text: /*
   *  linux/fs/isofs/namei.c
   *
   *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
   *
   *  (C) 1991  Linus Torvalds - minix filesystem
   */
  
  #include <linux/gfp.h>
  #include "isofs.h"
  
  /*
   * ok, we cannot use strncmp, as the name is not in our data space.
   * Thus we'll have to use isofs_match. No big problem. Match also makes
   * some sanity tests.
   */
  static int
  isofs_cmp(struct dentry *dentry, const char *compare, int dlen)
  {
  	struct qstr qstr;
  
  	if (!compare)
  		return 1;
  
  	/* check special "." and ".." files */
  	if (dlen == 1) {
  		/* "." */
  		if (compare[0] == 0) {
  			if (!dentry->d_name.len)
  				return 0;
  			compare = ".";
  		} else if (compare[0] == 1) {
  			compare = "..";
  			dlen = 2;
  		}
  	}
  
  	qstr.name = compare;
  	qstr.len = dlen;
  	return dentry->d_op->d_compare(NULL, NULL, NULL, NULL,
  			dentry->d_name.len, dentry->d_name.name, &qstr);
  }
  
  /*
   *	isofs_find_entry()
   *
   * finds an entry in the specified directory with the wanted name. It
   * returns the inode number of the found entry, or 0 on error.
   */
  static unsigned long
  isofs_find_entry(struct inode *dir, struct dentry *dentry,
  	unsigned long *block_rv, unsigned long *offset_rv,
  	char *tmpname, struct iso_directory_record *tmpde)
  {
  	unsigned long bufsize = ISOFS_BUFFER_SIZE(dir);
  	unsigned char bufbits = ISOFS_BUFFER_BITS(dir);
  	unsigned long block, f_pos, offset, block_saved, offset_saved;
  	struct buffer_head *bh = NULL;
  	struct isofs_sb_info *sbi = ISOFS_SB(dir->i_sb);
  
  	if (!ISOFS_I(dir)->i_first_extent)
  		return 0;
  
  	f_pos = 0;
  	offset = 0;
  	block = 0;
  
  	while (f_pos < dir->i_size) {
  		struct iso_directory_record *de;
  		int de_len, match, i, dlen;
  		char *dpnt;
  
  		if (!bh) {
  			bh = isofs_bread(dir, block);
  			if (!bh)
  				return 0;
  		}
  
  		de = (struct iso_directory_record *) (bh->b_data + offset);
  
  		de_len = *(unsigned char *) de;
  		if (!de_len) {
  			brelse(bh);
  			bh = NULL;
  			f_pos = (f_pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
  			block = f_pos >> bufbits;
  			offset = 0;
  			continue;
  		}
  
  		block_saved = bh->b_blocknr;
  		offset_saved = offset;
  		offset += de_len;
  		f_pos += de_len;
  
  		/* Make sure we have a full directory entry */
  		if (offset >= bufsize) {
  			int slop = bufsize - offset + de_len;
  			memcpy(tmpde, de, slop);
  			offset &= bufsize - 1;
  			block++;
  			brelse(bh);
  			bh = NULL;
  			if (offset) {
  				bh = isofs_bread(dir, block);
  				if (!bh)
  					return 0;
  				memcpy((void *) tmpde + slop, bh->b_data, offset);
  			}
  			de = tmpde;
  		}
  
  		dlen = de->name_len[0];
  		dpnt = de->name;
  		/* Basic sanity check, whether name doesn't exceed dir entry */
  		if (de_len < dlen + sizeof(struct iso_directory_record)) {
  			printk(KERN_NOTICE "iso9660: Corrupted directory entry"
  			       " in block %lu of inode %lu\n", block,
  			       dir->i_ino);
  			return 0;
  		}
  
  		if (sbi->s_rock &&
  		    ((i = get_rock_ridge_filename(de, tmpname, dir)))) {
  			dlen = i;	/* possibly -1 */
  			dpnt = tmpname;
  #ifdef CONFIG_JOLIET
  		} else if (sbi->s_joliet_level) {
  			dlen = get_joliet_filename(de, tmpname, dir);
  			dpnt = tmpname;
  #endif
  		} else if (sbi->s_mapping == 'a') {
  			dlen = get_acorn_filename(de, tmpname, dir);
  			dpnt = tmpname;
  		} else if (sbi->s_mapping == 'n') {
  			dlen = isofs_name_translate(de, tmpname, dir);
  			dpnt = tmpname;
  		}
  
  		/*
  		 * Skip hidden or associated files unless hide or showassoc,
  		 * respectively, is set
  		 */
  		match = 0;
  		if (dlen > 0 &&
  			(!sbi->s_hide ||
  				(!(de->flags[-sbi->s_high_sierra] & 1))) &&
  			(sbi->s_showassoc ||
  				(!(de->flags[-sbi->s_high_sierra] & 4)))) {
  			match = (isofs_cmp(dentry, dpnt, dlen) == 0);
  		}
  		if (match) {
  			isofs_normalize_block_and_offset(de,
  							 &block_saved,
  							 &offset_saved);
  			*block_rv = block_saved;
  			*offset_rv = offset_saved;
  			brelse(bh);
  			return 1;
  		}
  	}
  	brelse(bh);
  	return 0;
  }
  
  struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
  {
  	int found;
  	unsigned long uninitialized_var(block);
  	unsigned long uninitialized_var(offset);
  	struct inode *inode;
  	struct page *page;
  
  	page = alloc_page(GFP_USER);
  	if (!page)
  		return ERR_PTR(-ENOMEM);
  
  	found = isofs_find_entry(dir, dentry,
  				&block, &offset,
  				page_address(page),
  				1024 + page_address(page));
  	__free_page(page);
  
  	inode = found ? isofs_iget(dir->i_sb, block, offset) : NULL;
  
  	return d_splice_alias(inode, dentry);
  }
  