1/*
2 * Resizable simple ram filesystem for Linux.
3 *
4 * Copyright (C) 2000 Linus Torvalds.
5 *               2000 Transmeta Corp.
6 *
7 * Usage limits added by David Gibson, Linuxcare Australia.
8 * This file is released under the GPL.
9 */
10
11/*
12 * NOTE! This filesystem is probably most useful
13 * not as a real filesystem, but as an example of
14 * how virtual filesystems can be written.
15 *
16 * It doesn't get much simpler than this. Consider
17 * that this file implements the full semantics of
18 * a POSIX-compliant read-write filesystem.
19 *
20 * Note in particular how the filesystem does not
21 * need to implement any data structures of its own
22 * to keep track of the virtual data: using the VFS
23 * caches is sufficient.
24 */
25
26#include <linux/fs.h>
27#include <linux/pagemap.h>
28#include <linux/highmem.h>
29#include <linux/time.h>
30#include <linux/init.h>
31#include <linux/string.h>
32#include <linux/backing-dev.h>
33#include <linux/ramfs.h>
34#include <linux/sched.h>
35#include <linux/parser.h>
36#include <linux/magic.h>
37#include <linux/slab.h>
38#include <linux/uaccess.h>
39#include <linux/fs_context.h>
40#include <linux/fs_parser.h>
41#include <linux/seq_file.h>
42#include "internal.h"
43
44struct ramfs_mount_opts {
45	umode_t mode;
46};
47
48struct ramfs_fs_info {
49	struct ramfs_mount_opts mount_opts;
50};
51
52#define RAMFS_DEFAULT_MODE	0755
53
54static const struct super_operations ramfs_ops;
55static const struct inode_operations ramfs_dir_inode_operations;
56
57struct inode *ramfs_get_inode(struct super_block *sb,
58				const struct inode *dir, umode_t mode, dev_t dev)
59{
60	struct inode * inode = new_inode(sb);
61
62	if (inode) {
63		inode->i_ino = get_next_ino();
64		inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
65		inode->i_mapping->a_ops = &ram_aops;
66		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
67		mapping_set_unevictable(inode->i_mapping);
68		simple_inode_init_ts(inode);
69		switch (mode & S_IFMT) {
70		default:
71			init_special_inode(inode, mode, dev);
72			break;
73		case S_IFREG:
74			inode->i_op = &ramfs_file_inode_operations;
75			inode->i_fop = &ramfs_file_operations;
76			break;
77		case S_IFDIR:
78			inode->i_op = &ramfs_dir_inode_operations;
79			inode->i_fop = &simple_dir_operations;
80
81			/* directory inodes start off with i_nlink == 2 (for "." entry) */
82			inc_nlink(inode);
83			break;
84		case S_IFLNK:
85			inode->i_op = &page_symlink_inode_operations;
86			inode_nohighmem(inode);
87			break;
88		}
89	}
90	return inode;
91}
92
93/*
94 * File creation. Allocate an inode, and we're done..
95 */
96/* SMP-safe */
97static int
98ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
99	    struct dentry *dentry, umode_t mode, dev_t dev)
100{
101	struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
102	int error = -ENOSPC;
103
104	if (inode) {
105		error = security_inode_init_security(inode, dir,
106						     &dentry->d_name, NULL,
107						     NULL);
108		if (error) {
109			iput(inode);
110			goto out;
111		}
112
113		d_instantiate(dentry, inode);
114		dget(dentry);	/* Extra count - pin the dentry in core */
115		error = 0;
116		inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
117	}
118out:
119	return error;
120}
121
122static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
123		       struct dentry *dentry, umode_t mode)
124{
125	int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0);
126	if (!retval)
127		inc_nlink(dir);
128	return retval;
129}
130
131static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir,
132			struct dentry *dentry, umode_t mode, bool excl)
133{
134	return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
135}
136
137static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
138			 struct dentry *dentry, const char *symname)
139{
140	struct inode *inode;
141	int error = -ENOSPC;
142
143	inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
144	if (inode) {
145		int l = strlen(symname)+1;
146
147		error = security_inode_init_security(inode, dir,
148						     &dentry->d_name, NULL,
149						     NULL);
150		if (error) {
151			iput(inode);
152			goto out;
153		}
154
155		error = page_symlink(inode, symname, l);
156		if (!error) {
157			d_instantiate(dentry, inode);
158			dget(dentry);
159			inode_set_mtime_to_ts(dir,
160					      inode_set_ctime_current(dir));
161		} else
162			iput(inode);
163	}
164out:
165	return error;
166}
167
168static int ramfs_tmpfile(struct mnt_idmap *idmap,
169			 struct inode *dir, struct file *file, umode_t mode)
170{
171	struct inode *inode;
172	int error;
173
174	inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
175	if (!inode)
176		return -ENOSPC;
177
178	error = security_inode_init_security(inode, dir,
179					     &file_dentry(file)->d_name, NULL,
180					     NULL);
181	if (error) {
182		iput(inode);
183		goto out;
184	}
185
186	d_tmpfile(file, inode);
187out:
188	return finish_open_simple(file, error);
189}
190
191static const struct inode_operations ramfs_dir_inode_operations = {
192	.create		= ramfs_create,
193	.lookup		= simple_lookup,
194	.link		= simple_link,
195	.unlink		= simple_unlink,
196	.symlink	= ramfs_symlink,
197	.mkdir		= ramfs_mkdir,
198	.rmdir		= simple_rmdir,
199	.mknod		= ramfs_mknod,
200	.rename		= simple_rename,
201	.tmpfile	= ramfs_tmpfile,
202};
203
204/*
205 * Display the mount options in /proc/mounts.
