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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 | ||
9 | struct export_operations export_op_default; | |
10 | ||
11 | #define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun) | |
12 | ||
13 | #define dprintk(fmt, args...) do{}while(0) | |
14 | ||
e2f99018 CH |
15 | static struct dentry * |
16 | find_acceptable_alias(struct dentry *result, | |
17 | int (*acceptable)(void *context, struct dentry *dentry), | |
18 | void *context) | |
19 | { | |
20 | struct dentry *dentry, *toput = NULL; | |
21 | ||
22 | spin_lock(&dcache_lock); | |
23 | list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) { | |
24 | dget_locked(dentry); | |
25 | spin_unlock(&dcache_lock); | |
26 | if (toput) | |
27 | dput(toput); | |
28 | if (dentry != result && acceptable(context, dentry)) { | |
29 | dput(result); | |
30 | return dentry; | |
31 | } | |
32 | spin_lock(&dcache_lock); | |
33 | toput = dentry; | |
34 | } | |
35 | spin_unlock(&dcache_lock); | |
36 | ||
37 | if (toput) | |
38 | dput(toput); | |
39 | return NULL; | |
40 | } | |
41 | ||
1da177e4 LT |
42 | /** |
43 | * find_exported_dentry - helper routine to implement export_operations->decode_fh | |
44 | * @sb: The &super_block identifying the filesystem | |
45 | * @obj: An opaque identifier of the object to be found - passed to | |
46 | * get_inode | |
47 | * @parent: An optional opqaue identifier of the parent of the object. | |
48 | * @acceptable: A function used to test possible &dentries to see if they are | |
49 | * acceptable | |
50 | * @context: A parameter to @acceptable so that it knows on what basis to | |
51 | * judge. | |
52 | * | |
53 | * find_exported_dentry is the central helper routine to enable file systems | |
54 | * to provide the decode_fh() export_operation. It's main task is to take | |
55 | * an &inode, find or create an appropriate &dentry structure, and possibly | |
56 | * splice this into the dcache in the correct place. | |
57 | * | |
58 | * The decode_fh() operation provided by the filesystem should call | |
59 | * find_exported_dentry() with the same parameters that it received except | |
60 | * that instead of the file handle fragment, pointers to opaque identifiers | |
61 | * for the object and optionally its parent are passed. The default decode_fh | |
62 | * routine passes one pointer to the start of the filehandle fragment, and | |
63 | * one 8 bytes into the fragment. It is expected that most filesystems will | |
64 | * take this approach, though the offset to the parent identifier may well be | |
65 | * different. | |
66 | * | |
67 | * find_exported_dentry() will call get_dentry to get an dentry pointer from | |
68 | * the file system. If any &dentry in the d_alias list is acceptable, it will | |
69 | * be returned. Otherwise find_exported_dentry() will attempt to splice a new | |
70 | * &dentry into the dcache using get_name() and get_parent() to find the | |
71 | * appropriate place. | |
72 | */ | |
73 | ||
74 | struct dentry * | |
75 | find_exported_dentry(struct super_block *sb, void *obj, void *parent, | |
76 | int (*acceptable)(void *context, struct dentry *de), | |
77 | void *context) | |
78 | { | |
79 | struct dentry *result = NULL; | |
80 | struct dentry *target_dir; | |
81 | int err; | |
82 | struct export_operations *nops = sb->s_export_op; | |
e2f99018 | 83 | struct dentry *alias; |
1da177e4 LT |
84 | int noprogress; |
85 | char nbuf[NAME_MAX+1]; | |
86 | ||
87 | /* | |
88 | * Attempt to find the inode. | |
89 | */ | |
90 | result = CALL(sb->s_export_op,get_dentry)(sb,obj); | |
91 | err = -ESTALE; | |
