Commit | Line | Data |
---|---|---|
e9be9d5e MS |
1 | /* |
2 | * | |
3 | * Copyright (C) 2011 Novell Inc. | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify it | |
6 | * under the terms of the GNU General Public License version 2 as published by | |
7 | * the Free Software Foundation. | |
8 | */ | |
9 | ||
10 | #include <linux/fs.h> | |
11 | #include <linux/namei.h> | |
12 | #include <linux/xattr.h> | |
13 | #include <linux/security.h> | |
14 | #include <linux/mount.h> | |
15 | #include <linux/slab.h> | |
16 | #include <linux/parser.h> | |
17 | #include <linux/module.h> | |
18 | #include <linux/sched.h> | |
cc259639 | 19 | #include <linux/statfs.h> |
f45827e8 | 20 | #include <linux/seq_file.h> |
e9be9d5e MS |
21 | #include "overlayfs.h" |
22 | ||
23 | MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); | |
24 | MODULE_DESCRIPTION("Overlay filesystem"); | |
25 | MODULE_LICENSE("GPL"); | |
26 | ||
ef94b186 | 27 | #define OVERLAYFS_SUPER_MAGIC 0x794c7630 |
cc259639 | 28 | |
f45827e8 EZ |
29 | struct ovl_config { |
30 | char *lowerdir; | |
31 | char *upperdir; | |
32 | char *workdir; | |
33 | }; | |
34 | ||
e9be9d5e MS |
35 | /* private information held for overlayfs's superblock */ |
36 | struct ovl_fs { | |
37 | struct vfsmount *upper_mnt; | |
38 | struct vfsmount *lower_mnt; | |
39 | struct dentry *workdir; | |
cc259639 | 40 | long lower_namelen; |
f45827e8 EZ |
41 | /* pathnames of lower and upper dirs, for show_options */ |
42 | struct ovl_config config; | |
e9be9d5e MS |
43 | }; |
44 | ||
45 | struct ovl_dir_cache; | |
46 | ||
47 | /* private information held for every overlayfs dentry */ | |
48 | struct ovl_entry { | |
49 | struct dentry *__upperdentry; | |
50 | struct dentry *lowerdentry; | |
51 | struct ovl_dir_cache *cache; | |
52 | union { | |
53 | struct { | |
54 | u64 version; | |
55 | bool opaque; | |
56 | }; | |
57 | struct rcu_head rcu; | |
58 | }; | |
59 | }; | |
60 | ||
61 | const char *ovl_opaque_xattr = "trusted.overlay.opaque"; | |
62 | ||
63 | ||
64 | enum ovl_path_type ovl_path_type(struct dentry *dentry) | |
65 | { | |
66 | struct ovl_entry *oe = dentry->d_fsdata; | |
67 | ||
68 | if (oe->__upperdentry) { | |
69 | if (oe->lowerdentry) { | |
70 | if (S_ISDIR(dentry->d_inode->i_mode)) | |
71 | return OVL_PATH_MERGE; | |
72 | else | |
73 | return OVL_PATH_UPPER; | |
74 | } else { | |
75 | if (oe->opaque) | |
76 | return OVL_PATH_UPPER; | |
77 | else | |
78 | return OVL_PATH_PURE_UPPER; | |
79 | } | |
80 | } else { | |
81 | return OVL_PATH_LOWER; | |
82 | } | |
83 | } | |
84 | ||
85 | static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe) | |
86 | { | |
71d50928 | 87 | return lockless_dereference(oe->__upperdentry); |
e9be9d5e MS |
88 | } |
89 | ||
90 | void ovl_path_upper(struct dentry *dentry, struct path *path) | |
91 | { | |
92 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; | |
93 | struct ovl_entry *oe = dentry->d_fsdata; | |
94 | ||
95 | path->mnt = ofs->upper_mnt; | |
96 | path->dentry = ovl_upperdentry_dereference(oe); | |
97 | } | |
98 | ||
99 | enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path) | |
100 | { | |
101 | ||
102 | enum ovl_path_type type = ovl_path_type(dentry); | |
103 | ||
