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 "internal.h" 42 43 struct ramfs_mount_opts { 44 umode_t mode; 45 }; 46 47 struct ramfs_fs_info { 48 struct ramfs_mount_opts mount_opts; 49 }; 50 51 #define RAMFS_DEFAULT_MODE 0755 52 53 static const struct super_operations ramfs_ops; 54 static const struct inode_operations ramfs_dir_inode_operations; 55 56 static const struct address_space_operations ramfs_aops = { 57 .readpage = simple_readpage, 58 .write_begin = simple_write_begin, 59 .write_end = simple_write_end, 60 .set_page_dirty = __set_page_dirty_no_writeback, 61 }; 62 63 struct inode *ramfs_get_inode(struct super_block *sb, 64 const struct inode *dir, umode_t mode, dev_t dev) 65 { 66 struct inode * inode = new_inode(sb); 67 68 if (inode) { 69 inode->i_ino = get_next_ino(); 70 inode_init_owner(&init_user_ns, inode, dir, mode); 71 inode->i_mapping->a_ops = &ramfs_aops; 72 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 73 mapping_set_unevictable(inode->i_mapping); 74 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); 75 switch (mode & S_IFMT) { 76 default: 77 init_special_inode(inode, mode, dev); 78 break; 79 case S_IFREG: 80 inode->i_op = &ramfs_file_inode_operations; 81 inode->i_fop = &ramfs_file_operations; 82 break; 83 case S_IFDIR: 84 inode->i_op = &ramfs_dir_inode_operations; 85 inode->i_fop = &simple_dir_operations; 86 87 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 88 inc_nlink(inode); 89 break; 90 case S_IFLNK: 91 inode->i_op = &page_symlink_inode_operations; 92 inode_nohighmem(inode); 93 break; 94 } 95 } 96 return inode; 97 } 98 99 /* 100 * File creation. Allocate an inode, and we're done.. 101 */ 102 /* SMP-safe */ 103 static int 104 ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir, 105 struct dentry *dentry, umode_t mode, dev_t dev) 106 { 107 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev); 108 int error = -ENOSPC; 109 110 if (inode) { 111 d_instantiate(dentry, inode); 112 dget(dentry); /* Extra count - pin the dentry in core */ 113 error = 0; 114 dir->i_mtime = dir->i_ctime = current_time(dir); 115 } 116 return error; 117 } 118 119 static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir, 120 struct dentry *dentry, umode_t mode) 121 { 122 int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0); 123 if (!retval) 124 inc_nlink(dir); 125 return retval; 126 } 127 128 static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir, 129 struct dentry *dentry, umode_t mode, bool excl) 130 { 131 return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0); 132 } 133 134 static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir, 135 struct dentry *dentry, const char *symname) 136 { 137 struct inode *inode; 138 int error = -ENOSPC; 139 140 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 141 if (inode) { 142 int l = strlen(symname)+1; 143 error = page_symlink(inode, symname, l); 144 if (!error) { 145 d_instantiate(dentry, inode); 146 dget(dentry); 147 dir->i_mtime = dir->i_ctime = current_time(dir); 148 } else 149 iput(inode); 150 } 151 return error; 152 } 153 154 static const struct inode_operations ramfs_dir_inode_operations = { 155 .create = ramfs_create, 156 .lookup = simple_lookup, 157 .link = simple_link, 158 .unlink = simple_unlink, 159 .symlink = ramfs_symlink, 160 .mkdir = ramfs_mkdir, 161 .rmdir = simple_rmdir, 162 .mknod = ramfs_mknod, 163 .rename = simple_rename, 164 }; 165 166 /* 167 * Display the mount options in /proc/mounts. 168 */ 169 static int ramfs_show_options(struct seq_file *m, struct dentry *root) 170 { 171 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info; 172 173 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE) 174 seq_printf(m, ",mode=%o", fsi->mount_opts.mode); 175 return 0; 176 } 177 178 static const struct super_operations ramfs_ops = { 179 .statfs = simple_statfs, 180 .drop_inode = generic_delete_inode, 181 .show_options = ramfs_show_options, 182 }; 183 184 enum ramfs_param { 185 Opt_mode, 186 }; 187 188 const struct fs_parameter_spec ramfs_fs_parameters[] = { 189 fsparam_u32oct("mode", Opt_mode), 190 {} 191 }; 192 193 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 194 { 195 struct fs_parse_result result; 196 struct ramfs_fs_info *fsi = fc->s_fs_info; 197 int opt; 198 199 opt = fs_parse(fc, ramfs_fs_parameters, param, &result); 200 if (opt < 0) { 201 /* 202 * We might like to report bad mount options here; 203 * but traditionally ramfs has ignored all mount options, 204 * and as it is used as a !CONFIG_SHMEM simple substitute 205 * for tmpfs, better continue to ignore other mount options. 206 */ 207 if (opt == -ENOPARAM) 208 opt = 0; 209 return opt; 210 } 211 212 switch (opt) { 213 case Opt_mode: 214 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO; 215 break; 216 } 217 218 return 0; 219 } 220 221 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc) 222 { 223 struct ramfs_fs_info *fsi = sb->s_fs_info; 224 struct inode *inode; 225 226 sb->s_maxbytes = MAX_LFS_FILESIZE; 227 sb->s_blocksize = PAGE_SIZE; 228 sb->s_blocksize_bits = PAGE_SHIFT; 229 sb->s_magic = RAMFS_MAGIC; 230 sb->s_op = &ramfs_ops; 231 sb->s_time_gran = 1; 232 233 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 234 sb->s_root = d_make_root(inode); 235 if (!sb->s_root) 236 return -ENOMEM; 237 238 return 0; 239 } 240 241 static int ramfs_get_tree(struct fs_context *fc) 242 { 243 return get_tree_nodev(fc, ramfs_fill_super); 244 } 245 246 static void ramfs_free_fc(struct fs_context *fc) 247 { 248 kfree(fc->s_fs_info); 249 } 250 251 static const struct fs_context_operations ramfs_context_ops = { 252 .free = ramfs_free_fc, 253 .parse_param = ramfs_parse_param, 254 .get_tree = ramfs_get_tree, 255 }; 256 257 int ramfs_init_fs_context(struct fs_context *fc) 258 { 259 struct ramfs_fs_info *fsi; 260 261 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL); 262 if (!fsi) 263 return -ENOMEM; 264 265 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE; 266 fc->s_fs_info = fsi; 267 fc->ops = &ramfs_context_ops; 268 return 0; 269 } 270 271 static void ramfs_kill_sb(struct super_block *sb) 272 { 273 kfree(sb->s_fs_info); 274 kill_litter_super(sb); 275 } 276 277 static struct file_system_type ramfs_fs_type = { 278 .name = "ramfs", 279 .init_fs_context = ramfs_init_fs_context, 280 .parameters = ramfs_fs_parameters, 281 .kill_sb = ramfs_kill_sb, 282 .fs_flags = FS_USERNS_MOUNT, 283 }; 284 285 static int __init init_ramfs_fs(void) 286 { 287 return register_filesystem(&ramfs_fs_type); 288 } 289 fs_initcall(init_ramfs_fs); 290