xref: /linux/fs/ntfs/logfile.h (revision cdd4dc3aebeab43a72ce0bc2b5bab6f0a80b97a5)

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Defines for NTFS kernel journal (LogFile) handling.
 *
 * Copyright (c) 2000-2005 Anton Altaparmakov
 */

#ifndef _LINUX_NTFS_LOGFILE_H
#define _LINUX_NTFS_LOGFILE_H

#include "layout.h"

/*
 * Journal (LogFile) organization:
 *
 * Two restart areas present in the first two pages (restart pages, one restart
 * area in each page).  When the volume is dismounted they should be identical,
 * except for the update sequence array which usually has a different update
 * sequence number.
 *
 * These are followed by log records organized in pages headed by a log record
 * header going up to log file size.  Not all pages contain log records when a
 * volume is first formatted, but as the volume ages, all records will be used.
 * When the log file fills up, the records at the beginning are purged (by
 * modifying the oldest_lsn to a higher value presumably) and writing begins
 * at the beginning of the file.  Effectively, the log file is viewed as a
 * circular entity.
 *
 * NOTE: Windows NT, 2000, and XP all use log file version 1.1 but they accept
 * versions <= 1.x, including 0.-1.  (Yes, that is a minus one in there!)  We
 * probably only want to support 1.1 as this seems to be the current version
 * and we don't know how that differs from the older versions.  The only
 * exception is if the journal is clean as marked by the two restart pages
 * then it doesn't matter whether we are on an earlier version.  We can just
 * reinitialize the logfile and start again with version 1.1.
 */

/* Some LogFile related constants. */
#define MaxLogFileSize		0x100000000ULL
#define DefaultLogPageSize	4096
#define MinLogRecordPages	48

/*
 * Log file restart page header (begins the restart area).
 *
 * @magic: The magic is "RSTR".
 * @usa_ofs: See ntfs_record struct definition in layout.h.  When creating,
 *   set this to be immediately after this header structure (without any
 *   alignment).
 * @usa_count: See ntfs_record struct definition in layout.h.
 * @chkdsk_lsn: The last log file sequence number found by chkdsk.  Only
 *   used when the magic is changed to "CHKD".  Otherwise this is zero.
 * @system_page_size: Byte size of system pages when the log file was
 *   created, has to be >= 512 and a power of 2.  Use this to calculate
 *   the required size of the usa (usa_count) and add it to usa_ofs. Then
 *   verify that the result is less than the value of
 *   the restart_area_offset.
 * @log_page_size: Byte size of log file pages, has to be >= 512 and
 *   a power of 2.  The default is 4096 and is used when the system page
 *   size is between 4096 and 8192.  Otherwise this is set to the system
 *   page size instead.
 * @restart_area_offset: Byte offset from the start of this header to
 *   the RESTART_AREA. Value has to be aligned to 8-byte boundary.  When
 *   creating, set this to be after the usa.
 * @minor_ver: Log file minor version.  Only check if major version is 1.
 * @major_ver: Log file major version.  We only support version 1.1.
 */
struct restart_page_header {
	__le32 magic;
	__le16 usa_ofs;
	__le16 usa_count;
	__le64 chkdsk_lsn;
	__le32 system_page_size;
	__le32 log_page_size;
	__le16 restart_area_offset;
	__le16 minor_ver;
	__le16 major_ver;
} __packed;

/*
 * Constant for the log client indices meaning that there are no client records
 * in this particular client array.  Also inside the client records themselves,
 * this means that there are no client records preceding or following this one.
 */
#define LOGFILE_NO_CLIENT	cpu_to_le16(0xffff)
#define LOGFILE_NO_CLIENT_CPU	0xffff

/*
 * These are the so far known RESTART_AREA_* flags (16-bit) which contain
 * information about the log file in which they are present.
 * gcc: Force enum bit width to 16.
 */
enum {
	RESTART_VOLUME_IS_CLEAN	= cpu_to_le16(0x0002),
	RESTART_SPACE_FILLER	= cpu_to_le16(0xffff),
} __packed;

