/* Block- or MTD-based romfs
   *
   * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * Derived from: ROMFS file system, Linux implementation
   *
   * Copyright © 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
   *
   * Using parts of the minix filesystem
   * Copyright © 1991, 1992  Linus Torvalds
   *
   * and parts of the affs filesystem additionally
   * Copyright © 1993  Ray Burr
   * Copyright © 1996  Hans-Joachim Widmaier
   *
   * Changes
   *					Changed for 2.1.19 modules
   *	Jan 1997			Initial release
   *	Jun 1997			2.1.43+ changes
   *					Proper page locking in readpage
   *					Changed to work with 2.1.45+ fs
   *	Jul 1997			Fixed follow_link
   *			2.1.47
   *					lookup shouldn't return -ENOENT
   *					from Horst von Brand:
   *					  fail on wrong checksum
   *					  double unlock_super was possible
   *					  correct namelen for statfs
   *					spotted by Bill Hawes:
   *					  readlink shouldn't iput()
   *	Jun 1998	2.1.106		from Avery Pennarun: glibc scandir()
   *					  exposed a problem in readdir
   *			2.1.107		code-freeze spellchecker run
   *	Aug 1998			2.1.118+ VFS changes
   *	Sep 1998	2.1.122		another VFS change (follow_link)
   *	Apr 1999	2.2.7		no more EBADF checking in
   *					  lookup/readdir, use ERR_PTR
   *	Jun 1999	2.3.6		d_alloc_root use changed
   *			2.3.9		clean up usage of ENOENT/negative
   *					  dentries in lookup
   *					clean up page flags setting
   *					  (error, uptodate, locking) in
   *					  in readpage
   *					use init_special_inode for
   *					  fifos/sockets (and streamline) in
   *					  read_inode, fix _ops table order
   *	Aug 1999	2.3.16		__initfunc() => __init change
   *	Oct 1999	2.3.24		page->owner hack obsoleted
   *	Nov 1999	2.3.27		2.3.25+ page->offset => index change
   *
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>
  #include <linux/string.h>
  #include <linux/fs.h>
  #include <linux/time.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/blkdev.h>
  #include <linux/parser.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/statfs.h>
  #include <linux/mtd/super.h>
  #include <linux/ctype.h>
  #include <linux/highmem.h>
  #include <linux/pagemap.h>
  #include <linux/uaccess.h>
  #include "internal.h"
  
  static struct kmem_cache *romfs_inode_cachep;
  
  static const umode_t romfs_modemap[8] = {
  	0,			/* hard link */
  	S_IFDIR  | 0644,	/* directory */
  	S_IFREG  | 0644,	/* regular file */
  	S_IFLNK  | 0777,	/* symlink */
  	S_IFBLK  | 0600,	/* blockdev */
  	S_IFCHR  | 0600,	/* chardev */
  	S_IFSOCK | 0644,	/* socket */
  	S_IFIFO  | 0644		/* FIFO */
  };
  
  static const unsigned char romfs_dtype_table[] = {
  	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
  };
  
  static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
  
  /*
   * read a page worth of data from the image
   */
  static int romfs_readpage(struct file *file, struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	loff_t offset, size;
  	unsigned long fillsize, pos;
  	void *buf;
  	int ret;
  
  	buf = kmap(page);
  	if (!buf)
  		return -ENOMEM;
  
  	/* 32 bit warning -- but not for us :) */
  	offset = page_offset(page);
  	size = i_size_read(inode);
  	fillsize = 0;
  	ret = 0;
  	if (offset < size) {
  		size -= offset;
  		fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
  
  		pos = ROMFS_I(inode)->i_dataoffset + offset;
  
  		ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
  		if (ret < 0) {
  			SetPageError(page);
  			fillsize = 0;
  			ret = -EIO;
  		}
  	}
  
  	if (fillsize < PAGE_SIZE)
  		memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
  	if (ret == 0)
  		SetPageUptodate(page);
  
  	flush_dcache_page(page);
  	kunmap(page);
  	unlock_page(page);
  	return ret;
  }
  
  static const struct address_space_operations romfs_aops = {
  	.readpage	= romfs_readpage
  };
  
  /*
   * read the entries from a directory
   */

  static int romfs_readdir(struct file *file, struct dir_context *ctx)

  {

  	struct inode *i = file_inode(file);

  	struct romfs_inode ri;
  	unsigned long offset, maxoff;
  	int j, ino, nextfh;

