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.
26 #include <linux/module.h>
28 #include <linux/pagemap.h>
29 #include <linux/highmem.h>
30 #include <linux/init.h>
31 #include <linux/string.h>
32 #include <linux/smp_lock.h>
33 #include <linux/backing-dev.h>
35 #include <asm/uaccess.h>
37 /* some random number */
38 #define RAMFS_MAGIC 0x858458f6
40 static struct super_operations ramfs_ops;
41 static struct address_space_operations ramfs_aops;
42 static struct file_operations ramfs_file_operations;
43 static struct inode_operations ramfs_file_inode_operations;
44 static struct inode_operations ramfs_dir_inode_operations;
46 static struct backing_dev_info ramfs_backing_dev_info = {
47 .ra_pages = 0, /* No readahead */
48 .memory_backed = 1, /* Does not contribute to dirty memory */
51 static struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
53 struct inode * inode = new_inode(sb);
57 inode->i_uid = current->fsuid;
58 inode->i_gid = current->fsgid;
59 inode->i_blksize = PAGE_CACHE_SIZE;
61 inode->i_mapping->a_ops = &ramfs_aops;
62 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
63 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
64 switch (mode & S_IFMT) {
66 init_special_inode(inode, mode, dev);
69 inode->i_op = &ramfs_file_inode_operations;
70 inode->i_fop = &ramfs_file_operations;
73 inode->i_op = &ramfs_dir_inode_operations;
74 inode->i_fop = &simple_dir_operations;
76 /* directory inodes start off with i_nlink == 2 (for "." entry) */
80 inode->i_op = &page_symlink_inode_operations;
88 * File creation. Allocate an inode, and we're done..
92 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
94 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
98 if (dir->i_mode & S_ISGID) {
99 inode->i_gid = dir->i_gid;
101 inode->i_mode |= S_ISGID;
103 d_instantiate(dentry, inode);
104 dget(dentry); /* Extra count - pin the dentry in core */
110 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
112 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
118 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
120 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
123 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
128 inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
130 int l = strlen(symname)+1;
131 error = page_symlink(inode, symname, l);
133 if (dir->i_mode & S_ISGID)
134 inode->i_gid = dir->i_gid;
135 d_instantiate(dentry, inode);
143 static struct address_space_operations ramfs_aops = {
144 .readpage = simple_readpage,
145 .prepare_write = simple_prepare_write,
146 .commit_write = simple_commit_write
149 static struct file_operations ramfs_file_operations = {
150 .read = generic_file_read,
151 .write = generic_file_write,
152 .mmap = generic_file_mmap,
153 .fsync = simple_sync_file,
154 .sendfile = generic_file_sendfile,
155 .llseek = generic_file_llseek,
158 static struct inode_operations ramfs_file_inode_operations = {
159 .getattr = simple_getattr,
162 static struct inode_operations ramfs_dir_inode_operations = {
163 .create = ramfs_create,
164 .lookup = simple_lookup,
166 .unlink = simple_unlink,
167 .symlink = ramfs_symlink,
168 .mkdir = ramfs_mkdir,
169 .rmdir = simple_rmdir,
170 .mknod = ramfs_mknod,
171 .rename = simple_rename,
174 static struct super_operations ramfs_ops = {
175 .statfs = simple_statfs,
176 .drop_inode = generic_delete_inode,
179 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
181 struct inode * inode;
182 struct dentry * root;
184 sb->s_maxbytes = MAX_LFS_FILESIZE;
185 sb->s_blocksize = PAGE_CACHE_SIZE;
186 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
187 sb->s_magic = RAMFS_MAGIC;
188 sb->s_op = &ramfs_ops;
189 inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
193 root = d_alloc_root(inode);
202 static struct super_block *ramfs_get_sb(struct file_system_type *fs_type,
203 int flags, const char *dev_name, void *data)
205 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super);
208 static struct super_block *rootfs_get_sb(struct file_system_type *fs_type,
209 int flags, const char *dev_name, void *data)
211 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
214 static struct file_system_type ramfs_fs_type = {
216 .get_sb = ramfs_get_sb,
217 .kill_sb = kill_litter_super,
219 static struct file_system_type rootfs_fs_type = {
221 .get_sb = rootfs_get_sb,
222 .kill_sb = kill_litter_super,
225 static int __init init_ramfs_fs(void)
227 return register_filesystem(&ramfs_fs_type);
230 static void __exit exit_ramfs_fs(void)
232 unregister_filesystem(&ramfs_fs_type);
235 module_init(init_ramfs_fs)
236 module_exit(exit_ramfs_fs)
238 int __init init_rootfs(void)
240 return register_filesystem(&rootfs_fs_type);
243 MODULE_LICENSE("GPL");