fs/ramfs/inode.c

   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/module.h>
  27 #include <linux/fs.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/highmem.h>
  30 #include <linux/time.h>
  31 #include <linux/init.h>
  32 #include <linux/string.h>
  33 #include <linux/backing-dev.h>
  34 #include <linux/ramfs.h>
  35 #include <linux/sched.h>
  36 #include <linux/parser.h>
  37 #include <linux/magic.h>
  38 #include <linux/slab.h>
  39 #include <asm/uaccess.h>
  40 #include "internal.h"
  41
  42 #define RAMFS_DEFAULT_MODE      0755
  43
  44 static const struct super_operations ramfs_ops;
  45 static const struct inode_operations ramfs_dir_inode_operations;
  46
  47 static struct backing_dev_info ramfs_backing_dev_info = {
  48         .name           = "ramfs",
  49         .ra_pages       = 0,    /* No readahead */
  50         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK |
  51                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
  52                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
  53 };
  54
  55 struct inode *ramfs_get_inode(struct super_block *sb,
  56                                 const struct inode *dir, int mode, dev_t dev)
  57 {
  58         struct inode * inode = new_inode(sb);
  59
  60         if (inode) {
  61                 inode->i_ino = get_next_ino();
  62                 inode_init_owner(inode, dir, mode);
  63                 inode->i_mapping->a_ops = &ramfs_aops;
  64                 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
  65                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  66                 mapping_set_unevictable(inode->i_mapping);
  67                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  68                 switch (mode & S_IFMT) {
  69                 default:
  70                         init_special_inode(inode, mode, dev);
  71                         break;
  72                 case S_IFREG:
  73                         inode->i_op = &ramfs_file_inode_operations;
  74                         inode->i_fop = &ramfs_file_operations;
  75                         break;
  76                 case S_IFDIR:
  77                         inode->i_op = &ramfs_dir_inode_operations;
  78                         inode->i_fop = &simple_dir_operations;
  79
  80                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  81                         inc_nlink(inode);
  82                         break;
  83                 case S_IFLNK:
  84                         inode->i_op = &page_symlink_inode_operations;
  85                         break;
  86                 }
  87         }
  88         return inode;
  89 }
  90
  91 /*
  92  * File creation. Allocate an inode, and we're done..
  93  */
  94 /* SMP-safe */
  95 static int
  96 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  97 {
  98         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
  99         int error = -ENOSPC;
 100
 101         if (inode) {
 102                 d_instantiate(dentry, inode);
 103                 dget(dentry);   /* Extra count - pin the dentry in core */
 104                 error = 0;
 105                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 106         }
 107         return error;
 108 }
 109
 110 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 111 {
 112         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 113         if (!retval)
 114                 inc_nlink(dir);
 115         return retval;
 116 }
 117
 118 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
 119 {
 120         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 121 }
 122
 123 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 124 {
 125         struct inode *inode;
 126         int error = -ENOSPC;
 127
 128         inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
 129         if (inode) {
 130                 int l = strlen(symname)+1;
 131                 error = page_symlink(inode, symname, l);
 132                 if (!error) {
 133                         d_instantiate(dentry, inode);
 134                         dget(dentry);
 135                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 136                 } else
 137                         iput(inode);
 138         }
 139         return error;
 140 }
 141
 142 static const struct inode_operations ramfs_dir_inode_operations = {
 143         .create         = ramfs_create,
 144         .lookup         = simple_lookup,
 145         .link           = simple_link,
 146         .unlink         = simple_unlink,
 147         .symlink        = ramfs_symlink,
 148         .mkdir          = ramfs_mkdir,
 149         .rmdir          = simple_rmdir,
 150         .mknod          = ramfs_mknod,
 151         .rename         = simple_rename,
 152 };
 153
 154 static const struct super_operations ramfs_ops = {
 155         .statfs         = simple_statfs,
 156         .drop_inode     = generic_delete_inode,
 157         .show_options   = generic_show_options,
 158 };
 159
 160 struct ramfs_mount_opts {
 161         umode_t mode;
 162 };
 163
 164 enum {
 165         Opt_mode,
 166         Opt_err
 167 };
 168
 169 static const match_table_t tokens = {
 170         {Opt_mode, "mode=%o"},
 171         {Opt_err, NULL}
 172 };
 173
 174 struct ramfs_fs_info {
 175         struct ramfs_mount_opts mount_opts;
 176 };
 177
 178 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
 179 {
 180         substring_t args[MAX_OPT_ARGS];
 181         int option;
 182         int token;
 183         char *p;
 184
 185         opts->mode = RAMFS_DEFAULT_MODE;
 186
 187         while ((p = strsep(&data, ",")) != NULL) {
 188                 if (!*p)
 189                         continue;
 190
 191                 token = match_token(p, tokens, args);
 192                 switch (token) {
 193                 case Opt_mode:
 194                         if (match_octal(&args[0], &option))
 195                                 return -EINVAL;
 196                         opts->mode = option & S_IALLUGO;
 197                         break;
 198                 /*
 199                  * We might like to report bad mount options here;
 200                  * but traditionally ramfs has ignored all mount options,
 201                  * and as it is used as a !CONFIG_SHMEM simple substitute
 202                  * for tmpfs, better continue to ignore other mount options.
