xref: /openbmc/linux/fs/ramfs/inode.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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 <linux/parser.h>
37 #include <linux/magic.h>
38 #include <asm/uaccess.h>
39 #include "internal.h"
40 
41 #define RAMFS_DEFAULT_MODE	0755
42 
43 static const struct super_operations ramfs_ops;
44 static const struct inode_operations ramfs_dir_inode_operations;
45 
46 static struct backing_dev_info ramfs_backing_dev_info = {
47 	.name		= "ramfs",
48 	.ra_pages	= 0,	/* No readahead */
49 	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK |
50 			  BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
51 			  BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
52 };
53 
54 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
55 {
56 	struct inode * inode = new_inode(sb);
57 
58 	if (inode) {
59 		inode->i_mode = mode;
60 		inode->i_uid = current_fsuid();
61 		inode->i_gid = current_fsgid();
62 		inode->i_mapping->a_ops = &ramfs_aops;
63 		inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
64 		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
65 		mapping_set_unevictable(inode->i_mapping);
66 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
67 		switch (mode & S_IFMT) {
68 		default:
69 			init_special_inode(inode, mode, dev);
70 			break;
71 		case S_IFREG:
72 			inode->i_op = &ramfs_file_inode_operations;
73 			inode->i_fop = &ramfs_file_operations;
74 			break;
75 		case S_IFDIR:
76 			inode->i_op = &ramfs_dir_inode_operations;
77 			inode->i_fop = &simple_dir_operations;
78 
79 			/* directory inodes start off with i_nlink == 2 (for "." entry) */
80 			inc_nlink(inode);
81 			break;
82 		case S_IFLNK:
83 			inode->i_op = &page_symlink_inode_operations;
84 			break;
85 		}
86 	}
87 	return inode;
88 }
89 
90 /*
91  * File creation. Allocate an inode, and we're done..
92  */
93 /* SMP-safe */
94 static int
95 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
96 {
97 	struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
98 	int error = -ENOSPC;
99 
100 	if (inode) {
101 		if (dir->i_mode & S_ISGID) {
102 			inode->i_gid = dir->i_gid;
103 			if (S_ISDIR(mode))
104 				inode->i_mode |= S_ISGID;
105 		}
106 		d_instantiate(dentry, inode);
107 		dget(dentry);	/* Extra count - pin the dentry in core */
108 		error = 0;
109 		dir->i_mtime = dir->i_ctime = CURRENT_TIME;
110 	}
111 	return error;
112 }
113 
114 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
115 {
116 	int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
117 	if (!retval)
118 		inc_nlink(dir);
119 	return retval;
120 }
121 
122 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
123 {
124 	return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
125 }
126 
127 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
128 {
129 	struct inode *inode;
130 	int error = -ENOSPC;
131 
132 	inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
133 	if (inode) {
134 		int l = strlen(symname)+1;
135 		error = page_symlink(inode, symname, l);
136 		if (!error) {
137 			if (dir->i_mode & S_ISGID)
138 				inode->i_gid = dir->i_gid;
139 			d_instantiate(dentry, inode);
140 			dget(dentry);
141 			dir->i_mtime = dir->i_ctime = CURRENT_TIME;
142 		} else
143 			iput(inode);
144 	}
145 	return error;
146 }
147 
148 static const struct inode_operations ramfs_dir_inode_operations = {
149 	.create		= ramfs_create,
150 	.lookup		= simple_lookup,
151 	.link		= simple_link,
152 	.unlink		= simple_unlink,
153 	.symlink	= ramfs_symlink,
154 	.mkdir		= ramfs_mkdir,
155 	.rmdir		= simple_rmdir,
156 	.mknod		= ramfs_mknod,
157 	.rename		= simple_rename,
158 };
159 
160 static const struct super_operations ramfs_ops = {
161 	.statfs		= simple_statfs,
162 	.drop_inode	= generic_delete_inode,
163 	.show_options	= generic_show_options,
164 };
165 
166 struct ramfs_mount_opts {
167 	umode_t mode;
168 };
169 
170 enum {
171 	Opt_mode,
172 	Opt_err
173 };
174 
175 static const match_table_t tokens = {
176 	{Opt_mode, "mode=%o"},
177 	{Opt_err, NULL}
178 };
179 
180 struct ramfs_fs_info {
181 	struct ramfs_mount_opts mount_opts;
182 };
183 
184 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
185 {
186 	substring_t args[MAX_OPT_ARGS];
187 	int option;
188 	int token;
189 	char *p;
190 
191 	opts->mode = RAMFS_DEFAULT_MODE;
192 
193 	while ((p = strsep(&data, ",")) != NULL) {
194 		if (!*p)
195 			continue;
196 
197 		token = match_token(p, tokens, args);
198 		switch (token) {
199 		case Opt_mode:
200 			if (match_octal(&args[0], &option))
201 				return -EINVAL;
202 			opts->mode = option & S_IALLUGO;
203 			break;
204 		/*
205 		 * We might like to report bad mount options here;
206 		 * but traditionally ramfs has ignored all mount options,
207 		 * and as it is used as a !CONFIG_SHMEM simple substitute
208 		 * for tmpfs, better continue to ignore other mount options.
