/*
   * OMFS (as used by RIO Karma) directory operations.
   * Copyright (C) 2005 Bob Copeland <me@bobcopeland.com>
   * Released under GPL v2.
   */
  
  #include <linux/fs.h>
  #include <linux/ctype.h>
  #include <linux/buffer_head.h>
  #include "omfs.h"
  
  static int omfs_hash(const char *name, int namelen, int mod)
  {
  	int i, hash = 0;
  	for (i = 0; i < namelen; i++)
  		hash ^= tolower(name[i]) << (i % 24);
  	return hash % mod;
  }
  
  /*
   * Finds the bucket for a given name and reads the containing block;
   * *ofs is set to the offset of the first list entry.
   */
  static struct buffer_head *omfs_get_bucket(struct inode *dir,
  		const char *name, int namelen, int *ofs)
  {
  	int nbuckets = (dir->i_size - OMFS_DIR_START)/8;

  	int bucket = omfs_hash(name, namelen, nbuckets);
  
  	*ofs = OMFS_DIR_START + bucket * 8;

  	return omfs_bread(dir->i_sb, dir->i_ino);

  }
  
  static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block,
  				const char *name, int namelen,
  				u64 *prev_block)
  {
  	struct buffer_head *bh;
  	struct omfs_inode *oi;
  	int err = -ENOENT;
  	*prev_block = ~0;
  
  	while (block != ~0) {

  		bh = omfs_bread(dir->i_sb, block);

  		if (!bh) {
  			err = -EIO;
  			goto err;
  		}
  
  		oi = (struct omfs_inode *) bh->b_data;
  		if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, block)) {
  			brelse(bh);
  			goto err;
  		}
  
  		if (strncmp(oi->i_name, name, namelen) == 0)
  			return bh;
  
  		*prev_block = block;
  		block = be64_to_cpu(oi->i_sibling);
  		brelse(bh);
  	}
  err:
  	return ERR_PTR(err);
  }
  
  static struct buffer_head *omfs_find_entry(struct inode *dir,
  					   const char *name, int namelen)
  {
  	struct buffer_head *bh;
  	int ofs;
  	u64 block, dummy;
  
  	bh = omfs_get_bucket(dir, name, namelen, &ofs);
  	if (!bh)
  		return ERR_PTR(-EIO);
  
  	block = be64_to_cpu(*((__be64 *) &bh->b_data[ofs]));
  	brelse(bh);
  
  	return omfs_scan_list(dir, block, name, namelen, &dummy);
  }
  
  int omfs_make_empty(struct inode *inode, struct super_block *sb)
  {
  	struct omfs_sb_info *sbi = OMFS_SB(sb);

  	struct buffer_head *bh;
  	struct omfs_inode *oi;

  	bh = omfs_bread(sb, inode->i_ino);

  	if (!bh)
  		return -ENOMEM;
  
  	memset(bh->b_data, 0, sizeof(struct omfs_inode));

  	if (S_ISDIR(inode->i_mode)) {

  		memset(&bh->b_data[OMFS_DIR_START], 0xff,
  			sbi->s_sys_blocksize - OMFS_DIR_START);
  	} else
  		omfs_make_empty_table(bh, OMFS_EXTENT_START);
  
  	oi = (struct omfs_inode *) bh->b_data;
  	oi->i_head.h_self = cpu_to_be64(inode->i_ino);

  	oi->i_sibling = ~cpu_to_be64(0ULL);

  
  	mark_buffer_dirty(bh);
  	brelse(bh);
  	return 0;
  }
  
  static int omfs_add_link(struct dentry *dentry, struct inode *inode)
  {

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

  	const char *name = dentry->d_name.name;
  	int namelen = dentry->d_name.len;
  	struct omfs_inode *oi;
  	struct buffer_head *bh;
  	u64 block;
  	__be64 *entry;
  	int ofs;
  
  	/* just prepend to head of queue in proper bucket */
  	bh = omfs_get_bucket(dir, name, namelen, &ofs);
  	if (!bh)
  		goto out;
  
  	entry = (__be64 *) &bh->b_data[ofs];
  	block = be64_to_cpu(*entry);
  	*entry = cpu_to_be64(inode->i_ino);
  	mark_buffer_dirty(bh);
  	brelse(bh);
  
  	/* now set the sibling and parent pointers on the new inode */

  	bh = omfs_bread(dir->i_sb, inode->i_ino);

  	if (!bh)
  		goto out;
  
  	oi = (struct omfs_inode *) bh->b_data;
  	memcpy(oi->i_name, name, namelen);
  	memset(oi->i_name + namelen, 0, OMFS_NAMELEN - namelen);
  	oi->i_sibling = cpu_to_be64(block);
  	oi->i_parent = cpu_to_be64(dir->i_ino);
  	mark_buffer_dirty(bh);
  	brelse(bh);
  
  	dir->i_ctime = CURRENT_TIME_SEC;
  
