Commit | Line | Data |
---|---|---|
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 | |
dc7a0816 | 9 | * take a look at Documentation/filesystems/nfs/Exporting. |
e38f9817 | 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 | 16 | #include <linux/namei.h> |
745ca247 | 17 | #include <linux/sched.h> |
1da177e4 | 18 | |
10f11c34 | 19 | #define dprintk(fmt, args...) do{}while(0) |
1da177e4 | 20 | |
1da177e4 | 21 | |
e38f9817 | 22 | static int get_name(struct vfsmount *mnt, struct dentry *dentry, char *name, |
10f11c34 CH |
23 | struct dentry *child); |
24 | ||
25 | ||
e38f9817 CH |
26 | static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir, |
27 | char *name, struct dentry *child) | |
10f11c34 | 28 | { |
39655164 | 29 | const struct export_operations *nop = dir->d_sb->s_export_op; |
10f11c34 CH |
30 | |
31 | if (nop->get_name) | |
32 | return nop->get_name(dir, name, child); | |
33 | else | |
e38f9817 | 34 | return get_name(mnt, dir, name, child); |
10f11c34 | 35 | } |
1da177e4 | 36 | |
fb66a198 CH |
37 | /* |
38 | * Check if the dentry or any of it's aliases is acceptable. | |
39 | */ | |
e2f99018 CH |
40 | static struct dentry * |
41 | find_acceptable_alias(struct dentry *result, | |
42 | int (*acceptable)(void *context, struct dentry *dentry), | |
43 | void *context) | |
44 | { | |
45 | struct dentry *dentry, *toput = NULL; | |
46 | ||
fb66a198 CH |
47 | if (acceptable(context, result)) |
48 | return result; | |
49 | ||
b23fb0a6 | 50 | spin_lock(&dcache_inode_lock); |
e2f99018 | 51 | list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) { |
dc0474be | 52 | dget(dentry); |
b23fb0a6 | 53 | spin_unlock(&dcache_inode_lock); |
e2f99018 CH |
54 | if (toput) |
55 | dput(toput); | |
56 | if (dentry != result && acceptable(context, dentry)) { | |
57 | dput(result); | |
58 | return dentry; | |
59 | } | |
b23fb0a6 | 60 | spin_lock(&dcache_inode_lock); |
e2f99018 CH |
61 | toput = dentry; |
62 | } | |
b23fb0a6 | 63 | spin_unlock(&dcache_inode_lock); |
e2f99018 CH |
64 | |
65 | if (toput) | |
66 | dput(toput); | |
67 | return NULL; | |
68 | } | |
69 | ||
dd90b509 CH |
70 | /* |
71 | * Find root of a disconnected subtree and return a reference to it. | |
72 | */ | |
73 | static struct dentry * | |
74 | find_disconnected_root(struct dentry *dentry) | |
75 | { | |
76 | dget(dentry); | |
0461ee26 CH |
77 | while (!IS_ROOT(dentry)) { |
78 | struct dentry *parent = dget_parent(dentry); | |
79 | ||
80 | if (!(parent->d_flags & DCACHE_DISCONNECTED)) { | |
81 | dput(parent); | |
82 | break; | |
83 | } | |
84 | ||
dd90b509 CH |
85 | dput(dentry); |
86 | dentry = parent; | |
dd90b509 | 87 | } |
dd90b509 CH |
88 | return dentry; |
89 | } | |
90 | ||
019ab801 CH |
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 |
f3f8e175 | 97 | reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf) |
1da177e4 | 98 | { |
019ab801 CH |
99 | int noprogress = 0; |
100 | int err = -ESTALE; | |
1da177e4 LT |
101 | |
102 | /* | |
019ab801 | 103 | * It is possible that a confused file system might not let us complete |
1da177e4 LT |
104 | * the path to the root. For example, if get_parent returns a directory |
105 | * in which we cannot find a name for the child. While this implies a | |
106 | * very sick filesystem we don't want it to cause knfsd to spin. Hence | |
