fs/ntfs/logfile.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * logfile.h - Defines for NTFS kernel journal ($LogFile) handling.  Part of
   4  *             the Linux-NTFS project.
   5  *
   6  * Copyright (c) 2000-2005 Anton Altaparmakov
   7  */
   8
   9 #ifndef _LINUX_NTFS_LOGFILE_H
  10 #define _LINUX_NTFS_LOGFILE_H
  11
  12 #ifdef NTFS_RW
  13
  14 #include <linux/fs.h>
  15
  16 #include "types.h"
  17 #include "endian.h"
  18 #include "layout.h"
  19
  20 /*
  21  * Journal ($LogFile) organization:
  22  *
  23  * Two restart areas present in the first two pages (restart pages, one restart
  24  * area in each page).  When the volume is dismounted they should be identical,
  25  * except for the update sequence array which usually has a different update
  26  * sequence number.
  27  *
  28  * These are followed by log records organized in pages headed by a log record
  29  * header going up to log file size.  Not all pages contain log records when a
  30  * volume is first formatted, but as the volume ages, all records will be used.
  31  * When the log file fills up, the records at the beginning are purged (by
  32  * modifying the oldest_lsn to a higher value presumably) and writing begins
  33  * at the beginning of the file.  Effectively, the log file is viewed as a
  34  * circular entity.
  35  *
  36  * NOTE: Windows NT, 2000, and XP all use log file version 1.1 but they accept
  37  * versions <= 1.x, including 0.-1.  (Yes, that is a minus one in there!)  We
  38  * probably only want to support 1.1 as this seems to be the current version
  39  * and we don't know how that differs from the older versions.  The only
  40  * exception is if the journal is clean as marked by the two restart pages
  41  * then it doesn't matter whether we are on an earlier version.  We can just
  42  * reinitialize the logfile and start again with version 1.1.
  43  */
  44
  45 /* Some $LogFile related constants. */
  46 #define MaxLogFileSize          0x100000000ULL
  47 #define DefaultLogPageSize      4096
  48 #define MinLogRecordPages       48
  49
  50 /*
  51  * Log file restart page header (begins the restart area).
  52  */
  53 typedef struct {
  54 /*Ofs*/
  55 /*  0   NTFS_RECORD; -- Unfolded here as gcc doesn't like unnamed structs. */
  56 /*  0*/ NTFS_RECORD_TYPE magic; /* The magic is "RSTR". */
  57 /*  4*/ le16 usa_ofs;           /* See NTFS_RECORD definition in layout.h.
  58                                    When creating, set this to be immediately
  59                                    after this header structure (without any
  60                                    alignment). */
  61 /*  6*/ le16 usa_count;         /* See NTFS_RECORD definition in layout.h. */
  62
  63 /*  8*/ leLSN chkdsk_lsn;       /* The last log file sequence number found by
  64                                    chkdsk.  Only used when the magic is changed
  65                                    to "CHKD".  Otherwise this is zero. */
  66 /* 16*/ le32 system_page_size;  /* Byte size of system pages when the log file
  67                                    was created, has to be >= 512 and a power of
  68                                    2.  Use this to calculate the required size
  69                                    of the usa (usa_count) and add it to usa_ofs.
  70                                    Then verify that the result is less than the
  71                                    value of the restart_area_offset. */
  72 /* 20*/ le32 log_page_size;     /* Byte size of log file pages, has to be >=
  73                                    512 and a power of 2.  The default is 4096
  74                                    and is used when the system page size is
  75                                    between 4096 and 8192.  Otherwise this is
  76                                    set to the system page size instead. */
  77 /* 24*/ le16 restart_area_offset;/* Byte offset from the start of this header to
  78                                    the RESTART_AREA.  Value has to be aligned
  79                                    to 8-byte boundary.  When creating, set this
  80                                    to be after the usa. */
  81 /* 26*/ sle16 minor_ver;        /* Log file minor version.  Only check if major
  82                                    version is 1. */
  83 /* 28*/ sle16 major_ver;        /* Log file major version.  We only support
  84                                    version 1.1. */
  85 /* sizeof() = 30 (0x1e) bytes */
  86 } __attribute__ ((__packed__)) RESTART_PAGE_HEADER;
  87
  88 /*
  89  * Constant for the log client indices meaning that there are no client records
  90  * in this particular client array.  Also inside the client records themselves,
  91  * this means that there are no client records preceding or following this one.
  92  */
  93 #define LOGFILE_NO_CLIENT       cpu_to_le16(0xffff)
  94 #define LOGFILE_NO_CLIENT_CPU   0xffff
  95
  96 /*
  97  * These are the so far known RESTART_AREA_* flags (16-bit) which contain
  98  * information about the log file in which they are present.
  99  */
 100 enum {
 101         RESTART_VOLUME_IS_CLEAN = cpu_to_le16(0x0002),
 102         RESTART_SPACE_FILLER    = cpu_to_le16(0xffff), /* gcc: Force enum bit width to 16. */
 103 } __attribute__ ((__packed__));
 104
 105 typedef le16 RESTART_AREA_FLAGS;
 106
 107 /*
 108  * Log file restart area record.  The offset of this record is found by adding
 109  * the offset of the RESTART_PAGE_HEADER to the restart_area_offset value found
 110  * in it.  See notes at restart_area_offset above.
