Merge tag 'regmap-fix-v5.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux/fpc-iii.git] / fs / ntfs / dir.c

// 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. */
};