blob: 08b704cebfc4f8819944e09b05f5f7de35659b92 [file] [log] [blame]
Miklos Szeredie9be9d52014-10-24 00:14:38 +02001/*
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>
Andy Whitcroftcc259632014-10-24 00:14:38 +020019#include <linux/statfs.h>
Erez Zadokf45827e82014-10-24 00:14:38 +020020#include <linux/seq_file.h>
Miklos Szeredie9be9d52014-10-24 00:14:38 +020021#include "overlayfs.h"
22
23MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
24MODULE_DESCRIPTION("Overlay filesystem");
25MODULE_LICENSE("GPL");
26
Andy Whitcroftcc259632014-10-24 00:14:38 +020027#define OVERLAYFS_SUPER_MAGIC 0x794c764f
28
Erez Zadokf45827e82014-10-24 00:14:38 +020029struct ovl_config {
30 char *lowerdir;
31 char *upperdir;
32 char *workdir;
33};
34
Miklos Szeredie9be9d52014-10-24 00:14:38 +020035/* private information held for overlayfs's superblock */
36struct ovl_fs {
37 struct vfsmount *upper_mnt;
38 struct vfsmount *lower_mnt;
39 struct dentry *workdir;
Andy Whitcroftcc259632014-10-24 00:14:38 +020040 long lower_namelen;
Erez Zadokf45827e82014-10-24 00:14:38 +020041 /* pathnames of lower and upper dirs, for show_options */
42 struct ovl_config config;
Miklos Szeredie9be9d52014-10-24 00:14:38 +020043};
44
45struct ovl_dir_cache;
46
47/* private information held for every overlayfs dentry */
48struct 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
61const char *ovl_opaque_xattr = "trusted.overlay.opaque";
62
63
64enum 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
85static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
86{
87 struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
88 /*
89 * Make sure to order reads to upperdentry wrt ovl_dentry_update()
90 */
91 smp_read_barrier_depends();
92 return upperdentry;
93}
94
95void ovl_path_upper(struct dentry *dentry, struct path *path)
96{
97 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
98 struct ovl_entry *oe = dentry->d_fsdata;
99
100 path->mnt = ofs->upper_mnt;
101 path->dentry = ovl_upperdentry_dereference(oe);
102}
103
104enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
105{
106
107 enum ovl_path_type type = ovl_path_type(dentry);
108
109 if (type == OVL_PATH_LOWER)
110 ovl_path_lower(dentry, path);
111 else
112 ovl_path_upper(dentry, path);
113
114 return type;
115}
116
117struct dentry *ovl_dentry_upper(struct dentry *dentry)
118{
119 struct ovl_entry *oe = dentry->d_fsdata;
120
121 return ovl_upperdentry_dereference(oe);
122}
123
124struct dentry *ovl_dentry_lower(struct dentry *dentry)
125{
126 struct ovl_entry *oe = dentry->d_fsdata;
127
128 return oe->lowerdentry;
129}
130
131struct dentry *ovl_dentry_real(struct dentry *dentry)
132{
133 struct ovl_entry *oe = dentry->d_fsdata;
134 struct dentry *realdentry;
135
136 realdentry = ovl_upperdentry_dereference(oe);
137 if (!realdentry)
138 realdentry = oe->lowerdentry;
139
140 return realdentry;
141}
142
143struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
144{
145 struct dentry *realdentry;
146
147 realdentry = ovl_upperdentry_dereference(oe);
148 if (realdentry) {
149 *is_upper = true;
150 } else {
151 realdentry = oe->lowerdentry;
152 *is_upper = false;
153 }
154 return realdentry;
155}
156
157struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
158{
159 struct ovl_entry *oe = dentry->d_fsdata;
160
161 return oe->cache;
162}
163
164void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
165{
166 struct ovl_entry *oe = dentry->d_fsdata;
167
168 oe->cache = cache;
169}
170
171void ovl_path_lower(struct dentry *dentry, struct path *path)
172{
173 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
174 struct ovl_entry *oe = dentry->d_fsdata;
175
176 path->mnt = ofs->lower_mnt;
177 path->dentry = oe->lowerdentry;
178}
179
180int ovl_want_write(struct dentry *dentry)
181{
182 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
183 return mnt_want_write(ofs->upper_mnt);
184}
185
186void ovl_drop_write(struct dentry *dentry)
187{
188 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
189 mnt_drop_write(ofs->upper_mnt);
190}
191
192struct dentry *ovl_workdir(struct dentry *dentry)
193{
194 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
195 return ofs->workdir;
196}
197
198bool ovl_dentry_is_opaque(struct dentry *dentry)
199{
200 struct ovl_entry *oe = dentry->d_fsdata;
201 return oe->opaque;
202}
203
204void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
205{
206 struct ovl_entry *oe = dentry->d_fsdata;
207 oe->opaque = opaque;
208}
209
210void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
211{
212 struct ovl_entry *oe = dentry->d_fsdata;
213
214 WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
215 WARN_ON(oe->__upperdentry);
216 BUG_ON(!upperdentry->d_inode);
217 /*
218 * Make sure upperdentry is consistent before making it visible to
219 * ovl_upperdentry_dereference().
