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 /** 15 * find_exported_dentry - helper routine to implement export_operations->decode_fh 16 * @sb: The &super_block identifying the filesystem 17 * @obj: An opaque identifier of the object to be found - passed to 18 * get_inode 19 * @parent: An optional opqaue identifier of the parent of the object. 20 * @acceptable: A function used to test possible &dentries to see if they are 21 * acceptable 22 * @context: A parameter to @acceptable so that it knows on what basis to 23 * judge. 24 * 25 * find_exported_dentry is the central helper routine to enable file systems 26 * to provide the decode_fh() export_operation. It's main task is to take 27 * an &inode, find or create an appropriate &dentry structure, and possibly 28 * splice this into the dcache in the correct place. 29 * 30 * The decode_fh() operation provided by the filesystem should call 31 * find_exported_dentry() with the same parameters that it received except 32 * that instead of the file handle fragment, pointers to opaque identifiers 33 * for the object and optionally its parent are passed. The default decode_fh 34 * routine passes one pointer to the start of the filehandle fragment, and 35 * one 8 bytes into the fragment. It is expected that most filesystems will 36 * take this approach, though the offset to the parent identifier may well be 37 * different. 38 * 39 * find_exported_dentry() will call get_dentry to get an dentry pointer from 40 * the file system. If any &dentry in the d_alias list is acceptable, it will 41 * be returned. Otherwise find_exported_dentry() will attempt to splice a new 42 * &dentry into the dcache using get_name() and get_parent() to find the 43 * appropriate place. 44 */ 45 46 struct dentry * 47 find_exported_dentry(struct super_block *sb, void *obj, void *parent, 48 int (*acceptable)(void *context, struct dentry *de), 49 void *context) 50 { 51 struct dentry *result = NULL; 52 struct dentry *target_dir; 53 int err; 54 struct export_operations *nops = sb->s_export_op; 55 struct list_head *le, *head; 56 struct dentry *toput = NULL; 57 int noprogress; 58 char nbuf[NAME_MAX+1]; 59 60 /* 61 * Attempt to find the inode. 62 */ 63 result = CALL(sb->s_export_op,get_dentry)(sb,obj); 64 err = -ESTALE; 65 if (result == NULL) 66 goto err_out; 67 if (IS_ERR(result)) { 68 err = PTR_ERR(result); 69 goto err_out; 70 } 71 if (S_ISDIR(result->d_inode->i_mode) && 72 (result->d_flags & DCACHE_DISCONNECTED)) { 73 /* it is an unconnected directory, we must connect it */ 74 ; 75 } else { 76 if (acceptable(context, result)) 77 return result; 78 if (S_ISDIR(result->d_inode->i_mode)) { 79 /* there is no other dentry, so fail */ 80 goto err_result; 81 } 82 /* try any other aliases */ 83 spin_lock(&dcache_lock); 84 head = &result->d_inode->i_dentry; 85 list_for_each(le, head) { 86 struct dentry *dentry = list_entry(le, struct dentry, d_alias); 87 dget_locked(dentry); 88 spin_unlock(&dcache_lock); 89 if (toput) 90 dput(toput); 91 toput = NULL; 92 if (dentry != result && 93 acceptable(context, dentry)) { 94 dput(result); 95 return dentry; 96 } 97 spin_lock(&dcache_lock); 98 toput = dentry; 99 } 100 spin_unlock(&dcache_lock); 101 if (toput) 102 dput(toput); 103 } 104 105 /* It's a directory, or we are required to confirm the file's 106 * location in the tree based on the parent information 107 */ 108 dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj); 109 if (S_ISDIR(result->d_inode->i_mode)) 110 target_dir = dget(result); 111 else { 112 if (parent == NULL) 113 goto err_result; 114 115 target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent); 116 if (IS_ERR(target_dir)) 117 err = PTR_ERR(target_dir); 118 if (target_dir == NULL || IS_ERR(target_dir)) 119 goto err_result; 120 } 121 /* 122 * Now we need to make sure that target_dir is properly connected. 