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 <linux/seq_file.h>
  42 #include "internal.h"
  43
  44 struct ramfs_mount_opts {
  45         umode_t mode;
  46 };
  47
  48 struct ramfs_fs_info {
  49         struct ramfs_mount_opts mount_opts;
  50 };
  51
  52 #define RAMFS_DEFAULT_MODE      0755
  53
  54 static const struct super_operations ramfs_ops;
  55 static const struct inode_operations ramfs_dir_inode_operations;
  56
  57 struct inode *ramfs_get_inode(struct super_block *sb,
  58                                 const struct inode *dir, umode_t mode, dev_t dev)
  59 {
  60         struct inode * inode = new_inode(sb);
  61
  62         if (inode) {
  63                 inode->i_ino = get_next_ino();
  64                 inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
  65                 inode->i_mapping->a_ops = &ram_aops;
  66                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  67                 mapping_set_unevictable(inode->i_mapping);
  68                 simple_inode_init_ts(inode);
  69                 switch (mode & S_IFMT) {
  70                 default:
  71                         init_special_inode(inode, mode, dev);
  72                         break;
  73                 case S_IFREG:
  74                         inode->i_op = &ramfs_file_inode_operations;
  75                         inode->i_fop = &ramfs_file_operations;
  76                         break;
  77                 case S_IFDIR:
  78                         inode->i_op = &ramfs_dir_inode_operations;
  79                         inode->i_fop = &simple_dir_operations;
  80
  81                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  82                         inc_nlink(inode);
  83                         break;
  84                 case S_IFLNK:
  85                         inode->i_op = &page_symlink_inode_operations;
  86                         inode_nohighmem(inode);
  87                         break;
  88                 }
  89         }
  90         return inode;
  91 }
  92
  93 /*
  94  * File creation. Allocate an inode, and we're done..
  95  */
  96 /* SMP-safe */
  97 static int
  98 ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
  99             struct dentry *dentry, umode_t mode, dev_t dev)
 100 {
 101         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
 102         int error = -ENOSPC;
 103
 104         if (inode) {
 105                 error = security_inode_init_security(inode, dir,
 106                                                      &dentry->d_name, NULL,
 107                                                      NULL);
 108                 if (error) {
 109                         iput(inode);
 110                         goto out;
 111                 }
 112
 113                 d_instantiate(dentry, inode);
 114                 dget(dentry);   /* Extra count - pin the dentry in core */
 115                 error = 0;
 116                 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 117         }
 118 out:
 119         return error;
 120 }
 121
 122 static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 123                        struct dentry *dentry, umode_t mode)
 124 {
 125         int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0);
 126         if (!retval)
 127                 inc_nlink(dir);
 128         return retval;
 129 }
 130
 131 static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir,
 132                         struct dentry *dentry, umode_t mode, bool excl)
 133 {
 134         return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
 135 }
 136
 137 static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 138                          struct dentry *dentry, const char *symname)
 139 {
 140         struct inode *inode;
 141         int error = -ENOSPC;
 142
 143         inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
 144         if (inode) {
 145                 int l = strlen(symname)+1;
 146
 147                 error = security_inode_init_security(inode, dir,
 148                                                      &dentry->d_name, NULL,
 149                                                      NULL);
 150                 if (error) {
 151                         iput(inode);
 152                         goto out;
 153                 }
 154
 155                 error = page_symlink(inode, symname, l);
 156                 if (!error) {
 157                         d_instantiate(dentry, inode);
 158                         dget(dentry);
 159                         inode_set_mtime_to_ts(dir,
 160                                               inode_set_ctime_current(dir));
 161                 } else
 162                         iput(inode);
 163         }
 164 out:
 165         return error;
 166 }
 167
 168 static int ramfs_tmpfile(struct mnt_idmap *idmap,
 169                          struct inode *dir, struct file *file, umode_t mode)
 170 {
 171         struct inode *inode;
 172         int error;
 173
 174         inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
 175         if (!inode)
 176                 return -ENOSPC;
 177
 178         error = security_inode_init_security(inode, dir,
 179                                              &file_dentry(file)->d_name, NULL,
 180                                              NULL);
 181         if (error) {
 182                 iput(inode);
 183                 goto out;
 184         }
 185
 186         d_tmpfile(file, inode);
 187 out:
 188         return finish_open_simple(file, error);
 189 }
 190
 191 static const struct inode_operations ramfs_dir_inode_operations = {
 192         .create         = ramfs_create,
 193         .lookup         = simple_lookup,
 194         .link           = simple_link,
 195         .unlink         = simple_unlink,
 196         .symlink        = ramfs_symlink,
 197         .mkdir          = ramfs_mkdir,
 198         .rmdir          = simple_rmdir,
 199         .mknod          = ramfs_mknod,
 200         .rename         = simple_rename,
 201         .tmpfile        = ramfs_tmpfile,
 202 };
 203
 204 /*
 205  * Display the mount options in /proc/mounts.
