1 2 #include <linux/fs.h> 3 #include <linux/file.h> 4 #include <linux/module.h> 5 #include <linux/smp_lock.h> 6 #include <linux/namei.h> 7 8 struct export_operations export_op_default; 9 10 #define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun) 11 12 #define dprintk(fmt, args...) do{}while(0) 13 14 static struct dentry * 15 find_acceptable_alias(struct dentry *result, 16 int (*acceptable)(void *context, struct dentry *dentry), 17 void *context) 18 { 19 struct dentry *dentry, *toput = NULL; 20 21 spin_lock(&dcache_lock); 22 list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) { 23 dget_locked(dentry); 24 spin_unlock(&dcache_lock); 25 if (toput) 26 dput(toput); 27 if (dentry != result && acceptable(context, dentry)) { 28 dput(result); 29 return dentry; 30 } 31 spin_lock(&dcache_lock); 32 toput = dentry; 33 } 34 spin_unlock(&dcache_lock); 35 36 if (toput) 37 dput(toput); 38 return NULL; 39 } 40 41 /** 42 * find_exported_dentry - helper routine to implement export_operations->decode_fh 43 * @sb: The &super_block identifying the filesystem 44 * @obj: An opaque identifier of the object to be found - passed to 45 * get_inode 46 * @parent: An optional opqaue identifier of the parent of the object. 47 * @acceptable: A function used to test possible &dentries to see if they are 48 * acceptable 49 * @context: A parameter to @acceptable so that it knows on what basis to 50 * judge. 51 * 52 * find_exported_dentry is the central helper routine to enable file systems 53 * to provide the decode_fh() export_operation. It's main task is to take 54 * an &inode, find or create an appropriate &dentry structure, and possibly 55 * splice this into the dcache in the correct place. 56 * 57 * The decode_fh() operation provided by the filesystem should call 58 * find_exported_dentry() with the same parameters that it received except 59 * that instead of the file handle fragment, pointers to opaque identifiers 60 * for the object and optionally its parent are passed. The default decode_fh 61 * routine passes one pointer to the start of the filehandle fragment, and 62 * one 8 bytes into the fragment. It is expected that most filesystems will 63 * take this approach, though the offset to the parent identifier may well be 64 * different. 65 * 66 * find_exported_dentry() will call get_dentry to get an dentry pointer from 67 * the file system. If any &dentry in the d_alias list is acceptable, it will 68 * be returned. Otherwise find_exported_dentry() will attempt to splice a new 69 * &dentry into the dcache using get_name() and get_parent() to find the 70 * appropriate place. 71 */ 72 73 struct dentry * 74 find_exported_dentry(struct super_block *sb, void *obj, void *parent, 75 int (*acceptable)(void *context, struct dentry *de), 76 void *context) 77 { 78 struct dentry *result = NULL; 79 struct dentry *target_dir; 80 int err; 81 struct export_operations *nops = sb->s_export_op; 82 struct dentry *alias; 83 int noprogress; 84 char nbuf[NAME_MAX+1]; 85 86 /* 87 * Attempt to find the inode. 88 */ 89 result = CALL(sb->s_export_op,get_dentry)(sb,obj); 90 err = -ESTALE; 91 if (result == NULL) 92 goto err_out; 93 if (IS_ERR(result)) { 94 err = PTR_ERR(result); 95 goto err_out; 96 } 97 if (S_ISDIR(result->d_inode->i_mode) && 98 (result->d_flags & DCACHE_DISCONNECTED)) { 99 /* it is an unconnected directory, we must connect it */ 100 ; 101 } else { 102 if (acceptable(context, result)) 103 return result; 104 if (S_ISDIR(result->d_inode->i_mode)) { 105 /* there is no other dentry, so fail */ 106 goto err_result; 107 } 108 109 alias = find_acceptable_alias(result, acceptable, context); 110 if (alias) 111 return alias; 112 } 113 114 /* It's a directory, or we are required to confirm the file's 115 * location in the tree based on the parent information 116 */ 117 dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj); 118 if (S_ISDIR(result->d_inode->i_mode)) 119 target_dir = dget(result); 120 else { 121 if (parent == NULL) 122 goto err_result; 123 124 target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent); 125 if (IS_ERR(target_dir)) 126 err = PTR_ERR(target_dir); 127 if (target_dir == NULL || IS_ERR(target_dir)) 128 goto err_result; 129 } 130 /* 131 * Now we need to make sure that target_dir is properly connected. 