fs/isofs/export.c

   1 /*
   2  * fs/isofs/export.c
   3  *
   4  *  (C) 2004  Paul Serice - The new inode scheme requires switching
   5  *                          from iget() to iget5_locked() which means
   6  *                          the NFS export operations have to be hand
   7  *                          coded because the default routines rely on
   8  *                          iget().
   9  *
  10  * The following files are helpful:
  11  *
  12  *     Documentation/filesystems/nfs/Exporting
  13  *     fs/exportfs/expfs.c.
  14  */
  15
  16 #include "isofs.h"
  17
  18 static struct dentry *
  19 isofs_export_iget(struct super_block *sb,
  20                   unsigned long block,
  21                   unsigned long offset,
  22                   __u32 generation)
  23 {
  24         struct inode *inode;
  25
  26         if (block == 0)
  27                 return ERR_PTR(-ESTALE);
  28         inode = isofs_iget(sb, block, offset);
  29         if (IS_ERR(inode))
  30                 return ERR_CAST(inode);
  31         if (generation && inode->i_generation != generation) {
  32                 iput(inode);
  33                 return ERR_PTR(-ESTALE);
  34         }
  35         return d_obtain_alias(inode);
  36 }
  37
  38 /* This function is surprisingly simple.  The trick is understanding
  39  * that "child" is always a directory. So, to find its parent, you
  40  * simply need to find its ".." entry, normalize its block and offset,
  41  * and return the underlying inode.  See the comments for
  42  * isofs_normalize_block_and_offset(). */
  43 static struct dentry *isofs_export_get_parent(struct dentry *child)
  44 {
  45         unsigned long parent_block = 0;
  46         unsigned long parent_offset = 0;
  47         struct inode *child_inode = child->d_inode;
  48         struct iso_inode_info *e_child_inode = ISOFS_I(child_inode);
  49         struct iso_directory_record *de = NULL;
  50         struct buffer_head * bh = NULL;
  51         struct dentry *rv = NULL;
  52
  53         /* "child" must always be a directory. */
  54         if (!S_ISDIR(child_inode->i_mode)) {
  55                 printk(KERN_ERR "isofs: isofs_export_get_parent(): "
  56                        "child is not a directory!\n");
  57                 rv = ERR_PTR(-EACCES);
  58                 goto out;
  59         }
  60
  61         /* It is an invariant that the directory offset is zero.  If
  62          * it is not zero, it means the directory failed to be
  63          * normalized for some reason. */
  64         if (e_child_inode->i_iget5_offset != 0) {
  65                 printk(KERN_ERR "isofs: isofs_export_get_parent(): "
  66                        "child directory not normalized!\n");
  67                 rv = ERR_PTR(-EACCES);
  68                 goto out;
  69         }
  70
  71         /* The child inode has been normalized such that its
  72          * i_iget5_block value points to the "." entry.  Fortunately,
  73          * the ".." entry is located in the same block. */
  74         parent_block = e_child_inode->i_iget5_block;
  75
  76         /* Get the block in question. */
  77         bh = sb_bread(child_inode->i_sb, parent_block);
  78         if (bh == NULL) {
  79                 rv = ERR_PTR(-EACCES);
  80                 goto out;
  81         }
  82
  83         /* This is the "." entry. */
  84         de = (struct iso_directory_record*)bh->b_data;
  85
  86         /* The ".." entry is always the second entry. */
  87         parent_offset = (unsigned long)isonum_711(de->length);
  88         de = (struct iso_directory_record*)(bh->b_data + parent_offset);
  89
  90         /* Verify it is in fact the ".." entry. */
  91         if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) {
  92                 printk(KERN_ERR "isofs: Unable to find the \"..\" "
  93                        "directory for NFS.\n");
  94                 rv = ERR_PTR(-EACCES);
  95                 goto out;
  96         }
  97
  98         /* Normalize */
  99         isofs_normalize_block_and_offset(de, &parent_block, &parent_offset);
 100
 101         rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block,
 102                                      parent_offset));
 103  out:
 104         if (bh)
 105                 brelse(bh);
 106         return rv;
 107 }
 108
 109 static int
 110 isofs_export_encode_fh(struct inode *inode,
 111                        __u32 *fh32,
 112                        int *max_len,
 113                        struct inode *parent)
 114 {
 115         struct iso_inode_info * ei = ISOFS_I(inode);
 116         int len = *max_len;
 117         int type = 1;
 118         __u16 *fh16 = (__u16*)fh32;
 119
 120         /*
 121          * WARNING: max_len is 5 for NFSv2.  Because of this
 122          * limitation, we use the lower 16 bits of fh32[1] to hold the
 123          * offset of the inode and the upper 16 bits of fh32[1] to
 124          * hold the offset of the parent.
 125          */
 126         if (parent && (len < 5)) {
 127                 *max_len = 5;
 128                 return FILEID_INVALID;
 129         } else if (len < 3) {
 130                 *max_len = 3;
 131                 return FILEID_INVALID;
 132         }
 133
 134         len = 3;
 135         fh32[0] = ei->i_iget5_block;
 136         fh16[2] = (__u16)ei->i_iget5_offset;  /* fh16 [sic] */
 137         fh16[3] = 0;  /* avoid leaking uninitialized data */
 138         fh32[2] = inode->i_generation;
 139         if (parent) {
 140                 struct iso_inode_info *eparent;
 141                 eparent = ISOFS_I(parent);
 142                 fh32[3] = eparent->i_iget5_block;
 143                 fh16[3] = (__u16)eparent->i_iget5_offset;  /* fh16 [sic] */
 144                 fh32[4] = parent->i_generation;
 145                 len = 5;
 146                 type = 2;
 147         }
 148         *max_len = len;
 149         return type;
 150 }
 151
 152 struct isofs_fid {
 153         u32 block;
 154         u16 offset;
 155         u16 parent_offset;
 156         u32 generation;
 157         u32 parent_block;
 158         u32 parent_generation;
 159 };
 160
 161 static struct dentry *isofs_fh_to_dentry(struct super_block *sb,
 162         struct fid *fid, int fh_len, int fh_type)
 163 {
 164         struct isofs_fid *ifid = (struct isofs_fid *)fid;
 165
 166         if (fh_len < 3 || fh_type > 2)
 167                 return NULL;
 168
 169         return isofs_export_iget(sb, ifid->block, ifid->offset,
 170                         ifid->generation);
 171 }
 172
 173 static struct dentry *isofs_fh_to_parent(struct super_block *sb,
 174                 struct fid *fid, int fh_len, int fh_type)
 175 {
 176         struct isofs_fid *ifid = (struct isofs_fid *)fid;
 177
 178         if (fh_len < 2 || fh_type != 2)
 179                 return NULL;
 180
 181         return isofs_export_iget(sb,
 182                         fh_len > 2 ? ifid->parent_block : 0,
 183                         ifid->parent_offset,
 184                         fh_len > 4 ? ifid->parent_generation : 0);
 185 }
 186
 187 const struct export_operations isofs_export_ops = {
 188         .encode_fh      = isofs_export_encode_fh,
 189         .fh_to_dentry   = isofs_fh_to_dentry,
 190         .fh_to_parent   = isofs_fh_to_parent,
 191         .get_parent     = isofs_export_get_parent,
 192 };