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Commit | Line | Data |
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e38f9817 CH |
1 | /* |
2 | * Copyright (C) Neil Brown 2002 | |
3 | * Copyright (C) Christoph Hellwig 2007 | |
4 | * | |
5 | * This file contains the code mapping from inodes to NFS file handles, | |
6 | * and for mapping back from file handles to dentries. | |
7 | * | |
8 | * For details on why we do all the strange and hairy things in here | |
9 | * take a look at Documentation/filesystems/Exporting. | |
10 | */ | |
a5694255 | 11 | #include <linux/exportfs.h> |
1da177e4 LT |
12 | #include <linux/fs.h> |
13 | #include <linux/file.h> | |
14 | #include <linux/module.h> | |
d37065cd | 15 | #include <linux/mount.h> |
1da177e4 LT |
16 | #include <linux/namei.h> |
17 | ||
10f11c34 | 18 | #define dprintk(fmt, args...) do{}while(0) |
1da177e4 | 19 | |
1da177e4 | 20 | |
e38f9817 | 21 | static int get_name(struct vfsmount *mnt, struct dentry *dentry, char *name, |
10f11c34 CH |
22 | struct dentry *child); |
23 | ||
24 | ||
e38f9817 CH |
25 | static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir, |
26 | char *name, struct dentry *child) | |
10f11c34 | 27 | { |
39655164 | 28 | const struct export_operations *nop = dir->d_sb->s_export_op; |
10f11c34 CH |
29 | |
30 | if (nop->get_name) | |
31 | return nop->get_name(dir, name, child); | |
32 | else | |
e38f9817 | 33 | return get_name(mnt, dir, name, child); |
10f11c34 | 34 | } |
1da177e4 | 35 | |
fb66a198 CH |
36 | /* |
37 | * Check if the dentry or any of it's aliases is acceptable. | |
38 | */ | |
e2f99018 CH |
39 | static struct dentry * |
40 | find_acceptable_alias(struct dentry *result, | |
41 | int (*acceptable)(void *context, struct dentry *dentry), | |
42 | void *context) | |
43 | { | |
44 | struct dentry *dentry, *toput = NULL; | |
45 | ||
fb66a198 CH |
46 | if (acceptable(context, result)) |
47 | return result; | |
48 | ||
e2f99018 CH |
49 | spin_lock(&dcache_lock); |
50 | list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) { | |
51 | dget_locked(dentry); | |
52 | spin_unlock(&dcache_lock); | |
53 | if (toput) | |
54 | dput(toput); | |
55 | if (dentry != result && acceptable(context, dentry)) { | |
56 | dput(result); | |
57 | return dentry; | |
58 | } | |
59 | spin_lock(&dcache_lock); | |
60 | toput = dentry; | |
61 | } | |
62 | spin_unlock(&dcache_lock); | |
63 | ||
64 | if (toput) | |
65 | dput(toput); | |
66 | return NULL; | |
67 | } | |
68 | ||
dd90b509 CH |
69 | /* |
70 | * Find root of a disconnected subtree and return a reference to it. | |
71 | */ | |
72 | static struct dentry * | |
73 | find_disconnected_root(struct dentry *dentry) | |
74 | { | |
75 | dget(dentry); | |
76 | spin_lock(&dentry->d_lock); | |
77 | while (!IS_ROOT(dentry) && | |
78 | (dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) { | |
79 | struct dentry *parent = dentry->d_parent; | |
80 | dget(parent); | |
81 | spin_unlock(&dentry->d_lock); | |
82 | dput(dentry); | |
83 | dentry = parent; | |
84 | spin_lock(&dentry->d_lock); | |
85 | } | |
86 | spin_unlock(&dentry->d_lock); | |
87 | return dentry; | |
88 | } | |
89 | ||
019ab801 CH |
90 | |
91 | /* | |
92 | * Make sure target_dir is fully connected to the dentry tree. | |
1da177e4 | 93 | * |
019ab801 | 94 | * It may already be, as the flag isn't always updated when connection happens. |
1da177e4 | 95 | */ |
019ab801 | 96 | static int |
e38f9817 | 97 | reconnect_path(struct vfsmount *mnt, struct dentry *target_dir) |
