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Commit | Line | Data |
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1da177e4 | 1 | |
a5694255 | 2 | #include <linux/exportfs.h> |
1da177e4 LT |
3 | #include <linux/fs.h> |
4 | #include <linux/file.h> | |
5 | #include <linux/module.h> | |
d37065cd | 6 | #include <linux/mount.h> |
1da177e4 LT |
7 | #include <linux/namei.h> |
8 | ||
10f11c34 | 9 | #define dprintk(fmt, args...) do{}while(0) |
1da177e4 | 10 | |
1da177e4 | 11 | |
10f11c34 CH |
12 | static int get_name(struct dentry *dentry, char *name, |
13 | struct dentry *child); | |
14 | ||
15 | ||
16 | static struct dentry *exportfs_get_dentry(struct super_block *sb, void *obj) | |
17 | { | |
18 | struct dentry *result = ERR_PTR(-ESTALE); | |
19 | ||
20 | if (sb->s_export_op->get_dentry) { | |
21 | result = sb->s_export_op->get_dentry(sb, obj); | |
22 | if (!result) | |
23 | result = ERR_PTR(-ESTALE); | |
24 | } | |
25 | ||
26 | return result; | |
27 | } | |
28 | ||
29 | static int exportfs_get_name(struct dentry *dir, char *name, | |
30 | struct dentry *child) | |
31 | { | |
32 | struct export_operations *nop = dir->d_sb->s_export_op; | |
33 | ||
34 | if (nop->get_name) | |
35 | return nop->get_name(dir, name, child); | |
36 | else | |
37 | return get_name(dir, name, child); | |
38 | } | |
1da177e4 | 39 | |
fb66a198 CH |
40 | /* |
41 | * Check if the dentry or any of it's aliases is acceptable. | |
42 | */ | |
e2f99018 CH |
43 | static struct dentry * |
44 | find_acceptable_alias(struct dentry *result, | |
45 | int (*acceptable)(void *context, struct dentry *dentry), | |
46 | void *context) | |
47 | { | |
48 | struct dentry *dentry, *toput = NULL; | |
49 | ||
fb66a198 CH |
50 | if (acceptable(context, result)) |
51 | return result; | |
52 | ||
e2f99018 CH |
53 | spin_lock(&dcache_lock); |
54 | list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) { | |
55 | dget_locked(dentry); | |
56 | spin_unlock(&dcache_lock); | |
57 | if (toput) | |
58 | dput(toput); | |
59 | if (dentry != result && acceptable(context, dentry)) { | |
60 | dput(result); | |
61 | return dentry; | |
62 | } | |
63 | spin_lock(&dcache_lock); | |
64 | toput = dentry; | |
65 | } | |
66 | spin_unlock(&dcache_lock); | |
67 | ||
68 | if (toput) | |
69 | dput(toput); | |
70 | return NULL; | |
71 | } | |
72 | ||
dd90b509 CH |
73 | /* |
74 | * Find root of a disconnected subtree and return a reference to it. | |
75 | */ | |
76 | static struct dentry * | |
77 | find_disconnected_root(struct dentry *dentry) | |
78 | { | |
79 | dget(dentry); | |
80 | spin_lock(&dentry->d_lock); | |
81 | while (!IS_ROOT(dentry) && | |
82 | (dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) { | |
83 | struct dentry *parent = dentry->d_parent; | |
84 | dget(parent); | |
85 | spin_unlock(&dentry->d_lock); | |
86 | dput(dentry); | |
87 | dentry = parent; | |
88 | spin_lock(&dentry->d_lock); | |
89 | } | |
90 | spin_unlock(&dentry->d_lock); | |
91 | return dentry; | |
92 | } | |
93 | ||
019ab801 CH |
94 | |
95 | /* | |
96 | * Make sure target_dir is fully connected to the dentry tree. | |
1da177e4 | 97 | * |
019ab801 | 98 | * It may already be, as the flag isn't always updated when connection happens. |
1da177e4 | 99 | */ |
019ab801 CH |
100 | static int |
101 | reconnect_path(struct super_block *sb, struct dentry *target_dir) | |
1da177e4 | 102 | { |
1da177e4 | 103 | char nbuf[NAME_MAX+1]; |
019ab801 CH |
104 | int noprogress = 0; |
105 | int err = -ESTALE; | |
1da177e4 LT |
106 | |
107 | /* | |
019ab801 | 108 | * It is possible that a confused file system might not let us complete |
1da177e4 LT |
109 | * the path to the root. For example, if get_parent returns a directory |
110 | * in which we cannot find a name for the child. While this implies a | |
111 | * very sick filesystem we don't want it to cause knfsd to spin. Hence | |