132 * It may already be, as the flag isn't always updated when connection 133 * happens. 134 * So, we walk up parent links until we find a connected directory, 135 * or we run out of directories. Then we find the parent, find 136 * the name of the child in that parent, and do a lookup. 137 * This should connect the child into the parent 138 * We then repeat. 139 */ 140 141 /* it is possible that a confused file system might not let us complete 142 * the path to the root. For example, if get_parent returns a directory 143 * in which we cannot find a name for the child. While this implies a 144 * very sick filesystem we don't want it to cause knfsd to spin. Hence 145 * the noprogress counter. If we go through the loop 10 times (2 is 146 * probably enough) without getting anywhere, we just give up 147 */ 148 noprogress= 0; 149 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { 150 struct dentry *pd = target_dir; 151 152 dget(pd); 153 spin_lock(&pd->d_lock); 154 while (!IS_ROOT(pd) && 155 (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) { 156 struct dentry *parent = pd->d_parent; 157 158 dget(parent); 159 spin_unlock(&pd->d_lock); 160 dput(pd); 161 pd = parent; 162 spin_lock(&pd->d_lock); 163 } 164 spin_unlock(&pd->d_lock); 165 166 if (!IS_ROOT(pd)) { 167 /* must have found a connected parent - great */ 168 spin_lock(&pd->d_lock); 169 pd->d_flags &= ~DCACHE_DISCONNECTED; 170 spin_unlock(&pd->d_lock); 171 noprogress = 0; 172 } else if (pd == sb->s_root) { 173 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); 174 spin_lock(&pd->d_lock); 175 pd->d_flags &= ~DCACHE_DISCONNECTED; 176 spin_unlock(&pd->d_lock); 177 noprogress = 0; 178 } else { 179 /* we have hit the top of a disconnected path. Try 180 * to find parent and connect 181 * note: racing with some other process renaming a 182 * directory isn't much of a problem here. If someone 183 * renames the directory, it will end up properly 184 * connected, which is what we want 185 */ 186 struct dentry *ppd; 187 struct dentry *npd; 188 189 mutex_lock(&pd->d_inode->i_mutex); 190 ppd = CALL(nops,get_parent)(pd); 191 mutex_unlock(&pd->d_inode->i_mutex); 192 193 if (IS_ERR(ppd)) { 194 err = PTR_ERR(ppd); 195 dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n", 196 pd->d_inode->i_ino, err); 197 dput(pd); 198 break; 199 } 200 dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino); 201 err = CALL(nops,get_name)(ppd, nbuf, pd); 202 if (err) { 203 dput(ppd); 204 dput(pd); 205 if (err == -ENOENT) 206 /* some race between get_parent and 207 * get_name? just try again 208 */ 209 continue; 210 break; 211 } 212 dprintk("find_exported_dentry: found name: %s\n", nbuf); 213 mutex_lock(&ppd->d_inode->i_mutex); 214 npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); 215 mutex_unlock(&ppd->d_inode->i_mutex); 216 if (IS_ERR(npd)) { 217 err = PTR_ERR(npd); 218 dprintk("find_exported_dentry: lookup failed: %d\n", err); 219 dput(ppd); 220 dput(pd); 221 break; 222 } 223 /* we didn't really want npd, we really wanted 224 * a side-effect of the lookup. 