summaryrefslogtreecommitdiffstats
path: root/fs/ramfs/inode.c
blob: 65e7e56005b8f565f272a53d379d5b87065af3a4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
/*
 * Resizable simple ram filesystem for Linux.
 *
 * Copyright (C) 2000 Linus Torvalds.
 *               2000 Transmeta Corp.
 *
 * Usage limits added by David Gibson, Linuxcare Australia.
 * This file is released under the GPL.
 */

/*
 * NOTE! This filesystem is probably most useful
 * not as a real filesystem, but as an example of
 * how virtual filesystems can be written.
 *
 * It doesn't get much simpler than this. Consider
 * that this file implements the full semantics of
 * a POSIX-compliant read-write filesystem.
 *
 * Note in particular how the filesystem does not
 * need to implement any data structures of its own
 * to keep track of the virtual data: using the VFS
 * caches is sufficient.
 */

#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/ramfs.h>
#include <linux/sched.h>
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include "internal.h"

struct ramfs_mount_opts {
	umode_t mode;
};

struct ramfs_fs_info {
	struct ramfs_mount_opts mount_opts;
};

#define RAMFS_DEFAULT_MODE	0755

static const struct super_operations ramfs_ops;
static const struct inode_operations ramfs_dir_inode_operations;

struct inode *ramfs_get_inode(struct super_block *sb,
				const struct inode *dir, umode_t mode, dev_t dev)
{
	struct inode * inode = new_inode(sb);

	if (inode) {
		inode->i_ino = get_next_ino();
		inode_init_owner(&init_user_ns, inode, dir, mode);
		inode->i_mapping->a_ops = &ram_aops;
		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
		mapping_set_unevictable(inode->i_mapping);
		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
		switch (mode & S_IFMT) {
		default:
			init_special_inode(inode, mode, dev);
			break;
		case S_IFREG:
			inode->i_op = &ramfs_file_inode_operations;
			inode->i_fop = &ramfs_file_operations;
			break;
		case S_IFDIR:
			inode->i_op = &ramfs_dir_inode_operations;
			inode->i_fop = &simple_dir_operations;

			/* directory inodes start off with i_nlink == 2 (for "." entry) */
			inc_nlink(inode);
			break;
		case S_IFLNK:
			inode->i_op = &page_symlink_inode_operations;
			inode_nohighmem(inode);
			break;
		}
	}
	return inode;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
/* SMP-safe */
static int
ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
	    struct dentry *dentry, umode_t mode, dev_t dev)
{
	struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
	int error = -ENOSPC;

	if (inode) {
		d_instantiate(dentry, inode);
		dget(dentry);	/* Extra count - pin the dentry in core */
		error = 0;
		dir->i_mtime = dir->i_ctime = current_time(dir);
	}
	return error;
}

static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
		       struct dentry *dentry, umode_t mode)
{
	int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0);
	if (!retval)
		inc_nlink(dir);
	return retval;
}

static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir,
			struct dentry *dentry, umode_t mode, bool excl)
{
	return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
}

static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
			 struct dentry *dentry, const char *symname)
{
	struct inode *inode;
	int error = -ENOSPC;

	inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
	if (inode) {
		int l = strlen(symname)+1;
		error = page_symlink(inode, symname, l);
		if (!error) {
			d_instantiate(dentry, inode);
			dget(dentry);
			dir->i_mtime = dir->i_ctime = current_time(dir);
		} else
			iput(inode);
	}
	return error;
}

static int ramfs_tmpfile(struct user_namespace *mnt_userns,
			 struct inode *dir, struct dentry *dentry, umode_t mode)
{
	struct inode *inode;

	inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
	if (!inode)
		return -ENOSPC;
	d_tmpfile(dentry, inode);
	return 0;
}

static const struct inode_operations ramfs_dir_inode_operations = {
	.create		= ramfs_create,
	.lookup		= simple_lookup,
	.link		= simple_link,
	.unlink		= simple_unlink,
	.symlink	= ramfs_symlink,
	.mkdir		= ramfs_mkdir,
	.rmdir		= simple_rmdir,
	.mknod		= ramfs_mknod,
	.rename		= simple_rename,
	.tmpfile	= ramfs_tmpfile,
};

/*
 * Display the mount options in /proc/mounts.
 */
static int ramfs_show_options(struct seq_file *m, struct dentry *root)
{
	struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;

	if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
		seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
	return 0;
}

static const struct super_operations ramfs_ops = {
	.statfs		= simple_statfs,
	.drop_inode	= generic_delete_inode,
	.show_options	= ramfs_show_options,
};

enum ramfs_param {
	Opt_mode,
};

const struct fs_parameter_spec ramfs_fs_parameters[] = {
	fsparam_u32oct("mode",	Opt_mode),
	{}
};

static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
	struct fs_parse_result result;
	struct ramfs_fs_info *fsi = fc->s_fs_info;
	int opt;

	opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
	if (opt < 0) {
		/*
		 * We might like to report bad mount options here;
		 * but traditionally ramfs has ignored all mount options,
		 * and as it is used as a !CONFIG_SHMEM simple substitute
		 * for tmpfs, better continue to ignore other mount options.
		 */
		if (opt == -ENOPARAM)
			opt = 0;
		return opt;
	}

	switch (opt) {
	case Opt_mode:
		fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
		break;
	}

	return 0;
}

static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
	struct ramfs_fs_info *fsi = sb->s_fs_info;
	struct inode *inode;

	sb->s_maxbytes		= MAX_LFS_FILESIZE;
	sb->s_blocksize		= PAGE_SIZE;
	sb->s_blocksize_bits	= PAGE_SHIFT;
	sb->s_magic		= RAMFS_MAGIC;
	sb->s_op		= &ramfs_ops;
	sb->s_time_gran		= 1;

	inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
		return -ENOMEM;

	return 0;
}

static int ramfs_get_tree(struct fs_context *fc)
{
	return get_tree_nodev(fc, ramfs_fill_super);
}

static void ramfs_free_fc(struct fs_context *fc)
{
	kfree(fc->s_fs_info);
}

static const struct fs_context_operations ramfs_context_ops = {
	.free		= ramfs_free_fc,
	.parse_param	= ramfs_parse_param,
	.get_tree	= ramfs_get_tree,
};

int ramfs_init_fs_context(struct fs_context *fc)
{
	struct ramfs_fs_info *fsi;

	fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
	if (!fsi)
		return -ENOMEM;

	fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
	fc->s_fs_info = fsi;
	fc->ops = &ramfs_context_ops;
	return 0;
}

static void ramfs_kill_sb(struct super_block *sb)
{
	kfree(sb->s_fs_info);
	kill_litter_super(sb);
}

static struct file_system_type ramfs_fs_type = {
	.name		= "ramfs",
	.init_fs_context = ramfs_init_fs_context,
	.parameters	= ramfs_fs_parameters,
	.kill_sb	= ramfs_kill_sb,
	.fs_flags	= FS_USERNS_MOUNT,
};

static int __init init_ramfs_fs(void)
{
	return register_filesystem(&ramfs_fs_type);
}
fs_initcall(init_ramfs_fs);