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/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         struct dentry *result;
  26         if (block == 0)
  27                 return ERR_PTR(-ESTALE);
  28         inode = isofs_iget(sb, block, offset);
  29         if (inode == NULL)
  30                 return ERR_PTR(-ENOMEM);
  31         if (is_bad_inode(inode)
  32             || (generation && inode->i_generation != generation))
  33         {
  34                 iput(inode);
  35                 return ERR_PTR(-ESTALE);
  36         }
  37         result = d_alloc_anon(inode);
  38         if (!result) {
  39                 iput(inode);
  40                 return ERR_PTR(-ENOMEM);
  41         }
  42         return result;
  43 }
  44
  45 static struct dentry *
  46 isofs_export_get_dentry(struct super_block *sb, void *vobjp)
  47 {
  48         __u32 *objp = vobjp;
  49         unsigned long block = objp[0];
  50         unsigned long offset = objp[1];
  51         __u32 generation = objp[2];
  52         return isofs_export_iget(sb, block, offset, generation);
  53 }
  54
  55 /* This function is surprisingly simple.  The trick is understanding
  56  * that "child" is always a directory. So, to find its parent, you
  57  * simply need to find its ".." entry, normalize its block and offset,
  58  * and return the underlying inode.  See the comments for
  59  * isofs_normalize_block_and_offset(). */
  60 static struct dentry *isofs_export_get_parent(struct dentry *child)
  61 {
  62         unsigned long parent_block = 0;
  63         unsigned long parent_offset = 0;
  64         struct inode *child_inode = child->d_inode;
  65         struct iso_inode_info *e_child_inode = ISOFS_I(child_inode);
  66         struct inode *parent_inode = NULL;
  67         struct iso_directory_record *de = NULL;
  68         struct buffer_head * bh = NULL;
  69         struct dentry *rv = NULL;
  70
  71         /* "child" must always be a directory. */
  72         if (!S_ISDIR(child_inode->i_mode)) {
  73                 printk(KERN_ERR "isofs: isofs_export_get_parent(): "
  74                        "child is not a directory!\n");
  75                 rv = ERR_PTR(-EACCES);
  76                 goto out;
  77         }
  78
  79         /* It is an invariant that the directory offset is zero.  If
  80          * it is not zero, it means the directory failed to be
  81          * normalized for some reason. */
  82         if (e_child_inode->i_iget5_offset != 0) {
  83                 printk(KERN_ERR "isofs: isofs_export_get_parent(): "
  84                        "child directory not normalized!\n");
  85                 rv = ERR_PTR(-EACCES);
  86                 goto out;
  87         }
  88
  89         /* The child inode has been normalized such that its
  90          * i_iget5_block value points to the "." entry.  Fortunately,
  91          * the ".." entry is located in the same block. */
  92         parent_block = e_child_inode->i_iget5_block;
  93
  94         /* Get the block in question. */
  95         bh = sb_bread(child_inode->i_sb, parent_block);
  96         if (bh == NULL) {
  97                 rv = ERR_PTR(-EACCES);
  98                 goto out;
  99         }
 100
 101         /* This is the "." entry. */
 102         de = (struct iso_directory_record*)bh->b_data;
 103
 104         /* The ".." entry is always the second entry. */
 105         parent_offset = (unsigned long)isonum_711(de->length);
 106         de = (struct iso_directory_record*)(bh->b_data + parent_offset);
 107
 108         /* Verify it is in fact the ".." entry. */
 109         if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) {
 110                 printk(KERN_ERR "isofs: Unable to find the \"..\" "
 111                        "directory for NFS.\n");
 112                 rv = ERR_PTR(-EACCES);
 113                 goto out;
 114         }
 115
 116         /* Normalize */
