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/smp_lock.h>
  34 #include <linux/backing-dev.h>
  35 #include <linux/ramfs.h>
  36
  37 #include <asm/uaccess.h>
  38 #include "internal.h"
  39
  40 /* some random number */
  41 #define RAMFS_MAGIC     0x858458f6
  42
  43 static const struct super_operations ramfs_ops;
  44 static const struct inode_operations ramfs_dir_inode_operations;
  45
  46 static struct backing_dev_info ramfs_backing_dev_info = {
  47         .ra_pages       = 0,    /* No readahead */
  48         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK |
  49                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
  50                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
  51 };
  52
  53 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  54 {
  55         struct inode * inode = new_inode(sb);
  56
  57         if (inode) {
  58                 inode->i_mode = mode;
  59                 inode->i_uid = current->fsuid;
  60                 inode->i_gid = current->fsgid;
  61                 inode->i_blocks = 0;
  62                 inode->i_mapping->a_ops = &ramfs_aops;
  63                 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
  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, int mode, dev_t dev)
  94 {
  95         struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
  96         int error = -ENOSPC;
  97
  98         if (inode) {
  99                 if (dir->i_mode & S_ISGID) {
 100                         inode->i_gid = dir->i_gid;
 101                         if (S_ISDIR(mode))
 102                                 inode->i_mode |= S_ISGID;
 103                 }
 104                 d_instantiate(dentry, inode);
 105                 dget(dentry);   /* Extra count - pin the dentry in core */
 106                 error = 0;
 107                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 108         }
 109         return error;
 110 }
 111
 112 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 113 {
 114         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
 115         if (!retval)
 116                 inc_nlink(dir);
 117         return retval;
 118 }
 119
 120 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
 121 {
 122         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
 123 }
 124
 125 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
 126 {
 127         struct inode *inode;
 128         int error = -ENOSPC;
 129
 130         inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
 131         if (inode) {
 132                 int l = strlen(symname)+1;
 133                 error = page_symlink(inode, symname, l);
 134                 if (!error) {
 135                         if (dir->i_mode & S_ISGID)
 136                                 inode->i_gid = dir->i_gid;
 137                         d_instantiate(dentry, inode);
 138                         dget(dentry);
 139                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 140                 } else
 141                         iput(inode);
 142         }
 143         return error;
 144 }
 145
 146 static const struct inode_operations ramfs_dir_inode_operations = {
 147         .create         = ramfs_create,
 148         .lookup         = simple_lookup,
 149         .link           = simple_link,
 150         .unlink         = simple_unlink,
 151         .symlink        = ramfs_symlink,
 152         .mkdir          = ramfs_mkdir,
 153         .rmdir          = simple_rmdir,
 154         .mknod          = ramfs_mknod,
 155         .rename         = simple_rename,
 156 };
 157
 158 static const struct super_operations ramfs_ops = {
 159         .statfs         = simple_statfs,
 160         .drop_inode     = generic_delete_inode,
 161 };
 162
 163 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
 164 {
 165         struct inode * inode;
 166         struct dentry * root;
 167
 168         sb->s_maxbytes = MAX_LFS_FILESIZE;
 169         sb->s_blocksize = PAGE_CACHE_SIZE;
 170         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 171         sb->s_magic = RAMFS_MAGIC;
 172         sb->s_op = &ramfs_ops;
 173         sb->s_time_gran = 1;
 174         inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
 175         if (!inode)
 176                 return -ENOMEM;
 177
 178         root = d_alloc_root(inode);
 179         if (!root) {
 180                 iput(inode);
 181                 return -ENOMEM;
 182         }
 183         sb->s_root = root;
 184         return 0;
 185 }
 186
 187 int ramfs_get_sb(struct file_system_type *fs_type,
 188         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 189 {
 190         return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
 191 }
 192
 193 static int rootfs_get_sb(struct file_system_type *fs_type,
 194         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 195 {
 196         return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super,
 197                             mnt);
 198 }
 199
 200 static struct file_system_type ramfs_fs_type = {
 201         .name           = "ramfs",
 202         .get_sb         = ramfs_get_sb,
 203         .kill_sb        = kill_litter_super,
 204 };
 205 static struct file_system_type rootfs_fs_type = {
 206         .name           = "rootfs",
 207         .get_sb         = rootfs_get_sb,
 208         .kill_sb        = kill_litter_super,
 209 };
 210
 211 static int __init init_ramfs_fs(void)
 212 {
 213         return register_filesystem(&ramfs_fs_type);
 214 }
 215
 216 static void __exit exit_ramfs_fs(void)
 217 {
 218         unregister_filesystem(&ramfs_fs_type);
 219 }
 220
 221 module_init(init_ramfs_fs)
 222 module_exit(exit_ramfs_fs)
 223
 224 int __init init_rootfs(void)
 225 {
 226         return register_filesystem(&rootfs_fs_type);
 227 }
 228
 229 MODULE_LICENSE("GPL");