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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 <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(&init_user_ns, 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 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(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 user_namespace *mnt_userns, 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 d_instantiate(dentry, inode);
106 dget(dentry); /* Extra count - pin the dentry in core */
107 error = 0;
108 dir->i_mtime = dir->i_ctime = current_time(dir);
109 }
110 return error;
111}
112
113static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
114 struct dentry *dentry, umode_t mode)
115{
116 int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0);
117 if (!retval)
118 inc_nlink(dir);
119 return retval;
120}
121
122static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir,
123 struct dentry *dentry, umode_t mode, bool excl)
124{
125 return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
126}
127
128static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
129 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 int ramfs_tmpfile(struct user_namespace *mnt_userns,
149 struct inode *dir, struct file *file, umode_t mode)
150{
151 struct inode *inode;
152
153 inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
154 if (!inode)
155 return -ENOSPC;
156 d_tmpfile(file, inode);
157 return finish_open_simple(file, 0);
158}
159
160static const struct inode_operations ramfs_dir_inode_operations = {
161 .create = ramfs_create,
162 .lookup = simple_lookup,
163 .link = simple_link,
164 .unlink = simple_unlink,
165 .symlink = ramfs_symlink,
166 .mkdir = ramfs_mkdir,
167 .rmdir = simple_rmdir,
168 .mknod = ramfs_mknod,
169 .rename = simple_rename,
170 .tmpfile = ramfs_tmpfile,
171};
172
173/*
174 * Display the mount options in /proc/mounts.
175 */
176static int ramfs_show_options(struct seq_file *m, struct dentry *root)
177{
178 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
179
180 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
181 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
182 return 0;
183}
184
185static const struct super_operations ramfs_ops = {
186 .statfs = simple_statfs,
187 .drop_inode = generic_delete_inode,
188 .show_options = ramfs_show_options,
189};
190
191enum ramfs_param {
192 Opt_mode,
193};
194
195const struct fs_parameter_spec ramfs_fs_parameters[] = {
196 fsparam_u32oct("mode", Opt_mode),
197 {}
198};
199
200static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
201{
202 struct fs_parse_result result;
203 struct ramfs_fs_info *fsi = fc->s_fs_info;
204 int opt;
205
206 opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
207 if (opt == -ENOPARAM) {
208 opt = vfs_parse_fs_param_source(fc, param);
209 if (opt != -ENOPARAM)
210 return opt;
211 /*
212 * We might like to report bad mount options here;
213 * but traditionally ramfs has ignored all mount options,
214 * and as it is used as a !CONFIG_SHMEM simple substitute
215 * for tmpfs, better continue to ignore other mount options.
216 */
217 return 0;
218 }
219 if (opt < 0)
220 return opt;
221
222 switch (opt) {
223 case Opt_mode:
224 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
225 break;
226 }
227
228 return 0;
229}
230
231static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
232{
233 struct ramfs_fs_info *fsi = sb->s_fs_info;
234 struct inode *inode;
235
236 sb->s_maxbytes = MAX_LFS_FILESIZE;
237 sb->s_blocksize = PAGE_SIZE;
238 sb->s_blocksize_bits = PAGE_SHIFT;
239 sb->s_magic = RAMFS_MAGIC;
240 sb->s_op = &ramfs_ops;
241 sb->s_time_gran = 1;
242
243 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
244 sb->s_root = d_make_root(inode);
245 if (!sb->s_root)
246 return -ENOMEM;
247
248 return 0;
249}
250
251static int ramfs_get_tree(struct fs_context *fc)
252{
253 return get_tree_nodev(fc, ramfs_fill_super);
254}
255
256static void ramfs_free_fc(struct fs_context *fc)
257{
258 kfree(fc->s_fs_info);
259}
260
261static const struct fs_context_operations ramfs_context_ops = {
262 .free = ramfs_free_fc,
263 .parse_param = ramfs_parse_param,
264 .get_tree = ramfs_get_tree,
265};
266
267int ramfs_init_fs_context(struct fs_context *fc)
268{
269 struct ramfs_fs_info *fsi;
270
271 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
272 if (!fsi)
273 return -ENOMEM;
274
275 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
276 fc->s_fs_info = fsi;
277 fc->ops = &ramfs_context_ops;
278 return 0;
279}
280
281static void ramfs_kill_sb(struct super_block *sb)
282{
283 kfree(sb->s_fs_info);
284 kill_litter_super(sb);
285}
286
287static struct file_system_type ramfs_fs_type = {
288 .name = "ramfs",
289 .init_fs_context = ramfs_init_fs_context,
290 .parameters = ramfs_fs_parameters,
291 .kill_sb = ramfs_kill_sb,
292 .fs_flags = FS_USERNS_MOUNT,
293};
294
295static int __init init_ramfs_fs(void)
296{
297 return register_filesystem(&ramfs_fs_type);
298}
299fs_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 <asm/uaccess.h>
39#include "internal.h"
40
41#define RAMFS_DEFAULT_MODE 0755
42
43static const struct super_operations ramfs_ops;
44static const struct inode_operations ramfs_dir_inode_operations;
45
46static const struct address_space_operations ramfs_aops = {
47 .readpage = simple_readpage,
48 .write_begin = simple_write_begin,
49 .write_end = simple_write_end,
50 .set_page_dirty = __set_page_dirty_no_writeback,
51};
52
53struct inode *ramfs_get_inode(struct super_block *sb,
54 const struct inode *dir, umode_t mode, dev_t dev)
55{
56 struct inode * inode = new_inode(sb);
57
58 if (inode) {
59 inode->i_ino = get_next_ino();
60 inode_init_owner(inode, dir, mode);
61 inode->i_mapping->a_ops = &ramfs_aops;
62 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
63 mapping_set_unevictable(inode->i_mapping);
64 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
65 switch (mode & S_IFMT) {
66 default:
67 init_special_inode(inode, mode, dev);
68 break;
69 case S_IFREG:
70 inode->i_op = &ramfs_file_inode_operations;
71 inode->i_fop = &ramfs_file_operations;
72 break;
73 case S_IFDIR:
74 inode->i_op = &ramfs_dir_inode_operations;
75 inode->i_fop = &simple_dir_operations;
76
77 /* directory inodes start off with i_nlink == 2 (for "." entry) */
78 inc_nlink(inode);
79 break;
80 case S_IFLNK:
81 inode->i_op = &page_symlink_inode_operations;
82 inode_nohighmem(inode);
83 break;
84 }
85 }
86 return inode;
87}
88
89/*
90 * File creation. Allocate an inode, and we're done..