  	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
  	int ret;
  
  	maxoff = romfs_maxsize(i->i_sb);

  	offset = ctx->pos;

  	if (!offset) {
  		offset = i->i_ino & ROMFH_MASK;
  		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
  		if (ret < 0)
  			goto out;
  		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
  	}
  
  	/* Not really failsafe, but we are read-only... */
  	for (;;) {
  		if (!offset || offset >= maxoff) {
  			offset = maxoff;

  			ctx->pos = offset;

  			goto out;
  		}

  		ctx->pos = offset;

  
  		/* Fetch inode info */
  		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
  		if (ret < 0)
  			goto out;
  
  		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
  				      sizeof(fsname) - 1);
  		if (j < 0)
  			goto out;
  
  		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
  		if (ret < 0)
  			goto out;
  		fsname[j] = '\0';
  
  		ino = offset;
  		nextfh = be32_to_cpu(ri.next);
  		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
  			ino = be32_to_cpu(ri.spec);

  		if (!dir_emit(ctx, fsname, j, ino,
  			    romfs_dtype_table[nextfh & ROMFH_TYPE]))

  			goto out;

  		offset = nextfh & ROMFH_MASK;
  	}

  out:

  	return 0;

  }
  
  /*
   * look up an entry in a directory
   */
  static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,

  				   unsigned int flags)

  {
  	unsigned long offset, maxoff;
  	struct inode *inode;
  	struct romfs_inode ri;
  	const char *name;		/* got from dentry */
  	int len, ret;
  
  	offset = dir->i_ino & ROMFH_MASK;
  	ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
  	if (ret < 0)
  		goto error;
  
  	/* search all the file entries in the list starting from the one
  	 * pointed to by the directory's special data */
  	maxoff = romfs_maxsize(dir->i_sb);
  	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
  
  	name = dentry->d_name.name;
  	len = dentry->d_name.len;
  
  	for (;;) {
  		if (!offset || offset >= maxoff)
  			goto out0;
  
  		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
  		if (ret < 0)
  			goto error;
  
  		/* try to match the first 16 bytes of name */

  		ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
  				       len);

  		if (ret < 0)
  			goto error;
  		if (ret == 1)
  			break;
  
  		/* next entry */
  		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
  	}
  
  	/* Hard link handling */
  	if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
  		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
  
  	inode = romfs_iget(dir->i_sb, offset);
  	if (IS_ERR(inode)) {
  		ret = PTR_ERR(inode);
  		goto error;
  	}
  	goto outi;
  
  	/*
  	 * it's a bit funky, _lookup needs to return an error code
  	 * (negative) or a NULL, both as a dentry.  ENOENT should not
  	 * be returned, instead we need to create a negative dentry by
  	 * d_add(dentry, NULL); and return 0 as no error.
  	 * (Although as I see, it only matters on writable file
  	 * systems).
  	 */
  out0:
  	inode = NULL;
  outi:
  	d_add(dentry, inode);
  	ret = 0;
  error:
  	return ERR_PTR(ret);
  }
  
  static const struct file_operations romfs_dir_operations = {
  	.read		= generic_read_dir,

  	.iterate	= romfs_readdir,

  	.llseek		= default_llseek,

  };

  static const struct inode_operations romfs_dir_inode_operations = {

  	.lookup		= romfs_lookup,
  };
  
  /*
   * get a romfs inode based on its position in the image (which doubles as the
   * inode number)
   */
  static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
  {
  	struct romfs_inode_info *inode;
  	struct romfs_inode ri;
  	struct inode *i;
  	unsigned long nlen;

  	unsigned nextfh;
  	int ret;

  	umode_t mode;
  
  	/* we might have to traverse a chain of "hard link" file entries to get
  	 * to the actual file */
  	for (;;) {
  		ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
  		if (ret < 0)
  			goto error;
  
  		/* XXX: do romfs_checksum here too (with name) */
  
  		nextfh = be32_to_cpu(ri.next);
  		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
  			break;
  
  		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
  	}
  
  	/* determine the length of the filename */
  	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
  	if (IS_ERR_VALUE(nlen))
  		goto eio;
  
  	/* get an inode for this image position */
  	i = iget_locked(sb, pos);
  	if (!i)
  		return ERR_PTR(-ENOMEM);
  
  	if (!(i->i_state & I_NEW))
  		return i;
  
  	/* precalculate the data offset */
  	inode = ROMFS_I(i);
  	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
  	inode->i_dataoffset = pos + inode->i_metasize;

  	set_nlink(i, 1);		/* Hard to decide.. */

  	i->i_size = be32_to_cpu(ri.size);
  	i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
  	i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
  
