3 * Copyright (C) 2011 Novell Inc.
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.
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 <linux/statfs.h>
20 #include <linux/seq_file.h>
21 #include "overlayfs.h"
23 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
24 MODULE_DESCRIPTION("Overlay filesystem");
25 MODULE_LICENSE("GPL");
27 #define OVERLAYFS_SUPER_MAGIC 0x794c7630
35 /* private information held for overlayfs's superblock */
37 struct vfsmount *upper_mnt;
39 struct vfsmount **lower_mnt;
40 struct dentry *workdir;
42 /* pathnames of lower and upper dirs, for show_options */
43 struct ovl_config config;
48 /* private information held for every overlayfs dentry */
50 struct dentry *__upperdentry;
51 struct ovl_dir_cache *cache;
60 struct path lowerstack[];
63 #define OVL_MAX_STACK 500
65 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
67 return oe->numlower ? oe->lowerstack[0].dentry : NULL;
70 enum ovl_path_type ovl_path_type(struct dentry *dentry)
72 struct ovl_entry *oe = dentry->d_fsdata;
73 enum ovl_path_type type = 0;
75 if (oe->__upperdentry) {
76 type = __OVL_PATH_UPPER;
79 if (S_ISDIR(dentry->d_inode->i_mode))
80 type |= __OVL_PATH_MERGE;
81 } else if (!oe->opaque) {
82 type |= __OVL_PATH_PURE;
86 type |= __OVL_PATH_MERGE;
91 static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
93 return lockless_dereference(oe->__upperdentry);
96 void ovl_path_upper(struct dentry *dentry, struct path *path)
98 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
99 struct ovl_entry *oe = dentry->d_fsdata;
101 path->mnt = ofs->upper_mnt;
102 path->dentry = ovl_upperdentry_dereference(oe);
105 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
107 enum ovl_path_type type = ovl_path_type(dentry);
109 if (!OVL_TYPE_UPPER(type))
110 ovl_path_lower(dentry, path);
112 ovl_path_upper(dentry, path);
117 struct dentry *ovl_dentry_upper(struct dentry *dentry)
119 struct ovl_entry *oe = dentry->d_fsdata;
121 return ovl_upperdentry_dereference(oe);
124 struct dentry *ovl_dentry_lower(struct dentry *dentry)
126 struct ovl_entry *oe = dentry->d_fsdata;
128 return __ovl_dentry_lower(oe);
131 struct dentry *ovl_dentry_real(struct dentry *dentry)
133 struct ovl_entry *oe = dentry->d_fsdata;
134 struct dentry *realdentry;
136 realdentry = ovl_upperdentry_dereference(oe);
138 realdentry = __ovl_dentry_lower(oe);
143 struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
145 struct dentry *realdentry;
147 realdentry = ovl_upperdentry_dereference(oe);
151 realdentry = __ovl_dentry_lower(oe);
157 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
159 struct ovl_entry *oe = dentry->d_fsdata;
164 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
166 struct ovl_entry *oe = dentry->d_fsdata;
171 void ovl_path_lower(struct dentry *dentry, struct path *path)
173 struct ovl_entry *oe = dentry->d_fsdata;
175 *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
178 int ovl_want_write(struct dentry *dentry)
180 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
181 return mnt_want_write(ofs->upper_mnt);
184 void ovl_drop_write(struct dentry *dentry)
186 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
187 mnt_drop_write(ofs->upper_mnt);
190 struct dentry *ovl_workdir(struct dentry *dentry)
192 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
196 bool ovl_dentry_is_opaque(struct dentry *dentry)
198 struct ovl_entry *oe = dentry->d_fsdata;
202 void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
204 struct ovl_entry *oe = dentry->d_fsdata;
208 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
210 struct ovl_entry *oe = dentry->d_fsdata;
212 WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
213 WARN_ON(oe->__upperdentry);
214 BUG_ON(!upperdentry->d_inode);
216 * Make sure upperdentry is consistent before making it visible to
217 * ovl_upperdentry_dereference().
