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