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 <asm/uaccess.h> 39 #include "internal.h" 40 41 #define RAMFS_DEFAULT_MODE 0755 42 43 static const struct super_operations ramfs_ops; 44 static const struct inode_operations ramfs_dir_inode_operations; 45 46 static const struct address_space_operations ramfs_aops = { 47 .readpage = simple_readpage, 48 .write_begin = simple_write_begin, 49 .write_end = simple_write_end, 50 .set_page_dirty = __set_page_dirty_no_writeback, 51 }; 52 53 struct inode *ramfs_get_inode(struct super_block *sb, 54 const struct inode *dir, umode_t mode, dev_t dev) 55 { 56 struct inode * inode = new_inode(sb); 57 58 if (inode) { 59 inode->i_ino = get_next_ino(); 60 inode_init_owner(inode, dir, mode); 61 inode->i_mapping->a_ops = &ramfs_aops; 62 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 63 mapping_set_unevictable(inode->i_mapping); 64 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 65 switch (mode & S_IFMT) { 66 default: 67 init_special_inode(inode, mode, dev); 68 break; 69 case S_IFREG: 70 inode->i_op = &ramfs_file_inode_operations; 71 inode->i_fop = &ramfs_file_operations; 72 break; 73 case S_IFDIR: 74 inode->i_op = &ramfs_dir_inode_operations; 75 inode->i_fop = &simple_dir_operations; 76 77 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 78 inc_nlink(inode); 79 break; 80 case S_IFLNK: 81 inode->i_op = &page_symlink_inode_operations; 82 break; 83 } 84 } 85 return inode; 86 } 87 88 /* 89 * File creation. Allocate an inode, and we're done.. 90 */ 91 /* SMP-safe */ 92 static int 93 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 94 { 95 struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev); 96 int error = -ENOSPC; 97 98 if (inode) { 99 d_instantiate(dentry, inode); 100 dget(dentry); /* Extra count - pin the dentry in core */ 101 error = 0; 102 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 103 } 104 return error; 105 } 106 107 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode) 108 { 109 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 110 if (!retval) 111 inc_nlink(dir); 112 return retval; 113 } 114 115 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl) 116 { 117 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 118 } 119 120 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 121 { 122 struct inode *inode; 123 int error = -ENOSPC; 124 125 inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0); 126 if (inode) { 127 int l = strlen(symname)+1; 128 error = page_symlink(inode, symname, l); 129 if (!error) { 130 d_instantiate(dentry, inode); 131 dget(dentry); 132 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 133 } else 134 iput(inode); 135 } 136 return error; 137 } 138 139 static const struct inode_operations ramfs_dir_inode_operations = { 140 .create = ramfs_create, 141 .lookup = simple_lookup, 142 .link = simple_link, 143 .unlink = simple_unlink, 144 .symlink = ramfs_symlink, 145 .mkdir = ramfs_mkdir, 146 .rmdir = simple_rmdir, 147 .mknod = ramfs_mknod, 148 .rename = simple_rename, 149 }; 150 151 static const struct super_operations ramfs_ops = { 152 .statfs = simple_statfs, 153 .drop_inode = generic_delete_inode, 154 .show_options = generic_show_options, 155 }; 156 157 struct ramfs_mount_opts { 158 umode_t mode; 159 }; 160 161 enum { 162 Opt_mode, 163 Opt_err 164 }; 165 166 static const match_table_t tokens = { 167 {Opt_mode, "mode=%o"}, 168 {Opt_err, NULL} 169 }; 170 171 struct ramfs_fs_info { 172 struct ramfs_mount_opts mount_opts; 173 }; 174 175 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) 176 { 177 substring_t args[MAX_OPT_ARGS]; 178 int option; 179 int token; 180 char *p; 181 182 opts->mode = RAMFS_DEFAULT_MODE; 183 184 while ((p = strsep(&data, ",")) != NULL) { 185 if (!*p) 186 continue; 187 188 token = match_token(p, tokens, args); 189 switch (token) { 190 case Opt_mode: 191 if (match_octal(&args[0], &option)) 192 return -EINVAL; 193 opts->mode = option & S_IALLUGO; 194 break; 195 /* 196 * We might like to report bad mount options here; 197 * but traditionally ramfs has ignored all mount options, 198 * and as it is used as a !CONFIG_SHMEM simple substitute 199 * for tmpfs, better continue to ignore other mount options. 200 */ 201 } 202 } 203 204 return 0; 205 } 206 207 int ramfs_fill_super(struct super_block *sb, void *data, int silent) 208 { 209 struct ramfs_fs_info *fsi; 210 struct inode *inode; 211 int err; 212 213 save_mount_options(sb, data); 214 215 fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); 216 sb->s_fs_info = fsi; 217 if (!fsi) 218 return -ENOMEM; 219 220 err = ramfs_parse_options(data, &fsi->mount_opts); 221 if (err) 222 return err; 223 224 sb->s_maxbytes = MAX_LFS_FILESIZE; 225 sb->s_blocksize = PAGE_CACHE_SIZE; 226 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 227 sb->s_magic = RAMFS_MAGIC; 228 sb->s_op = &ramfs_ops; 229 sb->s_time_gran = 1; 230 231 inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0); 232 sb->s_root = d_make_root(inode); 233 if (!sb->s_root) 234 return -ENOMEM; 235 236 return 0; 237 } 238 239 struct dentry *ramfs_mount(struct file_system_type *fs_type, 240 int flags, const char *dev_name, void *data) 241 { 242 return mount_nodev(fs_type, flags, data, ramfs_fill_super); 243 } 244 245 static void ramfs_kill_sb(struct super_block *sb) 246 { 247 kfree(sb->s_fs_info); 248 kill_litter_super(sb); 249 } 250 251 static struct file_system_type ramfs_fs_type = { 252 .name = "ramfs", 253 .mount = ramfs_mount, 254 .kill_sb = ramfs_kill_sb, 255 .fs_flags = FS_USERNS_MOUNT, 256 }; 257 258 int __init init_ramfs_fs(void) 259 { 260 static unsigned long once; 261 262 if (test_and_set_bit(0, &once)) 263 return 0; 264 return register_filesystem(&ramfs_fs_type); 265 } 266 fs_initcall(init_ramfs_fs); 267