104 | if (type == OVL_PATH_LOWER) | |
105 | ovl_path_lower(dentry, path); | |
106 | else | |
107 | ovl_path_upper(dentry, path); | |
108 | ||
109 | return type; | |
110 | } | |
111 | ||
112 | struct dentry *ovl_dentry_upper(struct dentry *dentry) | |
113 | { | |
114 | struct ovl_entry *oe = dentry->d_fsdata; | |
115 | ||
116 | return ovl_upperdentry_dereference(oe); | |
117 | } | |
118 | ||
119 | struct dentry *ovl_dentry_lower(struct dentry *dentry) | |
120 | { | |
121 | struct ovl_entry *oe = dentry->d_fsdata; | |
122 | ||
123 | return oe->lowerdentry; | |
124 | } | |
125 | ||
126 | struct dentry *ovl_dentry_real(struct dentry *dentry) | |
127 | { | |
128 | struct ovl_entry *oe = dentry->d_fsdata; | |
129 | struct dentry *realdentry; | |
130 | ||
131 | realdentry = ovl_upperdentry_dereference(oe); | |
132 | if (!realdentry) | |
133 | realdentry = oe->lowerdentry; | |
134 | ||
135 | return realdentry; | |
136 | } | |
137 | ||
138 | struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper) | |
139 | { | |
140 | struct dentry *realdentry; | |
141 | ||
142 | realdentry = ovl_upperdentry_dereference(oe); | |
143 | if (realdentry) { | |
144 | *is_upper = true; | |
145 | } else { | |
146 | realdentry = oe->lowerdentry; | |
147 | *is_upper = false; | |
148 | } | |
149 | return realdentry; | |
150 | } | |
151 | ||
152 | struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry) | |
153 | { | |
154 | struct ovl_entry *oe = dentry->d_fsdata; | |
155 | ||
156 | return oe->cache; | |
157 | } | |
158 | ||
159 | void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache) | |
160 | { | |
161 | struct ovl_entry *oe = dentry->d_fsdata; | |
162 | ||
163 | oe->cache = cache; | |
164 | } | |
165 | ||
166 | void ovl_path_lower(struct dentry *dentry, struct path *path) | |
167 | { | |
168 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; | |
169 | struct ovl_entry *oe = dentry->d_fsdata; | |
170 | ||
171 | path->mnt = ofs->lower_mnt; | |
172 | path->dentry = oe->lowerdentry; | |
173 | } | |
174 | ||
175 | int ovl_want_write(struct dentry *dentry) | |
176 | { | |
177 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; | |
178 | return mnt_want_write(ofs->upper_mnt); | |
179 | } | |
180 | ||
181 | void ovl_drop_write(struct dentry *dentry) | |
182 | { | |
183 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; | |
184 | mnt_drop_write(ofs->upper_mnt); | |
185 | } | |
186 | ||
187 | struct dentry *ovl_workdir(struct dentry *dentry) | |
188 | { | |
189 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; | |
190 | return ofs->workdir; | |
191 | } | |
192 | ||
193 | bool ovl_dentry_is_opaque(struct dentry *dentry) | |
194 | { | |
195 | struct ovl_entry *oe = dentry->d_fsdata; | |
196 | return oe->opaque; | |
197 | } | |
198 | ||
199 | void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque) | |
200 | { | |
201 | struct ovl_entry *oe = dentry->d_fsdata; | |
202 | oe->opaque = opaque; | |
203 | } | |
204 | ||
205 | void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry) | |
206 | { | |
207 | struct ovl_entry *oe = dentry->d_fsdata; | |
208 | ||
209 | WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex)); | |
210 | WARN_ON(oe->__upperdentry); | |
