/*
   * 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/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 <linux/parser.h>

  #include <linux/magic.h>

  #include <linux/slab.h>

  #include <asm/uaccess.h>

  #include "internal.h"

  #define RAMFS_DEFAULT_MODE	0755

  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 = {

  	.name		= "ramfs",

  	.ra_pages	= 0,	/* No readahead */

  	.capabilities	= BDI_CAP_NO_ACCT_AND_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,

  				const struct inode *dir, umode_t mode, dev_t dev)

  {
  	struct inode * inode = new_inode(sb);
  
  	if (inode) {

  		inode->i_ino = get_next_ino();

  		inode_init_owner(inode, dir, mode);

  		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);

  		mapping_set_unevictable(inode->i_mapping);

  		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, umode_t mode, dev_t dev)

  {

  	struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);

  	int error = -ENOSPC;
  
  	if (inode) {

  		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, umode_t 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, umode_t 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, dir, S_IFLNK|S_IRWXUGO, 0);

  	if (inode) {
  		int l = strlen(symname)+1;
  		error = page_symlink(inode, symname, l);
  		if (!error) {

  			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,

  	.show_options	= generic_show_options,
  };
  
  struct ramfs_mount_opts {
  	umode_t mode;
  };
  
  enum {
  	Opt_mode,
  	Opt_err
  };
  
  static const match_table_t tokens = {
  	{Opt_mode, "mode=%o"},
  	{Opt_err, NULL}
  };
  
  struct ramfs_fs_info {
  	struct ramfs_mount_opts mount_opts;

  };

  static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
  {
  	substring_t args[MAX_OPT_ARGS];
  	int option;
  	int token;
  	char *p;
  
  	opts->mode = RAMFS_DEFAULT_MODE;
  
  	while ((p = strsep(&data, ",")) != NULL) {
  		if (!*p)
  			continue;
  
  		token = match_token(p, tokens, args);
  		switch (token) {
  		case Opt_mode:
  			if (match_octal(&args[0], &option))
  				return -EINVAL;
  			opts->mode = option & S_IALLUGO;
  			break;

  		/*
  		 * We might like to report bad mount options here;
  		 * but traditionally ramfs has ignored all mount options,
  		 * and as it is used as a !CONFIG_SHMEM simple substitute
  		 * for tmpfs, better continue to ignore other mount options.
  		 */

  		}
  	}
  
  	return 0;
  }

  int ramfs_fill_super(struct super_block *sb, void *data, int silent)

  {

  	struct ramfs_fs_info *fsi;
  	struct inode *inode = NULL;
  	struct dentry *root;
  	int err;
  
  	save_mount_options(sb, data);
  
  	fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);

  	sb->s_fs_info = fsi;

  	if (!fsi) {
  		err = -ENOMEM;
  		goto fail;
  	}

  
  	err = ramfs_parse_options(data, &fsi->mount_opts);
  	if (err)
  		goto fail;

  	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, NULL, S_IFDIR | fsi->mount_opts.mode, 0);

  	if (!inode) {
  		err = -ENOMEM;
  		goto fail;
  	}

  
  	root = d_alloc_root(inode);

  	sb->s_root = root;

  	if (!root) {

  		err = -ENOMEM;
  		goto fail;

  	}

  	return 0;

  fail:
  	kfree(fsi);

  	sb->s_fs_info = NULL;

  	iput(inode);
  	return err;

  }

  struct dentry *ramfs_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)

  {

  	return mount_nodev(fs_type, flags, data, ramfs_fill_super);

  }

  static struct dentry *rootfs_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)

  {

  	return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);

  }

  static void ramfs_kill_sb(struct super_block *sb)
  {
  	kfree(sb->s_fs_info);
  	kill_litter_super(sb);
  }

  static struct file_system_type ramfs_fs_type = {
  	.name		= "ramfs",

  	.mount		= ramfs_mount,

  	.kill_sb	= ramfs_kill_sb,

  };
  static struct file_system_type rootfs_fs_type = {
  	.name		= "rootfs",

  	.mount		= rootfs_mount,

  	.kill_sb	= kill_litter_super,
  };
  
  static int __init init_ramfs_fs(void)
  {
  	return register_filesystem(&ramfs_fs_type);
  }

  module_init(init_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;

  }