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 | |
765927b2 | 22 | static int get_name(const struct path *path, char *name, struct dentry *child); |
10f11c34 CH |
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; |
765927b2 | 29 | struct path path = {.mnt = mnt, .dentry = dir}; |
10f11c34 CH |
30 | |
31 | if (nop->get_name) | |
32 | return nop->get_name(dir, name, child); | |
33 | else | |
765927b2 | 34 | return get_name(&path, 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; | |
873feea0 | 46 | struct inode *inode; |
e2f99018 | 47 | |
fb66a198 CH |
48 | if (acceptable(context, result)) |
49 | return result; | |
50 | ||
873feea0 NP |
51 | inode = result->d_inode; |
52 | spin_lock(&inode->i_lock); | |
946e51f2 | 53 | hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) { |
dc0474be | 54 | dget(dentry); |
873feea0 | 55 | spin_unlock(&inode->i_lock); |
e2f99018 CH |
56 | if (toput) |
57 | dput(toput); | |
58 | if (dentry != result && acceptable(context, dentry)) { | |
59 | dput(result); | |
60 | return dentry; | |
61 | } | |
873feea0 | 62 | spin_lock(&inode->i_lock); |
e2f99018 CH |
63 | toput = dentry; |
64 | } | |
873feea0 | 65 | spin_unlock(&inode->i_lock); |
e2f99018 CH |
66 | |
67 | if (toput) | |
68 | dput(toput); | |
69 | return NULL; | |
70 | } | |
71 | ||
a056cc89 BF |
72 | static bool dentry_connected(struct dentry *dentry) |
73 | { | |
74 | dget(dentry); | |
75 | while (dentry->d_flags & DCACHE_DISCONNECTED) { | |
76 | struct dentry *parent = dget_parent(dentry); | |
77 | ||
78 | dput(dentry); | |
79 | if (IS_ROOT(dentry)) { | |
80 | dput(parent); | |
81 | return false; | |
82 | } | |
83 | dentry = parent; | |
84 | } | |
85 | dput(dentry); | |
86 | return true; | |
87 | } | |
88 | ||
0dbc018a BF |
89 | static void clear_disconnected(struct dentry *dentry) |
90 | { | |
91 | dget(dentry); | |
92 | while (dentry->d_flags & DCACHE_DISCONNECTED) { | |
93 | struct dentry *parent = dget_parent(dentry); | |
94 | ||
95 | WARN_ON_ONCE(IS_ROOT(dentry)); | |
96 | ||
97 | spin_lock(&dentry->d_lock); | |
98 | dentry->d_flags &= ~DCACHE_DISCONNECTED; | |
99 | spin_unlock(&dentry->d_lock); | |
100 | ||
101 | dput(dentry); | |
102 | dentry = parent; | |
103 | } | |
104 | dput(dentry); | |
105 | } | |
106 | ||
bbf7a8a3 BF |
107 | /* |
108 | * Reconnect a directory dentry with its parent. | |
109 | * | |
110 | * This can return a dentry, or NULL, or an error. | |
111 | * | |
112 | * In the first case the returned dentry is the parent of the given | |
113 | * dentry, and may itself need to be reconnected to its parent. | |
114 | * | |
115 | * In the NULL case, a concurrent VFS operation has either renamed or | |
116 | * removed this directory. The concurrent operation has reconnected our | |
117 | * dentry, so we no longer need to. | |
118 | */ | |
119 | static struct dentry *reconnect_one(struct vfsmount *mnt, | |
120 | struct dentry *dentry, char *nbuf) | |
121 | { | |
122 | struct dentry *parent; | |
123 | struct dentry *tmp; | |
124 | int err; | |
125 | ||
126 | parent = ERR_PTR(-EACCES); | |
127 | mutex_lock(&dentry->d_inode->i_mutex); | |
128 | if (mnt->mnt_sb->s_export_op->get_parent) | |
129 | parent = mnt->mnt_sb->s_export_op->get_parent(dentry); | |
130 | mutex_unlock(&dentry->d_inode->i_mutex); | |
131 | ||
132 | if (IS_ERR(parent)) { | |
133 | dprintk("%s: get_parent of %ld failed, err %d\n", | |
134 | __func__, dentry->d_inode->i_ino, PTR_ERR(parent)); | |
135 | return parent; | |
136 | } | |
137 | ||
138 | dprintk("%s: find name of %lu in %lu\n", __func__, | |
139 | dentry->d_inode->i_ino, parent->d_inode->i_ino); | |
140 | err = exportfs_get_name(mnt, parent, nbuf, dentry); | |
141 | if (err == -ENOENT) | |
142 | goto out_reconnected; | |
