2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
5 * Ported the filesystem routines to 2.5.
6 * 2003-02-10 Petr Baudis <pasky@ucw.cz>
10 #include <linux/magic.h>
11 #include <linux/module.h>
13 #include <linux/pagemap.h>
14 #include <linux/statfs.h>
15 #include <linux/slab.h>
16 #include <linux/seq_file.h>
17 #include <linux/mount.h>
18 #include <linux/namei.h>
23 struct hostfs_inode_info {
26 struct inode vfs_inode;
27 struct mutex open_mutex;
30 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
32 return list_entry(inode, struct hostfs_inode_info, vfs_inode);
35 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
37 static struct kmem_cache *hostfs_inode_cache;
39 /* Changed in hostfs_args before the kernel starts running */
40 static char *root_ino = "";
41 static int append = 0;
43 static const struct inode_operations hostfs_iops;
44 static const struct inode_operations hostfs_dir_iops;
45 static const struct inode_operations hostfs_link_iops;
48 static int __init hostfs_args(char *options, int *add)
52 ptr = strchr(options, ',');
60 ptr = strchr(options, ',');
63 if (*options != '\0') {
64 if (!strcmp(options, "append"))
66 else printf("hostfs_args - unsupported option - %s\n",
74 __uml_setup("hostfs=", hostfs_args,
75 "hostfs=<root dir>,<flags>,...\n"
76 " This is used to set hostfs parameters. The root directory argument\n"
77 " is used to confine all hostfs mounts to within the specified directory\n"
78 " tree on the host. If this isn't specified, then a user inside UML can\n"
79 " mount anything on the host that's accessible to the user that's running\n"
81 " The only flag currently supported is 'append', which specifies that all\n"
82 " files opened by hostfs will be opened in append mode.\n\n"
86 static char *__dentry_name(struct dentry *dentry, char *name)
88 char *p = dentry_path_raw(dentry, name, PATH_MAX);
92 root = dentry->d_sb->s_fs_info;
100 * This function relies on the fact that dentry_path_raw() will place
101 * the path name at the end of the provided buffer.
103 BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);
105 strlcpy(name, root, PATH_MAX);
106 if (len > p - name) {
112 strcpy(name + len, p);
117 static char *dentry_name(struct dentry *dentry)
119 char *name = __getname();
123 return __dentry_name(dentry, name);
126 static char *inode_name(struct inode *ino)
128 struct dentry *dentry;
131 dentry = d_find_alias(ino);
135 name = dentry_name(dentry);
142 static char *follow_link(char *link)
144 char *name, *resolved, *end;
147 name = kmalloc(PATH_MAX, GFP_KERNEL);
153 n = hostfs_do_readlink(link, name, PATH_MAX);
156 else if (n == PATH_MAX) {
164 end = strrchr(link, '/');
170 resolved = kasprintf(GFP_KERNEL, "%s%s", link, name);
171 if (resolved == NULL) {
184 static struct inode *hostfs_iget(struct super_block *sb)
186 struct inode *inode = new_inode(sb);
188 return ERR_PTR(-ENOMEM);
192 static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
195 * do_statfs uses struct statfs64 internally, but the linux kernel
196 * struct statfs still has 32-bit versions for most of these fields,
197 * so we convert them here
206 err = do_statfs(dentry->d_sb->s_fs_info,
207 &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
208 &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
212 sf->f_blocks = f_blocks;
213 sf->f_bfree = f_bfree;
214 sf->f_bavail = f_bavail;
215 sf->f_files = f_files;
216 sf->f_ffree = f_ffree;
