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_init_owner(inode, dir, mode); 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, dir, mode, dev); 98 int error = -ENOSPC; 99 100 if (inode) { 101 d_instantiate(dentry, inode); 102 dget(dentry); /* Extra count - pin the dentry in core */ 103 error = 0; 104 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 105 } 106 return error; 107 } 108 109 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) 110 { 111 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 112 if (!retval) 113 inc_nlink(dir); 114 return retval; 115 } 116 117 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) 118 { 119 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 120 } 121 122 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 123 { 124 struct inode *inode; 125 int error = -ENOSPC; 126 127 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 128 if (inode) { 129 int l = strlen(symname)+1; 130 error = page_symlink(inode, symname, l); 131 if (!error) { 132 d_instantiate(dentry, inode); 133 dget(dentry); 134 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 135 } else 136 iput(inode); 137 } 138 return error; 139 } 140 141 static const struct inode_operations ramfs_dir_inode_operations = { 142 .create = ramfs_create, 143 .lookup = simple_lookup, 144 .link = simple_link, 145 .unlink = simple_unlink, 146 .symlink = ramfs_symlink, 147 .mkdir = ramfs_mkdir, 148 .rmdir = simple_rmdir, 149 .mknod = ramfs_mknod, 150 .rename = simple_rename, 151 }; 152 153 static const struct super_operations ramfs_ops = { 154 .statfs = simple_statfs, 155 .drop_inode = generic_delete_inode, 156 .show_options = generic_show_options, 157 }; 158 159 struct ramfs_mount_opts { 160 umode_t mode; 161 }; 162 163 enum { 164 Opt_mode, 165 Opt_err 166 }; 167 168 static const match_table_t tokens = { 169 {Opt_mode, "mode=%o"}, 170 {Opt_err, NULL} 171 }; 172 173 struct ramfs_fs_info { 174 struct ramfs_mount_opts mount_opts; 175 }; 176 177 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) 178 { 179 substring_t args[MAX_OPT_ARGS]; 180 int option; 181 int token; 182 char *p; 183 184 opts->mode = RAMFS_DEFAULT_MODE; 185 186 while ((p = strsep(&data, ",")) != NULL) { 187 if (!*p) 188 continue; 189 190 token = match_token(p, tokens, args); 191 switch (token) { 192 case Opt_mode: 193 if (match_octal(&args[0], &option)) 194 return -EINVAL; 195 opts->mode = option & S_IALLUGO; 196 break; 197 /* 198 * We might like to report bad mount options here; 199 * but traditionally ramfs has ignored all mount options, 200 * and as it is used as a !CONFIG_SHMEM simple substitute 201 * for tmpfs, better continue to ignore other mount options. 202 */ 203 } 204 } 205 206 return 0; 207 } 208 209 int ramfs_fill_super(struct super_block *sb, void *data, int silent) 210 { 211 struct ramfs_fs_info *fsi; 212 struct inode *inode = NULL; 213 struct dentry *root; 214 int err; 215 216 save_mount_options(sb, data); 217 218 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); 219 sb->s_fs_info = fsi; 220 if (!fsi) { 221 err = -ENOMEM; 222 goto fail; 223 } 224 225 err = ramfs_parse_options(data, &fsi->mount_opts); 226 if (err) 227 goto fail; 228 229 sb->s_maxbytes = MAX_LFS_FILESIZE; 230 sb->s_blocksize = PAGE_CACHE_SIZE; 231 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 232 sb->s_magic = RAMFS_MAGIC; 233 sb->s_op = &ramfs_ops; 234 sb->s_time_gran = 1; 235 236 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 237 if (!inode) { 238 err = -ENOMEM; 239 goto fail; 240 } 241 242 root = d_alloc_root(inode); 243 sb->s_root = root; 244 if (!root) { 245 err = -ENOMEM; 246 goto fail; 247 } 248 249 return 0; 250 fail: 251 kfree(fsi); 252 sb->s_fs_info = NULL; 253 iput(inode); 254 return err; 255 } 256 257 int ramfs_get_sb(struct file_system_type *fs_type, 258 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 259 { 260 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt); 261 } 262 263 static int rootfs_get_sb(struct file_system_type *fs_type, 264 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 265 { 266 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super, 267 mnt); 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 .get_sb = ramfs_get_sb, 279 .kill_sb = ramfs_kill_sb, 280 }; 281 static struct file_system_type rootfs_fs_type = { 282 .name = "rootfs", 283 .get_sb = rootfs_get_sb, 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