/*

   *  linux/fs/ext4/dir.c

   *
   * Copyright (C) 1992, 1993, 1994, 1995
   * Remy Card (card@masi.ibp.fr)
   * Laboratoire MASI - Institut Blaise Pascal
   * Universite Pierre et Marie Curie (Paris VI)
   *
   *  from
   *
   *  linux/fs/minix/dir.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *

   *  ext4 directory handling functions

   *
   *  Big-endian to little-endian byte-swapping/bitmaps by
   *        David S. Miller (davem@caip.rutgers.edu), 1995
   *
   * Hash Tree Directory indexing (c) 2001  Daniel Phillips
   *
   */
  
  #include <linux/fs.h>

  #include <linux/jbd2.h>

  #include <linux/buffer_head.h>

  #include <linux/slab.h>
  #include <linux/rbtree.h>

  #include "ext4.h"

  static unsigned char ext4_filetype_table[] = {

  	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
  };

  static int ext4_readdir(struct file *, void *, filldir_t);

  static int ext4_dx_readdir(struct file *filp,
  			   void *dirent, filldir_t filldir);
  static int ext4_release_dir(struct inode *inode,
  				struct file *filp);

  const struct file_operations ext4_dir_operations = {

  	.llseek		= ext4_llseek,

  	.read		= generic_read_dir,

  	.readdir	= ext4_readdir,		/* we take BKL. needed?*/

  	.unlocked_ioctl = ext4_ioctl,

  #ifdef CONFIG_COMPAT

  	.compat_ioctl	= ext4_compat_ioctl,

  #endif

  	.fsync		= ext4_sync_file,

  	.release	= ext4_release_dir,

  };
  
  
  static unsigned char get_dtype(struct super_block *sb, int filetype)
  {

  	if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE) ||
  	    (filetype >= EXT4_FT_MAX))

  		return DT_UNKNOWN;

  	return (ext4_filetype_table[filetype]);

  }

  /*
   * Return 0 if the directory entry is OK, and 1 if there is a problem
   *
   * Note: this is the opposite of what ext2 and ext3 historically returned...
   */

  int __ext4_check_dir_entry(const char *function, unsigned int line,

  			   struct inode *dir, struct file *filp,

  			   struct ext4_dir_entry_2 *de,
  			   struct buffer_head *bh,
  			   unsigned int offset)

  {

  	const char *error_msg = NULL;

  	const int rlen = ext4_rec_len_from_disk(de->rec_len,
  						dir->i_sb->s_blocksize);

  	if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))

  		error_msg = "rec_len is smaller than minimal";

  	else if (unlikely(rlen % 4 != 0))

  		error_msg = "rec_len % 4 != 0";

  	else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))

  		error_msg = "rec_len is too small for name_len";

  	else if (unlikely(((char *) de - bh->b_data) + rlen >
  			  dir->i_sb->s_blocksize))

  		error_msg = "directory entry across blocks";

  	else if (unlikely(le32_to_cpu(de->inode) >
  			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))

  		error_msg = "inode out of bounds";

  	else
  		return 0;

  	if (filp)
  		ext4_error_file(filp, function, line, bh ? bh->b_blocknr : 0,
  				"bad entry in directory: %s - offset=%u(%u), "
  				"inode=%u, rec_len=%d, name_len=%d",
  				error_msg, (unsigned) (offset%bh->b_size),
  				offset, le32_to_cpu(de->inode),
  				rlen, de->name_len);
  	else
  		ext4_error_inode(dir, function, line, bh ? bh->b_blocknr : 0,
  				"bad entry in directory: %s - offset=%u(%u), "
  				"inode=%u, rec_len=%d, name_len=%d",
  				error_msg, (unsigned) (offset%bh->b_size),
  				offset, le32_to_cpu(de->inode),
  				rlen, de->name_len);

  	return 1;

  }

  static int ext4_readdir(struct file *filp,
  			 void *dirent, filldir_t filldir)

  {
  	int error = 0;

  	unsigned int offset;

  	int i, stored;

  	struct ext4_dir_entry_2 *de;

  	struct super_block *sb;
  	int err;

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

  	int ret = 0;

  	int dir_has_error = 0;

  
  	sb = inode->i_sb;

  	if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
  				    EXT4_FEATURE_COMPAT_DIR_INDEX) &&

