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