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 "internal.h"
42 :
43 : struct ramfs_mount_opts {
44 : umode_t mode;
45 : };
46 :
47 : struct ramfs_fs_info {
48 : struct ramfs_mount_opts mount_opts;
49 : };
50 :
51 : #define RAMFS_DEFAULT_MODE 0755
52 :
53 : static const struct super_operations ramfs_ops;
54 : static const struct inode_operations ramfs_dir_inode_operations;
55 :
56 : static 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 :
63 6 : struct inode *ramfs_get_inode(struct super_block *sb,
64 : const struct inode *dir, umode_t mode, dev_t dev)
65 : {
66 6 : struct inode * inode = new_inode(sb);
67 :
68 6 : if (inode) {
69 6 : inode->i_ino = get_next_ino();
70 6 : inode_init_owner(&init_user_ns, inode, dir, mode);
71 6 : inode->i_mapping->a_ops = &ramfs_aops;
72 6 : mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
73 6 : mapping_set_unevictable(inode->i_mapping);
74 6 : inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
75 6 : switch (mode & S_IFMT) {
76 3 : default:
77 3 : init_special_inode(inode, mode, dev);
78 3 : break;
79 0 : case S_IFREG:
80 0 : inode->i_op = &ramfs_file_inode_operations;
81 0 : inode->i_fop = &ramfs_file_operations;
82 0 : break;
83 3 : case S_IFDIR:
84 3 : inode->i_op = &ramfs_dir_inode_operations;
85 3 : inode->i_fop = &simple_dir_operations;
86 :
87 : /* directory inodes start off with i_nlink == 2 (for "." entry) */
88 3 : inc_nlink(inode);
89 3 : break;
90 0 : case S_IFLNK:
91 0 : inode->i_op = &page_symlink_inode_operations;
92 0 : inode_nohighmem(inode);
93 0 : break;
94 : }
95 0 : }
96 6 : return inode;
97 : }
98 :
99 : /*
100 : * File creation. Allocate an inode, and we're done..
101 : */
102 : /* SMP-safe */
103 : static int
104 5 : ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
105 : struct dentry *dentry, umode_t mode, dev_t dev)
106 : {
107 5 : struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
108 5 : int error = -ENOSPC;
109 :
110 5 : if (inode) {
111 5 : d_instantiate(dentry, inode);
112 5 : dget(dentry); /* Extra count - pin the dentry in core */
113 5 : error = 0;
114 5 : dir->i_mtime = dir->i_ctime = current_time(dir);
115 : }
116 5 : return error;
117 : }
118 :
119 2 : static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
120 : struct dentry *dentry, umode_t mode)
121 : {
122 2 : int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0);
123 2 : if (!retval)
124 2 : inc_nlink(dir);
125 2 : return retval;
126 : }
127 :
128 0 : static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir,
129 : struct dentry *dentry, umode_t mode, bool excl)
130 : {
131 0 : return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
132 : }
133 :
134 0 : static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
135 : struct dentry *dentry, const char *symname)
136 : {
137 0 : struct inode *inode;
138 0 : int error = -ENOSPC;
139 :
140 0 : inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
141 0 : if (inode) {
142 0 : int l = strlen(symname)+1;
143 0 : error = page_symlink(inode, symname, l);
144 0 : if (!error) {
145 0 : d_instantiate(dentry, inode);
146 0 : dget(dentry);
147 0 : dir->i_mtime = dir->i_ctime = current_time(dir);
148 : } else
149 0 : iput(inode);
150 : }
151 0 : return error;
152 : }
153 :
154 0 : static int ramfs_tmpfile(struct user_namespace *mnt_userns,
155 : struct inode *dir, struct dentry *dentry, umode_t mode)
156 : {
157 0 : struct inode *inode;
158 :
159 0 : inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
160 0 : if (!inode)
161 : return -ENOSPC;
162 0 : d_tmpfile(dentry, inode);
163 0 : return 0;
164 : }
165 :
166 : static const struct inode_operations ramfs_dir_inode_operations = {
167 : .create = ramfs_create,
168 : .lookup = simple_lookup,
169 : .link = simple_link,
170 : .unlink = simple_unlink,
171 : .symlink = ramfs_symlink,
172 : .mkdir = ramfs_mkdir,
173 : .rmdir = simple_rmdir,
174 : .mknod = ramfs_mknod,
175 : .rename = simple_rename,
176 : .tmpfile = ramfs_tmpfile,
177 : };
178 :
179 : /*
180 : * Display the mount options in /proc/mounts.