143 | if (err) | |
144 | goto out_err; | |
145 | dprintk("%s: found name: %s\n", __func__, nbuf); | |
146 | mutex_lock(&parent->d_inode->i_mutex); | |
147 | tmp = lookup_one_len(nbuf, parent, strlen(nbuf)); | |
148 | mutex_unlock(&parent->d_inode->i_mutex); | |
149 | if (IS_ERR(tmp)) { | |
150 | dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp)); | |
151 | goto out_err; | |
152 | } | |
153 | if (tmp != dentry) { | |
154 | dput(tmp); | |
155 | goto out_reconnected; | |
156 | } | |
157 | dput(tmp); | |
158 | if (IS_ROOT(dentry)) { | |
159 | err = -ESTALE; | |
160 | goto out_err; | |
161 | } | |
162 | return parent; | |
163 | ||
164 | out_err: | |
165 | dput(parent); | |
166 | return ERR_PTR(err); | |
167 | out_reconnected: | |
168 | dput(parent); | |
169 | /* | |
170 | * Someone must have renamed our entry into another parent, in | |
171 | * which case it has been reconnected by the rename. | |
172 | * | |
173 | * Or someone removed it entirely, in which case filehandle | |
174 | * lookup will succeed but the directory is now IS_DEAD and | |
175 | * subsequent operations on it will fail. | |
176 | * | |
177 | * Alternatively, maybe there was no race at all, and the | |
178 | * filesystem is just corrupt and gave us a parent that doesn't | |
179 | * actually contain any entry pointing to this inode. So, | |
180 | * double check that this worked and return -ESTALE if not: | |
181 | */ | |
182 | if (!dentry_connected(dentry)) | |
183 | return ERR_PTR(-ESTALE); | |
184 | return NULL; | |
185 | } | |
186 | ||
019ab801 CH |
187 | /* |
188 | * Make sure target_dir is fully connected to the dentry tree. | |
1da177e4 | 189 | * |
78cee9a8 BF |
190 | * On successful return, DCACHE_DISCONNECTED will be cleared on |
191 | * target_dir, and target_dir->d_parent->...->d_parent will reach the | |
192 | * root of the filesystem. | |
193 | * | |
194 | * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected. | |
195 | * But the converse is not true: target_dir may have DCACHE_DISCONNECTED | |
196 | * set but already be connected. In that case we'll verify the | |
197 | * connection to root and then clear the flag. | |
198 | * | |
199 | * Note that target_dir could be removed by a concurrent operation. In | |
200 | * that case reconnect_path may still succeed with target_dir fully | |
201 | * connected, but further operations using the filehandle will fail when | |
202 | * necessary (due to S_DEAD being set on the directory). | |
1da177e4 | 203 | */ |
019ab801 | 204 | static int |
f3f8e175 | 205 | reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf) |
1da177e4 | 206 | { |
f27c9298 | 207 | struct dentry *dentry, *parent; |
1da177e4 | 208 | |
f27c9298 | 209 | dentry = dget(target_dir); |
1da177e4 | 210 | |
f27c9298 | 211 | while (dentry->d_flags & DCACHE_DISCONNECTED) { |
efbf201f | 212 | BUG_ON(dentry == mnt->mnt_sb->s_root); |
854ff5ca | 213 | |
f27c9298 BF |
214 | if (IS_ROOT(dentry)) |
215 | parent = reconnect_one(mnt, dentry, nbuf); | |
216 | else | |
217 | parent = dget_parent(dentry); | |
218 | ||
219 | if (!parent) | |
0dbc018a | 220 | break; |
efbf201f | 221 | dput(dentry); |
f27c9298 BF |
222 | if (IS_ERR(parent)) |
223 | return PTR_ERR(parent); | |
224 | dentry = parent; | |
1da177e4 | 225 | } |
f27c9298 | 226 | dput(dentry); |
a056cc89 | 227 | clear_disconnected(target_dir); |
019ab801 CH |
228 | return 0; |
229 | } | |
230 | ||
1da177e4 | 231 | struct getdents_callback { |
5c0ba4e0 | 232 | struct dir_context ctx; |
1da177e4 LT |
233 | char *name; /* name that was found. It already points to a |
234 | buffer NAME_MAX+1 is size */ | |
950ee956 | 235 | u64 ino; /* the inum we are looking for */ |
1da177e4 LT |