217 sf->f_type = HOSTFS_SUPER_MAGIC;
221 static struct inode *hostfs_alloc_inode(struct super_block *sb)
223 struct hostfs_inode_info *hi;
225 hi = kmem_cache_alloc(hostfs_inode_cache, GFP_KERNEL_ACCOUNT);
230 inode_init_once(&hi->vfs_inode);
231 mutex_init(&hi->open_mutex);
232 return &hi->vfs_inode;
235 static void hostfs_evict_inode(struct inode *inode)
237 truncate_inode_pages_final(&inode->i_data);
239 if (HOSTFS_I(inode)->fd != -1) {
240 close_file(&HOSTFS_I(inode)->fd);
241 HOSTFS_I(inode)->fd = -1;
245 static void hostfs_free_inode(struct inode *inode)
247 kmem_cache_free(hostfs_inode_cache, HOSTFS_I(inode));
250 static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
252 const char *root_path = root->d_sb->s_fs_info;
253 size_t offset = strlen(root_ino) + 1;
255 if (strlen(root_path) > offset)
256 seq_show_option(seq, root_path + offset, NULL);
259 seq_puts(seq, ",append");
264 static const struct super_operations hostfs_sbops = {
265 .alloc_inode = hostfs_alloc_inode,
266 .free_inode = hostfs_free_inode,
267 .evict_inode = hostfs_evict_inode,
268 .statfs = hostfs_statfs,
269 .show_options = hostfs_show_options,
272 static int hostfs_readdir(struct file *file, struct dir_context *ctx)
276 unsigned long long next, ino;
280 name = dentry_name(file->f_path.dentry);
283 dir = open_dir(name, &error);
289 while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
290 if (!dir_emit(ctx, name, len, ino, type))
298 static int hostfs_open(struct inode *ino, struct file *file)
305 mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
306 if ((mode & HOSTFS_I(ino)->mode) == mode)
309 mode |= HOSTFS_I(ino)->mode;
314 if (mode & FMODE_READ)
316 if (mode & FMODE_WRITE)
319 name = dentry_name(d_real(file->f_path.dentry, file->f_inode));
323 fd = open_file(name, r, w, append);
328 mutex_lock(&HOSTFS_I(ino)->open_mutex);
329 /* somebody else had handled it first? */
330 if ((mode & HOSTFS_I(ino)->mode) == mode) {
331 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
335 if ((mode | HOSTFS_I(ino)->mode) != mode) {
336 mode |= HOSTFS_I(ino)->mode;
337 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
341 if (HOSTFS_I(ino)->fd == -1) {
342 HOSTFS_I(ino)->fd = fd;
344 err = replace_file(fd, HOSTFS_I(ino)->fd);
347 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
351 HOSTFS_I(ino)->mode = mode;
352 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
357 static int hostfs_file_release(struct inode *inode, struct file *file)
359 filemap_write_and_wait(inode->i_mapping);
364 static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
367 struct inode *inode = file->f_mapping->host;
370 ret = file_write_and_wait_range(file, start, end);
375 ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
381 static const struct file_operations hostfs_file_fops = {
382 .llseek = generic_file_llseek,
383 .splice_read = generic_file_splice_read,
384 .read_iter = generic_file_read_iter,
385 .write_iter = generic_file_write_iter,
386 .mmap = generic_file_mmap,
388 .release = hostfs_file_release,
389 .fsync = hostfs_fsync,
392 static const struct file_operations hostfs_dir_fops = {
393 .llseek = generic_file_llseek,
394 .iterate_shared = hostfs_readdir,
395 .read = generic_read_dir,
397 .fsync = hostfs_fsync,
400 static int hostfs_writepage(struct page *page, struct writeback_control *wbc)
402 struct address_space *mapping = page->mapping;
403 struct inode *inode = mapping->host;
