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 <linux/uaccess.h>
  39 #include <linux/fs_context.h>
  40 #include <linux/fs_parser.h>
  41 #include "internal.h"
  42
  43 struct ramfs_mount_opts {
  44         umode_t mode;
  45 };
  46
  47 struct ramfs_fs_info {
  48         struct ramfs_mount_opts mount_opts;
  49 };
  50
  51 #define RAMFS_DEFAULT_MODE      0755
  52
  53 static const struct super_operations ramfs_ops;
  54 static const struct inode_operations ramfs_dir_inode_operations;
  55
  56 static const struct address_space_operations ramfs_aops = {
  57         .readpage       = simple_readpage,
  58         .write_begin    = simple_write_begin,
  59         .write_end      = simple_write_end,
  60         .set_page_dirty = __set_page_dirty_no_writeback,
  61 };
  62
  63 struct inode *ramfs_get_inode(struct super_block *sb,
  64                                 const struct inode *dir, umode_t mode, dev_t dev)
  65 {
  66         struct inode * inode = new_inode(sb);
  67
  68         if (inode) {
  69                 inode->i_ino = get_next_ino();
  70                 inode_init_owner(inode, dir, mode);
  71                 inode->i_mapping->a_ops = &ramfs_aops;
  72                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  73                 mapping_set_unevictable(inode->i_mapping);
  74                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
  75                 switch (mode & S_IFMT) {
  76                 default:
  77                         init_special_inode(inode, mode, dev);
  78                         break;
  79                 case S_IFREG:
  80                         inode->i_op = &ramfs_file_inode_operations;
  81                         inode->i_fop = &ramfs_file_operations;
  82                         break;
  83                 case S_IFDIR:
  84                         inode->i_op = &ramfs_dir_inode_operations;
  85                         inode->i_fop = &simple_dir_operations;
  86
  87                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  88                         inc_nlink(inode);
  89                         break;
  90                 case S_IFLNK:
  91                         inode->i_op = &page_symlink_inode_operations;
  92                         inode_nohighmem(inode);
  93                         break;
  94                 }
  95         }
  96         return inode;
  97 }
  98
  99 /*
 100  * File creation. Allocate an inode, and we're done..
 101  */
 102 /* SMP-safe */
 103 static int
 104 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 105 {
 106         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
 107         int error = -ENOSPC;
 108
 109         if (inode) {
 110                 d_instantiate(dentry, inode);
 111                 dget(dentry);   /* Extra count - pin the dentry in core */
 112                 error = 0;
 113                 dir->i_mtime = dir->i_ctime = current_time(dir);
 114         }
 115         return error;
 116 }
 117
 118 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
 119 {
 120         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 121         if (!retval)
 122                 inc_nlink(dir);
 123         return retval;
 124 }
 125
 126 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
 127 {
 128         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 129 }
 130
 131 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 132 {
 133         struct inode *inode;
 134         int error = -ENOSPC;
 135
 136         inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
 137         if (inode) {
 138                 int l = strlen(symname)+1;
 139                 error = page_symlink(inode, symname, l);
 140                 if (!error) {
 141                         d_instantiate(dentry, inode);
 142                         dget(dentry);
 143                         dir->i_mtime = dir->i_ctime = current_time(dir);
 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 /*
 163  * Display the mount options in /proc/mounts.
 164  */
 165 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
 166 {
 167         struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
 168
 169         if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
 170                 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
 171         return 0;
 172 }
 173
 174 static const struct super_operations ramfs_ops = {
 175         .statfs         = simple_statfs,
 176         .drop_inode     = generic_delete_inode,
 177         .show_options   = ramfs_show_options,
 178 };
 179
 180 enum ramfs_param {
 181         Opt_mode,
 182 };
 183
 184 const struct fs_parameter_spec ramfs_fs_parameters[] = {
 185         fsparam_u32oct("mode",  Opt_mode),
 186         {}
 187 };
 188
 189 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 190 {
 191         struct fs_parse_result result;
 192         struct ramfs_fs_info *fsi = fc->s_fs_info;
 193         int opt;
 194
 195         opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
 196         if (opt < 0) {
 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                 if (opt == -ENOPARAM)
 204                         opt = 0;
 205                 return opt;
 206         }
 207
 208         switch (opt) {
 209         case Opt_mode:
 210                 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
 211                 break;
 212         }
 213
 214         return 0;
 215 }
 216
 217 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
 218 {
 219         struct ramfs_fs_info *fsi = sb->s_fs_info;
 220         struct inode *inode;
 221
 222         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 223         sb->s_blocksize         = PAGE_SIZE;
 224         sb->s_blocksize_bits    = PAGE_SHIFT;
 225         sb->s_magic             = RAMFS_MAGIC;
 226         sb->s_op                = &ramfs_ops;
 227         sb->s_time_gran         = 1;
 228
 229         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
 230         sb->s_root = d_make_root(inode);
 231         if (!sb->s_root)
 232                 return -ENOMEM;
 233
 234         return 0;
 235 }
 236
 237 static int ramfs_get_tree(struct fs_context *fc)
 238 {
 239         return get_tree_nodev(fc, ramfs_fill_super);
 240 }
 241
 242 static void ramfs_free_fc(struct fs_context *fc)
 243 {
 244         kfree(fc->s_fs_info);
 245 }
 246
 247 static const struct fs_context_operations ramfs_context_ops = {
 248         .free           = ramfs_free_fc,
 249         .parse_param    = ramfs_parse_param,
 250         .get_tree       = ramfs_get_tree,
 251 };
 252
 253 int ramfs_init_fs_context(struct fs_context *fc)
 254 {
 255         struct ramfs_fs_info *fsi;
 256
 257         fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
 258         if (!fsi)
 259                 return -ENOMEM;
 260
 261         fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
 262         fc->s_fs_info = fsi;
 263         fc->ops = &ramfs_context_ops;
 264         return 0;
 265 }
 266
 267 static void ramfs_kill_sb(struct super_block *sb)
 268 {
 269         kfree(sb->s_fs_info);
 270         kill_litter_super(sb);
 271 }
 272
 273 static struct file_system_type ramfs_fs_type = {
 274         .name           = "ramfs",
 275         .init_fs_context = ramfs_init_fs_context,
 276         .parameters     = ramfs_fs_parameters,
 277         .kill_sb        = ramfs_kill_sb,
 278         .fs_flags       = FS_USERNS_MOUNT,
 279 };
 280
 281 static int __init init_ramfs_fs(void)
 282 {
 283         return register_filesystem(&ramfs_fs_type);
 284 }
 285 fs_initcall(init_ramfs_fs);