Line data Source code
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 4 : struct inode *ramfs_get_inode(struct super_block *sb,
58 : const struct inode *dir, umode_t mode, dev_t dev)
59 : {
60 4 : struct inode * inode = new_inode(sb);
61 :
62 4 : if (inode) {
63 4 : inode->i_ino = get_next_ino();
64 4 : inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
65 4 : inode->i_mapping->a_ops = &ram_aops;
66 8 : mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
67 8 : mapping_set_unevictable(inode->i_mapping);
68 4 : inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
69 4 : switch (mode & S_IFMT) {
70 : default:
71 1 : init_special_inode(inode, mode, dev);
72 1 : break;
73 : case S_IFREG:
74 0 : inode->i_op = &ramfs_file_inode_operations;
75 0 : inode->i_fop = &ramfs_file_operations;
76 0 : break;
77 : case S_IFDIR:
78 3 : inode->i_op = &ramfs_dir_inode_operations;
79 3 : inode->i_fop = &simple_dir_operations;
80 :
81 : /* directory inodes start off with i_nlink == 2 (for "." entry) */
82 3 : inc_nlink(inode);
83 3 : break;
84 : case S_IFLNK:
85 0 : inode->i_op = &page_symlink_inode_operations;
86 0 : inode_nohighmem(inode);
87 0 : break;
88 : }
89 : }
90 4 : return inode;
91 : }
92 :
93 : /*
94 : * File creation. Allocate an inode, and we're done..
95 : */
96 : /* SMP-safe */
97 : static int
98 3 : ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
99 : struct dentry *dentry, umode_t mode, dev_t dev)
100 : {
101 3 : struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
102 3 : int error = -ENOSPC;
103 :
104 3 : if (inode) {
105 3 : d_instantiate(dentry, inode);
106 3 : dget(dentry); /* Extra count - pin the dentry in core */
107 3 : error = 0;
108 3 : dir->i_mtime = dir->i_ctime = current_time(dir);
109 : }
110 3 : return error;
111 : }
112 :
113 2 : static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
114 : struct dentry *dentry, umode_t mode)
115 : {
116 2 : int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0);
117 2 : if (!retval)
118 2 : inc_nlink(dir);
119 2 : return retval;
120 : }
121 :
122 0 : static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir,
123 : struct dentry *dentry, umode_t mode, bool excl)
124 : {
125 0 : return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
126 : }
127 :
128 0 : static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
129 : struct dentry *dentry, const char *symname)
130 : {
131 : struct inode *inode;
132 0 : int error = -ENOSPC;
133 :
134 0 : inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
135 0 : if (inode) {
136 0 : int l = strlen(symname)+1;
137 0 : error = page_symlink(inode, symname, l);
138 0 : if (!error) {
139 0 : d_instantiate(dentry, inode);
140 0 : dget(dentry);
141 0 : dir->i_mtime = dir->i_ctime = current_time(dir);
142 : } else
143 0 : iput(inode);
144 : }
145 0 : return error;
146 : }
147 :
148 0 : static int ramfs_tmpfile(struct mnt_idmap *idmap,
149 : struct inode *dir, struct file *file, umode_t mode)
150 : {
151 : struct inode *inode;
152 :
153 0 : inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
154 0 : if (!inode)
155 : return -ENOSPC;
156 0 : d_tmpfile(file, inode);
157 0 : return finish_open_simple(file, 0);
158 : }
159 :
160 : static 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 : */
176 0 : static int ramfs_show_options(struct seq_file *m, struct dentry *root)
177 : {
178 0 : struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
179 :
180 0 : if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
181 0 : seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
182 0 : return 0;
183 : }
184 :
185 : static const struct super_operations ramfs_ops = {
186 : .statfs = simple_statfs,
187 : .drop_inode = generic_delete_inode,
188 : .show_options = ramfs_show_options,
189 : };
190 :
191 : enum ramfs_param {
192 : Opt_mode,
193 : };
194 :
195 : const struct fs_parameter_spec ramfs_fs_parameters[] = {
196 : fsparam_u32oct("mode", Opt_mode),
197 : {}
198 : };
199 :
200 1 : static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
201 : {
202 : struct fs_parse_result result;
203 1 : struct ramfs_fs_info *fsi = fc->s_fs_info;
204 : int opt;
205 :
206 1 : opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
207 1 : if (opt == -ENOPARAM) {
208 1 : opt = vfs_parse_fs_param_source(fc, param);
209 1 : 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 0 : return 0;
218 : }
219 0 : if (opt < 0)
220 : return opt;
221 :
222 0 : switch (opt) {
223 : case Opt_mode:
224 0 : fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
225 0 : break;
226 : }
227 :
228 : return 0;
229 : }
230 :
231 1 : static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
232 : {
233 1 : struct ramfs_fs_info *fsi = sb->s_fs_info;
234 : struct inode *inode;
235 :
236 1 : sb->s_maxbytes = MAX_LFS_FILESIZE;
237 1 : sb->s_blocksize = PAGE_SIZE;
238 1 : sb->s_blocksize_bits = PAGE_SHIFT;
239 1 : sb->s_magic = RAMFS_MAGIC;
240 1 : sb->s_op = &ramfs_ops;
241 1 : sb->s_time_gran = 1;
242 :
243 1 : inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
244 1 : sb->s_root = d_make_root(inode);
245 1 : if (!sb->s_root)
246 : return -ENOMEM;
247 :
248 1 : return 0;
249 : }
250 :
251 1 : static int ramfs_get_tree(struct fs_context *fc)
252 : {
253 1 : return get_tree_nodev(fc, ramfs_fill_super);
254 : }
255 :
256 1 : static void ramfs_free_fc(struct fs_context *fc)
257 : {
258 1 : kfree(fc->s_fs_info);
259 1 : }
260 :
261 : static 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 :
267 1 : int ramfs_init_fs_context(struct fs_context *fc)
268 : {
269 : struct ramfs_fs_info *fsi;
270 :
271 1 : fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
272 1 : if (!fsi)
273 : return -ENOMEM;
274 :
275 1 : fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
276 1 : fc->s_fs_info = fsi;
277 1 : fc->ops = &ramfs_context_ops;
278 1 : return 0;
279 : }
280 :
281 0 : static void ramfs_kill_sb(struct super_block *sb)
282 : {
283 0 : kfree(sb->s_fs_info);
284 0 : kill_litter_super(sb);
285 0 : }
286 :
287 : static 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 :
295 1 : static int __init init_ramfs_fs(void)
296 : {
297 1 : return register_filesystem(&ramfs_fs_type);
298 : }
299 : fs_initcall(init_ramfs_fs);
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