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(&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) { 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 mnt_idmap *idmap, 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 error = security_inode_init_security(inode, dir, 106 &dentry->d_name, NULL, 107 NULL); 108 if (error) { 109 iput(inode); 110 goto out; 111 } 112 113 d_instantiate(dentry, inode); 114 dget(dentry); /* Extra count - pin the dentry in core */ 115 error = 0; 116 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); 117 } 118 out: 119 return error; 120 } 121 122 static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir, 123 struct dentry *dentry, umode_t mode) 124 { 125 int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0); 126 if (!retval) 127 inc_nlink(dir); 128 return retval; 129 } 130 131 static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir, 132 struct dentry *dentry, umode_t mode, bool excl) 133 { 134 return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0); 135 } 136 137 static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir, 138 struct dentry *dentry, const char *symname) 139 { 140 struct inode *inode; 141 int error = -ENOSPC; 142 143 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 144 if (inode) { 145 int l = strlen(symname)+1; 146 147 error = security_inode_init_security(inode, dir, 148 &dentry->d_name, NULL, 149 NULL); 150 if (error) { 151 iput(inode); 152 goto out; 153 } 154 155 error = page_symlink(inode, symname, l); 156 if (!error) { 157 d_instantiate(dentry, inode); 158 dget(dentry); 159 inode_set_mtime_to_ts(dir, 160 inode_set_ctime_current(dir)); 161 } else 162 iput(inode); 163 } 164 out: 165 return error; 166 } 167 168 static int ramfs_tmpfile(struct mnt_idmap *idmap, 169 struct inode *dir, struct file *file, umode_t mode) 170 { 171 struct inode *inode; 172 int error; 173 174 inode = ramfs_get_inode(dir->i_sb, dir, mode, 0); 175 if (!inode) 176 return -ENOSPC; 177 178 error = security_inode_init_security(inode, dir, 179 &file_dentry(file)->d_name, NULL, 180 NULL); 181 if (error) { 182 iput(inode); 183 goto out; 184 } 185 186 d_tmpfile(file, inode); 187 out: 188 return finish_open_simple(file, error); 189 } 190 191 static const struct inode_operations ramfs_dir_inode_operations = { 192 .create = ramfs_create, 193 .lookup = simple_lookup, 194 .link = simple_link, 195 .unlink = simple_unlink, 196 .symlink = ramfs_symlink, 197 .mkdir = ramfs_mkdir, 198 .rmdir = simple_rmdir, 199 .mknod = ramfs_mknod, 200 .rename = simple_rename, 201 .tmpfile = ramfs_tmpfile, 202 }; 203 204 /* 205 * Display the mount options in /proc/mounts. 206 */ 207 static int ramfs_show_options(struct seq_file *m, struct dentry *root) 208 { 209 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info; 210 211 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE) 212 seq_printf(m, ",mode=%o", fsi->mount_opts.mode); 213 return 0; 214 } 215 216 static const struct super_operations ramfs_ops = { 217 .statfs = simple_statfs, 218 .drop_inode = generic_delete_inode, 219 .show_options = ramfs_show_options, 220 }; 221 222 enum ramfs_param { 223 Opt_mode, 224 }; 225 226 const struct fs_parameter_spec ramfs_fs_parameters[] = { 227 fsparam_u32oct("mode", Opt_mode), 228 {} 229 }; 230 231 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 232 { 233 struct fs_parse_result result; 234 struct ramfs_fs_info *fsi = fc->s_fs_info; 235 int opt; 236 237 opt = fs_parse(fc, ramfs_fs_parameters, param, &result); 238 if (opt == -ENOPARAM) { 239 opt = vfs_parse_fs_param_source(fc, param); 240 if (opt != -ENOPARAM) 241 return opt; 242 /* 243 * We might like to report bad mount options here; 244 * but traditionally ramfs has ignored all mount options, 245 * and as it is used as a !CONFIG_SHMEM simple substitute 246 * for tmpfs, better continue to ignore other mount options. 247 */ 248 return 0; 249 } 250 if (opt < 0) 251 return opt; 252 253 switch (opt) { 254 case Opt_mode: 255 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO; 256 break; 257 } 258 259 return 0; 260 } 261 262 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc) 263 { 264 struct ramfs_fs_info *fsi = sb->s_fs_info; 265 struct inode *inode; 266 267 sb->s_maxbytes = MAX_LFS_FILESIZE; 268 sb->s_blocksize = PAGE_SIZE; 269 sb->s_blocksize_bits = PAGE_SHIFT; 270 sb->s_magic = RAMFS_MAGIC; 271 sb->s_op = &ramfs_ops; 272 sb->s_time_gran = 1; 273 274 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 275 sb->s_root = d_make_root(inode); 276 if (!sb->s_root) 277 return -ENOMEM; 278 279 return 0; 280 } 281 282 static int ramfs_get_tree(struct fs_context *fc) 283 { 284 return get_tree_nodev(fc, ramfs_fill_super); 285 } 286 287 static void ramfs_free_fc(struct fs_context *fc) 288 { 289 kfree(fc->s_fs_info); 290 } 291 292 static const struct fs_context_operations ramfs_context_ops = { 293 .free = ramfs_free_fc, 294 .parse_param = ramfs_parse_param, 295 .get_tree = ramfs_get_tree, 296 }; 297 298 int ramfs_init_fs_context(struct fs_context *fc) 299 { 300 struct ramfs_fs_info *fsi; 301 302 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL); 303 if (!fsi) 304 return -ENOMEM; 305 306 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE; 307 fc->s_fs_info = fsi; 308 fc->ops = &ramfs_context_ops; 309 return 0; 310 } 311 312 void ramfs_kill_sb(struct super_block *sb) 313 { 314 kfree(sb->s_fs_info); 315 kill_litter_super(sb); 316 } 317 318 static struct file_system_type ramfs_fs_type = { 319 .name = "ramfs", 320 .init_fs_context = ramfs_init_fs_context, 321 .parameters = ramfs_fs_parameters, 322 .kill_sb = ramfs_kill_sb, 323 .fs_flags = FS_USERNS_MOUNT, 324 }; 325 326 static int __init init_ramfs_fs(void) 327 { 328 return register_filesystem(&ramfs_fs_type); 329 } 330 fs_initcall(init_ramfs_fs); 331