225 * hopefully, npd == pd, though it isn't really 226 * a problem if it isn't 227 */ 228 if (npd == pd) 229 noprogress = 0; 230 else 231 printk("find_exported_dentry: npd != pd\n"); 232 dput(npd); 233 dput(ppd); 234 if (IS_ROOT(pd)) { 235 /* something went wrong, we have to give up */ 236 dput(pd); 237 break; 238 } 239 } 240 dput(pd); 241 } 242 243 if (target_dir->d_flags & DCACHE_DISCONNECTED) { 244 /* something went wrong - oh-well */ 245 if (!err) 246 err = -ESTALE; 247 goto err_target; 248 } 249 /* if we weren't after a directory, have one more step to go */ 250 if (result != target_dir) { 251 struct dentry *nresult; 252 err = CALL(nops,get_name)(target_dir, nbuf, result); 253 if (!err) { 254 mutex_lock(&target_dir->d_inode->i_mutex); 255 nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf)); 256 mutex_unlock(&target_dir->d_inode->i_mutex); 257 if (!IS_ERR(nresult)) { 258 if (nresult->d_inode) { 259 dput(result); 260 result = nresult; 261 } else 262 dput(nresult); 263 } 264 } 265 } 266 dput(target_dir); 267 /* now result is properly connected, it is our best bet */ 268 if (acceptable(context, result)) 269 return result; 270 271 alias = find_acceptable_alias(result, acceptable, context); 272 if (alias) 273 return alias; 274 275 /* drat - I just cannot find anything acceptable */ 276 dput(result); 277 /* It might be justifiable to return ESTALE here, 278 * but the filehandle at-least looks reasonable good 279 * and it just be a permission problem, so returning 280 * -EACCESS is safer 281 */ 282 return ERR_PTR(-EACCES); 283 284 err_target: 285 dput(target_dir); 286 err_result: 287 dput(result); 288 err_out: 289 return ERR_PTR(err); 290 } 291 292 293 294 static struct dentry *get_parent(struct dentry *child) 295 { 296 /* get_parent cannot be supported generically, the locking 297 * is too icky. 298 * instead, we just return EACCES. If server reboots or inodes 299 * get flushed, you lose 300 */ 301 return ERR_PTR(-EACCES); 302 } 303 304 305 struct getdents_callback { 306 char *name; /* name that was found. It already points to a 307 buffer NAME_MAX+1 is size */ 308 unsigned long ino; /* the inum we are looking for */ 309 int found; /* inode matched? */ 310 int sequence; /* sequence counter */ 311 }; 312 313 /* 314 * A rather strange filldir function to capture 315 * the name matching the specified inode number. 316 */ 317 static int filldir_one(void * __buf, const char * name, int len, 318 loff_t pos, ino_t ino, unsigned int d_type) 319 { 320 struct getdents_callback *buf = __buf; 321 int result = 0; 322 323 buf->sequence++; 324 if (buf->ino == ino) { 325 memcpy(buf->name, name, len); 326 buf->name[len] = '\0'; 327 buf->found = 1; 328 result = -1; 329 } 330 return result; 331 } 332 333 /** 334 * get_name - default export_operations->get_name function 335 * @dentry: the directory in which to find a name 336 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name 337 * @child: the dentry for the child directory. 338 * 339 * calls readdir on the parent until it finds an entry with 340 * the same inode number as the child, and returns that. 341 */ 342 static int get_name(struct dentry *dentry, char *name, 343 struct dentry *child) 344 { 345 struct inode *dir = dentry->d_inode; 346 int error; 347 struct file *file; 348 struct getdents_callback buffer; 349 350 error = -ENOTDIR; 351 if (!dir || !S_ISDIR(dir->i_mode)) 352 goto out; 353 error = -EINVAL; 354 if (!dir->i_fop) 355 goto out; 356 /* 357 * Open the directory ... 358 */ 359 file = dentry_open(dget(dentry), NULL, O_RDONLY); 360 error = PTR_ERR(file); 361 if (IS_ERR(file)) 362 goto out; 363 364 error = -EINVAL; 365 if (!file->f_op->readdir) 366 goto out_close; 367 368 buffer.name = name; 369 buffer.ino = child->d_inode->i_ino; 370 buffer.found = 0; 371 buffer.sequence = 0; 372 while (1) { 373 int old_seq = buffer.sequence; 374 375 error = vfs_readdir(file, filldir_one, &buffer); 376 377 if (error < 0) 378 break; 379 380 error = 0; 381 if (buffer.found) 382 break; 383 error = -ENOENT; 384 if (old_seq == buffer.sequence) 385 break; 386 } 387 388 out_close: 389 fput(file); 390 out: 391 return error; 392 } 393 394 395 static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation) 396 { 397 398 /* iget isn't really right if the inode is currently unallocated!! 