xref: /openbmc/linux/fs/ramfs/inode.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 
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 		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 */
91 static int
92 ramfs_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 
111 static 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 
119 static 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 
124 static 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 
145 static 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 
157 static const struct super_operations ramfs_ops = {
158 	.statfs		= simple_statfs,
159 	.drop_inode	= generic_delete_inode,
160 };
161 
162 static 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 
186 int 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 
192 static 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 
199 static struct file_system_type ramfs_fs_type = {
200 	.name		= "ramfs",
201 	.get_sb		= ramfs_get_sb,
202 	.kill_sb	= kill_litter_super,
203 };
204 static struct file_system_type rootfs_fs_type = {
205 	.name		= "rootfs",
206 	.get_sb		= rootfs_get_sb,
207 	.kill_sb	= kill_litter_super,
208 };
209 
210 static int __init init_ramfs_fs(void)
211 {
212 	return register_filesystem(&ramfs_fs_type);
213 }
214 
215 static void __exit exit_ramfs_fs(void)
216 {
217 	unregister_filesystem(&ramfs_fs_type);
218 }
219 
220 module_init(init_ramfs_fs)
221 module_exit(exit_ramfs_fs)
222 
223 int __init init_rootfs(void)
224 {
225 	return register_filesystem(&rootfs_fs_type);
226 }
227 
228 MODULE_LICENSE("GPL");
229