220 oe->__upperdentry = upperdentry;
223 void ovl_dentry_version_inc(struct dentry *dentry)
225 struct ovl_entry *oe = dentry->d_fsdata;
227 WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
231 u64 ovl_dentry_version_get(struct dentry *dentry)
233 struct ovl_entry *oe = dentry->d_fsdata;
235 WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
239 bool ovl_is_whiteout(struct dentry *dentry)
241 struct inode *inode = dentry->d_inode;
243 return inode && IS_WHITEOUT(inode);
246 static bool ovl_is_opaquedir(struct dentry *dentry)
250 struct inode *inode = dentry->d_inode;
252 if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
255 res = inode->i_op->getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
256 if (res == 1 && val == 'y')
262 static void ovl_dentry_release(struct dentry *dentry)
264 struct ovl_entry *oe = dentry->d_fsdata;
269 dput(oe->__upperdentry);
270 for (i = 0; i < oe->numlower; i++)
271 dput(oe->lowerstack[i].dentry);
276 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
278 struct ovl_entry *oe = dentry->d_fsdata;
282 for (i = 0; i < oe->numlower; i++) {
283 struct dentry *d = oe->lowerstack[i].dentry;
285 if (d->d_flags & DCACHE_OP_REVALIDATE) {
286 ret = d->d_op->d_revalidate(d, flags);
290 if (!(flags & LOOKUP_RCU))
299 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
301 struct ovl_entry *oe = dentry->d_fsdata;
305 for (i = 0; i < oe->numlower; i++) {
306 struct dentry *d = oe->lowerstack[i].dentry;
308 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
309 ret = d->d_op->d_weak_revalidate(d, flags);
317 static const struct dentry_operations ovl_dentry_operations = {
318 .d_release = ovl_dentry_release,
319 .d_select_inode = ovl_d_select_inode,
322 static const struct dentry_operations ovl_reval_dentry_operations = {
323 .d_release = ovl_dentry_release,
324 .d_revalidate = ovl_dentry_revalidate,
325 .d_weak_revalidate = ovl_dentry_weak_revalidate,
328 static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
330 size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
331 struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
334 oe->numlower = numlower;
339 static bool ovl_dentry_remote(struct dentry *dentry)
341 return dentry->d_flags &
342 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
345 static bool ovl_dentry_weird(struct dentry *dentry)
347 return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
348 DCACHE_MANAGE_TRANSIT |
353 static inline struct dentry *ovl_lookup_real(struct dentry *dir,
356 struct dentry *dentry;
358 mutex_lock(&dir->d_inode->i_mutex);
359 dentry = lookup_one_len(name->name, dir, name->len);
360 mutex_unlock(&dir->d_inode->i_mutex);
362 if (IS_ERR(dentry)) {
363 if (PTR_ERR(dentry) == -ENOENT)
365 } else if (!dentry->d_inode) {
368 } else if (ovl_dentry_weird(dentry)) {
370 /* Don't support traversing automounts and other weirdness */
371 dentry = ERR_PTR(-EREMOTE);
377 * Returns next layer in stack starting from top.
378 * Returns -1 if this is the last layer.
380 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
382 struct ovl_entry *oe = dentry->d_fsdata;
386 ovl_path_upper(dentry, path);
388 return oe->numlower ? 1 : -1;
391 BUG_ON(idx > oe->numlower);
392 *path = oe->lowerstack[idx - 1];
394 return (idx < oe->numlower) ? idx + 1 : -1;
397 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
400 struct ovl_entry *oe;
401 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
402 struct path *stack = NULL;
403 struct dentry *upperdir, *upperdentry = NULL;
404 unsigned int ctr = 0;
405 struct inode *inode = NULL;
406 bool upperopaque = false;
407 struct dentry *this, *prev = NULL;
411 upperdir = ovl_upperdentry_dereference(poe);
413 this = ovl_lookup_real(upperdir, &dentry->d_name);
419 if (unlikely(ovl_dentry_remote(this))) {
424 if (ovl_is_whiteout(this)) {
428 } else if (poe->numlower && ovl_is_opaquedir(this)) {
432 upperdentry = prev = this;
435 if (!upperopaque && poe->numlower) {
437 stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
442 for (i = 0; !upperopaque && i < poe->numlower; i++) {
444 struct path lowerpath = poe->lowerstack[i];
446 this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
450 * If it's positive, then treat ENAMETOOLONG as ENOENT.