209 		 */
210 		}
211 	}
212 
213 	return 0;
214 }
215 
216 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
217 {
218 	struct ramfs_fs_info *fsi;
219 	struct inode *inode = NULL;
220 	struct dentry *root;
221 	int err;
222 
223 	save_mount_options(sb, data);
224 
225 	fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
226 	sb->s_fs_info = fsi;
227 	if (!fsi) {
228 		err = -ENOMEM;
229 		goto fail;
230 	}
231 
232 	err = ramfs_parse_options(data, &fsi->mount_opts);
233 	if (err)
234 		goto fail;
235 
236 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
237 	sb->s_blocksize		= PAGE_CACHE_SIZE;
238 	sb->s_blocksize_bits	= PAGE_CACHE_SHIFT;
239 	sb->s_magic		= RAMFS_MAGIC;
240 	sb->s_op		= &ramfs_ops;
241 	sb->s_time_gran		= 1;
242 
243 	inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0);
244 	if (!inode) {
245 		err = -ENOMEM;
246 		goto fail;
247 	}
248 
249 	root = d_alloc_root(inode);
250 	sb->s_root = root;
251 	if (!root) {
252 		err = -ENOMEM;
253 		goto fail;
254 	}
255 
256 	return 0;
257 fail:
258 	kfree(fsi);
259 	sb->s_fs_info = NULL;
260 	iput(inode);
261 	return err;
262 }
263 
264 int ramfs_get_sb(struct file_system_type *fs_type,
265 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
266 {
267 	return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
268 }
269 
270 static int rootfs_get_sb(struct file_system_type *fs_type,
271 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
272 {
273 	return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
274 			    mnt);
275 }
276 
277 static void ramfs_kill_sb(struct super_block *sb)
278 {
279 	kfree(sb->s_fs_info);
280 	kill_litter_super(sb);
281 }
282 
283 static struct file_system_type ramfs_fs_type = {
284 	.name		= "ramfs",
285 	.get_sb		= ramfs_get_sb,
286 	.kill_sb	= ramfs_kill_sb,
287 };
288 static struct file_system_type rootfs_fs_type = {
289 	.name		= "rootfs",
290 	.get_sb		= rootfs_get_sb,
291 	.kill_sb	= kill_litter_super,
292 };
293 
294 static int __init init_ramfs_fs(void)
295 {
296 	return register_filesystem(&ramfs_fs_type);
297 }
298 
299 static void __exit exit_ramfs_fs(void)
300 {
301 	unregister_filesystem(&ramfs_fs_type);
302 }
303 
304 module_init(init_ramfs_fs)
305 module_exit(exit_ramfs_fs)
306 
307 int __init init_rootfs(void)
308 {
309 	int err;
310 
311 	err = bdi_init(&ramfs_backing_dev_info);
312 	if (err)
313 		return err;
314 
315 	err = register_filesystem(&rootfs_fs_type);
316 	if (err)
317 		bdi_destroy(&ramfs_backing_dev_info);
318 
319 	return err;
320 }
321 
322 MODULE_LICENSE("GPL");
323