112 | * the noprogress counter. If we go through the loop 10 times (2 is | |
113 | * probably enough) without getting anywhere, we just give up | |
114 | */ | |
1da177e4 | 115 | while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { |
dd90b509 | 116 | struct dentry *pd = find_disconnected_root(target_dir); |
1da177e4 LT |
117 | |
118 | if (!IS_ROOT(pd)) { | |
119 | /* must have found a connected parent - great */ | |
120 | spin_lock(&pd->d_lock); | |
121 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
122 | spin_unlock(&pd->d_lock); | |
123 | noprogress = 0; | |
124 | } else if (pd == sb->s_root) { | |
125 | printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); | |
126 | spin_lock(&pd->d_lock); | |
127 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
128 | spin_unlock(&pd->d_lock); | |
129 | noprogress = 0; | |
130 | } else { | |
10f11c34 CH |
131 | /* |
132 | * We have hit the top of a disconnected path, try to | |
133 | * find parent and connect. | |
134 | * | |
135 | * Racing with some other process renaming a directory | |
136 | * isn't much of a problem here. If someone renames | |
137 | * the directory, it will end up properly connected, | |
138 | * which is what we want | |
139 | * | |
140 | * Getting the parent can't be supported generically, | |
141 | * the locking is too icky. | |
142 | * | |
143 | * Instead we just return EACCES. If server reboots | |
144 | * or inodes get flushed, you lose | |
1da177e4 | 145 | */ |
10f11c34 | 146 | struct dentry *ppd = ERR_PTR(-EACCES); |
1da177e4 LT |
147 | struct dentry *npd; |
148 | ||
1b1dcc1b | 149 | mutex_lock(&pd->d_inode->i_mutex); |
019ab801 CH |
150 | if (sb->s_export_op->get_parent) |
151 | ppd = sb->s_export_op->get_parent(pd); | |
1b1dcc1b | 152 | mutex_unlock(&pd->d_inode->i_mutex); |
1da177e4 LT |
153 | |
154 | if (IS_ERR(ppd)) { | |
155 | err = PTR_ERR(ppd); | |
019ab801 CH |
156 | dprintk("%s: get_parent of %ld failed, err %d\n", |
157 | __FUNCTION__, pd->d_inode->i_ino, err); | |
1da177e4 LT |
158 | dput(pd); |
159 | break; | |
160 | } | |
019ab801 CH |
161 | |
162 | dprintk("%s: find name of %lu in %lu\n", __FUNCTION__, | |
163 | pd->d_inode->i_ino, ppd->d_inode->i_ino); | |
10f11c34 | 164 | err = exportfs_get_name(ppd, nbuf, pd); |
1da177e4 LT |
165 | if (err) { |
166 | dput(ppd); | |
167 | dput(pd); | |
168 | if (err == -ENOENT) | |
169 | /* some race between get_parent and | |
170 | * get_name? just try again | |
171 | */ | |
172 | continue; | |
173 | break; | |
174 | } | |
019ab801 | 175 | dprintk("%s: found name: %s\n", __FUNCTION__, nbuf); |
1b1dcc1b | 176 | mutex_lock(&ppd->d_inode->i_mutex); |
1da177e4 | 177 | npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); |
1b1dcc1b | 178 | mutex_unlock(&ppd->d_inode->i_mutex); |
1da177e4 LT |
179 | if (IS_ERR(npd)) { |
180 | err = PTR_ERR(npd); | |
019ab801 CH |
181 | dprintk("%s: lookup failed: %d\n", |
182 | __FUNCTION__, err); | |
1da177e4 LT |
183 | dput(ppd); |
184 | dput(pd); | |
185 | break; | |
186 | } | |
187 | /* we didn't really want npd, we really wanted | |
188 | * a side-effect of the lookup. | |
189 | * hopefully, npd == pd, though it isn't really | |
190 | * a problem if it isn't | |
191 | */ | |
192 | if (npd == pd) | |
193 | noprogress = 0; | |
194 | else | |
019ab801 | 195 | printk("%s: npd != pd\n", __FUNCTION__); |
1da177e4 LT |
196 | dput(npd); |
197 | dput(ppd); | |
198 | if (IS_ROOT(pd)) { | |
199 | /* something went wrong, we have to give up */ | |
200 | dput(pd); | |
201 | break; | |
202 | } | |
203 | } | |
204 | dput(pd); | |
205 | } | |
206 | ||
207 | if (target_dir->d_flags & DCACHE_DISCONNECTED) { | |
208 | /* something went wrong - oh-well */ | |
209 | if (!err) | |
210 | err = -ESTALE; | |
019ab801 | 211 | return err; |
1da177e4 | 212 | } |
019ab801 CH |
213 | |
214 | return 0; | |
215 | } | |
216 | ||
