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 | |
44 | struct ramfs_mount_opts { |
45 | umode_t mode; |
46 | }; |
47 | |
48 | struct ramfs_fs_info { |
49 | struct ramfs_mount_opts mount_opts; |
50 | }; |
51 | |
52 | #define RAMFS_DEFAULT_MODE 0755 |
53 | |
54 | static const struct super_operations ramfs_ops; |
55 | static const struct inode_operations ramfs_dir_inode_operations; |
56 | |
57 | struct 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(idmap: &nop_mnt_idmap, inode, dir, mode); |
65 | inode->i_mapping->a_ops = &ram_aops; |
66 | mapping_set_gfp_mask(m: inode->i_mapping, GFP_HIGHUSER); |
67 | mapping_set_unevictable(mapping: 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 */ |
97 | static int |
98 | ramfs_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(sb: 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 | inode_set_mtime_to_ts(inode: dir, ts: inode_set_ctime_current(inode: dir)); |
109 | } |
110 | return error; |
111 | } |
112 | |
113 | static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir, |
114 | struct dentry *dentry, umode_t mode) |
115 | { |
116 | int retval = ramfs_mknod(idmap: &nop_mnt_idmap, dir, dentry, mode: mode | S_IFDIR, dev: 0); |
117 | if (!retval) |
118 | inc_nlink(inode: dir); |
119 | return retval; |
120 | } |
121 | |
122 | static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir, |
123 | struct dentry *dentry, umode_t mode, bool excl) |
124 | { |
125 | return ramfs_mknod(idmap: &nop_mnt_idmap, dir, dentry, mode: mode | S_IFREG, dev: 0); |
126 | } |
127 | |
128 | static int ramfs_symlink(struct mnt_idmap *idmap, 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(sb: dir->i_sb, dir, S_IFLNK|S_IRWXUGO, dev: 0); |
135 | if (inode) { |
136 | int l = strlen(symname)+1; |
137 | error = page_symlink(inode, symname, len: l); |
138 | if (!error) { |
139 | d_instantiate(dentry, inode); |
140 | dget(dentry); |
141 | inode_set_mtime_to_ts(inode: dir, |
142 | ts: inode_set_ctime_current(inode: dir)); |
143 | } else |
144 | iput(inode); |
145 | } |
146 | return error; |
147 | } |
148 | |
149 | static int ramfs_tmpfile(struct mnt_idmap *idmap, |
150 | struct inode *dir, struct file *file, umode_t mode) |
151 | { |
152 | struct inode *inode; |
153 | |
154 | inode = ramfs_get_inode(sb: dir->i_sb, dir, mode, dev: 0); |
155 | if (!inode) |
156 | return -ENOSPC; |
157 | d_tmpfile(file, inode); |
158 | return finish_open_simple(file, error: 0); |
159 | } |
160 | |
161 | static const struct inode_operations ramfs_dir_inode_operations = { |
162 | .create = ramfs_create, |
163 | .lookup = simple_lookup, |
164 | .link = simple_link, |
165 | .unlink = simple_unlink, |
166 | .symlink = ramfs_symlink, |
167 | .mkdir = ramfs_mkdir, |
168 | .rmdir = simple_rmdir, |
169 | .mknod = ramfs_mknod, |
170 | .rename = simple_rename, |
171 | .tmpfile = ramfs_tmpfile, |
172 | }; |
173 | |
174 | /* |
175 | * Display the mount options in /proc/mounts. |
176 | */ |
177 | static int ramfs_show_options(struct seq_file *m, struct dentry *root) |
178 | { |
179 | struct ramfs_fs_info *fsi = root->d_sb->s_fs_info; |
180 | |
181 | if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE) |
182 | seq_printf(m, fmt: ",mode=%o" , fsi->mount_opts.mode); |
183 | return 0; |
184 | } |
185 | |
186 | static const struct super_operations ramfs_ops = { |