211 | BUG_ON(!upperdentry->d_inode); | |
212 | /* | |
213 | * Make sure upperdentry is consistent before making it visible to | |
214 | * ovl_upperdentry_dereference(). | |
215 | */ | |
216 | smp_wmb(); | |
217 | oe->__upperdentry = upperdentry; | |
218 | } | |
219 | ||
220 | void ovl_dentry_version_inc(struct dentry *dentry) | |
221 | { | |
222 | struct ovl_entry *oe = dentry->d_fsdata; | |
223 | ||
224 | WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); | |
225 | oe->version++; | |
226 | } | |
227 | ||
228 | u64 ovl_dentry_version_get(struct dentry *dentry) | |
229 | { | |
230 | struct ovl_entry *oe = dentry->d_fsdata; | |
231 | ||
232 | WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); | |
233 | return oe->version; | |
234 | } | |
235 | ||
236 | bool ovl_is_whiteout(struct dentry *dentry) | |
237 | { | |
238 | struct inode *inode = dentry->d_inode; | |
239 | ||
240 | return inode && IS_WHITEOUT(inode); | |
241 | } | |
242 | ||
243 | static bool ovl_is_opaquedir(struct dentry *dentry) | |
244 | { | |
245 | int res; | |
246 | char val; | |
247 | struct inode *inode = dentry->d_inode; | |
248 | ||
249 | if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr) | |
250 | return false; | |
251 | ||
252 | res = inode->i_op->getxattr(dentry, ovl_opaque_xattr, &val, 1); | |
253 | if (res == 1 && val == 'y') | |
254 | return true; | |
255 | ||
256 | return false; | |
257 | } | |
258 | ||
259 | static void ovl_dentry_release(struct dentry *dentry) | |
260 | { | |
261 | struct ovl_entry *oe = dentry->d_fsdata; | |
262 | ||
263 | if (oe) { | |
264 | dput(oe->__upperdentry); | |
265 | dput(oe->lowerdentry); | |
266 | kfree_rcu(oe, rcu); | |
267 | } | |
268 | } | |
269 | ||
270 | static const struct dentry_operations ovl_dentry_operations = { | |
271 | .d_release = ovl_dentry_release, | |
272 | }; | |
273 | ||
274 | static struct ovl_entry *ovl_alloc_entry(void) | |
275 | { | |
276 | return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL); | |
277 | } | |
278 | ||
279 | static inline struct dentry *ovl_lookup_real(struct dentry *dir, | |
280 | struct qstr *name) | |
281 | { | |
282 | struct dentry *dentry; | |
283 | ||
284 | mutex_lock(&dir->d_inode->i_mutex); | |
285 | dentry = lookup_one_len(name->name, dir, name->len); | |
286 | mutex_unlock(&dir->d_inode->i_mutex); | |
287 | ||
288 | if (IS_ERR(dentry)) { | |
289 | if (PTR_ERR(dentry) == -ENOENT) | |
290 | dentry = NULL; | |
291 | } else if (!dentry->d_inode) { | |
292 | dput(dentry); | |
293 | dentry = NULL; | |
294 | } | |
295 | return dentry; | |
296 | } | |
297 | ||
298 | struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, | |
299 | unsigned int flags) | |
300 | { | |
301 | struct ovl_entry *oe; | |
302 | struct dentry *upperdir; | |
303 | struct dentry *lowerdir; | |
304 | struct dentry *upperdentry = NULL; | |
305 | struct dentry *lowerdentry = NULL; | |
306 | struct inode *inode = NULL; | |
307 | int err; | |
308 | ||
309 | err = -ENOMEM; | |
310 | oe = ovl_alloc_entry(); | |
311 | if (!oe) | |
312 | goto out; | |
313 | ||
314 | upperdir = ovl_dentry_upper(dentry->d_parent); | |
315 | lowerdir = ovl_dentry_lower(dentry->d_parent); | |
316 | ||
317 | if (upperdir) { | |
