text: // SPDX-License-Identifier: GPL-2.0-or-later
  /**
   * dir.c - NTFS kernel directory operations. Part of the Linux-NTFS project.
   *
   * Copyright (c) 2001-2007 Anton Altaparmakov
   * Copyright (c) 2002 Richard Russon
   */
  
  #include <linux/buffer_head.h>
  #include <linux/slab.h>
  #include <linux/blkdev.h>
  
  #include "dir.h"
  #include "aops.h"
  #include "attrib.h"
  #include "mft.h"
  #include "debug.h"
  #include "ntfs.h"
  
  /**
   * The little endian Unicode string $I30 as a global constant.
   */
  ntfschar I30[5] = { cpu_to_le16('$'), cpu_to_le16('I'),
  		cpu_to_le16('3'),	cpu_to_le16('0'), 0 };
  
  /**
   * ntfs_lookup_inode_by_name - find an inode in a directory given its name
   * @dir_ni:	ntfs inode of the directory in which to search for the name
   * @uname:	Unicode name for which to search in the directory
   * @uname_len:	length of the name @uname in Unicode characters
   * @res:	return the found file name if necessary (see below)
   *
   * Look for an inode with name @uname in the directory with inode @dir_ni.
   * ntfs_lookup_inode_by_name() walks the contents of the directory looking for
   * the Unicode name. If the name is found in the directory, the corresponding
   * inode number (>= 0) is returned as a mft reference in cpu format, i.e. it
   * is a 64-bit number containing the sequence number.
   *
   * On error, a negative value is returned corresponding to the error code. In
   * particular if the inode is not found -ENOENT is returned. Note that you
   * can't just check the return value for being negative, you have to check the
   * inode number for being negative which you can extract using MREC(return
   * value).
   *
   * Note, @uname_len does not include the (optional) terminating NULL character.
   *
   * Note, we look for a case sensitive match first but we also look for a case
   * insensitive match at the same time. If we find a case insensitive match, we
   * save that for the case that we don't find an exact match, where we return
   * the case insensitive match and setup @res (which we allocate!) with the mft
   * reference, the file name type, length and with a copy of the little endian
   * Unicode file name itself. If we match a file name which is in the DOS name
   * space, we only return the mft reference and file name type in @res.
   * ntfs_lookup() then uses this to find the long file name in the inode itself.
   * This is to avoid polluting the dcache with short file names. We want them to
   * work but we don't care for how quickly one can access them. This also fixes
   * the dcache aliasing issues.
   *
   * Locking:  - Caller must hold i_mutex on the directory.
   *	     - Each page cache page in the index allocation mapping must be
   *	       locked whilst being accessed otherwise we may find a corrupt
   *	       page due to it being under ->writepage at the moment which
   *	       applies the mst protection fixups before writing out and then
   *	       removes them again after the write is complete after which it 
   *	       unlocks the page.
   */
  MFT_REF ntfs_lookup_inode_by_name(ntfs_inode *dir_ni, const ntfschar *uname,
  		const int uname_len, ntfs_name **res)
  {
  	ntfs_volume *vol = dir_ni->vol;
  	struct super_block *sb = vol->sb;
  	MFT_RECORD *m;
  	INDEX_ROOT *ir;
  	INDEX_ENTRY *ie;
  	INDEX_ALLOCATION *ia;
  	u8 *index_end;
  	u64 mref;
  	ntfs_attr_search_ctx *ctx;
  	int err, rc;
  	VCN vcn, old_vcn;
  	struct address_space *ia_mapping;
  	struct page *page;
  	u8 *kaddr;
  	ntfs_name *name = NULL;
  
  	BUG_ON(!S_ISDIR(VFS_I(dir_ni)->i_mode));
  	BUG_ON(NInoAttr(dir_ni));
  	/* Get hold of the mft record for the directory. */
  	m = map_mft_record(dir_ni);
  	if (IS_ERR(m)) {
  		ntfs_error(sb, "map_mft_record() failed with error code %ld.",
  				-PTR_ERR(m));
  		return ERR_MREF(PTR_ERR(m));
  	}
  	ctx = ntfs_attr_get_search_ctx(dir_ni, m);
  	if (unlikely(!ctx)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	/* Find the index root attribute in the mft record. */
  	err = ntfs_attr_lookup(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0, NULL,
  			0, ctx);
  	if (unlikely(err)) {
  		if (err == -ENOENT) {
  			ntfs_error(sb, "Index root attribute missing in "
  					"directory inode 0x%lx.",
  					dir_ni->mft_no);
  			err = -EIO;
  		}
  		goto err_out;
  	}
  	/* Get to the index root value (it's been verified in read_inode). */
  	ir = (INDEX_ROOT*)((u8*)ctx->attr +
  			le16_to_cpu(ctx->attr->data.resident.value_offset));
  	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
  	/* The first index entry. */
  	ie = (INDEX_ENTRY*)((u8*)&ir->index +
  			le32_to_cpu(ir->index.entries_offset));
  	/*
  	 * Loop until we exceed valid memory (corruption case) or until we
  	 * reach the last entry.
  	 */
  	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
  		/* Bounds checks. */
  		if ((u8*)ie < (u8*)ctx->mrec || (u8*)ie +
  				sizeof(INDEX_ENTRY_HEADER) > index_end ||
  				(u8*)ie + le16_to_cpu(ie->key_length) >
  				index_end)
  			goto dir_err_out;
  		/*
  		 * The last entry cannot contain a name. It can however contain
  		 * a pointer to a child node in the B+tree so we just break out.
  		 */
  		if (ie->flags & INDEX_ENTRY_END)
  			break;
  		/*
  		 * We perform a case sensitive comparison and if that matches
  		 * we are done and return the mft reference of the inode (i.e.
  		 * the inode number together with the sequence number for
  		 * consistency checking). We convert it to cpu format before
  		 * returning.
  		 */
  		if (ntfs_are_names_equal(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length,
  				CASE_SENSITIVE, vol->upcase, vol->upcase_len)) {
  found_it:
  			/*
  			 * We have a perfect match, so we don't need to care
  			 * about having matched imperfectly before, so we can
  			 * free name and set *res to NULL.
  			 * However, if the perfect match is a short file name,
  			 * we need to signal this through *res, so that
  			 * ntfs_lookup() can fix dcache aliasing issues.
  			 * As an optimization we just reuse an existing
  			 * allocation of *res.
  			 */
  			if (ie->key.file_name.file_name_type == FILE_NAME_DOS) {
  				if (!name) {
  					name = kmalloc(sizeof(ntfs_name),
  							GFP_NOFS);
  					if (!name) {
  						err = -ENOMEM;
  						goto err_out;
  					}
  				}
  				name->mref = le64_to_cpu(
  						ie->data.dir.indexed_file);
  				name->type = FILE_NAME_DOS;
  				name->len = 0;
  				*res = name;
  			} else {
  				kfree(name);
  				*res = NULL;
  			}
  			mref = le64_to_cpu(ie->data.dir.indexed_file);
  			ntfs_attr_put_search_ctx(ctx);
  			unmap_mft_record(dir_ni);
  			return mref;
  		}
  		/*
  		 * For a case insensitive mount, we also perform a case
  		 * insensitive comparison (provided the file name is not in the
  		 * POSIX namespace). If the comparison matches, and the name is
  		 * in the WIN32 namespace, we cache the filename in *res so
  		 * that the caller, ntfs_lookup(), can work on it. If the
  		 * comparison matches, and the name is in the DOS namespace, we
  		 * only cache the mft reference and the file name type (we set
  		 * the name length to zero for simplicity).
  		 */
  		if (!NVolCaseSensitive(vol) &&
  				ie->key.file_name.file_name_type &&
  				ntfs_are_names_equal(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length,
  				IGNORE_CASE, vol->upcase, vol->upcase_len)) {
  			int name_size = sizeof(ntfs_name);
  			u8 type = ie->key.file_name.file_name_type;
  			u8 len = ie->key.file_name.file_name_length;
  
