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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 <asm/uaccess.h>
39 #include "internal.h"
40
41 #define RAMFS_DEFAULT_MODE 0755
42
43 static const struct super_operations ramfs_ops;
44 static const struct inode_operations ramfs_dir_inode_operations;
45
46 static struct backing_dev_info ramfs_backing_dev_info = {
47 .name = "ramfs",
48 .ra_pages = 0, /* No readahead */
49 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK |
50 BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
51 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
52 };
53
54 struct inode *ramfs_get_inode(struct super_block *sb,
55 const struct inode *dir, int mode, dev_t dev)
56 {
57 struct inode * inode = new_inode(sb);
58
59 if (inode) {
60 inode->i_ino = get_next_ino();
61 inode_init_owner(inode, dir, mode);
62 inode->i_mapping->a_ops = &ramfs_aops;
63 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
64 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
65 mapping_set_unevictable(inode->i_mapping);
66 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
67 switch (mode & S_IFMT) {
68 default:
69 init_special_inode(inode, mode, dev);
70 break;
71 case S_IFREG:
72 inode->i_op = &ramfs_file_inode_operations;
73 inode->i_fop = &ramfs_file_operations;
74 break;
75 case S_IFDIR:
76 inode->i_op = &ramfs_dir_inode_operations;
77 inode->i_fop = &simple_dir_operations;
78
79 /* directory inodes start off with i_nlink == 2 (for "." entry) */
80 inc_nlink(inode);
81 break;
82 case S_IFLNK:
83 inode->i_op = &page_symlink_inode_operations;
84 break;
85 }
86 }
87 return inode;
88 }
89
90 /*
91 * File creation. Allocate an inode, and we're done..
92 */
93 /* SMP-safe */
94 static int
95 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
96 {
97 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
98 int error = -ENOSPC;
99
100 if (inode) {
101 d_instantiate(dentry, inode);
102 dget(dentry); /* Extra count - pin the dentry in core */
103 error = 0;
104 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
105 }
106 return error;
107 }
108
109 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
110 {
111 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
112 if (!retval)
113 inc_nlink(dir);
114 return retval;
115 }
116
117 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
118 {
119 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
120 }
121
122 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
123 {
124 struct inode *inode;
125 int error = -ENOSPC;
126
127 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
128 if (inode) {
129 int l = strlen(symname)+1;
130 error = page_symlink(inode, symname, l);
131 if (!error) {
132 d_instantiate(dentry, inode);
133 dget(dentry);
134 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
135 } else
136 iput(inode);
137 }
138 return error;
139 }
140
141 static const struct inode_operations ramfs_dir_inode_operations = {
142 .create = ramfs_create,
143 .lookup = simple_lookup,
144 .link = simple_link,
145 .unlink = simple_unlink,
146 .symlink = ramfs_symlink,
147 .mkdir = ramfs_mkdir,
148 .rmdir = simple_rmdir,
149 .mknod = ramfs_mknod,
150 .rename = simple_rename,
151 };
152
153 static const struct super_operations ramfs_ops = {
154 .statfs = simple_statfs,
155 .drop_inode = generic_delete_inode,
156 .show_options = generic_show_options,
157 };
158
159 struct ramfs_mount_opts {
160 umode_t mode;
161 };
162
163 enum {
164 Opt_mode,
165 Opt_err
166 };
167
168 static const match_table_t tokens = {
169 {Opt_mode, "mode=%o"},
170 {Opt_err, NULL}
171 };
172
173 struct ramfs_fs_info {
174 struct ramfs_mount_opts mount_opts;
175 };
176
177 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
178 {
179 substring_t args[MAX_OPT_ARGS];
180 int option;
181 int token;
182 char *p;
183
184 opts->mode = RAMFS_DEFAULT_MODE;
185
186 while ((p = strsep(&data, ",")) != NULL) {
187 if (!*p)
188 continue;
189
190 token = match_token(p, tokens, args);
191 switch (token) {
192 case Opt_mode:
193 if (match_octal(&args[0], &option))
194 return -EINVAL;
195 opts->mode = option & S_IALLUGO;
196 break;
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 }
204 }
205
206 return 0;
207 }
208
209 int ramfs_fill_super(struct super_block *sb, void *data, int silent)
210 {
211 struct ramfs_fs_info *fsi;
212 struct inode *inode = NULL;
213 struct dentry *root;
214 int err;
215
216 save_mount_options(sb, data);
217
218 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
219 sb->s_fs_info = fsi;
220 if (!fsi) {
221 err = -ENOMEM;
222 goto fail;
223 }
224
225 err = ramfs_parse_options(data, &fsi->mount_opts);
226 if (err)
227 goto fail;
228
229 sb->s_maxbytes = MAX_LFS_FILESIZE;
230 sb->s_blocksize = PAGE_CACHE_SIZE;
231 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
232 sb->s_magic = RAMFS_MAGIC;
233 sb->s_op = &ramfs_ops;
234 sb->s_time_gran = 1;
235
236 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
237 if (!inode) {
238 err = -ENOMEM;
239 goto fail;
240 }
241
242 root = d_alloc_root(inode);
243 sb->s_root = root;
244 if (!root) {
245 err = -ENOMEM;
246 goto fail;
247 }
248
249 return 0;
250 fail:
251 kfree(fsi);
252 sb->s_fs_info = NULL;
253 iput(inode);
254 return err;
255 }
256
257 struct dentry *ramfs_mount(struct file_system_type *fs_type,
258 int flags, const char *dev_name, void *data)
259 {
260 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
261 }
262
263 static struct dentry *rootfs_mount(struct file_system_type *fs_type,
264 int flags, const char *dev_name, void *data)
265 {
266 return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
267 }
268
269 static void ramfs_kill_sb(struct super_block *sb)
270 {
271 kfree(sb->s_fs_info);
272 kill_litter_super(sb);
273 }
274
275 static struct file_system_type ramfs_fs_type = {
276 .name = "ramfs",
277 .mount = ramfs_mount,
278 .kill_sb = ramfs_kill_sb,
279 };
280 static struct file_system_type rootfs_fs_type = {
281 .name = "rootfs",
282 .mount = rootfs_mount,
283 .kill_sb = kill_litter_super,
284 };
285
286 static int __init init_ramfs_fs(void)
287 {
288 return register_filesystem(&ramfs_fs_type);
289 }
290 module_init(init_ramfs_fs)
291
292 int __init init_rootfs(void)
293 {
294 int err;
295
296 err = bdi_init(&ramfs_backing_dev_info);
297 if (err)
298 return err;
299
300 err = register_filesystem(&rootfs_fs_type);
301 if (err)
302 bdi_destroy(&ramfs_backing_dev_info);
303
304 return err;
305 }