/*
 * Log file restart area record.  The offset of this record is found by adding
 * the offset of the RESTART_PAGE_HEADER to the restart_area_offset value found
 * in it.  See notes at restart_area_offset above.
 *
 * @current_lsn: The current, i.e. last LSN inside the log when
 *   the restart area was last written.  This happens often but what is
 *   the interval?  Is it just fixed time or is it every time a check point
 *   is written or somethine else?  On create set to 0.
 * @log_clients: Number of log client records in the array of log client
 *   records which follows this restart area.  Must be 1.
 * @client_free_list: The index of the first free log client record in
 *   the array of log client records.  LOGFILE_NO_CLIENT means that there
 *   are no free log client records in the array.  If != LOGFILE_NO_CLIENT,
 *   check that log_clients > client_free_list.  On Win2k and presumably
 *   earlier, on a clean volume this is != LOGFILE_NO_CLIENT, and it should
 *   be 0, i.e. the first (and only) client record is free and thus
 *   the logfile is closed and hence clean.  A dirty volume would have left
 *   the logfile open and hence this would be LOGFILE_NO_CLIENT.  On WinXP
 *   and presumably later, the logfile is always open, even on clean
 *   shutdown so this should always be LOGFILE_NO_CLIENT.
 * @client_in_use_list: The index of the first in-use log client record in
 *   the array of log client records.  LOGFILE_NO_CLIENT means that there
 *   are no in-use log client records in the array.
 *   If != LOGFILE_NO_CLIENT check that log_clients > client_in_use_list.
 *   On Win2k and presumably earlier, on a clean volume this is
 *   LOGFILE_NO_CLIENT, i.e. there are no client records in use and thus
 *   the logfile is closed and hence clean.  A dirty volume would have left
 *   the logfile open and hence this would be != LOGFILE_NO_CLIENT, and it
 *   should be 0, i.e. the first (and only) client record is in use.  On
 *   WinXP and presumably later, the logfile is always open, even on clean
 *   shutdown so this should always be 0.
 * @flags: Flags modifying LFS behaviour.  On Win2k and presumably earlier
 *   this is always 0.  On WinXP and presumably later, if the logfile was
 *   shutdown cleanly, the second bit, RESTART_VOLUME_IS_CLEAN, is set.
 *   This bit is cleared when the volume is mounted by WinXP and set when
 *   the volume is dismounted, thus if the logfile is dirty, this bit is
 *   clear.  Thus we don't need to check the Windows version to determine
 *   if the logfile is clean.  Instead if the logfile is closed, we know
 *   it must be clean.  If it is open and this bit is set, we also know
 *   it must be clean.  If on the other hand the logfile is open and this
 *   bit is clear, we can be almost certain that the logfile is dirty.
 * @seq_number_bits: How many bits to use for the sequence number.  This
 *   is calculated as 67 - the number of bits required to store the logfile
 *   size in bytes and this can be used in with the specified file_size as
 *   a consistency check.
 * @restart_area_length: Length of the restart area including the client
 *   array.  Following checks required if version matches.  Otherwise,
 *   skip them.  restart_area_offset + restart_area_length has to be
 *   <= system_page_size.  Also, restart_area_length has to be >=
 *   client_array_offset + (log_clients * sizeof(log client record)).
 * @client_array_offset: Offset from the start of this record to the first
 *   log client record if versions are matched.  When creating, set this
 *   to be after this restart area structure, aligned to 8-bytes boundary.
 *   If the versions do not match, this is ignored and the offset is
 *   assumed to be (sizeof(RESTART_AREA) + 7) &  ~7, i.e. rounded up to
 *   first 8-byte boundary.  Either way, client_array_offset has to be
 *   aligned to an 8-byte boundary.  Also, restart_area_offset +
 *   client_array_offset has to be <= 510.  Finally, client_array_offset +
 *   (log_clients * sizeof(log client record)) has to be <= system_page_size.
 *   On Win2k and presumably earlier, this is 0x30, i.e. immediately
 *   following this record.  On WinXP and presumably later, this is 0x40,
 *   i.e. there are 16 extra bytes between this record and the client
 *   array.  This probably means that the RESTART_AREA record is actually
 *   bigger in WinXP and later.
 * @file_size: Usable byte size of the log file.
 *   If the restart_area_offset + the offset of the file_size are > 510
 *   then corruption has occurred.  This is the very first check when
 *   starting with the restart_area as if it fails it means that some of
 *   the above values will be corrupted by the multi sector transfer
 *   protection.  The file_size has to be rounded down to be a multiple
 *   of the log_page_size in the RESTART_PAGE_HEADER and then it has to be
 *   at least big enough to store the two restart pages and 48 (0x30) log
 *   record pages.
 * @last_lsn_data_length: Length of data of last LSN, not including the log
 *   record header.  On create set to 0.
 * @log_record_header_length: Byte size of the log record header.  If the
 *   version matches then check that the value of log_record_header_length
 *   is a multiple of 8, i.e. (log_record_header_length + 7) & ~7 ==
 *   log_record_header_length.  When creating set it to
 *   sizeof(LOG_RECORD_HEADER), aligned to 8 bytes.
 * @log_page_data_offset: Offset to the start of data in a log record page.
 *   Must be a multiple of 8.  On create set it to immediately after
 *   the update sequence array of the log record page.
 * @restart_log_open_count: A counter that gets incremented every time
 *   the logfile is restarted which happens at mount time when the logfile
 *   is opened. When creating set to a random value.  Win2k sets it to
 *   the low 32 bits of the current system time in NTFS format (see time.h).
 * @reserved: Reserved/alignment to 8-byte boundary.
 */
struct restart_area {
	__le64 current_lsn;
	__le16 log_clients;
	__le16 client_free_list;
	__le16 client_in_use_list;
	__le16 flags;
	__le32 seq_number_bits;
	__le16 restart_area_length;
	__le16 client_array_offset;
	__le64 file_size;
	__le32 last_lsn_data_length;
	__le16 log_record_header_length;
	__le16 log_page_data_offset;
	__le32 restart_log_open_count;
	__le32 reserved;
} __packed;

