/*
   * Copyright (c) 2000-2001 Christoph Hellwig.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions, and the following disclaimer,
   *    without modification.
   * 2. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * Alternatively, this software may be distributed under the terms of the
   * GNU General Public License ("GPL").
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  /*
   * Veritas filesystem driver - lookup and other directory related code.
   */
  #include <linux/fs.h>
  #include <linux/time.h>
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/kernel.h>
  #include <linux/pagemap.h>
  
  #include "vxfs.h"
  #include "vxfs_dir.h"
  #include "vxfs_inode.h"
  #include "vxfs_extern.h"
  
  /*
   * Number of VxFS blocks per page.
   */
  #define VXFS_BLOCK_PER_PAGE(sbp)  ((PAGE_CACHE_SIZE / (sbp)->s_blocksize))
  
  
  static struct dentry *	vxfs_lookup(struct inode *, struct dentry *, unsigned int);
  static int		vxfs_readdir(struct file *, struct dir_context *);
  
  const struct inode_operations vxfs_dir_inode_ops = {
  	.lookup =		vxfs_lookup,
  };
  
  const struct file_operations vxfs_dir_operations = {
  	.llseek =		generic_file_llseek,
  	.read =			generic_read_dir,
  	.iterate =		vxfs_readdir,
  };
  
  static inline u_long
  dir_blocks(struct inode *ip)
  {
  	u_long			bsize = ip->i_sb->s_blocksize;
  	return (ip->i_size + bsize - 1) & ~(bsize - 1);
  }
  
  /*
   * NOTE! unlike strncmp, vxfs_match returns 1 for success, 0 for failure.
   *
   * len <= VXFS_NAMELEN and de != NULL are guaranteed by caller.
   */
  static inline int
  vxfs_match(int len, const char * const name, struct vxfs_direct *de)
  {
  	if (len != de->d_namelen)
  		return 0;
  	if (!de->d_ino)
  		return 0;
  	return !memcmp(name, de->d_name, len);
  }
  
  static inline struct vxfs_direct *
  vxfs_next_entry(struct vxfs_direct *de)
  {
  	return ((struct vxfs_direct *)((char*)de + de->d_reclen));
  }
  
  /**
   * vxfs_find_entry - find a mathing directory entry for a dentry
   * @ip:		directory inode
   * @dp:		dentry for which we want to find a direct
   * @ppp:	gets filled with the page the return value sits in
   *
   * Description:
   *   vxfs_find_entry finds a &struct vxfs_direct for the VFS directory
   *   cache entry @dp.  @ppp will be filled with the page the return
   *   value resides in.
   *
   * Returns:
   *   The wanted direct on success, else a NULL pointer.
   */
  static struct vxfs_direct *
  vxfs_find_entry(struct inode *ip, struct dentry *dp, struct page **ppp)
  {
  	u_long				npages, page, nblocks, pblocks, block;
  	u_long				bsize = ip->i_sb->s_blocksize;
  	const char			*name = dp->d_name.name;
  	int				namelen = dp->d_name.len;
  
  	npages = dir_pages(ip);
  	nblocks = dir_blocks(ip);
  	pblocks = VXFS_BLOCK_PER_PAGE(ip->i_sb);
  	
  	for (page = 0; page < npages; page++) {
  		caddr_t			kaddr;
  		struct page		*pp;
  
  		pp = vxfs_get_page(ip->i_mapping, page);
  		if (IS_ERR(pp))
  			continue;
  		kaddr = (caddr_t)page_address(pp);
  
  		for (block = 0; block <= nblocks && block <= pblocks; block++) {
  			caddr_t			baddr, limit;
  			struct vxfs_dirblk	*dbp;
  			struct vxfs_direct	*de;
  
  			baddr = kaddr + (block * bsize);
  			limit = baddr + bsize - VXFS_DIRLEN(1);
  			
  			dbp = (struct vxfs_dirblk *)baddr;
  			de = (struct vxfs_direct *)(baddr + VXFS_DIRBLKOV(dbp));
  
  			for (; (caddr_t)de <= limit; de = vxfs_next_entry(de)) {
  				if (!de->d_reclen)
  					break;
  				if (!de->d_ino)
  					continue;
  				if (vxfs_match(namelen, name, de)) {
  					*ppp = pp;
  					return (de);
  				}
  			}
  		}
  		vxfs_put_page(pp);
  	}
  
  	return NULL;
  }
  
  /**
   * vxfs_inode_by_name - find inode number for dentry
   * @dip:	directory to search in
   * @dp:		dentry we search for
   *
   * Description:
   *   vxfs_inode_by_name finds out the inode number of
   *   the path component described by @dp in @dip.
   *
   * Returns:
   *   The wanted inode number on success, else Zero.
   */
  static ino_t
  vxfs_inode_by_name(struct inode *dip, struct dentry *dp)
  {
  	struct vxfs_direct		*de;
  	struct page			*pp;
  	ino_t				ino = 0;
  
