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 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_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_blocks = 0; 61 inode->i_mapping->a_ops = &ramfs_aops; 62 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; 63 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 64 switch (mode & S_IFMT) { 65 default: 66 init_special_inode(inode, mode, dev); 67 break; 68 case S_IFREG: 69 inode->i_op = &ramfs_file_inode_operations; 70 inode->i_fop = &ramfs_file_operations; 71 break; 72 case S_IFDIR: 73 inode->i_op = &ramfs_dir_inode_operations; 74 inode->i_fop = &simple_dir_operations; 75 76 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 77 inc_nlink(inode); 78 break; 79 case S_IFLNK: 80 inode->i_op = &page_symlink_inode_operations; 81 break; 82 } 83 } 84 return inode; 85 } 86 87 /* 88 * File creation. Allocate an inode, and we're done.. 89 */ 90 /* SMP-safe */ 91 static int 92 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) 93 { 94 struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev); 95 int error = -ENOSPC; 96 97 if (inode) { 98 if (dir->i_mode & S_ISGID) { 99 inode->i_gid = dir->i_gid; 100 if (S_ISDIR(mode)) 101 inode->i_mode |= S_ISGID; 102 } 103 d_instantiate(dentry, inode); 104 dget(dentry); /* Extra count - pin the dentry in core */ 105 error = 0; 106 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 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 inc_nlink(dir); 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 dir->i_mtime = dir->i_ctime = CURRENT_TIME; 139 } else 140 iput(inode); 141 } 142 return error; 143 } 144 145 static const struct inode_operations ramfs_dir_inode_operations = { 146 .create = ramfs_create, 147 .lookup = simple_lookup, 148 .link = simple_link, 149 .unlink = simple_unlink, 150 .symlink = ramfs_symlink, 151 .mkdir = ramfs_mkdir, 152 .rmdir = simple_rmdir, 153 .mknod = ramfs_mknod, 154 .rename = simple_rename, 155 }; 156 157 static const struct super_operations ramfs_ops = { 158 .statfs = simple_statfs, 159 .drop_inode = generic_delete_inode, 160 }; 161 162 static int ramfs_fill_super(struct super_block * sb, void * data, int silent) 163 { 164 struct inode * inode; 165 struct dentry * root; 166 167 sb->s_maxbytes = MAX_LFS_FILESIZE; 168 sb->s_blocksize = PAGE_CACHE_SIZE; 169 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 170 sb->s_magic = RAMFS_MAGIC; 171 sb->s_op = &ramfs_ops; 172 sb->s_time_gran = 1; 173 inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0); 174 if (!inode) 175 return -ENOMEM; 176 177 root = d_alloc_root(inode); 178 if (!root) { 179 iput(inode); 180 return -ENOMEM; 181 } 182 sb->s_root = root; 183 return 0; 184 } 185 186 int ramfs_get_sb(struct file_system_type *fs_type, 187 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 188 { 189 return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt); 190 } 191 192 static int rootfs_get_sb(struct file_system_type *fs_type, 193 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 194 { 195 return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super, 196 mnt); 197 } 198 199 static struct file_system_type ramfs_fs_type = { 200 .name = "ramfs", 201 .get_sb = ramfs_get_sb, 202 .kill_sb = kill_litter_super, 203 }; 204 static struct file_system_type rootfs_fs_type = { 205 .name = "rootfs", 206 .get_sb = rootfs_get_sb, 207 .kill_sb = kill_litter_super, 208 }; 209 210 static int __init init_ramfs_fs(void) 211 { 212 return register_filesystem(&ramfs_fs_type); 213 } 214 215 static void __exit exit_ramfs_fs(void) 216 { 217 unregister_filesystem(&ramfs_fs_type); 218 } 219 220 module_init(init_ramfs_fs) 221 module_exit(exit_ramfs_fs) 222 223 int __init init_rootfs(void) 224 { 225 return register_filesystem(&rootfs_fs_type); 226 } 227 228 MODULE_LICENSE("GPL"); 229