318 | upperdentry = ovl_lookup_real(upperdir, &dentry->d_name); | |
319 | err = PTR_ERR(upperdentry); | |
320 | if (IS_ERR(upperdentry)) | |
321 | goto out_put_dir; | |
322 | ||
323 | if (lowerdir && upperdentry) { | |
324 | if (ovl_is_whiteout(upperdentry)) { | |
325 | dput(upperdentry); | |
326 | upperdentry = NULL; | |
327 | oe->opaque = true; | |
328 | } else if (ovl_is_opaquedir(upperdentry)) { | |
329 | oe->opaque = true; | |
330 | } | |
331 | } | |
332 | } | |
333 | if (lowerdir && !oe->opaque) { | |
334 | lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name); | |
335 | err = PTR_ERR(lowerdentry); | |
336 | if (IS_ERR(lowerdentry)) | |
337 | goto out_dput_upper; | |
338 | } | |
339 | ||
340 | if (lowerdentry && upperdentry && | |
341 | (!S_ISDIR(upperdentry->d_inode->i_mode) || | |
342 | !S_ISDIR(lowerdentry->d_inode->i_mode))) { | |
343 | dput(lowerdentry); | |
344 | lowerdentry = NULL; | |
345 | oe->opaque = true; | |
346 | } | |
347 | ||
348 | if (lowerdentry || upperdentry) { | |
349 | struct dentry *realdentry; | |
350 | ||
351 | realdentry = upperdentry ? upperdentry : lowerdentry; | |
352 | err = -ENOMEM; | |
353 | inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, | |
354 | oe); | |
355 | if (!inode) | |
356 | goto out_dput; | |
357 | ovl_copyattr(realdentry->d_inode, inode); | |
358 | } | |
359 | ||
360 | oe->__upperdentry = upperdentry; | |
361 | oe->lowerdentry = lowerdentry; | |
362 | ||
363 | dentry->d_fsdata = oe; | |
364 | d_add(dentry, inode); | |
365 | ||
366 | return NULL; | |
367 | ||
368 | out_dput: | |
369 | dput(lowerdentry); | |
370 | out_dput_upper: | |
371 | dput(upperdentry); | |
372 | out_put_dir: | |
373 | kfree(oe); | |
374 | out: | |
375 | return ERR_PTR(err); | |
376 | } | |
377 | ||
378 | struct file *ovl_path_open(struct path *path, int flags) | |
379 | { | |
380 | return dentry_open(path, flags, current_cred()); | |
381 | } | |
382 | ||
383 | static void ovl_put_super(struct super_block *sb) | |
384 | { | |
385 | struct ovl_fs *ufs = sb->s_fs_info; | |
386 | ||
387 | dput(ufs->workdir); | |
388 | mntput(ufs->upper_mnt); | |
389 | mntput(ufs->lower_mnt); | |
390 | ||
f45827e8 EZ |
391 | kfree(ufs->config.lowerdir); |
392 | kfree(ufs->config.upperdir); | |
393 | kfree(ufs->config.workdir); | |
e9be9d5e MS |
394 | kfree(ufs); |
395 | } | |
396 | ||
cc259639 AW |
397 | /** |
398 | * ovl_statfs | |
399 | * @sb: The overlayfs super block | |
400 | * @buf: The struct kstatfs to fill in with stats | |
401 | * | |
402 | * Get the filesystem statistics. As writes always target the upper layer | |
403 | * filesystem pass the statfs to the same filesystem. | |
404 | */ | |
405 | static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) | |
406 | { | |
407 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; | |
408 | struct dentry *root_dentry = dentry->d_sb->s_root; | |
409 | struct path path; | |
410 | int err; | |
411 | ||
412 | ovl_path_upper(root_dentry, &path); | |
413 | ||
414 | err = vfs_statfs(&path, buf); | |
415 | if (!err) { | |
416 | buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen); | |
417 | buf->f_type = OVERLAYFS_SUPER_MAGIC; | |
418 | } | |
419 | ||
420 | return err; | |
421 | } | |
422 | ||
f45827e8 EZ |
