The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/fs/ntfs/usnjrnl.h

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    1 /*
    2  * usnjrnl.h - Defines for NTFS kernel transaction log ($UsnJrnl) handling.
    3  *             Part of the Linux-NTFS project.
    4  *
    5  * Copyright (c) 2005 Anton Altaparmakov
    6  *
    7  * This program/include file is free software; you can redistribute it and/or
    8  * modify it under the terms of the GNU General Public License as published
    9  * by the Free Software Foundation; either version 2 of the License, or
   10  * (at your option) any later version.
   11  *
   12  * This program/include file is distributed in the hope that it will be
   13  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
   14  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   15  * GNU General Public License for more details.
   16  *
   17  * You should have received a copy of the GNU General Public License
   18  * along with this program (in the main directory of the Linux-NTFS
   19  * distribution in the file COPYING); if not, write to the Free Software
   20  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   21  */
   22 
   23 #ifndef _LINUX_NTFS_USNJRNL_H
   24 #define _LINUX_NTFS_USNJRNL_H
   25 
   26 #ifdef NTFS_RW
   27 
   28 #include "types.h"
   29 #include "endian.h"
   30 #include "layout.h"
   31 #include "volume.h"
   32 
   33 /*
   34  * Transaction log ($UsnJrnl) organization:
   35  *
   36  * The transaction log records whenever a file is modified in any way.  So for
   37  * example it will record that file "blah" was written to at a particular time
   38  * but not what was written.  If will record that a file was deleted or
   39  * created, that a file was truncated, etc.  See below for all the reason
   40  * codes used.
   41  *
   42  * The transaction log is in the $Extend directory which is in the root
   43  * directory of each volume.  If it is not present it means transaction
   44  * logging is disabled.  If it is present it means transaction logging is
   45  * either enabled or in the process of being disabled in which case we can
   46  * ignore it as it will go away as soon as Windows gets its hands on it.
   47  *
   48  * To determine whether the transaction logging is enabled or in the process
   49  * of being disabled, need to check the volume flags in the
   50  * $VOLUME_INFORMATION attribute in the $Volume system file (which is present
   51  * in the root directory and has a fixed mft record number, see layout.h).
   52  * If the flag VOLUME_DELETE_USN_UNDERWAY is set it means the transaction log
   53  * is in the process of being disabled and if this flag is clear it means the
   54  * transaction log is enabled.
   55  *
   56  * The transaction log consists of two parts; the $DATA/$Max attribute as well
   57  * as the $DATA/$J attribute.  $Max is a header describing the transaction
   58  * log whilst $J is the transaction log data itself as a sequence of variable
   59  * sized USN_RECORDs (see below for all the structures).
   60  *
   61  * We do not care about transaction logging at this point in time but we still
   62  * need to let windows know that the transaction log is out of date.  To do
   63  * this we need to stamp the transaction log.  This involves setting the
   64  * lowest_valid_usn field in the $DATA/$Max attribute to the usn to be used
   65  * for the next added USN_RECORD to the $DATA/$J attribute as well as
   66  * generating a new journal_id in $DATA/$Max.
   67  *
   68  * The journal_id is as of the current version (2.0) of the transaction log
   69  * simply the 64-bit timestamp of when the journal was either created or last
   70  * stamped.
   71  *
   72  * To determine the next usn there are two ways.  The first is to parse
   73  * $DATA/$J and to find the last USN_RECORD in it and to add its record_length
   74  * to its usn (which is the byte offset in the $DATA/$J attribute).  The
   75  * second is simply to take the data size of the attribute.  Since the usns
   76  * are simply byte offsets into $DATA/$J, this is exactly the next usn.  For
   77  * obvious reasons we use the second method as it is much simpler and faster.