  	    ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||

  	     ((inode->i_size >> sb->s_blocksize_bits) == 1))) {

  		err = ext4_dx_readdir(filp, dirent, filldir);

  		if (err != ERR_BAD_DX_DIR) {
  			ret = err;
  			goto out;
  		}
  		/*
  		 * We don't set the inode dirty flag since it's not
  		 * critical that it get flushed back to the disk.
  		 */

  		ext4_clear_inode_flag(filp->f_path.dentry->d_inode,
  				      EXT4_INODE_INDEX);

  	}

  	stored = 0;
  	offset = filp->f_pos & (sb->s_blocksize - 1);
  
  	while (!error && !stored && filp->f_pos < inode->i_size) {

  		struct ext4_map_blocks map;

  		struct buffer_head *bh = NULL;

  		map.m_lblk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
  		map.m_len = 1;
  		err = ext4_map_blocks(NULL, inode, &map, 0);

  		if (err > 0) {

  			pgoff_t index = map.m_pblk >>

  					(PAGE_CACHE_SHIFT - inode->i_blkbits);
  			if (!ra_has_index(&filp->f_ra, index))

  				page_cache_sync_readahead(

  					sb->s_bdev->bd_inode->i_mapping,
  					&filp->f_ra, filp,

  					index, 1);

  			filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;

  			bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);

  		}
  
  		/*
  		 * We ignore I/O errors on directories so users have a chance
  		 * of recovering data when there's a bad sector
  		 */
  		if (!bh) {

  			if (!dir_has_error) {

  				EXT4_ERROR_FILE(filp, 0,
  						"directory contains a "
  						"hole at offset %llu",

  					   (unsigned long long) filp->f_pos);
  				dir_has_error = 1;
  			}

  			/* corrupt size?  Maybe no more blocks to read */
  			if (filp->f_pos > inode->i_blocks << 9)
  				break;

  			filp->f_pos += sb->s_blocksize - offset;
  			continue;
  		}
  
  revalidate:
  		/* If the dir block has changed since the last call to
  		 * readdir(2), then we might be pointing to an invalid
  		 * dirent right now.  Scan from the start of the block
  		 * to make sure. */
  		if (filp->f_version != inode->i_version) {
  			for (i = 0; i < sb->s_blocksize && i < offset; ) {

  				de = (struct ext4_dir_entry_2 *)

  					(bh->b_data + i);
  				/* It's too expensive to do a full
  				 * dirent test each time round this
  				 * loop, but we do have to test at
  				 * least that it is non-zero.  A
  				 * failure will be detected in the
  				 * dirent test below. */

  				if (ext4_rec_len_from_disk(de->rec_len,
  					sb->s_blocksize) < EXT4_DIR_REC_LEN(1))

  					break;

  				i += ext4_rec_len_from_disk(de->rec_len,
  							    sb->s_blocksize);

  			}
  			offset = i;
  			filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
  				| offset;
  			filp->f_version = inode->i_version;
  		}
  
  		while (!error && filp->f_pos < inode->i_size
  		       && offset < sb->s_blocksize) {

  			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);

  			if (ext4_check_dir_entry(inode, filp, de,

  						 bh, offset)) {

  				/*
  				 * On error, skip the f_pos to the next block
  				 */

  				filp->f_pos = (filp->f_pos |
  						(sb->s_blocksize - 1)) + 1;

  				brelse(bh);

  				ret = stored;
  				goto out;
  			}

  			offset += ext4_rec_len_from_disk(de->rec_len,
  					sb->s_blocksize);

  			if (le32_to_cpu(de->inode)) {
  				/* We might block in the next section
  				 * if the data destination is
  				 * currently swapped out.  So, use a
  				 * version stamp to detect whether or
  				 * not the directory has been modified
  				 * during the copy operation.
  				 */

  				u64 version = filp->f_version;

  
  				error = filldir(dirent, de->name,
  						de->name_len,
  						filp->f_pos,
  						le32_to_cpu(de->inode),
  						get_dtype(sb, de->file_type));
  				if (error)
  					break;
  				if (version != filp->f_version)
  					goto revalidate;

  				stored++;

  			}

  			filp->f_pos += ext4_rec_len_from_disk(de->rec_len,
  						sb->s_blocksize);

  		}
  		offset = 0;

  		brelse(bh);