217 | /** | |
218 | * find_exported_dentry - helper routine to implement export_operations->decode_fh | |
219 | * @sb: The &super_block identifying the filesystem | |
220 | * @obj: An opaque identifier of the object to be found - passed to | |
221 | * get_inode | |
222 | * @parent: An optional opqaue identifier of the parent of the object. | |
223 | * @acceptable: A function used to test possible &dentries to see if they are | |
224 | * acceptable | |
225 | * @context: A parameter to @acceptable so that it knows on what basis to | |
226 | * judge. | |
227 | * | |
228 | * find_exported_dentry is the central helper routine to enable file systems | |
229 | * to provide the decode_fh() export_operation. It's main task is to take | |
230 | * an &inode, find or create an appropriate &dentry structure, and possibly | |
231 | * splice this into the dcache in the correct place. | |
232 | * | |
233 | * The decode_fh() operation provided by the filesystem should call | |
234 | * find_exported_dentry() with the same parameters that it received except | |
235 | * that instead of the file handle fragment, pointers to opaque identifiers | |
236 | * for the object and optionally its parent are passed. The default decode_fh | |
237 | * routine passes one pointer to the start of the filehandle fragment, and | |
238 | * one 8 bytes into the fragment. It is expected that most filesystems will | |
239 | * take this approach, though the offset to the parent identifier may well be | |
240 | * different. | |
241 | * | |
242 | * find_exported_dentry() will call get_dentry to get an dentry pointer from | |
243 | * the file system. If any &dentry in the d_alias list is acceptable, it will | |
244 | * be returned. Otherwise find_exported_dentry() will attempt to splice a new | |
245 | * &dentry into the dcache using get_name() and get_parent() to find the | |
246 | * appropriate place. | |
247 | */ | |
248 | ||
249 | struct dentry * | |
250 | find_exported_dentry(struct super_block *sb, void *obj, void *parent, | |
251 | int (*acceptable)(void *context, struct dentry *de), | |
252 | void *context) | |
253 | { | |
254 | struct dentry *result, *alias; | |
255 | int err = -ESTALE; | |
256 | ||
257 | /* | |
258 | * Attempt to find the inode. | |
259 | */ | |
260 | result = exportfs_get_dentry(sb, obj); | |
261 | if (IS_ERR(result)) | |
262 | return result; | |
263 | ||
264 | if (S_ISDIR(result->d_inode->i_mode)) { | |
265 | if (!(result->d_flags & DCACHE_DISCONNECTED)) { | |
266 | if (acceptable(context, result)) | |
267 | return result; | |
268 | err = -EACCES; | |
269 | goto err_result; | |
270 | } | |
271 | ||
272 | err = reconnect_path(sb, result); | |
273 | if (err) | |
274 | goto err_result; | |
275 | } else { | |
276 | struct dentry *target_dir, *nresult; | |
277 | char nbuf[NAME_MAX+1]; | |
278 | ||
279 | alias = find_acceptable_alias(result, acceptable, context); | |
280 | if (alias) | |
281 | return alias; | |
282 | ||
283 | if (parent == NULL) | |
284 | goto err_result; | |
285 | ||
286 | target_dir = exportfs_get_dentry(sb,parent); | |
287 | if (IS_ERR(target_dir)) { | |
288 | err = PTR_ERR(target_dir); | |
289 | goto err_result; | |
290 | } | |
291 | ||
292 | err = reconnect_path(sb, target_dir); | |
293 | if (err) { | |
294 | dput(target_dir); | |
295 | goto err_result; | |
296 | } | |
297 | ||
298 | /* | |
299 | * As we weren't after a directory, have one more step to go. | |
300 | */ | |
10f11c34 | 301 | err = exportfs_get_name(target_dir, nbuf, result); |
1da177e4 | 302 | if (!err) { |
1b1dcc1b | 303 | mutex_lock(&target_dir->d_inode->i_mutex); |
019ab801 CH |
304 | nresult = lookup_one_len(nbuf, target_dir, |
305 | strlen(nbuf)); | |
1b1dcc1b | 306 | mutex_unlock(&target_dir->d_inode->i_mutex); |
1da177e4 LT |
307 | if (!IS_ERR(nresult)) { |
308 | if (nresult->d_inode) { | |
309 | dput(result); | |