   78  *
   79  * As an aside, note that to actually disable the transaction log, one would
   80  * need to set the VOLUME_DELETE_USN_UNDERWAY flag (see above), then go
   81  * through all the mft records on the volume and set the usn field in their
   82  * $STANDARD_INFORMATION attribute to zero.  Once that is done, one would need
   83  * to delete the transaction log file, i.e. \$Extent\$UsnJrnl, and finally,
   84  * one would need to clear the VOLUME_DELETE_USN_UNDERWAY flag.
   85  *
   86  * Note that if a volume is unmounted whilst the transaction log is being
   87  * disabled, the process will continue the next time the volume is mounted.
   88  * This is why we can safely mount read-write when we see a transaction log
   89  * in the process of being deleted.
   90  */
   91 
   92 /* Some $UsnJrnl related constants. */
   93 #define UsnJrnlMajorVer         2
   94 #define UsnJrnlMinorVer         0
   95 
   96 /*
   97  * $DATA/$Max attribute.  This is (always?) resident and has a fixed size of
   98  * 32 bytes.  It contains the header describing the transaction log.
   99  */
  100 typedef struct {
  101 /*Ofs*/
  102 /*   0*/sle64 maximum_size;     /* The maximum on-disk size of the $DATA/$J
  103                                    attribute. */
  104 /*   8*/sle64 allocation_delta; /* Number of bytes by which to increase the
  105                                    size of the $DATA/$J attribute. */
  106 /*0x10*/sle64 journal_id;       /* Current id of the transaction log. */
  107 /*0x18*/leUSN lowest_valid_usn; /* Lowest valid usn in $DATA/$J for the
  108                                    current journal_id. */
  109 /* sizeof() = 32 (0x20) bytes */
  110 } __attribute__ ((__packed__)) USN_HEADER;
  111 
  112 /*
  113  * Reason flags (32-bit).  Cumulative flags describing the change(s) to the
  114  * file since it was last opened.  I think the names speak for themselves but
  115  * if you disagree check out the descriptions in the Linux NTFS project NTFS
  116  * documentation: http://www.linux-ntfs.org/
  117  */
  118 enum {
  119         USN_REASON_DATA_OVERWRITE       = cpu_to_le32(0x00000001),
  120         USN_REASON_DATA_EXTEND          = cpu_to_le32(0x00000002),
  121         USN_REASON_DATA_TRUNCATION      = cpu_to_le32(0x00000004),
  122         USN_REASON_NAMED_DATA_OVERWRITE = cpu_to_le32(0x00000010),
  123         USN_REASON_NAMED_DATA_EXTEND    = cpu_to_le32(0x00000020),
  124         USN_REASON_NAMED_DATA_TRUNCATION= cpu_to_le32(0x00000040),
  125         USN_REASON_FILE_CREATE          = cpu_to_le32(0x00000100),
  126         USN_REASON_FILE_DELETE          = cpu_to_le32(0x00000200),
  127         USN_REASON_EA_CHANGE            = cpu_to_le32(0x00000400),
  128         USN_REASON_SECURITY_CHANGE      = cpu_to_le32(0x00000800),
  129         USN_REASON_RENAME_OLD_NAME      = cpu_to_le32(0x00001000),
  130         USN_REASON_RENAME_NEW_NAME      = cpu_to_le32(0x00002000),
  131         USN_REASON_INDEXABLE_CHANGE     = cpu_to_le32(0x00004000),
  132         USN_REASON_BASIC_INFO_CHANGE    = cpu_to_le32(0x00008000),
  133         USN_REASON_HARD_LINK_CHANGE     = cpu_to_le32(0x00010000),
  134         USN_REASON_COMPRESSION_CHANGE   = cpu_to_le32(0x00020000),
  135         USN_REASON_ENCRYPTION_CHANGE    = cpu_to_le32(0x00040000),
  136         USN_REASON_OBJECT_ID_CHANGE     = cpu_to_le32(0x00080000),
  137         USN_REASON_REPARSE_POINT_CHANGE = cpu_to_le32(0x00100000),
  138         USN_REASON_STREAM_CHANGE        = cpu_to_le32(0x00200000),
  139         USN_REASON_CLOSE                = cpu_to_le32(0x80000000),
  140 };
  141 