423 | /** |
424 | * ovl_show_options | |
425 | * | |
426 | * Prints the mount options for a given superblock. | |
427 | * Returns zero; does not fail. | |
428 | */ | |
429 | static int ovl_show_options(struct seq_file *m, struct dentry *dentry) | |
430 | { | |
431 | struct super_block *sb = dentry->d_sb; | |
432 | struct ovl_fs *ufs = sb->s_fs_info; | |
433 | ||
434 | seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir); | |
435 | seq_printf(m, ",upperdir=%s", ufs->config.upperdir); | |
436 | seq_printf(m, ",workdir=%s", ufs->config.workdir); | |
437 | return 0; | |
438 | } | |
439 | ||
e9be9d5e MS |
440 | static const struct super_operations ovl_super_operations = { |
441 | .put_super = ovl_put_super, | |
cc259639 | 442 | .statfs = ovl_statfs, |
f45827e8 | 443 | .show_options = ovl_show_options, |
e9be9d5e MS |
444 | }; |
445 | ||
446 | enum { | |
447 | OPT_LOWERDIR, | |
448 | OPT_UPPERDIR, | |
449 | OPT_WORKDIR, | |
450 | OPT_ERR, | |
451 | }; | |
452 | ||
453 | static const match_table_t ovl_tokens = { | |
454 | {OPT_LOWERDIR, "lowerdir=%s"}, | |
455 | {OPT_UPPERDIR, "upperdir=%s"}, | |
456 | {OPT_WORKDIR, "workdir=%s"}, | |
457 | {OPT_ERR, NULL} | |
458 | }; | |
459 | ||
91c77947 MS |
460 | static char *ovl_next_opt(char **s) |
461 | { | |
462 | char *sbegin = *s; | |
463 | char *p; | |
464 | ||
465 | if (sbegin == NULL) | |
466 | return NULL; | |
467 | ||
468 | for (p = sbegin; *p; p++) { | |
469 | if (*p == '\\') { | |
470 | p++; | |
471 | if (!*p) | |
472 | break; | |
473 | } else if (*p == ',') { | |
474 | *p = '\0'; | |
475 | *s = p + 1; | |
476 | return sbegin; | |
477 | } | |
478 | } | |
479 | *s = NULL; | |
480 | return sbegin; | |
481 | } | |
482 | ||
e9be9d5e MS |
483 | static int ovl_parse_opt(char *opt, struct ovl_config *config) |
484 | { | |
485 | char *p; | |
486 | ||
91c77947 | 487 | while ((p = ovl_next_opt(&opt)) != NULL) { |
e9be9d5e MS |
488 | int token; |
489 | substring_t args[MAX_OPT_ARGS]; | |
490 | ||
491 | if (!*p) | |
492 | continue; | |
493 | ||
494 | token = match_token(p, ovl_tokens, args); | |
495 | switch (token) { | |
496 | case OPT_UPPERDIR: | |
497 | kfree(config->upperdir); | |
498 | config->upperdir = match_strdup(&args[0]); | |
499 | if (!config->upperdir) | |
500 | return -ENOMEM; | |
501 | break; | |
502 | ||
503 | case OPT_LOWERDIR: | |
504 | kfree(config->lowerdir); | |
505 | config->lowerdir = match_strdup(&args[0]); | |
506 | if (!config->lowerdir) | |
507 | return -ENOMEM; | |
508 | break; | |
509 | ||
510 | case OPT_WORKDIR: | |
511 | kfree(config->workdir); | |
512 | config->workdir = match_strdup(&args[0]); | |
513 | if (!config->workdir) | |
514 | return -ENOMEM; | |
515 | break; | |
516 | ||
517 | default: | |
518 | return -EINVAL; | |
519 | } | |
520 | } | |
521 | return 0; | |
522 | } | |
523 | ||
524 | #define OVL_WORKDIR_NAME "work" | |
525 | ||
526 | static struct dentry *ovl_workdir_create(struct vfsmount *mnt, | |
527 | struct dentry *dentry) | |
528 | { | |
529 | struct inode *dir = dentry->d_inode; | |
530 | struct dentry *work; | |
531 | int err; | |
532 | bool retried = false; | |
533 | ||
534 | err = mnt_want_write(mnt); | |
535 | if (err) | |
536 | return ERR_PTR(err); | |
537 | ||