  	/* mark affected inodes dirty to rebuild checksums */
  	mark_inode_dirty(dir);
  	mark_inode_dirty(inode);
  	return 0;
  out:
  	return -ENOMEM;
  }
  
  static int omfs_delete_entry(struct dentry *dentry)
  {

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

  	struct inode *dirty;
  	const char *name = dentry->d_name.name;
  	int namelen = dentry->d_name.len;
  	struct omfs_inode *oi;
  	struct buffer_head *bh, *bh2;
  	__be64 *entry, next;
  	u64 block, prev;
  	int ofs;
  	int err = -ENOMEM;
  
  	/* delete the proper node in the bucket's linked list */
  	bh = omfs_get_bucket(dir, name, namelen, &ofs);
  	if (!bh)
  		goto out;
  
  	entry = (__be64 *) &bh->b_data[ofs];
  	block = be64_to_cpu(*entry);
  
  	bh2 = omfs_scan_list(dir, block, name, namelen, &prev);
  	if (IS_ERR(bh2)) {
  		err = PTR_ERR(bh2);
  		goto out_free_bh;
  	}
  
  	oi = (struct omfs_inode *) bh2->b_data;
  	next = oi->i_sibling;
  	brelse(bh2);
  
  	if (prev != ~0) {
  		/* found in middle of list, get list ptr */
  		brelse(bh);

  		bh = omfs_bread(dir->i_sb, prev);

  		if (!bh)
  			goto out;
  
  		oi = (struct omfs_inode *) bh->b_data;
  		entry = &oi->i_sibling;
  	}
  
  	*entry = next;
  	mark_buffer_dirty(bh);
  
  	if (prev != ~0) {
  		dirty = omfs_iget(dir->i_sb, prev);
  		if (!IS_ERR(dirty)) {
  			mark_inode_dirty(dirty);
  			iput(dirty);
  		}
  	}
  
  	err = 0;
  out_free_bh:
  	brelse(bh);
  out:
  	return err;
  }
  
  static int omfs_dir_is_empty(struct inode *inode)
  {
  	int nbuckets = (inode->i_size - OMFS_DIR_START) / 8;
  	struct buffer_head *bh;
  	u64 *ptr;
  	int i;

  	bh = omfs_bread(inode->i_sb, inode->i_ino);

  
  	if (!bh)
  		return 0;
  
  	ptr = (u64 *) &bh->b_data[OMFS_DIR_START];
  
  	for (i = 0; i < nbuckets; i++, ptr++)
  		if (*ptr != ~0)
  			break;
  
  	brelse(bh);
  	return *ptr != ~0;
  }

  static int omfs_remove(struct inode *dir, struct dentry *dentry)

  {

  	struct inode *inode = d_inode(dentry);

  	int ret;

  	if (S_ISDIR(inode->i_mode) &&
  	    !omfs_dir_is_empty(inode))
  		return -ENOTEMPTY;

  
  	ret = omfs_delete_entry(dentry);
  	if (ret)

  		return ret;
  	
  	clear_nlink(inode);
  	mark_inode_dirty(inode);

  	mark_inode_dirty(dir);

  	return 0;

  }

  static int omfs_add_node(struct inode *dir, struct dentry *dentry, umode_t mode)

  {
  	int err;
  	struct inode *inode = omfs_new_inode(dir, mode);
  
  	if (IS_ERR(inode))
  		return PTR_ERR(inode);
  
  	err = omfs_make_empty(inode, dir->i_sb);
  	if (err)
  		goto out_free_inode;
  
  	err = omfs_add_link(dentry, inode);
  	if (err)
  		goto out_free_inode;
  
  	d_instantiate(dentry, inode);
  	return 0;
  
  out_free_inode:
  	iput(inode);
  	return err;
  }

  static int omfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)

  {
  	return omfs_add_node(dir, dentry, mode | S_IFDIR);
  }

  static int omfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,

  		bool excl)

  {
  	return omfs_add_node(dir, dentry, mode | S_IFREG);
  }
  
  static struct dentry *omfs_lookup(struct inode *dir, struct dentry *dentry,

  				  unsigned int flags)

  {
  	struct buffer_head *bh;
  	struct inode *inode = NULL;
  
  	if (dentry->d_name.len > OMFS_NAMELEN)
  		return ERR_PTR(-ENAMETOOLONG);
  
  	bh = omfs_find_entry(dir, dentry->d_name.name, dentry->d_name.len);
  	if (!IS_ERR(bh)) {
  		struct omfs_inode *oi = (struct omfs_inode *)bh->b_data;
  		ino_t ino = be64_to_cpu(oi->i_head.h_self);
  		brelse(bh);
  		inode = omfs_iget(dir->i_sb, ino);
  		if (IS_ERR(inode))
  			return ERR_CAST(inode);
  	}
  	d_add(dentry, inode);
  	return NULL;
  }
  
