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   1 /*
   2  *      linux/mm/msync.c
   3  *
   4  * Copyright (C) 1994-1999  Linus Torvalds
   5  */
   6
   7 /*
   8  * The msync() system call.
   9  */
  10 #include <linux/slab.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/mm.h>
  13 #include <linux/mman.h>
  14 #include <linux/hugetlb.h>
  15 #include <linux/syscalls.h>
  16
  17 #include <asm/pgtable.h>
  18 #include <asm/tlbflush.h>
  19
  20 /*
  21  * Called with mm->page_table_lock held to protect against other
  22  * threads/the swapper from ripping pte's out from under us.
  23  */
  24
  25 static void msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
  26                                 unsigned long addr, unsigned long end)
  27 {
  28         struct mm_struct *mm = vma->vm_mm;
  29         pte_t *pte;
  30         int progress = 0;
  31
  32 again:
  33         pte = pte_offset_map(pmd, addr);
  34         do {
  35                 unsigned long pfn;
  36                 struct page *page;
  37
  38                 if (progress >= 64) {
  39                         progress = 0;
  40                         if (need_resched() ||
  41                             need_lockbreak(&mm->page_table_lock))
  42                                 break;
  43                 }
  44                 progress++;
  45                 if (!pte_present(*pte))
  46                         continue;
  47                 if (!pte_maybe_dirty(*pte))
  48                         continue;
  49                 pfn = pte_pfn(*pte);
  50                 if (unlikely(!pfn_valid(pfn))) {
  51                         print_bad_pte(vma, *pte, addr);
  52                         continue;
  53                 }
  54                 page = pfn_to_page(pfn);
  55
  56                 if (ptep_clear_flush_dirty(vma, addr, pte) ||
  57                     page_test_and_clear_dirty(page))
  58                         set_page_dirty(page);
  59                 progress += 3;
  60         } while (pte++, addr += PAGE_SIZE, addr != end);
  61         pte_unmap(pte - 1);
  62         cond_resched_lock(&mm->page_table_lock);
  63         if (addr != end)
  64                 goto again;
  65 }
  66
  67 static inline void msync_pmd_range(struct vm_area_struct *vma, pud_t *pud,
  68                                 unsigned long addr, unsigned long end)
  69 {
  70         pmd_t *pmd;
  71         unsigned long next;
  72
  73         pmd = pmd_offset(pud, addr);
  74         do {
  75                 next = pmd_addr_end(addr, end);
  76                 if (pmd_none_or_clear_bad(pmd))
  77                         continue;
  78                 msync_pte_range(vma, pmd, addr, next);
  79         } while (pmd++, addr = next, addr != end);
  80 }
  81
  82 static inline void msync_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
  83                                 unsigned long addr, unsigned long end)
  84 {
  85         pud_t *pud;
  86         unsigned long next;
  87
  88         pud = pud_offset(pgd, addr);
  89         do {
  90                 next = pud_addr_end(addr, end);
  91                 if (pud_none_or_clear_bad(pud))
  92                         continue;
  93                 msync_pmd_range(vma, pud, addr, next);
  94         } while (pud++, addr = next, addr != end);
  95 }
  96
  97 static void msync_page_range(struct vm_area_struct *vma,
  98                                 unsigned long addr, unsigned long end)
  99 {
 100         struct mm_struct *mm = vma->vm_mm;
 101         pgd_t *pgd;
 102         unsigned long next;
 103
 104         /* For hugepages we can't go walking the page table normally,
 105          * but that's ok, hugetlbfs is memory based, so we don't need
 106          * to do anything more on an msync().
 107          * Can't do anything with VM_RESERVED regions either.
 108          */
 109         if (vma->vm_flags & (VM_HUGETLB|VM_RESERVED))
 110                 return;
 111
 112         BUG_ON(addr >= end);
 113         pgd = pgd_offset(mm, addr);
 114         flush_cache_range(vma, addr, end);
 115         spin_lock(&mm->page_table_lock);
 116         do {
 117                 next = pgd_addr_end(addr, end);
 118                 if (pgd_none_or_clear_bad(pgd))
 119                         continue;
 120                 msync_pud_range(vma, pgd, addr, next);
 121         } while (pgd++, addr = next, addr != end);
 122         spin_unlock(&mm->page_table_lock);
 123 }
 124
 125 /*
 126  * MS_SYNC syncs the entire file - including mappings.
