MMMOD_WRITER_MDL_ENTRY

The MMMOD_WRITER_MDL_ENTRY structure holds the state of the file I/O that the Memory Manager does with a paging file. The Memory Manager has zero, one or two of these per paging file, depending on the type of paging file.

Variability

As an internal structure, it varies between versions, and even a little between builds, but far less than do many others.

Layout

LIST_ENTRY Links;

LARGE_INTEGER WriteOffset;

union {
    IO_STATUS_BLOCK IoStatus;
    LARGE_INTEGER LastByte;
} u;

union {
    IO_STATUS_BLOCK IoStatus;
} u;

IRP *Irp;

ULONG_PTR LastPageToWrite;

MMMOD_WRITER_LISTHEAD *PagingListHead;

LIST_ENTRY *CurrentList;

union {
    ULONG LastPageToWrite;
    ULONG KeepForever;
} u1;

union {
    ULONG KeepForever;
} u1;

MODWRITER_FLAGS u1;

ULONG StoreWriteRefCount;

KAPC StoreWriteCompletionApc;

ULONG ByteCount;

ULONG ChargedPages;

MMPAGING_FILE *PagingFile;

FILE_OBJECT *File;

CONTROL_AREA *ControlArea;

ERESOURCE *FileResource;

LARGE_INTEGER WriteOffset;

LARGE_INTEGER IssueTime;

MI_PARTITION *Partition;

MDL *PointerMdl;

struct {
    MDL Mdl;
    PFN_NUMBER Page [ANYSIZE_ARRAY];
};

Flags

The first substantial change in the MMMOD_WRITER_MDL_ENTRY came when Windows Vista did away with the paging list. The reorganisation moved the LastPageToWrite into a union with a new member named KeepForever. The former seems not to have been needed after all, and was soon discarded from the union. The latter is anyway a boolean. Windows 8 formalised this by turning the union into bit fields.

ULONG KeepForever : 1;

ULONG Networked : 1;

ULONG IoPriority : 3;

ULONG ModifiedStoreWrite : 1;