  			/* Only one case insensitive matching name allowed. */
  			if (name) {
  				ntfs_error(sb, "Found already allocated name "
  						"in phase 1. Please run chkdsk "
  						"and if that doesn't find any "
  						"errors please report you saw "
  						"this message to "
  						"linux-ntfs-dev@lists."
  						"sourceforge.net.");
  				goto dir_err_out;
  			}
  
  			if (type != FILE_NAME_DOS)
  				name_size += len * sizeof(ntfschar);
  			name = kmalloc(name_size, GFP_NOFS);
  			if (!name) {
  				err = -ENOMEM;
  				goto err_out;
  			}
  			name->mref = le64_to_cpu(ie->data.dir.indexed_file);
  			name->type = type;
  			if (type != FILE_NAME_DOS) {
  				name->len = len;
  				memcpy(name->name, ie->key.file_name.file_name,
  						len * sizeof(ntfschar));
  			} else
  				name->len = 0;
  			*res = name;
  		}
  		/*
  		 * Not a perfect match, need to do full blown collation so we
  		 * know which way in the B+tree we have to go.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				IGNORE_CASE, vol->upcase, vol->upcase_len);
  		/*
  		 * If uname collates before the name of the current entry, there
  		 * is definitely no such name in this index but we might need to
  		 * descend into the B+tree so we just break out of the loop.
  		 */
  		if (rc == -1)
  			break;
  		/* The names are not equal, continue the search. */
  		if (rc)
  			continue;
  		/*
  		 * Names match with case insensitive comparison, now try the
  		 * case sensitive comparison, which is required for proper
  		 * collation.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				CASE_SENSITIVE, vol->upcase, vol->upcase_len);
  		if (rc == -1)
  			break;
  		if (rc)
  			continue;
  		/*
  		 * Perfect match, this will never happen as the
  		 * ntfs_are_names_equal() call will have gotten a match but we
  		 * still treat it correctly.
  		 */
  		goto found_it;
  	}
  	/*
  	 * We have finished with this index without success. Check for the
  	 * presence of a child node and if not present return -ENOENT, unless
  	 * we have got a matching name cached in name in which case return the
  	 * mft reference associated with it.
  	 */
  	if (!(ie->flags & INDEX_ENTRY_NODE)) {
  		if (name) {
  			ntfs_attr_put_search_ctx(ctx);
  			unmap_mft_record(dir_ni);
  			return name->mref;
  		}
  		ntfs_debug("Entry not found.");
  		err = -ENOENT;
  		goto err_out;
  	} /* Child node present, descend into it. */
  	/* Consistency check: Verify that an index allocation exists. */
  	if (!NInoIndexAllocPresent(dir_ni)) {
  		ntfs_error(sb, "No index allocation attribute but index entry "
  				"requires one. Directory inode 0x%lx is "
  				"corrupt or driver bug.", dir_ni->mft_no);
  		goto err_out;
  	}
  	/* Get the starting vcn of the index_block holding the child node. */
  	vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
  	ia_mapping = VFS_I(dir_ni)->i_mapping;
  	/*
  	 * We are done with the index root and the mft record. Release them,
  	 * otherwise we deadlock with ntfs_map_page().
  	 */
  	ntfs_attr_put_search_ctx(ctx);
  	unmap_mft_record(dir_ni);
  	m = NULL;
  	ctx = NULL;
  descend_into_child_node:
  	/*
  	 * Convert vcn to index into the index allocation attribute in units
  	 * of PAGE_SIZE and map the page cache page, reading it from
  	 * disk if necessary.
  	 */
  	page = ntfs_map_page(ia_mapping, vcn <<
  			dir_ni->itype.index.vcn_size_bits >> PAGE_SHIFT);
  	if (IS_ERR(page)) {
  		ntfs_error(sb, "Failed to map directory index page, error %ld.",
  				-PTR_ERR(page));
  		err = PTR_ERR(page);
  		goto err_out;
  	}
  	lock_page(page);
  	kaddr = (u8*)page_address(page);
  fast_descend_into_child_node:
  	/* Get to the index allocation block. */
  	ia = (INDEX_ALLOCATION*)(kaddr + ((vcn <<
  			dir_ni->itype.index.vcn_size_bits) & ~PAGE_MASK));
  	/* Bounds checks. */
  	if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_SIZE) {
  		ntfs_error(sb, "Out of bounds check failed. Corrupt directory "
  				"inode 0x%lx or driver bug.", dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	/* Catch multi sector transfer fixup errors. */
  	if (unlikely(!ntfs_is_indx_record(ia->magic))) {
  		ntfs_error(sb, "Directory index record with vcn 0x%llx is "
  				"corrupt.  Corrupt inode 0x%lx.  Run chkdsk.",
  				(unsigned long long)vcn, dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
  		ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
  				"different from expected VCN (0x%llx). "
  				"Directory inode 0x%lx is corrupt or driver "
  				"bug.", (unsigned long long)
  				sle64_to_cpu(ia->index_block_vcn),
  				(unsigned long long)vcn, dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	if (le32_to_cpu(ia->index.allocated_size) + 0x18 !=
  			dir_ni->itype.index.block_size) {
  		ntfs_error(sb, "Index buffer (VCN 0x%llx) of directory inode "
  				"0x%lx has a size (%u) differing from the "
  				"directory specified size (%u). Directory "
  				"inode is corrupt or driver bug.",
  				(unsigned long long)vcn, dir_ni->mft_no,
  				le32_to_cpu(ia->index.allocated_size) + 0x18,
  				dir_ni->itype.index.block_size);
  		goto unm_err_out;
  	}
  	index_end = (u8*)ia + dir_ni->itype.index.block_size;
  	if (index_end > kaddr + PAGE_SIZE) {
  		ntfs_error(sb, "Index buffer (VCN 0x%llx) of directory inode "
  				"0x%lx crosses page boundary. Impossible! "
  				"Cannot access! This is probably a bug in the "
  				"driver.", (unsigned long long)vcn,
  				dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
  	if (index_end > (u8*)ia + dir_ni->itype.index.block_size) {
  		ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of directory "
  				"inode 0x%lx exceeds maximum size.",
  				(unsigned long long)vcn, dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	/* The first index entry. */
  	ie = (INDEX_ENTRY*)((u8*)&ia->index +
  			le32_to_cpu(ia->index.entries_offset));
  	/*
  	 * Iterate similar to above big loop but applied to index buffer, thus
  	 * loop until we exceed valid memory (corruption case) or until we
  	 * reach the last entry.
  	 */
  	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
  		/* Bounds check. */
  		if ((u8*)ie < (u8*)ia || (u8*)ie +
  				sizeof(INDEX_ENTRY_HEADER) > index_end ||
  				(u8*)ie + le16_to_cpu(ie->key_length) >
  				index_end) {
  			ntfs_error(sb, "Index entry out of bounds in "
  					"directory inode 0x%lx.",
  					dir_ni->mft_no);
  			goto unm_err_out;
  		}
  		/*
  		 * The last entry cannot contain a name. It can however contain
  		 * a pointer to a child node in the B+tree so we just break out.
  		 */
  		if (ie->flags & INDEX_ENTRY_END)
  			break;
  		/*
  		 * We perform a case sensitive comparison and if that matches
  		 * we are done and return the mft reference of the inode (i.e.
  		 * the inode number together with the sequence number for
  		 * consistency checking). We convert it to cpu format before
  		 * returning.
  		 */
  		if (ntfs_are_names_equal(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length,
  				CASE_SENSITIVE, vol->upcase, vol->upcase_len)) {
  found_it2:
  			/*
  			 * We have a perfect match, so we don't need to care
  			 * about having matched imperfectly before, so we can
  			 * free name and set *res to NULL.
  			 * However, if the perfect match is a short file name,
  			 * we need to signal this through *res, so that
  			 * ntfs_lookup() can fix dcache aliasing issues.
  			 * As an optimization we just reuse an existing
  			 * allocation of *res.
  			 */
  			if (ie->key.file_name.file_name_type == FILE_NAME_DOS) {
  				if (!name) {
  					name = kmalloc(sizeof(ntfs_name),
  							GFP_NOFS);
  					if (!name) {
  						err = -ENOMEM;
  						goto unm_err_out;
  					}
  				}
  				name->mref = le64_to_cpu(
  						ie->data.dir.indexed_file);
  				name->type = FILE_NAME_DOS;
  				name->len = 0;
  				*res = name;
  			} else {
  				kfree(name);
  				*res = NULL;
  			}
  			mref = le64_to_cpu(ie->data.dir.indexed_file);
  			unlock_page(page);
  			ntfs_unmap_page(page);
  			return mref;
  		}
  		/*
  		 * For a case insensitive mount, we also perform a case
  		 * insensitive comparison (provided the file name is not in the
  		 * POSIX namespace). If the comparison matches, and the name is
  		 * in the WIN32 namespace, we cache the filename in *res so
  		 * that the caller, ntfs_lookup(), can work on it. If the
  		 * comparison matches, and the name is in the DOS namespace, we
  		 * only cache the mft reference and the file name type (we set
  		 * the name length to zero for simplicity).
  		 */
  		if (!NVolCaseSensitive(vol) &&
  				ie->key.file_name.file_name_type &&
  				ntfs_are_names_equal(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length,
  				IGNORE_CASE, vol->upcase, vol->upcase_len)) {
  			int name_size = sizeof(ntfs_name);
  			u8 type = ie->key.file_name.file_name_type;
  			u8 len = ie->key.file_name.file_name_length;
  
