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 <asm/uaccess.h>
  38 #include "internal.h"
  39
  40 /* some random number */
  41 #define RAMFS_MAGIC     0x858458f6
  42
  43 #define RAMFS_DEFAULT_MODE      0755
  44
  45 static const struct super_operations ramfs_ops;
  46 static const struct inode_operations ramfs_dir_inode_operations;
  47
  48 static struct backing_dev_info ramfs_backing_dev_info = {
  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, int mode, dev_t dev)
  56 {
  57         struct inode * inode = new_inode(sb);
  58
  59         if (inode) {
  60                 inode->i_mode = mode;
  61                 inode->i_uid = current_fsuid();
  62                 inode->i_gid = current_fsgid();
  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, mode, dev);
  99         int error = -ENOSPC;
 100
 101         if (inode) {
 102                 if (dir->i_mode & S_ISGID) {
 103                         inode->i_gid = dir->i_gid;
 104                         if (S_ISDIR(mode))
 105                                 inode->i_mode |= S_ISGID;
 106                 }
 107                 d_instantiate(dentry, inode);
 108                 dget(dentry);   /* Extra count - pin the dentry in core */
 109                 error = 0;
 110                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 111         }
 112         return error;
 113 }
 114
 115 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 116 {
 117         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 118         if (!retval)
 119                 inc_nlink(dir);
 120         return retval;
 121 }
 122
 123 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
 124 {
 125         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 126 }
 127
 128 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 129 {
 130         struct inode *inode;
 131         int error = -ENOSPC;
 132
 133         inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
 134         if (inode) {
 135                 int l = strlen(symname)+1;
 136                 error = page_symlink(inode, symname, l);
 137                 if (!error) {
 138                         if (dir->i_mode & S_ISGID)
 139                                 inode->i_gid = dir->i_gid;
 140                         d_instantiate(dentry, inode);
 141                         dget(dentry);
 142                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 143                 } else
 144                         iput(inode);
 145         }
 146         return error;
 147 }
 148
 149 static const struct inode_operations ramfs_dir_inode_operations = {
 150         .create         = ramfs_create,
 151         .lookup         = simple_lookup,
 152         .link           = simple_link,
 153         .unlink         = simple_unlink,
 154         .symlink        = ramfs_symlink,
 155         .mkdir          = ramfs_mkdir,
 156         .rmdir          = simple_rmdir,
 157         .mknod          = ramfs_mknod,
 158         .rename         = simple_rename,
 159 };
 160
 161 static const struct super_operations ramfs_ops = {
 162         .statfs         = simple_statfs,
 163         .drop_inode     = generic_delete_inode,
 164         .show_options   = generic_show_options,
 165 };
 166
 167 struct ramfs_mount_opts {
 168         umode_t mode;
 169 };
 170
 171 enum {
 172         Opt_mode,
 173         Opt_err
 174 };
 175
 176 static const match_table_t tokens = {
 177         {Opt_mode, "mode=%o"},
 178         {Opt_err, NULL}
 179 };
 180
 181 struct ramfs_fs_info {
 182         struct ramfs_mount_opts mount_opts;
 183 };
 184
 185 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
 186 {
 187         substring_t args[MAX_OPT_ARGS];
 188         int option;
 189         int token;
 190         char *p;
 191
 192         opts->mode = RAMFS_DEFAULT_MODE;
 193
 194         while ((p = strsep(&data, ",")) != NULL) {
 195                 if (!*p)
 196                         continue;
 197
 198                 token = match_token(p, tokens, args);
 199                 switch (token) {
 200                 case Opt_mode:
 201                         if (match_octal(&args[0], &option))
 202                                 return -EINVAL;
 203                         opts->mode = option & S_IALLUGO;
 204                         break;
 205                 default:
 206                         printk(KERN_ERR "ramfs: bad mount option: %s\n", p);
 207                         return -EINVAL;
 208                 }
 209         }
 210
 211         return 0;
 212 }
 213
 214 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
 215 {
 216         struct ramfs_fs_info *fsi;
 217         struct inode *inode = NULL;
 218         struct dentry *root;
 219         int err;
 220
 221         save_mount_options(sb, data);
 222
 223         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
 224         sb->s_fs_info = fsi;
 225         if (!fsi) {
 226                 err = -ENOMEM;
 227                 goto fail;
 228         }
 229
 230         err = ramfs_parse_options(data, &fsi->mount_opts);
 231         if (err)
 232                 goto fail;
 233
 234         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 235         sb->s_blocksize         = PAGE_CACHE_SIZE;
 236         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 237         sb->s_magic             = RAMFS_MAGIC;
 238         sb->s_op                = &ramfs_ops;
 239         sb->s_time_gran         = 1;
 240
 241         inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0);
 242         if (!inode) {
 243                 err = -ENOMEM;
 244                 goto fail;
 245         }
 246
 247         root = d_alloc_root(inode);
 248         sb->s_root = root;
 249         if (!root) {
 250                 err = -ENOMEM;
 251                 goto fail;
 252         }
 253
 254         return 0;
 255 fail:
 256         kfree(fsi);
 257         sb->s_fs_info = NULL;
 258         iput(inode);
 259         return err;
 260 }
 261
 262 int ramfs_get_sb(struct file_system_type *fs_type,
 263         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 264 {
 265         return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
 266 }
 267
 268 static int rootfs_get_sb(struct file_system_type *fs_type,
 269         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 270 {
 271         return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
 272                             mnt);
 273 }
 274
 275 static void ramfs_kill_sb(struct super_block *sb)
 276 {
 277         kfree(sb->s_fs_info);
 278         kill_litter_super(sb);
 279 }
 280
 281 static struct file_system_type ramfs_fs_type = {
 282         .name           = "ramfs",
 283         .get_sb         = ramfs_get_sb,
 284         .kill_sb        = ramfs_kill_sb,
 285 };
 286 static struct file_system_type rootfs_fs_type = {
 287         .name           = "rootfs",
 288         .get_sb         = rootfs_get_sb,
 289         .kill_sb        = kill_litter_super,
 290 };
 291
 292 static int __init init_ramfs_fs(void)
 293 {
 294         return register_filesystem(&ramfs_fs_type);
 295 }
 296
 297 static void __exit exit_ramfs_fs(void)
 298 {
 299         unregister_filesystem(&ramfs_fs_type);
 300 }
 301
 302 module_init(init_ramfs_fs)
 303 module_exit(exit_ramfs_fs)
 304
 305 int __init init_rootfs(void)
 306 {
 307         int err;
 308
 309         err = bdi_init(&ramfs_backing_dev_info);
 310         if (err)
 311                 return err;
 312
 313         err = register_filesystem(&rootfs_fs_type);
 314         if (err)
 315                 bdi_destroy(&ramfs_backing_dev_info);
 316
 317         return err;
 318 }
 319
 320 MODULE_LICENSE("GPL");