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>
41 #include <linux/seq_file.h>
44 struct ramfs_mount_opts {
48 struct ramfs_fs_info {
49 struct ramfs_mount_opts mount_opts;
52 #define RAMFS_DEFAULT_MODE 0755
54 static const struct super_operations ramfs_ops;
55 static const struct inode_operations ramfs_dir_inode_operations;
57 struct inode *ramfs_get_inode(struct super_block *sb,
58 const struct inode *dir, umode_t mode, dev_t dev)
60 struct inode * inode = new_inode(sb);
63 inode->i_ino = get_next_ino();
64 inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
65 inode->i_mapping->a_ops = &ram_aops;
66 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
67 mapping_set_unevictable(inode->i_mapping);
68 simple_inode_init_ts(inode);
69 switch (mode & S_IFMT) {
71 init_special_inode(inode, mode, dev);
74 inode->i_op = &ramfs_file_inode_operations;
75 inode->i_fop = &ramfs_file_operations;
78 inode->i_op = &ramfs_dir_inode_operations;
79 inode->i_fop = &simple_dir_operations;
81 /* directory inodes start off with i_nlink == 2 (for "." entry) */
85 inode->i_op = &page_symlink_inode_operations;
86 inode_nohighmem(inode);
94 * File creation. Allocate an inode, and we're done..
98 ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
99 struct dentry *dentry, umode_t mode, dev_t dev)
101 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
105 d_instantiate(dentry, inode);
106 dget(dentry); /* Extra count - pin the dentry in core */
108 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
113 static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
114 struct dentry *dentry, umode_t mode)
116 int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0);
122 static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir,
123 struct dentry *dentry, umode_t mode, bool excl)
125 return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
128 static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
129 struct dentry *dentry, const char *symname)
134 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
136 int l = strlen(symname)+1;
137 error = page_symlink(inode, symname, l);
139 d_instantiate(dentry, inode);
141 inode_set_mtime_to_ts(dir,
142 inode_set_ctime_current(dir));
149 static int ramfs_tmpfile(struct mnt_idmap *idmap,
150 struct inode *dir, struct file *file, umode_t mode)
154 inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
157 d_tmpfile(file, inode);
158 return finish_open_simple(file, 0);
161 static const struct inode_operations ramfs_dir_inode_operations = {
162 .create = ramfs_create,
163 .lookup = simple_lookup,
165 .unlink = simple_unlink,
166 .symlink = ramfs_symlink,
167 .mkdir = ramfs_mkdir,
168 .rmdir = simple_rmdir,
169 .mknod = ramfs_mknod,
170 .rename = simple_rename,
171 .tmpfile = ramfs_tmpfile,
175 * Display the mount options in /proc/mounts.
177 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
179 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
181 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
182 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
186 static const struct super_operations ramfs_ops = {
187 .statfs = simple_statfs,
188 .drop_inode = generic_delete_inode,
189 .show_options = ramfs_show_options,
196 const struct fs_parameter_spec ramfs_fs_parameters[] = {
197 fsparam_u32oct("mode", Opt_mode),
201 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
203 struct fs_parse_result result;
204 struct ramfs_fs_info *fsi = fc->s_fs_info;
207 opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
208 if (opt == -ENOPARAM) {
209 opt = vfs_parse_fs_param_source(fc, param);
210 if (opt != -ENOPARAM)
213 * We might like to report bad mount options here;
214 * but traditionally ramfs has ignored all mount options,
215 * and as it is used as a !CONFIG_SHMEM simple substitute
216 * for tmpfs, better continue to ignore other mount options.
225 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
232 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
234 struct ramfs_fs_info *fsi = sb->s_fs_info;
237 sb->s_maxbytes = MAX_LFS_FILESIZE;
238 sb->s_blocksize = PAGE_SIZE;
239 sb->s_blocksize_bits = PAGE_SHIFT;
240 sb->s_magic = RAMFS_MAGIC;
241 sb->s_op = &ramfs_ops;
244 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
245 sb->s_root = d_make_root(inode);
252 static int ramfs_get_tree(struct fs_context *fc)
254 return get_tree_nodev(fc, ramfs_fill_super);
257 static void ramfs_free_fc(struct fs_context *fc)
259 kfree(fc->s_fs_info);
262 static const struct fs_context_operations ramfs_context_ops = {
263 .free = ramfs_free_fc,
264 .parse_param = ramfs_parse_param,
265 .get_tree = ramfs_get_tree,
268 int ramfs_init_fs_context(struct fs_context *fc)
270 struct ramfs_fs_info *fsi;
272 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
276 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
278 fc->ops = &ramfs_context_ops;
282 void ramfs_kill_sb(struct super_block *sb)
284 kfree(sb->s_fs_info);
285 kill_litter_super(sb);
288 static struct file_system_type ramfs_fs_type = {
290 .init_fs_context = ramfs_init_fs_context,
291 .parameters = ramfs_fs_parameters,
292 .kill_sb = ramfs_kill_sb,
293 .fs_flags = FS_USERNS_MOUNT,
296 static int __init init_ramfs_fs(void)
298 return register_filesystem(&ramfs_fs_type);
300 fs_initcall(init_ramfs_fs);