  	/* set up mode and ops */
  	mode = romfs_modemap[nextfh & ROMFH_TYPE];
  
  	switch (nextfh & ROMFH_TYPE) {
  	case ROMFH_DIR:
  		i->i_size = ROMFS_I(i)->i_metasize;
  		i->i_op = &romfs_dir_inode_operations;
  		i->i_fop = &romfs_dir_operations;
  		if (nextfh & ROMFH_EXEC)
  			mode |= S_IXUGO;
  		break;
  	case ROMFH_REG:
  		i->i_fop = &romfs_ro_fops;
  		i->i_data.a_ops = &romfs_aops;

  		if (nextfh & ROMFH_EXEC)
  			mode |= S_IXUGO;
  		break;
  	case ROMFH_SYM:
  		i->i_op = &page_symlink_inode_operations;

  		inode_nohighmem(i);

  		i->i_data.a_ops = &romfs_aops;
  		mode |= S_IRWXUGO;
  		break;
  	default:
  		/* depending on MBZ for sock/fifos */
  		nextfh = be32_to_cpu(ri.spec);
  		init_special_inode(i, mode, MKDEV(nextfh >> 16,
  						  nextfh & 0xffff));
  		break;
  	}
  
  	i->i_mode = mode;
  
  	unlock_new_inode(i);
  	return i;
  
  eio:
  	ret = -EIO;
  error:

  	pr_err("read error for inode 0x%lx
  ", pos);

  	return ERR_PTR(ret);
  }
  
  /*
   * allocate a new inode
   */
  static struct inode *romfs_alloc_inode(struct super_block *sb)
  {
  	struct romfs_inode_info *inode;

  	inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
  	return inode ? &inode->vfs_inode : NULL;
  }
  
  /*
   * return a spent inode to the slab cache
   */

  static void romfs_i_callback(struct rcu_head *head)

  {

  	struct inode *inode = container_of(head, struct inode, i_rcu);

  	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
  }

  static void romfs_destroy_inode(struct inode *inode)
  {
  	call_rcu(&inode->i_rcu, romfs_i_callback);
  }

  /*
   * get filesystem statistics
   */
  static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
  {

  	struct super_block *sb = dentry->d_sb;
  	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

  	buf->f_type = ROMFS_MAGIC;
  	buf->f_namelen = ROMFS_MAXFN;
  	buf->f_bsize = ROMBSIZE;
  	buf->f_bfree = buf->f_bavail = buf->f_ffree;
  	buf->f_blocks =
  		(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;

  	buf->f_fsid.val[0] = (u32)id;
  	buf->f_fsid.val[1] = (u32)(id >> 32);

  	return 0;
  }
  
  /*
   * remounting must involve read-only
   */
  static int romfs_remount(struct super_block *sb, int *flags, char *data)
  {

  	sync_filesystem(sb);

  	*flags |= MS_RDONLY;
  	return 0;
  }
  
  static const struct super_operations romfs_super_ops = {
  	.alloc_inode	= romfs_alloc_inode,
  	.destroy_inode	= romfs_destroy_inode,
  	.statfs		= romfs_statfs,
  	.remount_fs	= romfs_remount,
  };
  
  /*
   * checksum check on part of a romfs filesystem
   */
  static __u32 romfs_checksum(const void *data, int size)
  {
  	const __be32 *ptr = data;
  	__u32 sum;
  
  	sum = 0;
  	size >>= 2;
  	while (size > 0) {
  		sum += be32_to_cpu(*ptr++);
  		size--;
  	}
  	return sum;
  }
  
  /*
   * fill in the superblock
   */
  static int romfs_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct romfs_super_block *rsb;
  	struct inode *root;
  	unsigned long pos, img_size;
  	const char *storage;
  	size_t len;
  	int ret;
  
  #ifdef CONFIG_BLOCK
  	if (!sb->s_mtd) {
  		sb_set_blocksize(sb, ROMBSIZE);
  	} else {
  		sb->s_blocksize = ROMBSIZE;
  		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
  	}
  #endif
  
  	sb->s_maxbytes = 0xFFFFFFFF;
  	sb->s_magic = ROMFS_MAGIC;
  	sb->s_flags |= MS_RDONLY | MS_NOATIME;
  	sb->s_op = &romfs_super_ops;
  