91 */
92/* SMP-safe */
93static int
94ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
95{
96 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
97 int error = -ENOSPC;
98
99 if (inode) {
100 d_instantiate(dentry, inode);
101 dget(dentry); /* Extra count - pin the dentry in core */
102 error = 0;
103 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
104 }
105 return error;
106}
107
108static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
109{
110 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
111 if (!retval)
112 inc_nlink(dir);
113 return retval;
114}
115
116static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
117{
118 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
119}
120
121static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
122{
123 struct inode *inode;
124 int error = -ENOSPC;
125
126 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
127 if (inode) {
128 int l = strlen(symname)+1;
129 error = page_symlink(inode, symname, l);
130 if (!error) {
131 d_instantiate(dentry, inode);
132 dget(dentry);
133 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
134 } else
135 iput(inode);
136 }
137 return error;
138}
139
140static const struct inode_operations ramfs_dir_inode_operations = {
141 .create = ramfs_create,
142 .lookup = simple_lookup,
143 .link = simple_link,
144 .unlink = simple_unlink,
145 .symlink = ramfs_symlink,
146 .mkdir = ramfs_mkdir,
147 .rmdir = simple_rmdir,
148 .mknod = ramfs_mknod,
149 .rename = simple_rename,
150};
151
152static const struct super_operations ramfs_ops = {
153 .statfs = simple_statfs,
154 .drop_inode = generic_delete_inode,
155 .show_options = generic_show_options,
156};
157
158struct ramfs_mount_opts {
159 umode_t mode;
160};
161
162enum {
163 Opt_mode,
164 Opt_err
165};
166
167static const match_table_t tokens = {
168 {Opt_mode, "mode=%o"},
169 {Opt_err, NULL}
170};
171
172struct ramfs_fs_info {
173 struct ramfs_mount_opts mount_opts;
174};
175
176static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
177{
178 substring_t args[MAX_OPT_ARGS];
179 int option;
180 int token;
181 char *p;
182
183 opts->mode = RAMFS_DEFAULT_MODE;
184
185 while ((p = strsep(&data, ",")) != NULL) {
186 if (!*p)
187 continue;
188
189 token = match_token(p, tokens, args);
190 switch (token) {
191 case Opt_mode:
192 if (match_octal(&args[0], &option))
193 return -EINVAL;
194 opts->mode = option & S_IALLUGO;
195 break;
196 /*
197 * We might like to report bad mount options here;
198 * but traditionally ramfs has ignored all mount options,
199 * and as it is used as a !CONFIG_SHMEM simple substitute
200 * for tmpfs, better continue to ignore other mount options.
201 */
202 }
203 }
204
205 return 0;
206}
207
208int ramfs_fill_super(struct super_block *sb, void *data, int silent)
209{
210 struct ramfs_fs_info *fsi;
211 struct inode *inode;
212 int err;
213
214 save_mount_options(sb, data);
215
216 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
217 sb->s_fs_info = fsi;
218 if (!fsi)
219 return -ENOMEM;
220
221 err = ramfs_parse_options(data, &fsi->mount_opts);
222 if (err)
223 return err;
224
225 sb->s_maxbytes = MAX_LFS_FILESIZE;
226 sb->s_blocksize = PAGE_SIZE;
227 sb->s_blocksize_bits = PAGE_SHIFT;
228 sb->s_magic = RAMFS_MAGIC;
229 sb->s_op = &ramfs_ops;
230 sb->s_time_gran = 1;
231
232 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
233 sb->s_root = d_make_root(inode);
234 if (!sb->s_root)
235 return -ENOMEM;
236
237 return 0;
238}
239
240struct dentry *ramfs_mount(struct file_system_type *fs_type,
241 int flags, const char *dev_name, void *data)
242{
243 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
244}
245
246static void ramfs_kill_sb(struct super_block *sb)
247{
248 kfree(sb->s_fs_info);
249 kill_litter_super(sb);
250}
251
252static struct file_system_type ramfs_fs_type = {
253 .name = "ramfs",
254 .mount = ramfs_mount,
255 .kill_sb = ramfs_kill_sb,
256 .fs_flags = FS_USERNS_MOUNT,
257};
258
259int __init init_ramfs_fs(void)
260{
261 static unsigned long once;
262
263 if (test_and_set_bit(0, &once))
264 return 0;
265 return register_filesystem(&ramfs_fs_type);
266}
267fs_initcall(init_ramfs_fs);