/* * Resizable simple ram filesystem for Linux. * * Copyright (C) 2000 Linus Torvalds. * 2000 Transmeta Corp. * * Usage limits added by David Gibson, Linuxcare Australia. * This file is released under the GPL. */ /* * NOTE! This filesystem is probably most useful * not as a real filesystem, but as an example of * how virtual filesystems can be written. * * It doesn't get much simpler than this. Consider * that this file implements the full semantics of * a POSIX-compliant read-write filesystem. * * Note in particular how the filesystem does not * need to implement any data structures of its own * to keep track of the virtual data: using the VFS * caches is sufficient. */ #include <linux/module.h> #include <linux/fs.h> #include <linux/pagemap.h> #include <linux/highmem.h> #include <linux/time.h> #include <linux/init.h> #include <linux/string.h> #include <linux/backing-dev.h> #include <linux/ramfs.h> #include <linux/sched.h> #include <asm/uaccess.h> #include "internal.h" /* some random number */ #define RAMFS_MAGIC 0x858458f6 static const struct super_operations ramfs_ops; static const struct inode_operations ramfs_dir_inode_operations; static struct backing_dev_info ramfs_backing_dev_info = { .ra_pages = 0, /* No readahead */ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK | BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY | BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP, }; struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev) { struct inode * inode = new_inode(sb); if (inode) { inode->i_mode = mode; inode->i_uid = current->fsuid; inode->i_gid = current->fsgid; inode->i_blocks = 0; inode->i_mapping->a_ops = &ramfs_aops; inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; switch (mode & S_IFMT) { default: init_special_inode(inode, mode, dev); break; case S_IFREG: inode->i_op = &ramfs_file_inode_operations; inode->i_fop = &ramfs_file_operations; break; case S_IFDIR: inode->i_op = &ramfs_dir_inode_operations; inode->i_fop = &simple_dir_operations; /* directory inodes start off with i_nlink == 2 (for "." entry) */ inc_nlink(inode); break; case S_IFLNK: inode->i_op = &page_symlink_inode_operations; break; } } return inode; } /* * File creation. Allocate an inode, and we're done.. */ /* SMP-safe */ static int ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) { struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev); int error = -ENOSPC; if (inode) { if (dir->i_mode & S_ISGID) { inode->i_gid = dir->i_gid; if (S_ISDIR(mode)) inode->i_mode |= S_ISGID; } d_instantiate(dentry, inode); dget(dentry); /* Extra count - pin the dentry in core */ error = 0; dir->i_mtime = dir->i_ctime = CURRENT_TIME; } return error; } static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode) { int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); if (!retval) inc_nlink(dir); return retval; } static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) { return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); } static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) { struct inode *inode; int error = -ENOSPC; inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0); if (inode) { int l = strlen(symname)+1; error = page_symlink(inode, symname, l); if (!error) { if (dir->i_mode & S_ISGID) inode->i_gid = dir->i_gid; d_instantiate(dentry, inode); dget(dentry); dir->i_mtime = dir->i_ctime = CURRENT_TIME; } else iput(inode); } return error; } static const struct inode_operations ramfs_dir_inode_operations = { .create = ramfs_create, .lookup = simple_lookup, .link = simple_link, .unlink = simple_unlink, .symlink = ramfs_symlink, .mkdir = ramfs_mkdir, .rmdir = simple_rmdir, .mknod = ramfs_mknod, .rename = simple_rename, }; static const struct super_operations ramfs_ops = { .statfs = simple_statfs, .drop_inode = generic_delete_inode, }; static int ramfs_fill_super(struct super_block * sb, void * data, int silent) { struct inode * inode; struct dentry * root; sb->s_maxbytes = MAX_LFS_FILESIZE; sb->s_blocksize = PAGE_CACHE_SIZE; sb->s_blocksize_bits = PAGE_CACHE_SHIFT; sb->s_magic = RAMFS_MAGIC; sb->s_op = &ramfs_ops; sb->s_time_gran = 1; inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0); if (!inode) return -ENOMEM; root = d_alloc_root(inode); if (!root) { iput(inode); return -ENOMEM; } sb->s_root = root; return 0; } int ramfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt); } static int rootfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super, mnt); } static struct file_system_type ramfs_fs_type = { .name = "ramfs", .get_sb = ramfs_get_sb, .kill_sb = kill_litter_super, }; static struct file_system_type rootfs_fs_type = { .name = "rootfs", .get_sb = rootfs_get_sb, .kill_sb = kill_litter_super, }; static int __init init_ramfs_fs(void) { return register_filesystem(&ramfs_fs_type); } static void __exit exit_ramfs_fs(void) { unregister_filesystem(&ramfs_fs_type); } module_init(init_ramfs_fs) module_exit(exit_ramfs_fs) int __init init_rootfs(void) { int err; err = bdi_init(&ramfs_backing_dev_info); if (err) return err; err = register_filesystem(&rootfs_fs_type); if (err) bdi_destroy(&ramfs_backing_dev_info); return err; } MODULE_LICENSE("GPL");