NTFS: Add MFT_RECORD_OLD as a copy of MFT_RECORD in fs/ntfs/layout.h

      and change MFT_RECORD to contain the NTFS 3.1+ specific fields.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

fs/ntfs/ChangeLog

@@ -45,6 +45,8 @@ ToDo/Notes:
 	  fs/ntfs/logfile.c::ntfs_empty_logfile() to using it.
 	- Remove unnecessary casts from LCN_* constants.
 	- Implement fs/ntfs/runlist.c::ntfs_rl_truncate_nolock().
+	- Add MFT_RECORD_OLD as a copy of MFT_RECORD in fs/ntfs/layout.h and
+	  change MFT_RECORD to contain the NTFS 3.1+ specific fields.
 
 2.1.20 - Fix two stupid bugs introduced in 2.1.18 release.
 

fs/ntfs/layout.h

@@ -260,7 +260,7 @@ typedef enum {
 enum {
 	MFT_RECORD_IN_USE	= const_cpu_to_le16(0x0001),
 	MFT_RECORD_IS_DIRECTORY = const_cpu_to_le16(0x0002),
-};
+} __attrobite__ ((__packed__));
 
 typedef le16 MFT_RECORD_FLAGS;
 
@@ -385,10 +385,9 @@ typedef struct {
 				   NOTE: Every time the mft record is reused
 				   this number is set to zero.  NOTE: The first
 				   instance number is always 0. */
-/* sizeof() = 42 bytes */
-/* NTFS 3.1+ (Windows XP and above) introduce the following additions. */
-/* 42*/ //le16 reserved;	/* Reserved/alignment. */
-/* 44*/ //le32 mft_record_number;/* Number of this mft record. */
+/* The below fields are specific to NTFS 3.1+ (Windows XP and above): */
+/* 42*/ le16 reserved;		/* Reserved/alignment. */
+/* 44*/ le32 mft_record_number;	/* Number of this mft record. */
 /* sizeof() = 48 bytes */
 /*
  * When (re)using the mft record, we place the update sequence array at this
@@ -401,6 +400,72 @@ typedef struct {
  */
 } __attribute__ ((__packed__)) MFT_RECORD;
 
+/* This is the version without the NTFS 3.1+ specific fields. */
+typedef struct {
+/*Ofs*/
+/*  0	NTFS_RECORD; -- Unfolded here as gcc doesn't like unnamed structs. */
+	NTFS_RECORD_TYPE magic;	/* Usually the magic is "FILE". */
+	le16 usa_ofs;		/* See NTFS_RECORD definition above. */
+	le16 usa_count;		/* See NTFS_RECORD definition above. */
+
+/*  8*/	le64 lsn;		/* $LogFile sequence number for this record.
+				   Changed every time the record is modified. */
+/* 16*/	le16 sequence_number;	/* Number of times this mft record has been
+				   reused. (See description for MFT_REF
+				   above.) NOTE: The increment (skipping zero)
+				   is done when the file is deleted. NOTE: If
+				   this is zero it is left zero. */
+/* 18*/	le16 link_count;	/* Number of hard links, i.e. the number of
+				   directory entries referencing this record.
+				   NOTE: Only used in mft base records.
+				   NOTE: When deleting a directory entry we
+				   check the link_count and if it is 1 we
+				   delete the file. Otherwise we delete the
+				   FILE_NAME_ATTR being referenced by the
+				   directory entry from the mft record and
+				   decrement the link_count.
+				   FIXME: Careful with Win32 + DOS names! */
+/* 20*/	le16 attrs_offset;	/* Byte offset to the first attribute in this
+				   mft record from the start of the mft record.
+				   NOTE: Must be aligned to 8-byte boundary. */
+/* 22*/	MFT_RECORD_FLAGS flags;	/* Bit array of MFT_RECORD_FLAGS. When a file
+				   is deleted, the MFT_RECORD_IN_USE flag is
+				   set to zero. */
+/* 24*/	le32 bytes_in_use;	/* Number of bytes used in this mft record.
+				   NOTE: Must be aligned to 8-byte boundary. */
+/* 28*/	le32 bytes_allocated;	/* Number of bytes allocated for this mft
+				   record. This should be equal to the mft
+				   record size. */
+/* 32*/	leMFT_REF base_mft_record;/* This is zero for base mft records.
+				   When it is not zero it is a mft reference
+				   pointing to the base mft record to which
+				   this record belongs (this is then used to
+				   locate the attribute list attribute present
+				   in the base record which describes this
+				   extension record and hence might need
+				   modification when the extension record
+				   itself is modified, also locating the
+				   attribute list also means finding the other
+				   potential extents, belonging to the non-base
+				   mft record). */
+/* 40*/	le16 next_attr_instance;/* The instance number that will be assigned to
+				   the next attribute added to this mft record.
+				   NOTE: Incremented each time after it is used.
+				   NOTE: Every time the mft record is reused
+				   this number is set to zero.  NOTE: The first
+				   instance number is always 0. */
+/* sizeof() = 42 bytes */
+/*
+ * When (re)using the mft record, we place the update sequence array at this
+ * offset, i.e. before we start with the attributes.  This also makes sense,
+ * otherwise we could run into problems with the update sequence array
+ * containing in itself the last two bytes of a sector which would mean that
+ * multi sector transfer protection wouldn't work.  As you can't protect data
+ * by overwriting it since you then can't get it back...
+ * When reading we obviously use the data from the ntfs record header.
+ */
+} __attribute__ ((__packed__)) MFT_RECORD_OLD;
+
 /*
  * System defined attributes (32-bit).  Each attribute type has a corresponding
  * attribute name (Unicode string of maximum 64 character length) as described