addr);
 147         pud = pud_alloc(mm, pgd, addr);
 148         if (pud) {
 149                 if (sz == PUD_SIZE) {
 150                         pte = (pte_t *)pud;
 151                 } else {
 152                         BUG_ON(sz != PMD_SIZE);
 153                         if (pud_none(*pud))
 154                                 pte = huge_pmd_share(mm, addr, pud);
 155                         else
 156                                 pte = (pte_t *)pmd_alloc(mm, pud, addr);
 157                 }
 158         }
 159         BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
 160
 161         return pte;
 162 }
 163
 164 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 165 {
 166         pgd_t *pgd;
 167         pud_t *pud;
 168         pmd_t *pmd = NULL;
 169
 170         pgd = pgd_offset(mm, addr);
 171         if (pgd_present(*pgd)) {
 172                 pud = pud_offset(pgd, addr);
 173                 if (pud_present(*pud)) {
 174                         if (pud_large(*pud))
 175                                 return (pte_t *)pud;
 176                         pmd = pmd_offset(pud, addr);
 177                 }
 178         }
 179         return (pte_t *) pmd;
 180 }
 181
 182 #if 0   /* This is just for testing */
 183 struct page *
 184 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 185 {
 186         unsigned long start = address;
 187         int length = 1;
 188         int nr;
 189         struct page *page;
 190         struct vm_area_struct *vma;
 191
 192         vma = find_vma(mm, addr);
 193         if (!vma || !is_vm_hugetlb_page(vma))
 194                 return ERR_PTR(-EINVAL);
 195
 196         pte = huge_pte_offset(mm, address);
 197
 198         /* hugetlb should be locked, and hence, prefaulted */
 199         WARN_ON(!pte || pte_none(*pte));
 200
 201         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 202
 203         WARN_ON(!PageHead(page));
 204
 205         return page;
 206 }
 207
 208 int pmd_huge(pmd_t pmd)
 209 {
 210         return 0;
 211 }
 212
 213 int pud_huge(pud_t pud)
 214 {
 215         return 0;
 216 }
 217
 218 struct page *
 219 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 220                 pmd_t *pmd, int write)
 221 {
 222         return NULL;
 223 }
 224
 225 #else
 226
 227 struct page *
 228 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 229 {
 230         return ERR_PTR(-EINVAL);
 231 }
 232
 233 int pmd_huge(pmd_t pmd)
 234 {
 235         return !!(pmd_val(pmd) & _PAGE_PSE);
 236 }
 237
 238 int pud_huge(pud_t pud)
 239 {
 240         return !!(pud_val(pud) & _PAGE_PSE);
 241 }
 242
 243 struct page *
 244 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 245                 pmd_t *pmd, int write)
 246 {
 247         struct page *page;
 248
 249         page = pte_page(*(pte_t *)pmd);
 250         if (page)
 251                 page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
 252         return page;
 253 }
 254
 255 struct page *
 256 follow_huge_pud(struct mm_struct *mm, unsigned long address,
 257                 pud_t *pud, int write)
 258 {
 259         struct page *page;
 260
 261         page = pte_page(*(pte_t *)pud);
 262         if (page)
 263                 page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
 264         return page;
 265 }
 266
 267 #endif
 268
 269 /* x86_64 also uses this file */
 270
 271 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 272 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
 273                 unsigned long addr, unsigned long len,
 274                 unsigned long pgoff, unsigned long flags)
 275 {
 276         struct hstate *h = hstate_file(file);
 277         struct vm_unmapped_area_info info;
 278
 279         info.flags = 0;
 280         info.length = len;
 281         info.low_limit = TASK_UNMAPPED_BASE;
 282         info.high_limit = TASK_SIZE;
 283         info.align_mask = PAGE_MASK & ~huge_page_mask(h);
 284         info.align_offset = 0;
 285         return vm_unmapped_area(&info);
 286 }
 287
 288 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 289                 unsigned long addr0, unsigned long len,
 290                 unsigned long pgoff, unsigned long flags)
 291 {
 292         struct hstate *h = hstate_file(file);
 293         struct vm_unmapped_area_info info;
 294         unsigned long addr;
 295
 296         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 297         info.length = len;
 298         info.low_limit = PAGE_SIZE;
 299         info.high_limit = current->mm->mmap_base;
 300         info.align_mask = PAGE_MASK & ~huge_page_mask(h);
 301         info.align_offset = 0;
 302         addr = vm_unmapped_area(&info);
 303
 304         /*
 305          * A failed mmap() very likely causes application failure,
 306          * so fall back to the bottom-up function here. This scenario
 307          * can happen with large stack limits and large mmap()
 308          * allocations.
 309          */
 310         if (addr & ~PAGE_MASK) {
 311                 VM_BUG_ON(addr != -ENOMEM);
 312                 info.flags = 0;
 313                 info.low_limit = TASK_UNMAPPED_BASE;
 314                 info.high_limit = TASK_SIZE;
 315                 addr = vm_unmapped_area(&info);
 316         }
 317
 318         return addr;
 319 }
 320
 321 unsigned long
 322 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 323                 unsigned long len, unsigned long pgoff, unsigned long flags)
 324 {
 325         struct hstate *h = hstate_file(file);
 326         struct mm_struct *mm = current->mm;
 327         struct vm_area_struct *vma;
 328
 329         if (len & ~huge_page_mask(h))
 330                 return -EINVAL;
 331         if (len > TASK_SIZE)
 332                 return -ENOMEM;
 333
 334         if (flags & MAP_FIXED) {
 335                 if (prepare_hugepage_range(file, addr, len))
 336                         return -EINVAL;
 337                 return addr;
 338         }
 339
 340         if (addr) {
 341                 addr = ALIGN(addr, huge_page_size(h));
 342                 vma = find_vma(mm, addr);
 343                 if (TASK_SIZE - len >= addr &&
 344                     (!vma || addr + len <= vma->vm_start))
 345                         return addr;
 346         }
 347         if (mm->get_unmapped_area == arch_get_unmapped_area)
 348                 return hugetlb_get_unmapped_area_bottomup(file, addr, len,
 349                                 pgoff, flags);
 350         else
 351                 return hugetlb_get_unmapped_area_topdown(file, addr, len,
 352                                 pgoff, flags);
 353 }
 354
 355 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
 356
 357 #ifdef CONFIG_X86_64
 358 static __init int setup_hugepagesz(char *opt)
 359 {
 360         unsigned long ps = memparse(opt, &opt);
 361         if (ps == PMD_SIZE) {
 362                 hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
 363         } else if (ps == PUD_SIZE && cpu_has_gbpages) {
 364                 hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
 365         } else {
 366                 printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
 367                         ps >> 20);
 368                 return 0;
 369         }
 370         return 1;
 371 }
 372 __setup("hugepagesz=", setup_hugepagesz);
 373 #endif