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
42 static const struct super_operations ramfs_ops;
43 static const struct inode_operations ramfs_dir_inode_operations;
44
45 static 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
52 struct 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 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
64 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
65 switch (mode & S_IFMT) {
66 default:
67 init_special_inode(inode, mode, dev);
68 break;
69 case S_IFREG:
70 inode->i_op = &ramfs_file_inode_operations;
71 inode->i_fop = &ramfs_file_operations;
72 break;
73 case S_IFDIR:
74 inode->i_op = &ramfs_dir_inode_operations;
75 inode->i_fop = &simple_dir_operations;
76
77 /* directory inodes start off with i_nlink == 2 (for "." entry) */
78 inc_nlink(inode);
79 break;
80 case S_IFLNK:
81 inode->i_op = &page_symlink_inode_operations;
82 break;
83 }
84 }
85 return inode;
86 }
87
88 /*
89 * File creation. Allocate an inode, and we're done..
90 */
91 /* SMP-safe */
92 static int
93 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
94 {
95 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
96 int error = -ENOSPC;
97
98 if (inode) {
99 if (dir->i_mode & S_ISGID) {
100 inode->i_gid = dir->i_gid;
101 if (S_ISDIR(mode))
102 inode->i_mode |= S_ISGID;
103 }
104 d_instantiate(dentry, inode);
105 dget(dentry); /* Extra count - pin the dentry in core */
106 error = 0;
107 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
108 }
109 return error;
110 }
111
112 static 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 inc_nlink(dir);
117 return retval;
118 }
119
120 static 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
125 static 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 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
140 } else
141 iput(inode);
142 }
143 return error;
144 }
145
146 static const struct inode_operations ramfs_dir_inode_operations = {
147 .create = ramfs_create,
148 .lookup = simple_lookup,
149 .link = simple_link,
150 .unlink = simple_unlink,
151 .symlink = ramfs_symlink,
152 .mkdir = ramfs_mkdir,
153 .rmdir = simple_rmdir,
154 .mknod = ramfs_mknod,
155 .rename = simple_rename,
156 };
157
158 static const struct super_operations ramfs_ops = {
159 .statfs = simple_statfs,
160 .drop_inode = generic_delete_inode,
161 };
162
163 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
164 {
165 struct inode * inode;
166 struct dentry * root;
167
168 sb->s_maxbytes = MAX_LFS_FILESIZE;
169 sb->s_blocksize = PAGE_CACHE_SIZE;
170 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
171 sb->s_magic = RAMFS_MAGIC;
172 sb->s_op = &ramfs_ops;
173 sb->s_time_gran = 1;
174 inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
175 if (!inode)
176 return -ENOMEM;
177
178 root = d_alloc_root(inode);
179 if (!root) {
180 iput(inode);
181 return -ENOMEM;
182 }
183 sb->s_root = root;
184 return 0;
185 }
186
187 int ramfs_get_sb(struct file_system_type *fs_type,
188 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
189 {
190 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
191 }
192
193 static int rootfs_get_sb(struct file_system_type *fs_type,
194 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
195 {
196 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
197 mnt);
198 }
199
200 static struct file_system_type ramfs_fs_type = {
201 .name = "ramfs",
202 .get_sb = ramfs_get_sb,
203 .kill_sb = kill_litter_super,
204 };
205 static struct file_system_type rootfs_fs_type = {
206 .name = "rootfs",
207 .get_sb = rootfs_get_sb,
208 .kill_sb = kill_litter_super,
209 };
210
211 static int __init init_ramfs_fs(void)
212 {
213 return register_filesystem(&ramfs_fs_type);
214 }
215
216 static void __exit exit_ramfs_fs(void)
217 {
218 unregister_filesystem(&ramfs_fs_type);
219 }
220
221 module_init(init_ramfs_fs)
222 module_exit(exit_ramfs_fs)
223
224 int __init init_rootfs(void)
225 {
226 int err;
227
228 err = bdi_init(&ramfs_backing_dev_info);
229 if (err)
230 return err;
231
232 err = register_filesystem(&rootfs_fs_type);
233 if (err)
234 bdi_destroy(&ramfs_backing_dev_info);
235
236 return err;
237 }
238
239 MODULE_LICENSE("GPL");
240
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