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 <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, int mode, dev_t dev)
  55 {
  56         struct inode * inode = new_inode(sb);
  57
  58         if (inode) {
  59                 inode->i_mode = mode;
  60                 inode->i_uid = current_fsuid();
  61                 inode->i_gid = current_fsgid();
  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, int mode, dev_t dev)
  96 {
  97         struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
  98         int error = -ENOSPC;
  99
 100         if (inode) {
 101                 if (dir->i_mode & S_ISGID) {
 102                         inode->i_gid = dir->i_gid;
 103                         if (S_ISDIR(mode))
 104                                 inode->i_mode |= S_ISGID;
 105                 }
 106                 d_instantiate(dentry, inode);
 107                 dget(dentry);   /* Extra count - pin the dentry in core */
 108                 error = 0;
 109                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 110         }
 111         return error;
 112 }
 113
 114 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 115 {
 116         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 117         if (!retval)
 118                 inc_nlink(dir);
 119         return retval;
 120 }
 121
 122 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
 123 {
 124         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 125 }
 126
 127 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 128 {
 129         struct inode *inode;
 130         int error = -ENOSPC;
 131
 132         inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
 133         if (inode) {
 134                 int l = strlen(symname)+1;
 135                 error = page_symlink(inode, symname, l);
 136                 if (!error) {
 137                         if (dir->i_mode & S_ISGID)
 138                                 inode->i_gid = dir->i_gid;
 139                         d_instantiate(dentry, inode);
 140                         dget(dentry);
 141                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 142                 } else
 143                         iput(inode);
 144         }
 145         return error;
 146 }
 147
 148 static const struct inode_operations ramfs_dir_inode_operations = {
 149         .create         = ramfs_create,
 150         .lookup         = simple_lookup,
 151         .link           = simple_link,
 152         .unlink         = simple_unlink,
 153         .symlink        = ramfs_symlink,
 154         .mkdir          = ramfs_mkdir,
 155         .rmdir          = simple_rmdir,
 156         .mknod          = ramfs_mknod,
 157         .rename         = simple_rename,
 158 };
 159
 160 static const struct super_operations ramfs_ops = {
 161         .statfs         = simple_statfs,
 162         .drop_inode     = generic_delete_inode,
 163         .show_options   = generic_show_options,
 164 };
 165
 166 struct ramfs_mount_opts {
 167         umode_t mode;
 168 };
 169
 170 enum {
 171         Opt_mode,
 172         Opt_err
 173 };
 174
 175 static const match_table_t tokens = {
 176         {Opt_mode, "mode=%o"},
 177         {Opt_err, NULL}
 178 };
 179
 180 struct ramfs_fs_info {
 181         struct ramfs_mount_opts mount_opts;
 182 };
 183
 184 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
 185 {
 186         substring_t args[MAX_OPT_ARGS];
 187         int option;
 188         int token;
 189         char *p;
 190
 191         opts->mode = RAMFS_DEFAULT_MODE;
 192
 193         while ((p = strsep(&data, ",")) != NULL) {
 194                 if (!*p)
 195                         continue;
 196
 197                 token = match_token(p, tokens, args);
 198                 switch (token) {
 199                 case Opt_mode:
 200                         if (match_octal(&args[0], &option))
 201                                 return -EINVAL;
 202                         opts->mode = option & S_IALLUGO;
 203                         break;
 204                 /*
 205                  * We might like to report bad mount options here;
 206                  * but traditionally ramfs has ignored all mount options,
 207                  * and as it is used as a !CONFIG_SHMEM simple substitute
 208                  * for tmpfs, better continue to ignore other mount options.
 209                  */
 210                 }
 211         }
 212
 213         return 0;
 214 }
 215
 216 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
 217 {
 218         struct ramfs_fs_info *fsi;
 219         struct inode *inode = NULL;
 220         struct dentry *root;
 221         int err;
 222
 223         save_mount_options(sb, data);
 224
 225         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
 226         sb->s_fs_info = fsi;
 227         if (!fsi) {
 228                 err = -ENOMEM;
 229                 goto fail;
 230         }
 231
 232         err = ramfs_parse_options(data, &fsi->mount_opts);
 233         if (err)
 234                 goto fail;
 235
 236         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 237         sb->s_blocksize         = PAGE_CACHE_SIZE;
 238         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 239         sb->s_magic             = RAMFS_MAGIC;
 240         sb->s_op                = &ramfs_ops;
 241         sb->s_time_gran         = 1;
 242
 243         inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0);
 244         if (!inode) {
 245                 err = -ENOMEM;
 246                 goto fail;
 247         }
 248
 249         root = d_alloc_root(inode);
 250         sb->s_root = root;
 251         if (!root) {
 252                 err = -ENOMEM;
 253                 goto fail;
 254         }
 255
 256         return 0;
 257 fail:
 258         kfree(fsi);
 259         sb->s_fs_info = NULL;
 260         iput(inode);
 261         return err;
 262 }
 263
 264 int ramfs_get_sb(struct file_system_type *fs_type,
 265         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 266 {
 267         return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
 268 }
 269
 270 static int rootfs_get_sb(struct file_system_type *fs_type,
 271         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 272 {
 273         return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
 274                             mnt);
 275 }
 276
 277 static void ramfs_kill_sb(struct super_block *sb)
 278 {
 279         kfree(sb->s_fs_info);
 280         kill_litter_super(sb);
 281 }
 282
 283 static struct file_system_type ramfs_fs_type = {
 284         .name           = "ramfs",
 285         .get_sb         = ramfs_get_sb,
 286         .kill_sb        = ramfs_kill_sb,
 287 };
 288 static struct file_system_type rootfs_fs_type = {
 289         .name           = "rootfs",
 290         .get_sb         = rootfs_get_sb,
 291         .kill_sb        = kill_litter_super,
 292 };
 293
 294 static int __init init_ramfs_fs(void)
 295 {
 296         return register_filesystem(&ramfs_fs_type);
 297 }
 298
 299 static void __exit exit_ramfs_fs(void)
 300 {
 301         unregister_filesystem(&ramfs_fs_type);
 302 }
 303
 304 module_init(init_ramfs_fs)
 305 module_exit(exit_ramfs_fs)
 306
 307 int __init init_rootfs(void)
 308 {
 309         int err;
 310
 311         err = bdi_init(&ramfs_backing_dev_info);
 312         if (err)
 313                 return err;
 314
 315         err = register_filesystem(&rootfs_fs_type);
 316         if (err)
 317                 bdi_destroy(&ramfs_backing_dev_info);
 318
 319         return err;
 320 }
 321
 322 MODULE_LICENSE("GPL");