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/fs.h> 27 #include <linux/pagemap.h> 28 #include <linux/highmem.h> 29 #include <linux/time.h> 30 #include <linux/init.h> 31 #include <linux/string.h> 32 #include <linux/backing-dev.h> 33 #include <linux/ramfs.h> 34 #include <linux/sched.h> 35 #include <linux/parser.h> 36 #include <linux/magic.h> 37 #include <linux/slab.h> 38 #include <linux/uaccess.h> 39 #include <linux/fs_context.h> 40 #include <linux/fs_parser.h> 41 #include <linux/seq_file.h> 42 #include "internal.h" 43 44 struct ramfs_mount_opts { 45 umode_t mode; 46 }; 47 48 struct ramfs_fs_info { 49 struct ramfs_mount_opts mount_opts; 50 }; 51 52 #define RAMFS_DEFAULT_MODE 0755 53 54 static const struct super_operations ramfs_ops; 55 static const struct inode_operations ramfs_dir_inode_operations; 56 57 struct inode *ramfs_get_inode(struct super_block *sb, 58 const struct inode *dir, umode_t mode, dev_t dev) 59 { 60 struct inode * inode = new_inode(sb); 61 62 if (inode) { 63 inode->i_ino = get_next_ino(); 64 inode_init_owner(&nop_mnt_idmap, inode, dir, mode); 65 inode->i_mapping->a_ops = &ram_aops; 66 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 67 mapping_set_unevictable(inode->i_mapping); 68 simple_inode_init_ts(inode); 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 inode_nohighmem(inode); 87 break; 88 } 89 } 90 return inode; 91 } 92 93 /* 94 * File creation. Allocate an inode, and we're done.. 95 */ 96 /* SMP-safe */ 97 static int 98 ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir, 99 struct dentry *dentry, umode_t mode, dev_t dev) 100 { 101 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev); 102 int error = -ENOSPC; 103 104 if (inode) { 105 d_instantiate(dentry, inode); 106 dget(dentry); /* Extra count - pin the dentry in core */ 107 error = 0; 108 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); 109 } 110 return error; 111 } 112 113 static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir, 114 struct dentry *dentry, umode_t mode) 115 { 116 int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0); 117 if (!retval) 118 inc_nlink(dir); 119 return retval; 120 } 121 122 static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir, 123 struct dentry *dentry, umode_t mode, bool excl) 124 { 125 return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0); 126 } 127 128 static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir, 129 struct dentry *dentry, const char *symname) 130 { 131 struct inode *inode; 132 int error = -ENOSPC; 133 134 inode = ramfs_get_inode(dir->i_sb, dir, 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 d_instantiate(dentry, inode); 140 dget(dentry); 141 inode_set_mtime_to_ts(dir, 142 inode_set_ctime_current(dir)); 143 } else 144 iput(inode); 145 } 146 return error; 147 } 148 149 static int ramfs_tmpfile(struct mnt_idmap *idmap, 150 struct inode *dir, struct file *file, umode_t mode) 151 { 152 struct inode *inode; 153 154 inode = ramfs_get_inode(dir->i_sb, dir, mode, 0); 155 if (!inode) 156 return -ENOSPC; 157 d_tmpfile(file, inode); 158 return finish_open_simple(file, 0); 159 } 160 161 static const struct inode_operations ramfs_dir_inode_operations = { 162 .create = ramfs_create, 163 .lookup = simple_lookup, 164 .link = simple_link, 165 .unlink = simple_unlink, 166 .symlink = ramfs_symlink, 167 .mkdir = ramfs_mkdir, 168 .rmdir = simple_rmdir, 169 .mknod = ramfs_mknod, 170 .rename = simple_rename, 171 .tmpfile = ramfs_tmpfile, 172 }; 173 174 /* 175 * Display the mount options in /proc/mounts. 176 */ 177 static int ramfs_show_options(struct seq_file *m, struct dentry *root) 178 { 179 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info; 180 181 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE) 182 seq_printf(m, ",mode=%o", fsi->mount_opts.mode); 183 return 0; 184 } 185 186 static const struct super_operations ramfs_ops = { 187 .statfs = simple_statfs, 188 .drop_inode = generic_delete_inode, 189 .show_options = ramfs_show_options, 190 }; 191 192 enum ramfs_param { 193 Opt_mode, 194 }; 195 196 const struct fs_parameter_spec ramfs_fs_parameters[] = { 197 fsparam_u32oct("mode", Opt_mode), 198 {} 199 }; 200 201 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 202 { 203 struct fs_parse_result result; 204 struct ramfs_fs_info *fsi = fc->s_fs_info; 205 int opt; 206 207 opt = fs_parse(fc, ramfs_fs_parameters, param, &result); 208 if (opt == -ENOPARAM) { 209 opt = vfs_parse_fs_param_source(fc, param); 210 if (opt != -ENOPARAM) 211 return opt; 212 /* 213 * We might like to report bad mount options here; 214 * but traditionally ramfs has ignored all mount options, 215 * and as it is used as a !CONFIG_SHMEM simple substitute 216 * for tmpfs, better continue to ignore other mount options. 217 */ 218 return 0; 219 } 220 if (opt < 0) 221 return opt; 222 223 switch (opt) { 224 case Opt_mode: 225 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO; 226 break; 227 } 228 229 return 0; 230 } 231 232 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc) 233 { 234 struct ramfs_fs_info *fsi = sb->s_fs_info; 235 struct inode *inode; 236 237 sb->s_maxbytes = MAX_LFS_FILESIZE; 238 sb->s_blocksize = PAGE_SIZE; 239 sb->s_blocksize_bits = PAGE_SHIFT; 240 sb->s_magic = RAMFS_MAGIC; 241 sb->s_op = &ramfs_ops; 242 sb->s_time_gran = 1; 243 244 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 245 sb->s_root = d_make_root(inode); 246 if (!sb->s_root) 247 return -ENOMEM; 248 249 return 0; 250 } 251 252 static int ramfs_get_tree(struct fs_context *fc) 253 { 254 return get_tree_nodev(fc, ramfs_fill_super); 255 } 256 257 static void ramfs_free_fc(struct fs_context *fc) 258 { 259 kfree(fc->s_fs_info); 260 } 261 262 static const struct fs_context_operations ramfs_context_ops = { 263 .free = ramfs_free_fc, 264 .parse_param = ramfs_parse_param, 265 .get_tree = ramfs_get_tree, 266 }; 267 268 int ramfs_init_fs_context(struct fs_context *fc) 269 { 270 struct ramfs_fs_info *fsi; 271 272 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL); 273 if (!fsi) 274 return -ENOMEM; 275 276 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE; 277 fc->s_fs_info = fsi; 278 fc->ops = &ramfs_context_ops; 279 return 0; 280 } 281 282 void ramfs_kill_sb(struct super_block *sb) 283 { 284 kfree(sb->s_fs_info); 285 kill_litter_super(sb); 286 } 287 288 static struct file_system_type ramfs_fs_type = { 289 .name = "ramfs", 290 .init_fs_context = ramfs_init_fs_context, 291 .parameters = ramfs_fs_parameters, 292 .kill_sb = ramfs_kill_sb, 293 .fs_flags = FS_USERNS_MOUNT, 294 }; 295 296 static int __init init_ramfs_fs(void) 297 { 298 return register_filesystem(&ramfs_fs_type); 299 } 300 fs_initcall(init_ramfs_fs); 301