2 * Resizable simple ram filesystem for Linux.
4 * Copyright (C) 2000 Linus Torvalds.
7 * Usage limits added by David Gibson, Linuxcare Australia.
8 * This file is released under the GPL.
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.
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.
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.
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>
43 struct ramfs_mount_opts {
47 struct ramfs_fs_info {
48 struct ramfs_mount_opts mount_opts;
51 #define RAMFS_DEFAULT_MODE 0755
53 static const struct super_operations ramfs_ops;
54 static const struct inode_operations ramfs_dir_inode_operations;
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,
63 struct inode *ramfs_get_inode(struct super_block *sb,
64 const struct inode *dir, umode_t mode, dev_t dev)
66 struct inode * inode = new_inode(sb);
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) {
77 init_special_inode(inode, mode, dev);
80 inode->i_op = &ramfs_file_inode_operations;
81 inode->i_fop = &ramfs_file_operations;
84 inode->i_op = &ramfs_dir_inode_operations;
85 inode->i_fop = &simple_dir_operations;
87 /* directory inodes start off with i_nlink == 2 (for "." entry) */
91 inode->i_op = &page_symlink_inode_operations;
92 inode_nohighmem(inode);
100 * File creation. Allocate an inode, and we're done..
104 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
106 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
110 d_instantiate(dentry, inode);
111 dget(dentry); /* Extra count - pin the dentry in core */
113 dir->i_mtime = dir->i_ctime = current_time(dir);
118 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
120 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
126 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
128 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
131 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
136 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
138 int l = strlen(symname)+1;
139 error = page_symlink(inode, symname, l);
141 d_instantiate(dentry, inode);
143 dir->i_mtime = dir->i_ctime = current_time(dir);
150 static const struct inode_operations ramfs_dir_inode_operations = {
151 .create = ramfs_create,
152 .lookup = simple_lookup,
154 .unlink = simple_unlink,
155 .symlink = ramfs_symlink,
156 .mkdir = ramfs_mkdir,
157 .rmdir = simple_rmdir,
158 .mknod = ramfs_mknod,
159 .rename = simple_rename,
163 * Display the mount options in /proc/mounts.
165 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
167 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
169 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
170 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
174 static const struct super_operations ramfs_ops = {
175 .statfs = simple_statfs,
176 .drop_inode = generic_delete_inode,
177 .show_options = ramfs_show_options,
184 static const struct fs_parameter_spec ramfs_param_specs[] = {
185 fsparam_u32oct("mode", Opt_mode),
189 const struct fs_parameter_description ramfs_fs_parameters = {
191 .specs = ramfs_param_specs,
194 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
196 struct fs_parse_result result;
197 struct ramfs_fs_info *fsi = fc->s_fs_info;
200 opt = fs_parse(fc, &ramfs_fs_parameters, param, &result);
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.
208 if (opt == -ENOPARAM)
215 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
222 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
224 struct ramfs_fs_info *fsi = sb->s_fs_info;
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;
234 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
235 sb->s_root = d_make_root(inode);
242 static int ramfs_get_tree(struct fs_context *fc)
244 return get_tree_nodev(fc, ramfs_fill_super);
247 static void ramfs_free_fc(struct fs_context *fc)
249 kfree(fc->s_fs_info);
252 static 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,
258 int ramfs_init_fs_context(struct fs_context *fc)
260 struct ramfs_fs_info *fsi;
262 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
266 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
268 fc->ops = &ramfs_context_ops;
272 static void ramfs_kill_sb(struct super_block *sb)
274 kfree(sb->s_fs_info);
275 kill_litter_super(sb);
278 static struct file_system_type ramfs_fs_type = {
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,
286 static int __init init_ramfs_fs(void)
288 return register_filesystem(&ramfs_fs_type);
290 fs_initcall(init_ramfs_fs);