inode.c

  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/fs.h>
 27#include <linux/pagemap.h>
 28#include <linux/highmem.h>
 29#include <linux/time.h>
 30#include <linux/init.h>
 31#include <linux/string.h>
 32#include <linux/backing-dev.h>
 33#include <linux/ramfs.h>
 34#include <linux/sched.h>
 35#include <linux/parser.h>
 36#include <linux/magic.h>
 37#include <linux/slab.h>
 38#include <linux/uaccess.h>
 39#include <linux/fs_context.h>
 40#include <linux/fs_parser.h>
 41#include <linux/seq_file.h>
 42#include "internal.h"
 43
 44struct ramfs_mount_opts {
 45	umode_t mode;
 46};
 47
 48struct ramfs_fs_info {
 49	struct ramfs_mount_opts mount_opts;
 50};
 51
 52#define RAMFS_DEFAULT_MODE	0755
 53
 54static const struct super_operations ramfs_ops;
 55static const struct inode_operations ramfs_dir_inode_operations;
 56
 57struct inode *ramfs_get_inode(struct super_block *sb,
 58				const struct inode *dir, umode_t mode, dev_t dev)
 59{
 60	struct inode * inode = new_inode(sb);
 61
 62	if (inode) {
 63		inode->i_ino = get_next_ino();
 64		inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
 65		inode->i_mapping->a_ops = &ram_aops;
 66		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
 67		mapping_set_unevictable(inode->i_mapping);
 68		simple_inode_init_ts(inode);
 69		switch (mode & S_IFMT) {
 70		default:
 71			init_special_inode(inode, mode, dev);
 72			break;
 73		case S_IFREG:
 74			inode->i_op = &ramfs_file_inode_operations;
 75			inode->i_fop = &ramfs_file_operations;
 76			break;
 77		case S_IFDIR:
 78			inode->i_op = &ramfs_dir_inode_operations;
 79			inode->i_fop = &simple_dir_operations;
 80
 81			/* directory inodes start off with i_nlink == 2 (for "." entry) */
 82			inc_nlink(inode);
 83			break;
 84		case S_IFLNK:
 85			inode->i_op = &page_symlink_inode_operations;
 86			inode_nohighmem(inode);
 87			break;
 88		}
 89	}
 90	return inode;
 91}
 92
 93/*
 94 * File creation. Allocate an inode, and we're done..
 95 */
 96/* SMP-safe */
 97static int
 98ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
 99	    struct dentry *dentry, umode_t mode, dev_t dev)
100{
101	struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
102	int error = -ENOSPC;
103
104	if (inode) {
105		error = security_inode_init_security(inode, dir,
106						     &dentry->d_name, NULL,
107						     NULL);
108		if (error) {
109			iput(inode);
110			goto out;
111		}
112
113		d_make_persistent(dentry, inode);
114		error = 0;
115		inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
116	}
117out:
118	return error;
119}
120
121static struct dentry *ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
122				 struct dentry *dentry, umode_t mode)
123{
124	int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0);
125	if (!retval)
126		inc_nlink(dir);
127	return ERR_PTR(retval);
128}
129
130static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir,
131			struct dentry *dentry, umode_t mode, bool excl)
132{
133	return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
134}
135
136static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
137			 struct dentry *dentry, const char *symname)
138{
139	struct inode *inode;
140	int error = -ENOSPC;
141
142	inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
143	if (inode) {
144		int l = strlen(symname)+1;
145
146		error = security_inode_init_security(inode, dir,
147						     &dentry->d_name, NULL,
148						     NULL);
149		if (error) {
150			iput(inode);
151			goto out;
152		}
153
154		error = page_symlink(inode, symname, l);
155		if (!error) {
156			d_make_persistent(dentry, inode);
157			inode_set_mtime_to_ts(dir,
158					      inode_set_ctime_current(dir));
159		} else
160			iput(inode);
161	}
162out:
163	return error;
164}
165
166static int ramfs_tmpfile(struct mnt_idmap *idmap,
167			 struct inode *dir, struct file *file, umode_t mode)
168{
169	struct inode *inode;
170	int error;
171
172	inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
173	if (!inode)
174		return -ENOSPC;
175
176	error = security_inode_init_security(inode, dir,
177					     &file_dentry(file)->d_name, NULL,
178					     NULL);
179	if (error) {
180		iput(inode);
181		goto out;
182	}
183
184	d_tmpfile(file, inode);
185out:
186	return finish_open_simple(file, error);
187}
188
189static const struct inode_operations ramfs_dir_inode_operations = {
190	.create		= ramfs_create,
191	.lookup		= simple_lookup,
192	.link		= simple_link,
193	.unlink		= simple_unlink,
194	.symlink	= ramfs_symlink,
195	.mkdir		= ramfs_mkdir,
196	.rmdir		= simple_rmdir,
197	.mknod		= ramfs_mknod,
198	.rename		= simple_rename,
199	.tmpfile	= ramfs_tmpfile,
200};
201
202/*
203 * Display the mount options in /proc/mounts.
