FreeBSD/Linux Kernel Cross Reference
sys/fs/ntfs/usnjrnl.h

     /*
      * usnjrnl.h - Defines for NTFS kernel transaction log ($UsnJrnl) handling.
      *             Part of the Linux-NTFS project.
      *
      * Copyright (c) 2005 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
     */
    
    #ifndef _LINUX_NTFS_USNJRNL_H
    #define _LINUX_NTFS_USNJRNL_H
    
    #ifdef NTFS_RW
    
    #include "types.h"
    #include "endian.h"
    #include "layout.h"
    #include "volume.h"
    
    /*
     * Transaction log ($UsnJrnl) organization:
     *
     * The transaction log records whenever a file is modified in any way.  So for
     * example it will record that file "blah" was written to at a particular time
     * but not what was written.  If will record that a file was deleted or
     * created, that a file was truncated, etc.  See below for all the reason
     * codes used.
     *
     * The transaction log is in the $Extend directory which is in the root
     * directory of each volume.  If it is not present it means transaction
     * logging is disabled.  If it is present it means transaction logging is
     * either enabled or in the process of being disabled in which case we can
     * ignore it as it will go away as soon as Windows gets its hands on it.
     *
     * To determine whether the transaction logging is enabled or in the process
     * of being disabled, need to check the volume flags in the
     * $VOLUME_INFORMATION attribute in the $Volume system file (which is present
     * in the root directory and has a fixed mft record number, see layout.h).
     * If the flag VOLUME_DELETE_USN_UNDERWAY is set it means the transaction log
     * is in the process of being disabled and if this flag is clear it means the
     * transaction log is enabled.
     *
     * The transaction log consists of two parts; the $DATA/$Max attribute as well
     * as the $DATA/$J attribute.  $Max is a header describing the transaction
     * log whilst $J is the transaction log data itself as a sequence of variable
     * sized USN_RECORDs (see below for all the structures).
     *
     * We do not care about transaction logging at this point in time but we still
     * need to let windows know that the transaction log is out of date.  To do
     * this we need to stamp the transaction log.  This involves setting the
     * lowest_valid_usn field in the $DATA/$Max attribute to the usn to be used
     * for the next added USN_RECORD to the $DATA/$J attribute as well as
     * generating a new journal_id in $DATA/$Max.
     *
     * The journal_id is as of the current version (2.0) of the transaction log
     * simply the 64-bit timestamp of when the journal was either created or last
     * stamped.
     *
     * To determine the next usn there are two ways.  The first is to parse
     * $DATA/$J and to find the last USN_RECORD in it and to add its record_length
     * to its usn (which is the byte offset in the $DATA/$J attribute).  The
     * second is simply to take the data size of the attribute.  Since the usns
     * are simply byte offsets into $DATA/$J, this is exactly the next usn.  For
     * obvious reasons we use the second method as it is much simpler and faster.
     *
     * As an aside, note that to actually disable the transaction log, one would
     * need to set the VOLUME_DELETE_USN_UNDERWAY flag (see above), then go
     * through all the mft records on the volume and set the usn field in their
     * $STANDARD_INFORMATION attribute to zero.  Once that is done, one would need
     * to delete the transaction log file, i.e. \$Extent\$UsnJrnl, and finally,
     * one would need to clear the VOLUME_DELETE_USN_UNDERWAY flag.
     *
     * Note that if a volume is unmounted whilst the transaction log is being
     * disabled, the process will continue the next time the volume is mounted.
     * This is why we can safely mount read-write when we see a transaction log
     * in the process of being deleted.
     */
    
    /* Some $UsnJrnl related constants. */
    #define UsnJrnlMajorVer         2
    #define UsnJrnlMinorVer         0
    
    /*
     * $DATA/$Max attribute.  This is (always?) resident and has a fixed size of
     * 32 bytes.  It contains the header describing the transaction log.
     */
   typedef struct {
   /*Ofs*/
   /*   0*/sle64 maximum_size;     /* The maximum on-disk size of the $DATA/$J
                                      attribute. */
   /*   8*/sle64 allocation_delta; /* Number of bytes by which to increase the
                                      size of the $DATA/$J attribute. */
   /*0x10*/sle64 journal_id;       /* Current id of the transaction log. */
   /*0x18*/leUSN lowest_valid_usn; /* Lowest valid usn in $DATA/$J for the
                                      current journal_id. */
   /* sizeof() = 32 (0x20) bytes */
   } __attribute__ ((__packed__)) USN_HEADER;
   