123 * It may already be, as the flag isn't always updated when connection 124 * happens. 125 * So, we walk up parent links until we find a connected directory, 126 * or we run out of directories. Then we find the parent, find 127 * the name of the child in that parent, and do a lookup. 128 * This should connect the child into the parent 129 * We then repeat. 130 */ 131 132 /* it is possible that a confused file system might not let us complete 133 * the path to the root. For example, if get_parent returns a directory 134 * in which we cannot find a name for the child. While this implies a 135 * very sick filesystem we don't want it to cause knfsd to spin. Hence 136 * the noprogress counter. If we go through the loop 10 times (2 is 137 * probably enough) without getting anywhere, we just give up 138 */ 139 noprogress= 0; 140 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { 141 struct dentry *pd = target_dir; 142 143 dget(pd); 144 spin_lock(&pd->d_lock); 145 while (!IS_ROOT(pd) && 146 (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) { 147 struct dentry *parent = pd->d_parent; 148 149 dget(parent); 150 spin_unlock(&pd->d_lock); 151 dput(pd); 152 pd = parent; 153 spin_lock(&pd->d_lock); 154 } 155 spin_unlock(&pd->d_lock); 156 157 if (!IS_ROOT(pd)) { 158 /* must have found a connected parent - great */ 159 spin_lock(&pd->d_lock); 160 pd->d_flags &= ~DCACHE_DISCONNECTED; 161 spin_unlock(&pd->d_lock); 162 noprogress = 0; 163 } else if (pd == sb->s_root) { 164 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); 165 spin_lock(&pd->d_lock); 166 pd->d_flags &= ~DCACHE_DISCONNECTED; 167 spin_unlock(&pd->d_lock); 168 noprogress = 0; 169 } else { 170 /* we have hit the top of a disconnected path. Try 171 * to find parent and connect 172 * note: racing with some other process renaming a 173 * directory isn't much of a problem here. If someone 174 * renames the directory, it will end up properly 175 * connected, which is what we want 176 */ 177 struct dentry *ppd; 178 struct dentry *npd; 179 180 mutex_lock(&pd->d_inode->i_mutex); 181 ppd = CALL(nops,get_parent)(pd); 182 mutex_unlock(&pd->d_inode->i_mutex); 183 184 if (IS_ERR(ppd)) { 185 err = PTR_ERR(ppd); 186 dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n", 187 pd->d_inode->i_ino, err); 188 dput(pd); 189 break; 190 } 191 dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino); 192 err = CALL(nops,get_name)(ppd, nbuf, pd); 193 if (err) { 194 dput(ppd); 195 dput(pd); 196 if (err == -ENOENT) 197 /* some race between get_parent and 198 * get_name? just try again 199 */ 200 continue; 201 break; 202 } 203 dprintk("find_exported_dentry: found name: %s\n", nbuf); 204 mutex_lock(&ppd->d_inode->i_mutex); 205 npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); 206 mutex_unlock(&ppd->d_inode->i_mutex); 207 if (IS_ERR(npd)) { 208 err = PTR_ERR(npd); 209 dprintk("find_exported_dentry: lookup failed: %d\n", err); 210 dput(ppd); 211 dput(pd); 212 break; 213 } 214 /* we didn't really want npd, we really wanted 215 * a side-effect of the lookup. 216 * hopefully, npd == pd, though it isn't really 217 * a problem if it isn't 218 */ 219 if (npd == pd) 220 noprogress = 0; 221 else 222 printk("find_exported_dentry: npd != pd\n"); 223 dput(npd); 224 dput(ppd); 225 if (IS_ROOT(pd)) { 226 /* something went wrong, we have to give up */ 227 dput(pd); 228 break; 229 } 230 } 231 dput(pd); 232 } 233 234 if (target_dir->d_flags & DCACHE_DISCONNECTED) { 235 /* something went wrong - oh-well */ 236 if (!err) 237 err = -ESTALE; 238 goto err_target; 239 } 240 /* if we weren't after a directory, have one more step to go */ 241 if (result != target_dir) { 242 struct dentry *nresult; 243 err = CALL(nops,get_name)(target_dir, nbuf, result); 244 if (!err) { 245 mutex_lock(&target_dir->d_inode->i_mutex); 246 nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf)); 247 mutex_unlock(&target_dir->d_inode->i_mutex); 248 if (!IS_ERR(nresult)) { 249 if (nresult->d_inode) { 250 dput(result); 251 result = nresult; 252 } else 253 dput(nresult); 254 } 255 } 256 } 257 dput(target_dir); 258 /* now result is properly connected, it is our best bet */ 259 if (acceptable(context, result)) 260 return result; 261 /* one last try of the aliases.. */ 262 spin_lock(&dcache_lock); 263 toput = NULL; 264 head = &result->d_inode->i_dentry; 265 list_for_each(le, head) { 266 struct dentry *dentry = list_entry(le, struct dentry, d_alias); 267 dget_locked(dentry); 268 spin_unlock(&dcache_lock); 269 if (toput) dput(toput); 270 if (dentry != result && 271 acceptable(context, dentry)) { 272 dput(result); 273 return dentry; 274 } 275 spin_lock(&dcache_lock); 276 toput = dentry; 277 } 278 spin_unlock(&dcache_lock); 279 if (toput) 280 dput(toput); 281 282 /* drat - I just cannot find anything acceptable */ 283 dput(result); 284 /* It might be justifiable to return ESTALE here, 285 * but the filehandle at-least looks reasonable good 286 * and it just be a permission problem, so returning 287 * -EACCESS is safer 288 */ 289 return ERR_PTR(-EACCES); 290 291 err_target: 292 dput(target_dir); 293 err_result: 294 dput(result); 295 err_out: 296 return ERR_PTR(err); 297 } 298 299 300 301 static struct dentry *get_parent(struct dentry *child) 302 { 303 /* get_parent cannot be supported generically, the locking 304 * is too icky. 305 * instead, we just return EACCES. If server reboots or inodes 306 * get flushed, you lose 307 */ 308 return ERR_PTR(-EACCES); 309 } 310 311 312 struct getdents_callback { 313 char *name; /* name that was found. It already points to a 314 buffer NAME_MAX+1 is size */ 315 unsigned long ino; /* the inum we are looking for */ 316 int found; /* inode matched? */ 317 int sequence; /* sequence counter */ 318 }; 319 320 /* 321 * A rather strange filldir function to capture 322 * the name matching the specified inode number. 323 */ 324 static int filldir_one(void * __buf, const char * name, int len, 325 loff_t pos, ino_t ino, unsigned int d_type) 326 { 327 struct getdents_callback *buf = __buf; 328 int result = 0; 329 330 buf->sequence++; 331 if (buf->ino == ino) { 332 memcpy(buf->name, name, len); 333 buf->name[len] = '\0'; 334 buf->found = 1; 335 result = -1; 336 } 337 return result; 338 } 339 340 /** 341 * get_name - default export_operations->get_name function 342 * @dentry: the directory in which to find a name 343 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name 344 * @child: the dentry for the child directory. 345 * 346 * calls readdir on the parent until it finds an entry with 347 * the same inode number as the child, and returns that. 348 */ 349 static int get_name(struct dentry *dentry, char *name, 350 struct dentry *child) 351 { 352 struct inode *dir = dentry->d_inode; 353 int error; 354 struct file *file; 355 struct getdents_callback buffer; 356 357 error = -ENOTDIR; 358 if (!dir || !S_ISDIR(dir->i_mode)) 359 goto out; 360 error = -EINVAL; 361 if (!dir->i_fop) 362 goto out; 363 /* 364 * Open the directory ... 365 */ 366 file = dentry_open(dget(dentry), NULL, O_RDONLY); 367 error = PTR_ERR(file); 368 if (IS_ERR(file)) 369 goto out; 370 371 error = -EINVAL; 372 if (!file->f_op->readdir) 373 goto out_close; 374 375 buffer.name = name; 376 buffer.ino = child->d_inode->i_ino; 377 buffer.found = 0; 378 buffer.sequence = 0; 379 while (1) { 380 int old_seq = buffer.sequence; 381 382 error = vfs_readdir(file, filldir_one, &buffer); 383 384 if (error < 0) 385 break; 386 387 error = 0; 388 if (buffer.found) 389 break; 390 error = -ENOENT; 391 if (old_seq == buffer.sequence) 392 break; 393 } 394 395 out_close: 396 fput(file); 397 out: 398 return error; 399 } 400 401 402 static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation) 403 { 404 405 /* iget isn't really right if the inode is currently unallocated!! 