 117         isofs_normalize_block_and_offset(de, &parent_block, &parent_offset);
 118
 119         /* Get the inode. */
 120         parent_inode = isofs_iget(child_inode->i_sb,
 121                                   parent_block,
 122                                   parent_offset);
 123         if (parent_inode == NULL) {
 124                 rv = ERR_PTR(-EACCES);
 125                 goto out;
 126         }
 127
 128         /* Allocate the dentry. */
 129         rv = d_alloc_anon(parent_inode);
 130         if (rv == NULL) {
 131                 rv = ERR_PTR(-ENOMEM);
 132                 goto out;
 133         }
 134
 135  out:
 136         if (bh) {
 137                 brelse(bh);
 138         }
 139         return rv;
 140 }
 141
 142 static int
 143 isofs_export_encode_fh(struct dentry *dentry,
 144                        __u32 *fh32,
 145                        int *max_len,
 146                        int connectable)
 147 {
 148         struct inode * inode = dentry->d_inode;
 149         struct iso_inode_info * ei = ISOFS_I(inode);
 150         int len = *max_len;
 151         int type = 1;
 152         __u16 *fh16 = (__u16*)fh32;
 153
 154         /*
 155          * WARNING: max_len is 5 for NFSv2.  Because of this
 156          * limitation, we use the lower 16 bits of fh32[1] to hold the
 157          * offset of the inode and the upper 16 bits of fh32[1] to
 158          * hold the offset of the parent.
 159          */
 160
 161         if (len < 3 || (connectable && len < 5))
 162                 return 255;
 163
 164         len = 3;
 165         fh32[0] = ei->i_iget5_block;
 166         fh16[2] = (__u16)ei->i_iget5_offset;  /* fh16 [sic] */
 167         fh32[2] = inode->i_generation;
 168         if (connectable && !S_ISDIR(inode->i_mode)) {
 169                 struct inode *parent;
 170                 struct iso_inode_info *eparent;
 171                 spin_lock(&dentry->d_lock);
 172                 parent = dentry->d_parent->d_inode;
 173                 eparent = ISOFS_I(parent);
 174                 fh32[3] = eparent->i_iget5_block;
 175                 fh16[3] = (__u16)eparent->i_iget5_offset;  /* fh16 [sic] */
 176                 fh32[4] = parent->i_generation;
 177                 spin_unlock(&dentry->d_lock);
 178                 len = 5;
 179                 type = 2;
 180         }
 181         *max_len = len;
 182         return type;
 183 }
 184
 185
 186 static struct dentry *
 187 isofs_export_decode_fh(struct super_block *sb,
 188                        __u32 *fh32,
 189                        int fh_len,
 190                        int fileid_type,
 191                        int (*acceptable)(void *context, struct dentry *de),
 192                        void *context)
 193 {
 194         __u16 *fh16 = (__u16*)fh32;
 195         __u32 child[3];   /* The child is what triggered all this. */
 196         __u32 parent[3];  /* The parent is just along for the ride. */
 197
 198         if (fh_len < 3 || fileid_type > 2)
 199                 return NULL;
 200
 201         child[0] = fh32[0];
 202         child[1] = fh16[2];  /* fh16 [sic] */
 203         child[2] = fh32[2];
 204
 205         parent[0] = 0;
 206         parent[1] = 0;
 207         parent[2] = 0;
 208         if (fileid_type == 2) {
 209                 if (fh_len > 2) parent[0] = fh32[3];
 210                 parent[1] = fh16[3];  /* fh16 [sic] */
 211                 if (fh_len > 4) parent[2] = fh32[4];
 212         }
 213
 214         return sb->s_export_op->find_exported_dentry(sb, child, parent,
 215                                                      acceptable, context);
 216 }
 217
 218
 219 struct export_operations isofs_export_ops = {
 220         .decode_fh      = isofs_export_decode_fh,
 221         .encode_fh      = isofs_export_encode_fh,
 222         .get_dentry     = isofs_export_get_dentry,
 223         .get_parent     = isofs_export_get_parent,
 224 };