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Ntfs!LfsGetLbcb函数分析之Ntfs!LfsPrepareLfcbForLogRecord

news 来源：原创 2025/6/21 12:43:23

第一部分：

PLBCB
LfsGetLbcb (
IN PLFCB Lfcb
)
{

        //
        // Pin the desired record page.
        //

        LfsPreparePinWriteData( Lfcb,
                                Lfcb->NextLogPage,
                                (ULONG)Lfcb->LogPageSize,
                                FlagOn( Lfcb->Flags, LFCB_REUSE_TAIL ),
                                &PageHeader,
                                &PageHeaderBcb );

        //
        // Now allocate an Lbcb.
        //

LfsAllocateLbcb( Lfcb, &Lbcb );

        //
        // Now initialize the rest of the Lbcb fields.
        //

        Lbcb->FileOffset = Lfcb->NextLogPage;
        Lbcb->SeqNumber = Lfcb->SeqNumber;
        Lbcb->BufferOffset = Lfcb->LogPageDataOffset;

        //
        // Store the next page in the Lfcb.
        //

        LfsNextLogPageOffset( Lfcb,
                              Lfcb->NextLogPage,
                              &Lfcb->NextLogPage,
                              &WrappedOrUsaError );

        Lbcb->Length = Lfcb->LogPageSize;
        Lbcb->PageHeader = PageHeader;
        Lbcb->LogPageBcb = PageHeaderBcb;

1: kd> dt _lbcb 0xe1368a94-c
Ntfs!_LBCB
   +0x000 NodeTypeCode     : 0n2050
   +0x002 NodeByteSize     : 0n96
   +0x004 WorkqueLinks     : _LIST_ENTRY [ 0xe13517f0 - 0xe1357ea4 ]
   +0x00c ActiveLinks      : _LIST_ENTRY [ 0xe13517f8 - 0xe13517f8 ]
   +0x018 FileOffset       : 0n7884800
   +0x020 Length           : 0n4096
   +0x028 SeqNumber        : 0n8
   +0x030 BufferOffset     : 0n2256
   +0x038 PageHeader       : 0xc2c45000 Void
   +0x03c LogPageBcb       : 0x894c6658 Void
   +0x040 LastLsn          : _LARGE_INTEGER 0x80f0b0f
   +0x048 LastEndLsn       : _LARGE_INTEGER 0x80f0b0f
   +0x050 Flags            : 1
   +0x054 LbcbFlags        : 6
   +0x058 ResourceThread   : 0x8999c023

1: kd> dx -id 0,0,899a2278 -r1 ((Ntfs!_LFCB *)0xe1351768)
((Ntfs!_LFCB *)0xe1351768)                 : 0xe1351768 [Type: _LFCB *]
    [+0x000] NodeTypeCode     : 2051 [Type: short]
    [+0x002] NodeByteSize     : 352 [Type: short]
    [+0x004] LfcbLinks        [Type: _LIST_ENTRY]
    [+0x00c] LchLinks         [Type: _LIST_ENTRY]
    [+0x014] FileObject       : 0x89469688 [Type: _FILE_OBJECT *]
    [+0x018] FileSize         : 67108864 [Type: __int64]
    [+0x020] LogPageSize      : 4096 [Type: __int64]
    [+0x028] LogPageMask      : 0xfff [Type: unsigned long]
    [+0x02c] LogPageInverseMask : -4096 [Type: long]
    [+0x030] LogPageShift     : 0xc [Type: unsigned long]
    [+0x038] FirstLogPage     : 16384 [Type: __int64]
    [+0x040] NextLogPage      : 7888896 [Type: __int64]

1: kd> ?0n7888896
Evaluate expression: 7888896 = 00786000

1: kd> ?0n67108864
Evaluate expression: 67108864 = 04000000

F:\srv03rtm>grep "LfsGetLbcb" -rn F:\srv03rtm\base\fs |grep -v "inary"
F:\srv03rtm\base\fs/lfs/lbcbsup.c:31:#pragma alloc_text(PAGE, LfsGetLbcb)
F:\srv03rtm\base\fs/lfs/lbcbsup.c:194:LfsGetLbcb (
F:\srv03rtm\base\fs/lfs/lbcbsup.c:223:    DebugTrace( +1, Dbg, "LfsGetLbcb: Entered\n", 0 );
F:\srv03rtm\base\fs/lfs/lbcbsup.c:374:        DebugUnwind( LfsGetLbcb );
F:\srv03rtm\base\fs/lfs/lbcbsup.c:399:        DebugTrace( -1, Dbg, "LfsGetLbcb: Exit\n", 0 );
F:\srv03rtm\base\fs/lfs/lfsprocs.h:176:LfsGetLbcb (
F:\srv03rtm\base\fs/lfs/logrcsup.c:552:            ThisLbcb = LfsGetLbcb( Lfcb );
F:\srv03rtm\base\fs/ntfs/mp/ntfs.prf:138:LfsGetLbcb@4

第二部分：

VOID
LfsPrepareLfcbForLogRecord (
    IN OUT PLFCB Lfcb,
    IN ULONG RemainingLogBytes
    )
{

while (TRUE) {

        //
        // If the Lbcb link we have is the head of the list, we will need another
        // Lbcb.
        //

if (LbcbLinks == &Lfcb->LbcbActive) {

ThisLbcb = LfsGetLbcb( Lfcb );

} else {

            ThisLbcb = CONTAINING_RECORD( LbcbLinks,
                                          LBCB,
                                          ActiveLinks );
        }

第三部分：

BOOLEAN
LfsWriteLogRecordIntoLogPage (
    IN PLFCB Lfcb,
    IN PLCH Lch,
    IN ULONG NumberOfWriteEntries,
    IN PLFS_WRITE_ENTRY WriteEntries,
    IN LFS_RECORD_TYPE RecordType,
    IN TRANSACTION_ID *TransactionId OPTIONAL,
    IN LSN ClientUndoNextLsn OPTIONAL,
    IN LSN ClientPreviousLsn OPTIONAL,
    IN LONG UndoRequirement,
    IN BOOLEAN ForceToDisk,
    OUT PLSN Lsn
    )
{

        //
        // We update the Lfcb so that we can start putting the log record into
        // the top of the Lbcb active list.
        //

LfsPrepareLfcbForLogRecord( Lfcb,
RemainingLogBytes + Lfcb->RecordHeaderLength );

        ThisLbcb = CONTAINING_RECORD( Lfcb->LbcbActive.Flink,
                                      LBCB,
                                      ActiveLinks );