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dir.c

/**
 * dir.c - NTFS kernel directory operations. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2007 Anton Altaparmakov
 * Copyright (c) 2002 Richard Russon
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/buffer_head.h>

#include "dir.h"
#include "aops.h"
#include "attrib.h"
#include "mft.h"
#include "debug.h"
#include "ntfs.h"

/**
 * The little endian Unicode string $I30 as a global constant.
 */
ntfschar I30[5] = { const_cpu_to_le16('$'), const_cpu_to_le16('I'),
            const_cpu_to_le16('3'), const_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_CACHE_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_CACHE_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_CACHE_MASK));
      /* Bounds checks. */
      if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_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_CACHE_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_CACHE_SHIFT == vcn <<
                              vol->cluster_size_bits >>
                              PAGE_CACHE_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_CACHE_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_CACHE_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_CACHE_MASK));
      /* Bounds checks. */
      if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_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_CACHE_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_CACHE_SHIFT == vcn <<
                              vol->cluster_size_bits >>
                              PAGE_CACHE_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
 * @fpos:   position in the directory
 * @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
 * @dirent: vfs filldir callback context
 * @filldir:      vfs filldir callback
 *
 * 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, loff_t fpos,
            ntfs_inode *ndir, struct page *ia_page, INDEX_ENTRY *ie,
            u8 *name, void *dirent, filldir_t filldir)
{
      unsigned long mref;
      int name_len, rc;
      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, fpos, mref,
                  dt_type == DT_DIR ? "DIR" : "REG");
      rc = filldir(dirent, name, name_len, fpos, mref, dt_type);
      /* Relock the page but not if we are aborting ->readdir. */
      if (!rc && ia_page)
            lock_page(ia_page);
      return rc;
}

/*
 * 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 *filp, void *dirent, filldir_t filldir)
{
      s64 ia_pos, ia_start, prev_ia_pos, bmp_pos;
      loff_t fpos, i_size;
      struct inode *bmp_vi, *vdir = filp->f_path.dentry->d_inode;
      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;

      fpos = filp->f_pos;
      ntfs_debug("Entering for inode 0x%lx, fpos 0x%llx.",
                  vdir->i_ino, fpos);
      rc = err = 0;
      /* Are we at end of dir yet? */
      i_size = i_size_read(vdir);
      if (fpos >= i_size + vol->mft_record_size)
            goto done;
      /* Emulate . and .. for all directories. */
      if (!fpos) {
            ntfs_debug("Calling filldir for . with len 1, fpos 0x0, "
                        "inode 0x%lx, DT_DIR.", vdir->i_ino);
            rc = filldir(dirent, ".", 1, fpos, vdir->i_ino, DT_DIR);
            if (rc)
                  goto done;
            fpos++;
      }
      if (fpos == 1) {
            ntfs_debug("Calling filldir for .. with len 2, fpos 0x1, "
                        "inode 0x%lx, DT_DIR.",
                        (unsigned long)parent_ino(filp->f_path.dentry));
            rc = filldir(dirent, "..", 2, fpos,
                        parent_ino(filp->f_path.dentry), DT_DIR);
            if (rc)
                  goto done;
            fpos++;
      }
      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 (fpos >= 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)fpos;
      /* 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. */
            fpos = (u8*)ie - (u8*)ir;
            /* Submit the name to the filldir callback. */
            rc = ntfs_filldir(vol, fpos, ndir, NULL, ie, name, dirent,
                        filldir);
            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. */
      fpos = vol->mft_record_size;
skip_index_root:
      kaddr = NULL;
      prev_ia_pos = -1LL;
      /* Get the offset into the index allocation attribute. */
      ia_pos = (s64)fpos - 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_CACHE_SIZE * 8) - 1);
      bmp_pos &= ~(u64)((PAGE_CACHE_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_CACHE_SHIFT),
                  (unsigned long long)bmp_pos &
                  (unsigned long long)((PAGE_CACHE_SIZE * 8) - 1));
      bmp_page = ntfs_map_page(bmp_mapping,
                  bmp_pos >> (3 + PAGE_CACHE_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_CACHE_SIZE)) {
                  ntfs_unmap_page(bmp_page);
                  bmp_pos += PAGE_CACHE_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_CACHE_MASK) !=
                  (ia_pos & (s64)PAGE_CACHE_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_CACHE_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_CACHE_MASK &
                  ~(s64)(ndir->itype.index.block_size - 1)));
      /* Bounds checks. */
      if (unlikely((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_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_CACHE_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. */
            fpos = (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, fpos, ndir, ia_page, ie, name, dirent,
                        filldir);
            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. */
      fpos = i_size + vol->mft_record_size;
abort:
      kfree(name);
done:
#ifdef DEBUG
      if (!rc)
            ntfs_debug("EOD, fpos 0x%llx, returning 0.", fpos);
      else
            ntfs_debug("filldir returned %i, fpos 0x%llx, returning 0.",
                        rc, fpos);
#endif
      filp->f_pos = fpos;
      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);
      filp->f_pos = fpos;
      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, struct dentry *dentry,
            int datasync)
{
      struct inode *bmp_vi, *vi = dentry->d_inode;
      int err, ret;
      ntfs_attr na;

      ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
      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, (test_t)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);
      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. */
      .readdir    = ntfs_readdir,         /* Read directory contents. */
#ifdef NTFS_RW
      .fsync            = ntfs_dir_fsync, /* Sync a directory to disk. */
      /*.aio_fsync      = ,*/             /* Sync all outstanding async
                                       i/o operations on a kiocb. */
#endif /* NTFS_RW */
      /*.ioctl    = ,*/             /* Perform function on the
                                       mounted filesystem. */
      .open       = ntfs_dir_open,  /* Open directory. */
};

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