406 * This should really all be done inside each filesystem 407 * 408 * ext2fs' read_inode has been strengthed to return a bad_inode if 409 * the inode had been deleted. 410 * 411 * Currently we don't know the generation for parent directory, so 412 * a generation of 0 means "accept any" 413 */ 414 struct inode *inode; 415 struct dentry *result; 416 if (ino == 0) 417 return ERR_PTR(-ESTALE); 418 inode = iget(sb, ino); 419 if (inode == NULL) 420 return ERR_PTR(-ENOMEM); 421 if (is_bad_inode(inode) 422 || (generation && inode->i_generation != generation) 423 ) { 424 /* we didn't find the right inode.. */ 425 dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n", 426 inode->i_ino, 427 inode->i_nlink, atomic_read(&inode->i_count), 428 inode->i_generation, 429 generation); 430 431 iput(inode); 432 return ERR_PTR(-ESTALE); 433 } 434 /* now to find a dentry. 435 * If possible, get a well-connected one 436 */ 437 result = d_alloc_anon(inode); 438 if (!result) { 439 iput(inode); 440 return ERR_PTR(-ENOMEM); 441 } 442 return result; 443 } 444 445 446 static struct dentry *get_object(struct super_block *sb, void *vobjp) 447 { 448 __u32 *objp = vobjp; 449 unsigned long ino = objp[0]; 450 __u32 generation = objp[1]; 451 452 return export_iget(sb, ino, generation); 453 } 454 455 456 /** 457 * export_encode_fh - default export_operations->encode_fh function 458 * @dentry: the dentry to encode 459 * @fh: where to store the file handle fragment 460 * @max_len: maximum length to store there 461 * @connectable: whether to store parent information 462 * 463 * This default encode_fh function assumes that the 32 inode number 464 * is suitable for locating an inode, and that the generation number 465 * can be used to check that it is still valid. It places them in the 466 * filehandle fragment where export_decode_fh expects to find them. 467 */ 468 static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, 469 int connectable) 470 { 471 struct inode * inode = dentry->d_inode; 472 int len = *max_len; 473 int type = 1; 474 475 if (len < 2 || (connectable && len < 4)) 476 return 255; 477 478 len = 2; 479 fh[0] = inode->i_ino; 480 fh[1] = inode->i_generation; 481 if (connectable && !S_ISDIR(inode->i_mode)) { 482 struct inode *parent; 483 484 spin_lock(&dentry->d_lock); 485 parent = dentry->d_parent->d_inode; 486 fh[2] = parent->i_ino; 487 fh[3] = parent->i_generation; 488 spin_unlock(&dentry->d_lock); 489 len = 4; 490 type = 2; 491 } 492 *max_len = len; 493 return type; 494 } 495 496 497 /** 498 * export_decode_fh - default export_operations->decode_fh function 499 * @sb: The superblock 500 * @fh: pointer to the file handle fragment 501 * @fh_len: length of file handle fragment 502 * @acceptable: function for testing acceptability of dentrys 503 * @context: context for @acceptable 504 * 505 * This is the default decode_fh() function. 506 * a fileid_type of 1 indicates that the filehandlefragment 507 * just contains an object identifier understood by get_dentry. 508 * a fileid_type of 2 says that there is also a directory 509 * identifier 8 bytes in to the filehandlefragement. 510 */ 511 static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len, 512 int fileid_type, 513 int (*acceptable)(void *context, struct dentry *de), 514 void *context) 515 { 516 __u32 parent[2]; 517 parent[0] = parent[1] = 0; 518 if (fh_len < 2 || fileid_type > 2) 519 return NULL; 520 if (fileid_type == 2) { 521 if (fh_len > 2) parent[0] = fh[2]; 522 if (fh_len > 3) parent[1] = fh[3]; 523 } 524 return find_exported_dentry(sb, fh, parent, 525 acceptable, context); 526 } 527 528 struct export_operations export_op_default = { 529 .decode_fh = export_decode_fh, 530 .encode_fh = export_encode_fh, 531 532 .get_name = get_name, 533 .get_parent = get_parent, 534 .get_dentry = get_object, 535 }; 536 537 EXPORT_SYMBOL(export_op_default); 538 EXPORT_SYMBOL(find_exported_dentry); 539 540 MODULE_LICENSE("GPL"); 541