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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
Axel Lin87e06aa2014-01-23 15:54:55 -080046static const struct address_space_operations ramfs_aops = {
47 .readpage = simple_readpage,
48 .write_begin = simple_write_begin,
49 .write_end = simple_write_end,
50 .set_page_dirty = __set_page_dirty_no_writeback,
51};
52
Dmitry Monakhov454abaf2010-03-04 17:32:18 +030053struct inode *ramfs_get_inode(struct super_block *sb,
Al Viro632861f2011-07-26 03:16:55 -040054 const struct inode *dir, umode_t mode, dev_t dev)
Linus Torvalds1da177e2005-04-16 15:20:36 -070055{
56 struct inode * inode = new_inode(sb);
57
58 if (inode) {
Christoph Hellwig85fe4022010-10-23 11:19:54 -040059 inode->i_ino = get_next_ino();
Dmitry Monakhov454abaf2010-03-04 17:32:18 +030060 inode_init_owner(inode, dir, mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 inode->i_mapping->a_ops = &ramfs_aops;
Mel Gorman769848c2007-07-17 04:03:05 -070062 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
Lee Schermerhornba9ddf42008-10-18 20:26:42 -070063 mapping_set_unevictable(inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
65 switch (mode & S_IFMT) {
66 default:
67 init_special_inode(inode, mode, dev);
68 break;
69 case S_IFREG:
70 inode->i_op = &ramfs_file_inode_operations;
71 inode->i_fop = &ramfs_file_operations;
72 break;
73 case S_IFDIR:
74 inode->i_op = &ramfs_dir_inode_operations;
75 inode->i_fop = &simple_dir_operations;
76
77 /* directory inodes start off with i_nlink == 2 (for "." entry) */
Dave Hansend8c76e62006-09-30 23:29:04 -070078 inc_nlink(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 break;
80 case S_IFLNK:
81 inode->i_op = &page_symlink_inode_operations;
Al Viro21fc61c2015-11-17 01:07:57 -050082 inode_nohighmem(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 break;
84 }
85 }
86 return inode;
87}
88
89/*
90 * File creation. Allocate an inode, and we're done..
91 */
92/* SMP-safe */
93static int
Al Viro1a67aaf2011-07-26 01:52:52 -040094ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
Linus Torvalds1da177e2005-04-16 15:20:36 -070095{
Dmitry Monakhov454abaf2010-03-04 17:32:18 +030096 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 int error = -ENOSPC;
98
99 if (inode) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 d_instantiate(dentry, inode);
101 dget(dentry); /* Extra count - pin the dentry in core */
102 error = 0;
Andrew Morton8dde0502006-02-24 13:04:23 -0800103 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 }
105 return error;
106}
107
Al Viro18bb1db2011-07-26 01:41:39 -0400108static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109{
110 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
111 if (!retval)
Dave Hansend8c76e62006-09-30 23:29:04 -0700112 inc_nlink(dir);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 return retval;
114}
115
Al Viroebfc3b42012-06-10 18:05:36 -0400116static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117{
118 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
119}
120
121static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
122{
123 struct inode *inode;
124 int error = -ENOSPC;
125
Dmitry Monakhov454abaf2010-03-04 17:32:18 +0300126 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127 if (inode) {
128 int l = strlen(symname)+1;
129 error = page_symlink(inode, symname, l);
130 if (!error) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 d_instantiate(dentry, inode);
132 dget(dentry);
Peter Staubachecbd3a62006-03-06 15:42:56 -0800133 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134 } else
135 iput(inode);
136 }
137 return error;
138}
139
Arjan van de Venc5ef1c42007-02-12 00:55:40 -0800140static const struct inode_operations ramfs_dir_inode_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 .create = ramfs_create,
142 .lookup = simple_lookup,
143 .link = simple_link,
144 .unlink = simple_unlink,
145 .symlink = ramfs_symlink,
146 .mkdir = ramfs_mkdir,
147 .rmdir = simple_rmdir,
148 .mknod = ramfs_mknod,
149 .rename = simple_rename,
150};
151
Josef 'Jeff' Sipekee9b6d62007-02-12 00:55:41 -0800152static const struct super_operations ramfs_ops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 .statfs = simple_statfs,
154 .drop_inode = generic_delete_inode,
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700155 .show_options = generic_show_options,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156};
157
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700158struct ramfs_mount_opts {
159 umode_t mode;
160};
161
162enum {
163 Opt_mode,
164 Opt_err
165};
166
167static const match_table_t tokens = {
168 {Opt_mode, "mode=%o"},
169 {Opt_err, NULL}
170};
171
172struct ramfs_fs_info {
173 struct ramfs_mount_opts mount_opts;
174};
175
176static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
177{
178 substring_t args[MAX_OPT_ARGS];
179 int option;
180 int token;
181 char *p;
182
183 opts->mode = RAMFS_DEFAULT_MODE;
184
185 while ((p = strsep(&data, ",")) != NULL) {
186 if (!*p)
187 continue;
188
189 token = match_token(p, tokens, args);
190 switch (token) {
191 case Opt_mode:
192 if (match_octal(&args[0], &option))
193 return -EINVAL;
194 opts->mode = option & S_IALLUGO;
195 break;
Mike Frysinger0a8eba92009-06-14 22:56:48 +0100196 /*
197 * We might like to report bad mount options here;
198 * but traditionally ramfs has ignored all mount options,
199 * and as it is used as a !CONFIG_SHMEM simple substitute
200 * for tmpfs, better continue to ignore other mount options.