1da177e4 | 98 | { |
1da177e4 | 99 | char nbuf[NAME_MAX+1]; |
019ab801 CH |
100 | int noprogress = 0; |
101 | int err = -ESTALE; | |
1da177e4 LT |
102 | |
103 | /* | |
019ab801 | 104 | * It is possible that a confused file system might not let us complete |
1da177e4 LT |
105 | * the path to the root. For example, if get_parent returns a directory |
106 | * in which we cannot find a name for the child. While this implies a | |
107 | * very sick filesystem we don't want it to cause knfsd to spin. Hence | |
108 | * the noprogress counter. If we go through the loop 10 times (2 is | |
109 | * probably enough) without getting anywhere, we just give up | |
110 | */ | |
1da177e4 | 111 | while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { |
dd90b509 | 112 | struct dentry *pd = find_disconnected_root(target_dir); |
1da177e4 LT |
113 | |
114 | if (!IS_ROOT(pd)) { | |
115 | /* must have found a connected parent - great */ | |
116 | spin_lock(&pd->d_lock); | |
117 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
118 | spin_unlock(&pd->d_lock); | |
119 | noprogress = 0; | |
e38f9817 | 120 | } else if (pd == mnt->mnt_sb->s_root) { |
1da177e4 LT |
121 | printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); |
122 | spin_lock(&pd->d_lock); | |
123 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
124 | spin_unlock(&pd->d_lock); | |
125 | noprogress = 0; | |
126 | } else { | |
10f11c34 CH |
127 | /* |
128 | * We have hit the top of a disconnected path, try to | |
129 | * find parent and connect. | |
130 | * | |
131 | * Racing with some other process renaming a directory | |
132 | * isn't much of a problem here. If someone renames | |
133 | * the directory, it will end up properly connected, | |
134 | * which is what we want | |
135 | * | |
136 | * Getting the parent can't be supported generically, | |
137 | * the locking is too icky. | |
138 | * | |
139 | * Instead we just return EACCES. If server reboots | |
140 | * or inodes get flushed, you lose | |
1da177e4 | 141 | */ |
10f11c34 | 142 | struct dentry *ppd = ERR_PTR(-EACCES); |
1da177e4 LT |
143 | struct dentry *npd; |
144 | ||
1b1dcc1b | 145 | mutex_lock(&pd->d_inode->i_mutex); |
e38f9817 CH |
146 | if (mnt->mnt_sb->s_export_op->get_parent) |
147 | ppd = mnt->mnt_sb->s_export_op->get_parent(pd); | |
1b1dcc1b | 148 | mutex_unlock(&pd->d_inode->i_mutex); |
1da177e4 LT |
149 | |
150 | if (IS_ERR(ppd)) { | |
151 | err = PTR_ERR(ppd); | |
019ab801 CH |
152 | dprintk("%s: get_parent of %ld failed, err %d\n", |
153 | __FUNCTION__, pd->d_inode->i_ino, err); | |
1da177e4 LT |
154 | dput(pd); |
155 | break; | |
156 | } | |
019ab801 CH |
157 | |
158 | dprintk("%s: find name of %lu in %lu\n", __FUNCTION__, | |
159 | pd->d_inode->i_ino, ppd->d_inode->i_ino); | |
e38f9817 | 160 | err = exportfs_get_name(mnt, ppd, nbuf, pd); |
1da177e4 LT |
161 | if (err) { |
162 | dput(ppd); | |
163 | dput(pd); | |
164 | if (err == -ENOENT) | |
165 | /* some race between get_parent and | |
166 | * get_name? just try again | |
167 | */ | |
168 | continue; | |
169 | break; | |
170 | } | |
019ab801 | 171 | dprintk("%s: found name: %s\n", __FUNCTION__, nbuf); |
1b1dcc1b | 172 | mutex_lock(&ppd->d_inode->i_mutex); |
1da177e4 | 173 | npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); |
1b1dcc1b | 174 | mutex_unlock(&ppd->d_inode->i_mutex); |
1da177e4 LT |
175 | if (IS_ERR(npd)) { |
176 | err = PTR_ERR(npd); | |
019ab801 CH |
177 | dprintk("%s: lookup failed: %d\n", |
178 | __FUNCTION__, err); | |
1da177e4 LT |
179 | dput(ppd); |