 203                  */
 204                 }
 205         }
 206
 207         return 0;
 208 }
 209
 210 int ramfs_fill_super(struct super_block *sb, void *data, int silent)
 211 {
 212         struct ramfs_fs_info *fsi;
 213         struct inode *inode = NULL;
 214         struct dentry *root;
 215         int err;
 216
 217         save_mount_options(sb, data);
 218
 219         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
 220         sb->s_fs_info = fsi;
 221         if (!fsi) {
 222                 err = -ENOMEM;
 223                 goto fail;
 224         }
 225
 226         err = ramfs_parse_options(data, &fsi->mount_opts);
 227         if (err)
 228                 goto fail;
 229
 230         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 231         sb->s_blocksize         = PAGE_CACHE_SIZE;
 232         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 233         sb->s_magic             = RAMFS_MAGIC;
 234         sb->s_op                = &ramfs_ops;
 235         sb->s_time_gran         = 1;
 236
 237         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
 238         if (!inode) {
 239                 err = -ENOMEM;
 240                 goto fail;
 241         }
 242
 243         root = d_alloc_root(inode);
 244         sb->s_root = root;
 245         if (!root) {
 246                 err = -ENOMEM;
 247                 goto fail;
 248         }
 249
 250         return 0;
 251 fail:
 252         kfree(fsi);
 253         sb->s_fs_info = NULL;
 254         iput(inode);
 255         return err;
 256 }
 257
 258 struct dentry *ramfs_mount(struct file_system_type *fs_type,
 259         int flags, const char *dev_name, void *data)
 260 {
 261         return mount_nodev(fs_type, flags, data, ramfs_fill_super);
 262 }
 263
 264 static struct dentry *rootfs_mount(struct file_system_type *fs_type,
 265         int flags, const char *dev_name, void *data)
 266 {
 267         return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
 268 }
 269
 270 static void ramfs_kill_sb(struct super_block *sb)
 271 {
 272         kfree(sb->s_fs_info);
 273         kill_litter_super(sb);
 274 }
 275
 276 static struct file_system_type ramfs_fs_type = {
 277         .name           = "ramfs",
 278         .mount          = ramfs_mount,
 279         .kill_sb        = ramfs_kill_sb,
 280 };
 281 static struct file_system_type rootfs_fs_type = {
 282         .name           = "rootfs",
 283         .mount          = rootfs_mount,
 284         .kill_sb        = kill_litter_super,
 285 };
 286
 287 static int __init init_ramfs_fs(void)
 288 {
 289         return register_filesystem(&ramfs_fs_type);
 290 }
 291
 292 static void __exit exit_ramfs_fs(void)
 293 {
 294         unregister_filesystem(&ramfs_fs_type);
 295 }
 296
 297 module_init(init_ramfs_fs)
 298 module_exit(exit_ramfs_fs)
 299
 300 int __init init_rootfs(void)
 301 {
 302         int err;
 303
 304         err = bdi_init(&ramfs_backing_dev_info);
 305         if (err)
 306                 return err;
 307
 308         err = register_filesystem(&rootfs_fs_type);
 309         if (err)
 310                 bdi_destroy(&ramfs_backing_dev_info);
 311
 312         return err;
 313 }
 314
 315 MODULE_LICENSE("GPL");