  			/* Only one case insensitive matching name allowed. */
  			if (name) {
  				ntfs_error(sb, "Found already allocated name "
  						"in phase 2. Please run chkdsk "
  						"and if that doesn't find any "
  						"errors please report you saw "
  						"this message to "
  						"linux-ntfs-dev@lists."
  						"sourceforge.net.");
  				unlock_page(page);
  				ntfs_unmap_page(page);
  				goto dir_err_out;
  			}
  
  			if (type != FILE_NAME_DOS)
  				name_size += len * sizeof(ntfschar);
  			name = kmalloc(name_size, GFP_NOFS);
  			if (!name) {
  				err = -ENOMEM;
  				goto unm_err_out;
  			}
  			name->mref = le64_to_cpu(ie->data.dir.indexed_file);
  			name->type = type;
  			if (type != FILE_NAME_DOS) {
  				name->len = len;
  				memcpy(name->name, ie->key.file_name.file_name,
  						len * sizeof(ntfschar));
  			} else
  				name->len = 0;
  			*res = name;
  		}
  		/*
  		 * Not a perfect match, need to do full blown collation so we
  		 * know which way in the B+tree we have to go.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				IGNORE_CASE, vol->upcase, vol->upcase_len);
  		/*
  		 * If uname collates before the name of the current entry, there
  		 * is definitely no such name in this index but we might need to
  		 * descend into the B+tree so we just break out of the loop.
  		 */
  		if (rc == -1)
  			break;
  		/* The names are not equal, continue the search. */
  		if (rc)
  			continue;
  		/*
  		 * Names match with case insensitive comparison, now try the
  		 * case sensitive comparison, which is required for proper
  		 * collation.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				CASE_SENSITIVE, vol->upcase, vol->upcase_len);
  		if (rc == -1)
  			break;
  		if (rc)
  			continue;
  		/*
  		 * Perfect match, this will never happen as the
  		 * ntfs_are_names_equal() call will have gotten a match but we
  		 * still treat it correctly.
  		 */
  		goto found_it2;
  	}
  	/*
  	 * We have finished with this index buffer without success. Check for
  	 * the presence of a child node.
  	 */
  	if (ie->flags & INDEX_ENTRY_NODE) {
  		if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
  			ntfs_error(sb, "Index entry with child node found in "
  					"a leaf node in directory inode 0x%lx.",
  					dir_ni->mft_no);
  			goto unm_err_out;
  		}
  		/* Child node present, descend into it. */
  		old_vcn = vcn;
  		vcn = sle64_to_cpup((sle64*)((u8*)ie +
  				le16_to_cpu(ie->length) - 8));
  		if (vcn >= 0) {
  			/* If vcn is in the same page cache page as old_vcn we
  			 * recycle the mapped page. */
  			if (old_vcn << vol->cluster_size_bits >>
  					PAGE_SHIFT == vcn <<
  					vol->cluster_size_bits >>
  					PAGE_SHIFT)
  				goto fast_descend_into_child_node;
  			unlock_page(page);
  			ntfs_unmap_page(page);
  			goto descend_into_child_node;
  		}
  		ntfs_error(sb, "Negative child node vcn in directory inode "
  				"0x%lx.", dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	/*
  	 * No child node present, return -ENOENT, unless we have got a matching
  	 * name cached in name in which case return the mft reference
  	 * associated with it.
  	 */
  	if (name) {
  		unlock_page(page);
  		ntfs_unmap_page(page);
  		return name->mref;
  	}
  	ntfs_debug("Entry not found.");
  	err = -ENOENT;
  unm_err_out:
  	unlock_page(page);
  	ntfs_unmap_page(page);
  err_out:
  	if (!err)
  		err = -EIO;
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(dir_ni);
  	if (name) {
  		kfree(name);
  		*res = NULL;
  	}
  	return ERR_MREF(err);
  dir_err_out:
  	ntfs_error(sb, "Corrupt directory.  Aborting lookup.");
  	goto err_out;
  }
  
  #if 0
  
  // TODO: (AIA)
  // The algorithm embedded in this code will be required for the time when we
  // want to support adding of entries to directories, where we require correct
  // collation of file names in order not to cause corruption of the filesystem.
  