  	de = vxfs_find_entry(dip, dp, &pp);
  	if (de) {
  		ino = de->d_ino;
  		kunmap(pp);
  		page_cache_release(pp);
  	}
  	
  	return (ino);
  }
  
  /**
   * vxfs_lookup - lookup pathname component
   * @dip:	dir in which we lookup
   * @dp:		dentry we lookup
   * @flags:	lookup flags
   *
   * Description:
   *   vxfs_lookup tries to lookup the pathname component described
   *   by @dp in @dip.
   *
   * Returns:
   *   A NULL-pointer on success, else a negative error code encoded
   *   in the return pointer.
   */
  static struct dentry *
  vxfs_lookup(struct inode *dip, struct dentry *dp, unsigned int flags)
  {
  	struct inode		*ip = NULL;
  	ino_t			ino;
  			 
  	if (dp->d_name.len > VXFS_NAMELEN)
  		return ERR_PTR(-ENAMETOOLONG);
  				 
  	ino = vxfs_inode_by_name(dip, dp);
  	if (ino) {
  		ip = vxfs_iget(dip->i_sb, ino);
  		if (IS_ERR(ip))
  			return ERR_CAST(ip);
  	}
  	d_add(dp, ip);
  	return NULL;
  }
  
  /**
   * vxfs_readdir - read a directory
   * @fp:		the directory to read
   * @retp:	return buffer
   * @filler:	filldir callback
   *
   * Description:
   *   vxfs_readdir fills @retp with directory entries from @fp
   *   using the VFS supplied callback @filler.
   *
   * Returns:
   *   Zero.
   */
  static int
  vxfs_readdir(struct file *fp, struct dir_context *ctx)
  {
  	struct inode		*ip = file_inode(fp);
  	struct super_block	*sbp = ip->i_sb;
  	u_long			bsize = sbp->s_blocksize;
  	u_long			page, npages, block, pblocks, nblocks, offset;
  	loff_t			pos;
  
  	if (ctx->pos == 0) {
  		if (!dir_emit_dot(fp, ctx))
  			return 0;
  		ctx->pos = 1;
  	}
  	if (ctx->pos == 1) {
  		if (!dir_emit(ctx, "..", 2, VXFS_INO(ip)->vii_dotdot, DT_DIR))
  			return 0;
  		ctx->pos = 2;
  	}
  	pos = ctx->pos - 2;
  	
  	if (pos > VXFS_DIRROUND(ip->i_size))
  		return 0;
  
  	npages = dir_pages(ip);
  	nblocks = dir_blocks(ip);
  	pblocks = VXFS_BLOCK_PER_PAGE(sbp);
  
  	page = pos >> PAGE_CACHE_SHIFT;
  	offset = pos & ~PAGE_CACHE_MASK;
  	block = (u_long)(pos >> sbp->s_blocksize_bits) % pblocks;
  
  	for (; page < npages; page++, block = 0) {
  		char			*kaddr;
  		struct page		*pp;
  
  		pp = vxfs_get_page(ip->i_mapping, page);
  		if (IS_ERR(pp))
  			continue;
  		kaddr = (char *)page_address(pp);
  
  		for (; block <= nblocks && block <= pblocks; block++) {
  			char			*baddr, *limit;
  			struct vxfs_dirblk	*dbp;
  			struct vxfs_direct	*de;
  
  			baddr = kaddr + (block * bsize);
  			limit = baddr + bsize - VXFS_DIRLEN(1);
  	
  			dbp = (struct vxfs_dirblk *)baddr;
  			de = (struct vxfs_direct *)
  				(offset ?
  				 (kaddr + offset) :
  				 (baddr + VXFS_DIRBLKOV(dbp)));
  
  			for (; (char *)de <= limit; de = vxfs_next_entry(de)) {
  				if (!de->d_reclen)
  					break;
  				if (!de->d_ino)
  					continue;
  
  				offset = (char *)de - kaddr;
  				ctx->pos = ((page << PAGE_CACHE_SHIFT) | offset) + 2;
  				if (!dir_emit(ctx, de->d_name, de->d_namelen,
  					de->d_ino, DT_UNKNOWN)) {
  					vxfs_put_page(pp);
  					return 0;
  				}
  			}
  			offset = 0;
  		}
  		vxfs_put_page(pp);
  		offset = 0;
  	}
  	ctx->pos = ((page << PAGE_CACHE_SHIFT) | offset) + 2;
  	return 0;
  }