  	}
  out:
  	return ret;
  }

  /*
   * These functions convert from the major/minor hash to an f_pos
   * value.
   *
   * Currently we only use major hash numer.  This is unfortunate, but
   * on 32-bit machines, the same VFS interface is used for lseek and
   * llseek, so if we use the 64 bit offset, then the 32-bit versions of
   * lseek/telldir/seekdir will blow out spectacularly, and from within
   * the ext2 low-level routine, we don't know if we're being called by
   * a 64-bit version of the system call or the 32-bit version of the
   * system call.  Worse yet, NFSv2 only allows for a 32-bit readdir
   * cookie.  Sigh.
   */
  #define hash2pos(major, minor)	(major >> 1)
  #define pos2maj_hash(pos)	((pos << 1) & 0xffffffff)
  #define pos2min_hash(pos)	(0)
  
  /*
   * This structure holds the nodes of the red-black tree used to store
   * the directory entry in hash order.
   */
  struct fname {
  	__u32		hash;
  	__u32		minor_hash;
  	struct rb_node	rb_hash;
  	struct fname	*next;
  	__u32		inode;
  	__u8		name_len;
  	__u8		file_type;
  	char		name[0];
  };
  
  /*
   * This functoin implements a non-recursive way of freeing all of the
   * nodes in the red-black tree.
   */
  static void free_rb_tree_fname(struct rb_root *root)
  {
  	struct rb_node	*n = root->rb_node;
  	struct rb_node	*parent;
  	struct fname	*fname;
  
  	while (n) {
  		/* Do the node's children first */

  		if (n->rb_left) {

  			n = n->rb_left;
  			continue;
  		}
  		if (n->rb_right) {
  			n = n->rb_right;
  			continue;
  		}
  		/*
  		 * The node has no children; free it, and then zero
  		 * out parent's link to it.  Finally go to the
  		 * beginning of the loop and try to free the parent
  		 * node.
  		 */
  		parent = rb_parent(n);
  		fname = rb_entry(n, struct fname, rb_hash);
  		while (fname) {

  			struct fname *old = fname;

  			fname = fname->next;

  			kfree(old);

  		}
  		if (!parent)

  			*root = RB_ROOT;

  		else if (parent->rb_left == n)
  			parent->rb_left = NULL;
  		else if (parent->rb_right == n)
  			parent->rb_right = NULL;
  		n = parent;
  	}

  }

  static struct dir_private_info *ext4_htree_create_dir_info(loff_t pos)

  {
  	struct dir_private_info *p;

  	p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);

  	if (!p)
  		return NULL;

  	p->curr_hash = pos2maj_hash(pos);
  	p->curr_minor_hash = pos2min_hash(pos);

  	return p;
  }

  void ext4_htree_free_dir_info(struct dir_private_info *p)

  {
  	free_rb_tree_fname(&p->root);
  	kfree(p);
  }
  
  /*
   * Given a directory entry, enter it into the fname rb tree.
   */

  int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,

  			     __u32 minor_hash,

  			     struct ext4_dir_entry_2 *dirent)

  {
  	struct rb_node **p, *parent = NULL;

  	struct fname *fname, *new_fn;

  	struct dir_private_info *info;
  	int len;

  	info = dir_file->private_data;

  	p = &info->root.rb_node;
  
  	/* Create and allocate the fname structure */
  	len = sizeof(struct fname) + dirent->name_len + 1;
  	new_fn = kzalloc(len, GFP_KERNEL);
  	if (!new_fn)
  		return -ENOMEM;
  	new_fn->hash = hash;
  	new_fn->minor_hash = minor_hash;
  	new_fn->inode = le32_to_cpu(dirent->inode);
  	new_fn->name_len = dirent->name_len;
  	new_fn->file_type = dirent->file_type;
  	memcpy(new_fn->name, dirent->name, dirent->name_len);
  	new_fn->name[dirent->name_len] = 0;
  
  	while (*p) {
  		parent = *p;
  		fname = rb_entry(parent, struct fname, rb_hash);
  
  		/*
  		 * If the hash and minor hash match up, then we put
  		 * them on a linked list.  This rarely happens...
  		 */
  		if ((new_fn->hash == fname->hash) &&
  		    (new_fn->minor_hash == fname->minor_hash)) {
  			new_fn->next = fname->next;
  			fname->next = new_fn;
  			return 0;
  		}
  
  		if (new_fn->hash < fname->hash)
  			p = &(*p)->rb_left;
  		else if (new_fn->hash > fname->hash)
  			p = &(*p)->rb_right;
  		else if (new_fn->minor_hash < fname->minor_hash)
  			p = &(*p)->rb_left;
  		else /* if (new_fn->minor_hash > fname->minor_hash) */
  			p = &(*p)->rb_right;
  	}
  
  	rb_link_node(&new_fn->rb_hash, parent, p);
  	rb_insert_color(&new_fn->rb_hash, &info->root);
  	return 0;
  }
  
