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>
41 struct ramfs_mount_opts {
45 struct ramfs_fs_info {
46 struct ramfs_mount_opts mount_opts;
49 #define RAMFS_DEFAULT_MODE 0755
51 static const struct super_operations ramfs_ops;
52 static const struct inode_operations ramfs_dir_inode_operations;
54 static const struct address_space_operations ramfs_aops = {
55 .readpage = simple_readpage,
56 .write_begin = simple_write_begin,
57 .write_end = simple_write_end,
58 .set_page_dirty = __set_page_dirty_no_writeback,
61 struct inode *ramfs_get_inode(struct super_block *sb,
62 const struct inode *dir, umode_t mode, dev_t dev)
64 struct inode * inode = new_inode(sb);
67 inode->i_ino = get_next_ino();
68 inode_init_owner(inode, dir, mode);
69 inode->i_mapping->a_ops = &ramfs_aops;
70 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
71 mapping_set_unevictable(inode->i_mapping);
72 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
73 switch (mode & S_IFMT) {
75 init_special_inode(inode, mode, dev);
78 inode->i_op = &ramfs_file_inode_operations;
79 inode->i_fop = &ramfs_file_operations;
82 inode->i_op = &ramfs_dir_inode_operations;
83 inode->i_fop = &simple_dir_operations;
85 /* directory inodes start off with i_nlink == 2 (for "." entry) */
89 inode->i_op = &page_symlink_inode_operations;
90 inode_nohighmem(inode);
98 * File creation. Allocate an inode, and we're done..
102 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
104 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
108 d_instantiate(dentry, inode);
109 dget(dentry); /* Extra count - pin the dentry in core */
111 dir->i_mtime = dir->i_ctime = current_time(dir);
116 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
118 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
124 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
126 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
129 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
134 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
136 int l = strlen(symname)+1;
137 error = page_symlink(inode, symname, l);
139 d_instantiate(dentry, inode);
141 dir->i_mtime = dir->i_ctime = current_time(dir);
148 static const struct inode_operations ramfs_dir_inode_operations = {
149 .create = ramfs_create,
150 .lookup = simple_lookup,
152 .unlink = simple_unlink,
153 .symlink = ramfs_symlink,
154 .mkdir = ramfs_mkdir,
155 .rmdir = simple_rmdir,
156 .mknod = ramfs_mknod,
157 .rename = simple_rename,
161 * Display the mount options in /proc/mounts.
163 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
165 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
167 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
168 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
172 static const struct super_operations ramfs_ops = {
173 .statfs = simple_statfs,
174 .drop_inode = generic_delete_inode,
175 .show_options = ramfs_show_options,
183 static const match_table_t tokens = {
184 {Opt_mode, "mode=%o"},
188 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
190 substring_t args[MAX_OPT_ARGS];
195 opts->mode = RAMFS_DEFAULT_MODE;
197 while ((p = strsep(&data, ",")) != NULL) {
201 token = match_token(p, tokens, args);
204 if (match_octal(&args[0], &option))
206 opts->mode = option & S_IALLUGO;
209 * We might like to report bad mount options here;
210 * but traditionally ramfs has ignored all mount options,
211 * and as it is used as a !CONFIG_SHMEM simple substitute
212 * for tmpfs, better continue to ignore other mount options.
220 static int ramfs_fill_super(struct super_block *sb, void *data, int silent)
222 struct ramfs_fs_info *fsi;
226 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
231 err = ramfs_parse_options(data, &fsi->mount_opts);
235 sb->s_maxbytes = MAX_LFS_FILESIZE;
236 sb->s_blocksize = PAGE_SIZE;
237 sb->s_blocksize_bits = PAGE_SHIFT;
238 sb->s_magic = RAMFS_MAGIC;
239 sb->s_op = &ramfs_ops;
242 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
243 sb->s_root = d_make_root(inode);
250 struct dentry *ramfs_mount(struct file_system_type *fs_type,
251 int flags, const char *dev_name, void *data)
253 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
256 static void ramfs_kill_sb(struct super_block *sb)
258 kfree(sb->s_fs_info);
259 kill_litter_super(sb);
262 static struct file_system_type ramfs_fs_type = {
264 .mount = ramfs_mount,
265 .kill_sb = ramfs_kill_sb,
266 .fs_flags = FS_USERNS_MOUNT,
269 static int __init init_ramfs_fs(void)
271 return register_filesystem(&ramfs_fs_type);
273 fs_initcall(init_ramfs_fs);