452 if (err == -ENAMETOOLONG && (upperdentry || ctr))
458 if (ovl_is_whiteout(this)) {
463 * Only makes sense to check opaque dir if this is not the
466 if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
469 if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
470 !S_ISDIR(this->d_inode->i_mode))) {
472 * FIXME: check for upper-opaqueness maybe better done
475 if (prev == upperdentry)
481 * If this is a non-directory then stop here.
483 if (!S_ISDIR(this->d_inode->i_mode))
486 stack[ctr].dentry = this;
487 stack[ctr].mnt = lowerpath.mnt;
494 oe = ovl_alloc_entry(ctr);
499 if (upperdentry || ctr) {
500 struct dentry *realdentry;
502 realdentry = upperdentry ? upperdentry : stack[0].dentry;
505 inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
509 ovl_copyattr(realdentry->d_inode, inode);
512 oe->opaque = upperopaque;
513 oe->__upperdentry = upperdentry;
514 memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
516 dentry->d_fsdata = oe;
517 d_add(dentry, inode);
524 for (i = 0; i < ctr; i++)
525 dput(stack[i].dentry);
533 struct file *ovl_path_open(struct path *path, int flags)
535 return dentry_open(path, flags, current_cred());
538 static void ovl_put_super(struct super_block *sb)
540 struct ovl_fs *ufs = sb->s_fs_info;
544 mntput(ufs->upper_mnt);
545 for (i = 0; i < ufs->numlower; i++)
546 mntput(ufs->lower_mnt[i]);
547 kfree(ufs->lower_mnt);
549 kfree(ufs->config.lowerdir);
550 kfree(ufs->config.upperdir);
551 kfree(ufs->config.workdir);
557 * @sb: The overlayfs super block
558 * @buf: The struct kstatfs to fill in with stats
560 * Get the filesystem statistics. As writes always target the upper layer
561 * filesystem pass the statfs to the upper filesystem (if it exists)
563 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
565 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
566 struct dentry *root_dentry = dentry->d_sb->s_root;
570 ovl_path_real(root_dentry, &path);
572 err = vfs_statfs(&path, buf);
574 buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
575 buf->f_type = OVERLAYFS_SUPER_MAGIC;
584 * Prints the mount options for a given superblock.
585 * Returns zero; does not fail.