187 | .statfs = simple_statfs, |
188 | .drop_inode = generic_delete_inode, |
189 | .show_options = ramfs_show_options, |
190 | }; |
191 | |
192 | enum ramfs_param { |
193 | Opt_mode, |
194 | }; |
195 | |
196 | const struct fs_parameter_spec ramfs_fs_parameters[] = { |
197 | fsparam_u32oct("mode" , Opt_mode), |
198 | {} |
199 | }; |
200 | |
201 | static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param) |
202 | { |
203 | struct fs_parse_result result; |
204 | struct ramfs_fs_info *fsi = fc->s_fs_info; |
205 | int opt; |
206 | |
207 | opt = fs_parse(fc, desc: ramfs_fs_parameters, param, result: &result); |
208 | if (opt == -ENOPARAM) { |
209 | opt = vfs_parse_fs_param_source(fc, param); |
210 | if (opt != -ENOPARAM) |
211 | return opt; |
212 | /* |
213 | * We might like to report bad mount options here; |
214 | * but traditionally ramfs has ignored all mount options, |
215 | * and as it is used as a !CONFIG_SHMEM simple substitute |
216 | * for tmpfs, better continue to ignore other mount options. |
217 | */ |
218 | return 0; |
219 | } |
220 | if (opt < 0) |
221 | return opt; |
222 | |
223 | switch (opt) { |
224 | case Opt_mode: |
225 | fsi->mount_opts.mode = result.uint_32 & S_IALLUGO; |
226 | break; |
227 | } |
228 | |
229 | return 0; |
230 | } |
231 | |
232 | static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc) |
233 | { |
234 | struct ramfs_fs_info *fsi = sb->s_fs_info; |
235 | struct inode *inode; |
236 | |
237 | sb->s_maxbytes = MAX_LFS_FILESIZE; |
238 | sb->s_blocksize = PAGE_SIZE; |
239 | sb->s_blocksize_bits = PAGE_SHIFT; |
240 | sb->s_magic = RAMFS_MAGIC; |
241 | sb->s_op = &ramfs_ops; |
242 | sb->s_time_gran = 1; |
243 | |
244 | inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, dev: 0); |
245 | sb->s_root = d_make_root(inode); |
246 | if (!sb->s_root) |
247 | return -ENOMEM; |
248 | |
249 | return 0; |
250 | } |
251 | |
252 | static int ramfs_get_tree(struct fs_context *fc) |
253 | { |
254 | return get_tree_nodev(fc, fill_super: ramfs_fill_super); |
255 | } |
256 | |
257 | static void ramfs_free_fc(struct fs_context *fc) |
258 | { |
259 | kfree(objp: fc->s_fs_info); |
260 | } |
261 | |
262 | static const struct fs_context_operations ramfs_context_ops = { |
263 | .free = ramfs_free_fc, |
264 | .parse_param = ramfs_parse_param, |
265 | .get_tree = ramfs_get_tree, |
266 | }; |
267 | |
268 | int ramfs_init_fs_context(struct fs_context *fc) |
269 | { |
270 | struct ramfs_fs_info *fsi; |
271 | |
272 | fsi = kzalloc(size: sizeof(*fsi), GFP_KERNEL); |
273 | if (!fsi) |
274 | return -ENOMEM; |
275 | |
276 | fsi->mount_opts.mode = RAMFS_DEFAULT_MODE; |
277 | fc->s_fs_info = fsi; |
278 | fc->ops = &ramfs_context_ops; |
279 | return 0; |
280 | } |
281 | |
282 | void ramfs_kill_sb(struct super_block *sb) |
283 | { |
284 | kfree(objp: sb->s_fs_info); |
285 | kill_litter_super(sb); |
286 | } |
287 | |
288 | static struct file_system_type ramfs_fs_type = { |
289 | .name = "ramfs" , |
290 | .init_fs_context = ramfs_init_fs_context, |
291 | .parameters = ramfs_fs_parameters, |
292 | .kill_sb = ramfs_kill_sb, |
293 | .fs_flags = FS_USERNS_MOUNT, |
294 | }; |
295 | |
296 | static int __init init_ramfs_fs(void) |
297 | { |
298 | return register_filesystem(&ramfs_fs_type); |
299 | } |
300 | fs_initcall(init_ramfs_fs); |
301 | |