92 | if (result == NULL) | |
93 | goto err_out; | |
94 | if (IS_ERR(result)) { | |
95 | err = PTR_ERR(result); | |
96 | goto err_out; | |
97 | } | |
98 | if (S_ISDIR(result->d_inode->i_mode) && | |
99 | (result->d_flags & DCACHE_DISCONNECTED)) { | |
100 | /* it is an unconnected directory, we must connect it */ | |
101 | ; | |
102 | } else { | |
103 | if (acceptable(context, result)) | |
104 | return result; | |
105 | if (S_ISDIR(result->d_inode->i_mode)) { | |
8c7b389e | 106 | err = -EACCES; |
1da177e4 LT |
107 | goto err_result; |
108 | } | |
e2f99018 CH |
109 | |
110 | alias = find_acceptable_alias(result, acceptable, context); | |
111 | if (alias) | |
112 | return alias; | |
1da177e4 LT |
113 | } |
114 | ||
115 | /* It's a directory, or we are required to confirm the file's | |
116 | * location in the tree based on the parent information | |
117 | */ | |
118 | dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj); | |
119 | if (S_ISDIR(result->d_inode->i_mode)) | |
120 | target_dir = dget(result); | |
121 | else { | |
122 | if (parent == NULL) | |
123 | goto err_result; | |
124 | ||
125 | target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent); | |
126 | if (IS_ERR(target_dir)) | |
127 | err = PTR_ERR(target_dir); | |
128 | if (target_dir == NULL || IS_ERR(target_dir)) | |
129 | goto err_result; | |
130 | } | |
131 | /* | |
132 | * Now we need to make sure that target_dir is properly connected. | |
133 | * It may already be, as the flag isn't always updated when connection | |
134 | * happens. | |
135 | * So, we walk up parent links until we find a connected directory, | |
136 | * or we run out of directories. Then we find the parent, find | |
137 | * the name of the child in that parent, and do a lookup. | |
138 | * This should connect the child into the parent | |
139 | * We then repeat. | |
140 | */ | |
141 | ||
142 | /* it is possible that a confused file system might not let us complete | |
143 | * the path to the root. For example, if get_parent returns a directory | |
144 | * in which we cannot find a name for the child. While this implies a | |
145 | * very sick filesystem we don't want it to cause knfsd to spin. Hence | |
146 | * the noprogress counter. If we go through the loop 10 times (2 is | |
147 | * probably enough) without getting anywhere, we just give up | |
148 | */ | |
149 | noprogress= 0; | |
150 | while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { | |
151 | struct dentry *pd = target_dir; | |
152 | ||
153 | dget(pd); | |
154 | spin_lock(&pd->d_lock); | |
155 | while (!IS_ROOT(pd) && | |
156 | (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) { | |
157 | struct dentry *parent = pd->d_parent; | |
158 | ||
159 | dget(parent); | |
160 | spin_unlock(&pd->d_lock); | |
161 | dput(pd); | |
162 | pd = parent; | |
163 | spin_lock(&pd->d_lock); | |
164 | } | |
165 | spin_unlock(&pd->d_lock); | |
166 | ||
167 | if (!IS_ROOT(pd)) { | |
168 | /* must have found a connected parent - great */ | |
169 | spin_lock(&pd->d_lock); | |
170 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
171 | spin_unlock(&pd->d_lock); | |
172 | noprogress = 0; | |
173 | } else if (pd == sb->s_root) { | |
174 | printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); | |
175 | spin_lock(&pd->d_lock); | |
176 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
177 | spin_unlock(&pd->d_lock); | |
178 | noprogress = 0; | |
179 | } else { | |
180 | /* we have hit the top of a disconnected path. Try | |
181 | * to find parent and connect | |
182 | * note: racing with some other process renaming a | |
183 | * directory isn't much of a problem here. If someone | |