220 */
221 smp_wmb();
222 oe->__upperdentry = upperdentry;
223}
224
225void ovl_dentry_version_inc(struct dentry *dentry)
226{
227 struct ovl_entry *oe = dentry->d_fsdata;
228
229 WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
230 oe->version++;
231}
232
233u64 ovl_dentry_version_get(struct dentry *dentry)
234{
235 struct ovl_entry *oe = dentry->d_fsdata;
236
237 WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
238 return oe->version;
239}
240
241bool ovl_is_whiteout(struct dentry *dentry)
242{
243 struct inode *inode = dentry->d_inode;
244
245 return inode && IS_WHITEOUT(inode);
246}
247
248static bool ovl_is_opaquedir(struct dentry *dentry)
249{
250 int res;
251 char val;
252 struct inode *inode = dentry->d_inode;
253
254 if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
255 return false;
256
257 res = inode->i_op->getxattr(dentry, ovl_opaque_xattr, &val, 1);
258 if (res == 1 && val == 'y')
259 return true;
260
261 return false;
262}
263
264static void ovl_dentry_release(struct dentry *dentry)
265{
266 struct ovl_entry *oe = dentry->d_fsdata;
267
268 if (oe) {
269 dput(oe->__upperdentry);
270 dput(oe->lowerdentry);
271 kfree_rcu(oe, rcu);
272 }
273}
274
275static const struct dentry_operations ovl_dentry_operations = {
276 .d_release = ovl_dentry_release,
277};
278
279static struct ovl_entry *ovl_alloc_entry(void)
280{
281 return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
282}
283
284static inline struct dentry *ovl_lookup_real(struct dentry *dir,
285 struct qstr *name)
286{
287 struct dentry *dentry;
288
289 mutex_lock(&dir->d_inode->i_mutex);
290 dentry = lookup_one_len(name->name, dir, name->len);
291 mutex_unlock(&dir->d_inode->i_mutex);
292
293 if (IS_ERR(dentry)) {
294 if (PTR_ERR(dentry) == -ENOENT)
295 dentry = NULL;
296 } else if (!dentry->d_inode) {
297 dput(dentry);
298 dentry = NULL;
299 }
300 return dentry;
301}
302
303struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
304 unsigned int flags)
305{
306 struct ovl_entry *oe;
307 struct dentry *upperdir;
308 struct dentry *lowerdir;
309 struct dentry *upperdentry = NULL;
310 struct dentry *lowerdentry = NULL;
311 struct inode *inode = NULL;
312 int err;
313
314 err = -ENOMEM;
315 oe = ovl_alloc_entry();
316 if (!oe)
317 goto out;
318
319 upperdir = ovl_dentry_upper(dentry->d_parent);
320 lowerdir = ovl_dentry_lower(dentry->d_parent);
321
322 if (upperdir) {
323 upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
324 err = PTR_ERR(upperdentry);
325 if (IS_ERR(upperdentry))
326 goto out_put_dir;
327
328 if (lowerdir && upperdentry) {
329 if (ovl_is_whiteout(upperdentry)) {
330 dput(upperdentry);
331 upperdentry = NULL;
332 oe->opaque = true;
333 } else if (ovl_is_opaquedir(upperdentry)) {
334 oe->opaque = true;
335 }
336 }
337 }
338 if (lowerdir && !oe->opaque) {
339 lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
340 err = PTR_ERR(lowerdentry);
341 if (IS_ERR(lowerdentry))
342 goto out_dput_upper;
343 }
344
345 if (lowerdentry && upperdentry &&
346 (!S_ISDIR(upperdentry->d_inode->i_mode) ||
347 !S_ISDIR(lowerdentry->d_inode->i_mode))) {
348 dput(lowerdentry);
349 lowerdentry = NULL;
350 oe->opaque = true;
351 }
352
353 if (lowerdentry || upperdentry) {
354 struct dentry *realdentry;
355
356 realdentry = upperdentry ? upperdentry : lowerdentry;
357 err = -ENOMEM;
358 inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
359 oe);
360 if (!inode)
361 goto out_dput;
362 ovl_copyattr(realdentry->d_inode, inode);
363 }
364
365 oe->__upperdentry = upperdentry;
366 oe->lowerdentry = lowerdentry;
367
368 dentry->d_fsdata = oe;
369 d_add(dentry, inode);
370
371 return NULL;
372
373out_dput:
374 dput(lowerdentry);
375out_dput_upper:
376 dput(upperdentry);
377out_put_dir:
378 kfree(oe);
379out:
380 return ERR_PTR(err);
381}
382
383struct file *ovl_path_open(struct path *path, int flags)
384{
385 return dentry_open(path, flags, current_cred());
386}
387
