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(idmap: &nop_mnt_idmap, inode, dir, mode);
65 inode->i_mapping->a_ops = &ram_aops;
66 mapping_set_gfp_mask(m: inode->i_mapping, GFP_HIGHUSER);
67 mapping_set_unevictable(mapping: 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(sb: dir->i_sb, dir, mode, dev);
102 int error = -ENOSPC;
103
104 if (inode) {
105 error = security_inode_init_security(inode, dir,
106 qstr: &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(inode: dir, ts: inode_set_ctime_current(inode: dir));
117 }
118out:
119 return error;
120}
121
122static struct dentry *ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
123 struct dentry *dentry, umode_t mode)
124{
125 int retval = ramfs_mknod(idmap: &nop_mnt_idmap, dir, dentry, mode: mode | S_IFDIR, dev: 0);
126 if (!retval)
127 inc_nlink(inode: dir);
128 return ERR_PTR(error: 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(idmap: &nop_mnt_idmap, dir, dentry, mode: mode | S_IFREG, dev: 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(sb: dir->i_sb, dir, S_IFLNK|S_IRWXUGO, dev: 0);
144 if (inode) {
145 int l = strlen(symname)+1;
146
147 error = security_inode_init_security(inode, dir,
148 qstr: &dentry->d_name, NULL,
149 NULL);
150 if (error) {
151 iput(inode);
152 goto out;
153 }
154
155 error = page_symlink(inode, symname, len: l);
156 if (!error) {
157 d_instantiate(dentry, inode);
158 dget(dentry);
159 inode_set_mtime_to_ts(inode: dir,
160 ts: inode_set_ctime_current(inode: 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(sb: dir->i_sb, dir, mode, dev: 0);
175 if (!inode)
176 return -ENOSPC;
177
178 error = security_inode_init_security(inode, dir,
179 qstr: &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, fmt: ",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 = inode_just_drop,
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, desc: ramfs_fs_parameters, param, result: &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_d_flags = DCACHE_DONTCACHE;
273 sb->s_time_gran = 1;
274
275 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, dev: 0);
276 sb->s_root = d_make_root(inode);
277 if (!sb->s_root)
278 return -ENOMEM;
279
280 return 0;
281}
282
283static int ramfs_get_tree(struct fs_context *fc)
284{
285 return get_tree_nodev(fc, fill_super: ramfs_fill_super);
286}
287
288static void ramfs_free_fc(struct fs_context *fc)
289{
290 kfree(objp: fc->s_fs_info);
291}
292
293static const struct fs_context_operations ramfs_context_ops = {
294 .free = ramfs_free_fc,
295 .parse_param = ramfs_parse_param,
296 .get_tree = ramfs_get_tree,
297};
298
299int ramfs_init_fs_context(struct fs_context *fc)
300{
301 struct ramfs_fs_info *fsi;
302
303 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
304 if (!fsi)
305 return -ENOMEM;
306
307 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
308 fc->s_fs_info = fsi;
309 fc->ops = &ramfs_context_ops;
310 return 0;
311}
312
313void ramfs_kill_sb(struct super_block *sb)
314{
315 kfree(objp: sb->s_fs_info);
316 kill_litter_super(sb);
317}
318
319static struct file_system_type ramfs_fs_type = {
320 .name = "ramfs",
321 .init_fs_context = ramfs_init_fs_context,
322 .parameters = ramfs_fs_parameters,
323 .kill_sb = ramfs_kill_sb,
324 .fs_flags = FS_USERNS_MOUNT,
325};
326
327static int __init init_ramfs_fs(void)
328{
329 return register_filesystem(&ramfs_fs_type);
330}
331fs_initcall(init_ramfs_fs);
332