 206  */
 207 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
 208 {
 209         struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
 210
 211         if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
 212                 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
 213         return 0;
 214 }
 215
 216 static const struct super_operations ramfs_ops = {
 217         .statfs         = simple_statfs,
 218         .drop_inode     = generic_delete_inode,
 219         .show_options   = ramfs_show_options,
 220 };
 221
 222 enum ramfs_param {
 223         Opt_mode,
 224 };
 225
 226 const struct fs_parameter_spec ramfs_fs_parameters[] = {
 227         fsparam_u32oct("mode",  Opt_mode),
 228         {}
 229 };
 230
 231 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 232 {
 233         struct fs_parse_result result;
 234         struct ramfs_fs_info *fsi = fc->s_fs_info;
 235         int opt;
 236
 237         opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
 238         if (opt == -ENOPARAM) {
 239                 opt = vfs_parse_fs_param_source(fc, param);
 240                 if (opt != -ENOPARAM)
 241                         return opt;
 242                 /*
 243                  * We might like to report bad mount options here;
 244                  * but traditionally ramfs has ignored all mount options,
 245                  * and as it is used as a !CONFIG_SHMEM simple substitute
 246                  * for tmpfs, better continue to ignore other mount options.
 247                  */
 248                 return 0;
 249         }
 250         if (opt < 0)
 251                 return opt;
 252
 253         switch (opt) {
 254         case Opt_mode:
 255                 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
 256                 break;
 257         }
 258
 259         return 0;
 260 }
 261
 262 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
 263 {
 264         struct ramfs_fs_info *fsi = sb->s_fs_info;
 265         struct inode *inode;
 266
 267         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 268         sb->s_blocksize         = PAGE_SIZE;
 269         sb->s_blocksize_bits    = PAGE_SHIFT;
 270         sb->s_magic             = RAMFS_MAGIC;
 271         sb->s_op                = &ramfs_ops;
 272         sb->s_time_gran         = 1;
 273
 274         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
 275         sb->s_root = d_make_root(inode);
 276         if (!sb->s_root)
 277                 return -ENOMEM;
 278
 279         return 0;
 280 }
 281
 282 static int ramfs_get_tree(struct fs_context *fc)
 283 {
 284         return get_tree_nodev(fc, ramfs_fill_super);
 285 }
 286
 287 static void ramfs_free_fc(struct fs_context *fc)
 288 {
 289         kfree(fc->s_fs_info);
 290 }
 291
 292 static const struct fs_context_operations ramfs_context_ops = {
 293         .free           = ramfs_free_fc,
 294         .parse_param    = ramfs_parse_param,
 295         .get_tree       = ramfs_get_tree,
 296 };
 297
 298 int ramfs_init_fs_context(struct fs_context *fc)
 299 {
 300         struct ramfs_fs_info *fsi;
 301
 302         fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
 303         if (!fsi)
 304                 return -ENOMEM;
 305
 306         fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
 307         fc->s_fs_info = fsi;
 308         fc->ops = &ramfs_context_ops;
 309         return 0;
 310 }
 311
 312 void ramfs_kill_sb(struct super_block *sb)
 313 {
 314         kfree(sb->s_fs_info);
 315         kill_litter_super(sb);
 316 }
 317
 318 static struct file_system_type ramfs_fs_type = {
 319         .name           = "ramfs",
 320         .init_fs_context = ramfs_init_fs_context,
 321         .parameters     = ramfs_fs_parameters,
 322         .kill_sb        = ramfs_kill_sb,
 323         .fs_flags       = FS_USERNS_MOUNT,
 324 };
 325
 326 static int __init init_ramfs_fs(void)
 327 {
 328         return register_filesystem(&ramfs_fs_type);
 329 }
 330 fs_initcall(init_ramfs_fs);