/*
   *  linux/fs/ufs/ufs_dir.c
   *
   * Copyright (C) 1996
   * Adrian Rodriguez (adrian@franklins-tower.rutgers.edu)
   * Laboratory for Computer Science Research Computing Facility
   * Rutgers, The State University of New Jersey
   *
   * swab support by Francois-Rene Rideau <fare@tunes.org> 19970406
   *
   * 4.4BSD (FreeBSD) support added on February 1st 1998 by
   * Niels Kristian Bech Jensen <nkbj@image.dk> partially based
   * on code by Martin von Loewis <martin@mira.isdn.cs.tu-berlin.de>.

   *
   * Migration to usage of "page cache" on May 2006 by
   * Evgeniy Dushistov <dushistov@mail.ru> based on ext2 code base.

   */
  
  #include <linux/time.h>
  #include <linux/fs.h>

  #include <linux/swap.h>

  #include "ufs_fs.h"

  #include "ufs.h"

  #include "swab.h"
  #include "util.h"

  /*
   * NOTE! unlike strncmp, ufs_match returns 1 for success, 0 for failure.
   *
   * len <= UFS_MAXNAMLEN and de != NULL are guaranteed by caller.
   */
  static inline int ufs_match(struct super_block *sb, int len,

  		const unsigned char *name, struct ufs_dir_entry *de)

  {
  	if (len != ufs_get_de_namlen(sb, de))
  		return 0;
  	if (!de->d_ino)
  		return 0;
  	return !memcmp(name, de->d_name, len);
  }

  static int ufs_commit_chunk(struct page *page, loff_t pos, unsigned len)

  {

  	struct address_space *mapping = page->mapping;
  	struct inode *dir = mapping->host;

  	int err = 0;

  	dir->i_version++;

  	block_write_end(NULL, mapping, pos, len, len, page, NULL);
  	if (pos+len > dir->i_size) {
  		i_size_write(dir, pos+len);
  		mark_inode_dirty(dir);
  	}

  	if (IS_DIRSYNC(dir))
  		err = write_one_page(page, 1);
  	else
  		unlock_page(page);
  	return err;
  }

  static inline void ufs_put_page(struct page *page)
  {
  	kunmap(page);
  	page_cache_release(page);
  }

  static inline unsigned long ufs_dir_pages(struct inode *inode)
  {
  	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  }

  ino_t ufs_inode_by_name(struct inode *dir, const struct qstr *qstr)

  {
  	ino_t res = 0;
  	struct ufs_dir_entry *de;
  	struct page *page;
  	

  	de = ufs_find_entry(dir, qstr, &page);

  	if (de) {
  		res = fs32_to_cpu(dir->i_sb, de->d_ino);
  		ufs_put_page(page);

  	}

  	return res;

  }

  /* Releases the page */
  void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
  		  struct page *page, struct inode *inode)

  {

  	loff_t pos = page_offset(page) +
  			(char *) de - (char *) page_address(page);
  	unsigned len = fs16_to_cpu(dir->i_sb, de->d_reclen);

  	int err;

  	lock_page(page);

  	err = ufs_prepare_chunk(page, pos, len);

  	BUG_ON(err);

  	de->d_ino = cpu_to_fs32(dir->i_sb, inode->i_ino);
  	ufs_set_de_type(dir->i_sb, de, inode->i_mode);

  
  	err = ufs_commit_chunk(page, pos, len);

  	ufs_put_page(page);
  	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
  	mark_inode_dirty(dir);
  }

  static void ufs_check_page(struct page *page)
  {
  	struct inode *dir = page->mapping->host;
  	struct super_block *sb = dir->i_sb;
  	char *kaddr = page_address(page);
  	unsigned offs, rec_len;
  	unsigned limit = PAGE_CACHE_SIZE;

  	const unsigned chunk_mask = UFS_SB(sb)->s_uspi->s_dirblksize - 1;

  	struct ufs_dir_entry *p;
  	char *error;
  
  	if ((dir->i_size >> PAGE_CACHE_SHIFT) == page->index) {
  		limit = dir->i_size & ~PAGE_CACHE_MASK;

  		if (limit & chunk_mask)

  			goto Ebadsize;
  		if (!limit)
  			goto out;