 111  */
 112 typedef struct {
 113 /*Ofs*/
 114 /*  0*/ leLSN current_lsn;      /* The current, i.e. last LSN inside the log
 115                                    when the restart area was last written.
 116                                    This happens often but what is the interval?
 117                                    Is it just fixed time or is it every time a
 118                                    check point is written or somethine else?
 119                                    On create set to 0. */
 120 /*  8*/ le16 log_clients;       /* Number of log client records in the array of
 121                                    log client records which follows this
 122                                    restart area.  Must be 1.  */
 123 /* 10*/ le16 client_free_list;  /* The index of the first free log client record
 124                                    in the array of log client records.
 125                                    LOGFILE_NO_CLIENT means that there are no
 126                                    free log client records in the array.
 127                                    If != LOGFILE_NO_CLIENT, check that
 128                                    log_clients > client_free_list.  On Win2k
 129                                    and presumably earlier, on a clean volume
 130                                    this is != LOGFILE_NO_CLIENT, and it should
 131                                    be 0, i.e. the first (and only) client
 132                                    record is free and thus the logfile is
 133                                    closed and hence clean.  A dirty volume
 134                                    would have left the logfile open and hence
 135                                    this would be LOGFILE_NO_CLIENT.  On WinXP
 136                                    and presumably later, the logfile is always
 137                                    open, even on clean shutdown so this should
 138                                    always be LOGFILE_NO_CLIENT. */
 139 /* 12*/ le16 client_in_use_list;/* The index of the first in-use log client
 140                                    record in the array of log client records.
 141                                    LOGFILE_NO_CLIENT means that there are no
 142                                    in-use log client records in the array.  If
 143                                    != LOGFILE_NO_CLIENT check that log_clients
 144                                    > client_in_use_list.  On Win2k and
 145                                    presumably earlier, on a clean volume this
 146                                    is LOGFILE_NO_CLIENT, i.e. there are no
 147                                    client records in use and thus the logfile
 148                                    is closed and hence clean.  A dirty volume
 149                                    would have left the logfile open and hence
 150                                    this would be != LOGFILE_NO_CLIENT, and it
 151                                    should be 0, i.e. the first (and only)
 152                                    client record is in use.  On WinXP and
 153                                    presumably later, the logfile is always
 154                                    open, even on clean shutdown so this should
 155                                    always be 0. */
 156 /* 14*/ RESTART_AREA_FLAGS flags;/* Flags modifying LFS behaviour.  On Win2k
 157                                    and presumably earlier this is always 0.  On
 158                                    WinXP and presumably later, if the logfile
 159                                    was shutdown cleanly, the second bit,
 160                                    RESTART_VOLUME_IS_CLEAN, is set.  This bit
 161                                    is cleared when the volume is mounted by
 162                                    WinXP and set when the volume is dismounted,
 163                                    thus if the logfile is dirty, this bit is
 164                                    clear.  Thus we don't need to check the
 165                                    Windows version to determine if the logfile
 166                                    is clean.  Instead if the logfile is closed,
 167                                    we know it must be clean.  If it is open and
 168                                    this bit is set, we also know it must be
 169                                    clean.  If on the other hand the logfile is
 170                                    open and this bit is clear, we can be almost
 171                                    certain that the logfile is dirty. */
 172 /* 16*/ le32 seq_number_bits;   /* How many bits to use for the sequence
 173                                    number.  This is calculated as 67 - the
 174                                    number of bits required to store the logfile
 175                                    size in bytes and this can be used in with
 176                                    the specified file_size as a consistency
 177                                    check. */
 178 /* 20*/ le16 restart_area_length;/* Length of the restart area including the
 179                                    client array.  Following checks required if
 180                                    version matches.  Otherwise, skip them.
 181                                    restart_area_offset + restart_area_length
 182                                    has to be <= system_page_size.  Also,
 183                                    restart_area_length has to be >=
 184                                    client_array_offset + (log_clients *
 185                                    sizeof(log client record)). */
 186 /* 22*/ le16 client_array_offset;/* Offset from the start of this record to
 187                                    the first log client record if versions are
 188                                    matched.  When creating, set this to be
 189                                    after this restart area structure, aligned
 190                                    to 8-bytes boundary.  If the versions do not
 191                                    match, this is ignored and the offset is
 192                                    assumed to be (sizeof(RESTART_AREA) + 7) &
 193                                    ~7, i.e. rounded up to first 8-byte
 194                                    boundary.  Either way, client_array_offset
 195                                    has to be aligned to an 8-byte boundary.
 196                                    Also, restart_area_offset +
 197                                    client_array_offset has to be <= 510.
