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/module.h> 27 #include <linux/fs.h> 28 #include <linux/pagemap.h> 29 #include <linux/highmem.h> 30 #include <linux/time.h> 31 #include <linux/init.h> 32 #include <linux/string.h> 33 #include <linux/backing-dev.h> 34 #include <linux/ramfs.h> 35 #include <linux/sched.h> 36 #include <linux/parser.h> 37 #include <asm/uaccess.h> 38 #include "internal.h" 39 40 /* some random number */ 41 #define RAMFS_MAGIC 0x858458f6 42 43 #define RAMFS_DEFAULT_MODE 0755 44 45 static const struct super_operations ramfs_ops; 46 static const struct inode_operations ramfs_dir_inode_operations; 47 48 static struct backing_dev_info ramfs_backing_dev_info = { 49 .name = "ramfs", 50 .ra_pages = 0, /* No readahead */ 51 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | 52 BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY | 53 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP, 54 }; 55 56 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev) 57 { 58 struct inode * inode = new_inode(sb); 59 60 if (inode) { 61 inode->i_mode = mode; 62 inode->i_uid = current_fsuid(); 63 inode->i_gid = current_fsgid(); 64 inode->i_mapping->a_ops = &ramfs_aops; 65 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; 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; 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 break; 87 } 88 } 89 return inode; 90 } 91 92 /* 93 * File creation. Allocate an inode, and we're done.. 94 */ 95 /* SMP-safe */ 96 static int 97 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) 98 { 99 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev); 100 int error = -ENOSPC; 101 102 if (inode) { 103 if (dir->i_mode & S_ISGID) { 104 inode->i_gid = dir->i_gid; 105 if (S_ISDIR(mode)) 106 inode->i_mode |= S_ISGID; 107 } 108 d_instantiate(dentry, inode); 109 dget(dentry); /* Extra count - pin the dentry in core */ 110 error = 0; 111 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 112 } 113 return error; 114 } 115 116 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) 117 { 118 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 119 if (!retval) 120 inc_nlink(dir); 121 return retval; 122 } 123 124 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) 125 { 126 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 127 } 128 129 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 130 { 131 struct inode *inode; 132 int error = -ENOSPC; 133 134 inode = ramfs_get_inode(dir->i_sb, 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 if (dir->i_mode & S_ISGID) 140 inode->i_gid = dir->i_gid; 141 d_instantiate(dentry, inode); 142 dget(dentry); 143 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 144 } else 145 iput(inode); 146 } 147 return error; 148 } 149 150 static const struct inode_operations ramfs_dir_inode_operations = { 151 .create = ramfs_create, 152 .lookup = simple_lookup, 153 .link = simple_link, 154 .unlink = simple_unlink, 155 .symlink = ramfs_symlink, 156 .mkdir = ramfs_mkdir, 157 .rmdir = simple_rmdir, 158 .mknod = ramfs_mknod, 159 .rename = simple_rename, 160 }; 161 162 static const struct super_operations ramfs_ops = { 163 .statfs = simple_statfs, 164 .drop_inode = generic_delete_inode, 165 .show_options = generic_show_options, 166 }; 167 168 struct ramfs_mount_opts { 169 umode_t mode; 170 }; 171 172 enum { 173 Opt_mode, 174 Opt_err 175 }; 176 177 static const match_table_t tokens = { 178 {Opt_mode, "mode=%o"}, 179 {Opt_err, NULL} 180 }; 181 182 struct ramfs_fs_info { 183 struct ramfs_mount_opts mount_opts; 184 }; 185 186 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) 187 { 188 substring_t args[MAX_OPT_ARGS]; 189 int option; 190 int token; 191 char *p; 192 193 opts->mode = RAMFS_DEFAULT_MODE; 194 195 while ((p = strsep(&data, ",")) != NULL) { 196 if (!*p) 197 continue; 198 199 token = match_token(p, tokens, args); 200 switch (token) { 201 case Opt_mode: 202 if (match_octal(&args[0], &option)) 203 return -EINVAL; 204 opts->mode = option & S_IALLUGO; 205 break; 206 /* 207 * We might like to report bad mount options here; 208 * but traditionally ramfs has ignored all mount options, 209 * and as it is used as a !CONFIG_SHMEM simple substitute 210 * for tmpfs, better continue to ignore other mount options. 211 */ 212 } 213 } 214 215 return 0; 216 } 217 218 static int ramfs_fill_super(struct super_block * sb, void * data, int silent) 219 { 220 struct ramfs_fs_info *fsi; 221 struct inode *inode = NULL; 222 struct dentry *root; 223 int err; 224 225 save_mount_options(sb, data); 226 227 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); 228 sb->s_fs_info = fsi; 229 if (!fsi) { 230 err = -ENOMEM; 231 goto fail; 232 } 233 234 err = ramfs_parse_options(data, &fsi->mount_opts); 235 if (err) 236 goto fail; 237 238 sb->s_maxbytes = MAX_LFS_FILESIZE; 239 sb->s_blocksize = PAGE_CACHE_SIZE; 240 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 241 sb->s_magic = RAMFS_MAGIC; 242 sb->s_op = &ramfs_ops; 243 sb->s_time_gran = 1; 244 245 inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0); 246 if (!inode) { 247 err = -ENOMEM; 248 goto fail; 249 } 250 251 root = d_alloc_root(inode); 252 sb->s_root = root; 253 if (!root) { 254 err = -ENOMEM; 255 goto fail; 256 } 257 258 return 0; 259 fail: 260 kfree(fsi); 261 sb->s_fs_info = NULL; 262 iput(inode); 263 return err; 264 } 265 266 int ramfs_get_sb(struct file_system_type *fs_type, 267 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 268 { 269 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt); 270 } 271 272 static int rootfs_get_sb(struct file_system_type *fs_type, 273 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 274 { 275 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super, 276 mnt); 277 } 278 279 static void ramfs_kill_sb(struct super_block *sb) 280 { 281 kfree(sb->s_fs_info); 282 kill_litter_super(sb); 283 } 284 285 static struct file_system_type ramfs_fs_type = { 286 .name = "ramfs", 287 .get_sb = ramfs_get_sb, 288 .kill_sb = ramfs_kill_sb, 289 }; 290 static struct file_system_type rootfs_fs_type = { 291 .name = "rootfs", 292 .get_sb = rootfs_get_sb, 293 .kill_sb = kill_litter_super, 294 }; 295 296 static int __init init_ramfs_fs(void) 297 { 298 return register_filesystem(&ramfs_fs_type); 299 } 300 301 static void __exit exit_ramfs_fs(void) 302 { 303 unregister_filesystem(&ramfs_fs_type); 304 } 305 306 module_init(init_ramfs_fs) 307 module_exit(exit_ramfs_fs) 308 309 int __init init_rootfs(void) 310 { 311 int err; 312 313 err = bdi_init(&ramfs_backing_dev_info); 314 if (err) 315 return err; 316 317 err = register_filesystem(&rootfs_fs_type); 318 if (err) 319 bdi_destroy(&ramfs_backing_dev_info); 320 321 return err; 322 } 323 324 MODULE_LICENSE("GPL"); 325