206 */
207static int ramfs_show_options(struct seq_file *m, struct dentry *root)
208{
209	struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
210
211	if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
212		seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
213	return 0;
214}
215
216static const struct super_operations ramfs_ops = {
217	.statfs		= simple_statfs,
218	.drop_inode	= generic_delete_inode,
219	.show_options	= ramfs_show_options,
220};
221
222enum ramfs_param {
223	Opt_mode,
224};
225
226const struct fs_parameter_spec ramfs_fs_parameters[] = {
227	fsparam_u32oct("mode",	Opt_mode),
228	{}
229};
230
231static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
232{
233	struct fs_parse_result result;
234	struct ramfs_fs_info *fsi = fc->s_fs_info;
235	int opt;
236
237	opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
238	if (opt == -ENOPARAM) {
239		opt = vfs_parse_fs_param_source(fc, param);
240		if (opt != -ENOPARAM)
241			return opt;
242		/*
243		 * We might like to report bad mount options here;
244		 * but traditionally ramfs has ignored all mount options,
245		 * and as it is used as a !CONFIG_SHMEM simple substitute
246		 * for tmpfs, better continue to ignore other mount options.
247		 */
248		return 0;
249	}
250	if (opt < 0)
251		return opt;
252
253	switch (opt) {
254	case Opt_mode:
255		fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
256		break;
257	}
258
259	return 0;
260}
261
262static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
263{
264	struct ramfs_fs_info *fsi = sb->s_fs_info;
265	struct inode *inode;
266
267	sb->s_maxbytes		= MAX_LFS_FILESIZE;
268	sb->s_blocksize		= PAGE_SIZE;
269	sb->s_blocksize_bits	= PAGE_SHIFT;
270	sb->s_magic		= RAMFS_MAGIC;
271	sb->s_op		= &ramfs_ops;
272	sb->s_time_gran		= 1;
273
274	inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
275	sb->s_root = d_make_root(inode);
276	if (!sb->s_root)
277		return -ENOMEM;
278
279	return 0;
280}
281
282static int ramfs_get_tree(struct fs_context *fc)
283{
284	return get_tree_nodev(fc, ramfs_fill_super);
285}
286
287static void ramfs_free_fc(struct fs_context *fc)
288{
289	kfree(fc->s_fs_info);
290}
291
292static const struct fs_context_operations ramfs_context_ops = {
293	.free		= ramfs_free_fc,
294	.parse_param	= ramfs_parse_param,
295	.get_tree	= ramfs_get_tree,
296};
297
298int ramfs_init_fs_context(struct fs_context *fc)
299{
300	struct ramfs_fs_info *fsi;
301
302	fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
303	if (!fsi)
304		return -ENOMEM;
305
306	fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
307	fc->s_fs_info = fsi;
308	fc->ops = &ramfs_context_ops;
309	return 0;
310}
311
312void ramfs_kill_sb(struct super_block *sb)
313{
314	kfree(sb->s_fs_info);
315	kill_litter_super(sb);
316}
317
318static struct file_system_type ramfs_fs_type = {
319	.name		= "ramfs",
320	.init_fs_context = ramfs_init_fs_context,
321	.parameters	= ramfs_fs_parameters,
322	.kill_sb	= ramfs_kill_sb,
323	.fs_flags	= FS_USERNS_MOUNT,
324};
325
326static int __init init_ramfs_fs(void)
327{
328	return register_filesystem(&ramfs_fs_type);
329}
330fs_initcall(init_ramfs_fs);
331