   /*
    * Reason flags (32-bit).  Cumulative flags describing the change(s) to the
    * file since it was last opened.  I think the names speak for themselves but
    * if you disagree check out the descriptions in the Linux NTFS project NTFS
    * documentation: http://www.linux-ntfs.org/
    */
   enum {
           USN_REASON_DATA_OVERWRITE       = cpu_to_le32(0x00000001),
           USN_REASON_DATA_EXTEND          = cpu_to_le32(0x00000002),
           USN_REASON_DATA_TRUNCATION      = cpu_to_le32(0x00000004),
           USN_REASON_NAMED_DATA_OVERWRITE = cpu_to_le32(0x00000010),
           USN_REASON_NAMED_DATA_EXTEND    = cpu_to_le32(0x00000020),
           USN_REASON_NAMED_DATA_TRUNCATION= cpu_to_le32(0x00000040),
           USN_REASON_FILE_CREATE          = cpu_to_le32(0x00000100),
           USN_REASON_FILE_DELETE          = cpu_to_le32(0x00000200),
           USN_REASON_EA_CHANGE            = cpu_to_le32(0x00000400),
           USN_REASON_SECURITY_CHANGE      = cpu_to_le32(0x00000800),
           USN_REASON_RENAME_OLD_NAME      = cpu_to_le32(0x00001000),
           USN_REASON_RENAME_NEW_NAME      = cpu_to_le32(0x00002000),
           USN_REASON_INDEXABLE_CHANGE     = cpu_to_le32(0x00004000),
           USN_REASON_BASIC_INFO_CHANGE    = cpu_to_le32(0x00008000),
           USN_REASON_HARD_LINK_CHANGE     = cpu_to_le32(0x00010000),
           USN_REASON_COMPRESSION_CHANGE   = cpu_to_le32(0x00020000),
           USN_REASON_ENCRYPTION_CHANGE    = cpu_to_le32(0x00040000),
           USN_REASON_OBJECT_ID_CHANGE     = cpu_to_le32(0x00080000),
           USN_REASON_REPARSE_POINT_CHANGE = cpu_to_le32(0x00100000),
           USN_REASON_STREAM_CHANGE        = cpu_to_le32(0x00200000),
           USN_REASON_CLOSE                = cpu_to_le32(0x80000000),
   };
   
   typedef le32 USN_REASON_FLAGS;
   
   /*
    * Source info flags (32-bit).  Information about the source of the change(s)
    * to the file.  For detailed descriptions of what these mean, see the Linux
    * NTFS project NTFS documentation:
    *      http://www.linux-ntfs.org/
    */
   enum {
           USN_SOURCE_DATA_MANAGEMENT        = cpu_to_le32(0x00000001),
           USN_SOURCE_AUXILIARY_DATA         = cpu_to_le32(0x00000002),
           USN_SOURCE_REPLICATION_MANAGEMENT = cpu_to_le32(0x00000004),
   };
   
   typedef le32 USN_SOURCE_INFO_FLAGS;
   
   /*
    * $DATA/$J attribute.  This is always non-resident, is marked as sparse, and
    * is of variabled size.  It consists of a sequence of variable size
    * USN_RECORDS.  The minimum allocated_size is allocation_delta as
    * specified in $DATA/$Max.  When the maximum_size specified in $DATA/$Max is
    * exceeded by more than allocation_delta bytes, allocation_delta bytes are
    * allocated and appended to the $DATA/$J attribute and an equal number of
    * bytes at the beginning of the attribute are freed and made sparse.  Note the
    * making sparse only happens at volume checkpoints and hence the actual
    * $DATA/$J size can exceed maximum_size + allocation_delta temporarily.
    */
   typedef struct {
   /*Ofs*/
   /*   0*/le32 length;            /* Byte size of this record (8-byte
                                      aligned). */
   /*   4*/le16 major_ver;         /* Major version of the transaction log used
                                      for this record. */
   /*   6*/le16 minor_ver;         /* Minor version of the transaction log used
                                      for this record. */
   /*   8*/leMFT_REF mft_reference;/* The mft reference of the file (or
                                      directory) described by this record. */
   /*0x10*/leMFT_REF parent_directory;/* The mft reference of the parent
                                      directory of the file described by this
                                      record. */
   /*0x18*/leUSN usn;              /* The usn of this record.  Equals the offset
                                      within the $DATA/$J attribute. */
   /*0x20*/sle64 time;             /* Time when this record was created. */
   /*0x28*/USN_REASON_FLAGS reason;/* Reason flags (see above). */
   /*0x2c*/USN_SOURCE_INFO_FLAGS source_info;/* Source info flags (see above). */
   /*0x30*/le32 security_id;       /* File security_id copied from
                                      $STANDARD_INFORMATION. */
   /*0x34*/FILE_ATTR_FLAGS file_attributes;        /* File attributes copied from
                                      $STANDARD_INFORMATION or $FILE_NAME (not
                                      sure which). */
   /*0x38*/le16 file_name_size;    /* Size of the file name in bytes. */
   /*0x3a*/le16 file_name_offset;  /* Offset to the file name in bytes from the
                                      start of this record. */
   /*0x3c*/ntfschar file_name[0];  /* Use when creating only.  When reading use
                                      file_name_offset to determine the location
                                      of the name. */
   /* sizeof() = 60 (0x3c) bytes */
   } __attribute__ ((__packed__)) USN_RECORD;
   
   extern bool ntfs_stamp_usnjrnl(ntfs_volume *vol);
   
   #endif /* NTFS_RW */
   
   #endif /* _LINUX_NTFS_USNJRNL_H */

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