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 struct super_operations ramfs_ops; 44 static 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_blksize = PAGE_CACHE_SIZE; 62 inode->i_blocks = 0; 63 inode->i_mapping->a_ops = &ramfs_aops; 64 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; 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 inode->i_nlink++; 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 dir->i_nlink++; 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 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 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 struct super_block *ramfs_get_sb(struct file_system_type *fs_type, 189 int flags, const char *dev_name, void *data) 190 { 191 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super); 192 } 193 194 static struct super_block *rootfs_get_sb(struct file_system_type *fs_type, 195 int flags, const char *dev_name, void *data) 196 { 197 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); 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"); 230