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 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 int err; 227 228 err = bdi_init(&ramfs_backing_dev_info); 229 if (err) 230 return err; 231 232 err = register_filesystem(&rootfs_fs_type); 233 if (err) 234 bdi_destroy(&ramfs_backing_dev_info); 235 236 return err; 237 } 238 239 MODULE_LICENSE("GPL"); 240