587 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
589 struct super_block *sb = dentry->d_sb;
590 struct ovl_fs *ufs = sb->s_fs_info;
592 seq_show_option(m, "lowerdir", ufs->config.lowerdir);
593 if (ufs->config.upperdir) {
594 seq_show_option(m, "upperdir", ufs->config.upperdir);
595 seq_show_option(m, "workdir", ufs->config.workdir);
600 static int ovl_remount(struct super_block *sb, int *flags, char *data)
602 struct ovl_fs *ufs = sb->s_fs_info;
604 if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
610 static const struct super_operations ovl_super_operations = {
611 .put_super = ovl_put_super,
612 .statfs = ovl_statfs,
613 .show_options = ovl_show_options,
614 .remount_fs = ovl_remount,
624 static const match_table_t ovl_tokens = {
625 {OPT_LOWERDIR, "lowerdir=%s"},
626 {OPT_UPPERDIR, "upperdir=%s"},
627 {OPT_WORKDIR, "workdir=%s"},
631 static char *ovl_next_opt(char **s)
639 for (p = sbegin; *p; p++) {
644 } else if (*p == ',') {
654 static int ovl_parse_opt(char *opt, struct ovl_config *config)
658 while ((p = ovl_next_opt(&opt)) != NULL) {
660 substring_t args[MAX_OPT_ARGS];
665 token = match_token(p, ovl_tokens, args);
668 kfree(config->upperdir);
669 config->upperdir = match_strdup(&args[0]);
670 if (!config->upperdir)
675 kfree(config->lowerdir);
676 config->lowerdir = match_strdup(&args[0]);
677 if (!config->lowerdir)
682 kfree(config->workdir);
683 config->workdir = match_strdup(&args[0]);
684 if (!config->workdir)
689 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
694 /* Workdir is useless in non-upper mount */
695 if (!config->upperdir && config->workdir) {
696 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
698 kfree(config->workdir);
699 config->workdir = NULL;
705 #define OVL_WORKDIR_NAME "work"
707 static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
708 struct dentry *dentry)
710 struct inode *dir = dentry->d_inode;
713 bool retried = false;
715 err = mnt_want_write(mnt);
719 mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
721 work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
722 strlen(OVL_WORKDIR_NAME));
725 struct kstat stat = {
735 ovl_cleanup(dir, work);
740 err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
745 mutex_unlock(&dir->i_mutex);
756 static void ovl_unescape(char *s)
769 static int ovl_mount_dir_noesc(const char *name, struct path *path)
774 pr_err("overlayfs: empty lowerdir\n");
777 err = kern_path(name, LOOKUP_FOLLOW, path);
779 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
783 if (ovl_dentry_weird(path->dentry)) {
784 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
787 if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
788 pr_err("overlayfs: '%s' not a directory\n", name);
799 static int ovl_mount_dir(const char *name, struct path *path)
802 char *tmp = kstrdup(name, GFP_KERNEL);
806 err = ovl_mount_dir_noesc(tmp, path);
809 if (ovl_dentry_remote(path->dentry)) {
810 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
820 static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
821 int *stack_depth, bool *remote)
824 struct kstatfs statfs;
826 err = ovl_mount_dir_noesc(name, path);
830 err = vfs_statfs(path, &statfs);
832 pr_err("overlayfs: statfs failed on '%s'\n", name);
835 *namelen = max(*namelen, statfs.f_namelen);
836 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
838 if (ovl_dentry_remote(path->dentry))
849 /* Workdir should not be subdir of upperdir and vice versa */
850 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
854 if (workdir != upperdir) {
855 ok = (lock_rename(workdir, upperdir) == NULL);
856 unlock_rename(workdir, upperdir);
861 static unsigned int ovl_split_lowerdirs(char *str)
863 unsigned int ctr = 1;
866 for (s = d = str;; s++, d++) {
869 } else if (*s == ':') {
881 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
883 struct path upperpath = { NULL, NULL };
884 struct path workpath = { NULL, NULL };
885 struct dentry *root_dentry;
886 struct ovl_entry *oe;
888 struct path *stack = NULL;
891 unsigned int numlower;
892 unsigned int stacklen = 0;
898 ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
902 err = ovl_parse_opt((char *) data, &ufs->config);
904 goto out_free_config;
907 if (!ufs->config.lowerdir) {
908 pr_err("overlayfs: missing 'lowerdir'\n");
909 goto out_free_config;
912 sb->s_stack_depth = 0;