107 | * the noprogress counter. If we go through the loop 10 times (2 is | |
108 | * probably enough) without getting anywhere, we just give up | |
109 | */ | |
1da177e4 | 110 | while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { |
dd90b509 | 111 | struct dentry *pd = find_disconnected_root(target_dir); |
1da177e4 LT |
112 | |
113 | if (!IS_ROOT(pd)) { | |
114 | /* must have found a connected parent - great */ | |
115 | spin_lock(&pd->d_lock); | |
116 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
117 | spin_unlock(&pd->d_lock); | |
118 | noprogress = 0; | |
e38f9817 | 119 | } else if (pd == mnt->mnt_sb->s_root) { |
1da177e4 LT |
120 | printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); |
121 | spin_lock(&pd->d_lock); | |
122 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
123 | spin_unlock(&pd->d_lock); | |
124 | noprogress = 0; | |
125 | } else { | |
10f11c34 CH |
126 | /* |
127 | * We have hit the top of a disconnected path, try to | |
128 | * find parent and connect. | |
129 | * | |
130 | * Racing with some other process renaming a directory | |
131 | * isn't much of a problem here. If someone renames | |
132 | * the directory, it will end up properly connected, | |
133 | * which is what we want | |
134 | * | |
135 | * Getting the parent can't be supported generically, | |
136 | * the locking is too icky. | |
137 | * | |
138 | * Instead we just return EACCES. If server reboots | |
139 | * or inodes get flushed, you lose | |
1da177e4 | 140 | */ |
10f11c34 | 141 | struct dentry *ppd = ERR_PTR(-EACCES); |
1da177e4 LT |
142 | struct dentry *npd; |
143 | ||
1b1dcc1b | 144 | mutex_lock(&pd->d_inode->i_mutex); |
e38f9817 CH |
145 | if (mnt->mnt_sb->s_export_op->get_parent) |
146 | ppd = mnt->mnt_sb->s_export_op->get_parent(pd); | |
1b1dcc1b | 147 | mutex_unlock(&pd->d_inode->i_mutex); |
1da177e4 LT |
148 | |
149 | if (IS_ERR(ppd)) { | |
150 | err = PTR_ERR(ppd); | |
019ab801 | 151 | dprintk("%s: get_parent of %ld failed, err %d\n", |
8e24eea7 | 152 | __func__, pd->d_inode->i_ino, err); |
1da177e4 LT |
153 | dput(pd); |
154 | break; | |
155 | } | |
019ab801 | 156 | |
8e24eea7 | 157 | dprintk("%s: find name of %lu in %lu\n", __func__, |
019ab801 | 158 | pd->d_inode->i_ino, ppd->d_inode->i_ino); |
e38f9817 | 159 | err = exportfs_get_name(mnt, ppd, nbuf, pd); |
1da177e4 LT |
160 | if (err) { |
161 | dput(ppd); | |
162 | dput(pd); | |
163 | if (err == -ENOENT) | |
164 | /* some race between get_parent and | |
165 | * get_name? just try again | |
166 | */ | |
167 | continue; | |
168 | break; | |
169 | } | |
8e24eea7 | 170 | dprintk("%s: found name: %s\n", __func__, nbuf); |
1b1dcc1b | 171 | mutex_lock(&ppd->d_inode->i_mutex); |
1da177e4 | 172 | npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); |
1b1dcc1b | 173 | mutex_unlock(&ppd->d_inode->i_mutex); |
1da177e4 LT |
174 | if (IS_ERR(npd)) { |
175 | err = PTR_ERR(npd); | |
019ab801 | 176 | dprintk("%s: lookup failed: %d\n", |
8e24eea7 | 177 | __func__, err); |
1da177e4 LT |
178 | dput(ppd); |
179 | dput(pd); | |
180 | break; | |
181 | } | |
182 | /* we didn't really want npd, we really wanted | |
183 | * a side-effect of the lookup. | |
184 | * hopefully, npd == pd, though it isn't really | |