  /**
   * ntfs_lookup_inode_by_name - find an inode in a directory given its name
   * @dir_ni:	ntfs inode of the directory in which to search for the name
   * @uname:	Unicode name for which to search in the directory
   * @uname_len:	length of the name @uname in Unicode characters
   *
   * Look for an inode with name @uname in the directory with inode @dir_ni.
   * ntfs_lookup_inode_by_name() walks the contents of the directory looking for
   * the Unicode name. If the name is found in the directory, the corresponding
   * inode number (>= 0) is returned as a mft reference in cpu format, i.e. it
   * is a 64-bit number containing the sequence number.
   *
   * On error, a negative value is returned corresponding to the error code. In
   * particular if the inode is not found -ENOENT is returned. Note that you
   * can't just check the return value for being negative, you have to check the
   * inode number for being negative which you can extract using MREC(return
   * value).
   *
   * Note, @uname_len does not include the (optional) terminating NULL character.
   */
  u64 ntfs_lookup_inode_by_name(ntfs_inode *dir_ni, const ntfschar *uname,
  		const int uname_len)
  {
  	ntfs_volume *vol = dir_ni->vol;
  	struct super_block *sb = vol->sb;
  	MFT_RECORD *m;
  	INDEX_ROOT *ir;
  	INDEX_ENTRY *ie;
  	INDEX_ALLOCATION *ia;
  	u8 *index_end;
  	u64 mref;
  	ntfs_attr_search_ctx *ctx;
  	int err, rc;
  	IGNORE_CASE_BOOL ic;
  	VCN vcn, old_vcn;
  	struct address_space *ia_mapping;
  	struct page *page;
  	u8 *kaddr;
  
  	/* Get hold of the mft record for the directory. */
  	m = map_mft_record(dir_ni);
  	if (IS_ERR(m)) {
  		ntfs_error(sb, "map_mft_record() failed with error code %ld.",
  				-PTR_ERR(m));
  		return ERR_MREF(PTR_ERR(m));
  	}
  	ctx = ntfs_attr_get_search_ctx(dir_ni, m);
  	if (!ctx) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	/* Find the index root attribute in the mft record. */
  	err = ntfs_attr_lookup(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0, NULL,
  			0, ctx);
  	if (unlikely(err)) {
  		if (err == -ENOENT) {
  			ntfs_error(sb, "Index root attribute missing in "
  					"directory inode 0x%lx.",
  					dir_ni->mft_no);
  			err = -EIO;
  		}
  		goto err_out;
  	}
  	/* Get to the index root value (it's been verified in read_inode). */
  	ir = (INDEX_ROOT*)((u8*)ctx->attr +
  			le16_to_cpu(ctx->attr->data.resident.value_offset));
  	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
  	/* The first index entry. */
  	ie = (INDEX_ENTRY*)((u8*)&ir->index +
  			le32_to_cpu(ir->index.entries_offset));
  	/*
  	 * Loop until we exceed valid memory (corruption case) or until we
  	 * reach the last entry.
  	 */
  	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
  		/* Bounds checks. */
  		if ((u8*)ie < (u8*)ctx->mrec || (u8*)ie +
  				sizeof(INDEX_ENTRY_HEADER) > index_end ||
  				(u8*)ie + le16_to_cpu(ie->key_length) >
  				index_end)
  			goto dir_err_out;
  		/*
  		 * The last entry cannot contain a name. It can however contain
  		 * a pointer to a child node in the B+tree so we just break out.
  		 */
  		if (ie->flags & INDEX_ENTRY_END)
  			break;
  		/*
  		 * If the current entry has a name type of POSIX, the name is
  		 * case sensitive and not otherwise. This has the effect of us
  		 * not being able to access any POSIX file names which collate
  		 * after the non-POSIX one when they only differ in case, but
  		 * anyone doing screwy stuff like that deserves to burn in
  		 * hell... Doing that kind of stuff on NT4 actually causes
  		 * corruption on the partition even when using SP6a and Linux
  		 * is not involved at all.
  		 */
  		ic = ie->key.file_name.file_name_type ? IGNORE_CASE :
  				CASE_SENSITIVE;
  		/*
  		 * If the names match perfectly, we are done and return the
  		 * mft reference of the inode (i.e. the inode number together
  		 * with the sequence number for consistency checking. We
  		 * convert it to cpu format before returning.
  		 */
  		if (ntfs_are_names_equal(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, ic,
  				vol->upcase, vol->upcase_len)) {
  found_it:
  			mref = le64_to_cpu(ie->data.dir.indexed_file);
  			ntfs_attr_put_search_ctx(ctx);
  			unmap_mft_record(dir_ni);
  			return mref;
  		}
  		/*
  		 * Not a perfect match, need to do full blown collation so we
  		 * know which way in the B+tree we have to go.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				IGNORE_CASE, vol->upcase, vol->upcase_len);
  		/*
  		 * If uname collates before the name of the current entry, there
  		 * is definitely no such name in this index but we might need to
  		 * descend into the B+tree so we just break out of the loop.
  		 */
  		if (rc == -1)
  			break;
  		/* The names are not equal, continue the search. */
  		if (rc)
  			continue;
  		/*
  		 * Names match with case insensitive comparison, now try the
  		 * case sensitive comparison, which is required for proper
  		 * collation.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				CASE_SENSITIVE, vol->upcase, vol->upcase_len);
  		if (rc == -1)
  			break;
  		if (rc)
  			continue;
  		/*
  		 * Perfect match, this will never happen as the
  		 * ntfs_are_names_equal() call will have gotten a match but we
  		 * still treat it correctly.
  		 */
  		goto found_it;
  	}
  	/*
  	 * We have finished with this index without success. Check for the
  	 * presence of a child node.
  	 */
  	if (!(ie->flags & INDEX_ENTRY_NODE)) {
  		/* No child node, return -ENOENT. */
  		err = -ENOENT;
  		goto err_out;
  	} /* Child node present, descend into it. */
  	/* Consistency check: Verify that an index allocation exists. */
  	if (!NInoIndexAllocPresent(dir_ni)) {
  		ntfs_error(sb, "No index allocation attribute but index entry "
  				"requires one. Directory inode 0x%lx is "
  				"corrupt or driver bug.", dir_ni->mft_no);
  		goto err_out;
  	}
  	/* Get the starting vcn of the index_block holding the child node. */
  	vcn = sle64_to_cpup((u8*)ie + le16_to_cpu(ie->length) - 8);
  	ia_mapping = VFS_I(dir_ni)->i_mapping;
  	/*
  	 * We are done with the index root and the mft record. Release them,
  	 * otherwise we deadlock with ntfs_map_page().
  	 */
  	ntfs_attr_put_search_ctx(ctx);
  	unmap_mft_record(dir_ni);
  	m = NULL;
  	ctx = NULL;
  descend_into_child_node:
  	/*
  	 * Convert vcn to index into the index allocation attribute in units
  	 * of PAGE_SIZE and map the page cache page, reading it from
  	 * disk if necessary.
  	 */
  	page = ntfs_map_page(ia_mapping, vcn <<
  			dir_ni->itype.index.vcn_size_bits >> PAGE_SHIFT);
  	if (IS_ERR(page)) {
  		ntfs_error(sb, "Failed to map directory index page, error %ld.",
  				-PTR_ERR(page));
  		err = PTR_ERR(page);
  		goto err_out;
  	}
  	lock_page(page);
  	kaddr = (u8*)page_address(page);
  fast_descend_into_child_node:
  	/* Get to the index allocation block. */
  	ia = (INDEX_ALLOCATION*)(kaddr + ((vcn <<
  			dir_ni->itype.index.vcn_size_bits) & ~PAGE_MASK));
  	/* Bounds checks. */
  	if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_SIZE) {
  		ntfs_error(sb, "Out of bounds check failed. Corrupt directory "
  				"inode 0x%lx or driver bug.", dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	/* Catch multi sector transfer fixup errors. */
  	if (unlikely(!ntfs_is_indx_record(ia->magic))) {
  		ntfs_error(sb, "Directory index record with vcn 0x%llx is "
  				"corrupt.  Corrupt inode 0x%lx.  Run chkdsk.",
  				(unsigned long long)vcn, dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
  		ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
  				"different from expected VCN (0x%llx). "
  				"Directory inode 0x%lx is corrupt or driver "
  				"bug.", (unsigned long long)
  				sle64_to_cpu(ia->index_block_vcn),
  				(unsigned long long)vcn, dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	if (le32_to_cpu(ia->index.allocated_size) + 0x18 !=
  			dir_ni->itype.index.block_size) {
  		ntfs_error(sb, "Index buffer (VCN 0x%llx) of directory inode "
  				"0x%lx has a size (%u) differing from the "
  				"directory specified size (%u). Directory "
  				"inode is corrupt or driver bug.",
  				(unsigned long long)vcn, dir_ni->mft_no,
  				le32_to_cpu(ia->index.allocated_size) + 0x18,
  				dir_ni->itype.index.block_size);
  		goto unm_err_out;
  	}
  	index_end = (u8*)ia + dir_ni->itype.index.block_size;
  	if (index_end > kaddr + PAGE_SIZE) {
  		ntfs_error(sb, "Index buffer (VCN 0x%llx) of directory inode "
  				"0x%lx crosses page boundary. Impossible! "
  				"Cannot access! This is probably a bug in the "
  				"driver.", (unsigned long long)vcn,
  				dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
  	if (index_end > (u8*)ia + dir_ni->itype.index.block_size) {
  		ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of directory "
  				"inode 0x%lx exceeds maximum size.",
  				(unsigned long long)vcn, dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	/* The first index entry. */
  	ie = (INDEX_ENTRY*)((u8*)&ia->index +
  			le32_to_cpu(ia->index.entries_offset));
  	/*
  	 * Iterate similar to above big loop but applied to index buffer, thus
  	 * loop until we exceed valid memory (corruption case) or until we
  	 * reach the last entry.
  	 */
  	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
  		/* Bounds check. */
  		if ((u8*)ie < (u8*)ia || (u8*)ie +
  				sizeof(INDEX_ENTRY_HEADER) > index_end ||
  				(u8*)ie + le16_to_cpu(ie->key_length) >
  				index_end) {
  			ntfs_error(sb, "Index entry out of bounds in "
  					"directory inode 0x%lx.",
  					dir_ni->mft_no);
  			goto unm_err_out;
  		}
  		/*
  		 * The last entry cannot contain a name. It can however contain
  		 * a pointer to a child node in the B+tree so we just break out.
  		 */
  		if (ie->flags & INDEX_ENTRY_END)
  			break;
  		/*
  		 * If the current entry has a name type of POSIX, the name is
  		 * case sensitive and not otherwise. This has the effect of us
  		 * not being able to access any POSIX file names which collate
  		 * after the non-POSIX one when they only differ in case, but
  		 * anyone doing screwy stuff like that deserves to burn in
  		 * hell... Doing that kind of stuff on NT4 actually causes
  		 * corruption on the partition even when using SP6a and Linux
  		 * is not involved at all.
  		 */
  		ic = ie->key.file_name.file_name_type ? IGNORE_CASE :
  				CASE_SENSITIVE;
  		/*
  		 * If the names match perfectly, we are done and return the
  		 * mft reference of the inode (i.e. the inode number together
  		 * with the sequence number for consistency checking. We
  		 * convert it to cpu format before returning.
  		 */
  		if (ntfs_are_names_equal(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, ic,
  				vol->upcase, vol->upcase_len)) {
  found_it2:
  			mref = le64_to_cpu(ie->data.dir.indexed_file);
  			unlock_page(page);
  			ntfs_unmap_page(page);
  			return mref;
  		}
  		/*
  		 * Not a perfect match, need to do full blown collation so we
  		 * know which way in the B+tree we have to go.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				IGNORE_CASE, vol->upcase, vol->upcase_len);
  		/*
  		 * If uname collates before the name of the current entry, there
  		 * is definitely no such name in this index but we might need to
  		 * descend into the B+tree so we just break out of the loop.
  		 */
  		if (rc == -1)
  			break;
  		/* The names are not equal, continue the search. */
  		if (rc)
  			continue;
  		/*
  		 * Names match with case insensitive comparison, now try the
  		 * case sensitive comparison, which is required for proper
  		 * collation.
  		 */
  		rc = ntfs_collate_names(uname, uname_len,
  				(ntfschar*)&ie->key.file_name.file_name,
  				ie->key.file_name.file_name_length, 1,
  				CASE_SENSITIVE, vol->upcase, vol->upcase_len);
  		if (rc == -1)
  			break;
  		if (rc)
  			continue;
  		/*
  		 * Perfect match, this will never happen as the
  		 * ntfs_are_names_equal() call will have gotten a match but we
  		 * still treat it correctly.
  		 */
  		goto found_it2;
  	}
  	/*
  	 * We have finished with this index buffer without success. Check for
  	 * the presence of a child node.
  	 */
  	if (ie->flags & INDEX_ENTRY_NODE) {
  		if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
  			ntfs_error(sb, "Index entry with child node found in "
  					"a leaf node in directory inode 0x%lx.",
  					dir_ni->mft_no);
  			goto unm_err_out;
  		}
  		/* Child node present, descend into it. */
  		old_vcn = vcn;
  		vcn = sle64_to_cpup((u8*)ie + le16_to_cpu(ie->length) - 8);
  		if (vcn >= 0) {
  			/* If vcn is in the same page cache page as old_vcn we
  			 * recycle the mapped page. */
  			if (old_vcn << vol->cluster_size_bits >>
  					PAGE_SHIFT == vcn <<
  					vol->cluster_size_bits >>
  					PAGE_SHIFT)
  				goto fast_descend_into_child_node;
  			unlock_page(page);
  			ntfs_unmap_page(page);
  			goto descend_into_child_node;
  		}
  		ntfs_error(sb, "Negative child node vcn in directory inode "
  				"0x%lx.", dir_ni->mft_no);
  		goto unm_err_out;
  	}
  	/* No child node, return -ENOENT. */
  	ntfs_debug("Entry not found.");
  	err = -ENOENT;
  unm_err_out:
  	unlock_page(page);
  	ntfs_unmap_page(page);
  err_out:
  	if (!err)
  		err = -EIO;
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(dir_ni);
  	return ERR_MREF(err);
  dir_err_out:
  	ntfs_error(sb, "Corrupt directory. Aborting lookup.");
  	goto err_out;
  }
  