180 | dput(pd); | |
181 | break; | |
182 | } | |
183 | /* we didn't really want npd, we really wanted | |
184 | * a side-effect of the lookup. | |
185 | * hopefully, npd == pd, though it isn't really | |
186 | * a problem if it isn't | |
187 | */ | |
188 | if (npd == pd) | |
189 | noprogress = 0; | |
190 | else | |
019ab801 | 191 | printk("%s: npd != pd\n", __FUNCTION__); |
1da177e4 LT |
192 | dput(npd); |
193 | dput(ppd); | |
194 | if (IS_ROOT(pd)) { | |
195 | /* something went wrong, we have to give up */ | |
196 | dput(pd); | |
197 | break; | |
198 | } | |
199 | } | |
200 | dput(pd); | |
201 | } | |
202 | ||
203 | if (target_dir->d_flags & DCACHE_DISCONNECTED) { | |
204 | /* something went wrong - oh-well */ | |
205 | if (!err) | |
206 | err = -ESTALE; | |
019ab801 | 207 | return err; |
1da177e4 | 208 | } |
019ab801 CH |
209 | |
210 | return 0; | |
211 | } | |
212 | ||
1da177e4 LT |
213 | struct getdents_callback { |
214 | char *name; /* name that was found. It already points to a | |
215 | buffer NAME_MAX+1 is size */ | |
216 | unsigned long ino; /* the inum we are looking for */ | |
217 | int found; /* inode matched? */ | |
218 | int sequence; /* sequence counter */ | |
219 | }; | |
220 | ||
221 | /* | |
222 | * A rather strange filldir function to capture | |
223 | * the name matching the specified inode number. | |
224 | */ | |
225 | static int filldir_one(void * __buf, const char * name, int len, | |
afefdbb2 | 226 | loff_t pos, u64 ino, unsigned int d_type) |
1da177e4 LT |
227 | { |
228 | struct getdents_callback *buf = __buf; | |
229 | int result = 0; | |
230 | ||
231 | buf->sequence++; | |
232 | if (buf->ino == ino) { | |
233 | memcpy(buf->name, name, len); | |
234 | buf->name[len] = '\0'; | |
235 | buf->found = 1; | |
236 | result = -1; | |
237 | } | |
238 | return result; | |
239 | } | |
240 | ||
241 | /** | |
242 | * get_name - default export_operations->get_name function | |
243 | * @dentry: the directory in which to find a name | |
244 | * @name: a pointer to a %NAME_MAX+1 char buffer to store the name | |
245 | * @child: the dentry for the child directory. | |
246 | * | |
247 | * calls readdir on the parent until it finds an entry with | |
248 | * the same inode number as the child, and returns that. | |
249 | */ | |
e38f9817 CH |
250 | static int get_name(struct vfsmount *mnt, struct dentry *dentry, |
251 | char *name, struct dentry *child) | |
1da177e4 LT |
252 | { |
253 | struct inode *dir = dentry->d_inode; | |
254 | int error; | |
255 | struct file *file; | |
256 | struct getdents_callback buffer; | |
257 | ||
258 | error = -ENOTDIR; | |
259 | if (!dir || !S_ISDIR(dir->i_mode)) | |
260 | goto out; | |
261 | error = -EINVAL; | |
262 | if (!dir->i_fop) | |
263 | goto out; | |
264 | /* | |
265 | * Open the directory ... | |
266 | */ | |
e38f9817 | 267 | file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY); |
1da177e4 LT |
268 | error = PTR_ERR(file); |
269 | if (IS_ERR(file)) | |
270 | goto out; | |
271 | ||
272 | error = -EINVAL; | |
273 | if (!file->f_op->readdir) | |
274 | goto out_close; | |
275 | ||
276 | buffer.name = name; | |
277 | buffer.ino = child->d_inode->i_ino; | |
278 | buffer.found = 0; | |
279 | buffer.sequence = 0; | |
280 | while (1) { | |
281 | int old_seq = buffer.sequence; | |
282 | ||
283 | error = vfs_readdir(file, filldir_one, &buffer); | |
284 | ||
285 | if (error < 0) | |
286 | break; | |
287 | ||
288 | error = 0; | |
289 | if (buffer.found) | |
290 | break; | |
291 | error = -ENOENT; | |
