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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
Andrew Morton8dde0502006-02-24 13:04:23 -080030#include <linux/time.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070031#include <linux/init.h>
32#include <linux/string.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033#include <linux/backing-dev.h>
34#include <linux/ramfs.h>
35
36#include <asm/uaccess.h>
David Howells642fb4d2006-01-06 00:11:41 -080037#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070038
39/* some random number */
40#define RAMFS_MAGIC 0x858458f6
41
Josef 'Jeff' Sipekee9b6d62007-02-12 00:55:41 -080042static const struct super_operations ramfs_ops;
Arjan van de Venc5ef1c42007-02-12 00:55:40 -080043static const struct inode_operations ramfs_dir_inode_operations;
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
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;
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 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) */
Dave Hansend8c76e62006-09-30 23:29:04 -070077 inc_nlink(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 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;
Andrew Morton8dde0502006-02-24 13:04:23 -0800106 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 }
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)
Dave Hansend8c76e62006-09-30 23:29:04 -0700115 inc_nlink(dir);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116 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);
Peter Staubachecbd3a62006-03-06 15:42:56 -0800138 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139 } else
140 iput(inode);
141 }
142 return error;
143}
144
Arjan van de Venc5ef1c42007-02-12 00:55:40 -0800145static const struct inode_operations ramfs_dir_inode_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146 .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
Josef 'Jeff' Sipekee9b6d62007-02-12 00:55:41 -0800157static const struct super_operations ramfs_ops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 .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
David Howells454e2392006-06-23 02:02:57 -0700186int ramfs_get_sb(struct file_system_type *fs_type,
187 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188{
David Howells454e2392006-06-23 02:02:57 -0700189 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190}
191
David Howells454e2392006-06-23 02:02:57 -0700192static int rootfs_get_sb(struct file_system_type *fs_type,
193 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194{
David Howells454e2392006-06-23 02:02:57 -0700195 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
196 mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197}
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");