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 <linux/magic.h> 38 #include <asm/uaccess.h> 39 #include "internal.h" 40 41 #define RAMFS_DEFAULT_MODE 0755 42 43 static const struct super_operations ramfs_ops; 44 static const struct inode_operations ramfs_dir_inode_operations; 45 46 static struct backing_dev_info ramfs_backing_dev_info = { 47 .name = "ramfs", 48 .ra_pages = 0, /* No readahead */ 49 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | 50 BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY | 51 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP, 52 }; 53 54 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev) 55 { 56 struct inode * inode = new_inode(sb); 57 58 if (inode) { 59 inode->i_mode = mode; 60 inode->i_uid = current_fsuid(); 61 inode->i_gid = current_fsgid(); 62 inode->i_mapping->a_ops = &ramfs_aops; 63 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; 64 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 65 mapping_set_unevictable(inode->i_mapping); 66 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 67 switch (mode & S_IFMT) { 68 default: 69 init_special_inode(inode, mode, dev); 70 break; 71 case S_IFREG: 72 inode->i_op = &ramfs_file_inode_operations; 73 inode->i_fop = &ramfs_file_operations; 74 break; 75 case S_IFDIR: 76 inode->i_op = &ramfs_dir_inode_operations; 77 inode->i_fop = &simple_dir_operations; 78 79 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 80 inc_nlink(inode); 81 break; 82 case S_IFLNK: 83 inode->i_op = &page_symlink_inode_operations; 84 break; 85 } 86 } 87 return inode; 88 } 89 90 /* 91 * File creation. Allocate an inode, and we're done.. 92 */ 93 /* SMP-safe */ 94 static int 95 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) 96 { 97 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev); 98 int error = -ENOSPC; 99 100 if (inode) { 101 if (dir->i_mode & S_ISGID) { 102 inode->i_gid = dir->i_gid; 103 if (S_ISDIR(mode)) 104 inode->i_mode |= S_ISGID; 105 } 106 d_instantiate(dentry, inode); 107 dget(dentry); /* Extra count - pin the dentry in core */ 108 error = 0; 109 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 110 } 111 return error; 112 } 113 114 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) 115 { 116 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 117 if (!retval) 118 inc_nlink(dir); 119 return retval; 120 } 121 122 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) 123 { 124 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 125 } 126 127 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 128 { 129 struct inode *inode; 130 int error = -ENOSPC; 131 132 inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0); 133 if (inode) { 134 int l = strlen(symname)+1; 135 error = page_symlink(inode, symname, l); 136 if (!error) { 137 if (dir->i_mode & S_ISGID) 138 inode->i_gid = dir->i_gid; 139 d_instantiate(dentry, inode); 140 dget(dentry); 141 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 142 } else 143 iput(inode); 144 } 145 return error; 146 } 147 148 static const struct inode_operations ramfs_dir_inode_operations = { 149 .create = ramfs_create, 150 .lookup = simple_lookup, 151 .link = simple_link, 152 .unlink = simple_unlink, 153 .symlink = ramfs_symlink, 154 .mkdir = ramfs_mkdir, 155 .rmdir = simple_rmdir, 156 .mknod = ramfs_mknod, 157 .rename = simple_rename, 158 }; 159 160 static const struct super_operations ramfs_ops = { 161 .statfs = simple_statfs, 162 .drop_inode = generic_delete_inode, 163 .show_options = generic_show_options, 164 }; 165 166 struct ramfs_mount_opts { 167 umode_t mode; 168 }; 169 170 enum { 171 Opt_mode, 172 Opt_err 173 }; 174 175 static const match_table_t tokens = { 176 {Opt_mode, "mode=%o"}, 177 {Opt_err, NULL} 178 }; 179 180 struct ramfs_fs_info { 181 struct ramfs_mount_opts mount_opts; 182 }; 183 184 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) 185 { 186 substring_t args[MAX_OPT_ARGS]; 187 int option; 188 int token; 189 char *p; 190 191 opts->mode = RAMFS_DEFAULT_MODE; 192 193 while ((p = strsep(&data, ",")) != NULL) { 194 if (!*p) 195 continue; 196 197 token = match_token(p, tokens, args); 198 switch (token) { 199 case Opt_mode: 200 if (match_octal(&args[0], &option)) 201 return -EINVAL; 202 opts->mode = option & S_IALLUGO; 203 break; 204 /* 205 * We might like to report bad mount options here; 206 * but traditionally ramfs has ignored all mount options, 207 * and as it is used as a !CONFIG_SHMEM simple substitute 208 * for tmpfs, better continue to ignore other mount options. 209 */ 210 } 211 } 212 213 return 0; 214 } 215 216 static int ramfs_fill_super(struct super_block * sb, void * data, int silent) 217 { 218 struct ramfs_fs_info *fsi; 219 struct inode *inode = NULL; 220 struct dentry *root; 221 int err; 222 223 save_mount_options(sb, data); 224 225 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); 226 sb->s_fs_info = fsi; 227 if (!fsi) { 228 err = -ENOMEM; 229 goto fail; 230 } 231 232 err = ramfs_parse_options(data, &fsi->mount_opts); 233 if (err) 234 goto fail; 235 236 sb->s_maxbytes = MAX_LFS_FILESIZE; 237 sb->s_blocksize = PAGE_CACHE_SIZE; 238 sb->s_blocksize_bits = PAGE_CACHE_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, S_IFDIR | fsi->mount_opts.mode, 0); 244 if (!inode) { 245 err = -ENOMEM; 246 goto fail; 247 } 248 249 root = d_alloc_root(inode); 250 sb->s_root = root; 251 if (!root) { 252 err = -ENOMEM; 253 goto fail; 254 } 255 256 return 0; 257 fail: 258 kfree(fsi); 259 sb->s_fs_info = NULL; 260 iput(inode); 261 return err; 262 } 263 264 int ramfs_get_sb(struct file_system_type *fs_type, 265 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 266 { 267 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt); 268 } 269 270 static int rootfs_get_sb(struct file_system_type *fs_type, 271 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 272 { 273 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super, 274 mnt); 275 } 276 277 static void ramfs_kill_sb(struct super_block *sb) 278 { 279 kfree(sb->s_fs_info); 280 kill_litter_super(sb); 281 } 282 283 static struct file_system_type ramfs_fs_type = { 284 .name = "ramfs", 285 .get_sb = ramfs_get_sb, 286 .kill_sb = ramfs_kill_sb, 287 }; 288 static struct file_system_type rootfs_fs_type = { 289 .name = "rootfs", 290 .get_sb = rootfs_get_sb, 291 .kill_sb = kill_litter_super, 292 }; 293 294 static int __init init_ramfs_fs(void) 295 { 296 return register_filesystem(&ramfs_fs_type); 297 } 298 299 static void __exit exit_ramfs_fs(void) 300 { 301 unregister_filesystem(&ramfs_fs_type); 302 } 303 304 module_init(init_ramfs_fs) 305 module_exit(exit_ramfs_fs) 306 307 int __init init_rootfs(void) 308 { 309 int err; 310 311 err = bdi_init(&ramfs_backing_dev_info); 312 if (err) 313 return err; 314 315 err = register_filesystem(&rootfs_fs_type); 316 if (err) 317 bdi_destroy(&ramfs_backing_dev_info); 318 319 return err; 320 } 321 322 MODULE_LICENSE("GPL"); 323