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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#include <linux/fs.h>
27#include <linux/pagemap.h>
28#include <linux/highmem.h>
Andrew Morton8dde0502006-02-24 13:04:23 -080029#include <linux/time.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070030#include <linux/init.h>
31#include <linux/string.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070032#include <linux/backing-dev.h>
33#include <linux/ramfs.h>
Alexey Dobriyane8edc6e2007-05-21 01:22:52 +040034#include <linux/sched.h>
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -070035#include <linux/parser.h>
maximilian attemsa7e31082009-09-22 16:45:53 -070036#include <linux/magic.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090037#include <linux/slab.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#include <asm/uaccess.h>
David Howells642fb4d2006-01-06 00:11:41 -080039#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070040
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -070041#define RAMFS_DEFAULT_MODE 0755
42
Josef 'Jeff' Sipekee9b6d62007-02-12 00:55:41 -080043static const struct super_operations ramfs_ops;
Arjan van de Venc5ef1c42007-02-12 00:55:40 -080044static const struct inode_operations ramfs_dir_inode_operations;
Linus Torvalds1da177e2005-04-16 15:20:36 -070045
46static struct backing_dev_info ramfs_backing_dev_info = {
Jens Axboed9938312009-06-12 14:45:52 +020047 .name = "ramfs",
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 .ra_pages = 0, /* No readahead */
Miklos Szeredie4ad08f2008-04-30 00:54:37 -070049 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK |
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
51 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
52};
53
Dmitry Monakhov454abaf2010-03-04 17:32:18 +030054struct inode *ramfs_get_inode(struct super_block *sb,
Al Viro632861f2011-07-26 03:16:55 -040055 const struct inode *dir, umode_t mode, dev_t dev)
Linus Torvalds1da177e2005-04-16 15:20:36 -070056{
57 struct inode * inode = new_inode(sb);
58
59 if (inode) {
Christoph Hellwig85fe4022010-10-23 11:19:54 -040060 inode->i_ino = get_next_ino();
Dmitry Monakhov454abaf2010-03-04 17:32:18 +030061 inode_init_owner(inode, dir, mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 inode->i_mapping->a_ops = &ramfs_aops;
63 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
Mel Gorman769848c2007-07-17 04:03:05 -070064 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
Lee Schermerhornba9ddf42008-10-18 20:26:42 -070065 mapping_set_unevictable(inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 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) */
Dave Hansend8c76e62006-09-30 23:29:04 -070080 inc_nlink(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 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 */
94static int
Al Viro1a67aaf2011-07-26 01:52:52 -040095ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
Linus Torvalds1da177e2005-04-16 15:20:36 -070096{
Dmitry Monakhov454abaf2010-03-04 17:32:18 +030097 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 int error = -ENOSPC;
99
100 if (inode) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 d_instantiate(dentry, inode);
102 dget(dentry); /* Extra count - pin the dentry in core */
103 error = 0;
Andrew Morton8dde0502006-02-24 13:04:23 -0800104 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 }
106 return error;
107}
108
Al Viro18bb1db2011-07-26 01:41:39 -0400109static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110{
111 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
112 if (!retval)
Dave Hansend8c76e62006-09-30 23:29:04 -0700113 inc_nlink(dir);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 return retval;
115}
116
Al Viroebfc3b42012-06-10 18:05:36 -0400117static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118{
119 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
120}
121
122static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
123{
124 struct inode *inode;
125 int error = -ENOSPC;
126
Dmitry Monakhov454abaf2010-03-04 17:32:18 +0300127 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128 if (inode) {
129 int l = strlen(symname)+1;
130 error = page_symlink(inode, symname, l);
131 if (!error) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132 d_instantiate(dentry, inode);
133 dget(dentry);
Peter Staubachecbd3a62006-03-06 15:42:56 -0800134 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 } else
136 iput(inode);
137 }
138 return error;
139}
140
Arjan van de Venc5ef1c42007-02-12 00:55:40 -0800141static const struct inode_operations ramfs_dir_inode_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 .create = ramfs_create,
143 .lookup = simple_lookup,
144 .link = simple_link,
145 .unlink = simple_unlink,
146 .symlink = ramfs_symlink,
147 .mkdir = ramfs_mkdir,
148 .rmdir = simple_rmdir,
149 .mknod = ramfs_mknod,
150 .rename = simple_rename,
151};
152
Josef 'Jeff' Sipekee9b6d62007-02-12 00:55:41 -0800153static const struct super_operations ramfs_ops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 .statfs = simple_statfs,
155 .drop_inode = generic_delete_inode,
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700156 .show_options = generic_show_options,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157};
158
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700159struct ramfs_mount_opts {
160 umode_t mode;
161};
162
163enum {
164 Opt_mode,
165 Opt_err
166};
167
168static const match_table_t tokens = {
169 {Opt_mode, "mode=%o"},
170 {Opt_err, NULL}
171};
172
173struct ramfs_fs_info {
174 struct ramfs_mount_opts mount_opts;
175};
176
177static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
178{
179 substring_t args[MAX_OPT_ARGS];
180 int option;
181 int token;
182 char *p;
183
184 opts->mode = RAMFS_DEFAULT_MODE;
185
186 while ((p = strsep(&data, ",")) != NULL) {
187 if (!*p)
188 continue;
189
190 token = match_token(p, tokens, args);
191 switch (token) {
192 case Opt_mode:
193 if (match_octal(&args[0], &option))
194 return -EINVAL;
195 opts->mode = option & S_IALLUGO;
196 break;
Mike Frysinger0a8eba92009-06-14 22:56:48 +0100197 /*
198 * We might like to report bad mount options here;
199 * but traditionally ramfs has ignored all mount options,
200 * and as it is used as a !CONFIG_SHMEM simple substitute
201 * for tmpfs, better continue to ignore other mount options.