  #endif
  
  /**
   * ntfs_filldir - ntfs specific filldir method
   * @vol:	current ntfs volume
   * @ndir:	ntfs inode of current directory
   * @ia_page:	page in which the index allocation buffer @ie is in resides
   * @ie:		current index entry
   * @name:	buffer to use for the converted name
   * @actor:	what to feed the entries to
   *
   * Convert the Unicode @name to the loaded NLS and pass it to the @filldir
   * callback.
   *
   * If @ia_page is not NULL it is the locked page containing the index
   * allocation block containing the index entry @ie.
   *
   * Note, we drop (and then reacquire) the page lock on @ia_page across the
   * @filldir() call otherwise we would deadlock with NFSd when it calls ->lookup
   * since ntfs_lookup() will lock the same page.  As an optimization, we do not
   * retake the lock if we are returning a non-zero value as ntfs_readdir()
   * would need to drop the lock immediately anyway.
   */
  static inline int ntfs_filldir(ntfs_volume *vol,
  		ntfs_inode *ndir, struct page *ia_page, INDEX_ENTRY *ie,
  		u8 *name, struct dir_context *actor)
  {
  	unsigned long mref;
  	int name_len;
  	unsigned dt_type;
  	FILE_NAME_TYPE_FLAGS name_type;
  