292 | if (old_seq == buffer.sequence) | |
293 | break; | |
294 | } | |
295 | ||
296 | out_close: | |
297 | fput(file); | |
298 | out: | |
299 | return error; | |
300 | } | |
301 | ||
1da177e4 LT |
302 | /** |
303 | * export_encode_fh - default export_operations->encode_fh function | |
304 | * @dentry: the dentry to encode | |
305 | * @fh: where to store the file handle fragment | |
306 | * @max_len: maximum length to store there | |
307 | * @connectable: whether to store parent information | |
308 | * | |
309 | * This default encode_fh function assumes that the 32 inode number | |
310 | * is suitable for locating an inode, and that the generation number | |
311 | * can be used to check that it is still valid. It places them in the | |
312 | * filehandle fragment where export_decode_fh expects to find them. | |
313 | */ | |
6e91ea2b CH |
314 | static int export_encode_fh(struct dentry *dentry, struct fid *fid, |
315 | int *max_len, int connectable) | |
1da177e4 LT |
316 | { |
317 | struct inode * inode = dentry->d_inode; | |
318 | int len = *max_len; | |
6e91ea2b | 319 | int type = FILEID_INO32_GEN; |
1da177e4 LT |
320 | |
321 | if (len < 2 || (connectable && len < 4)) | |
322 | return 255; | |
323 | ||
324 | len = 2; | |
6e91ea2b CH |
325 | fid->i32.ino = inode->i_ino; |
326 | fid->i32.gen = inode->i_generation; | |
1da177e4 LT |
327 | if (connectable && !S_ISDIR(inode->i_mode)) { |
328 | struct inode *parent; | |
329 | ||
330 | spin_lock(&dentry->d_lock); | |
331 | parent = dentry->d_parent->d_inode; | |
6e91ea2b CH |
332 | fid->i32.parent_ino = parent->i_ino; |
333 | fid->i32.parent_gen = parent->i_generation; | |
1da177e4 LT |
334 | spin_unlock(&dentry->d_lock); |
335 | len = 4; | |
6e91ea2b | 336 | type = FILEID_INO32_GEN_PARENT; |
1da177e4 LT |
337 | } |
338 | *max_len = len; | |
339 | return type; | |
340 | } | |
341 | ||
6e91ea2b | 342 | int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len, |
d37065cd CH |
343 | int connectable) |
344 | { | |
39655164 | 345 | const struct export_operations *nop = dentry->d_sb->s_export_op; |
10f11c34 | 346 | int error; |
d37065cd | 347 | |
10f11c34 | 348 | if (nop->encode_fh) |
6e91ea2b | 349 | error = nop->encode_fh(dentry, fid->raw, max_len, connectable); |
10f11c34 | 350 | else |
6e91ea2b | 351 | error = export_encode_fh(dentry, fid, max_len, connectable); |
10f11c34 CH |
352 | |
353 | return error; | |
d37065cd CH |
354 | } |
355 | EXPORT_SYMBOL_GPL(exportfs_encode_fh); | |
356 | ||
6e91ea2b CH |
357 | struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, |
358 | int fh_len, int fileid_type, | |
359 | int (*acceptable)(void *, struct dentry *), void *context) | |
d37065cd | 360 | { |
39655164 | 361 | const struct export_operations *nop = mnt->mnt_sb->s_export_op; |
2596110a CH |
362 | struct dentry *result, *alias; |
363 | int err; | |
d37065cd | 364 | |
2596110a CH |
365 | /* |
366 | * Try to get any dentry for the given file handle from the filesystem. | |
367 | */ | |
368 | result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type); | |
369 | if (!result) | |
370 | result = ERR_PTR(-ESTALE); | |
371 | if (IS_ERR(result)) | |
372 | return result; | |
373 | ||
374 | if (S_ISDIR(result->d_inode->i_mode)) { | |
375 | /* | |
376 | * This request is for a directory. | |
377 | * | |
378 | * On the positive side there is only one dentry for each | |
379 | * directory inode. On the negative side this implies that we | |
380 | * to ensure our dentry is connected all the way up to the | |
