2 * Resizable simple ram filesystem for Linux.
4 * Copyright (C) 2000 Linus Torvalds.
7 * Usage limits added by David Gibson, Linuxcare Australia.
8 * This file is released under the GPL.
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.
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.
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.
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 <asm/uaccess.h>
41 #define RAMFS_DEFAULT_MODE 0755
43 static const struct super_operations ramfs_ops;
44 static const struct inode_operations ramfs_dir_inode_operations;
46 static 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,
53 struct inode *ramfs_get_inode(struct super_block *sb,
54 const struct inode *dir, umode_t mode, dev_t dev)
56 struct inode * inode = new_inode(sb);
59 inode->i_ino = get_next_ino();
60 inode_init_owner(inode, dir, mode);
61 inode->i_mapping->a_ops = &ramfs_aops;
62 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
63 mapping_set_unevictable(inode->i_mapping);
64 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
65 switch (mode & S_IFMT) {
67 init_special_inode(inode, mode, dev);
70 inode->i_op = &ramfs_file_inode_operations;
71 inode->i_fop = &ramfs_file_operations;
74 inode->i_op = &ramfs_dir_inode_operations;
75 inode->i_fop = &simple_dir_operations;
77 /* directory inodes start off with i_nlink == 2 (for "." entry) */
81 inode->i_op = &page_symlink_inode_operations;
89 * File creation. Allocate an inode, and we're done..
93 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
95 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
99 d_instantiate(dentry, inode);
100 dget(dentry); /* Extra count - pin the dentry in core */
102 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
107 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
109 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
115 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
117 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
120 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
125 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
127 int l = strlen(symname)+1;
128 error = page_symlink(inode, symname, l);
130 d_instantiate(dentry, inode);
132 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
139 static const struct inode_operations ramfs_dir_inode_operations = {
140 .create = ramfs_create,
141 .lookup = simple_lookup,
143 .unlink = simple_unlink,
144 .symlink = ramfs_symlink,
145 .mkdir = ramfs_mkdir,
146 .rmdir = simple_rmdir,
147 .mknod = ramfs_mknod,
148 .rename = simple_rename,
151 static const struct super_operations ramfs_ops = {
152 .statfs = simple_statfs,
153 .drop_inode = generic_delete_inode,
154 .show_options = generic_show_options,
157 struct ramfs_mount_opts {
166 static const match_table_t tokens = {
167 {Opt_mode, "mode=%o"},
171 struct ramfs_fs_info {
172 struct ramfs_mount_opts mount_opts;
175 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
177 substring_t args[MAX_OPT_ARGS];
182 opts->mode = RAMFS_DEFAULT_MODE;
184 while ((p = strsep(&data, ",")) != NULL) {
188 token = match_token(p, tokens, args);
191 if (match_octal(&args[0], &option))
193 opts->mode = option & S_IALLUGO;
196 * We might like to report bad mount options here;
197 * but traditionally ramfs has ignored all mount options,
198 * and as it is used as a !CONFIG_SHMEM simple substitute
199 * for tmpfs, better continue to ignore other mount options.
207 int ramfs_fill_super(struct super_block *sb, void *data, int silent)
209 struct ramfs_fs_info *fsi;
213 save_mount_options(sb, data);
215 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
220 err = ramfs_parse_options(data, &fsi->mount_opts);
224 sb->s_maxbytes = MAX_LFS_FILESIZE;
225 sb->s_blocksize = PAGE_CACHE_SIZE;
226 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
227 sb->s_magic = RAMFS_MAGIC;
228 sb->s_op = &ramfs_ops;
231 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
232 sb->s_root = d_make_root(inode);
239 struct dentry *ramfs_mount(struct file_system_type *fs_type,
240 int flags, const char *dev_name, void *data)
242 return mount_nodev(fs_type, flags, data, ramfs_fill_super);
245 static void ramfs_kill_sb(struct super_block *sb)
247 kfree(sb->s_fs_info);
248 kill_litter_super(sb);
251 static struct file_system_type ramfs_fs_type = {
253 .mount = ramfs_mount,
254 .kill_sb = ramfs_kill_sb,
255 .fs_flags = FS_USERNS_MOUNT,
258 int __init init_ramfs_fs(void)
260 static unsigned long once;
262 if (test_and_set_bit(0, &once))
264 return register_filesystem(&ramfs_fs_type);
266 fs_initcall(init_ramfs_fs);