  	name_type = ie->key.file_name.file_name_type;
  	if (name_type == FILE_NAME_DOS) {
  		ntfs_debug("Skipping DOS name space entry.");
  		return 0;
  	}
  	if (MREF_LE(ie->data.dir.indexed_file) == FILE_root) {
  		ntfs_debug("Skipping root directory self reference entry.");
  		return 0;
  	}
  	if (MREF_LE(ie->data.dir.indexed_file) < FILE_first_user &&
  			!NVolShowSystemFiles(vol)) {
  		ntfs_debug("Skipping system file.");
  		return 0;
  	}
  	name_len = ntfs_ucstonls(vol, (ntfschar*)&ie->key.file_name.file_name,
  			ie->key.file_name.file_name_length, &name,
  			NTFS_MAX_NAME_LEN * NLS_MAX_CHARSET_SIZE + 1);
  	if (name_len <= 0) {
  		ntfs_warning(vol->sb, "Skipping unrepresentable inode 0x%llx.",
  				(long long)MREF_LE(ie->data.dir.indexed_file));
  		return 0;
  	}
  	if (ie->key.file_name.file_attributes &
  			FILE_ATTR_DUP_FILE_NAME_INDEX_PRESENT)
  		dt_type = DT_DIR;
  	else
  		dt_type = DT_REG;
  	mref = MREF_LE(ie->data.dir.indexed_file);
  	/*
  	 * Drop the page lock otherwise we deadlock with NFS when it calls
  	 * ->lookup since ntfs_lookup() will lock the same page.
  	 */
  	if (ia_page)
  		unlock_page(ia_page);
  	ntfs_debug("Calling filldir for %s with len %i, fpos 0x%llx, inode "
  			"0x%lx, DT_%s.", name, name_len, actor->pos, mref,
  			dt_type == DT_DIR ? "DIR" : "REG");
  	if (!dir_emit(actor, name, name_len, mref, dt_type))
  		return 1;
  	/* Relock the page but not if we are aborting ->readdir. */
  	if (ia_page)
  		lock_page(ia_page);
  	return 0;
  }
  
  /*
   * We use the same basic approach as the old NTFS driver, i.e. we parse the
   * index root entries and then the index allocation entries that are marked
   * as in use in the index bitmap.
   *
   * While this will return the names in random order this doesn't matter for
   * ->readdir but OTOH results in a faster ->readdir.
   *
   * VFS calls ->readdir without BKL but with i_mutex held. This protects the VFS
   * parts (e.g. ->f_pos and ->i_size, and it also protects against directory
   * modifications).
   *
   * Locking:  - Caller must hold i_mutex on the directory.
   *	     - Each page cache page in the index allocation mapping must be
   *	       locked whilst being accessed otherwise we may find a corrupt
   *	       page due to it being under ->writepage at the moment which
   *	       applies the mst protection fixups before writing out and then
   *	       removes them again after the write is complete after which it 
   *	       unlocks the page.
   */
  static int ntfs_readdir(struct file *file, struct dir_context *actor)
  {
  	s64 ia_pos, ia_start, prev_ia_pos, bmp_pos;
  	loff_t i_size;
  	struct inode *bmp_vi, *vdir = file_inode(file);
  	struct super_block *sb = vdir->i_sb;
  	ntfs_inode *ndir = NTFS_I(vdir);
  	ntfs_volume *vol = NTFS_SB(sb);
  	MFT_RECORD *m;
  	INDEX_ROOT *ir = NULL;
  	INDEX_ENTRY *ie;
  	INDEX_ALLOCATION *ia;
  	u8 *name = NULL;
  	int rc, err, ir_pos, cur_bmp_pos;
  	struct address_space *ia_mapping, *bmp_mapping;
  	struct page *bmp_page = NULL, *ia_page = NULL;
  	u8 *kaddr, *bmp, *index_end;
  	ntfs_attr_search_ctx *ctx;
  