236 | int found; /* inode matched? */ |
237 | int sequence; /* sequence counter */ | |
238 | }; | |
239 | ||
240 | /* | |
241 | * A rather strange filldir function to capture | |
242 | * the name matching the specified inode number. | |
243 | */ | |
ac7576f4 | 244 | static int filldir_one(struct dir_context *ctx, const char *name, int len, |
afefdbb2 | 245 | loff_t pos, u64 ino, unsigned int d_type) |
1da177e4 | 246 | { |
ac7576f4 MS |
247 | struct getdents_callback *buf = |
248 | container_of(ctx, struct getdents_callback, ctx); | |
1da177e4 LT |
249 | int result = 0; |
250 | ||
251 | buf->sequence++; | |
dfc59e2c | 252 | if (buf->ino == ino && len <= NAME_MAX) { |
1da177e4 LT |
253 | memcpy(buf->name, name, len); |
254 | buf->name[len] = '\0'; | |
255 | buf->found = 1; | |
256 | result = -1; | |
257 | } | |
258 | return result; | |
259 | } | |
260 | ||
261 | /** | |
262 | * get_name - default export_operations->get_name function | |
00f01791 | 263 | * @path: the directory in which to find a name |
1da177e4 LT |
264 | * @name: a pointer to a %NAME_MAX+1 char buffer to store the name |
265 | * @child: the dentry for the child directory. | |
266 | * | |
267 | * calls readdir on the parent until it finds an entry with | |
268 | * the same inode number as the child, and returns that. | |
269 | */ | |
765927b2 | 270 | static int get_name(const struct path *path, char *name, struct dentry *child) |
1da177e4 | 271 | { |
745ca247 | 272 | const struct cred *cred = current_cred(); |
765927b2 | 273 | struct inode *dir = path->dentry->d_inode; |
1da177e4 LT |
274 | int error; |
275 | struct file *file; | |
950ee956 BF |
276 | struct kstat stat; |
277 | struct path child_path = { | |
278 | .mnt = path->mnt, | |
279 | .dentry = child, | |
280 | }; | |
ac6614b7 AV |
281 | struct getdents_callback buffer = { |
282 | .ctx.actor = filldir_one, | |
283 | .name = name, | |
ac6614b7 | 284 | }; |
1da177e4 LT |
285 | |
286 | error = -ENOTDIR; | |
287 | if (!dir || !S_ISDIR(dir->i_mode)) | |
288 | goto out; | |
289 | error = -EINVAL; | |
290 | if (!dir->i_fop) | |
291 | goto out; | |
950ee956 BF |
292 | /* |
293 | * inode->i_ino is unsigned long, kstat->ino is u64, so the | |
294 | * former would be insufficient on 32-bit hosts when the | |
295 | * filesystem supports 64-bit inode numbers. So we need to | |
296 | * actually call ->getattr, not just read i_ino: | |
297 | */ | |
298 | error = vfs_getattr_nosec(&child_path, &stat); | |
299 | if (error) | |
300 | return error; | |
301 | buffer.ino = stat.ino; | |
1da177e4 LT |
302 | /* |
303 | * Open the directory ... | |
304 | */ | |
765927b2 | 305 | file = dentry_open(path, O_RDONLY, cred); |
1da177e4 LT |
306 | error = PTR_ERR(file); |
307 | if (IS_ERR(file)) | |
308 | goto out; | |
309 | ||
310 | error = -EINVAL; | |
2233f31a | 311 | if (!file->f_op->iterate) |
1da177e4 LT |
312 | goto out_close; |
313 | ||
1da177e4 LT |
314 | buffer.sequence = 0; |
315 | while (1) { | |
316 | int old_seq = buffer.sequence; | |
317 | ||
5c0ba4e0 | 318 | error = iterate_dir(file, &buffer.ctx); |
53c9c5c0 AV |
319 | if (buffer.found) { |
320 | error = 0; | |
321 | break; | |
322 | } | |
1da177e4 LT |
323 | |
324 | if (error < 0) | |
325 | break; | |
326 | ||
1da177e4 LT |
327 | error = -ENOENT; |
328 | if (old_seq == buffer.sequence) | |
329 | break; | |
330 | } | |
331 | ||
332 | out_close: | |
333 | fput(file); | |
334 | out: | |
335 | return error; | |
336 | } | |
337 | ||
1da177e4 LT |
338 | /** |
339 | * export_encode_fh - default export_operations->encode_fh function | |
b0b0382b | 340 | * @inode: the object to encode |
00f01791 | 341 | * @fid: where to store the file handle fragment |
1da177e4 | 342 | * @max_len: maximum length to store there |
