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/init.h> 31 #include <linux/string.h> 32 #include <linux/smp_lock.h> 33 #include <linux/backing-dev.h> 34 #include <linux/ramfs.h> 35 36 #include <asm/uaccess.h> 37 #include "internal.h" 38 39 /* some random number */ 40 #define RAMFS_MAGIC 0x858458f6 41 42 static struct super_operations ramfs_ops; 43 static 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_DIRTY | BDI_CAP_NO_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_blksize = PAGE_CACHE_SIZE; 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 inode->i_nlink++; 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 } 108 return error; 109 } 110 111 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) 112 { 113 int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); 114 if (!retval) 115 dir->i_nlink++; 116 return retval; 117 } 118 119 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) 120 { 121 return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); 122 } 123 124 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 125 { 126 struct inode *inode; 127 int error = -ENOSPC; 128 129 inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0); 130 if (inode) { 131 int l = strlen(symname)+1; 132 error = page_symlink(inode, symname, l); 133 if (!error) { 134 if (dir->i_mode & S_ISGID) 135 inode->i_gid = dir->i_gid; 136 d_instantiate(dentry, inode); 137 dget(dentry); 138 } else 139 iput(inode); 140 } 141 return error; 142 } 143 144 static struct inode_operations ramfs_dir_inode_operations = { 145 .create = ramfs_create, 146 .lookup = simple_lookup, 147 .link = simple_link, 148 .unlink = simple_unlink, 149 .symlink = ramfs_symlink, 150 .mkdir = ramfs_mkdir, 151 .rmdir = simple_rmdir, 152 .mknod = ramfs_mknod, 153 .rename = simple_rename, 154 }; 155 156 static struct super_operations ramfs_ops = { 157 .statfs = simple_statfs, 158 .drop_inode = generic_delete_inode, 159 }; 160 161 static int ramfs_fill_super(struct super_block * sb, void * data, int silent) 162 { 163 struct inode * inode; 164 struct dentry * root; 165 166 sb->s_maxbytes = MAX_LFS_FILESIZE; 167 sb->s_blocksize = PAGE_CACHE_SIZE; 168 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 169 sb->s_magic = RAMFS_MAGIC; 170 sb->s_op = &ramfs_ops; 171 sb->s_time_gran = 1; 172 inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0); 173 if (!inode) 174 return -ENOMEM; 175 176 root = d_alloc_root(inode); 177 if (!root) { 178 iput(inode); 179 return -ENOMEM; 180 } 181 sb->s_root = root; 182 return 0; 183 } 184 185 struct super_block *ramfs_get_sb(struct file_system_type *fs_type, 186 int flags, const char *dev_name, void *data) 187 { 188 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super); 189 } 190 191 static struct super_block *rootfs_get_sb(struct file_system_type *fs_type, 192 int flags, const char *dev_name, void *data) 193 { 194 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); 195 } 196 197 static struct file_system_type ramfs_fs_type = { 198 .name = "ramfs", 199 .get_sb = ramfs_get_sb, 200 .kill_sb = kill_litter_super, 201 }; 202 static struct file_system_type rootfs_fs_type = { 203 .name = "rootfs", 204 .get_sb = rootfs_get_sb, 205 .kill_sb = kill_litter_super, 206 }; 207 208 static int __init init_ramfs_fs(void) 209 { 210 return register_filesystem(&ramfs_fs_type); 211 } 212 213 static void __exit exit_ramfs_fs(void) 214 { 215 unregister_filesystem(&ramfs_fs_type); 216 } 217 218 module_init(init_ramfs_fs) 219 module_exit(exit_ramfs_fs) 220 221 int __init init_rootfs(void) 222 { 223 return register_filesystem(&rootfs_fs_type); 224 } 225 226 MODULE_LICENSE("GPL"); 227