 127  *
 128  * MS_ASYNC does not start I/O (it used to, up to 2.5.67).  Instead, it just
 129  * marks the relevant pages dirty.  The application may now run fsync() to
 130  * write out the dirty pages and wait on the writeout and check the result.
 131  * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
 132  * async writeout immediately.
 133  * So my _not_ starting I/O in MS_ASYNC we provide complete flexibility to
 134  * applications.
 135  */
 136 static int msync_interval(struct vm_area_struct *vma,
 137                         unsigned long addr, unsigned long end, int flags)
 138 {
 139         int ret = 0;
 140         struct file *file = vma->vm_file;
 141
 142         if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
 143                 return -EBUSY;
 144
 145         if (file && (vma->vm_flags & VM_SHARED)) {
 146                 msync_page_range(vma, addr, end);
 147
 148                 if (flags & MS_SYNC) {
 149                         struct address_space *mapping = file->f_mapping;
 150                         int err;
 151
 152                         ret = filemap_fdatawrite(mapping);
 153                         if (file->f_op && file->f_op->fsync) {
 154                                 /*
 155                                  * We don't take i_sem here because mmap_sem
 156                                  * is already held.
 157                                  */
 158                                 err = file->f_op->fsync(file,file->f_dentry,1);
 159                                 if (err && !ret)
 160                                         ret = err;
 161                         }
 162                         err = filemap_fdatawait(mapping);
 163                         if (!ret)
 164                                 ret = err;
 165                 }
 166         }
 167         return ret;
 168 }
 169
 170 asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
 171 {
 172         unsigned long end;
 173         struct vm_area_struct *vma;
 174         int unmapped_error, error = -EINVAL;
 175
 176         if (flags & MS_SYNC)
 177                 current->flags |= PF_SYNCWRITE;
 178
 179         down_read(&current->mm->mmap_sem);
 180         if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
 181                 goto out;
 182         if (start & ~PAGE_MASK)
 183                 goto out;
 184         if ((flags & MS_ASYNC) && (flags & MS_SYNC))
 185                 goto out;
 186         error = -ENOMEM;
 187         len = (len + ~PAGE_MASK) & PAGE_MASK;
 188         end = start + len;
 189         if (end < start)
 190                 goto out;
 191         error = 0;
 192         if (end == start)
 193                 goto out;
 194         /*
 195          * If the interval [start,end) covers some unmapped address ranges,
 196          * just ignore them, but return -ENOMEM at the end.
 197          */
 198         vma = find_vma(current->mm, start);
 199         unmapped_error = 0;
 200         for (;;) {
 201                 /* Still start < end. */
 202                 error = -ENOMEM;
 203                 if (!vma)
 204                         goto out;
 205                 /* Here start < vma->vm_end. */
 206                 if (start < vma->vm_start) {
 207                         unmapped_error = -ENOMEM;
 208                         start = vma->vm_start;
 209                 }
 210                 /* Here vma->vm_start <= start < vma->vm_end. */
 211                 if (end <= vma->vm_end) {
 212                         if (start < end) {
 213                                 error = msync_interval(vma, start, end, flags);
 214                                 if (error)
 215                                         goto out;
 216                         }
 217                         error = unmapped_error;
 218                         goto out;
 219                 }
 220                 /* Here vma->vm_start <= start < vma->vm_end < end. */
 221                 error = msync_interval(vma, start, vma->vm_end, flags);
 222                 if (error)
 223                         goto out;
 224                 start = vma->vm_end;
 225                 vma = vma->vm_next;
 226         }
 227 out:
 228         up_read(&current->mm->mmap_sem);
 229         current->flags &= ~PF_SYNCWRITE;
 230         return error;
 231 }