  	ntfs_debug("Entering for inode 0x%lx, fpos 0x%llx.",
  			vdir->i_ino, actor->pos);
  	rc = err = 0;
  	/* Are we at end of dir yet? */
  	i_size = i_size_read(vdir);
  	if (actor->pos >= i_size + vol->mft_record_size)
  		return 0;
  	/* Emulate . and .. for all directories. */
  	if (!dir_emit_dots(file, actor))
  		return 0;
  	m = NULL;
  	ctx = NULL;
  	/*
  	 * Allocate a buffer to store the current name being processed
  	 * converted to format determined by current NLS.
  	 */
  	name = kmalloc(NTFS_MAX_NAME_LEN * NLS_MAX_CHARSET_SIZE + 1, GFP_NOFS);
  	if (unlikely(!name)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	/* Are we jumping straight into the index allocation attribute? */
  	if (actor->pos >= vol->mft_record_size)
  		goto skip_index_root;
  	/* Get hold of the mft record for the directory. */
  	m = map_mft_record(ndir);
  	if (IS_ERR(m)) {
  		err = PTR_ERR(m);
  		m = NULL;
  		goto err_out;
  	}
  	ctx = ntfs_attr_get_search_ctx(ndir, m);
  	if (unlikely(!ctx)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	/* Get the offset into the index root attribute. */
  	ir_pos = (s64)actor->pos;
  	/* Find the index root attribute in the mft record. */
  	err = ntfs_attr_lookup(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0, NULL,
  			0, ctx);
  	if (unlikely(err)) {
  		ntfs_error(sb, "Index root attribute missing in directory "
  				"inode 0x%lx.", vdir->i_ino);
  		goto err_out;
  	}
  	/*
  	 * Copy the index root attribute value to a buffer so that we can put
  	 * the search context and unmap the mft record before calling the
  	 * filldir() callback.  We need to do this because of NFSd which calls
  	 * ->lookup() from its filldir callback() and this causes NTFS to
  	 * deadlock as ntfs_lookup() maps the mft record of the directory and
  	 * we have got it mapped here already.  The only solution is for us to
  	 * unmap the mft record here so that a call to ntfs_lookup() is able to
  	 * map the mft record without deadlocking.
  	 */
  	rc = le32_to_cpu(ctx->attr->data.resident.value_length);
  	ir = kmalloc(rc, GFP_NOFS);
  	if (unlikely(!ir)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	/* Copy the index root value (it has been verified in read_inode). */
  	memcpy(ir, (u8*)ctx->attr +
  			le16_to_cpu(ctx->attr->data.resident.value_offset), rc);
  	ntfs_attr_put_search_ctx(ctx);
  	unmap_mft_record(ndir);
  	ctx = NULL;
  	m = NULL;
  	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
  	/* The first index entry. */
  	ie = (INDEX_ENTRY*)((u8*)&ir->index +
  			le32_to_cpu(ir->index.entries_offset));
  	/*
  	 * Loop until we exceed valid memory (corruption case) or until we
  	 * reach the last entry or until filldir tells us it has had enough
  	 * or signals an error (both covered by the rc test).
  	 */
  	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
  		ntfs_debug("In index root, offset 0x%zx.", (u8*)ie - (u8*)ir);
  		/* Bounds checks. */
  		if (unlikely((u8*)ie < (u8*)ir || (u8*)ie +
  				sizeof(INDEX_ENTRY_HEADER) > index_end ||
  				(u8*)ie + le16_to_cpu(ie->key_length) >
  				index_end))
  			goto err_out;
  		/* The last entry cannot contain a name. */
  		if (ie->flags & INDEX_ENTRY_END)
  			break;
  		/* Skip index root entry if continuing previous readdir. */
  		if (ir_pos > (u8*)ie - (u8*)ir)
  			continue;
  		/* Advance the position even if going to skip the entry. */
  		actor->pos = (u8*)ie - (u8*)ir;
  		/* Submit the name to the filldir callback. */
  		rc = ntfs_filldir(vol, ndir, NULL, ie, name, actor);
  		if (rc) {
  			kfree(ir);
  			goto abort;
  		}
  	}
  	/* We are done with the index root and can free the buffer. */
  	kfree(ir);
  	ir = NULL;
  	/* If there is no index allocation attribute we are finished. */
  	if (!NInoIndexAllocPresent(ndir))
  		goto EOD;
  	/* Advance fpos to the beginning of the index allocation. */
  	actor->pos = vol->mft_record_size;
  skip_index_root:
  	kaddr = NULL;
  	prev_ia_pos = -1LL;
  	/* Get the offset into the index allocation attribute. */
  	ia_pos = (s64)actor->pos - vol->mft_record_size;
  	ia_mapping = vdir->i_mapping;
  	ntfs_debug("Inode 0x%lx, getting index bitmap.", vdir->i_ino);
  	bmp_vi = ntfs_attr_iget(vdir, AT_BITMAP, I30, 4);
  	if (IS_ERR(bmp_vi)) {
  		ntfs_error(sb, "Failed to get bitmap attribute.");
  		err = PTR_ERR(bmp_vi);
  		goto err_out;
  	}
  	bmp_mapping = bmp_vi->i_mapping;
  	/* Get the starting bitmap bit position and sanity check it. */
  	bmp_pos = ia_pos >> ndir->itype.index.block_size_bits;
  	if (unlikely(bmp_pos >> 3 >= i_size_read(bmp_vi))) {
  		ntfs_error(sb, "Current index allocation position exceeds "
  				"index bitmap size.");
  		goto iput_err_out;
  	}
  	/* Get the starting bit position in the current bitmap page. */
  	cur_bmp_pos = bmp_pos & ((PAGE_SIZE * 8) - 1);
  	bmp_pos &= ~(u64)((PAGE_SIZE * 8) - 1);
  get_next_bmp_page:
  	ntfs_debug("Reading bitmap with page index 0x%llx, bit ofs 0x%llx",
  			(unsigned long long)bmp_pos >> (3 + PAGE_SHIFT),
  			(unsigned long long)bmp_pos &
  			(unsigned long long)((PAGE_SIZE * 8) - 1));
  	bmp_page = ntfs_map_page(bmp_mapping,
  			bmp_pos >> (3 + PAGE_SHIFT));
  	if (IS_ERR(bmp_page)) {
  		ntfs_error(sb, "Reading index bitmap failed.");
  		err = PTR_ERR(bmp_page);
  		bmp_page = NULL;
  		goto iput_err_out;
  	}
  	bmp = (u8*)page_address(bmp_page);
  	/* Find next index block in use. */
  	while (!(bmp[cur_bmp_pos >> 3] & (1 << (cur_bmp_pos & 7)))) {
  find_next_index_buffer:
  		cur_bmp_pos++;
  		/*
  		 * If we have reached the end of the bitmap page, get the next
  		 * page, and put away the old one.
  		 */
  		if (unlikely((cur_bmp_pos >> 3) >= PAGE_SIZE)) {
  			ntfs_unmap_page(bmp_page);
  			bmp_pos += PAGE_SIZE * 8;
  			cur_bmp_pos = 0;
  			goto get_next_bmp_page;
  		}
  		/* If we have reached the end of the bitmap, we are done. */
  		if (unlikely(((bmp_pos + cur_bmp_pos) >> 3) >= i_size))
  			goto unm_EOD;
  		ia_pos = (bmp_pos + cur_bmp_pos) <<
  				ndir->itype.index.block_size_bits;
  	}
  	ntfs_debug("Handling index buffer 0x%llx.",
  			(unsigned long long)bmp_pos + cur_bmp_pos);
  	/* If the current index buffer is in the same page we reuse the page. */
  	if ((prev_ia_pos & (s64)PAGE_MASK) !=
  			(ia_pos & (s64)PAGE_MASK)) {
  		prev_ia_pos = ia_pos;
  		if (likely(ia_page != NULL)) {
  			unlock_page(ia_page);
  			ntfs_unmap_page(ia_page);
  		}
  		/*
  		 * Map the page cache page containing the current ia_pos,
  		 * reading it from disk if necessary.
  		 */
  		ia_page = ntfs_map_page(ia_mapping, ia_pos >> PAGE_SHIFT);
  		if (IS_ERR(ia_page)) {
  			ntfs_error(sb, "Reading index allocation data failed.");
  			err = PTR_ERR(ia_page);
  			ia_page = NULL;
  			goto err_out;
  		}
  		lock_page(ia_page);
  		kaddr = (u8*)page_address(ia_page);
  	}
  	/* Get the current index buffer. */
  	ia = (INDEX_ALLOCATION*)(kaddr + (ia_pos & ~PAGE_MASK &
  					  ~(s64)(ndir->itype.index.block_size - 1)));
  	/* Bounds checks. */
  	if (unlikely((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_SIZE)) {
  		ntfs_error(sb, "Out of bounds check failed. Corrupt directory "
  				"inode 0x%lx or driver bug.", vdir->i_ino);
  		goto err_out;
  	}
  	/* Catch multi sector transfer fixup errors. */
  	if (unlikely(!ntfs_is_indx_record(ia->magic))) {
  		ntfs_error(sb, "Directory index record with vcn 0x%llx is "
  				"corrupt.  Corrupt inode 0x%lx.  Run chkdsk.",
  				(unsigned long long)ia_pos >>
  				ndir->itype.index.vcn_size_bits, vdir->i_ino);
  		goto err_out;
  	}
  	if (unlikely(sle64_to_cpu(ia->index_block_vcn) != (ia_pos &
  			~(s64)(ndir->itype.index.block_size - 1)) >>
  			ndir->itype.index.vcn_size_bits)) {
  		ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
  				"different from expected VCN (0x%llx). "
  				"Directory inode 0x%lx is corrupt or driver "
  				"bug. ", (unsigned long long)
  				sle64_to_cpu(ia->index_block_vcn),
  				(unsigned long long)ia_pos >>
  				ndir->itype.index.vcn_size_bits, vdir->i_ino);
  		goto err_out;
  	}
  	if (unlikely(le32_to_cpu(ia->index.allocated_size) + 0x18 !=
  			ndir->itype.index.block_size)) {
  		ntfs_error(sb, "Index buffer (VCN 0x%llx) of directory inode "
  				"0x%lx has a size (%u) differing from the "
  				"directory specified size (%u). Directory "
  				"inode is corrupt or driver bug.",
  				(unsigned long long)ia_pos >>
  				ndir->itype.index.vcn_size_bits, vdir->i_ino,
  				le32_to_cpu(ia->index.allocated_size) + 0x18,
  				ndir->itype.index.block_size);
  		goto err_out;
  	}
  	index_end = (u8*)ia + ndir->itype.index.block_size;
  	if (unlikely(index_end > kaddr + PAGE_SIZE)) {
  		ntfs_error(sb, "Index buffer (VCN 0x%llx) of directory inode "
  				"0x%lx crosses page boundary. Impossible! "
  				"Cannot access! This is probably a bug in the "
  				"driver.", (unsigned long long)ia_pos >>
  				ndir->itype.index.vcn_size_bits, vdir->i_ino);
  		goto err_out;
  	}
  	ia_start = ia_pos & ~(s64)(ndir->itype.index.block_size - 1);
  	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
  	if (unlikely(index_end > (u8*)ia + ndir->itype.index.block_size)) {
  		ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of directory "
  				"inode 0x%lx exceeds maximum size.",
  				(unsigned long long)ia_pos >>
  				ndir->itype.index.vcn_size_bits, vdir->i_ino);
  		goto err_out;
  	}
  	/* The first index entry in this index buffer. */
  	ie = (INDEX_ENTRY*)((u8*)&ia->index +
  			le32_to_cpu(ia->index.entries_offset));
  	/*
  	 * Loop until we exceed valid memory (corruption case) or until we
  	 * reach the last entry or until filldir tells us it has had enough
  	 * or signals an error (both covered by the rc test).
  	 */
  	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
  		ntfs_debug("In index allocation, offset 0x%llx.",
  				(unsigned long long)ia_start +
  				(unsigned long long)((u8*)ie - (u8*)ia));
  		/* Bounds checks. */
  		if (unlikely((u8*)ie < (u8*)ia || (u8*)ie +
  				sizeof(INDEX_ENTRY_HEADER) > index_end ||
  				(u8*)ie + le16_to_cpu(ie->key_length) >
  				index_end))
  			goto err_out;
  		/* The last entry cannot contain a name. */
  		if (ie->flags & INDEX_ENTRY_END)
  			break;
  		/* Skip index block entry if continuing previous readdir. */
  		if (ia_pos - ia_start > (u8*)ie - (u8*)ia)
  			continue;
  		/* Advance the position even if going to skip the entry. */
  		actor->pos = (u8*)ie - (u8*)ia +
  				(sle64_to_cpu(ia->index_block_vcn) <<
  				ndir->itype.index.vcn_size_bits) +
  				vol->mft_record_size;
  		/*
  		 * Submit the name to the @filldir callback.  Note,
  		 * ntfs_filldir() drops the lock on @ia_page but it retakes it
  		 * before returning, unless a non-zero value is returned in
  		 * which case the page is left unlocked.
  		 */
  		rc = ntfs_filldir(vol, ndir, ia_page, ie, name, actor);
  		if (rc) {
  			/* @ia_page is already unlocked in this case. */
  			ntfs_unmap_page(ia_page);
  			ntfs_unmap_page(bmp_page);
  			iput(bmp_vi);
  			goto abort;
  		}
  	}
  	goto find_next_index_buffer;
  unm_EOD:
  	if (ia_page) {
  		unlock_page(ia_page);
  		ntfs_unmap_page(ia_page);
  	}
  	ntfs_unmap_page(bmp_page);
  	iput(bmp_vi);
  EOD:
  	/* We are finished, set fpos to EOD. */
  	actor->pos = i_size + vol->mft_record_size;
  abort:
  	kfree(name);
  	return 0;
  err_out:
  	if (bmp_page) {
  		ntfs_unmap_page(bmp_page);
  iput_err_out:
  		iput(bmp_vi);
  	}
  	if (ia_page) {
  		unlock_page(ia_page);
  		ntfs_unmap_page(ia_page);
  	}
  	kfree(ir);
  	kfree(name);
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(ndir);
  	if (!err)
  		err = -EIO;
  	ntfs_debug("Failed. Returning error code %i.", -err);
  	return err;
  }
  