  	}

  	for (offs = 0; offs <= limit - UFS_DIR_REC_LEN(1); offs += rec_len) {
  		p = (struct ufs_dir_entry *)(kaddr + offs);
  		rec_len = fs16_to_cpu(sb, p->d_reclen);
  
  		if (rec_len < UFS_DIR_REC_LEN(1))
  			goto Eshort;
  		if (rec_len & 3)
  			goto Ealign;
  		if (rec_len < UFS_DIR_REC_LEN(ufs_get_de_namlen(sb, p)))
  			goto Enamelen;

  		if (((offs + rec_len - 1) ^ offs) & ~chunk_mask)

  			goto Espan;
  		if (fs32_to_cpu(sb, p->d_ino) > (UFS_SB(sb)->s_uspi->s_ipg *
  						  UFS_SB(sb)->s_uspi->s_ncg))
  			goto Einumber;
  	}
  	if (offs != limit)
  		goto Eend;
  out:
  	SetPageChecked(page);
  	return;
  
  	/* Too bad, we had an error */
  
  Ebadsize:
  	ufs_error(sb, "ufs_check_page",
  		  "size of directory #%lu is not a multiple of chunk size",
  		  dir->i_ino
  	);
  	goto fail;
  Eshort:
  	error = "rec_len is smaller than minimal";
  	goto bad_entry;
  Ealign:
  	error = "unaligned directory entry";
  	goto bad_entry;
  Enamelen:
  	error = "rec_len is too small for name_len";
  	goto bad_entry;
  Espan:
  	error = "directory entry across blocks";
  	goto bad_entry;
  Einumber:
  	error = "inode out of bounds";
  bad_entry:
  	ufs_error (sb, "ufs_check_page", "bad entry in directory #%lu: %s - "
  		   "offset=%lu, rec_len=%d, name_len=%d",
  		   dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
  		   rec_len, ufs_get_de_namlen(sb, p));
  	goto fail;
  Eend:
  	p = (struct ufs_dir_entry *)(kaddr + offs);

  	ufs_error(sb, __func__,

  		   "entry in directory #%lu spans the page boundary"
  		   "offset=%lu",
  		   dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs);
  fail:
  	SetPageChecked(page);
  	SetPageError(page);
  }

  static struct page *ufs_get_page(struct inode *dir, unsigned long n)
  {
  	struct address_space *mapping = dir->i_mapping;

  	struct page *page = read_mapping_page(mapping, n, NULL);

  	if (!IS_ERR(page)) {

  		kmap(page);

  		if (!PageChecked(page))
  			ufs_check_page(page);
  		if (PageError(page))
  			goto fail;

  	}

  	return page;

  fail:
  	ufs_put_page(page);
  	return ERR_PTR(-EIO);

  }

  /*
   * Return the offset into page `page_nr' of the last valid
   * byte in that page, plus one.
   */
  static unsigned
  ufs_last_byte(struct inode *inode, unsigned long page_nr)

  {

  	unsigned last_byte = inode->i_size;
  
  	last_byte -= page_nr << PAGE_CACHE_SHIFT;
  	if (last_byte > PAGE_CACHE_SIZE)
  		last_byte = PAGE_CACHE_SIZE;
  	return last_byte;

  }

  static inline struct ufs_dir_entry *
  ufs_next_entry(struct super_block *sb, struct ufs_dir_entry *p)

  {

  	return (struct ufs_dir_entry *)((char *)p +
  					fs16_to_cpu(sb, p->d_reclen));

  }

  
  struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p)

  {

  	struct page *page = ufs_get_page(dir, 0);
  	struct ufs_dir_entry *de = NULL;

  	if (!IS_ERR(page)) {
  		de = ufs_next_entry(dir->i_sb,
  				    (struct ufs_dir_entry *)page_address(page));
  		*p = page;

  	}

  	return de;

  }

  /*
   *	ufs_find_entry()
   *
   * finds an entry in the specified directory with the wanted name. It
   * returns the page in which the entry was found, and the entry itself
   * (as a parameter - res_dir). Page is returned mapped and unlocked.
   * Entry is guaranteed to be valid.
   */

  struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,

  				     struct page **res_page)

  {

  	struct super_block *sb = dir->i_sb;

  	const unsigned char *name = qstr->name;

  	int namelen = qstr->len;

  	unsigned reclen = UFS_DIR_REC_LEN(namelen);
  	unsigned long start, n;
  	unsigned long npages = ufs_dir_pages(dir);
  	struct page *page = NULL;

  	struct ufs_inode_info *ui = UFS_I(dir);

  	struct ufs_dir_entry *de;

  	UFSD("ENTER, dir_ino %lu, name %s, namlen %u
  ", dir->i_ino, name, namelen);

  
  	if (npages == 0 || namelen > UFS_MAXNAMLEN)
  		goto out;
  