  142 typedef le32 USN_REASON_FLAGS;
  143 
  144 /*
  145  * Source info flags (32-bit).  Information about the source of the change(s)
  146  * to the file.  For detailed descriptions of what these mean, see the Linux
  147  * NTFS project NTFS documentation:
  148  *      http://www.linux-ntfs.org/
  149  */
  150 enum {
  151         USN_SOURCE_DATA_MANAGEMENT        = cpu_to_le32(0x00000001),
  152         USN_SOURCE_AUXILIARY_DATA         = cpu_to_le32(0x00000002),
  153         USN_SOURCE_REPLICATION_MANAGEMENT = cpu_to_le32(0x00000004),
  154 };
  155 
  156 typedef le32 USN_SOURCE_INFO_FLAGS;
  157 
  158 /*
  159  * $DATA/$J attribute.  This is always non-resident, is marked as sparse, and
  160  * is of variabled size.  It consists of a sequence of variable size
  161  * USN_RECORDS.  The minimum allocated_size is allocation_delta as
  162  * specified in $DATA/$Max.  When the maximum_size specified in $DATA/$Max is
  163  * exceeded by more than allocation_delta bytes, allocation_delta bytes are
  164  * allocated and appended to the $DATA/$J attribute and an equal number of
  165  * bytes at the beginning of the attribute are freed and made sparse.  Note the
  166  * making sparse only happens at volume checkpoints and hence the actual
  167  * $DATA/$J size can exceed maximum_size + allocation_delta temporarily.
  168  */
  169 typedef struct {
  170 /*Ofs*/
  171 /*   0*/le32 length;            /* Byte size of this record (8-byte
  172                                    aligned). */
  173 /*   4*/le16 major_ver;         /* Major version of the transaction log used
  174                                    for this record. */
  175 /*   6*/le16 minor_ver;         /* Minor version of the transaction log used
  176                                    for this record. */
  177 /*   8*/leMFT_REF mft_reference;/* The mft reference of the file (or
  178                                    directory) described by this record. */
  179 /*0x10*/leMFT_REF parent_directory;/* The mft reference of the parent
  180                                    directory of the file described by this
  181                                    record. */
  182 /*0x18*/leUSN usn;              /* The usn of this record.  Equals the offset
  183                                    within the $DATA/$J attribute. */
  184 /*0x20*/sle64 time;             /* Time when this record was created. */
  185 /*0x28*/USN_REASON_FLAGS reason;/* Reason flags (see above). */
  186 /*0x2c*/USN_SOURCE_INFO_FLAGS source_info;/* Source info flags (see above). */
  187 /*0x30*/le32 security_id;       /* File security_id copied from
  188                                    $STANDARD_INFORMATION. */
  189 /*0x34*/FILE_ATTR_FLAGS file_attributes;        /* File attributes copied from
  190                                    $STANDARD_INFORMATION or $FILE_NAME (not
  191                                    sure which). */
  192 /*0x38*/le16 file_name_size;    /* Size of the file name in bytes. */
  193 /*0x3a*/le16 file_name_offset;  /* Offset to the file name in bytes from the
  194                                    start of this record. */
  195 /*0x3c*/ntfschar file_name[0];  /* Use when creating only.  When reading use
  196                                    file_name_offset to determine the location
  197                                    of the name. */
  198 /* sizeof() = 60 (0x3c) bytes */
  199 } __attribute__ ((__packed__)) USN_RECORD;
  200 
  201 extern bool ntfs_stamp_usnjrnl(ntfs_volume *vol);
  202 
  203 #endif /* NTFS_RW */
  204 
  205 #endif /* _LINUX_NTFS_USNJRNL_H */

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