1 /* 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 26 #include <linux/fs.h> 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> 42 #include "internal.h" 43 44 struct ramfs_mount_opts { 45 umode_t mode; 46 }; 47 48 struct ramfs_fs_info { 49 struct ramfs_mount_opts mount_opts; 50 }; 51 52 #define RAMFS_DEFAULT_MODE 0755 53 54 static const struct super_operations ramfs_ops; 55 static const struct inode_operations ramfs_dir_inode_operations; 56 57 struct inode *ramfs_get_inode(struct super_block *sb, 58 const struct inode *dir, umode_t mode, dev_t dev) 59 { 60 struct inode * inode = new_inode(sb); 61 62 if (inode) { 63 inode->i_ino = get_next_ino(); 64 inode_init_owner(&init_user_ns, 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 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); 69 switch (mode & S_IFMT) { 70 default: 71 init_special_inode(inode, mode, dev); 72 break; 73 case S_IFREG: 74 inode->i_op = &ramfs_file_inode_operations; 75 inode->i_fop = &ramfs_file_operations; 76 break; 77 case S_IFDIR: 78 inode->i_op = &ramfs_dir_inode_operations; 79 inode->i_fop = &simple_dir_operations; 80 81 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 82 inc_nlink(inode); 83 break; 84 case S_IFLNK: 85 inode->i_op = &page_symlink_inode_operations; 86 inode_nohighmem(inode); 87 break; 88 } 89 } 90 return inode; 91 } 92 93 /* 94 * File creation. Allocate an inode, and we're done.. 95 */ 96 /* SMP-safe */ 97 static int 98 ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir, 99 struct dentry *dentry, umode_t mode, dev_t dev) 100 { 101 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev); 102 int error = -ENOSPC; 103 104 if (inode) { 105 d_instantiate(dentry, inode); 106 dget(dentry); /* Extra count - pin the dentry in core */ 107 error = 0; 108 dir->i_mtime = dir->i_ctime = current_time(dir); 109 } 110 return error; 111 } 112 113 static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir, 114 struct dentry *dentry, umode_t mode) 115 { 116 int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0); 117 if (!retval) 118 inc_nlink(dir); 119 return retval; 120 } 121 122 static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir, 123 struct dentry *dentry, umode_t mode, bool excl) 124 { 125 return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0); 126 } 127 128 static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir, 129 struct dentry *dentry, const char *symname) 130 { 131 struct inode *inode; 132 int error = -ENOSPC; 133 134 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 135 if (inode) { 136 int l = strlen(symname)+1; 137 error = page_symlink(inode, symname, l); 138 if (!error) { 139 d_instantiate(dentry, inode); 140 dget(dentry); 141 dir->i_mtime = dir->i_ctime = current_time(dir); 142 } else 143 iput(inode); 144 } 145 return error; 146 } 147 148 static int ramfs_tmpfile(struct user_namespace *mnt_userns, 149 struct inode *dir, struct file *file, umode_t mode) 150 { 151 struct inode *inode; 152 153 inode = ramfs_get_inode(dir->i_sb, dir, mode, 0); 154 if (!inode) 155 return -ENOSPC; 156 d_tmpfile(file, inode); 157 return finish_open_simple(file, 0); 158 } 159 160 static const struct inode_operations ramfs_dir_inode_operations = { 161 .create = ramfs_create, 162 .lookup = simple_lookup, 163 .link = simple_link, 164 .unlink = simple_unlink, 165 .symlink = ramfs_symlink, 166 .mkdir = ramfs_mkdir, 167 .rmdir = simple_rmdir, 168 .mknod = ramfs_mknod, 169 .rename = simple_rename, 170 .tmpfile = ramfs_tmpfile, 171 }; 172 173 /* 174 * Display the mount options in /proc/mounts. 175 */ 176 static int ramfs_show_options(struct seq_file *m, struct dentry *root) 177 { 178 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info; 179 180 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE) 181 seq_printf(m, ",mode=%o", fsi->mount_opts.mode); 182 return 0; 183 } 184 185 static const struct super_operations ramfs_ops = { 186 .statfs = simple_statfs, 187 .drop_inode = generic_delete_inode, 188 .show_options = ramfs_show_options, 189 }; 190 191 enum ramfs_param { 192 Opt_mode, 193 }; 194 195 const struct fs_parameter_spec ramfs_fs_parameters[] = { 196 fsparam_u32oct("mode", Opt_mode), 197 {} 198 }; 199 200 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 201 { 202 struct fs_parse_result result; 203 struct ramfs_fs_info *fsi = fc->s_fs_info; 204 int opt; 205 206 opt = fs_parse(fc, ramfs_fs_parameters, param, &result); 207 if (opt == -ENOPARAM) { 208 opt = vfs_parse_fs_param_source(fc, param); 209 if (opt != -ENOPARAM) 210 return opt; 211 /* 212 * We might like to report bad mount options here; 213 * but traditionally ramfs has ignored all mount options, 214 * and as it is used as a !CONFIG_SHMEM simple substitute 215 * for tmpfs, better continue to ignore other mount options. 216 */ 217 return 0; 218 } 219 if (opt < 0) 220 return opt; 221 222 switch (opt) { 223 case Opt_mode: 224 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO; 225 break; 226 } 227 228 return 0; 229 } 230 231 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc) 232 { 233 struct ramfs_fs_info *fsi = sb->s_fs_info; 234 struct inode *inode; 235 236 sb->s_maxbytes = MAX_LFS_FILESIZE; 237 sb->s_blocksize = PAGE_SIZE; 238 sb->s_blocksize_bits = PAGE_SHIFT; 239 sb->s_magic = RAMFS_MAGIC; 240 sb->s_op = &ramfs_ops; 241 sb->s_time_gran = 1; 242 243 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 244 sb->s_root = d_make_root(inode); 245 if (!sb->s_root) 246 return -ENOMEM; 247 248 return 0; 249 } 250 251 static int ramfs_get_tree(struct fs_context *fc) 252 { 253 return get_tree_nodev(fc, ramfs_fill_super); 254 } 255 256 static void ramfs_free_fc(struct fs_context *fc) 257 { 258 kfree(fc->s_fs_info); 259 } 260 261 static const struct fs_context_operations ramfs_context_ops = { 262 .free = ramfs_free_fc, 263 .parse_param = ramfs_parse_param, 264 .get_tree = ramfs_get_tree, 265 }; 266 267 int ramfs_init_fs_context(struct fs_context *fc) 268 { 269 struct ramfs_fs_info *fsi; 270 271 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL); 272 if (!fsi) 273 return -ENOMEM; 274 275 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE; 276 fc->s_fs_info = fsi; 277 fc->ops = &ramfs_context_ops; 278 return 0; 279 } 280 281 static void ramfs_kill_sb(struct super_block *sb) 282 { 283 kfree(sb->s_fs_info); 284 kill_litter_super(sb); 285 } 286 287 static struct file_system_type ramfs_fs_type = { 288 .name = "ramfs", 289 .init_fs_context = ramfs_init_fs_context, 290 .parameters = ramfs_fs_parameters, 291 .kill_sb = ramfs_kill_sb, 292 .fs_flags = FS_USERNS_MOUNT, 293 }; 294 295 static int __init init_ramfs_fs(void) 296 { 297 return register_filesystem(&ramfs_fs_type); 298 } 299 fs_initcall(init_ramfs_fs); 300