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(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 inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 105 { 106 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev); 107 int error = -ENOSPC; 108 109 if (inode) { 110 d_instantiate(dentry, inode); 111 dget(dentry); /* Extra count - pin the dentry in core */ 112 error = 0; 113 dir->i_mtime = dir->i_ctime = current_time(dir); 114 } 115 return error; 116 } 117 118 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode) 119 { 120 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 121 if (!retval) 122 inc_nlink(dir); 123 return retval; 124 } 125 126 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl) 127 { 128 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 129 } 130 131 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 132 { 133 struct inode *inode; 134 int error = -ENOSPC; 135 136 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 137 if (inode) { 138 int l = strlen(symname)+1; 139 error = page_symlink(inode, symname, l); 140 if (!error) { 141 d_instantiate(dentry, inode); 142 dget(dentry); 143 dir->i_mtime = dir->i_ctime = current_time(dir); 144 } else 145 iput(inode); 146 } 147 return error; 148 } 149 150 static const struct inode_operations ramfs_dir_inode_operations = { 151 .create = ramfs_create, 152 .lookup = simple_lookup, 153 .link = simple_link, 154 .unlink = simple_unlink, 155 .symlink = ramfs_symlink, 156 .mkdir = ramfs_mkdir, 157 .rmdir = simple_rmdir, 158 .mknod = ramfs_mknod, 159 .rename = simple_rename, 160 }; 161 162 /* 163 * Display the mount options in /proc/mounts. 164 */ 165 static int ramfs_show_options(struct seq_file *m, struct dentry *root) 166 { 167 struct ramfs_fs_info *fsi = root->d_sb->s_fs_info; 168 169 if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE) 170 seq_printf(m, ",mode=%o", fsi->mount_opts.mode); 171 return 0; 172 } 173 174 static const struct super_operations ramfs_ops = { 175 .statfs = simple_statfs, 176 .drop_inode = generic_delete_inode, 177 .show_options = ramfs_show_options, 178 }; 179 180 enum ramfs_param { 181 Opt_mode, 182 }; 183 184 const struct fs_parameter_spec ramfs_fs_parameters[] = { 185 fsparam_u32oct("mode", Opt_mode), 186 {} 187 }; 188 189 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 190 { 191 struct fs_parse_result result; 192 struct ramfs_fs_info *fsi = fc->s_fs_info; 193 int opt; 194 195 opt = fs_parse(fc, ramfs_fs_parameters, param, &result); 196 if (opt < 0) { 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 if (opt == -ENOPARAM) 204 opt = 0; 205 return opt; 206 } 207 208 switch (opt) { 209 case Opt_mode: 210 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO; 211 break; 212 } 213 214 return 0; 215 } 216 217 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc) 218 { 219 struct ramfs_fs_info *fsi = sb->s_fs_info; 220 struct inode *inode; 221 222 sb->s_maxbytes = MAX_LFS_FILESIZE; 223 sb->s_blocksize = PAGE_SIZE; 224 sb->s_blocksize_bits = PAGE_SHIFT; 225 sb->s_magic = RAMFS_MAGIC; 226 sb->s_op = &ramfs_ops; 227 sb->s_time_gran = 1; 228 229 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 230 sb->s_root = d_make_root(inode); 231 if (!sb->s_root) 232 return -ENOMEM; 233 234 return 0; 235 } 236 237 static int ramfs_get_tree(struct fs_context *fc) 238 { 239 return get_tree_nodev(fc, ramfs_fill_super); 240 } 241 242 static void ramfs_free_fc(struct fs_context *fc) 243 { 244 kfree(fc->s_fs_info); 245 } 246 247 static const struct fs_context_operations ramfs_context_ops = { 248 .free = ramfs_free_fc, 249 .parse_param = ramfs_parse_param, 250 .get_tree = ramfs_get_tree, 251 }; 252 253 int ramfs_init_fs_context(struct fs_context *fc) 254 { 255 struct ramfs_fs_info *fsi; 256 257 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL); 258 if (!fsi) 259 return -ENOMEM; 260 261 fsi->mount_opts.mode = RAMFS_DEFAULT_MODE; 262 fc->s_fs_info = fsi; 263 fc->ops = &ramfs_context_ops; 264 return 0; 265 } 266 267 static void ramfs_kill_sb(struct super_block *sb) 268 { 269 kfree(sb->s_fs_info); 270 kill_litter_super(sb); 271 } 272 273 static struct file_system_type ramfs_fs_type = { 274 .name = "ramfs", 275 .init_fs_context = ramfs_init_fs_context, 276 .parameters = ramfs_fs_parameters, 277 .kill_sb = ramfs_kill_sb, 278 .fs_flags = FS_USERNS_MOUNT, 279 }; 280 281 static int __init init_ramfs_fs(void) 282 { 283 return register_filesystem(&ramfs_fs_type); 284 } 285 fs_initcall(init_ramfs_fs); 286