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/module.h>
  27 #include <linux/fs.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/highmem.h>
  30 #include <linux/time.h>
  31 #include <linux/init.h>
  32 #include <linux/string.h>
  33 #include <linux/backing-dev.h>
  34 #include <linux/ramfs.h>
  35 #include <linux/sched.h>
  36 #include <asm/uaccess.h>
  37 #include "internal.h"
  38
  39 /* some random number */
  40 #define RAMFS_MAGIC     0x858458f6
  41
  42 static const struct super_operations ramfs_ops;
  43 static const struct inode_operations ramfs_dir_inode_operations;
  44
  45 static struct backing_dev_info ramfs_backing_dev_info = {
  46         .ra_pages       = 0,    /* No readahead */
  47         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK |
  48                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
  49                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
  50 };
  51
  52 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  53 {
  54         struct inode * inode = new_inode(sb);
  55
  56         if (inode) {
  57                 inode->i_mode = mode;
  58                 inode->i_uid = current->fsuid;
  59                 inode->i_gid = current->fsgid;
  60                 inode->i_blocks = 0;
  61                 inode->i_mapping->a_ops = &ramfs_aops;
  62                 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
  63                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
  64                 mapping_set_unevictable(inode->i_mapping);
  65                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  66                 switch (mode & S_IFMT) {
  67                 default:
  68                         init_special_inode(inode, mode, dev);
  69                         break;
  70                 case S_IFREG:
  71                         inode->i_op = &ramfs_file_inode_operations;
  72                         inode->i_fop = &ramfs_file_operations;
  73                         break;
  74                 case S_IFDIR:
  75                         inode->i_op = &ramfs_dir_inode_operations;
  76                         inode->i_fop = &simple_dir_operations;
  77
  78                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  79                         inc_nlink(inode);
  80                         break;
  81                 case S_IFLNK:
  82                         inode->i_op = &page_symlink_inode_operations;
  83                         break;
  84                 }
  85         }
  86         return inode;
  87 }
  88
  89 /*
  90  * File creation. Allocate an inode, and we're done..
  91  */
  92 /* SMP-safe */
  93 static int
  94 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  95 {
  96         struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
  97         int error = -ENOSPC;
  98
  99         if (inode) {
 100                 if (dir->i_mode & S_ISGID) {
 101                         inode->i_gid = dir->i_gid;
 102                         if (S_ISDIR(mode))
 103                                 inode->i_mode |= S_ISGID;
 104                 }
 105                 d_instantiate(dentry, inode);
 106                 dget(dentry);   /* Extra count - pin the dentry in core */
 107                 error = 0;
 108                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 109         }
 110         return error;
 111 }
 112
 113 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 114 {
 115         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 116         if (!retval)
 117                 inc_nlink(dir);
 118         return retval;
 119 }
 120
 121 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
 122 {
 123         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 124 }
 125
 126 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 127 {
 128         struct inode *inode;
 129         int error = -ENOSPC;
 130
 131         inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
 132         if (inode) {
 133                 int l = strlen(symname)+1;
 134                 error = page_symlink(inode, symname, l);
 135                 if (!error) {
 136                         if (dir->i_mode & S_ISGID)
 137                                 inode->i_gid = dir->i_gid;
 138                         d_instantiate(dentry, inode);
 139                         dget(dentry);
 140                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 141                 } else
 142                         iput(inode);
 143         }
 144         return error;
 145 }
 146
 147 static const struct inode_operations ramfs_dir_inode_operations = {
 148         .create         = ramfs_create,
 149         .lookup         = simple_lookup,
 150         .link           = simple_link,
 151         .unlink         = simple_unlink,
 152         .symlink        = ramfs_symlink,
 153         .mkdir          = ramfs_mkdir,
 154         .rmdir          = simple_rmdir,
 155         .mknod          = ramfs_mknod,
 156         .rename         = simple_rename,
 157 };
 158
 159 static const struct super_operations ramfs_ops = {
 160         .statfs         = simple_statfs,
 161         .drop_inode     = generic_delete_inode,
 162 };
 163
 164 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
 165 {
 166         struct inode * inode;
 167         struct dentry * root;
 168
 169         sb->s_maxbytes = MAX_LFS_FILESIZE;
 170         sb->s_blocksize = PAGE_CACHE_SIZE;
 171         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 172         sb->s_magic = RAMFS_MAGIC;
 173         sb->s_op = &ramfs_ops;
 174         sb->s_time_gran = 1;
 175         inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
 176         if (!inode)
 177                 return -ENOMEM;
 178
 179         root = d_alloc_root(inode);
 180         if (!root) {
 181                 iput(inode);
 182                 return -ENOMEM;
 183         }
 184         sb->s_root = root;
 185         return 0;
 186 }
 187
 188 int ramfs_get_sb(struct file_system_type *fs_type,
 189         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 190 {
 191         return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
 192 }
 193
 194 static int rootfs_get_sb(struct file_system_type *fs_type,
 195         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 196 {
 197         return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
 198                             mnt);
 199 }
 200
 201 static struct file_system_type ramfs_fs_type = {
 202         .name           = "ramfs",
 203         .get_sb         = ramfs_get_sb,
 204         .kill_sb        = kill_litter_super,
 205 };
 206 static struct file_system_type rootfs_fs_type = {
 207         .name           = "rootfs",
 208         .get_sb         = rootfs_get_sb,
 209         .kill_sb        = kill_litter_super,
 210 };
 211
 212 static int __init init_ramfs_fs(void)
 213 {
 214         return register_filesystem(&ramfs_fs_type);
 215 }
 216
 217 static void __exit exit_ramfs_fs(void)
 218 {
 219         unregister_filesystem(&ramfs_fs_type);
 220 }
 221
 222 module_init(init_ramfs_fs)
 223 module_exit(exit_ramfs_fs)
 224
 225 int __init init_rootfs(void)
 226 {
 227         int err;
 228
 229         err = bdi_init(&ramfs_backing_dev_info);
 230         if (err)
 231                 return err;
 232
 233         err = register_filesystem(&rootfs_fs_type);
 234         if (err)
 235                 bdi_destroy(&ramfs_backing_dev_info);
 236
 237         return err;
 238 }
 239
 240 MODULE_LICENSE("GPL");