388static void ovl_put_super(struct super_block *sb)
389{
390 struct ovl_fs *ufs = sb->s_fs_info;
391
392 dput(ufs->workdir);
393 mntput(ufs->upper_mnt);
394 mntput(ufs->lower_mnt);
395
Erez Zadokf45827e82014-10-24 00:14:38 +0200396 kfree(ufs->config.lowerdir);
397 kfree(ufs->config.upperdir);
398 kfree(ufs->config.workdir);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200399 kfree(ufs);
400}
401
Andy Whitcroftcc259632014-10-24 00:14:38 +0200402/**
403 * ovl_statfs
404 * @sb: The overlayfs super block
405 * @buf: The struct kstatfs to fill in with stats
406 *
407 * Get the filesystem statistics. As writes always target the upper layer
408 * filesystem pass the statfs to the same filesystem.
409 */
410static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
411{
412 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
413 struct dentry *root_dentry = dentry->d_sb->s_root;
414 struct path path;
415 int err;
416
417 ovl_path_upper(root_dentry, &path);
418
419 err = vfs_statfs(&path, buf);
420 if (!err) {
421 buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
422 buf->f_type = OVERLAYFS_SUPER_MAGIC;
423 }
424
425 return err;
426}
427
Erez Zadokf45827e82014-10-24 00:14:38 +0200428/**
429 * ovl_show_options
430 *
431 * Prints the mount options for a given superblock.
432 * Returns zero; does not fail.
433 */
434static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
435{
436 struct super_block *sb = dentry->d_sb;
437 struct ovl_fs *ufs = sb->s_fs_info;
438
439 seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
440 seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
441 seq_printf(m, ",workdir=%s", ufs->config.workdir);
442 return 0;
443}
444
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200445static const struct super_operations ovl_super_operations = {
446 .put_super = ovl_put_super,
Andy Whitcroftcc259632014-10-24 00:14:38 +0200447 .statfs = ovl_statfs,
Erez Zadokf45827e82014-10-24 00:14:38 +0200448 .show_options = ovl_show_options,
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200449};
450
451enum {
452 OPT_LOWERDIR,
453 OPT_UPPERDIR,
454 OPT_WORKDIR,
455 OPT_ERR,
456};
457
458static const match_table_t ovl_tokens = {
459 {OPT_LOWERDIR, "lowerdir=%s"},
460 {OPT_UPPERDIR, "upperdir=%s"},
461 {OPT_WORKDIR, "workdir=%s"},
462 {OPT_ERR, NULL}
463};
464
465static int ovl_parse_opt(char *opt, struct ovl_config *config)
466{
467 char *p;
468
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200469 while ((p = strsep(&opt, ",")) != NULL) {
470 int token;
471 substring_t args[MAX_OPT_ARGS];
472
473 if (!*p)
474 continue;
475
476 token = match_token(p, ovl_tokens, args);
477 switch (token) {
478 case OPT_UPPERDIR:
479 kfree(config->upperdir);
480 config->upperdir = match_strdup(&args[0]);
481 if (!config->upperdir)
482 return -ENOMEM;
483 break;
484
485 case OPT_LOWERDIR:
486 kfree(config->lowerdir);
487 config->lowerdir = match_strdup(&args[0]);
488 if (!config->lowerdir)
489 return -ENOMEM;
490 break;
491
492 case OPT_WORKDIR:
493 kfree(config->workdir);
494 config->workdir = match_strdup(&args[0]);
495 if (!config->workdir)
496 return -ENOMEM;
497 break;
498
499 default:
500 return -EINVAL;
501 }
502 }
503 return 0;
504}
505
506#define OVL_WORKDIR_NAME "work"
507
508static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
509 struct dentry *dentry)
510{
511 struct inode *dir = dentry->d_inode;
512 struct dentry *work;
513 int err;
514 bool retried = false;
515
516 err = mnt_want_write(mnt);
517 if (err)
518 return ERR_PTR(err);
519
520 mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
521retry:
522 work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
523 strlen(OVL_WORKDIR_NAME));
524
525 if (!IS_ERR(work)) {
526 struct kstat stat = {
527 .mode = S_IFDIR | 0,
528 };
529
530 if (work->d_inode) {
531 err = -EEXIST;
532 if (retried)
533 goto out_dput;
534
535 retried = true;
536 ovl_cleanup(dir, work);
537 dput(work);
538 goto retry;
539 }
540
