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/module.h>
27#include <linux/fs.h>
28#include <linux/pagemap.h>
29#include <linux/highmem.h>
30#include <linux/time.h>
31#include <linux/init.h>
32#include <linux/string.h>
33#include <linux/backing-dev.h>
34#include <linux/ramfs.h>
35#include <linux/sched.h>
36#include <asm/uaccess.h>
37#include "internal.h"
38
39/* some random number */
40#define RAMFS_MAGIC	0x858458f6
41
42static const struct super_operations ramfs_ops;
43static const struct inode_operations ramfs_dir_inode_operations;
44
45static struct backing_dev_info ramfs_backing_dev_info = {
46	.ra_pages	= 0,	/* No readahead */
47	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK |
48			  BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
49			  BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
50};
51
52struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
53{
54	struct inode * inode = new_inode(sb);
55
56	if (inode) {
57		inode->i_mode = mode;
58		inode->i_uid = current->fsuid;
59		inode->i_gid = current->fsgid;
60		inode->i_blocks = 0;
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) {
65		default:
66			init_special_inode(inode, mode, dev);
67			break;
68		case S_IFREG:
69			inode->i_op = &ramfs_file_inode_operations;
70			inode->i_fop = &ramfs_file_operations;
71			break;
72		case S_IFDIR:
73			inode->i_op = &ramfs_dir_inode_operations;
74			inode->i_fop = &simple_dir_operations;
75
76			/* directory inodes start off with i_nlink == 2 (for "." entry) */
77			inc_nlink(inode);
78			break;
79		case S_IFLNK:
80			inode->i_op = &page_symlink_inode_operations;
81			break;
82		}
83	}
84	return inode;
85}
86
87/*
88 * File creation. Allocate an inode, and we're done..
89 */
90/* SMP-safe */
91static int
92ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
93{
94	struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
95	int error = -ENOSPC;
96
97	if (inode) {
98		if (dir->i_mode & S_ISGID) {
99			inode->i_gid = dir->i_gid;
100			if (S_ISDIR(mode))
101				inode->i_mode |= S_ISGID;
102		}
103		d_instantiate(dentry, inode);
104		dget(dentry);	/* Extra count - pin the dentry in core */
105		error = 0;
106		dir->i_mtime = dir->i_ctime = CURRENT_TIME;
107	}
108	return error;
109}
110
111static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
112{
113	int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
114	if (!retval)
115		inc_nlink(dir);
116	return retval;
117}
118
119static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
120{
121	return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
122}
123
124static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
125{
126	struct inode *inode;
127	int error = -ENOSPC;
128
129	inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
130	if (inode) {
131		int l = strlen(symname)+1;
132		error = page_symlink(inode, symname, l);
133		if (!error) {
134			if (dir->i_mode & S_ISGID)
135				inode->i_gid = dir->i_gid;
136			d_instantiate(dentry, inode);
137			dget(dentry);
138			dir->i_mtime = dir->i_ctime = CURRENT_TIME;
139		} else
140			iput(inode);
141	}
142	return error;
143}
144
145static const struct inode_operations ramfs_dir_inode_operations = {
146	.create		= ramfs_create,
147	.lookup		= simple_lookup,
148	.link		= simple_link,
149	.unlink		= simple_unlink,
150	.symlink	= ramfs_symlink,
151	.mkdir		= ramfs_mkdir,
152	.rmdir		= simple_rmdir,
153	.mknod		= ramfs_mknod,
154	.rename		= simple_rename,
155};
156
157static const struct super_operations ramfs_ops = {
158	.statfs		= simple_statfs,
159	.drop_inode	= generic_delete_inode,
160};
161
162static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
163{
164	struct inode * inode;
165	struct dentry * root;
166
167	sb->s_maxbytes = MAX_LFS_FILESIZE;
168	sb->s_blocksize = PAGE_CACHE_SIZE;
169	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
170	sb->s_magic = RAMFS_MAGIC;
171	sb->s_op = &ramfs_ops;
172	sb->s_time_gran = 1;
173	inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
174	if (!inode)
175		return -ENOMEM;
176
177	root = d_alloc_root(inode);
178	if (!root) {
179		iput(inode);
180		return -ENOMEM;
181	}
182	sb->s_root = root;
183	return 0;
184}
185
186int ramfs_get_sb(struct file_system_type *fs_type,
187	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
188{
189	return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
190}
191
192static int rootfs_get_sb(struct file_system_type *fs_type,
193	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
194{
195	return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
196			    mnt);
197}
198
199static struct file_system_type ramfs_fs_type = {
200	.name		= "ramfs",
201	.get_sb		= ramfs_get_sb,
202	.kill_sb	= kill_litter_super,
203};
204static struct file_system_type rootfs_fs_type = {
205	.name		= "rootfs",
206	.get_sb		= rootfs_get_sb,
207	.kill_sb	= kill_litter_super,
208};
209
210static int __init init_ramfs_fs(void)
211{
212	return register_filesystem(&ramfs_fs_type);
213}
214
215static void __exit exit_ramfs_fs(void)
216{
217	unregister_filesystem(&ramfs_fs_type);
218}
219
220module_init(init_ramfs_fs)
221module_exit(exit_ramfs_fs)
222
223int __init init_rootfs(void)
224{
225	return register_filesystem(&rootfs_fs_type);
226}
227
228MODULE_LICENSE("GPL");
229