path: root/fs/ntfs/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 $I30 as a global constant.
 */
ntfschar I30[5] = { cpu_to_le16('$'), 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.