fs/umsdos/symlink.c

   1 /*
   2  *  linux/fs/umsdos/file.c
   3  *
   4  *  Written 1992 by Jacques Gelinas
   5  *      inspired from linux/fs/msdos/file.c Werner Almesberger
   6  *
   7  *  Extended MS-DOS regular file handling primitives
   8  */
   9
  10 #include <linux/sched.h>
  11 #include <linux/fs.h>
  12 #include <linux/msdos_fs.h>
  13 #include <linux/errno.h>
  14 #include <linux/fcntl.h>
  15 #include <linux/stat.h>
  16 #include <linux/umsdos_fs.h>
  17 #include <linux/malloc.h>
  18
  19 #include <asm/uaccess.h>
  20 #include <asm/system.h>
  21
  22 static struct file_operations umsdos_symlink_operations;
  23
  24
  25 /*
  26  * Read the data associate with the symlink.
  27  * Return length read in buffer or  a negative error code.
  28  *
  29  */
  30
  31 int umsdos_readlink_x (      struct dentry *dentry,
  32                              char *buffer,
  33                              int bufsiz)
  34 {
  35         size_t size = dentry->d_inode->i_size;
  36         loff_t loffs = 0;
  37         ssize_t ret;
  38         struct file filp;
  39
  40 Printk((KERN_DEBUG "UMSDOS_read: %s/%s, size=%u\n",
  41 dentry->d_parent->d_name.name, dentry->d_name.name, size));
  42
  43         fill_new_filp (&filp, dentry);
  44         filp.f_reada = 0;
  45         filp.f_flags = O_RDONLY;
  46         filp.f_op    = &umsdos_symlink_operations;
  47
  48         if (size > bufsiz)
  49                 size = bufsiz;
  50
  51         ret = fat_file_read (&filp, buffer, size, &loffs);
  52         if (ret != size) {
  53                 ret = -EIO;
  54         }
  55         return ret;
  56 }
  57
  58
  59
  60 static int UMSDOS_readlink (struct dentry *dentry, char *buffer, int buflen)
  61 {
  62         return umsdos_readlink_x (dentry, buffer, buflen);
  63 }
  64
  65 /* this one mostly stolen from romfs :) */
  66 static struct dentry *UMSDOS_followlink (struct dentry *dentry,
  67                                         struct dentry *base,
  68                                         unsigned int follow)
  69 {
  70         struct inode *inode = dentry->d_inode;
  71         char *symname;
  72         int len, cnt;
  73         mm_segment_t old_fs = get_fs ();
  74
  75 Printk((KERN_DEBUG "UMSDOS_followlink /mn/: (%s/%s)\n",
  76 dentry->d_parent->d_name.name, dentry->d_name.name));
  77
  78         len = inode->i_size;
  79
  80         if (!(symname = kmalloc (len + 1, GFP_KERNEL))) {
  81                 dentry = ERR_PTR (-ENOMEM);
  82                 goto outnobuf;
  83         }
  84
  85         set_fs (KERNEL_DS);     /* we read into kernel space this time */
  86         cnt = umsdos_readlink_x (dentry, symname, len);
  87         set_fs (old_fs);
  88
  89         if (len != cnt) {
  90                 dentry = ERR_PTR (-EIO);
  91                 goto out;
  92         }
  93
  94         symname[len] = 0;
  95         dentry = lookup_dentry (symname, base, follow);
  96         kfree (symname);
  97
  98         if (0) {
  99               out:
 100                 kfree (symname);
 101               outnobuf:
 102                 dput (base);
 103         }
 104         return dentry;
 105 }
 106
 107 /* needed to patch the file structure */
 108 static struct file_operations umsdos_symlink_operations =
 109 {
 110         NULL,                   /* lseek - default */
 111         NULL,                   /* read */
 112         NULL,                   /* write */
 113         NULL,                   /* readdir - bad */
 114         NULL,                   /* poll - default */
 115         NULL,                   /* ioctl - default */
 116         NULL,                   /* mmap */
 117         NULL,                   /* no special open is needed */
 118         NULL,                   /* no flush code */
 119         NULL,                   /* release */
 120         NULL                    /* fsync */
 121 };
 122
 123
 124 struct inode_operations umsdos_symlink_inode_operations =
 125 {
 126         NULL,                   /* default file operations (none) */
 127         NULL,                   /* create */
 128         NULL,                   /* lookup */
 129         NULL,                   /* link */
 130         NULL,                   /* unlink */
 131         NULL,                   /* symlink */
 132         NULL,                   /* mkdir */
 133         NULL,                   /* rmdir */
 134         NULL,                   /* mknod */
 135         NULL,                   /* rename */
 136         UMSDOS_readlink,        /* readlink */
 137         UMSDOS_followlink,      /* followlink */
 138         generic_readpage,       /* readpage */
 139         NULL,                   /* writepage */
 140         fat_bmap,               /* bmap */
 141         NULL,                   /* truncate */
 142         NULL,                   /* permission */
 143         NULL,                   /* smap */
 144         NULL,                   /* updatepage */
 145         NULL                    /* revalidate */
 146 };
 147