184 | * renames the directory, it will end up properly | |
185 | * connected, which is what we want | |
186 | */ | |
187 | struct dentry *ppd; | |
188 | struct dentry *npd; | |
189 | ||
1b1dcc1b | 190 | mutex_lock(&pd->d_inode->i_mutex); |
1da177e4 | 191 | ppd = CALL(nops,get_parent)(pd); |
1b1dcc1b | 192 | mutex_unlock(&pd->d_inode->i_mutex); |
1da177e4 LT |
193 | |
194 | if (IS_ERR(ppd)) { | |
195 | err = PTR_ERR(ppd); | |
196 | dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n", | |
197 | pd->d_inode->i_ino, err); | |
198 | dput(pd); | |
199 | break; | |
200 | } | |
201 | dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino); | |
202 | err = CALL(nops,get_name)(ppd, nbuf, pd); | |
203 | if (err) { | |
204 | dput(ppd); | |
205 | dput(pd); | |
206 | if (err == -ENOENT) | |
207 | /* some race between get_parent and | |
208 | * get_name? just try again | |
209 | */ | |
210 | continue; | |
211 | break; | |
212 | } | |
213 | dprintk("find_exported_dentry: found name: %s\n", nbuf); | |
1b1dcc1b | 214 | mutex_lock(&ppd->d_inode->i_mutex); |
1da177e4 | 215 | npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); |
1b1dcc1b | 216 | mutex_unlock(&ppd->d_inode->i_mutex); |
1da177e4 LT |
217 | if (IS_ERR(npd)) { |
218 | err = PTR_ERR(npd); | |
219 | dprintk("find_exported_dentry: lookup failed: %d\n", err); | |
220 | dput(ppd); | |
221 | dput(pd); | |
222 | break; | |
223 | } | |
224 | /* we didn't really want npd, we really wanted | |
225 | * a side-effect of the lookup. | |
226 | * hopefully, npd == pd, though it isn't really | |
227 | * a problem if it isn't | |
228 | */ | |
229 | if (npd == pd) | |
230 | noprogress = 0; | |
231 | else | |
232 | printk("find_exported_dentry: npd != pd\n"); | |
233 | dput(npd); | |
234 | dput(ppd); | |
235 | if (IS_ROOT(pd)) { | |
236 | /* something went wrong, we have to give up */ | |
237 | dput(pd); | |
238 | break; | |
239 | } | |
240 | } | |
241 | dput(pd); | |
242 | } | |
243 | ||
244 | if (target_dir->d_flags & DCACHE_DISCONNECTED) { | |
245 | /* something went wrong - oh-well */ | |
246 | if (!err) | |
247 | err = -ESTALE; | |
248 | goto err_target; | |
249 | } | |
250 | /* if we weren't after a directory, have one more step to go */ | |
251 | if (result != target_dir) { | |
252 | struct dentry *nresult; | |
253 | err = CALL(nops,get_name)(target_dir, nbuf, result); | |
254 | if (!err) { | |
1b1dcc1b | 255 | mutex_lock(&target_dir->d_inode->i_mutex); |
1da177e4 | 256 | nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf)); |
1b1dcc1b | 257 | mutex_unlock(&target_dir->d_inode->i_mutex); |
1da177e4 LT |
258 | if (!IS_ERR(nresult)) { |
259 | if (nresult->d_inode) { | |
260 | dput(result); | |
261 | result = nresult; | |
262 | } else | |
263 | dput(nresult); | |
264 | } | |
265 | } | |
266 | } | |
267 | dput(target_dir); | |
268 | /* now result is properly connected, it is our best bet */ | |
269 | if (acceptable(context, result)) | |
270 | return result; | |
e2f99018 CH |
271 | |
272 | alias = find_acceptable_alias(result, acceptable, context); | |
273 | if (alias) | |
274 | return alias; | |
1da177e4 LT |
275 | |
276 | /* drat - I just cannot find anything acceptable */ | |
277 | dput(result); | |
278 | /* It might be justifiable to return ESTALE here, | |
279 | * but the filehandle at-least looks reasonable good | |
280 | * and it just be a permission problem, so returning | |
281 | * -EACCESS is safer | |
282 | */ | |
283 | return ERR_PTR(-EACCES); | |
284 | ||
285 | err_target: | |
286 | dput(target_dir); | |
287 | err_result: | |
288 | dput(result); | |
289 | err_out: | |