/*
 * Log client record.  The offset of this record is found by adding the offset
 * of the RESTART_AREA to the client_array_offset value found in it.
 *
 * @oldest_lsn: Oldest LSN needed by this client.  On create set to 0.
 * @client_restart_lsn: LSN at which this client needs to restart
 *   the volume, i.e. the current position within the log file.
 *   At present, if clean this should = current_lsn in restart area but it
 *   probably also = current_lsn when dirty most of the time.
 *   At create set to 0.
 * @prev_client: The offset to the previous log client record in the array
 *   of log client records.  LOGFILE_NO_CLIENT means there is no previous
 *   client record, i.e. this is the first one.  This is always
 *   LOGFILE_NO_CLIENT.
 * @next_client: The offset to the next log client record in the array of
 *   log client records.  LOGFILE_NO_CLIENT means there are no next client
 *   records, i.e. this is the last one.  This is always LOGFILE_NO_CLIENT.
 * @seq_number: On Win2k and presumably earlier, this is set to zero every
 *   time the logfile is restarted and it is incremented when the logfile
 *   is closed at dismount time.  Thus it is 0 when dirty and 1 when clean.
 *   On WinXP and presumably later, this is always 0.
 * @reserved[6]: Reserved/alignment.
 * @client_name_length: Length of client name in bytes.  Should always be 8.
 * @client_name[64]: Name of the client in Unicode. Should always be "NTFS"
 *   with the remaining bytes set to 0.
 */
struct log_client_record {
	__le64 oldest_lsn;
	__le64 client_restart_lsn;
	__le16 prev_client;
	__le16 next_client;
	__le16 seq_number;
	u8 reserved[6];
	__le32 client_name_length;
	__le16 client_name[64];
} __packed;

bool ntfs_check_logfile(struct inode *log_vi,
		struct restart_page_header **rp);
bool ntfs_empty_logfile(struct inode *log_vi);
#endif /* _LINUX_NTFS_LOGFILE_H */