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/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 void ramfs_kill_sb(struct super_block *sb)
 248 {
 249         kfree(sb->s_fs_info);
 250         kill_litter_super(sb);
 251 }
 252
 253 static struct file_system_type ramfs_fs_type = {
 254         .name           = "ramfs",
 255         .mount          = ramfs_mount,
 256         .kill_sb        = ramfs_kill_sb,
 257         .fs_flags       = FS_USERNS_MOUNT,
 258 };
 259
 260 int __init init_ramfs_fs(void)
 261 {
 262         static unsigned long once;
 263         int err;
 264
 265         if (test_and_set_bit(0, &once))
 266                 return 0;
 267
 268         err = bdi_init(&ramfs_backing_dev_info);
 269         if (err)
 270                 return err;
 271
 272         err = register_filesystem(&ramfs_fs_type);
 273         if (err)
 274                 bdi_destroy(&ramfs_backing_dev_info);
 275
 276         return err;
 277 }
 278 module_init(init_ramfs_fs)