  	/* OFFSET_CACHE */
  	*res_page = NULL;

  	start = ui->i_dir_start_lookup;

  	if (start >= npages)
  		start = 0;
  	n = start;
  	do {
  		char *kaddr;
  		page = ufs_get_page(dir, n);
  		if (!IS_ERR(page)) {
  			kaddr = page_address(page);
  			de = (struct ufs_dir_entry *) kaddr;
  			kaddr += ufs_last_byte(dir, n) - reclen;
  			while ((char *) de <= kaddr) {
  				if (de->d_reclen == 0) {

  					ufs_error(dir->i_sb, __func__,

  						  "zero-length directory entry");
  					ufs_put_page(page);
  					goto out;
  				}
  				if (ufs_match(sb, namelen, name, de))
  					goto found;
  				de = ufs_next_entry(sb, de);
  			}
  			ufs_put_page(page);
  		}
  		if (++n >= npages)
  			n = 0;
  	} while (n != start);
  out:
  	return NULL;
  
  found:
  	*res_page = page;

  	ui->i_dir_start_lookup = n;

  	return de;

  }
  
  /*

   *	Parent is locked.

   */
  int ufs_add_link(struct dentry *dentry, struct inode *inode)
  {

  	struct inode *dir = dentry->d_parent->d_inode;

  	const unsigned char *name = dentry->d_name.name;

  	int namelen = dentry->d_name.len;

  	struct super_block *sb = dir->i_sb;
  	unsigned reclen = UFS_DIR_REC_LEN(namelen);

  	const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;

  	unsigned short rec_len, name_len;
  	struct page *page = NULL;
  	struct ufs_dir_entry *de;
  	unsigned long npages = ufs_dir_pages(dir);
  	unsigned long n;
  	char *kaddr;

  	loff_t pos;

  	int err;

  	UFSD("ENTER, name %s, namelen %u
  ", name, namelen);

  
  	/*
  	 * We take care of directory expansion in the same loop.
  	 * This code plays outside i_size, so it locks the page
  	 * to protect that region.
  	 */
  	for (n = 0; n <= npages; n++) {
  		char *dir_end;
  
  		page = ufs_get_page(dir, n);
  		err = PTR_ERR(page);
  		if (IS_ERR(page))
  			goto out;
  		lock_page(page);
  		kaddr = page_address(page);
  		dir_end = kaddr + ufs_last_byte(dir, n);
  		de = (struct ufs_dir_entry *)kaddr;
  		kaddr += PAGE_CACHE_SIZE - reclen;
  		while ((char *)de <= kaddr) {
  			if ((char *)de == dir_end) {
  				/* We hit i_size */
  				name_len = 0;

  				rec_len = chunk_size;
  				de->d_reclen = cpu_to_fs16(sb, chunk_size);

  				de->d_ino = 0;
  				goto got_it;

  			}

  			if (de->d_reclen == 0) {

  				ufs_error(dir->i_sb, __func__,

  					  "zero-length directory entry");
  				err = -EIO;
  				goto out_unlock;
  			}
  			err = -EEXIST;
  			if (ufs_match(sb, namelen, name, de))
  				goto out_unlock;
  			name_len = UFS_DIR_REC_LEN(ufs_get_de_namlen(sb, de));
  			rec_len = fs16_to_cpu(sb, de->d_reclen);
  			if (!de->d_ino && rec_len >= reclen)
  				goto got_it;
  			if (rec_len >= name_len + reclen)
  				goto got_it;
  			de = (struct ufs_dir_entry *) ((char *) de + rec_len);

  		}

  		unlock_page(page);
  		ufs_put_page(page);

  	}

  	BUG();
  	return -EINVAL;
  
  got_it:

  	pos = page_offset(page) +
  			(char*)de - (char*)page_address(page);

  	err = ufs_prepare_chunk(page, pos, rec_len);

  	if (err)
  		goto out_unlock;

  	if (de->d_ino) {

  		struct ufs_dir_entry *de1 =
  			(struct ufs_dir_entry *) ((char *) de + name_len);
  		de1->d_reclen = cpu_to_fs16(sb, rec_len - name_len);
  		de->d_reclen = cpu_to_fs16(sb, name_len);

  		de = de1;
  	}

  	ufs_set_de_namlen(sb, de, namelen);

  	memcpy(de->d_name, name, namelen + 1);

  	de->d_ino = cpu_to_fs32(sb, inode->i_ino);
  	ufs_set_de_type(sb, de, inode->i_mode);

  	err = ufs_commit_chunk(page, pos, rec_len);

  	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;

  	mark_inode_dirty(dir);