538 | mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT); | |
539 | retry: | |
540 | work = lookup_one_len(OVL_WORKDIR_NAME, dentry, | |
541 | strlen(OVL_WORKDIR_NAME)); | |
542 | ||
543 | if (!IS_ERR(work)) { | |
544 | struct kstat stat = { | |
545 | .mode = S_IFDIR | 0, | |
546 | }; | |
547 | ||
548 | if (work->d_inode) { | |
549 | err = -EEXIST; | |
550 | if (retried) | |
551 | goto out_dput; | |
552 | ||
553 | retried = true; | |
554 | ovl_cleanup(dir, work); | |
555 | dput(work); | |
556 | goto retry; | |
557 | } | |
558 | ||
559 | err = ovl_create_real(dir, work, &stat, NULL, NULL, true); | |
560 | if (err) | |
561 | goto out_dput; | |
562 | } | |
563 | out_unlock: | |
564 | mutex_unlock(&dir->i_mutex); | |
565 | mnt_drop_write(mnt); | |
566 | ||
567 | return work; | |
568 | ||
569 | out_dput: | |
570 | dput(work); | |
571 | work = ERR_PTR(err); | |
572 | goto out_unlock; | |
573 | } | |
574 | ||
91c77947 MS |
575 | static void ovl_unescape(char *s) |
576 | { | |
577 | char *d = s; | |
578 | ||
579 | for (;; s++, d++) { | |
580 | if (*s == '\\') | |
581 | s++; | |
582 | *d = *s; | |
583 | if (!*s) | |
584 | break; | |
585 | } | |
586 | } | |
587 | ||
e9be9d5e MS |
588 | static int ovl_mount_dir(const char *name, struct path *path) |
589 | { | |
590 | int err; | |
91c77947 MS |
591 | char *tmp = kstrdup(name, GFP_KERNEL); |
592 | ||
593 | if (!tmp) | |
594 | return -ENOMEM; | |
e9be9d5e | 595 | |
91c77947 MS |
596 | ovl_unescape(tmp); |
597 | err = kern_path(tmp, LOOKUP_FOLLOW, path); | |
e9be9d5e | 598 | if (err) { |
91c77947 | 599 | pr_err("overlayfs: failed to resolve '%s': %i\n", tmp, err); |
e9be9d5e MS |
600 | err = -EINVAL; |
601 | } | |
91c77947 | 602 | kfree(tmp); |
e9be9d5e MS |
603 | return err; |
604 | } | |
605 | ||
606 | static bool ovl_is_allowed_fs_type(struct dentry *root) | |
607 | { | |
608 | const struct dentry_operations *dop = root->d_op; | |
609 | ||
610 | /* | |
611 | * We don't support: | |
612 | * - automount filesystems | |
613 | * - filesystems with revalidate (FIXME for lower layer) | |
614 | * - filesystems with case insensitive names | |
615 | */ | |
616 | if (dop && | |
617 | (dop->d_manage || dop->d_automount || | |
618 | dop->d_revalidate || dop->d_weak_revalidate || | |
619 | dop->d_compare || dop->d_hash)) { | |
620 | return false; | |
621 | } | |
622 | return true; | |
623 | } | |
624 | ||
625 | /* Workdir should not be subdir of upperdir and vice versa */ | |
626 | static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) | |
627 | { | |
628 | bool ok = false; | |
629 | ||
630 | if (workdir != upperdir) { | |
631 | ok = (lock_rename(workdir, upperdir) == NULL); | |
632 | unlock_rename(workdir, upperdir); | |
633 | } | |
634 | return ok; | |
635 | } | |
636 | ||
637 | static int ovl_fill_super(struct super_block *sb, void *data, int silent) | |
638 | { | |
639 | struct path lowerpath; | |
640 | struct path upperpath; | |
641 | struct path workpath; | |
642 | struct inode *root_inode; | |
643 | struct dentry *root_dentry; | |
644 | struct ovl_entry *oe; | |
645 | struct ovl_fs *ufs; | |
cc259639 | 646 | struct kstatfs statfs; |
e9be9d5e MS |
647 | int err; |
648 | ||
f45827e8 EZ |
649 | err = -ENOMEM; |
