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 .ra_pages = 0, /* No readahead */ 50 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | 51 BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY | 52 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP, 53 }; 54 55 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev) 56 { 57 struct inode * inode = new_inode(sb); 58 59 if (inode) { 60 inode->i_mode = mode; 61 inode->i_uid = current_fsuid(); 62 inode->i_gid = current_fsgid(); 63 inode->i_mapping->a_ops = &ramfs_aops; 64 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; 65 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 66 mapping_set_unevictable(inode->i_mapping); 67 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 68 switch (mode & S_IFMT) { 69 default: 70 init_special_inode(inode, mode, dev); 71 break; 72 case S_IFREG: 73 inode->i_op = &ramfs_file_inode_operations; 74 inode->i_fop = &ramfs_file_operations; 75 break; 76 case S_IFDIR: 77 inode->i_op = &ramfs_dir_inode_operations; 78 inode->i_fop = &simple_dir_operations; 79 80 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 81 inc_nlink(inode); 82 break; 83 case S_IFLNK: 84 inode->i_op = &page_symlink_inode_operations; 85 break; 86 } 87 } 88 return inode; 89 } 90 91 /* 92 * File creation. Allocate an inode, and we're done.. 93 */ 94 /* SMP-safe */ 95 static int 96 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) 97 { 98 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev); 99 int error = -ENOSPC; 100 101 if (inode) { 102 if (dir->i_mode & S_ISGID) { 103 inode->i_gid = dir->i_gid; 104 if (S_ISDIR(mode)) 105 inode->i_mode |= S_ISGID; 106 } 107 d_instantiate(dentry, inode); 108 dget(dentry); /* Extra count - pin the dentry in core */ 109 error = 0; 110 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 111 } 112 return error; 113 } 114 115 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) 116 { 117 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 118 if (!retval) 119 inc_nlink(dir); 120 return retval; 121 } 122 123 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) 124 { 125 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 126 } 127 128 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 129 { 130 struct inode *inode; 131 int error = -ENOSPC; 132 133 inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0); 134 if (inode) { 135 int l = strlen(symname)+1; 136 error = page_symlink(inode, symname, l); 137 if (!error) { 138 if (dir->i_mode & S_ISGID) 139 inode->i_gid = dir->i_gid; 140 d_instantiate(dentry, inode); 141 dget(dentry); 142 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 143 } else 144 iput(inode); 145 } 146 return error; 147 } 148 149 static const struct inode_operations ramfs_dir_inode_operations = { 150 .create = ramfs_create, 151 .lookup = simple_lookup, 152 .link = simple_link, 153 .unlink = simple_unlink, 154 .symlink = ramfs_symlink, 155 .mkdir = ramfs_mkdir, 156 .rmdir = simple_rmdir, 157 .mknod = ramfs_mknod, 158 .rename = simple_rename, 159 }; 160 161 static const struct super_operations ramfs_ops = { 162 .statfs = simple_statfs, 163 .drop_inode = generic_delete_inode, 164 .show_options = generic_show_options, 165 }; 166 167 struct ramfs_mount_opts { 168 umode_t mode; 169 }; 170 171 enum { 172 Opt_mode, 173 Opt_err 174 }; 175 176 static const match_table_t tokens = { 177 {Opt_mode, "mode=%o"}, 178 {Opt_err, NULL} 179 }; 180 181 struct ramfs_fs_info { 182 struct ramfs_mount_opts mount_opts; 183 }; 184 185 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) 186 { 187 substring_t args[MAX_OPT_ARGS]; 188 int option; 189 int token; 190 char *p; 191 192 opts->mode = RAMFS_DEFAULT_MODE; 193 194 while ((p = strsep(&data, ",")) != NULL) { 195 if (!*p) 196 continue; 197 198 token = match_token(p, tokens, args); 199 switch (token) { 200 case Opt_mode: 201 if (match_octal(&args[0], &option)) 202 return -EINVAL; 203 opts->mode = option & S_IALLUGO; 204 break; 205 default: 206 printk(KERN_ERR "ramfs: bad mount option: %s\n", p); 207 return -EINVAL; 208 } 209 } 210 211 return 0; 212 } 213 214 static int ramfs_fill_super(struct super_block * sb, void * data, int silent) 215 { 216 struct ramfs_fs_info *fsi; 217 struct inode *inode = NULL; 218 struct dentry *root; 219 int err; 220 221 save_mount_options(sb, data); 222 223 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); 224 sb->s_fs_info = fsi; 225 if (!fsi) { 226 err = -ENOMEM; 227 goto fail; 228 } 229 230 err = ramfs_parse_options(data, &fsi->mount_opts); 231 if (err) 232 goto fail; 233 234 sb->s_maxbytes = MAX_LFS_FILESIZE; 235 sb->s_blocksize = PAGE_CACHE_SIZE; 236 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 237 sb->s_magic = RAMFS_MAGIC; 238 sb->s_op = &ramfs_ops; 239 sb->s_time_gran = 1; 240 241 inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0); 242 if (!inode) { 243 err = -ENOMEM; 244 goto fail; 245 } 246 247 root = d_alloc_root(inode); 248 sb->s_root = root; 249 if (!root) { 250 err = -ENOMEM; 251 goto fail; 252 } 253 254 return 0; 255 fail: 256 kfree(fsi); 257 sb->s_fs_info = NULL; 258 iput(inode); 259 return err; 260 } 261 262 int ramfs_get_sb(struct file_system_type *fs_type, 263 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 264 { 265 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt); 266 } 267 268 static int rootfs_get_sb(struct file_system_type *fs_type, 269 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 270 { 271 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super, 272 mnt); 273 } 274 275 static void ramfs_kill_sb(struct super_block *sb) 276 { 277 kfree(sb->s_fs_info); 278 kill_litter_super(sb); 279 } 280 281 static struct file_system_type ramfs_fs_type = { 282 .name = "ramfs", 283 .get_sb = ramfs_get_sb, 284 .kill_sb = ramfs_kill_sb, 285 }; 286 static struct file_system_type rootfs_fs_type = { 287 .name = "rootfs", 288 .get_sb = rootfs_get_sb, 289 .kill_sb = kill_litter_super, 290 }; 291 292 static int __init init_ramfs_fs(void) 293 { 294 return register_filesystem(&ramfs_fs_type); 295 } 296 297 static void __exit exit_ramfs_fs(void) 298 { 299 unregister_filesystem(&ramfs_fs_type); 300 } 301 302 module_init(init_ramfs_fs) 303 module_exit(exit_ramfs_fs) 304 305 int __init init_rootfs(void) 306 { 307 int err; 308 309 err = bdi_init(&ramfs_backing_dev_info); 310 if (err) 311 return err; 312 313 err = register_filesystem(&rootfs_fs_type); 314 if (err) 315 bdi_destroy(&ramfs_backing_dev_info); 316 317 return err; 318 } 319 320 MODULE_LICENSE("GPL"); 321