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         .name           = "ramfs",
  50         .ra_pages       = 0,    /* No readahead */
  51         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK |
  52                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
  53                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
  54 };
  55
  56 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  57 {
  58         struct inode * inode = new_inode(sb);
  59
  60         if (inode) {
  61                 inode->i_mode = mode;
  62                 inode->i_uid = current_fsuid();
  63                 inode->i_gid = current_fsgid();
  64                 inode->i_mapping->a_ops = &ramfs_aops;
  65                 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
  66                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  67                 mapping_set_unevictable(inode->i_mapping);
  68                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  69                 switch (mode & S_IFMT) {
  70                 default:
  71                         init_special_inode(inode, mode, dev);
  72                         break;
  73                 case S_IFREG:
  74                         inode->i_op = &ramfs_file_inode_operations;
  75                         inode->i_fop = &ramfs_file_operations;
  76                         break;
  77                 case S_IFDIR:
  78                         inode->i_op = &ramfs_dir_inode_operations;
  79                         inode->i_fop = &simple_dir_operations;
  80
  81                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  82                         inc_nlink(inode);
  83                         break;
  84                 case S_IFLNK:
  85                         inode->i_op = &page_symlink_inode_operations;
  86                         break;
  87                 }
  88         }
  89         return inode;
  90 }
  91
  92 /*
  93  * File creation. Allocate an inode, and we're done..
  94  */
  95 /* SMP-safe */
  96 static int
  97 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  98 {
  99         struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
 100         int error = -ENOSPC;
 101
 102         if (inode) {
 103                 if (dir->i_mode & S_ISGID) {
 104                         inode->i_gid = dir->i_gid;
 105                         if (S_ISDIR(mode))
 106                                 inode->i_mode |= S_ISGID;
 107                 }
 108                 d_instantiate(dentry, inode);
 109                 dget(dentry);   /* Extra count - pin the dentry in core */
 110                 error = 0;
 111                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 112         }
 113         return error;
 114 }
 115
 116 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 117 {
 118         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 119         if (!retval)
 120                 inc_nlink(dir);
 121         return retval;
 122 }
 123
 124 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
 125 {
 126         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 127 }
 128
 129 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 130 {
 131         struct inode *inode;
 132         int error = -ENOSPC;
 133
 134         inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
 135         if (inode) {
 136                 int l = strlen(symname)+1;
 137                 error = page_symlink(inode, symname, l);
 138                 if (!error) {
 139                         if (dir->i_mode & S_ISGID)
 140                                 inode->i_gid = dir->i_gid;
 141                         d_instantiate(dentry, inode);
 142                         dget(dentry);
 143                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 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 static const struct super_operations ramfs_ops = {
 163         .statfs         = simple_statfs,
 164         .drop_inode     = generic_delete_inode,
 165         .show_options   = generic_show_options,
 166 };
 167
 168 struct ramfs_mount_opts {
 169         umode_t mode;
 170 };
 171
 172 enum {
 173         Opt_mode,
 174         Opt_err
 175 };
 176
 177 static const match_table_t tokens = {
 178         {Opt_mode, "mode=%o"},
 179         {Opt_err, NULL}
 180 };
 181
 182 struct ramfs_fs_info {
 183         struct ramfs_mount_opts mount_opts;
 184 };
 185
 186 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
 187 {
 188         substring_t args[MAX_OPT_ARGS];
 189         int option;
 190         int token;
 191         char *p;
 192
 193         opts->mode = RAMFS_DEFAULT_MODE;
 194
 195         while ((p = strsep(&data, ",")) != NULL) {
 196                 if (!*p)
 197                         continue;
 198
 199                 token = match_token(p, tokens, args);
 200                 switch (token) {
 201                 case Opt_mode:
 202                         if (match_octal(&args[0], &option))
 203                                 return -EINVAL;
 204                         opts->mode = option & S_IALLUGO;
 205                         break;
 206                 /*
 207                  * We might like to report bad mount options here;
 208                  * but traditionally ramfs has ignored all mount options,
 209                  * and as it is used as a !CONFIG_SHMEM simple substitute
 210                  * for tmpfs, better continue to ignore other mount options.
 211                  */
 212                 }
 213         }
 214
 215         return 0;
 216 }
 217
 218 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
 219 {
 220         struct ramfs_fs_info *fsi;
 221         struct inode *inode = NULL;
 222         struct dentry *root;
 223         int err;
 224
 225         save_mount_options(sb, data);
 226
 227         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
 228         sb->s_fs_info = fsi;
 229         if (!fsi) {
 230                 err = -ENOMEM;
 231                 goto fail;
 232         }
 233
 234         err = ramfs_parse_options(data, &fsi->mount_opts);
 235         if (err)
 236                 goto fail;
 237
 238         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 239         sb->s_blocksize         = PAGE_CACHE_SIZE;
 240         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 241         sb->s_magic             = RAMFS_MAGIC;
 242         sb->s_op                = &ramfs_ops;
 243         sb->s_time_gran         = 1;
 244
 245         inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0);
 246         if (!inode) {
 247                 err = -ENOMEM;
 248                 goto fail;
 249         }
 250
 251         root = d_alloc_root(inode);
 252         sb->s_root = root;
 253         if (!root) {
 254                 err = -ENOMEM;
 255                 goto fail;
 256         }
 257
 258         return 0;
 259 fail:
 260         kfree(fsi);
 261         sb->s_fs_info = NULL;
 262         iput(inode);
 263         return err;
 264 }
 265
 266 int ramfs_get_sb(struct file_system_type *fs_type,
 267         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 268 {
 269         return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
 270 }
 271
 272 static int rootfs_get_sb(struct file_system_type *fs_type,
 273         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 274 {
 275         return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
 276                             mnt);
 277 }
 278
 279 static void ramfs_kill_sb(struct super_block *sb)
 280 {
 281         kfree(sb->s_fs_info);
 282         kill_litter_super(sb);
 283 }
 284
 285 static struct file_system_type ramfs_fs_type = {
 286         .name           = "ramfs",
 287         .get_sb         = ramfs_get_sb,
 288         .kill_sb        = ramfs_kill_sb,
 289 };
 290 static struct file_system_type rootfs_fs_type = {
 291         .name           = "rootfs",
 292         .get_sb         = rootfs_get_sb,
 293         .kill_sb        = kill_litter_super,
 294 };
 295
 296 static int __init init_ramfs_fs(void)
 297 {
 298         return register_filesystem(&ramfs_fs_type);
 299 }
 300
 301 static void __exit exit_ramfs_fs(void)
 302 {
 303         unregister_filesystem(&ramfs_fs_type);
 304 }
 305
 306 module_init(init_ramfs_fs)
 307 module_exit(exit_ramfs_fs)
 308
 309 int __init init_rootfs(void)
 310 {
 311         int err;
 312
 313         err = bdi_init(&ramfs_backing_dev_info);
 314         if (err)
 315                 return err;
 316
 317         err = register_filesystem(&rootfs_fs_type);
 318         if (err)
 319                 bdi_destroy(&ramfs_backing_dev_info);
 320
 321         return err;
 322 }
 323
 324 MODULE_LICENSE("GPL");