650 | ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL); | |
651 | if (!ufs) | |
e9be9d5e MS |
652 | goto out; |
653 | ||
f45827e8 EZ |
654 | err = ovl_parse_opt((char *) data, &ufs->config); |
655 | if (err) | |
656 | goto out_free_config; | |
657 | ||
e9be9d5e MS |
658 | /* FIXME: workdir is not needed for a R/O mount */ |
659 | err = -EINVAL; | |
f45827e8 EZ |
660 | if (!ufs->config.upperdir || !ufs->config.lowerdir || |
661 | !ufs->config.workdir) { | |
e9be9d5e MS |
662 | pr_err("overlayfs: missing upperdir or lowerdir or workdir\n"); |
663 | goto out_free_config; | |
664 | } | |
665 | ||
666 | err = -ENOMEM; | |
e9be9d5e MS |
667 | oe = ovl_alloc_entry(); |
668 | if (oe == NULL) | |
f45827e8 | 669 | goto out_free_config; |
e9be9d5e | 670 | |
f45827e8 | 671 | err = ovl_mount_dir(ufs->config.upperdir, &upperpath); |
e9be9d5e MS |
672 | if (err) |
673 | goto out_free_oe; | |
674 | ||
f45827e8 | 675 | err = ovl_mount_dir(ufs->config.lowerdir, &lowerpath); |
e9be9d5e MS |
676 | if (err) |
677 | goto out_put_upperpath; | |
678 | ||
f45827e8 | 679 | err = ovl_mount_dir(ufs->config.workdir, &workpath); |
e9be9d5e MS |
680 | if (err) |
681 | goto out_put_lowerpath; | |
682 | ||
683 | err = -EINVAL; | |
684 | if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) || | |
685 | !S_ISDIR(lowerpath.dentry->d_inode->i_mode) || | |
686 | !S_ISDIR(workpath.dentry->d_inode->i_mode)) { | |
687 | pr_err("overlayfs: upperdir or lowerdir or workdir not a directory\n"); | |
688 | goto out_put_workpath; | |
689 | } | |
690 | ||
691 | if (upperpath.mnt != workpath.mnt) { | |
692 | pr_err("overlayfs: workdir and upperdir must reside under the same mount\n"); | |
693 | goto out_put_workpath; | |
694 | } | |
695 | if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) { | |
696 | pr_err("overlayfs: workdir and upperdir must be separate subtrees\n"); | |
697 | goto out_put_workpath; | |
698 | } | |
699 | ||
700 | if (!ovl_is_allowed_fs_type(upperpath.dentry)) { | |
701 | pr_err("overlayfs: filesystem of upperdir is not supported\n"); | |
702 | goto out_put_workpath; | |
703 | } | |
704 | ||
705 | if (!ovl_is_allowed_fs_type(lowerpath.dentry)) { | |
706 | pr_err("overlayfs: filesystem of lowerdir is not supported\n"); | |
707 | goto out_put_workpath; | |
708 | } | |
709 | ||
cc259639 AW |
710 | err = vfs_statfs(&lowerpath, &statfs); |
711 | if (err) { | |
712 | pr_err("overlayfs: statfs failed on lowerpath\n"); | |
713 | goto out_put_workpath; | |
714 | } | |
715 | ufs->lower_namelen = statfs.f_namelen; | |
716 | ||
69c433ed MS |
717 | sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth, |
718 | lowerpath.mnt->mnt_sb->s_stack_depth) + 1; | |
719 | ||
720 | err = -EINVAL; | |
721 | if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { | |
722 | pr_err("overlayfs: maximum fs stacking depth exceeded\n"); | |
723 | goto out_put_workpath; | |
724 | } | |
725 | ||
e9be9d5e MS |
726 | ufs->upper_mnt = clone_private_mount(&upperpath); |
727 | err = PTR_ERR(ufs->upper_mnt); | |
728 | if (IS_ERR(ufs->upper_mnt)) { | |
729 | pr_err("overlayfs: failed to clone upperpath\n"); | |
730 | goto out_put_workpath; | |
731 | } | |
732 | ||
733 | ufs->lower_mnt = clone_private_mount(&lowerpath); | |
