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