201 */
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700202 }
203 }
204
205 return 0;
206}
207
Peter Korsgaardda5e4ef2010-03-16 21:55:21 +0100208int ramfs_fill_super(struct super_block *sb, void *data, int silent)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209{
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700210 struct ramfs_fs_info *fsi;
Al Viro318ceed2012-02-12 22:08:01 -0500211 struct inode *inode;
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700212 int err;
213
214 save_mount_options(sb, data);
215
216 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
Ingo Molnarf8201ab2009-04-07 14:16:50 +0800217 sb->s_fs_info = fsi;
Al Viro318ceed2012-02-12 22:08:01 -0500218 if (!fsi)
219 return -ENOMEM;
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700220
221 err = ramfs_parse_options(data, &fsi->mount_opts);
222 if (err)
Al Viro318ceed2012-02-12 22:08:01 -0500223 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700224
Ingo Molnarf8201ab2009-04-07 14:16:50 +0800225 sb->s_maxbytes = MAX_LFS_FILESIZE;
226 sb->s_blocksize = PAGE_CACHE_SIZE;
227 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
228 sb->s_magic = RAMFS_MAGIC;
229 sb->s_op = &ramfs_ops;
230 sb->s_time_gran = 1;
231
Dmitry Monakhov454abaf2010-03-04 17:32:18 +0300232 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
Al Viro48fde702012-01-08 22:15:13 -0500233 sb->s_root = d_make_root(inode);
Al Viro318ceed2012-02-12 22:08:01 -0500234 if (!sb->s_root)
235 return -ENOMEM;
Ingo Molnarf8201ab2009-04-07 14:16:50 +0800236
Linus Torvalds1da177e2005-04-16 15:20:36 -0700237 return 0;
238}
239
Al Viro3c26ff62010-07-25 11:46:36 +0400240struct dentry *ramfs_mount(struct file_system_type *fs_type,
241 int flags, const char *dev_name, void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242{
Al Viro3c26ff62010-07-25 11:46:36 +0400243 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244}
245
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700246static void ramfs_kill_sb(struct super_block *sb)
247{
248 kfree(sb->s_fs_info);
249 kill_litter_super(sb);
250}
251
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252static struct file_system_type ramfs_fs_type = {
253 .name = "ramfs",
Al Viro3c26ff62010-07-25 11:46:36 +0400254 .mount = ramfs_mount,
Wu Fengguangc3b1b1c2009-03-31 15:24:34 -0700255 .kill_sb = ramfs_kill_sb,
Eric W. Biedermanb3c67612013-01-25 16:37:44 -0800256 .fs_flags = FS_USERNS_MOUNT,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258
Rob Landley57f150a2013-09-11 14:26:10 -0700259int __init init_ramfs_fs(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260{
Rob Landley4bbee762013-09-11 14:26:08 -0700261 static unsigned long once;
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -0700262
Rob Landley4bbee762013-09-11 14:26:08 -0700263 if (test_and_set_bit(0, &once))
264 return 0;
Christoph Hellwigb4caecd2015-01-14 10:42:32 +0100265 return register_filesystem(&ramfs_fs_type);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266}
Paul Gortmakeraf52b042014-01-21 15:48:46 -0800267fs_initcall(init_ramfs_fs);