734 | err = PTR_ERR(ufs->lower_mnt); | |
735 | if (IS_ERR(ufs->lower_mnt)) { | |
736 | pr_err("overlayfs: failed to clone lowerpath\n"); | |
737 | goto out_put_upper_mnt; | |
738 | } | |
739 | ||
740 | ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry); | |
741 | err = PTR_ERR(ufs->workdir); | |
742 | if (IS_ERR(ufs->workdir)) { | |
743 | pr_err("overlayfs: failed to create directory %s/%s\n", | |
f45827e8 | 744 | ufs->config.workdir, OVL_WORKDIR_NAME); |
e9be9d5e MS |
745 | goto out_put_lower_mnt; |
746 | } | |
747 | ||
748 | /* | |
749 | * Make lower_mnt R/O. That way fchmod/fchown on lower file | |
750 | * will fail instead of modifying lower fs. | |
751 | */ | |
752 | ufs->lower_mnt->mnt_flags |= MNT_READONLY; | |
753 | ||
754 | /* If the upper fs is r/o, we mark overlayfs r/o too */ | |
755 | if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY) | |
756 | sb->s_flags |= MS_RDONLY; | |
757 | ||
758 | sb->s_d_op = &ovl_dentry_operations; | |
759 | ||
760 | err = -ENOMEM; | |
761 | root_inode = ovl_new_inode(sb, S_IFDIR, oe); | |
762 | if (!root_inode) | |
763 | goto out_put_workdir; | |
764 | ||
765 | root_dentry = d_make_root(root_inode); | |
766 | if (!root_dentry) | |
767 | goto out_put_workdir; | |
768 | ||
769 | mntput(upperpath.mnt); | |
770 | mntput(lowerpath.mnt); | |
771 | path_put(&workpath); | |
772 | ||
773 | oe->__upperdentry = upperpath.dentry; | |
774 | oe->lowerdentry = lowerpath.dentry; | |
775 | ||
776 | root_dentry->d_fsdata = oe; | |
777 | ||
cc259639 | 778 | sb->s_magic = OVERLAYFS_SUPER_MAGIC; |
e9be9d5e MS |
779 | sb->s_op = &ovl_super_operations; |
780 | sb->s_root = root_dentry; | |
781 | sb->s_fs_info = ufs; | |
782 | ||
783 | return 0; | |
784 | ||
785 | out_put_workdir: | |
786 | dput(ufs->workdir); | |
787 | out_put_lower_mnt: | |
788 | mntput(ufs->lower_mnt); | |
789 | out_put_upper_mnt: | |
790 | mntput(ufs->upper_mnt); | |
791 | out_put_workpath: | |
792 | path_put(&workpath); | |
793 | out_put_lowerpath: | |
794 | path_put(&lowerpath); | |
795 | out_put_upperpath: | |
796 | path_put(&upperpath); | |
797 | out_free_oe: | |
798 | kfree(oe); | |
e9be9d5e | 799 | out_free_config: |
f45827e8 EZ |
800 | kfree(ufs->config.lowerdir); |
801 | kfree(ufs->config.upperdir); | |
802 | kfree(ufs->config.workdir); | |
803 | kfree(ufs); | |
e9be9d5e MS |
804 | out: |
805 | return err; | |
806 | } | |
807 | ||
808 | static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags, | |
809 | const char *dev_name, void *raw_data) | |
810 | { | |
811 | return mount_nodev(fs_type, flags, raw_data, ovl_fill_super); | |
812 | } | |
813 | ||
814 | static struct file_system_type ovl_fs_type = { | |
815 | .owner = THIS_MODULE, | |
ef94b186 | 816 | .name = "overlay", |
e9be9d5e MS |
817 | .mount = ovl_mount, |
818 | .kill_sb = kill_anon_super, | |
819 | }; | |
ef94b186 | 820 | MODULE_ALIAS_FS("overlay"); |
e9be9d5e MS |
821 | |
822 | static int __init ovl_init(void) | |
823 | { | |
824 | return register_filesystem(&ovl_fs_type); | |
825 | } | |
826 | ||
827 | static void __exit ovl_exit(void) | |
828 | { | |
829 | unregister_filesystem(&ovl_fs_type); | |
830 | } | |
831 | ||
832 | module_init(ovl_init); | |
833 | module_exit(ovl_exit); |