541 err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
542 if (err)
543 goto out_dput;
544 }
545out_unlock:
546 mutex_unlock(&dir->i_mutex);
547 mnt_drop_write(mnt);
548
549 return work;
550
551out_dput:
552 dput(work);
553 work = ERR_PTR(err);
554 goto out_unlock;
555}
556
557static int ovl_mount_dir(const char *name, struct path *path)
558{
559 int err;
560
561 err = kern_path(name, LOOKUP_FOLLOW, path);
562 if (err) {
563 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
564 err = -EINVAL;
565 }
566 return err;
567}
568
569static bool ovl_is_allowed_fs_type(struct dentry *root)
570{
571 const struct dentry_operations *dop = root->d_op;
572
573 /*
574 * We don't support:
575 * - automount filesystems
576 * - filesystems with revalidate (FIXME for lower layer)
577 * - filesystems with case insensitive names
578 */
579 if (dop &&
580 (dop->d_manage || dop->d_automount ||
581 dop->d_revalidate || dop->d_weak_revalidate ||
582 dop->d_compare || dop->d_hash)) {
583 return false;
584 }
585 return true;
586}
587
588/* Workdir should not be subdir of upperdir and vice versa */
589static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
590{
591 bool ok = false;
592
593 if (workdir != upperdir) {
594 ok = (lock_rename(workdir, upperdir) == NULL);
595 unlock_rename(workdir, upperdir);
596 }
597 return ok;
598}
599
600static int ovl_fill_super(struct super_block *sb, void *data, int silent)
601{
602 struct path lowerpath;
603 struct path upperpath;
604 struct path workpath;
605 struct inode *root_inode;
606 struct dentry *root_dentry;
607 struct ovl_entry *oe;
608 struct ovl_fs *ufs;
Andy Whitcroftcc259632014-10-24 00:14:38 +0200609 struct kstatfs statfs;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200610 int err;
611
Erez Zadokf45827e82014-10-24 00:14:38 +0200612 err = -ENOMEM;
613 ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
614 if (!ufs)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200615 goto out;
616
Erez Zadokf45827e82014-10-24 00:14:38 +0200617 err = ovl_parse_opt((char *) data, &ufs->config);
618 if (err)
619 goto out_free_config;
620
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200621 /* FIXME: workdir is not needed for a R/O mount */
622 err = -EINVAL;
Erez Zadokf45827e82014-10-24 00:14:38 +0200623 if (!ufs->config.upperdir || !ufs->config.lowerdir ||
624 !ufs->config.workdir) {
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200625 pr_err("overlayfs: missing upperdir or lowerdir or workdir\n");
626 goto out_free_config;
627 }
628
629 err = -ENOMEM;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200630 oe = ovl_alloc_entry();
631 if (oe == NULL)
Erez Zadokf45827e82014-10-24 00:14:38 +0200632 goto out_free_config;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200633
Erez Zadokf45827e82014-10-24 00:14:38 +0200634 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200635 if (err)
636 goto out_free_oe;
637
Erez Zadokf45827e82014-10-24 00:14:38 +0200638 err = ovl_mount_dir(ufs->config.lowerdir, &lowerpath);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200639 if (err)
640 goto out_put_upperpath;
641
Erez Zadokf45827e82014-10-24 00:14:38 +0200642 err = ovl_mount_dir(ufs->config.workdir, &workpath);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200643 if (err)
644 goto out_put_lowerpath;
645
646 err = -EINVAL;
647 if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
648 !S_ISDIR(lowerpath.dentry->d_inode->i_mode) ||
649 !S_ISDIR(workpath.dentry->d_inode->i_mode)) {
650 pr_err("overlayfs: upperdir or lowerdir or workdir not a directory\n");
651 goto out_put_workpath;
652 }
653
654 if (upperpath.mnt != workpath.mnt) {
655 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
656 goto out_put_workpath;
657 }
658 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
659 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
660 goto out_put_workpath;
661 }
662
663 if (!ovl_is_allowed_fs_type(upperpath.dentry)) {