  	/* read the image superblock and check it */
  	rsb = kmalloc(512, GFP_KERNEL);
  	if (!rsb)
  		return -ENOMEM;
  
  	sb->s_fs_info = (void *) 512;
  	ret = romfs_dev_read(sb, 0, rsb, 512);
  	if (ret < 0)
  		goto error_rsb;
  
  	img_size = be32_to_cpu(rsb->size);
  
  	if (sb->s_mtd && img_size > sb->s_mtd->size)
  		goto error_rsb_inval;
  
  	sb->s_fs_info = (void *) img_size;
  
  	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
  	    img_size < ROMFH_SIZE) {
  		if (!silent)

  			pr_warn("VFS: Can't find a romfs filesystem on dev %s.
  ",

  			       sb->s_id);
  		goto error_rsb_inval;
  	}
  
  	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {

  		pr_err("bad initial checksum on dev %s.
  ", sb->s_id);

  		goto error_rsb_inval;
  	}
  
  	storage = sb->s_mtd ? "MTD" : "the block layer";
  
  	len = strnlen(rsb->name, ROMFS_MAXFN);
  	if (!silent)

  		pr_notice("Mounting image '%*.*s' through %s
  ",
  			  (unsigned) len, (unsigned) len, rsb->name, storage);

  
  	kfree(rsb);
  	rsb = NULL;
  
  	/* find the root directory */
  	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
  
  	root = romfs_iget(sb, pos);

  	if (IS_ERR(root))

  		return PTR_ERR(root);

  	sb->s_root = d_make_root(root);

  	if (!sb->s_root)

  		return -ENOMEM;

  
  	return 0;

  error_rsb_inval:
  	ret = -EINVAL;
  error_rsb:

  	kfree(rsb);

  	return ret;
  }
  
  /*
   * get a superblock for mounting
   */

  static struct dentry *romfs_mount(struct file_system_type *fs_type,

  			int flags, const char *dev_name,

  			void *data)

  {

  	struct dentry *ret = ERR_PTR(-EINVAL);

  
  #ifdef CONFIG_ROMFS_ON_MTD

  	ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);

  #endif
  #ifdef CONFIG_ROMFS_ON_BLOCK

  	if (ret == ERR_PTR(-EINVAL))
  		ret = mount_bdev(fs_type, flags, dev_name, data,
  				  romfs_fill_super);

  #endif
  	return ret;
  }
  
  /*
   * destroy a romfs superblock in the appropriate manner
   */
  static void romfs_kill_sb(struct super_block *sb)
  {
  #ifdef CONFIG_ROMFS_ON_MTD
  	if (sb->s_mtd) {
  		kill_mtd_super(sb);
  		return;
  	}
  #endif
  #ifdef CONFIG_ROMFS_ON_BLOCK
  	if (sb->s_bdev) {
  		kill_block_super(sb);
  		return;
  	}
  #endif
  }
  
  static struct file_system_type romfs_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "romfs",

  	.mount		= romfs_mount,

  	.kill_sb	= romfs_kill_sb,
  	.fs_flags	= FS_REQUIRES_DEV,
  };

  MODULE_ALIAS_FS("romfs");

  
  /*
   * inode storage initialiser
   */
  static void romfs_i_init_once(void *_inode)
  {
  	struct romfs_inode_info *inode = _inode;
  
  	inode_init_once(&inode->vfs_inode);
  }
  
  /*
   * romfs module initialisation
   */
  static int __init init_romfs_fs(void)
  {
  	int ret;

  	pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.
  ");

  
  	romfs_inode_cachep =
  		kmem_cache_create("romfs_i",
  				  sizeof(struct romfs_inode_info), 0,

  				  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
  				  SLAB_ACCOUNT, romfs_i_init_once);

  
  	if (!romfs_inode_cachep) {

  		pr_err("Failed to initialise inode cache
  ");

  		return -ENOMEM;
  	}
  	ret = register_filesystem(&romfs_fs_type);
  	if (ret) {

  		pr_err("Failed to register filesystem
  ");

  		goto error_register;
  	}
  	return 0;
  
  error_register:
  	kmem_cache_destroy(romfs_inode_cachep);
  	return ret;
  }
  
  /*
   * romfs module removal
   */
  static void __exit exit_romfs_fs(void)
  {
  	unregister_filesystem(&romfs_fs_type);

  	/*
  	 * Make sure all delayed rcu free inodes are flushed before we
  	 * destroy cache.
  	 */
  	rcu_barrier();

  	kmem_cache_destroy(romfs_inode_cachep);
  }
  
  module_init(init_romfs_fs);
  module_exit(exit_romfs_fs);
  
  MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
  MODULE_AUTHOR("Red Hat, Inc.");
  MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */