xref: /openbmc/linux/fs/ramfs/inode.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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 
41 static struct super_operations ramfs_ops;
42 static struct address_space_operations ramfs_aops;
43 static struct inode_operations ramfs_file_inode_operations;
44 static struct inode_operations ramfs_dir_inode_operations;
45 
46 static 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 
53 struct 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 */
93 static int
94 ramfs_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 
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 		dir->i_nlink++;
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 		} else
140 			iput(inode);
141 	}
142 	return error;
143 }
144 
145 static struct address_space_operations ramfs_aops = {
146 	.readpage	= simple_readpage,
147 	.prepare_write	= simple_prepare_write,
148 	.commit_write	= simple_commit_write
149 };
150 
151 struct 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 
160 static struct inode_operations ramfs_file_inode_operations = {
161 	.getattr	= simple_getattr,
162 };
163 
164 static 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 
176 static struct super_operations ramfs_ops = {
177 	.statfs		= simple_statfs,
178 	.drop_inode	= generic_delete_inode,
179 };
180 
181 static 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 
205 struct 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 
211 static 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 
217 static struct file_system_type ramfs_fs_type = {
218 	.name		= "ramfs",
219 	.get_sb		= ramfs_get_sb,
220 	.kill_sb	= kill_litter_super,
221 };
222 static struct file_system_type rootfs_fs_type = {
223 	.name		= "rootfs",
224 	.get_sb		= rootfs_get_sb,
225 	.kill_sb	= kill_litter_super,
226 };
227 
228 static int __init init_ramfs_fs(void)
229 {
230 	return register_filesystem(&ramfs_fs_type);
231 }
232 
233 static void __exit exit_ramfs_fs(void)
234 {
235 	unregister_filesystem(&ramfs_fs_type);
236 }
237 
238 module_init(init_ramfs_fs)
239 module_exit(exit_ramfs_fs)
240 
241 int __init init_rootfs(void)
242 {
243 	return register_filesystem(&rootfs_fs_type);
244 }
245 
246 MODULE_LICENSE("GPL");
247