fs/fat/mmap.c

   1 /*
   2  *      linux/fs/fat/mmap.c
   3  *
   4  *      Written by Jacques Gelinas (jacques@solucorp.qc.ca)
   5  *      Inspired by fs/nfs/mmap.c (Jon Tombs 15 Aug 1993)
   6  *
   7  *      mmap handling for fat-based filesystems
   8  */
   9
  10 #define ASC_LINUX_VERSION(V, P, S)      (((V) * 65536) + ((P) * 256) + (S))
  11 #include <linux/version.h>
  12
  13 #include <linux/stat.h>
  14 #include <linux/sched.h>
  15 #include <linux/kernel.h>
  16 #include <linux/mm.h>
  17 #include <linux/shm.h>
  18 #include <linux/errno.h>
  19 #include <linux/mman.h>
  20 #include <linux/string.h>
  21 #include <linux/malloc.h>
  22 #include <linux/msdos_fs.h>
  23
  24 #include <asm/uaccess.h>
  25 #include <asm/system.h>
  26
  27 /*
  28  * Fill in the supplied page for mmap
  29  */
  30 static unsigned long fat_file_mmap_nopage(
  31         struct vm_area_struct * area,
  32         unsigned long address,
  33         int error_code)
  34 {
  35         struct inode * inode = area->vm_dentry->d_inode;
  36         unsigned long page;
  37         unsigned int clear;
  38         int pos;
  39         long gap;       /* distance from eof to pos */
  40
  41         page = __get_free_page(GFP_KERNEL);
  42         if (!page)
  43                 return page;
  44         address &= PAGE_MASK;
  45         pos = address - area->vm_start + area->vm_offset;
  46
  47         clear = 0;
  48         gap = inode->i_size - pos;
  49         if (gap <= 0){
  50                 /* mmaping beyond end of file */
  51                 clear = PAGE_SIZE;
  52         }else{
  53                 int cur_read;
  54                 int need_read;
  55                 struct file filp;
  56                 if (gap < PAGE_SIZE){
  57                         clear = PAGE_SIZE - gap;
  58                 }
  59                 filp.f_reada = 0;
  60                 filp.f_pos = pos;
  61                 need_read = PAGE_SIZE - clear;
  62                 {
  63                         mm_segment_t cur_fs = get_fs();
  64                         set_fs (KERNEL_DS);
  65                         cur_read = fat_file_read (&filp, (char*)page,
  66                                                   need_read, &filp.f_pos);
  67                         set_fs (cur_fs);
  68                 }
  69                 if (cur_read != need_read){
  70                         printk ("MSDOS: Error while reading an mmap file %d <> %d\n"
  71                                 ,cur_read,need_read);
  72                 }
  73         }
  74         if (clear > 0){
  75                 memset ((char*)page+PAGE_SIZE-clear,0,clear);
  76         }
  77         return page;
  78 }
  79
  80 struct vm_operations_struct fat_file_mmap = {
  81         NULL,                   /* open */
  82         NULL,                   /* close */
  83         NULL,                   /* unmap */
  84         NULL,                   /* protect */
  85         NULL,                   /* sync */
  86         NULL,                   /* advise */
  87         fat_file_mmap_nopage,   /* nopage */
  88         NULL,                   /* wppage */
  89         NULL,                   /* swapout */
  90         NULL,                   /* swapin */
  91 };
  92
  93 /*
  94  * This is used for a general mmap of an msdos file
  95  * Returns 0 if ok, or a negative error code if not.
  96  */
  97 int fat_mmap(struct file * file, struct vm_area_struct * vma)
  98 {
  99         struct inode *inode = file->f_dentry->d_inode;
 100         if (MSDOS_SB(inode->i_sb)->cvf_format &&
 101             MSDOS_SB(inode->i_sb)->cvf_format->cvf_mmap)
 102                 return MSDOS_SB(inode->i_sb)->cvf_format->cvf_mmap(file,vma);
 103
 104         if (vma->vm_flags & VM_SHARED)  /* only PAGE_COW or read-only supported now */
 105                 return -EINVAL;
 106         if (vma->vm_offset & (inode->i_sb->s_blocksize - 1))
 107                 return -EINVAL;
 108         if (!inode->i_sb || !S_ISREG(inode->i_mode))
 109                 return -EACCES;
 110         if (!IS_RDONLY(inode)) {
 111                 inode->i_atime = CURRENT_TIME;
 112                 mark_inode_dirty(inode);
 113         }
 114
 115         vma->vm_dentry = dget(file->f_dentry);
 116         vma->vm_ops = &fat_file_mmap;
 117         return 0;
 118 }
 119
 120
 121 int fat_readpage(struct dentry * dentry, struct page * page)
 122 {
 123         struct inode * inode = dentry->d_inode;
 124         if (MSDOS_SB(inode->i_sb)->cvf_format &&
 125             MSDOS_SB(inode->i_sb)->cvf_format->cvf_readpage)
 126                 return MSDOS_SB(inode->i_sb)->cvf_format->cvf_readpage(inode,page);
 127
 128         printk("fat_readpage called with no handler (shouldn't happen)\n");
 129         return -1;
 130 }
 131