290 | return ERR_PTR(err); | |
291 | } | |
292 | ||
293 | ||
294 | ||
295 | static struct dentry *get_parent(struct dentry *child) | |
296 | { | |
297 | /* get_parent cannot be supported generically, the locking | |
298 | * is too icky. | |
299 | * instead, we just return EACCES. If server reboots or inodes | |
300 | * get flushed, you lose | |
301 | */ | |
302 | return ERR_PTR(-EACCES); | |
303 | } | |
304 | ||
305 | ||
306 | struct getdents_callback { | |
307 | char *name; /* name that was found. It already points to a | |
308 | buffer NAME_MAX+1 is size */ | |
309 | unsigned long ino; /* the inum we are looking for */ | |
310 | int found; /* inode matched? */ | |
311 | int sequence; /* sequence counter */ | |
312 | }; | |
313 | ||
314 | /* | |
315 | * A rather strange filldir function to capture | |
316 | * the name matching the specified inode number. | |
317 | */ | |
318 | static int filldir_one(void * __buf, const char * name, int len, | |
afefdbb2 | 319 | loff_t pos, u64 ino, unsigned int d_type) |
1da177e4 LT |
320 | { |
321 | struct getdents_callback *buf = __buf; | |
322 | int result = 0; | |
323 | ||
324 | buf->sequence++; | |
325 | if (buf->ino == ino) { | |
326 | memcpy(buf->name, name, len); | |
327 | buf->name[len] = '\0'; | |
328 | buf->found = 1; | |
329 | result = -1; | |
330 | } | |
331 | return result; | |
332 | } | |
333 | ||
334 | /** | |
335 | * get_name - default export_operations->get_name function | |
336 | * @dentry: the directory in which to find a name | |
337 | * @name: a pointer to a %NAME_MAX+1 char buffer to store the name | |
338 | * @child: the dentry for the child directory. | |
339 | * | |
340 | * calls readdir on the parent until it finds an entry with | |
341 | * the same inode number as the child, and returns that. | |
342 | */ | |
343 | static int get_name(struct dentry *dentry, char *name, | |
344 | struct dentry *child) | |
345 | { | |
346 | struct inode *dir = dentry->d_inode; | |
347 | int error; | |
348 | struct file *file; | |
349 | struct getdents_callback buffer; | |
350 | ||
351 | error = -ENOTDIR; | |
352 | if (!dir || !S_ISDIR(dir->i_mode)) | |
353 | goto out; | |
354 | error = -EINVAL; | |
355 | if (!dir->i_fop) | |
356 | goto out; | |
357 | /* | |
358 | * Open the directory ... | |
359 | */ | |
360 | file = dentry_open(dget(dentry), NULL, O_RDONLY); | |
361 | error = PTR_ERR(file); | |
362 | if (IS_ERR(file)) | |
363 | goto out; | |
364 | ||
365 | error = -EINVAL; | |
366 | if (!file->f_op->readdir) | |
367 | goto out_close; | |
368 | ||
369 | buffer.name = name; | |
370 | buffer.ino = child->d_inode->i_ino; | |
371 | buffer.found = 0; | |
372 | buffer.sequence = 0; | |
373 | while (1) { | |
374 | int old_seq = buffer.sequence; | |
375 | ||
376 | error = vfs_readdir(file, filldir_one, &buffer); | |
377 | ||
378 | if (error < 0) | |
379 | break; | |
380 | ||
381 | error = 0; | |
382 | if (buffer.found) | |
383 | break; | |
384 | error = -ENOENT; | |
385 | if (old_seq == buffer.sequence) | |
386 | break; | |
387 | } | |
388 | ||
389 | out_close: | |
390 | fput(file); | |
391 | out: | |
392 | return error; | |
393 | } | |
394 | ||
5ca29607 | 395 | static struct dentry *get_dentry(struct super_block *sb, void *vobjp) |
1da177e4 | 396 | { |
5ca29607 | 397 | return ERR_PTR(-ESTALE); |
1da177e4 LT |
398 | } |
399 | ||
1da177e4 LT |
400 | /** |
401 | * export_encode_fh - default export_operations->encode_fh function | |
402 | * @dentry: the dentry to encode | |
403 | * @fh: where to store the file handle fragment | |
404 | * @max_len: maximum length to store there | |
405 | * @connectable: whether to store parent information | |