  	/* OFFSET_CACHE */
  out_put:
  	ufs_put_page(page);
  out:
  	return err;
  out_unlock:
  	unlock_page(page);
  	goto out_put;
  }
  
  static inline unsigned
  ufs_validate_entry(struct super_block *sb, char *base,
  		   unsigned offset, unsigned mask)
  {
  	struct ufs_dir_entry *de = (struct ufs_dir_entry*)(base + offset);
  	struct ufs_dir_entry *p = (struct ufs_dir_entry*)(base + (offset&mask));
  	while ((char*)p < (char*)de) {
  		if (p->d_reclen == 0)
  			break;
  		p = ufs_next_entry(sb, p);
  	}
  	return (char *)p - base;
  }

  
  /*
   * This is blatantly stolen from ext2fs
   */
  static int
  ufs_readdir(struct file *filp, void *dirent, filldir_t filldir)
  {
  	loff_t pos = filp->f_pos;

  	struct inode *inode = filp->f_path.dentry->d_inode;

  	struct super_block *sb = inode->i_sb;
  	unsigned int offset = pos & ~PAGE_CACHE_MASK;
  	unsigned long n = pos >> PAGE_CACHE_SHIFT;
  	unsigned long npages = ufs_dir_pages(inode);

  	unsigned chunk_mask = ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);

  	int need_revalidate = filp->f_version != inode->i_version;
  	unsigned flags = UFS_SB(sb)->s_flags;

  	UFSD("BEGIN
  ");

  
  	if (pos > inode->i_size - UFS_DIR_REC_LEN(1))
  		return 0;
  
  	for ( ; n < npages; n++, offset = 0) {
  		char *kaddr, *limit;
  		struct ufs_dir_entry *de;
  
  		struct page *page = ufs_get_page(inode, n);
  
  		if (IS_ERR(page)) {

  			ufs_error(sb, __func__,

  				  "bad page in #%lu",
  				  inode->i_ino);
  			filp->f_pos += PAGE_CACHE_SIZE - offset;
  			return -EIO;
  		}
  		kaddr = page_address(page);
  		if (unlikely(need_revalidate)) {
  			if (offset) {
  				offset = ufs_validate_entry(sb, kaddr, offset, chunk_mask);
  				filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset;
  			}
  			filp->f_version = inode->i_version;
  			need_revalidate = 0;
  		}
  		de = (struct ufs_dir_entry *)(kaddr+offset);
  		limit = kaddr + ufs_last_byte(inode, n) - UFS_DIR_REC_LEN(1);
  		for ( ;(char*)de <= limit; de = ufs_next_entry(sb, de)) {
  			if (de->d_reclen == 0) {

  				ufs_error(sb, __func__,

  					"zero-length directory entry");
  				ufs_put_page(page);
  				return -EIO;
  			}
  			if (de->d_ino) {
  				int over;
  				unsigned char d_type = DT_UNKNOWN;
  
  				offset = (char *)de - kaddr;

  				UFSD("filldir(%s,%u)
  ", de->d_name,
  				      fs32_to_cpu(sb, de->d_ino));
  				UFSD("namlen %u
  ", ufs_get_de_namlen(sb, de));

  
  				if ((flags & UFS_DE_MASK) == UFS_DE_44BSD)
  					d_type = de->d_u.d_44.d_type;
  
  				over = filldir(dirent, de->d_name,
  					       ufs_get_de_namlen(sb, de),
  						(n<<PAGE_CACHE_SHIFT) | offset,
  					       fs32_to_cpu(sb, de->d_ino), d_type);
  				if (over) {
  					ufs_put_page(page);
  					return 0;
  				}
  			}
  			filp->f_pos += fs16_to_cpu(sb, de->d_reclen);
  		}
  		ufs_put_page(page);
  	}

  	return 0;
  }

  /*
   * ufs_delete_entry deletes a directory entry by merging it with the
   * previous entry.
   */

  int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
  		     struct page * page)

  {

  	struct super_block *sb = inode->i_sb;

  	char *kaddr = page_address(page);

  	unsigned from = ((char*)dir - kaddr) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);

  	unsigned to = ((char*)dir - kaddr) + fs16_to_cpu(sb, dir->d_reclen);

  	loff_t pos;

  	struct ufs_dir_entry *pde = NULL;
  	struct ufs_dir_entry *de = (struct ufs_dir_entry *) (kaddr + from);
  	int err;

  	UFSD("ENTER
  ");