381 | * filesystem root. | |
382 | */ | |
383 | if (result->d_flags & DCACHE_DISCONNECTED) { | |
e38f9817 | 384 | err = reconnect_path(mnt, result); |
2596110a CH |
385 | if (err) |
386 | goto err_result; | |
387 | } | |
388 | ||
389 | if (!acceptable(context, result)) { | |
390 | err = -EACCES; | |
391 | goto err_result; | |
392 | } | |
393 | ||
394 | return result; | |
10f11c34 | 395 | } else { |
2596110a CH |
396 | /* |
397 | * It's not a directory. Life is a little more complicated. | |
398 | */ | |
399 | struct dentry *target_dir, *nresult; | |
400 | char nbuf[NAME_MAX+1]; | |
401 | ||
402 | /* | |
403 | * See if either the dentry we just got from the filesystem | |
404 | * or any alias for it is acceptable. This is always true | |
405 | * if this filesystem is exported without the subtreecheck | |
406 | * option. If the filesystem is exported with the subtree | |
407 | * check option there's a fair chance we need to look at | |
408 | * the parent directory in the file handle and make sure | |
409 | * it's connected to the filesystem root. | |
410 | */ | |
411 | alias = find_acceptable_alias(result, acceptable, context); | |
412 | if (alias) | |
413 | return alias; | |
414 | ||
415 | /* | |
416 | * Try to extract a dentry for the parent directory from the | |
417 | * file handle. If this fails we'll have to give up. | |
418 | */ | |
419 | err = -ESTALE; | |
420 | if (!nop->fh_to_parent) | |
421 | goto err_result; | |
422 | ||
423 | target_dir = nop->fh_to_parent(mnt->mnt_sb, fid, | |
424 | fh_len, fileid_type); | |
425 | if (!target_dir) | |
426 | goto err_result; | |
427 | err = PTR_ERR(target_dir); | |
428 | if (IS_ERR(target_dir)) | |
429 | goto err_result; | |
430 | ||
431 | /* | |
432 | * And as usual we need to make sure the parent directory is | |
433 | * connected to the filesystem root. The VFS really doesn't | |
434 | * like disconnected directories.. | |
435 | */ | |
e38f9817 | 436 | err = reconnect_path(mnt, target_dir); |
2596110a CH |
437 | if (err) { |
438 | dput(target_dir); | |
439 | goto err_result; | |
440 | } | |
441 | ||
442 | /* | |
443 | * Now that we've got both a well-connected parent and a | |
444 | * dentry for the inode we're after, make sure that our | |
445 | * inode is actually connected to the parent. | |
446 | */ | |
e38f9817 | 447 | err = exportfs_get_name(mnt, target_dir, nbuf, result); |
2596110a CH |
448 | if (!err) { |
449 | mutex_lock(&target_dir->d_inode->i_mutex); | |
450 | nresult = lookup_one_len(nbuf, target_dir, | |
451 | strlen(nbuf)); | |
452 | mutex_unlock(&target_dir->d_inode->i_mutex); | |
453 | if (!IS_ERR(nresult)) { | |
454 | if (nresult->d_inode) { | |
455 | dput(result); | |
456 | result = nresult; | |
457 | } else | |
458 | dput(nresult); | |
459 | } | |
460 | } | |
461 | ||
462 | /* | |
463 | * At this point we are done with the parent, but it's pinned | |
464 | * by the child dentry anyway. | |
465 | */ | |
466 | dput(target_dir); | |
467 | ||
468 | /* | |
469 | * And finally make sure the dentry is actually acceptable | |
470 | * to NFSD. | |
471 | */ | |
472 | alias = find_acceptable_alias(result, acceptable, context); | |
473 | if (!alias) { | |
474 | err = -EACCES; | |
475 | goto err_result; | |
476 | } | |
477 | ||
478 | return alias; | |
10f11c34 CH |
479 | } |
480 | ||
2596110a CH |
481 | err_result: |
482 | dput(result); | |
483 | return ERR_PTR(err); | |
d37065cd CH |
484 | } |
485 | EXPORT_SYMBOL_GPL(exportfs_decode_fh); | |
486 | ||
1da177e4 | 487 | MODULE_LICENSE("GPL"); |