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 static struct backing_dev_info ramfs_backing_dev_info = {
  54         .name           = "ramfs",
  55         .ra_pages       = 0,    /* No readahead */
  56         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK |
  57                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
  58                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
  59 };
  60
  61 struct inode *ramfs_get_inode(struct super_block *sb,
  62                                 const struct inode *dir, umode_t mode, dev_t dev)
  63 {
  64         struct inode * inode = new_inode(sb);
  65
  66         if (inode) {
  67                 inode->i_ino = get_next_ino();
  68                 inode_init_owner(inode, dir, mode);
  69                 inode->i_mapping->a_ops = &ramfs_aops;
  70                 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
  71                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  72                 mapping_set_unevictable(inode->i_mapping);
  73                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  74                 switch (mode & S_IFMT) {
  75                 default:
  76                         init_special_inode(inode, mode, dev);
  77                         break;
  78                 case S_IFREG:
  79                         inode->i_op = &ramfs_file_inode_operations;
  80                         inode->i_fop = &ramfs_file_operations;
  81                         break;
  82                 case S_IFDIR:
  83                         inode->i_op = &ramfs_dir_inode_operations;
  84                         inode->i_fop = &simple_dir_operations;
  85
  86                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  87                         inc_nlink(inode);
  88                         break;
  89                 case S_IFLNK:
  90                         inode->i_op = &page_symlink_inode_operations;
  91                         break;
  92                 }
  93         }
  94         return inode;
  95 }
  96
  97 /*
  98  * File creation. Allocate an inode, and we're done..
  99  */
 100 /* SMP-safe */
 101 static int
 102 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 103 {
 104         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
 105         int error = -ENOSPC;
 106
 107         if (inode) {
 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, umode_t 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, umode_t mode, bool excl)
 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, dir, 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                         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 int ramfs_fill_super(struct super_block *sb, void *data, int silent)
 217 {
 218         struct ramfs_fs_info *fsi;
 219         struct inode *inode;
 220         int err;
 221
 222         save_mount_options(sb, data);
 223
 224         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
 225         sb->s_fs_info = fsi;
 226         if (!fsi)
 227                 return -ENOMEM;
 228
 229         err = ramfs_parse_options(data, &fsi->mount_opts);
 230         if (err)
 231                 return err;
 232
 233         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 234         sb->s_blocksize         = PAGE_CACHE_SIZE;
 235         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 236         sb->s_magic             = RAMFS_MAGIC;
 237         sb->s_op                = &ramfs_ops;
 238         sb->s_time_gran         = 1;
 239
 240         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
 241         sb->s_root = d_make_root(inode);
 242         if (!sb->s_root)
 243                 return -ENOMEM;
 244
 245         return 0;
 246 }
 247
 248 struct dentry *ramfs_mount(struct file_system_type *fs_type,
 249         int flags, const char *dev_name, void *data)
 250 {
 251         return mount_nodev(fs_type, flags, data, ramfs_fill_super);
 252 }
 253
 254 static void ramfs_kill_sb(struct super_block *sb)
 255 {
 256         kfree(sb->s_fs_info);
 257         kill_litter_super(sb);
 258 }
 259
 260 static struct file_system_type ramfs_fs_type = {
 261         .name           = "ramfs",
 262         .mount          = ramfs_mount,
 263         .kill_sb        = ramfs_kill_sb,
 264         .fs_flags       = FS_USERNS_MOUNT,
 265 };
 266
 267 int __init init_ramfs_fs(void)
 268 {
 269         static unsigned long once;
 270         int err;
 271
 272         if (test_and_set_bit(0, &once))
 273                 return 0;
 274
 275         err = bdi_init(&ramfs_backing_dev_info);
 276         if (err)
 277                 return err;
 278
 279         err = register_filesystem(&ramfs_fs_type);
 280         if (err)
 281                 bdi_destroy(&ramfs_backing_dev_info);
 282
 283         return err;
 284 }
 285 fs_initcall(init_ramfs_fs);