1 // SPDX-License-Identifier: GPL-2.0-only 2 /* fs/fat/nfs.c 3 */ 4 5 #include <linux/exportfs.h> 6 #include "fat.h" 7 8 struct fat_fid { 9 u32 i_gen; 10 u32 i_pos_low; 11 u16 i_pos_hi; 12 u16 parent_i_pos_hi; 13 u32 parent_i_pos_low; 14 u32 parent_i_gen; 15 }; 16 17 #define FAT_FID_SIZE_WITHOUT_PARENT 3 18 #define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32)) 19 20 /* 21 * Look up a directory inode given its starting cluster. 22 */ 23 static struct inode *fat_dget(struct super_block *sb, int i_logstart) 24 { 25 struct msdos_sb_info *sbi = MSDOS_SB(sb); 26 struct hlist_head *head; 27 struct msdos_inode_info *i; 28 struct inode *inode = NULL; 29 30 head = sbi->dir_hashtable + fat_dir_hash(i_logstart); 31 spin_lock(&sbi->dir_hash_lock); 32 hlist_for_each_entry(i, head, i_dir_hash) { 33 BUG_ON(i->vfs_inode.i_sb != sb); 34 if (i->i_logstart != i_logstart) 35 continue; 36 inode = igrab(&i->vfs_inode); 37 if (inode) 38 break; 39 } 40 spin_unlock(&sbi->dir_hash_lock); 41 return inode; 42 } 43 44 static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos) 45 { 46 if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) 47 return fat_iget(sb, i_pos); 48 49 else { 50 if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO)) 51 return NULL; 52 return ilookup(sb, ino); 53 } 54 } 55 56 static struct inode *__fat_nfs_get_inode(struct super_block *sb, 57 u64 ino, u32 generation, loff_t i_pos) 58 { 59 struct inode *inode = fat_ilookup(sb, ino, i_pos); 60 61 if (inode && generation && (inode->i_generation != generation)) { 62 iput(inode); 63 inode = NULL; 64 } 65 if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) { 66 struct buffer_head *bh = NULL; 67 struct msdos_dir_entry *de ; 68 sector_t blocknr; 69 int offset; 70 fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset); 71 bh = sb_bread(sb, blocknr); 72 if (!bh) { 73 fat_msg(sb, KERN_ERR, 74 "unable to read block(%llu) for building NFS inode", 75 (llu)blocknr); 76 return inode; 77 } 78 de = (struct msdos_dir_entry *)bh->b_data; 79 /* If a file is deleted on server and client is not updated 80 * yet, we must not build the inode upon a lookup call. 81 */ 82 if (IS_FREE(de[offset].name)) 83 inode = NULL; 84 else 85 inode = fat_build_inode(sb, &de[offset], i_pos); 86 brelse(bh); 87 } 88 89 return inode; 90 } 91 92 static struct inode *fat_nfs_get_inode(struct super_block *sb, 93 u64 ino, u32 generation) 94 { 95 96 return __fat_nfs_get_inode(sb, ino, generation, 0); 97 } 98 99 static int 100 fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp, 101 struct inode *parent) 102 { 103 int len = *lenp; 104 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb); 105 struct fat_fid *fid = (struct fat_fid *) fh; 106 loff_t i_pos; 107 int type = FILEID_FAT_WITHOUT_PARENT; 108 109 if (parent) { 110 if (len < FAT_FID_SIZE_WITH_PARENT) { 111 *lenp = FAT_FID_SIZE_WITH_PARENT; 112 return FILEID_INVALID; 113 } 114 } else { 115 if (len < FAT_FID_SIZE_WITHOUT_PARENT) { 116 *lenp = FAT_FID_SIZE_WITHOUT_PARENT; 117 return FILEID_INVALID; 118 } 119 } 120 121 i_pos = fat_i_pos_read(sbi, inode); 122 *lenp = FAT_FID_SIZE_WITHOUT_PARENT; 123 fid->i_gen = inode->i_generation; 124 fid->i_pos_low = i_pos & 0xFFFFFFFF; 125 fid->i_pos_hi = (i_pos >> 32) & 0xFFFF; 126 if (parent) { 127 i_pos = fat_i_pos_read(sbi, parent); 128 fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF; 129 fid->parent_i_pos_low = i_pos & 0xFFFFFFFF; 130 fid->parent_i_gen = parent->i_generation; 131 type = FILEID_FAT_WITH_PARENT; 132 *lenp = FAT_FID_SIZE_WITH_PARENT; 133 } 134 135 return type; 136 } 137 138 /* 139 * Map a NFS file handle to a corresponding dentry. 