399 * This should really all be done inside each filesystem 400 * 401 * ext2fs' read_inode has been strengthed to return a bad_inode if 402 * the inode had been deleted. 403 * 404 * Currently we don't know the generation for parent directory, so 405 * a generation of 0 means "accept any" 406 */ 407 struct inode *inode; 408 struct dentry *result; 409 if (ino == 0) 410 return ERR_PTR(-ESTALE); 411 inode = iget(sb, ino); 412 if (inode == NULL) 413 return ERR_PTR(-ENOMEM); 414 if (is_bad_inode(inode) 415 || (generation && inode->i_generation != generation) 416 ) { 417 /* we didn't find the right inode.. */ 418 dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n", 419 inode->i_ino, 420 inode->i_nlink, atomic_read(&inode->i_count), 421 inode->i_generation, 422 generation); 423 424 iput(inode); 425 return ERR_PTR(-ESTALE); 426 } 427 /* now to find a dentry. 428 * If possible, get a well-connected one 429 */ 430 result = d_alloc_anon(inode); 431 if (!result) { 432 iput(inode); 433 return ERR_PTR(-ENOMEM); 434 } 435 return result; 436 } 437 438 439 static struct dentry *get_object(struct super_block *sb, void *vobjp) 440 { 441 __u32 *objp = vobjp; 442 unsigned long ino = objp[0]; 443 __u32 generation = objp[1]; 444 445 return export_iget(sb, ino, generation); 446 } 447 448 449 /** 450 * export_encode_fh - default export_operations->encode_fh function 451 * @dentry: the dentry to encode 452 * @fh: where to store the file handle fragment 453 * @max_len: maximum length to store there 454 * @connectable: whether to store parent information 455 * 456 * This default encode_fh function assumes that the 32 inode number 457 * is suitable for locating an inode, and that the generation number 458 * can be used to check that it is still valid. It places them in the 459 * filehandle fragment where export_decode_fh expects to find them. 460 */ 461 static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, 462 int connectable) 463 { 464 struct inode * inode = dentry->d_inode; 465 int len = *max_len; 466 int type = 1; 467 468 if (len < 2 || (connectable && len < 4)) 469 return 255; 470 471 len = 2; 472 fh[0] = inode->i_ino; 473 fh[1] = inode->i_generation; 474 if (connectable && !S_ISDIR(inode->i_mode)) { 475 struct inode *parent; 476 477 spin_lock(&dentry->d_lock); 478 parent = dentry->d_parent->d_inode; 479 fh[2] = parent->i_ino; 480 fh[3] = parent->i_generation; 481 spin_unlock(&dentry->d_lock); 482 len = 4; 483 type = 2; 484 } 485 *max_len = len; 486 return type; 487 } 488 489 490 /** 491 * export_decode_fh - default export_operations->decode_fh function 492 * @sb: The superblock 493 * @fh: pointer to the file handle fragment 494 * @fh_len: length of file handle fragment 495 * @acceptable: function for testing acceptability of dentrys 496 * @context: context for @acceptable 497 * 498 * This is the default decode_fh() function. 499 * a fileid_type of 1 indicates that the filehandlefragment 500 * just contains an object identifier understood by get_dentry. 501 * a fileid_type of 2 says that there is also a directory 502 * identifier 8 bytes in to the filehandlefragement. 503 */ 504 static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len, 505 int fileid_type, 506 int (*acceptable)(void *context, struct dentry *de), 507 void *context) 508 { 509 __u32 parent[2]; 510 parent[0] = parent[1] = 0; 511 if (fh_len < 2 || fileid_type > 2) 512 return NULL; 513 if (fileid_type == 2) { 514 if (fh_len > 2) parent[0] = fh[2]; 515 if (fh_len > 3) parent[1] = fh[3]; 516 } 517 return find_exported_dentry(sb, fh, parent, 518 acceptable, context); 519 } 520 521 struct export_operations export_op_default = { 522 .decode_fh = export_decode_fh, 523 .encode_fh = export_encode_fh, 524 525 .get_name = get_name, 526 .get_parent = get_parent, 527 .get_dentry = get_object, 528 }; 529 530 EXPORT_SYMBOL(export_op_default); 531 EXPORT_SYMBOL(find_exported_dentry); 532 533 MODULE_LICENSE("GPL"); 534