| 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 struct backing_dev_info ramfs_backing_dev_info = { |
| 47 | .name = "ramfs", |
| 48 | .ra_pages = 0, /* No readahead */ |
| 49 | .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | |
| 50 | BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY | |
| 51 | BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP, |
| 52 | }; |
| 53 | |
| 54 | struct inode *ramfs_get_inode(struct super_block *sb, |
| 55 | const struct inode *dir, umode_t mode, dev_t dev) |
| 56 | { |
| 57 | struct inode * inode = new_inode(sb); |
| 58 | |
| 59 | if (inode) { |
| 60 | inode->i_ino = get_next_ino(); |
| 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, umode_t 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, umode_t 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, umode_t mode, bool excl) |
| 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; |
| 213 | int err; |
| 214 | |
| 215 | save_mount_options(sb, data); |
| 216 | |
| 217 | fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); |
| 218 | sb->s_fs_info = fsi; |
| 219 | if (!fsi) |
| 220 | return -ENOMEM; |
| 221 | |
| 222 | err = ramfs_parse_options(data, &fsi->mount_opts); |
| 223 | if (err) |
| 224 | return err; |
| 225 | |
| 226 | sb->s_maxbytes = MAX_LFS_FILESIZE; |
| 227 | sb->s_blocksize = PAGE_CACHE_SIZE; |
| 228 | sb->s_blocksize_bits = PAGE_CACHE_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 | struct dentry *ramfs_mount(struct file_system_type *fs_type, |
| 242 | int flags, const char *dev_name, void *data) |
| 243 | { |
| 244 | return mount_nodev(fs_type, flags, data, ramfs_fill_super); |
| 245 | } |
| 246 | |
| 247 | static struct dentry *rootfs_mount(struct file_system_type *fs_type, |
| 248 | int flags, const char *dev_name, void *data) |
| 249 | { |
| 250 | return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); |
| 251 | } |
| 252 | |
| 253 | static void ramfs_kill_sb(struct super_block *sb) |
| 254 | { |
| 255 | kfree(sb->s_fs_info); |
| 256 | kill_litter_super(sb); |
| 257 | } |
| 258 | |
| 259 | static struct file_system_type ramfs_fs_type = { |
| 260 | .name = "ramfs", |
| 261 | .mount = ramfs_mount, |
| 262 | .kill_sb = ramfs_kill_sb, |
| 263 | }; |
| 264 | static struct file_system_type rootfs_fs_type = { |
| 265 | .name = "rootfs", |
| 266 | .mount = rootfs_mount, |
| 267 | .kill_sb = kill_litter_super, |
| 268 | }; |
| 269 | |
| 270 | static int __init init_ramfs_fs(void) |
| 271 | { |
| 272 | return register_filesystem(&ramfs_fs_type); |
| 273 | } |
| 274 | module_init(init_ramfs_fs) |
| 275 | |
| 276 | int __init init_rootfs(void) |
| 277 | { |
| 278 | int err; |
| 279 | |
| 280 | err = bdi_init(&ramfs_backing_dev_info); |
| 281 | if (err) |
| 282 | return err; |
| 283 | |
| 284 | err = register_filesystem(&rootfs_fs_type); |
| 285 | if (err) |
| 286 | bdi_destroy(&ramfs_backing_dev_info); |
| 287 | |
| 288 | return err; |
| 289 | } |