ntfs-3g/libntfs/mft.c

/*
 * $Id$
 *
 * mft.c - Mft record handling code. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2000-2002 Anton Altaparmakov.
 *
 * 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 <stdlib.h>
#include <errno.h>
#include <string.h>

#include "mft.h"
#include "disk_io.h"
#include "debug.h"
#include "bitmap.h"
#include "attrib.h"

/**
 * ntfs_read_mft_records - read records from the mft from disk
 * @vol:	volume to read from
 * @mref:	starting mft record number to read
 * @count:	number of mft records to read
 * @b:		output data buffer
 *
 * Read @count mft records starting at @mref from volume @vol into buffer
 * @b. Return 0 on success or -1 on error, with errno set to the error
 * code.
 *
 * The read mft records are mst deprotected and are hence ready to use. The
 * caller should check each record with is_baad_record() in case mst
 * deprotection failed.
 *
 * NOTE: @b has to be at least of size @count * vol->mft_record_size.
 */
int ntfs_read_mft_records(const ntfs_volume *vol, const MFT_REF mref,
		const s64 count, MFT_RECORD *b)
{
	s64 br;
	VCN m;

	Dprintf("%s(): Entering for inode 0x%Lx.\n", __FUNCTION__, MREF(mref));
	if (!vol || !vol->mft_na || !b || count < 0) {
		errno = EINVAL;
		return -1;
	}
	m = MREF(mref);
	if (m + count > vol->nr_mft_records) {
		errno = ESPIPE;
		return -1;
	}
	br = ntfs_attr_mst_pread(vol->mft_na, m << vol->mft_record_size_bits,
			count, vol->mft_record_size, b);
	if (br != count) {
		if (br != -1)
			errno = EIO;
		if (br >= 0)
			Dputs("Error: partition is smaller than it should be!");
		else
			Dperror("Error reading $Mft record(s)");
		return -1;
	}
	return 0;
}

/**
 * ntfs_write_mft_records - write mft records to disk
 * @vol:	volume to write to
 * @mref:	starting mft record number to write
 * @count:	number of mft records to write
 * @b:		data buffer containing the mft records to write
 *
 * Write @count mft records starting at @mref from data buffer @b to volume
 * @vol. Return 0 on success or -1 on error, with errno set to the error code.
 *
 * Before the mft records are written, they are mst protected. After the write,
 * they are deprotected again, thus resulting in an increase in the update
 * sequence number inside the data buffer @b.
 *
 * If any mft records are written which are also represented in the mft mirror
 * $MFTMirr, we make a copy of the relevant parts of the data buffer @b into a
 * temporary buffer before we do the actual write. Then if at least one mft
 * record was successfully written, we write the appropriate mft records from
 * the copied buffer to the mft mirror, too.
 */
int ntfs_write_mft_records(const ntfs_volume *vol, const MFT_REF mref,
		const s64 count, MFT_RECORD *b)
{
	s64 bw;
	VCN m;
	void *bmirr = NULL;
	int cnt = 0, res = 0;

	Dprintf("%s(): Entering for inode 0x%Lx.\n", __FUNCTION__, MREF(mref));
	if (!vol || !vol->mft_na || !b || count < 0) {
		errno = EINVAL;
		return -1;
	}
	m = MREF(mref);
	if (m < vol->mftmirr_size) {
		cnt = vol->mftmirr_size - m;
		bmirr = malloc(cnt * vol->mft_record_size);
		if (!bmirr)
			return -1;
		memcpy(bmirr, b, cnt * vol->mft_record_size);
	}
	if (m + count > vol->nr_mft_records) {
		// TODO: Need to extend $MFT. This is not just normal attribute
		// extension as many rules need to be observed. (AIA)
		if (bmirr);
			free(bmirr);
		errno = ENOTSUP;
		return -1;
	}
	bw = ntfs_attr_mst_pwrite(vol->mft_na, m << vol->mft_record_size_bits,
			count, vol->mft_record_size, b);
	if (bw != count) {
		if (bw != -1)
			errno = EIO;
		if (bw >= 0)
			Dputs("Error: partial write while writing $Mft "
					"record(s)!\n");
		else
			Dperror("Error writing $Mft record(s)");
		res = errno;
	}
	if (bmirr && bw > 0) {
		if (bw < cnt)
			cnt = bw;
		bw = ntfs_attr_mst_pwrite(vol->mftmirr_na,
				m << vol->mft_record_size_bits, cnt,
				vol->mft_record_size, bmirr);
		if (bw != cnt) {
			if (bw != -1)
				errno = EIO;
			Dputs("Error: failed to sync $MFTMirr! Run chkdsk.");
			res = errno;
		}
	}
	if (bmirr)
		free(bmirr);
	if (!res)
		return res;
	errno = res;
	return -1;
}

/**
 * ntfs_read_file_record - read a FILE record from the mft from disk
 * @vol:	volume to read from
 * @mref:	mft reference specifying mft record to read
 * @mrec:	address of pointer in which to return the mft record
 * @attr:	address of pointer in which to return the first attribute
 *
 * Read a FILE record from the mft of @vol from the storage medium. @mref
 * specifies the mft record to read, including the sequence number, which can
 * be 0 if no sequence number checking is to be performed.
 *
 * The function allocates a buffer large enough to hold the mft record and
 * reads the record into the buffer (mst deprotecting it in the process).
 * *@mrec is then set to point to the buffer.
 *
 * If @attr is not NULL, *@attr is set to point to the first attribute in the
 * mft record, i.e. *@attr is a pointer into *@mrec.
 *
 * Return 0 on success, or -1 on error, with errno set to the error code.
 *
 * The read mft record is checked for having the magic FILE,
 * and for having a matching sequence number (if MSEQNO(*@mref) != 0).
 * If either of these fails, -1 is returned and errno is set to EIO. If you get
 * this, but you still want to read the mft record (e.g. in order to correct
 * it), use ntfs_read_mft_record() directly.
 *
 * Note: Caller has to free *@mrec when finished.
 *
 * Note: We do not check if the mft record is flagged in use. The caller can
 *	 check if desired.
 */
int ntfs_read_file_record(const ntfs_volume *vol, const MFT_REF mref,
		MFT_RECORD **mrec, ATTR_RECORD **attr)
{
	MFT_RECORD *m;
	ATTR_RECORD *a;
	int err;

	if (!vol || !mrec) {
		errno = EINVAL;
		return -1;
	}
	m = *mrec;
	if (!m) {
		m = (MFT_RECORD*)malloc(vol->mft_record_size);
		if (!m)
			return -1;
	}
	if (ntfs_read_mft_record(vol, mref, m)) {
		err = errno;
		goto read_failed;
	}
	if (!is_file_record(m->magic))
		goto file_corrupt;
	if (MSEQNO(mref) && MSEQNO(mref) != le16_to_cpu(m->sequence_number))
		goto file_corrupt;
	a = (ATTR_RECORD*)((char*)m + le16_to_cpu(m->attrs_offset));
	if (p2n(a) < p2n(m) || (char*)a > (char*)m + vol->mft_record_size)
		goto file_corrupt;
	*mrec = m;
	if (attr)
		*attr = a;
	return 0;
file_corrupt:
	Dputs("ntfs_read_file_record(): file is corrupt.");
	err = EIO;
read_failed:
	if (m != *mrec)
		free(m);
	errno = err;
	return -1;
}