204 */
205static int ramfs_show_options(struct seq_file *m, struct dentry *root)
206{
207	struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
208
209	if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
210		seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
211	return 0;
212}
213
214static const struct super_operations ramfs_ops = {
215	.statfs		= simple_statfs,
216	.drop_inode	= inode_just_drop,
217	.show_options	= ramfs_show_options,
218};
219
220enum ramfs_param {
221	Opt_mode,
222};
223
224const struct fs_parameter_spec ramfs_fs_parameters[] = {
225	fsparam_u32oct("mode",	Opt_mode),
226	{}
227};
228
229static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
230{
231	struct fs_parse_result result;
232	struct ramfs_fs_info *fsi = fc->s_fs_info;
233	int opt;
234
235	opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
236	if (opt == -ENOPARAM) {
237		opt = vfs_parse_fs_param_source(fc, param);
238		if (opt != -ENOPARAM)
239			return opt;
240		/*
241		 * We might like to report bad mount options here;
242		 * but traditionally ramfs has ignored all mount options,
243		 * and as it is used as a !CONFIG_SHMEM simple substitute
244		 * for tmpfs, better continue to ignore other mount options.
245		 */
246		return 0;
247	}
248	if (opt < 0)
249		return opt;
250
251	switch (opt) {
252	case Opt_mode:
253		fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
254		break;
255	}
256
257	return 0;
258}
259
260static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
261{
262	struct ramfs_fs_info *fsi = sb->s_fs_info;
263	struct inode *inode;
264
265	sb->s_maxbytes		= MAX_LFS_FILESIZE;
266	sb->s_blocksize		= PAGE_SIZE;
267	sb->s_blocksize_bits	= PAGE_SHIFT;
268	sb->s_magic		= RAMFS_MAGIC;
269	sb->s_op		= &ramfs_ops;
270	sb->s_d_flags		= DCACHE_DONTCACHE;
271	sb->s_time_gran		= 1;
272
273	inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
274	sb->s_root = d_make_root(inode);
275	if (!sb->s_root)
276		return -ENOMEM;
277
278	return 0;
279}
280
281static int ramfs_get_tree(struct fs_context *fc)
282{
283	return get_tree_nodev(fc, ramfs_fill_super);
284}
285
286static void ramfs_free_fc(struct fs_context *fc)
287{
288	kfree(fc->s_fs_info);
289}
290
291static const struct fs_context_operations ramfs_context_ops = {
292	.free		= ramfs_free_fc,
293	.parse_param	= ramfs_parse_param,
294	.get_tree	= ramfs_get_tree,
295};
296
297int ramfs_init_fs_context(struct fs_context *fc)
298{
299	struct ramfs_fs_info *fsi;
300
301	fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
302	if (!fsi)
303		return -ENOMEM;
304
305	fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
306	fc->s_fs_info = fsi;
307	fc->ops = &ramfs_context_ops;
308	return 0;
309}
310
311void ramfs_kill_sb(struct super_block *sb)
312{
313	kfree(sb->s_fs_info);
314	kill_anon_super(sb);
315}
316
317static struct file_system_type ramfs_fs_type = {
318	.name		= "ramfs",
319	.init_fs_context = ramfs_init_fs_context,
320	.parameters	= ramfs_fs_parameters,
321	.kill_sb	= ramfs_kill_sb,
322	.fs_flags	= FS_USERNS_MOUNT,
323};
324
325static int __init init_ramfs_fs(void)
326{
327	return register_filesystem(&ramfs_fs_type);
328}
329fs_initcall(init_ramfs_fs);