405 loff_t base = page_offset(page);
406 int count = PAGE_SIZE;
407 int end_index = inode->i_size >> PAGE_SHIFT;
410 if (page->index >= end_index)
411 count = inode->i_size & (PAGE_SIZE-1);
415 err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
417 ClearPageUptodate(page);
421 if (base > inode->i_size)
422 inode->i_size = base;
425 ClearPageError(page);
435 static int hostfs_readpage(struct file *file, struct page *page)
438 loff_t start = page_offset(page);
439 int bytes_read, ret = 0;
442 bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
444 if (bytes_read < 0) {
445 ClearPageUptodate(page);
451 memset(buffer + bytes_read, 0, PAGE_SIZE - bytes_read);
453 ClearPageError(page);
454 SetPageUptodate(page);
457 flush_dcache_page(page);
463 static int hostfs_write_begin(struct file *file, struct address_space *mapping,
464 loff_t pos, unsigned len, unsigned flags,
465 struct page **pagep, void **fsdata)
467 pgoff_t index = pos >> PAGE_SHIFT;
469 *pagep = grab_cache_page_write_begin(mapping, index, flags);
475 static int hostfs_write_end(struct file *file, struct address_space *mapping,
476 loff_t pos, unsigned len, unsigned copied,
477 struct page *page, void *fsdata)
479 struct inode *inode = mapping->host;
481 unsigned from = pos & (PAGE_SIZE - 1);
485 err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
488 if (!PageUptodate(page) && err == PAGE_SIZE)
489 SetPageUptodate(page);
492 * If err > 0, write_file has added err to pos, so we are comparing
493 * i_size against the last byte written.
495 if (err > 0 && (pos > inode->i_size))
503 static const struct address_space_operations hostfs_aops = {
504 .writepage = hostfs_writepage,
505 .readpage = hostfs_readpage,
506 .set_page_dirty = __set_page_dirty_nobuffers,
507 .write_begin = hostfs_write_begin,
508 .write_end = hostfs_write_end,
511 static int read_name(struct inode *ino, char *name)
514 struct hostfs_stat st;
515 int err = stat_file(name, &st, -1);
519 /* Reencode maj and min with the kernel encoding.*/
520 rdev = MKDEV(st.maj, st.min);
522 switch (st.mode & S_IFMT) {
524 ino->i_op = &hostfs_link_iops;
527 ino->i_op = &hostfs_dir_iops;
528 ino->i_fop = &hostfs_dir_fops;
534 init_special_inode(ino, st.mode & S_IFMT, rdev);
535 ino->i_op = &hostfs_iops;
538 ino->i_op = &hostfs_iops;
539 ino->i_fop = &hostfs_file_fops;
540 ino->i_mapping->a_ops = &hostfs_aops;
547 ino->i_mode = st.mode;
548 set_nlink(ino, st.nlink);
549 i_uid_write(ino, st.uid);
550 i_gid_write(ino, st.gid);
551 ino->i_atime = (struct timespec64){ st.atime.tv_sec, st.atime.tv_nsec };
552 ino->i_mtime = (struct timespec64){ st.mtime.tv_sec, st.mtime.tv_nsec };
553 ino->i_ctime = (struct timespec64){ st.ctime.tv_sec, st.ctime.tv_nsec };
554 ino->i_size = st.size;
555 ino->i_blocks = st.blocks;
559 static int hostfs_create(struct user_namespace *mnt_userns, struct inode *dir,
560 struct dentry *dentry, umode_t mode, bool excl)
566 inode = hostfs_iget(dir->i_sb);
568 error = PTR_ERR(inode);
573 name = dentry_name(dentry);
577 fd = file_create(name, mode & 0777);
581 error = read_name(inode, name);
587 HOSTFS_I(inode)->fd = fd;
588 HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
589 d_instantiate(dentry, inode);
598 static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
605 inode = hostfs_iget(ino->i_sb);
610 name = dentry_name(dentry);
612 err = read_name(inode, name);