310 | result = nresult; | |
311 | } else | |
312 | dput(nresult); | |
313 | } | |
314 | } | |
019ab801 | 315 | dput(target_dir); |
1da177e4 | 316 | } |
e2f99018 CH |
317 | |
318 | alias = find_acceptable_alias(result, acceptable, context); | |
319 | if (alias) | |
320 | return alias; | |
1da177e4 LT |
321 | |
322 | /* drat - I just cannot find anything acceptable */ | |
323 | dput(result); | |
324 | /* It might be justifiable to return ESTALE here, | |
325 | * but the filehandle at-least looks reasonable good | |
019ab801 | 326 | * and it may just be a permission problem, so returning |
1da177e4 LT |
327 | * -EACCESS is safer |
328 | */ | |
329 | return ERR_PTR(-EACCES); | |
330 | ||
1da177e4 LT |
331 | err_result: |
332 | dput(result); | |
1da177e4 LT |
333 | return ERR_PTR(err); |
334 | } | |
335 | ||
1da177e4 LT |
336 | struct getdents_callback { |
337 | char *name; /* name that was found. It already points to a | |
338 | buffer NAME_MAX+1 is size */ | |
339 | unsigned long ino; /* the inum we are looking for */ | |
340 | int found; /* inode matched? */ | |
341 | int sequence; /* sequence counter */ | |
342 | }; | |
343 | ||
344 | /* | |
345 | * A rather strange filldir function to capture | |
346 | * the name matching the specified inode number. | |
347 | */ | |
348 | static int filldir_one(void * __buf, const char * name, int len, | |
afefdbb2 | 349 | loff_t pos, u64 ino, unsigned int d_type) |
1da177e4 LT |
350 | { |
351 | struct getdents_callback *buf = __buf; | |
352 | int result = 0; | |
353 | ||
354 | buf->sequence++; | |
355 | if (buf->ino == ino) { | |
356 | memcpy(buf->name, name, len); | |
357 | buf->name[len] = '\0'; | |
358 | buf->found = 1; | |
359 | result = -1; | |
360 | } | |
361 | return result; | |
362 | } | |
363 | ||
364 | /** | |
365 | * get_name - default export_operations->get_name function | |
366 | * @dentry: the directory in which to find a name | |
367 | * @name: a pointer to a %NAME_MAX+1 char buffer to store the name | |
368 | * @child: the dentry for the child directory. | |
369 | * | |
370 | * calls readdir on the parent until it finds an entry with | |
371 | * the same inode number as the child, and returns that. | |
372 | */ | |
373 | static int get_name(struct dentry *dentry, char *name, | |
374 | struct dentry *child) | |
375 | { | |
376 | struct inode *dir = dentry->d_inode; | |
377 | int error; | |
378 | struct file *file; | |
379 | struct getdents_callback buffer; | |
380 | ||
381 | error = -ENOTDIR; | |
382 | if (!dir || !S_ISDIR(dir->i_mode)) | |
383 | goto out; | |
384 | error = -EINVAL; | |
385 | if (!dir->i_fop) | |
386 | goto out; | |
387 | /* | |
388 | * Open the directory ... | |
389 | */ | |
390 | file = dentry_open(dget(dentry), NULL, O_RDONLY); | |
391 | error = PTR_ERR(file); | |
392 | if (IS_ERR(file)) | |
393 | goto out; | |
394 | ||
395 | error = -EINVAL; | |
396 | if (!file->f_op->readdir) | |
397 | goto out_close; | |
398 | ||
399 | buffer.name = name; | |
400 | buffer.ino = child->d_inode->i_ino; | |
401 | buffer.found = 0; | |
402 | buffer.sequence = 0; | |
403 | while (1) { | |
404 | int old_seq = buffer.sequence; | |
405 | ||
406 | error = vfs_readdir(file, filldir_one, &buffer); | |
407 | ||
408 | if (error < 0) | |
409 | break; | |
410 | ||
411 | error = 0; | |
412 | if (buffer.found) | |
413 | break; | |
414 | error = -ENOENT; | |
415 | if (old_seq == buffer.sequence) | |
416 | break; | |
417 | } | |
418 | ||
419 | out_close: | |
420 | fput(file); | |
421 | out: | |
422 | return error; | |
423 | } | |
424 | ||
1da177e4 LT |
425 | /** |
426 | * export_encode_fh - default export_operations->encode_fh function | |
427 | * @dentry: the dentry to encode | |
428 | * @fh: where to store the file handle fragment | |
429 | * @max_len: maximum length to store there | |
430 | * @connectable: whether to store parent information | |
