tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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/init.h>
31#include <linux/string.h>
32#include <linux/smp_lock.h>
33#include <linux/backing-dev.h>
34#include <linux/ramfs.h>
35
36#include <asm/uaccess.h>
37
38/* some random number */
39#define RAMFS_MAGIC 0x858458f6
40
41static struct super_operations ramfs_ops;
42static struct address_space_operations ramfs_aops;
43static struct inode_operations ramfs_file_inode_operations;
44static struct inode_operations ramfs_dir_inode_operations;
45
46static struct backing_dev_info ramfs_backing_dev_info = {
47 .ra_pages = 0, /* No readahead */
48 .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK |
49 BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
50 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
51};
52
53struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
54{
55 struct inode * inode = new_inode(sb);
56
57 if (inode) {
58 inode->i_mode = mode;
59 inode->i_uid = current->fsuid;
60 inode->i_gid = current->fsgid;
61 inode->i_blksize = PAGE_CACHE_SIZE;
62 inode->i_blocks = 0;
63 inode->i_mapping->a_ops = &ramfs_aops;
64 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
65 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
66 switch (mode & S_IFMT) {
67 default:
68 init_special_inode(inode, mode, dev);
69 break;
70 case S_IFREG:
71 inode->i_op = &ramfs_file_inode_operations;
72 inode->i_fop = &ramfs_file_operations;
73 break;
74 case S_IFDIR:
75 inode->i_op = &ramfs_dir_inode_operations;
76 inode->i_fop = &simple_dir_operations;
77
78 /* directory inodes start off with i_nlink == 2 (for "." entry) */
79 inode->i_nlink++;
80 break;
81 case S_IFLNK:
82 inode->i_op = &page_symlink_inode_operations;
83 break;
84 }
85 }
86 return inode;
87}
88
89/*
90 * File creation. Allocate an inode, and we're done..
91 */
92/* SMP-safe */
93static int
94ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
95{
96 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
97 int error = -ENOSPC;
98
99 if (inode) {
100 if (dir->i_mode & S_ISGID) {
101 inode->i_gid = dir->i_gid;
102 if (S_ISDIR(mode))
103 inode->i_mode |= S_ISGID;
104 }
105 d_instantiate(dentry, inode);
106 dget(dentry); /* Extra count - pin the dentry in core */
107 error = 0;
108 }
109 return error;
110}
111
112static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
113{
114 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
115 if (!retval)
116 dir->i_nlink++;
117 return retval;
118}
119
120static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
121{
122 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
123}
124
125static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
126{
127 struct inode *inode;
128 int error = -ENOSPC;
129
130 inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
131 if (inode) {
132 int l = strlen(symname)+1;
133 error = page_symlink(inode, symname, l);
134 if (!error) {
135 if (dir->i_mode & S_ISGID)
136 inode->i_gid = dir->i_gid;
137 d_instantiate(dentry, inode);
138 dget(dentry);
139 } else
140 iput(inode);
141 }
142 return error;
143}
144
145static struct address_space_operations ramfs_aops = {
146 .readpage = simple_readpage,
147 .prepare_write = simple_prepare_write,
148 .commit_write = simple_commit_write
149};
150
151struct file_operations ramfs_file_operations = {
152 .read = generic_file_read,
153 .write = generic_file_write,
154 .mmap = generic_file_mmap,
155 .fsync = simple_sync_file,
156 .sendfile = generic_file_sendfile,
157 .llseek = generic_file_llseek,
158};
159
160static struct inode_operations ramfs_file_inode_operations = {
161 .getattr = simple_getattr,
162};
163
164static struct inode_operations ramfs_dir_inode_operations = {
165 .create = ramfs_create,
166 .lookup = simple_lookup,
167 .link = simple_link,
168 .unlink = simple_unlink,
169 .symlink = ramfs_symlink,
170 .mkdir = ramfs_mkdir,
171 .rmdir = simple_rmdir,
172 .mknod = ramfs_mknod,
173 .rename = simple_rename,
174};
175
176static struct super_operations ramfs_ops = {
177 .statfs = simple_statfs,
178 .drop_inode = generic_delete_inode,
179};
180
181static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
182{
183 struct inode * inode;
184 struct dentry * root;
185
186 sb->s_maxbytes = MAX_LFS_FILESIZE;
187 sb->s_blocksize = PAGE_CACHE_SIZE;
188 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
189 sb->s_magic = RAMFS_MAGIC;
190 sb->s_op = &ramfs_ops;
191 sb->s_time_gran = 1;
192 inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
193 if (!inode)
194 return -ENOMEM;
195
196 root = d_alloc_root(inode);
197 if (!root) {
198 iput(inode);
199 return -ENOMEM;
200 }
201 sb->s_root = root;
202 return 0;
203}
204
205struct super_block *ramfs_get_sb(struct file_system_type *fs_type,
206 int flags, const char *dev_name, void *data)
207{
208 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super);
209}
210
211static struct super_block *rootfs_get_sb(struct file_system_type *fs_type,
212 int flags, const char *dev_name, void *data)
213{
214 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
215}
216
217static struct file_system_type ramfs_fs_type = {
218 .name = "ramfs",
219 .get_sb = ramfs_get_sb,
220 .kill_sb = kill_litter_super,
221};
222static struct file_system_type rootfs_fs_type = {
223 .name = "rootfs",
224 .get_sb = rootfs_get_sb,
225 .kill_sb = kill_litter_super,
226};
227
228static int __init init_ramfs_fs(void)
229{
230 return register_filesystem(&ramfs_fs_type);
231}
232
233static void __exit exit_ramfs_fs(void)
234{
235 unregister_filesystem(&ramfs_fs_type);
236}
237
238module_init(init_ramfs_fs)
239module_exit(exit_ramfs_fs)
240
241int __init init_rootfs(void)
242{
243 return register_filesystem(&rootfs_fs_type);
244}
245
246MODULE_LICENSE("GPL");