406 | * | |
407 | * This default encode_fh function assumes that the 32 inode number | |
408 | * is suitable for locating an inode, and that the generation number | |
409 | * can be used to check that it is still valid. It places them in the | |
410 | * filehandle fragment where export_decode_fh expects to find them. | |
411 | */ | |
412 | static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, | |
413 | int connectable) | |
414 | { | |
415 | struct inode * inode = dentry->d_inode; | |
416 | int len = *max_len; | |
417 | int type = 1; | |
418 | ||
419 | if (len < 2 || (connectable && len < 4)) | |
420 | return 255; | |
421 | ||
422 | len = 2; | |
423 | fh[0] = inode->i_ino; | |
424 | fh[1] = inode->i_generation; | |
425 | if (connectable && !S_ISDIR(inode->i_mode)) { | |
426 | struct inode *parent; | |
427 | ||
428 | spin_lock(&dentry->d_lock); | |
429 | parent = dentry->d_parent->d_inode; | |
430 | fh[2] = parent->i_ino; | |
431 | fh[3] = parent->i_generation; | |
432 | spin_unlock(&dentry->d_lock); | |
433 | len = 4; | |
434 | type = 2; | |
435 | } | |
436 | *max_len = len; | |
437 | return type; | |
438 | } | |
439 | ||
440 | ||
441 | /** | |
442 | * export_decode_fh - default export_operations->decode_fh function | |
443 | * @sb: The superblock | |
444 | * @fh: pointer to the file handle fragment | |
445 | * @fh_len: length of file handle fragment | |
446 | * @acceptable: function for testing acceptability of dentrys | |
447 | * @context: context for @acceptable | |
448 | * | |
449 | * This is the default decode_fh() function. | |
450 | * a fileid_type of 1 indicates that the filehandlefragment | |
451 | * just contains an object identifier understood by get_dentry. | |
452 | * a fileid_type of 2 says that there is also a directory | |
453 | * identifier 8 bytes in to the filehandlefragement. | |
454 | */ | |
455 | static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len, | |
456 | int fileid_type, | |
457 | int (*acceptable)(void *context, struct dentry *de), | |
458 | void *context) | |
459 | { | |
460 | __u32 parent[2]; | |
461 | parent[0] = parent[1] = 0; | |
462 | if (fh_len < 2 || fileid_type > 2) | |
463 | return NULL; | |
464 | if (fileid_type == 2) { | |
465 | if (fh_len > 2) parent[0] = fh[2]; | |
466 | if (fh_len > 3) parent[1] = fh[3]; | |
467 | } | |
468 | return find_exported_dentry(sb, fh, parent, | |
469 | acceptable, context); | |
470 | } | |
471 | ||
d37065cd CH |
472 | int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, |
473 | int connectable) | |
474 | { | |
475 | struct export_operations *nop = dentry->d_sb->s_export_op; | |
476 | ||
477 | return CALL(nop, encode_fh)(dentry, fh, max_len, connectable); | |
478 | } | |
479 | EXPORT_SYMBOL_GPL(exportfs_encode_fh); | |
480 | ||
481 | struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, int fh_len, | |
482 | int fileid_type, int (*acceptable)(void *, struct dentry *), | |
483 | void *context) | |
484 | { | |
485 | struct export_operations *nop = mnt->mnt_sb->s_export_op; | |
486 | ||
487 | return CALL(nop, decode_fh)(mnt->mnt_sb, fh, fh_len, fileid_type, | |
488 | acceptable, context); | |
489 | } | |
490 | EXPORT_SYMBOL_GPL(exportfs_decode_fh); | |
491 | ||
1da177e4 LT |
492 | struct export_operations export_op_default = { |
493 | .decode_fh = export_decode_fh, | |
494 | .encode_fh = export_encode_fh, | |
495 | ||
496 | .get_name = get_name, | |
497 | .get_parent = get_parent, | |
5ca29607 | 498 | .get_dentry = get_dentry, |
1da177e4 LT |
499 | }; |
500 | ||
1da177e4 LT |
501 | EXPORT_SYMBOL(find_exported_dentry); |
502 | ||
503 | MODULE_LICENSE("GPL"); |