 198                                    Finally, client_array_offset + (log_clients
 199                                    * sizeof(log client record)) has to be <=
 200                                    system_page_size.  On Win2k and presumably
 201                                    earlier, this is 0x30, i.e. immediately
 202                                    following this record.  On WinXP and
 203                                    presumably later, this is 0x40, i.e. there
 204                                    are 16 extra bytes between this record and
 205                                    the client array.  This probably means that
 206                                    the RESTART_AREA record is actually bigger
 207                                    in WinXP and later. */
 208 /* 24*/ sle64 file_size;        /* Usable byte size of the log file.  If the
 209                                    restart_area_offset + the offset of the
 210                                    file_size are > 510 then corruption has
 211                                    occurred.  This is the very first check when
 212                                    starting with the restart_area as if it
 213                                    fails it means that some of the above values
 214                                    will be corrupted by the multi sector
 215                                    transfer protection.  The file_size has to
 216                                    be rounded down to be a multiple of the
 217                                    log_page_size in the RESTART_PAGE_HEADER and
 218                                    then it has to be at least big enough to
 219                                    store the two restart pages and 48 (0x30)
 220                                    log record pages. */
 221 /* 32*/ le32 last_lsn_data_length;/* Length of data of last LSN, not including
 222                                    the log record header.  On create set to
 223                                    0. */
 224 /* 36*/ le16 log_record_header_length;/* Byte size of the log record header.
 225                                    If the version matches then check that the
 226                                    value of log_record_header_length is a
 227                                    multiple of 8, i.e.
 228                                    (log_record_header_length + 7) & ~7 ==
 229                                    log_record_header_length.  When creating set
 230                                    it to sizeof(LOG_RECORD_HEADER), aligned to
 231                                    8 bytes. */
 232 /* 38*/ le16 log_page_data_offset;/* Offset to the start of data in a log record
 233                                    page.  Must be a multiple of 8.  On create
 234                                    set it to immediately after the update
 235                                    sequence array of the log record page. */
 236 /* 40*/ le32 restart_log_open_count;/* A counter that gets incremented every
 237                                    time the logfile is restarted which happens
 238                                    at mount time when the logfile is opened.
 239                                    When creating set to a random value.  Win2k
 240                                    sets it to the low 32 bits of the current
 241                                    system time in NTFS format (see time.h). */
 242 /* 44*/ le32 reserved;          /* Reserved/alignment to 8-byte boundary. */
 243 /* sizeof() = 48 (0x30) bytes */
 244 } __attribute__ ((__packed__)) RESTART_AREA;
 245
 246 /*
 247  * Log client record.  The offset of this record is found by adding the offset
 248  * of the RESTART_AREA to the client_array_offset value found in it.
 249  */
 250 typedef struct {
 251 /*Ofs*/
 252 /*  0*/ leLSN oldest_lsn;       /* Oldest LSN needed by this client.  On create
 253                                    set to 0. */
 254 /*  8*/ leLSN client_restart_lsn;/* LSN at which this client needs to restart
 255                                    the volume, i.e. the current position within
 256                                    the log file.  At present, if clean this
 257                                    should = current_lsn in restart area but it
 258                                    probably also = current_lsn when dirty most
 259                                    of the time.  At create set to 0. */
 260 /* 16*/ le16 prev_client;       /* The offset to the previous log client record
 261                                    in the array of log client records.
 262                                    LOGFILE_NO_CLIENT means there is no previous
 263                                    client record, i.e. this is the first one.
 264                                    This is always LOGFILE_NO_CLIENT. */
 265 /* 18*/ le16 next_client;       /* The offset to the next log client record in
 266                                    the array of log client records.
 267                                    LOGFILE_NO_CLIENT means there are no next
 268                                    client records, i.e. this is the last one.
 269                                    This is always LOGFILE_NO_CLIENT. */
 270 /* 20*/ le16 seq_number;        /* On Win2k and presumably earlier, this is set
 271                                    to zero every time the logfile is restarted
 272                                    and it is incremented when the logfile is
 273                                    closed at dismount time.  Thus it is 0 when
 274                                    dirty and 1 when clean.  On WinXP and
 275                                    presumably later, this is always 0. */
 276 /* 22*/ u8 reserved[6];         /* Reserved/alignment. */
 277 /* 28*/ le32 client_name_length;/* Length of client name in bytes.  Should
 278                                    always be 8. */
 279 /* 32*/ ntfschar client_name[64];/* Name of the client in Unicode.  Should
 280                                    always be "NTFS" with the remaining bytes
 281                                    set to 0. */
 282 /* sizeof() = 160 (0xa0) bytes */
 283 } __attribute__ ((__packed__)) LOG_CLIENT_RECORD;
 284
 285 extern bool ntfs_check_logfile(struct inode *log_vi,
 286                 RESTART_PAGE_HEADER **rp);
 287
 288 extern bool ntfs_is_logfile_clean(struct inode *log_vi,
 289                 const RESTART_PAGE_HEADER *rp);
 290
 291 extern bool ntfs_empty_logfile(struct inode *log_vi);
 292
 293 #endif /* NTFS_RW */
 294
 295 #endif /* _LINUX_NTFS_LOGFILE_H */