  /* sanity check block's self pointer */
  int omfs_is_bad(struct omfs_sb_info *sbi, struct omfs_header *header,
  	u64 fsblock)
  {
  	int is_bad;
  	u64 ino = be64_to_cpu(header->h_self);
  	is_bad = ((ino != fsblock) || (ino < sbi->s_root_ino) ||
  		(ino > sbi->s_num_blocks));
  
  	if (is_bad)
  		printk(KERN_WARNING "omfs: bad hash chain detected
  ");
  
  	return is_bad;
  }

  static bool omfs_fill_chain(struct inode *dir, struct dir_context *ctx,

  		u64 fsblock, int hindex)
  {

  	/* follow chain in this bucket */
  	while (fsblock != ~0) {

  		struct buffer_head *bh = omfs_bread(dir->i_sb, fsblock);
  		struct omfs_inode *oi;
  		u64 self;
  		unsigned char d_type;

  		if (!bh)

  			return true;

  
  		oi = (struct omfs_inode *) bh->b_data;
  		if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, fsblock)) {
  			brelse(bh);

  			return true;

  		}
  
  		self = fsblock;
  		fsblock = be64_to_cpu(oi->i_sibling);
  
  		/* skip visited nodes */
  		if (hindex) {
  			hindex--;
  			brelse(bh);
  			continue;
  		}
  
  		d_type = (oi->i_type == OMFS_DIR) ? DT_DIR : DT_REG;

  		if (!dir_emit(ctx, oi->i_name,
  			      strnlen(oi->i_name, OMFS_NAMELEN),
  			      self, d_type)) {
  			brelse(bh);
  			return false;
  		}

  		brelse(bh);

  		ctx->pos++;

  	}

  	return true;

  }
  
  static int omfs_rename(struct inode *old_dir, struct dentry *old_dentry,
  		struct inode *new_dir, struct dentry *new_dentry)
  {

  	struct inode *new_inode = d_inode(new_dentry);
  	struct inode *old_inode = d_inode(old_dentry);

  	int err;

  	if (new_inode) {
  		/* overwriting existing file/dir */

  		err = omfs_remove(new_dir, new_dentry);

  		if (err)
  			goto out;
  	}
  
  	/* since omfs locates files by name, we need to unlink _before_
  	 * adding the new link or we won't find the old one */

  	err = omfs_delete_entry(old_dentry);
  	if (err)

  		goto out;

  	mark_inode_dirty(old_dir);

  	err = omfs_add_link(new_dentry, old_inode);
  	if (err)
  		goto out;
  
  	old_inode->i_ctime = CURRENT_TIME_SEC;

  	mark_inode_dirty(old_inode);

  out:
  	return err;
  }

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

  {

  	struct inode *dir = file_inode(file);

  	struct buffer_head *bh;

  	__be64 *p;

  	unsigned int hchain, hindex;
  	int nbuckets;

  
  	if (ctx->pos >> 32)
  		return -EINVAL;
  
  	if (ctx->pos < 1 << 20) {
  		if (!dir_emit_dots(file, ctx))
  			return 0;
  		ctx->pos = 1 << 20;

  	}
  
  	nbuckets = (dir->i_size - OMFS_DIR_START) / 8;
  
  	/* high 12 bits store bucket + 1 and low 20 bits store hash index */

  	hchain = (ctx->pos >> 20) - 1;
  	hindex = ctx->pos & 0xfffff;

  	bh = omfs_bread(dir->i_sb, dir->i_ino);

  	if (!bh)

  		return -EINVAL;

  	p = (__be64 *)(bh->b_data + OMFS_DIR_START) + hchain;

  	for (; hchain < nbuckets; hchain++) {
  		__u64 fsblock = be64_to_cpu(*p++);
  		if (!omfs_fill_chain(dir, ctx, fsblock, hindex))

  			break;

  		hindex = 0;
  		ctx->pos = (hchain+2) << 20;

  	}
  	brelse(bh);

  	return 0;

  }

  const struct inode_operations omfs_dir_inops = {

  	.lookup = omfs_lookup,
  	.mkdir = omfs_mkdir,
  	.rename = omfs_rename,
  	.create = omfs_create,

  	.unlink = omfs_remove,
  	.rmdir = omfs_remove,

  };

  const struct file_operations omfs_dir_operations = {

  	.read = generic_read_dir,

  	.iterate = omfs_readdir,

  	.llseek = generic_file_llseek,

  };