664 pr_err("overlayfs: filesystem of upperdir is not supported\n");
665 goto out_put_workpath;
666 }
667
668 if (!ovl_is_allowed_fs_type(lowerpath.dentry)) {
669 pr_err("overlayfs: filesystem of lowerdir is not supported\n");
670 goto out_put_workpath;
671 }
672
Andy Whitcroftcc259632014-10-24 00:14:38 +0200673 err = vfs_statfs(&lowerpath, &statfs);
674 if (err) {
675 pr_err("overlayfs: statfs failed on lowerpath\n");
676 goto out_put_workpath;
677 }
678 ufs->lower_namelen = statfs.f_namelen;
679
Miklos Szeredi69c433e2014-10-24 00:14:39 +0200680 sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth,
681 lowerpath.mnt->mnt_sb->s_stack_depth) + 1;
682
683 err = -EINVAL;
684 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
685 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
686 goto out_put_workpath;
687 }
688
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200689 ufs->upper_mnt = clone_private_mount(&upperpath);
690 err = PTR_ERR(ufs->upper_mnt);
691 if (IS_ERR(ufs->upper_mnt)) {
692 pr_err("overlayfs: failed to clone upperpath\n");
693 goto out_put_workpath;
694 }
695
696 ufs->lower_mnt = clone_private_mount(&lowerpath);
697 err = PTR_ERR(ufs->lower_mnt);
698 if (IS_ERR(ufs->lower_mnt)) {
699 pr_err("overlayfs: failed to clone lowerpath\n");
700 goto out_put_upper_mnt;
701 }
702
703 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
704 err = PTR_ERR(ufs->workdir);
705 if (IS_ERR(ufs->workdir)) {
706 pr_err("overlayfs: failed to create directory %s/%s\n",
Erez Zadokf45827e82014-10-24 00:14:38 +0200707 ufs->config.workdir, OVL_WORKDIR_NAME);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200708 goto out_put_lower_mnt;
709 }
710
711 /*
712 * Make lower_mnt R/O. That way fchmod/fchown on lower file
713 * will fail instead of modifying lower fs.
714 */
715 ufs->lower_mnt->mnt_flags |= MNT_READONLY;
716
717 /* If the upper fs is r/o, we mark overlayfs r/o too */
718 if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)
719 sb->s_flags |= MS_RDONLY;
720
721 sb->s_d_op = &ovl_dentry_operations;
722
723 err = -ENOMEM;
724 root_inode = ovl_new_inode(sb, S_IFDIR, oe);
725 if (!root_inode)
726 goto out_put_workdir;
727
728 root_dentry = d_make_root(root_inode);
729 if (!root_dentry)
730 goto out_put_workdir;
731
732 mntput(upperpath.mnt);
733 mntput(lowerpath.mnt);
734 path_put(&workpath);
735
736 oe->__upperdentry = upperpath.dentry;
737 oe->lowerdentry = lowerpath.dentry;
738
739 root_dentry->d_fsdata = oe;
740
Andy Whitcroftcc259632014-10-24 00:14:38 +0200741 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200742 sb->s_op = &ovl_super_operations;
743 sb->s_root = root_dentry;
744 sb->s_fs_info = ufs;
745
746 return 0;
747
748out_put_workdir:
749 dput(ufs->workdir);
750out_put_lower_mnt:
751 mntput(ufs->lower_mnt);
752out_put_upper_mnt:
753 mntput(ufs->upper_mnt);
754out_put_workpath:
755 path_put(&workpath);
756out_put_lowerpath:
757 path_put(&lowerpath);
758out_put_upperpath:
759 path_put(&upperpath);
760out_free_oe:
761 kfree(oe);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200762out_free_config:
Erez Zadokf45827e82014-10-24 00:14:38 +0200763 kfree(ufs->config.lowerdir);
764 kfree(ufs->config.upperdir);
765 kfree(ufs->config.workdir);
766 kfree(ufs);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200767out:
768 return err;
769}
770
771static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
772 const char *dev_name, void *raw_data)
773{
774 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
775}
776
777static struct file_system_type ovl_fs_type = {
778 .owner = THIS_MODULE,
779 .name = "overlayfs",
780 .mount = ovl_mount,
781 .kill_sb = kill_anon_super,
782};
783MODULE_ALIAS_FS("overlayfs");
784
785static int __init ovl_init(void)
786{
787 return register_filesystem(&ovl_fs_type);
788}
789
790static void __exit ovl_exit(void)
791{
792 unregister_filesystem(&ovl_fs_type);
793}
794
795module_init(ovl_init);
796module_exit(ovl_exit);