  /**
   * ntfs_dir_open - called when an inode is about to be opened
   * @vi:		inode to be opened
   * @filp:	file structure describing the inode
   *
   * Limit directory size to the page cache limit on architectures where unsigned
   * long is 32-bits. This is the most we can do for now without overflowing the
   * page cache page index. Doing it this way means we don't run into problems
   * because of existing too large directories. It would be better to allow the
   * user to read the accessible part of the directory but I doubt very much
   * anyone is going to hit this check on a 32-bit architecture, so there is no
   * point in adding the extra complexity required to support this.
   *
   * On 64-bit architectures, the check is hopefully optimized away by the
   * compiler.
   */
  static int ntfs_dir_open(struct inode *vi, struct file *filp)
  {
  	if (sizeof(unsigned long) < 8) {
  		if (i_size_read(vi) > MAX_LFS_FILESIZE)
  			return -EFBIG;
  	}
  	return 0;
  }
  
  #ifdef NTFS_RW
  
  /**
   * ntfs_dir_fsync - sync a directory to disk
   * @filp:	directory to be synced
   * @dentry:	dentry describing the directory to sync
   * @datasync:	if non-zero only flush user data and not metadata
   *
   * Data integrity sync of a directory to disk.  Used for fsync, fdatasync, and
   * msync system calls.  This function is based on file.c::ntfs_file_fsync().
   *
   * Write the mft record and all associated extent mft records as well as the
   * $INDEX_ALLOCATION and $BITMAP attributes and then sync the block device.
   *
   * If @datasync is true, we do not wait on the inode(s) to be written out
   * but we always wait on the page cache pages to be written out.
   *
   * Note: In the past @filp could be NULL so we ignore it as we don't need it
   * anyway.
   *
   * Locking: Caller must hold i_mutex on the inode.
   *
   * TODO: We should probably also write all attribute/index inodes associated
   * with this inode but since we have no simple way of getting to them we ignore
   * this problem for now.  We do write the $BITMAP attribute if it is present
   * which is the important one for a directory so things are not too bad.
   */
  static int ntfs_dir_fsync(struct file *filp, loff_t start, loff_t end,
  			  int datasync)
  {
  	struct inode *bmp_vi, *vi = filp->f_mapping->host;
  	int err, ret;
  	ntfs_attr na;
  
  	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
  
  	err = file_write_and_wait_range(filp, start, end);
  	if (err)
  		return err;
  	inode_lock(vi);
  
  	BUG_ON(!S_ISDIR(vi->i_mode));
  	/* If the bitmap attribute inode is in memory sync it, too. */
  	na.mft_no = vi->i_ino;
  	na.type = AT_BITMAP;
  	na.name = I30;
  	na.name_len = 4;
  	bmp_vi = ilookup5(vi->i_sb, vi->i_ino, ntfs_test_inode, &na);
  	if (bmp_vi) {
   		write_inode_now(bmp_vi, !datasync);
  		iput(bmp_vi);
  	}
  	ret = __ntfs_write_inode(vi, 1);
  	write_inode_now(vi, !datasync);
  	err = sync_blockdev(vi->i_sb->s_bdev);
  	if (unlikely(err && !ret))
  		ret = err;
  	if (likely(!ret))
  		ntfs_debug("Done.");
  	else
  		ntfs_warning(vi->i_sb, "Failed to f%ssync inode 0x%lx.  Error "
  				"%u.", datasync ? "data" : "", vi->i_ino, -ret);
  	inode_unlock(vi);
  	return ret;
  }
  
  #endif /* NTFS_RW */
  
  const struct file_operations ntfs_dir_ops = {
  	.llseek		= generic_file_llseek,	/* Seek inside directory. */
  	.read		= generic_read_dir,	/* Return -EISDIR. */
  	.iterate	= ntfs_readdir,		/* Read directory contents. */
  #ifdef NTFS_RW
  	.fsync		= ntfs_dir_fsync,	/* Sync a directory to disk. */
  #endif /* NTFS_RW */
  	/*.ioctl	= ,*/			/* Perform function on the
  						   mounted filesystem. */
  	.open		= ntfs_dir_open,	/* Open directory. */
  };
  