617 inode = (err == -ENOENT) ? NULL : ERR_PTR(err);
620 return d_splice_alias(inode, dentry);
623 static int hostfs_link(struct dentry *to, struct inode *ino,
626 char *from_name, *to_name;
629 if ((from_name = dentry_name(from)) == NULL)
631 to_name = dentry_name(to);
632 if (to_name == NULL) {
633 __putname(from_name);
636 err = link_file(to_name, from_name);
637 __putname(from_name);
642 static int hostfs_unlink(struct inode *ino, struct dentry *dentry)
650 if ((file = dentry_name(dentry)) == NULL)
653 err = unlink_file(file);
658 static int hostfs_symlink(struct user_namespace *mnt_userns, struct inode *ino,
659 struct dentry *dentry, const char *to)
664 if ((file = dentry_name(dentry)) == NULL)
666 err = make_symlink(file, to);
671 static int hostfs_mkdir(struct user_namespace *mnt_userns, struct inode *ino,
672 struct dentry *dentry, umode_t mode)
677 if ((file = dentry_name(dentry)) == NULL)
679 err = do_mkdir(file, mode);
684 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
689 if ((file = dentry_name(dentry)) == NULL)
691 err = hostfs_do_rmdir(file);
696 static int hostfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
697 struct dentry *dentry, umode_t mode, dev_t dev)
703 inode = hostfs_iget(dir->i_sb);
705 err = PTR_ERR(inode);
710 name = dentry_name(dentry);
714 err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
718 err = read_name(inode, name);
723 d_instantiate(dentry, inode);
734 static int hostfs_rename2(struct user_namespace *mnt_userns,
735 struct inode *old_dir, struct dentry *old_dentry,
736 struct inode *new_dir, struct dentry *new_dentry,
739 char *old_name, *new_name;
742 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
745 old_name = dentry_name(old_dentry);
746 if (old_name == NULL)
748 new_name = dentry_name(new_dentry);
749 if (new_name == NULL) {
754 err = rename_file(old_name, new_name);
756 err = rename2_file(old_name, new_name, flags);
763 static int hostfs_permission(struct user_namespace *mnt_userns,
764 struct inode *ino, int desired)
767 int r = 0, w = 0, x = 0, err;
769 if (desired & MAY_NOT_BLOCK)
772 if (desired & MAY_READ) r = 1;
773 if (desired & MAY_WRITE) w = 1;
774 if (desired & MAY_EXEC) x = 1;
775 name = inode_name(ino);
779 if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
780 S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
783 err = access_file(name, r, w, x);
786 err = generic_permission(&init_user_ns, ino, desired);
790 static int hostfs_setattr(struct user_namespace *mnt_userns,
791 struct dentry *dentry, struct iattr *attr)
793 struct inode *inode = d_inode(dentry);
794 struct hostfs_iattr attrs;
798 int fd = HOSTFS_I(inode)->fd;
800 err = setattr_prepare(&init_user_ns, dentry, attr);
805 attr->ia_valid &= ~ATTR_SIZE;
808 if (attr->ia_valid & ATTR_MODE) {
809 attrs.ia_valid |= HOSTFS_ATTR_MODE;
810 attrs.ia_mode = attr->ia_mode;
812 if (attr->ia_valid & ATTR_UID) {
813 attrs.ia_valid |= HOSTFS_ATTR_UID;
814 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
816 if (attr->ia_valid & ATTR_GID) {
817 attrs.ia_valid |= HOSTFS_ATTR_GID;
818 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
820 if (attr->ia_valid & ATTR_SIZE) {
821 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
822 attrs.ia_size = attr->ia_size;
824 if (attr->ia_valid & ATTR_ATIME) {
825 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
826 attrs.ia_atime = (struct hostfs_timespec)
827 { attr->ia_atime.tv_sec, attr->ia_atime.tv_nsec };