140 * The dentry may or may not be connected to the filesystem root. 141 */ 142 static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid, 143 int fh_len, int fh_type) 144 { 145 return generic_fh_to_dentry(sb, fid, fh_len, fh_type, 146 fat_nfs_get_inode); 147 } 148 149 static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb, 150 struct fid *fh, int fh_len, 151 int fh_type) 152 { 153 struct inode *inode = NULL; 154 struct fat_fid *fid = (struct fat_fid *)fh; 155 loff_t i_pos; 156 157 switch (fh_type) { 158 case FILEID_FAT_WITHOUT_PARENT: 159 if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT) 160 return NULL; 161 break; 162 case FILEID_FAT_WITH_PARENT: 163 if (fh_len < FAT_FID_SIZE_WITH_PARENT) 164 return NULL; 165 break; 166 default: 167 return NULL; 168 } 169 i_pos = fid->i_pos_hi; 170 i_pos = (i_pos << 32) | (fid->i_pos_low); 171 inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos); 172 173 return d_obtain_alias(inode); 174 } 175 176 /* 177 * Find the parent for a file specified by NFS handle. 178 * This requires that the handle contain the i_ino of the parent. 179 */ 180 static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid, 181 int fh_len, int fh_type) 182 { 183 return generic_fh_to_parent(sb, fid, fh_len, fh_type, 184 fat_nfs_get_inode); 185 } 186 187 static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb, 188 struct fid *fh, int fh_len, 189 int fh_type) 190 { 191 struct inode *inode = NULL; 192 struct fat_fid *fid = (struct fat_fid *)fh; 193 loff_t i_pos; 194 195 if (fh_len < FAT_FID_SIZE_WITH_PARENT) 196 return NULL; 197 198 switch (fh_type) { 199 case FILEID_FAT_WITH_PARENT: 200 i_pos = fid->parent_i_pos_hi; 201 i_pos = (i_pos << 32) | (fid->parent_i_pos_low); 202 inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos); 203 break; 204 } 205 206 return d_obtain_alias(inode); 207 } 208 209 /* 210 * Rebuild the parent for a directory that is not connected 211 * to the filesystem root 212 */ 213 static 214 struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart) 215 { 216 int search_clus, clus_to_match; 217 struct msdos_dir_entry *de; 218 struct inode *parent = NULL; 219 struct inode *dummy_grand_parent = NULL; 220 struct fat_slot_info sinfo; 221 struct msdos_sb_info *sbi = MSDOS_SB(sb); 222 sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart); 223 struct buffer_head *parent_bh = sb_bread(sb, blknr); 224 if (!parent_bh) { 225 fat_msg(sb, KERN_ERR, 226 "unable to read cluster of parent directory"); 227 return NULL; 228 } 229 230 de = (struct msdos_dir_entry *) parent_bh->b_data; 231 clus_to_match = fat_get_start(sbi, &de[0]); 232 search_clus = fat_get_start(sbi, &de[1]); 233 234 dummy_grand_parent = fat_dget(sb, search_clus); 235 if (!dummy_grand_parent) { 236 dummy_grand_parent = new_inode(sb); 237 if (!dummy_grand_parent) { 238 brelse(parent_bh); 239 return parent; 240 } 241 242 dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO); 243 fat_fill_inode(dummy_grand_parent, &de[1]); 244 MSDOS_I(dummy_grand_parent)->i_pos = -1; 245 } 246 247 if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo)) 248 parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos); 249 250 brelse(parent_bh); 251 iput(dummy_grand_parent); 252 253 return parent; 254 } 255 256 /* 257 * Find the parent for a directory that is not currently connected to 258 * the filesystem root. 259 * 260 * On entry, the caller holds d_inode(child_dir)->i_mutex. 261 */ 262 static struct dentry *fat_get_parent(struct dentry *child_dir) 263 { 264 struct super_block *sb = child_dir->d_sb; 265 struct buffer_head *bh = NULL; 266 struct msdos_dir_entry *de; 267 struct inode *parent_inode = NULL; 268 struct msdos_sb_info *sbi = MSDOS_SB(sb); 269 270 if (!fat_get_dotdot_entry(d_inode(child_dir), &bh, &de)) { 271 int parent_logstart = fat_get_start(sbi, de); 272 parent_inode = fat_dget(sb, parent_logstart); 273 if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO) 274 parent_inode = fat_rebuild_parent(sb, parent_logstart); 275 } 276 brelse(bh); 277 278 return d_obtain_alias(parent_inode); 279 } 280 281 const struct export_operations fat_export_ops = { 282 .fh_to_dentry = fat_fh_to_dentry, 283 .fh_to_parent = fat_fh_to_parent, 284 .get_parent = fat_get_parent, 285 }; 286 287 const struct export_operations fat_export_ops_nostale = { 288 .encode_fh = fat_encode_fh_nostale, 289 .fh_to_dentry = fat_fh_to_dentry_nostale, 290 .fh_to_parent = fat_fh_to_parent_nostale, 291 .get_parent = fat_get_parent, 292 }; 293