mm/msync.c

   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 sync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
  26                                 unsigned long addr, unsigned long end)
  27 {
  28         pte_t *pte;
  29
  30         pte = pte_offset_map(pmd, addr);
  31         do {
  32                 unsigned long pfn;
  33                 struct page *page;
  34
  35                 if (!pte_present(*pte))
  36                         continue;
  37                 if (!pte_maybe_dirty(*pte))
  38                         continue;
  39                 pfn = pte_pfn(*pte);
  40                 if (!pfn_valid(pfn))
  41                         continue;
  42                 page = pfn_to_page(pfn);
  43                 if (PageReserved(page))
  44                         continue;
  45
  46                 if (ptep_clear_flush_dirty(vma, addr, pte) ||
  47                     page_test_and_clear_dirty(page))
  48                         set_page_dirty(page);
  49         } while (pte++, addr += PAGE_SIZE, addr != end);
  50         pte_unmap(pte - 1);
  51 }
  52
  53 static inline void sync_pmd_range(struct vm_area_struct *vma, pud_t *pud,
  54                                 unsigned long addr, unsigned long end)
  55 {
  56         pmd_t *pmd;
  57         unsigned long next;
  58
  59         pmd = pmd_offset(pud, addr);
  60         do {
  61                 next = pmd_addr_end(addr, end);
  62                 if (pmd_none_or_clear_bad(pmd))
  63                         continue;
  64                 sync_pte_range(vma, pmd, addr, next);
  65         } while (pmd++, addr = next, addr != end);
  66 }
  67
  68 static inline void sync_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
  69                                 unsigned long addr, unsigned long end)
  70 {
  71         pud_t *pud;
  72         unsigned long next;
  73
  74         pud = pud_offset(pgd, addr);
  75         do {
  76                 next = pud_addr_end(addr, end);
  77                 if (pud_none_or_clear_bad(pud))
  78                         continue;
  79                 sync_pmd_range(vma, pud, addr, next);
  80         } while (pud++, addr = next, addr != end);
  81 }
  82
  83 static void sync_page_range(struct vm_area_struct *vma,
  84                                 unsigned long addr, unsigned long end)
  85 {
  86         struct mm_struct *mm = vma->vm_mm;
  87         pgd_t *pgd;
  88         unsigned long next;
  89
  90         /* For hugepages we can't go walking the page table normally,
  91          * but that's ok, hugetlbfs is memory based, so we don't need
  92          * to do anything more on an msync() */
  93         if (is_vm_hugetlb_page(vma))
  94                 return;
  95
  96         BUG_ON(addr >= end);
  97         pgd = pgd_offset(mm, addr);
  98         flush_cache_range(vma, addr, end);
  99         spin_lock(&mm->page_table_lock);
 100         do {
 101                 next = pgd_addr_end(addr, end);
 102                 if (pgd_none_or_clear_bad(pgd))
 103                         continue;
 104                 sync_pud_range(vma, pgd, addr, next);
 105         } while (pgd++, addr = next, addr != end);
 106         spin_unlock(&mm->page_table_lock);
 107 }
 108
 109 #ifdef CONFIG_PREEMPT
 110 static inline void filemap_sync(struct vm_area_struct *vma,
 111                                 unsigned long addr, unsigned long end)
 112 {
 113         const size_t chunk = 64 * 1024; /* bytes */
 114         unsigned long next;
 115
 116         do {
 117                 next = addr + chunk;
 118                 if (next > end || next < addr)
 119                         next = end;
 120                 sync_page_range(vma, addr, next);
 121                 cond_resched();
 122         } while (addr = next, addr != end);
 123 }
 124 #else
 125 static inline void filemap_sync(struct vm_area_struct *vma,
 126                                 unsigned long addr, unsigned long end)
 127 {
 128         sync_page_range(vma, addr, end);
 129 }
 130 #endif
 131
 132 /*
 133  * MS_SYNC syncs the entire file - including mappings.
 134  *
 135  * MS_ASYNC does not start I/O (it used to, up to 2.5.67).  Instead, it just
 136  * marks the relevant pages dirty.  The application may now run fsync() to
 137  * write out the dirty pages and wait on the writeout and check the result.
 138  * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
 139  * async writeout immediately.
 140  * So my _not_ starting I/O in MS_ASYNC we provide complete flexibility to
 141  * applications.
 142  */
 143 static int msync_interval(struct vm_area_struct *vma,
 144                         unsigned long addr, unsigned long end, int flags)
 145 {
 146         int ret = 0;
 147         struct file *file = vma->vm_file;
 148
 149         if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
 150                 return -EBUSY;
 151
 152         if (file && (vma->vm_flags & VM_SHARED)) {
 153                 filemap_sync(vma, addr, end);
 154
 155                 if (flags & MS_SYNC) {
 156                         struct address_space *mapping = file->f_mapping;
 157                         int err;
 158
 159                         ret = filemap_fdatawrite(mapping);
 160                         if (file->f_op && file->f_op->fsync) {
 161                                 /*
 162                                  * We don't take i_sem here because mmap_sem
 163                                  * is already held.
 164                                  */
 165                                 err = file->f_op->fsync(file,file->f_dentry,1);
 166                                 if (err && !ret)
 167                                         ret = err;
 168                         }
 169                         err = filemap_fdatawait(mapping);
 170                         if (!ret)
 171                                 ret = err;
 172                 }
 173         }
 174         return ret;
 175 }
 176
 177 asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
 178 {
 179         unsigned long end;
 180         struct vm_area_struct *vma;
 181         int unmapped_error, error = -EINVAL;
 182
 183         if (flags & MS_SYNC)
 184                 current->flags |= PF_SYNCWRITE;
 185
 186         down_read(&current->mm->mmap_sem);
 187         if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
 188                 goto out;
 189         if (start & ~PAGE_MASK)
 190                 goto out;
 191         if ((flags & MS_ASYNC) && (flags & MS_SYNC))
 192                 goto out;
 193         error = -ENOMEM;
 194         len = (len + ~PAGE_MASK) & PAGE_MASK;
 195         end = start + len;
 196         if (end < start)
 197                 goto out;
 198         error = 0;
 199         if (end == start)
 200                 goto out;
 201         /*
 202          * If the interval [start,end) covers some unmapped address ranges,
 203          * just ignore them, but return -ENOMEM at the end.
 204          */
 205         vma = find_vma(current->mm, start);
 206         unmapped_error = 0;
 207         for (;;) {
 208                 /* Still start < end. */
 209                 error = -ENOMEM;
 210                 if (!vma)
 211                         goto out;
 212                 /* Here start < vma->vm_end. */
 213                 if (start < vma->vm_start) {
 214                         unmapped_error = -ENOMEM;
 215                         start = vma->vm_start;
 216                 }
 217                 /* Here vma->vm_start <= start < vma->vm_end. */
 218                 if (end <= vma->vm_end) {
 219                         if (start < end) {
 220                                 error = msync_interval(vma, start, end, flags);
 221                                 if (error)
 222                                         goto out;
 223                         }
 224                         error = unmapped_error;
 225                         goto out;
 226                 }
 227                 /* Here vma->vm_start <= start < vma->vm_end < end. */
 228                 error = msync_interval(vma, start, vma->vm_end, flags);
 229                 if (error)
 230                         goto out;
 231                 start = vma->vm_end;
 232                 vma = vma->vm_next;
 233         }
 234 out:
 235         up_read(&current->mm->mmap_sem);
 236         current->flags &= ~PF_SYNCWRITE;
 237         return error;
 238 }