913 if (ufs->config.upperdir) {
914 if (!ufs->config.workdir) {
915 pr_err("overlayfs: missing 'workdir'\n");
916 goto out_free_config;
919 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
921 goto out_free_config;
923 /* Upper fs should not be r/o */
924 if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
925 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
927 goto out_put_upperpath;
930 err = ovl_mount_dir(ufs->config.workdir, &workpath);
932 goto out_put_upperpath;
935 if (upperpath.mnt != workpath.mnt) {
936 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
937 goto out_put_workpath;
939 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
940 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
941 goto out_put_workpath;
943 sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
946 lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
948 goto out_put_workpath;
951 stacklen = ovl_split_lowerdirs(lowertmp);
952 if (stacklen > OVL_MAX_STACK) {
953 pr_err("overlayfs: too many lower directries, limit is %d\n",
955 goto out_free_lowertmp;
956 } else if (!ufs->config.upperdir && stacklen == 1) {
957 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
958 goto out_free_lowertmp;
961 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
963 goto out_free_lowertmp;
966 for (numlower = 0; numlower < stacklen; numlower++) {
967 err = ovl_lower_dir(lower, &stack[numlower],
968 &ufs->lower_namelen, &sb->s_stack_depth,
971 goto out_put_lowerpath;
973 lower = strchr(lower, '\0') + 1;
978 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
979 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
980 goto out_put_lowerpath;
983 if (ufs->config.upperdir) {
984 ufs->upper_mnt = clone_private_mount(&upperpath);
985 err = PTR_ERR(ufs->upper_mnt);
986 if (IS_ERR(ufs->upper_mnt)) {
987 pr_err("overlayfs: failed to clone upperpath\n");
988 goto out_put_lowerpath;
991 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
992 err = PTR_ERR(ufs->workdir);
993 if (IS_ERR(ufs->workdir)) {
994 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
995 ufs->config.workdir, OVL_WORKDIR_NAME, -err);
996 sb->s_flags |= MS_RDONLY;
1002 ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1003 if (ufs->lower_mnt == NULL)
1004 goto out_put_workdir;
1005 for (i = 0; i < numlower; i++) {
1006 struct vfsmount *mnt = clone_private_mount(&stack[i]);
1010 pr_err("overlayfs: failed to clone lowerpath\n");
1011 goto out_put_lower_mnt;
1014 * Make lower_mnt R/O. That way fchmod/fchown on lower file
1015 * will fail instead of modifying lower fs.
1017 mnt->mnt_flags |= MNT_READONLY;
1019 ufs->lower_mnt[ufs->numlower] = mnt;
1023 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1024 if (!ufs->upper_mnt)
1025 sb->s_flags |= MS_RDONLY;
1028 sb->s_d_op = &ovl_reval_dentry_operations;
1030 sb->s_d_op = &ovl_dentry_operations;
1033 oe = ovl_alloc_entry(numlower);
1035 goto out_put_lower_mnt;
1037 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
1041 mntput(upperpath.mnt);
1042 for (i = 0; i < numlower; i++)
1043 mntput(stack[i].mnt);
1044 path_put(&workpath);
1047 oe->__upperdentry = upperpath.dentry;
1048 for (i = 0; i < numlower; i++) {
1049 oe->lowerstack[i].dentry = stack[i].dentry;
1050 oe->lowerstack[i].mnt = ufs->lower_mnt[i];
1054 root_dentry->d_fsdata = oe;
1056 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1057 sb->s_op = &ovl_super_operations;
1058 sb->s_root = root_dentry;
1059 sb->s_fs_info = ufs;
1066 for (i = 0; i < ufs->numlower; i++)
1067 mntput(ufs->lower_mnt[i]);
1068 kfree(ufs->lower_mnt);
1071 mntput(ufs->upper_mnt);
1073 for (i = 0; i < numlower; i++)
1074 path_put(&stack[i]);
1079 path_put(&workpath);
1081 path_put(&upperpath);
1083 kfree(ufs->config.lowerdir);
1084 kfree(ufs->config.upperdir);
1085 kfree(ufs->config.workdir);
1091 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1092 const char *dev_name, void *raw_data)
1094 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1097 static struct file_system_type ovl_fs_type = {
1098 .owner = THIS_MODULE,
1101 .kill_sb = kill_anon_super,
1103 MODULE_ALIAS_FS("overlay");
1105 static int __init ovl_init(void)
1107 return register_filesystem(&ovl_fs_type);
1110 static void __exit ovl_exit(void)
1112 unregister_filesystem(&ovl_fs_type);
1115 module_init(ovl_init);
1116 module_exit(ovl_exit);