829 if (attr->ia_valid & ATTR_MTIME) {
830 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
831 attrs.ia_mtime = (struct hostfs_timespec)
832 { attr->ia_mtime.tv_sec, attr->ia_mtime.tv_nsec };
834 if (attr->ia_valid & ATTR_CTIME) {
835 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
836 attrs.ia_ctime = (struct hostfs_timespec)
837 { attr->ia_ctime.tv_sec, attr->ia_ctime.tv_nsec };
839 if (attr->ia_valid & ATTR_ATIME_SET) {
840 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
842 if (attr->ia_valid & ATTR_MTIME_SET) {
843 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
845 name = dentry_name(dentry);
848 err = set_attr(name, &attrs, fd);
853 if ((attr->ia_valid & ATTR_SIZE) &&
854 attr->ia_size != i_size_read(inode))
855 truncate_setsize(inode, attr->ia_size);
857 setattr_copy(&init_user_ns, inode, attr);
858 mark_inode_dirty(inode);
862 static const struct inode_operations hostfs_iops = {
863 .permission = hostfs_permission,
864 .setattr = hostfs_setattr,
867 static const struct inode_operations hostfs_dir_iops = {
868 .create = hostfs_create,
869 .lookup = hostfs_lookup,
871 .unlink = hostfs_unlink,
872 .symlink = hostfs_symlink,
873 .mkdir = hostfs_mkdir,
874 .rmdir = hostfs_rmdir,
875 .mknod = hostfs_mknod,
876 .rename = hostfs_rename2,
877 .permission = hostfs_permission,
878 .setattr = hostfs_setattr,
881 static const char *hostfs_get_link(struct dentry *dentry,
883 struct delayed_call *done)
887 return ERR_PTR(-ECHILD);
888 link = kmalloc(PATH_MAX, GFP_KERNEL);
890 char *path = dentry_name(dentry);
893 err = hostfs_do_readlink(path, link, PATH_MAX);
903 return ERR_PTR(-ENOMEM);
906 set_delayed_call(done, kfree_link, link);
910 static const struct inode_operations hostfs_link_iops = {
911 .get_link = hostfs_get_link,
914 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
916 struct inode *root_inode;
917 char *host_root_path, *req_root = d;
920 sb->s_blocksize = 1024;
921 sb->s_blocksize_bits = 10;
922 sb->s_magic = HOSTFS_SUPER_MAGIC;
923 sb->s_op = &hostfs_sbops;
924 sb->s_d_op = &simple_dentry_operations;
925 sb->s_maxbytes = MAX_LFS_FILESIZE;
927 /* NULL is printed as '(null)' by printf(): avoid that. */
928 if (req_root == NULL)
932 sb->s_fs_info = host_root_path =
933 kasprintf(GFP_KERNEL, "%s/%s", root_ino, req_root);
934 if (host_root_path == NULL)
937 root_inode = new_inode(sb);
941 err = read_name(root_inode, host_root_path);
945 if (S_ISLNK(root_inode->i_mode)) {
946 char *name = follow_link(host_root_path);
951 err = read_name(root_inode, name);
958 sb->s_root = d_make_root(root_inode);
959 if (sb->s_root == NULL)
970 static struct dentry *hostfs_read_sb(struct file_system_type *type,
971 int flags, const char *dev_name,
974 return mount_nodev(type, flags, data, hostfs_fill_sb_common);
977 static void hostfs_kill_sb(struct super_block *s)
983 static struct file_system_type hostfs_type = {
984 .owner = THIS_MODULE,
986 .mount = hostfs_read_sb,
987 .kill_sb = hostfs_kill_sb,
990 MODULE_ALIAS_FS("hostfs");
992 static int __init init_hostfs(void)
994 hostfs_inode_cache = KMEM_CACHE(hostfs_inode_info, 0);
995 if (!hostfs_inode_cache)
997 return register_filesystem(&hostfs_type);
1000 static void __exit exit_hostfs(void)
1002 unregister_filesystem(&hostfs_type);
1003 kmem_cache_destroy(hostfs_inode_cache);
1006 module_init(init_hostfs)
1007 module_exit(exit_hostfs)
1008 MODULE_LICENSE("GPL");