181 : */
182 0 : static int ramfs_show_options(struct seq_file *m, struct dentry *root)
183 : {
184 0 : struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
185 :
186 0 : if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
187 0 : seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
188 0 : return 0;
189 : }
190 :
191 : static const struct super_operations ramfs_ops = {
192 : .statfs = simple_statfs,
193 : .drop_inode = generic_delete_inode,
194 : .show_options = ramfs_show_options,
195 : };
196 :
197 : enum ramfs_param {
198 : Opt_mode,
199 : };
200 :
201 : const struct fs_parameter_spec ramfs_fs_parameters[] = {
202 : fsparam_u32oct("mode", Opt_mode),
203 : {}
204 : };
205 :
206 1 : static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
207 : {
208 1 : struct fs_parse_result result;
209 1 : struct ramfs_fs_info *fsi = fc->s_fs_info;
210 1 : int opt;
211 :
212 1 : opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
213 1 : if (opt < 0) {
214 : /*
215 : * We might like to report bad mount options here;
216 : * but traditionally ramfs has ignored all mount options,
217 : * and as it is used as a !CONFIG_SHMEM simple substitute
218 : * for tmpfs, better continue to ignore other mount options.
219 : */
220 1 : if (opt == -ENOPARAM)
221 1 : opt = 0;
222 1 : return opt;
223 : }
224 :
225 0 : switch (opt) {
226 0 : case Opt_mode:
227 0 : fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
228 0 : break;
229 : }
230 :
231 : return 0;
232 : }
233 :
234 1 : static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
235 : {
236 1 : struct ramfs_fs_info *fsi = sb->s_fs_info;
237 1 : struct inode *inode;
238 :
239 1 : sb->s_maxbytes = MAX_LFS_FILESIZE;
240 1 : sb->s_blocksize = PAGE_SIZE;
241 1 : sb->s_blocksize_bits = PAGE_SHIFT;
242 1 : sb->s_magic = RAMFS_MAGIC;
243 1 : sb->s_op = &ramfs_ops;
244 1 : sb->s_time_gran = 1;
245 :
246 1 : inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
247 1 : sb->s_root = d_make_root(inode);
248 1 : if (!sb->s_root)
249 0 : return -ENOMEM;
250 :
251 : return 0;
252 : }
253 :
254 1 : static int ramfs_get_tree(struct fs_context *fc)
255 : {
256 1 : return get_tree_nodev(fc, ramfs_fill_super);
257 : }
258 :
259 1 : static void ramfs_free_fc(struct fs_context *fc)
260 : {
261 1 : kfree(fc->s_fs_info);
262 1 : }
263 :
264 : static const struct fs_context_operations ramfs_context_ops = {
265 : .free = ramfs_free_fc,
266 : .parse_param = ramfs_parse_param,
267 : .get_tree = ramfs_get_tree,
268 : };
269 :
270 1 : int ramfs_init_fs_context(struct fs_context *fc)
271 : {
272 1 : struct ramfs_fs_info *fsi;
273 :
274 1 : fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
275 1 : if (!fsi)
276 : return -ENOMEM;
277 :
278 1 : fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
279 1 : fc->s_fs_info = fsi;
280 1 : fc->ops = &ramfs_context_ops;
281 1 : return 0;
282 : }
283 :
284 0 : static void ramfs_kill_sb(struct super_block *sb)
285 : {
286 0 : kfree(sb->s_fs_info);
287 0 : kill_litter_super(sb);
288 0 : }
289 :
290 : static struct file_system_type ramfs_fs_type = {
291 : .name = "ramfs",
292 : .init_fs_context = ramfs_init_fs_context,
293 : .parameters = ramfs_fs_parameters,
294 : .kill_sb = ramfs_kill_sb,
295 : .fs_flags = FS_USERNS_MOUNT,
296 : };
297 :
298 1 : static int __init init_ramfs_fs(void)
299 : {
300 1 : return register_filesystem(&ramfs_fs_type);
301 : }
302 : fs_initcall(init_ramfs_fs);
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