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 }; 193