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Linux/fs/ntfs/usnjrnl.h

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 48  * need to let windows know that the transaction log is out of date.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

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