431 | * | |
432 | * This default encode_fh function assumes that the 32 inode number | |
433 | * is suitable for locating an inode, and that the generation number | |
434 | * can be used to check that it is still valid. It places them in the | |
435 | * filehandle fragment where export_decode_fh expects to find them. | |
436 | */ | |
437 | static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, | |
438 | int connectable) | |
439 | { | |
440 | struct inode * inode = dentry->d_inode; | |
441 | int len = *max_len; | |
442 | int type = 1; | |
443 | ||
444 | if (len < 2 || (connectable && len < 4)) | |
445 | return 255; | |
446 | ||
447 | len = 2; | |
448 | fh[0] = inode->i_ino; | |
449 | fh[1] = inode->i_generation; | |
450 | if (connectable && !S_ISDIR(inode->i_mode)) { | |
451 | struct inode *parent; | |
452 | ||
453 | spin_lock(&dentry->d_lock); | |
454 | parent = dentry->d_parent->d_inode; | |
455 | fh[2] = parent->i_ino; | |
456 | fh[3] = parent->i_generation; | |
457 | spin_unlock(&dentry->d_lock); | |
458 | len = 4; | |
459 | type = 2; | |
460 | } | |
461 | *max_len = len; | |
462 | return type; | |
463 | } | |
464 | ||
465 | ||
466 | /** | |
467 | * export_decode_fh - default export_operations->decode_fh function | |
468 | * @sb: The superblock | |
469 | * @fh: pointer to the file handle fragment | |
470 | * @fh_len: length of file handle fragment | |
471 | * @acceptable: function for testing acceptability of dentrys | |
472 | * @context: context for @acceptable | |
473 | * | |
474 | * This is the default decode_fh() function. | |
475 | * a fileid_type of 1 indicates that the filehandlefragment | |
476 | * just contains an object identifier understood by get_dentry. | |
477 | * a fileid_type of 2 says that there is also a directory | |
478 | * identifier 8 bytes in to the filehandlefragement. | |
479 | */ | |
480 | static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len, | |
481 | int fileid_type, | |
482 | int (*acceptable)(void *context, struct dentry *de), | |
483 | void *context) | |
484 | { | |
485 | __u32 parent[2]; | |
486 | parent[0] = parent[1] = 0; | |
487 | if (fh_len < 2 || fileid_type > 2) | |
488 | return NULL; | |
489 | if (fileid_type == 2) { | |
490 | if (fh_len > 2) parent[0] = fh[2]; | |
491 | if (fh_len > 3) parent[1] = fh[3]; | |
492 | } | |
493 | return find_exported_dentry(sb, fh, parent, | |
494 | acceptable, context); | |
495 | } | |
496 | ||
d37065cd CH |
497 | int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, |
498 | int connectable) | |
499 | { | |
10f11c34 CH |
500 | struct export_operations *nop = dentry->d_sb->s_export_op; |
501 | int error; | |
d37065cd | 502 | |
10f11c34 CH |
503 | if (nop->encode_fh) |
504 | error = nop->encode_fh(dentry, fh, max_len, connectable); | |
505 | else | |
506 | error = export_encode_fh(dentry, fh, max_len, connectable); | |
507 | ||
508 | return error; | |
d37065cd CH |
509 | } |
510 | EXPORT_SYMBOL_GPL(exportfs_encode_fh); | |
511 | ||
512 | struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, int fh_len, | |
513 | int fileid_type, int (*acceptable)(void *, struct dentry *), | |
514 | void *context) | |
515 | { | |
516 | struct export_operations *nop = mnt->mnt_sb->s_export_op; | |
10f11c34 | 517 | struct dentry *result; |
d37065cd | 518 | |
10f11c34 CH |
519 | if (nop->decode_fh) { |
520 | result = nop->decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type, | |
d37065cd | 521 | acceptable, context); |
10f11c34 CH |
522 | } else { |
523 | result = export_decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type, | |
524 | acceptable, context); | |
525 | } | |
526 | ||
527 | return result; | |
d37065cd CH |
528 | } |
529 | EXPORT_SYMBOL_GPL(exportfs_decode_fh); | |
530 | ||
1da177e4 LT |
531 | EXPORT_SYMBOL(find_exported_dentry); |
532 | ||
533 | MODULE_LICENSE("GPL"); |