  
  
  /*

   * This is a helper function for ext4_dx_readdir.  It calls filldir

   * for all entres on the fname linked list.  (Normally there is only
   * one entry on the linked list, unless there are 62 bit hash collisions.)
   */

  static int call_filldir(struct file *filp, void *dirent,

  			filldir_t filldir, struct fname *fname)
  {
  	struct dir_private_info *info = filp->private_data;
  	loff_t	curr_pos;

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

  	struct super_block *sb;

  	int error;
  
  	sb = inode->i_sb;
  
  	if (!fname) {

  		printk(KERN_ERR "EXT4-fs: call_filldir: called with "

  		       "null fname?!?
  ");

  		return 0;
  	}
  	curr_pos = hash2pos(fname->hash, fname->minor_hash);
  	while (fname) {
  		error = filldir(dirent, fname->name,
  				fname->name_len, curr_pos,
  				fname->inode,
  				get_dtype(sb, fname->file_type));
  		if (error) {
  			filp->f_pos = curr_pos;

  			info->extra_fname = fname;

  			return error;
  		}
  		fname = fname->next;
  	}
  	return 0;
  }

  static int ext4_dx_readdir(struct file *filp,
  			 void *dirent, filldir_t filldir)

  {
  	struct dir_private_info *info = filp->private_data;

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

  	struct fname *fname;
  	int	ret;
  
  	if (!info) {

  		info = ext4_htree_create_dir_info(filp->f_pos);

  		if (!info)
  			return -ENOMEM;
  		filp->private_data = info;
  	}

  	if (filp->f_pos == EXT4_HTREE_EOF)

  		return 0;	/* EOF */
  
  	/* Some one has messed with f_pos; reset the world */
  	if (info->last_pos != filp->f_pos) {
  		free_rb_tree_fname(&info->root);
  		info->curr_node = NULL;
  		info->extra_fname = NULL;
  		info->curr_hash = pos2maj_hash(filp->f_pos);
  		info->curr_minor_hash = pos2min_hash(filp->f_pos);
  	}
  
  	/*
  	 * If there are any leftover names on the hash collision
  	 * chain, return them first.
  	 */

  	if (info->extra_fname) {
  		if (call_filldir(filp, dirent, filldir, info->extra_fname))
  			goto finished;

  		info->extra_fname = NULL;

  		goto next_node;

  	} else if (!info->curr_node)

  		info->curr_node = rb_first(&info->root);
  
  	while (1) {
  		/*
  		 * Fill the rbtree if we have no more entries,
  		 * or the inode has changed since we last read in the
  		 * cached entries.
  		 */
  		if ((!info->curr_node) ||
  		    (filp->f_version != inode->i_version)) {
  			info->curr_node = NULL;
  			free_rb_tree_fname(&info->root);
  			filp->f_version = inode->i_version;

  			ret = ext4_htree_fill_tree(filp, info->curr_hash,

  						   info->curr_minor_hash,
  						   &info->next_hash);
  			if (ret < 0)
  				return ret;
  			if (ret == 0) {

  				filp->f_pos = EXT4_HTREE_EOF;

  				break;
  			}
  			info->curr_node = rb_first(&info->root);
  		}
  
  		fname = rb_entry(info->curr_node, struct fname, rb_hash);
  		info->curr_hash = fname->hash;
  		info->curr_minor_hash = fname->minor_hash;
  		if (call_filldir(filp, dirent, filldir, fname))
  			break;

  	next_node:

  		info->curr_node = rb_next(info->curr_node);

  		if (info->curr_node) {
  			fname = rb_entry(info->curr_node, struct fname,
  					 rb_hash);
  			info->curr_hash = fname->hash;
  			info->curr_minor_hash = fname->minor_hash;
  		} else {

  			if (info->next_hash == ~0) {

  				filp->f_pos = EXT4_HTREE_EOF;

  				break;
  			}
  			info->curr_hash = info->next_hash;
  			info->curr_minor_hash = 0;
  		}
  	}
  finished:
  	info->last_pos = filp->f_pos;
  	return 0;
  }

  static int ext4_release_dir(struct inode *inode, struct file *filp)

  {

  	if (filp->private_data)

  		ext4_htree_free_dir_info(filp->private_data);

  
  	return 0;
  }