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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 <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);