185 | * a problem if it isn't | |
186 | */ | |
187 | if (npd == pd) | |
188 | noprogress = 0; | |
189 | else | |
8e24eea7 | 190 | printk("%s: npd != pd\n", __func__); |
1da177e4 LT |
191 | dput(npd); |
192 | dput(ppd); | |
193 | if (IS_ROOT(pd)) { | |
194 | /* something went wrong, we have to give up */ | |
195 | dput(pd); | |
196 | break; | |
197 | } | |
198 | } | |
199 | dput(pd); | |
200 | } | |
201 | ||
202 | if (target_dir->d_flags & DCACHE_DISCONNECTED) { | |
203 | /* something went wrong - oh-well */ | |
204 | if (!err) | |
205 | err = -ESTALE; | |
019ab801 | 206 | return err; |
1da177e4 | 207 | } |
019ab801 CH |
208 | |
209 | return 0; | |
210 | } | |
211 | ||
1da177e4 LT |
212 | struct getdents_callback { |
213 | char *name; /* name that was found. It already points to a | |
214 | buffer NAME_MAX+1 is size */ | |
215 | unsigned long ino; /* the inum we are looking for */ | |
216 | int found; /* inode matched? */ | |
217 | int sequence; /* sequence counter */ | |
218 | }; | |
219 | ||
220 | /* | |
221 | * A rather strange filldir function to capture | |
222 | * the name matching the specified inode number. | |
223 | */ | |
224 | static int filldir_one(void * __buf, const char * name, int len, | |
afefdbb2 | 225 | loff_t pos, u64 ino, unsigned int d_type) |
1da177e4 LT |
226 | { |
227 | struct getdents_callback *buf = __buf; | |
228 | int result = 0; | |
229 | ||
230 | buf->sequence++; | |
231 | if (buf->ino == ino) { | |
232 | memcpy(buf->name, name, len); | |
233 | buf->name[len] = '\0'; | |
234 | buf->found = 1; | |
235 | result = -1; | |
236 | } | |
237 | return result; | |
238 | } | |
239 | ||
240 | /** | |
241 | * get_name - default export_operations->get_name function | |
242 | * @dentry: the directory in which to find a name | |
243 | * @name: a pointer to a %NAME_MAX+1 char buffer to store the name | |
244 | * @child: the dentry for the child directory. | |
245 | * | |
246 | * calls readdir on the parent until it finds an entry with | |
247 | * the same inode number as the child, and returns that. | |
248 | */ | |
e38f9817 CH |
249 | static int get_name(struct vfsmount *mnt, struct dentry *dentry, |
250 | char *name, struct dentry *child) | |
1da177e4 | 251 | { |
745ca247 | 252 | const struct cred *cred = current_cred(); |
1da177e4 LT |
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 | */ | |
745ca247 | 267 | file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred); |
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); | |
53c9c5c0 AV |
284 | if (buffer.found) { |
285 | error = 0; | |
286 | break; | |
287 | } | |
1da177e4 LT |
288 | |
289 | if (error < 0) | |
290 | break; | |
291 | ||
1da177e4 LT |
292 | error = -ENOENT; |
293 | if (old_seq == buffer.sequence) | |
294 | break; | |
295 | } | |
296 | ||
297 | out_close: | |
298 | fput(file); | |
299 | out: | |
300 | return error; | |
301 | } | |
302 | ||
1da177e4 LT |
303 | /** |
304 | * export_encode_fh - default export_operations->encode_fh function | |
305 | * @dentry: the dentry to encode | |
306 | * @fh: where to store the file handle fragment | |
307 | * @max_len: maximum length to store there | |
308 | * @connectable: whether to store parent information | |
309 | * | |
310 | * This default encode_fh function assumes that the 32 inode number | |