b0b0382b | 343 | * @parent: parent directory inode, if wanted |
1da177e4 LT |
344 | * |
345 | * This default encode_fh function assumes that the 32 inode number | |
346 | * is suitable for locating an inode, and that the generation number | |
347 | * can be used to check that it is still valid. It places them in the | |
348 | * filehandle fragment where export_decode_fh expects to find them. | |
349 | */ | |
b0b0382b AV |
350 | static int export_encode_fh(struct inode *inode, struct fid *fid, |
351 | int *max_len, struct inode *parent) | |
1da177e4 | 352 | { |
1da177e4 | 353 | int len = *max_len; |
6e91ea2b | 354 | int type = FILEID_INO32_GEN; |
5fe0c237 | 355 | |
b0b0382b | 356 | if (parent && (len < 4)) { |
5fe0c237 | 357 | *max_len = 4; |
216b6cbd | 358 | return FILEID_INVALID; |
5fe0c237 AK |
359 | } else if (len < 2) { |
360 | *max_len = 2; | |
216b6cbd | 361 | return FILEID_INVALID; |
5fe0c237 | 362 | } |
1da177e4 LT |
363 | |
364 | len = 2; | |
6e91ea2b CH |
365 | fid->i32.ino = inode->i_ino; |
366 | fid->i32.gen = inode->i_generation; | |
b0b0382b | 367 | if (parent) { |
6e91ea2b CH |
368 | fid->i32.parent_ino = parent->i_ino; |
369 | fid->i32.parent_gen = parent->i_generation; | |
1da177e4 | 370 | len = 4; |
6e91ea2b | 371 | type = FILEID_INO32_GEN_PARENT; |
1da177e4 LT |
372 | } |
373 | *max_len = len; | |
374 | return type; | |
375 | } | |
376 | ||
711c7bf9 CG |
377 | int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid, |
378 | int *max_len, struct inode *parent) | |
379 | { | |
380 | const struct export_operations *nop = inode->i_sb->s_export_op; | |
381 | ||
382 | if (nop && nop->encode_fh) | |
383 | return nop->encode_fh(inode, fid->raw, max_len, parent); | |
384 | ||
385 | return export_encode_fh(inode, fid, max_len, parent); | |
386 | } | |
387 | EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh); | |
388 | ||
6e91ea2b | 389 | int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len, |
d37065cd CH |
390 | int connectable) |
391 | { | |
10f11c34 | 392 | int error; |
b0b0382b AV |
393 | struct dentry *p = NULL; |
394 | struct inode *inode = dentry->d_inode, *parent = NULL; | |
d37065cd | 395 | |
b0b0382b AV |
396 | if (connectable && !S_ISDIR(inode->i_mode)) { |
397 | p = dget_parent(dentry); | |
398 | /* | |
399 | * note that while p might've ceased to be our parent already, | |
400 | * it's still pinned by and still positive. | |
401 | */ | |
402 | parent = p->d_inode; | |
403 | } | |
711c7bf9 CG |
404 | |
405 | error = exportfs_encode_inode_fh(inode, fid, max_len, parent); | |
b0b0382b | 406 | dput(p); |
10f11c34 CH |
407 | |
408 | return error; | |
d37065cd CH |
409 | } |
410 | EXPORT_SYMBOL_GPL(exportfs_encode_fh); | |
411 | ||
6e91ea2b CH |
412 | struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, |
413 | int fh_len, int fileid_type, | |
414 | int (*acceptable)(void *, struct dentry *), void *context) | |
d37065cd | 415 | { |
39655164 | 416 | const struct export_operations *nop = mnt->mnt_sb->s_export_op; |
2596110a | 417 | struct dentry *result, *alias; |
f3f8e175 | 418 | char nbuf[NAME_MAX+1]; |
2596110a | 419 | int err; |
d37065cd | 420 | |
2596110a CH |
421 | /* |
422 | * Try to get any dentry for the given file handle from the filesystem. | |
423 | */ | |
becfd1f3 AK |
424 | if (!nop || !nop->fh_to_dentry) |
425 | return ERR_PTR(-ESTALE); | |
2596110a | 426 | result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type); |
a4f4d6df BF |
427 | if (!result) |
428 | result = ERR_PTR(-ESTALE); | |
2596110a CH |
429 | if (IS_ERR(result)) |
430 | return result; | |
431 | ||
432 | if (S_ISDIR(result->d_inode->i_mode)) { | |
433 | /* | |
434 | * This request is for a directory. | |
435 | * | |