  	UFSD("ino %u, reclen %u, namlen %u, name %s
  ",

  	      fs32_to_cpu(sb, de->d_ino),
  	      fs16_to_cpu(sb, de->d_reclen),

  	      ufs_get_de_namlen(sb, de), de->d_name);

  
  	while ((char*)de < (char*)dir) {
  		if (de->d_reclen == 0) {

  			ufs_error(inode->i_sb, __func__,

  				  "zero-length directory entry");
  			err = -EIO;
  			goto out;

  		}

  		pde = de;
  		de = ufs_next_entry(sb, de);

  	}

  	if (pde)
  		from = (char*)pde - (char*)page_address(page);

  
  	pos = page_offset(page) + from;

  	lock_page(page);

  	err = ufs_prepare_chunk(page, pos, to - from);

  	BUG_ON(err);
  	if (pde)

  		pde->d_reclen = cpu_to_fs16(sb, to - from);

  	dir->d_ino = 0;

  	err = ufs_commit_chunk(page, pos, to - from);

  	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
  	mark_inode_dirty(inode);
  out:
  	ufs_put_page(page);

  	UFSD("EXIT
  ");

  	return err;

  }
  
  int ufs_make_empty(struct inode * inode, struct inode *dir)
  {
  	struct super_block * sb = dir->i_sb;

  	struct address_space *mapping = inode->i_mapping;
  	struct page *page = grab_cache_page(mapping, 0);

  	const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;

  	struct ufs_dir_entry * de;

  	char *base;

  	int err;

  	if (!page)
  		return -ENOMEM;

  	err = ufs_prepare_chunk(page, 0, chunk_size);

  	if (err) {
  		unlock_page(page);
  		goto fail;
  	}

  	kmap(page);

  	base = (char*)page_address(page);
  	memset(base, 0, PAGE_CACHE_SIZE);
  
  	de = (struct ufs_dir_entry *) base;

  	de->d_ino = cpu_to_fs32(sb, inode->i_ino);
  	ufs_set_de_type(sb, de, inode->i_mode);
  	ufs_set_de_namlen(sb, de, 1);
  	de->d_reclen = cpu_to_fs16(sb, UFS_DIR_REC_LEN(1));
  	strcpy (de->d_name, ".");
  	de = (struct ufs_dir_entry *)
  		((char *)de + fs16_to_cpu(sb, de->d_reclen));
  	de->d_ino = cpu_to_fs32(sb, dir->i_ino);
  	ufs_set_de_type(sb, de, dir->i_mode);

  	de->d_reclen = cpu_to_fs16(sb, chunk_size - UFS_DIR_REC_LEN(1));

  	ufs_set_de_namlen(sb, de, 2);
  	strcpy (de->d_name, "..");

  	kunmap(page);

  	err = ufs_commit_chunk(page, 0, chunk_size);

  fail:

  	page_cache_release(page);
  	return err;

  }
  
  /*
   * routine to check that the specified directory is empty (for rmdir)
   */

  int ufs_empty_dir(struct inode * inode)

  {

  	struct super_block *sb = inode->i_sb;
  	struct page *page = NULL;
  	unsigned long i, npages = ufs_dir_pages(inode);
  
  	for (i = 0; i < npages; i++) {
  		char *kaddr;
  		struct ufs_dir_entry *de;
  		page = ufs_get_page(inode, i);
  
  		if (IS_ERR(page))
  			continue;
  
  		kaddr = page_address(page);
  		de = (struct ufs_dir_entry *)kaddr;
  		kaddr += ufs_last_byte(inode, i) - UFS_DIR_REC_LEN(1);
  
  		while ((char *)de <= kaddr) {
  			if (de->d_reclen == 0) {

  				ufs_error(inode->i_sb, __func__,

  					"zero-length directory entry: "
  					"kaddr=%p, de=%p
  ", kaddr, de);
  				goto not_empty;

  			}

  			if (de->d_ino) {
  				u16 namelen=ufs_get_de_namlen(sb, de);
  				/* check for . and .. */
  				if (de->d_name[0] != '.')
  					goto not_empty;
  				if (namelen > 2)
  					goto not_empty;
  				if (namelen < 2) {
  					if (inode->i_ino !=
  					    fs32_to_cpu(sb, de->d_ino))
  						goto not_empty;
  				} else if (de->d_name[1] != '.')
  					goto not_empty;
  			}
  			de = ufs_next_entry(sb, de);

  		}

  		ufs_put_page(page);

  	}

  	return 1;

  
  not_empty:
  	ufs_put_page(page);
  	return 0;

  }

  const struct file_operations ufs_dir_operations = {

  	.read		= generic_read_dir,
  	.readdir	= ufs_readdir,

  	.fsync		= generic_file_fsync,

  	.llseek		= generic_file_llseek,

  };