311 | * is suitable for locating an inode, and that the generation number | |
312 | * can be used to check that it is still valid. It places them in the | |
313 | * filehandle fragment where export_decode_fh expects to find them. | |
314 | */ | |
6e91ea2b CH |
315 | static int export_encode_fh(struct dentry *dentry, struct fid *fid, |
316 | int *max_len, int connectable) | |
1da177e4 LT |
317 | { |
318 | struct inode * inode = dentry->d_inode; | |
319 | int len = *max_len; | |
6e91ea2b | 320 | int type = FILEID_INO32_GEN; |
1da177e4 LT |
321 | |
322 | if (len < 2 || (connectable && len < 4)) | |
323 | return 255; | |
324 | ||
325 | len = 2; | |
6e91ea2b CH |
326 | fid->i32.ino = inode->i_ino; |
327 | fid->i32.gen = inode->i_generation; | |
1da177e4 LT |
328 | if (connectable && !S_ISDIR(inode->i_mode)) { |
329 | struct inode *parent; | |
330 | ||
331 | spin_lock(&dentry->d_lock); | |
332 | parent = dentry->d_parent->d_inode; | |
6e91ea2b CH |
333 | fid->i32.parent_ino = parent->i_ino; |
334 | fid->i32.parent_gen = parent->i_generation; | |
1da177e4 LT |
335 | spin_unlock(&dentry->d_lock); |
336 | len = 4; | |
6e91ea2b | 337 | type = FILEID_INO32_GEN_PARENT; |
1da177e4 LT |
338 | } |
339 | *max_len = len; | |
340 | return type; | |
341 | } | |
342 | ||
6e91ea2b | 343 | int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len, |
d37065cd CH |
344 | int connectable) |
345 | { | |
39655164 | 346 | const struct export_operations *nop = dentry->d_sb->s_export_op; |
10f11c34 | 347 | int error; |
d37065cd | 348 | |
10f11c34 | 349 | if (nop->encode_fh) |
6e91ea2b | 350 | error = nop->encode_fh(dentry, fid->raw, max_len, connectable); |
10f11c34 | 351 | else |
6e91ea2b | 352 | error = export_encode_fh(dentry, fid, max_len, connectable); |
10f11c34 CH |
353 | |
354 | return error; | |
d37065cd CH |
355 | } |
356 | EXPORT_SYMBOL_GPL(exportfs_encode_fh); | |
357 | ||
6e91ea2b CH |
358 | struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, |
359 | int fh_len, int fileid_type, | |
360 | int (*acceptable)(void *, struct dentry *), void *context) | |
d37065cd | 361 | { |
39655164 | 362 | const struct export_operations *nop = mnt->mnt_sb->s_export_op; |
2596110a | 363 | struct dentry *result, *alias; |
f3f8e175 | 364 | char nbuf[NAME_MAX+1]; |
2596110a | 365 | int err; |
d37065cd | 366 | |
2596110a CH |
367 | /* |
368 | * Try to get any dentry for the given file handle from the filesystem. | |
369 | */ | |
370 | result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type); | |
a4f4d6df BF |
371 | if (!result) |
372 | result = ERR_PTR(-ESTALE); | |
2596110a CH |
373 | if (IS_ERR(result)) |
374 | return result; | |
375 | ||
376 | if (S_ISDIR(result->d_inode->i_mode)) { | |
377 | /* | |
378 | * This request is for a directory. | |
379 | * | |
380 | * On the positive side there is only one dentry for each | |
381 | * directory inode. On the negative side this implies that we | |
382 | * to ensure our dentry is connected all the way up to the | |
383 | * filesystem root. | |
384 | */ | |
385 | if (result->d_flags & DCACHE_DISCONNECTED) { | |
f3f8e175 | 386 | err = reconnect_path(mnt, result, nbuf); |
2596110a CH |
387 | if (err) |
388 | goto err_result; | |
389 | } | |
390 | ||