436 | * On the positive side there is only one dentry for each | |
437 | * directory inode. On the negative side this implies that we | |
438 | * to ensure our dentry is connected all the way up to the | |
439 | * filesystem root. | |
440 | */ | |
441 | if (result->d_flags & DCACHE_DISCONNECTED) { | |
f3f8e175 | 442 | err = reconnect_path(mnt, result, nbuf); |
2596110a CH |
443 | if (err) |
444 | goto err_result; | |
445 | } | |
446 | ||
447 | if (!acceptable(context, result)) { | |
448 | err = -EACCES; | |
449 | goto err_result; | |
450 | } | |
451 | ||
452 | return result; | |
10f11c34 | 453 | } else { |
2596110a CH |
454 | /* |
455 | * It's not a directory. Life is a little more complicated. | |
456 | */ | |
457 | struct dentry *target_dir, *nresult; | |
2596110a CH |
458 | |
459 | /* | |
460 | * See if either the dentry we just got from the filesystem | |
461 | * or any alias for it is acceptable. This is always true | |
462 | * if this filesystem is exported without the subtreecheck | |
463 | * option. If the filesystem is exported with the subtree | |
464 | * check option there's a fair chance we need to look at | |
465 | * the parent directory in the file handle and make sure | |
466 | * it's connected to the filesystem root. | |
467 | */ | |
468 | alias = find_acceptable_alias(result, acceptable, context); | |
469 | if (alias) | |
470 | return alias; | |
471 | ||
472 | /* | |
473 | * Try to extract a dentry for the parent directory from the | |
474 | * file handle. If this fails we'll have to give up. | |
475 | */ | |
476 | err = -ESTALE; | |
477 | if (!nop->fh_to_parent) | |
478 | goto err_result; | |
479 | ||
480 | target_dir = nop->fh_to_parent(mnt->mnt_sb, fid, | |
481 | fh_len, fileid_type); | |
a4f4d6df BF |
482 | if (!target_dir) |
483 | goto err_result; | |
2596110a CH |
484 | err = PTR_ERR(target_dir); |
485 | if (IS_ERR(target_dir)) | |
486 | goto err_result; | |
487 | ||
488 | /* | |
489 | * And as usual we need to make sure the parent directory is | |
490 | * connected to the filesystem root. The VFS really doesn't | |
491 | * like disconnected directories.. | |
492 | */ | |
f3f8e175 | 493 | err = reconnect_path(mnt, target_dir, nbuf); |
2596110a CH |
494 | if (err) { |
495 | dput(target_dir); | |
496 | goto err_result; | |
497 | } | |
498 | ||
499 | /* | |
500 | * Now that we've got both a well-connected parent and a | |
501 | * dentry for the inode we're after, make sure that our | |
502 | * inode is actually connected to the parent. | |
503 | */ | |
e38f9817 | 504 | err = exportfs_get_name(mnt, target_dir, nbuf, result); |
2596110a CH |
505 | if (!err) { |
506 | mutex_lock(&target_dir->d_inode->i_mutex); | |
507 | nresult = lookup_one_len(nbuf, target_dir, | |
508 | strlen(nbuf)); | |
509 | mutex_unlock(&target_dir->d_inode->i_mutex); | |
510 | if (!IS_ERR(nresult)) { | |
511 | if (nresult->d_inode) { | |
512 | dput(result); | |
513 | result = nresult; | |
514 | } else | |
515 | dput(nresult); | |
516 | } | |
517 | } | |
518 | ||
519 | /* | |
520 | * At this point we are done with the parent, but it's pinned | |
521 | * by the child dentry anyway. | |
522 | */ | |
523 | dput(target_dir); | |
524 | ||
525 | /* | |
526 | * And finally make sure the dentry is actually acceptable | |
527 | * to NFSD. | |
528 | */ | |
529 | alias = find_acceptable_alias(result, acceptable, context); | |
530 | if (!alias) { | |
531 | err = -EACCES; | |
532 | goto err_result; | |
533 | } | |
534 | ||
535 | return alias; | |
10f11c34 CH |
536 | } |
537 | ||
2596110a CH |
538 | err_result: |
539 | dput(result); | |
540 | return ERR_PTR(err); | |
d37065cd CH |
541 | } |
542 | EXPORT_SYMBOL_GPL(exportfs_decode_fh); | |
543 | ||
1da177e4 | 544 | MODULE_LICENSE("GPL"); |