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 <linux/uaccess.h>
39 #include <linux/fs_context.h>
40 #include <linux/fs_parser.h>
43 struct ramfs_mount_opts {
47 struct ramfs_fs_info {
48 struct ramfs_mount_opts mount_opts;
51 #define RAMFS_DEFAULT_MODE 0755
53 static const struct super_operations ramfs_ops;
54 static const struct inode_operations ramfs_dir_inode_operations;
56 struct inode *ramfs_get_inode(struct super_block *sb,
57 const struct inode *dir, umode_t mode, dev_t dev)
59 struct inode * inode = new_inode(sb);
62 inode->i_ino = get_next_ino();
63 inode_init_owner(&init_user_ns, inode, dir, mode);
64 inode->i_mapping->a_ops = &ram_aops;
65 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
66 mapping_set_unevictable(inode->i_mapping);
67 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
68 switch (mode & S_IFMT) {
70 init_special_inode(inode, mode, dev);
73 inode->i_op = &ramfs_file_inode_operations;
74 inode->i_fop = &ramfs_file_operations;
77 inode->i_op = &ramfs_dir_inode_operations;
78 inode->i_fop = &simple_dir_operations;
80 /* directory inodes start off with i_nlink == 2 (for "." entry) */
84 inode->i_op = &page_symlink_inode_operations;
85 inode_nohighmem(inode);
93 * File creation. Allocate an inode, and we're done..
97 ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
98 struct dentry *dentry, umode_t mode, dev_t dev)
100 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
104 d_instantiate(dentry, inode);
105 dget(dentry); /* Extra count - pin the dentry in core */
107 dir->i_mtime = dir->i_ctime = current_time(dir);
112 static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
113 struct dentry *dentry, umode_t mode)
115 int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0);
121 static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir,
122 struct dentry *dentry, umode_t mode, bool excl)
124 return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
127 static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
128 struct dentry *dentry, const char *symname)
133 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
135 int l = strlen(symname)+1;
136 error = page_symlink(inode, symname, l);
138 d_instantiate(dentry, inode);
140 dir->i_mtime = dir->i_ctime = current_time(dir);
147 static int ramfs_tmpfile(struct user_namespace *mnt_userns,
148 struct inode *dir, struct dentry *dentry, umode_t mode)
152 inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
155 d_tmpfile(dentry, inode);
159 static const struct inode_operations ramfs_dir_inode_operations = {
160 .create = ramfs_create,
161 .lookup = simple_lookup,
163 .unlink = simple_unlink,
164 .symlink = ramfs_symlink,
165 .mkdir = ramfs_mkdir,
166 .rmdir = simple_rmdir,
167 .mknod = ramfs_mknod,
168 .rename = simple_rename,
169 .tmpfile = ramfs_tmpfile,
173 * Display the mount options in /proc/mounts.
175 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
177 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
179 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
180 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
184 static const struct super_operations ramfs_ops = {
185 .statfs = simple_statfs,
186 .drop_inode = generic_delete_inode,
187 .show_options = ramfs_show_options,
194 const struct fs_parameter_spec ramfs_fs_parameters[] = {
195 fsparam_u32oct("mode", Opt_mode),
199 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
201 struct fs_parse_result result;
202 struct ramfs_fs_info *fsi = fc->s_fs_info;
205 opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
208 * We might like to report bad mount options here;
209 * but traditionally ramfs has ignored all mount options,
210 * and as it is used as a !CONFIG_SHMEM simple substitute
211 * for tmpfs, better continue to ignore other mount options.
213 if (opt == -ENOPARAM)
220 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
227 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
229 struct ramfs_fs_info *fsi = sb->s_fs_info;
232 sb->s_maxbytes = MAX_LFS_FILESIZE;
233 sb->s_blocksize = PAGE_SIZE;
234 sb->s_blocksize_bits = PAGE_SHIFT;
235 sb->s_magic = RAMFS_MAGIC;
236 sb->s_op = &ramfs_ops;
239 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
240 sb->s_root = d_make_root(inode);
247 static int ramfs_get_tree(struct fs_context *fc)
249 return get_tree_nodev(fc, ramfs_fill_super);
252 static void ramfs_free_fc(struct fs_context *fc)
254 kfree(fc->s_fs_info);
257 static const struct fs_context_operations ramfs_context_ops = {
258 .free = ramfs_free_fc,
259 .parse_param = ramfs_parse_param,
260 .get_tree = ramfs_get_tree,
263 int ramfs_init_fs_context(struct fs_context *fc)
265 struct ramfs_fs_info *fsi;
267 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
271 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
273 fc->ops = &ramfs_context_ops;
277 static void ramfs_kill_sb(struct super_block *sb)
279 kfree(sb->s_fs_info);
280 kill_litter_super(sb);
283 static struct file_system_type ramfs_fs_type = {
285 .init_fs_context = ramfs_init_fs_context,
286 .parameters = ramfs_fs_parameters,
287 .kill_sb = ramfs_kill_sb,
288 .fs_flags = FS_USERNS_MOUNT,
291 static int __init init_ramfs_fs(void)
293 return register_filesystem(&ramfs_fs_type);
295 fs_initcall(init_ramfs_fs);