391 | if (!acceptable(context, result)) { | |
392 | err = -EACCES; | |
393 | goto err_result; | |
394 | } | |
395 | ||
396 | return result; | |
10f11c34 | 397 | } else { |
2596110a CH |
398 | /* |
399 | * It's not a directory. Life is a little more complicated. | |
400 | */ | |
401 | struct dentry *target_dir, *nresult; | |
2596110a CH |
402 | |
403 | /* | |
404 | * See if either the dentry we just got from the filesystem | |
405 | * or any alias for it is acceptable. This is always true | |
406 | * if this filesystem is exported without the subtreecheck | |
407 | * option. If the filesystem is exported with the subtree | |
408 | * check option there's a fair chance we need to look at | |
409 | * the parent directory in the file handle and make sure | |
410 | * it's connected to the filesystem root. | |
411 | */ | |
412 | alias = find_acceptable_alias(result, acceptable, context); | |
413 | if (alias) | |
414 | return alias; | |
415 | ||
416 | /* | |
417 | * Try to extract a dentry for the parent directory from the | |
418 | * file handle. If this fails we'll have to give up. | |
419 | */ | |
420 | err = -ESTALE; | |
421 | if (!nop->fh_to_parent) | |
422 | goto err_result; | |
423 | ||
424 | target_dir = nop->fh_to_parent(mnt->mnt_sb, fid, | |
425 | fh_len, fileid_type); | |
a4f4d6df BF |
426 | if (!target_dir) |
427 | goto err_result; | |
2596110a CH |
428 | err = PTR_ERR(target_dir); |
429 | if (IS_ERR(target_dir)) | |
430 | goto err_result; | |
431 | ||
432 | /* | |
433 | * And as usual we need to make sure the parent directory is | |
434 | * connected to the filesystem root. The VFS really doesn't | |
435 | * like disconnected directories.. | |
436 | */ | |
f3f8e175 | 437 | err = reconnect_path(mnt, target_dir, nbuf); |
2596110a CH |
438 | if (err) { |
439 | dput(target_dir); | |
440 | goto err_result; | |
441 | } | |
442 | ||
443 | /* | |
444 | * Now that we've got both a well-connected parent and a | |
445 | * dentry for the inode we're after, make sure that our | |
446 | * inode is actually connected to the parent. | |
447 | */ | |
e38f9817 | 448 | err = exportfs_get_name(mnt, target_dir, nbuf, result); |
2596110a CH |
449 | if (!err) { |
450 | mutex_lock(&target_dir->d_inode->i_mutex); | |
451 | nresult = lookup_one_len(nbuf, target_dir, | |
452 | strlen(nbuf)); | |
453 | mutex_unlock(&target_dir->d_inode->i_mutex); | |
454 | if (!IS_ERR(nresult)) { | |
455 | if (nresult->d_inode) { | |
456 | dput(result); | |
457 | result = nresult; | |
458 | } else | |
459 | dput(nresult); | |
460 | } | |
461 | } | |
462 | ||
463 | /* | |
464 | * At this point we are done with the parent, but it's pinned | |
465 | * by the child dentry anyway. | |
466 | */ | |
467 | dput(target_dir); | |
468 | ||
469 | /* | |
470 | * And finally make sure the dentry is actually acceptable | |
471 | * to NFSD. | |
472 | */ | |
473 | alias = find_acceptable_alias(result, acceptable, context); | |
474 | if (!alias) { | |
475 | err = -EACCES; | |
476 | goto err_result; | |
477 | } | |
478 | ||
479 | return alias; | |
10f11c34 CH |
480 | } |
481 | ||
2596110a CH |
482 | err_result: |
483 | dput(result); | |
484 | return ERR_PTR(err); | |
d37065cd CH |
485 | } |
486 | EXPORT_SYMBOL_GPL(exportfs_decode_fh); | |
487 | ||
1da177e4 | 488 | MODULE_LICENSE("GPL"); |