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 <linux/slab.h> 39 #include <asm/uaccess.h> 40 #include "internal.h" 41 42 #define RAMFS_DEFAULT_MODE 0755 43 44 static const struct super_operations ramfs_ops; 45 static const struct inode_operations ramfs_dir_inode_operations; 46 47 static struct backing_dev_info ramfs_backing_dev_info = { 48 .name = "ramfs", 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, 56 const struct inode *dir, int mode, dev_t dev) 57 { 58 struct inode * inode = new_inode(sb); 59 60 if (inode) { 61 inode->i_ino = get_next_ino(); 62 inode_init_owner(inode, dir, mode); 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, dir, mode, dev); 99 int error = -ENOSPC; 100 101 if (inode) { 102 d_instantiate(dentry, inode); 103 dget(dentry); /* Extra count - pin the dentry in core */ 104 error = 0; 105 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 106 } 107 return error; 108 } 109 110 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) 111 { 112 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 113 if (!retval) 114 inc_nlink(dir); 115 return retval; 116 } 117 118 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) 119 { 120 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 121 } 122 123 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 124 { 125 struct inode *inode; 126 int error = -ENOSPC; 127 128 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 129 if (inode) { 130 int l = strlen(symname)+1; 131 error = page_symlink(inode, symname, l); 132 if (!error) { 133 d_instantiate(dentry, inode); 134 dget(dentry); 135 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 136 } else 137 iput(inode); 138 } 139 return error; 140 } 141 142 static const struct inode_operations ramfs_dir_inode_operations = { 143 .create = ramfs_create, 144 .lookup = simple_lookup, 145 .link = simple_link, 146 .unlink = simple_unlink, 147 .symlink = ramfs_symlink, 148 .mkdir = ramfs_mkdir, 149 .rmdir = simple_rmdir, 150 .mknod = ramfs_mknod, 151 .rename = simple_rename, 152 }; 153 154 static const struct super_operations ramfs_ops = { 155 .statfs = simple_statfs, 156 .drop_inode = generic_delete_inode, 157 .show_options = generic_show_options, 158 }; 159 160 struct ramfs_mount_opts { 161 umode_t mode; 162 }; 163 164 enum { 165 Opt_mode, 166 Opt_err 167 }; 168 169 static const match_table_t tokens = { 170 {Opt_mode, "mode=%o"}, 171 {Opt_err, NULL} 172 }; 173 174 struct ramfs_fs_info { 175 struct ramfs_mount_opts mount_opts; 176 }; 177 178 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) 179 { 180 substring_t args[MAX_OPT_ARGS]; 181 int option; 182 int token; 183 char *p; 184 185 opts->mode = RAMFS_DEFAULT_MODE; 186 187 while ((p = strsep(&data, ",")) != NULL) { 188 if (!*p) 189 continue; 190 191 token = match_token(p, tokens, args); 192 switch (token) { 193 case Opt_mode: 194 if (match_octal(&args[0], &option)) 195 return -EINVAL; 196 opts->mode = option & S_IALLUGO; 197 break; 198 /* 199 * We might like to report bad mount options here; 200 * but traditionally ramfs has ignored all mount options, 201 * and as it is used as a !CONFIG_SHMEM simple substitute 202 * for tmpfs, better continue to ignore other mount options. 203 */ 204 } 205 } 206 207 return 0; 208 } 209 210 int ramfs_fill_super(struct super_block *sb, void *data, int silent) 211 { 212 struct ramfs_fs_info *fsi; 213 struct inode *inode = NULL; 214 struct dentry *root; 215 int err; 216 217 save_mount_options(sb, data); 218 219 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); 220 sb->s_fs_info = fsi; 221 if (!fsi) { 222 err = -ENOMEM; 223 goto fail; 224 } 225 226 err = ramfs_parse_options(data, &fsi->mount_opts); 227 if (err) 228 goto fail; 229 230 sb->s_maxbytes = MAX_LFS_FILESIZE; 231 sb->s_blocksize = PAGE_CACHE_SIZE; 232 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 233 sb->s_magic = RAMFS_MAGIC; 234 sb->s_op = &ramfs_ops; 235 sb->s_time_gran = 1; 236 237 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 238 if (!inode) { 239 err = -ENOMEM; 240 goto fail; 241 } 242 243 root = d_alloc_root(inode); 244 sb->s_root = root; 245 if (!root) { 246 err = -ENOMEM; 247 goto fail; 248 } 249 250 return 0; 251 fail: 252 kfree(fsi); 253 sb->s_fs_info = NULL; 254 iput(inode); 255 return err; 256 } 257 258 struct dentry *ramfs_mount(struct file_system_type *fs_type, 259 int flags, const char *dev_name, void *data) 260 { 261 return mount_nodev(fs_type, flags, data, ramfs_fill_super); 262 } 263 264 static struct dentry *rootfs_mount(struct file_system_type *fs_type, 265 int flags, const char *dev_name, void *data) 266 { 267 return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); 268 } 269 270 static void ramfs_kill_sb(struct super_block *sb) 271 { 272 kfree(sb->s_fs_info); 273 kill_litter_super(sb); 274 } 275 276 static struct file_system_type ramfs_fs_type = { 277 .name = "ramfs", 278 .mount = ramfs_mount, 279 .kill_sb = ramfs_kill_sb, 280 }; 281 static struct file_system_type rootfs_fs_type = { 282 .name = "rootfs", 283 .mount = rootfs_mount, 284 .kill_sb = kill_litter_super, 285 }; 286 287 static int __init init_ramfs_fs(void) 288 { 289 return register_filesystem(&ramfs_fs_type); 290 } 291 292 static void __exit exit_ramfs_fs(void) 293 { 294 unregister_filesystem(&ramfs_fs_type); 295 } 296 297 module_init(init_ramfs_fs) 298 module_exit(exit_ramfs_fs) 299 300 int __init init_rootfs(void) 301 { 302 int err; 303 304 err = bdi_init(&ramfs_backing_dev_info); 305 if (err) 306 return err; 307 308 err = register_filesystem(&rootfs_fs_type); 309 if (err) 310 bdi_destroy(&ramfs_backing_dev_info); 311 312 return err; 313 } 314 315 MODULE_LICENSE("GPL"); 316