202 */
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700203 }
204 }
205
206 return 0;
207}
208
Peter Korsgaardda5e4ef2010-03-16 21:55:21 +0100209int ramfs_fill_super(struct super_block *sb, void *data, int silent)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210{
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700211 struct ramfs_fs_info *fsi;
Al Viro318ceed2012-02-12 22:08:01 -0500212 struct inode *inode;
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700213 int err;
214
215 save_mount_options(sb, data);
216
217 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
Ingo Molnarf8201ab2009-04-07 14:16:50 +0800218 sb->s_fs_info = fsi;
Al Viro318ceed2012-02-12 22:08:01 -0500219 if (!fsi)
220 return -ENOMEM;
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700221
222 err = ramfs_parse_options(data, &fsi->mount_opts);
223 if (err)
Al Viro318ceed2012-02-12 22:08:01 -0500224 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225
Ingo Molnarf8201ab2009-04-07 14:16:50 +0800226 sb->s_maxbytes = MAX_LFS_FILESIZE;
227 sb->s_blocksize = PAGE_CACHE_SIZE;
228 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
229 sb->s_magic = RAMFS_MAGIC;
230 sb->s_op = &ramfs_ops;
231 sb->s_time_gran = 1;
232
Dmitry Monakhov454abaf2010-03-04 17:32:18 +0300233 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
Al Viro48fde702012-01-08 22:15:13 -0500234 sb->s_root = d_make_root(inode);
Al Viro318ceed2012-02-12 22:08:01 -0500235 if (!sb->s_root)
236 return -ENOMEM;
Ingo Molnarf8201ab2009-04-07 14:16:50 +0800237
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238 return 0;
239}
240
Al Viro3c26ff62010-07-25 11:46:36 +0400241struct dentry *ramfs_mount(struct file_system_type *fs_type,
242 int flags, const char *dev_name, void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243{
Al Viro3c26ff62010-07-25 11:46:36 +0400244 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700245}
246
Al Viro3c26ff62010-07-25 11:46:36 +0400247static struct dentry *rootfs_mount(struct file_system_type *fs_type,
248 int flags, const char *dev_name, void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249{
Al Viro3c26ff62010-07-25 11:46:36 +0400250 return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251}
252
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700253static void ramfs_kill_sb(struct super_block *sb)
254{
255 kfree(sb->s_fs_info);
256 kill_litter_super(sb);
257}
258
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259static struct file_system_type ramfs_fs_type = {
260 .name = "ramfs",
Al Viro3c26ff62010-07-25 11:46:36 +0400261 .mount = ramfs_mount,
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700262 .kill_sb = ramfs_kill_sb,
Eric W. Biedermanb3c67612013-01-25 16:37:44 -0800263 .fs_flags = FS_USERNS_MOUNT,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700264};
265static struct file_system_type rootfs_fs_type = {
266 .name = "rootfs",
Al Viro3c26ff62010-07-25 11:46:36 +0400267 .mount = rootfs_mount,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268 .kill_sb = kill_litter_super,
269};
270
271static int __init init_ramfs_fs(void)
272{
273 return register_filesystem(&ramfs_fs_type);
274}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275module_init(init_ramfs_fs)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276
277int __init init_rootfs(void)
278{
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -0700279 int err;
280
281 err = bdi_init(&ramfs_backing_dev_info);
282 if (err)
283 return err;
284
285 err = register_filesystem(&rootfs_fs_type);
286 if (err)
287 bdi_destroy(&ramfs_backing_dev_info);
288
289 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290}