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 const struct address_space_operations ramfs_aops = {
  47         .readpage       = simple_readpage,
  48         .write_begin    = simple_write_begin,
  49         .write_end      = simple_write_end,
  50         .set_page_dirty = __set_page_dirty_no_writeback,
  51 };
  52
  53 struct inode *ramfs_get_inode(struct super_block *sb,
  54                                 const struct inode *dir, umode_t mode, dev_t dev)
  55 {
  56         struct inode * inode = new_inode(sb);
  57
  58         if (inode) {
  59                 inode->i_ino = get_next_ino();
  60                 inode_init_owner(inode, dir, mode);
  61                 inode->i_mapping->a_ops = &ramfs_aops;
  62                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  63                 mapping_set_unevictable(inode->i_mapping);
  64                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  65                 switch (mode & S_IFMT) {
  66                 default:
  67                         init_special_inode(inode, mode, dev);
  68                         break;
  69                 case S_IFREG:
  70                         inode->i_op = &ramfs_file_inode_operations;
  71                         inode->i_fop = &ramfs_file_operations;
  72                         break;
  73                 case S_IFDIR:
  74                         inode->i_op = &ramfs_dir_inode_operations;
  75                         inode->i_fop = &simple_dir_operations;
  76
  77                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  78                         inc_nlink(inode);
  79                         break;
  80                 case S_IFLNK:
  81                         inode->i_op = &page_symlink_inode_operations;
  82                         break;
  83                 }
  84         }
  85         return inode;
  86 }
  87
  88 /*
  89  * File creation. Allocate an inode, and we're done..
  90  */
  91 /* SMP-safe */
  92 static int
  93 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
  94 {
  95         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
  96         int error = -ENOSPC;
  97
  98         if (inode) {
  99                 d_instantiate(dentry, inode);
 100                 dget(dentry);   /* Extra count - pin the dentry in core */
 101                 error = 0;
 102                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 103         }
 104         return error;
 105 }
 106
 107 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
 108 {
 109         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 110         if (!retval)
 111                 inc_nlink(dir);
 112         return retval;
 113 }
 114
 115 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
 116 {
 117         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 118 }
 119
 120 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 121 {
 122         struct inode *inode;
 123         int error = -ENOSPC;
 124
 125         inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
 126         if (inode) {
 127                 int l = strlen(symname)+1;
 128                 error = page_symlink(inode, symname, l);
 129                 if (!error) {
 130                         d_instantiate(dentry, inode);
 131                         dget(dentry);
 132                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 133                 } else
 134                         iput(inode);
 135         }
 136         return error;
 137 }
 138
 139 static const struct inode_operations ramfs_dir_inode_operations = {
 140         .create         = ramfs_create,
 141         .lookup         = simple_lookup,
 142         .link           = simple_link,
 143         .unlink         = simple_unlink,
 144         .symlink        = ramfs_symlink,
 145         .mkdir          = ramfs_mkdir,
 146         .rmdir          = simple_rmdir,
 147         .mknod          = ramfs_mknod,
 148         .rename         = simple_rename,
 149 };
 150
 151 static const struct super_operations ramfs_ops = {
 152         .statfs         = simple_statfs,
 153         .drop_inode     = generic_delete_inode,
 154         .show_options   = generic_show_options,
 155 };
 156
 157 struct ramfs_mount_opts {
 158         umode_t mode;
 159 };
 160
 161 enum {
 162         Opt_mode,
 163         Opt_err
 164 };
 165
 166 static const match_table_t tokens = {
 167         {Opt_mode, "mode=%o"},
 168         {Opt_err, NULL}
 169 };
 170
 171 struct ramfs_fs_info {
 172         struct ramfs_mount_opts mount_opts;
 173 };
 174
 175 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
 176 {
 177         substring_t args[MAX_OPT_ARGS];
 178         int option;
 179         int token;
 180         char *p;
 181
 182         opts->mode = RAMFS_DEFAULT_MODE;
 183
 184         while ((p = strsep(&data, ",")) != NULL) {
 185                 if (!*p)
 186                         continue;
 187
 188                 token = match_token(p, tokens, args);
 189                 switch (token) {
 190                 case Opt_mode:
 191                         if (match_octal(&args[0], &option))
 192                                 return -EINVAL;
 193                         opts->mode = option & S_IALLUGO;
 194                         break;
 195                 /*
 196                  * We might like to report bad mount options here;
 197                  * but traditionally ramfs has ignored all mount options,
 198                  * and as it is used as a !CONFIG_SHMEM simple substitute
 199                  * for tmpfs, better continue to ignore other mount options.
 200                  */
 201                 }
 202         }
 203
 204         return 0;
 205 }
 206
 207 int ramfs_fill_super(struct super_block *sb, void *data, int silent)
 208 {
 209         struct ramfs_fs_info *fsi;
 210         struct inode *inode;
 211         int err;
 212
 213         save_mount_options(sb, data);
 214
 215         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
 216         sb->s_fs_info = fsi;
 217         if (!fsi)
 218                 return -ENOMEM;
 219
 220         err = ramfs_parse_options(data, &fsi->mount_opts);
 221         if (err)
 222                 return err;
 223
 224         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 225         sb->s_blocksize         = PAGE_CACHE_SIZE;
 226         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 227         sb->s_magic             = RAMFS_MAGIC;
 228         sb->s_op                = &ramfs_ops;
 229         sb->s_time_gran         = 1;
 230
 231         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
 232         sb->s_root = d_make_root(inode);
 233         if (!sb->s_root)
 234                 return -ENOMEM;
 235
 236         return 0;
 237 }
 238
 239 struct dentry *ramfs_mount(struct file_system_type *fs_type,
 240         int flags, const char *dev_name, void *data)
 241 {
 242         return mount_nodev(fs_type, flags, data, ramfs_fill_super);
 243 }
 244
 245 static void ramfs_kill_sb(struct super_block *sb)
 246 {
 247         kfree(sb->s_fs_info);
 248         kill_litter_super(sb);
 249 }
 250
 251 static struct file_system_type ramfs_fs_type = {
 252         .name           = "ramfs",
 253         .mount          = ramfs_mount,
 254         .kill_sb        = ramfs_kill_sb,
 255         .fs_flags       = FS_USERNS_MOUNT,
 256 };
 257
 258 int __init init_ramfs_fs(void)
 259 {
 260         static unsigned long once;
 261
 262         if (test_and_set_bit(0, &once))
 263                 return 0;
 264         return register_filesystem(&ramfs_fs_type);
 265 }
 266 fs_initcall(init_ramfs_fs);