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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 "internal.h"
40
41struct ramfs_mount_opts {
42 umode_t mode;
43};
44
45struct ramfs_fs_info {
46 struct ramfs_mount_opts mount_opts;
47};
48
49#define RAMFS_DEFAULT_MODE 0755
50
51static const struct super_operations ramfs_ops;
52static const struct inode_operations ramfs_dir_inode_operations;
53
54static const struct address_space_operations ramfs_aops = {
55 .readpage = simple_readpage,
56 .write_begin = simple_write_begin,
57 .write_end = simple_write_end,
58 .set_page_dirty = __set_page_dirty_no_writeback,
59};
60
61struct inode *ramfs_get_inode(struct super_block *sb,
62 const struct inode *dir, umode_t mode, dev_t dev)
63{
64 struct inode * inode = new_inode(sb);
65
66 if (inode) {
67 inode->i_ino = get_next_ino();
68 inode_init_owner(inode, dir, mode);
69 inode->i_mapping->a_ops = &ramfs_aops;
70 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
71 mapping_set_unevictable(inode->i_mapping);
72 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
73 switch (mode & S_IFMT) {
74 default:
75 init_special_inode(inode, mode, dev);
76 break;
77 case S_IFREG:
78 inode->i_op = &ramfs_file_inode_operations;
79 inode->i_fop = &ramfs_file_operations;
80 break;
81 case S_IFDIR:
82 inode->i_op = &ramfs_dir_inode_operations;
83 inode->i_fop = &simple_dir_operations;
84
85 /* directory inodes start off with i_nlink == 2 (for "." entry) */
86 inc_nlink(inode);
87 break;
88 case S_IFLNK:
89 inode->i_op = &page_symlink_inode_operations;
90 inode_nohighmem(inode);
91 break;
92 }
93 }
94 return inode;
95}
96
97/*
98 * File creation. Allocate an inode, and we're done..
99 */
100/* SMP-safe */
101static int
102ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
103{
104 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
105 int error = -ENOSPC;
106
107 if (inode) {
108 d_instantiate(dentry, inode);
109 dget(dentry); /* Extra count - pin the dentry in core */
110 error = 0;
111 dir->i_mtime = dir->i_ctime = current_time(dir);
112 }
113 return error;
114}
115
116static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
117{
118 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
119 if (!retval)
120 inc_nlink(dir);
121 return retval;
122}
123
124static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
125{
126 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
127}
128
129static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
130{
131 struct inode *inode;
132 int error = -ENOSPC;
133
134 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
135 if (inode) {
136 int l = strlen(symname)+1;
137 error = page_symlink(inode, symname, l);
138 if (!error) {
139 d_instantiate(dentry, inode);
140 dget(dentry);
141 dir->i_mtime = dir->i_ctime = current_time(dir);
142 } else
143 iput(inode);
144 }
145 return error;
146}
147
148static const struct inode_operations ramfs_dir_inode_operations = {
149 .create = ramfs_create,
150 .lookup = simple_lookup,
151 .link = simple_link,
152 .unlink = simple_unlink,
153 .symlink = ramfs_symlink,
154 .mkdir = ramfs_mkdir,
155 .rmdir = simple_rmdir,
156 .mknod = ramfs_mknod,
157 .rename = simple_rename,
158};
159
160/*
161 * Display the mount options in /proc/mounts.
162 */
163static int ramfs_show_options(struct seq_file *m, struct dentry *root)
164{
165 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
166
167 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
168 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
169 return 0;
170}
171
172static const struct super_operations ramfs_ops = {
173 .statfs = simple_statfs,
174 .drop_inode = generic_delete_inode,
175 .show_options = ramfs_show_options,
176};
177
178enum {
179 Opt_mode,
180 Opt_err
181};
182
183static const match_table_t tokens = {
184 {Opt_mode, "mode=%o"},
185 {Opt_err, NULL}
186};
187
188static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
189{
190 substring_t args[MAX_OPT_ARGS];
191 int option;
192 int token;
193 char *p;
194
195 opts->mode = RAMFS_DEFAULT_MODE;
196
197 while ((p = strsep(&data, ",")) != NULL) {
198 if (!*p)
199 continue;
200
201 token = match_token(p, tokens, args);
202 switch (token) {
203 case Opt_mode:
204 if (match_octal(&args[0], &option))
205 return -EINVAL;
206 opts->mode = option & S_IALLUGO;
207 break;
208 /*
209 * We might like to report bad mount options here;
210 * but traditionally ramfs has ignored all mount options,
211 * and as it is used as a !CONFIG_SHMEM simple substitute
212 * for tmpfs, better continue to ignore other mount options.
213 */
214 }
215 }
216
217 return 0;
218}
219
220int ramfs_fill_super(struct super_block *sb, void *data, int silent)
221{
222 struct ramfs_fs_info *fsi;
223 struct inode *inode;
224 int err;
225
226 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
227 sb->s_fs_info = fsi;
228 if (!fsi)
229 return -ENOMEM;
230
231 err = ramfs_parse_options(data, &fsi->mount_opts);
232 if (err)
233 return err;
234
235 sb->s_maxbytes = MAX_LFS_FILESIZE;
236 sb->s_blocksize = PAGE_SIZE;
237 sb->s_blocksize_bits = PAGE_SHIFT;
238 sb->s_magic = RAMFS_MAGIC;
239 sb->s_op = &ramfs_ops;
240 sb->s_time_gran = 1;
241
242 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
243 sb->s_root = d_make_root(inode);
244 if (!sb->s_root)
245 return -ENOMEM;
246
247 return 0;
248}
249
250struct dentry *ramfs_mount(struct file_system_type *fs_type,
251 int flags, const char *dev_name, void *data)
252{
253 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
254}
255
256static void ramfs_kill_sb(struct super_block *sb)
257{
258 kfree(sb->s_fs_info);
259 kill_litter_super(sb);
260}
261
262static struct file_system_type ramfs_fs_type = {
263 .name = "ramfs",
264 .mount = ramfs_mount,
265 .kill_sb = ramfs_kill_sb,
266 .fs_flags = FS_USERNS_MOUNT,
267};
268
269int __init init_ramfs_fs(void)
270{
271 static unsigned long once;
272
273 if (test_and_set_bit(0, &once))
274 return 0;
275 return register_filesystem(&ramfs_fs_type);
276}
277fs_initcall(init_ramfs_fs);
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);