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