MRxLowIOSubmit[LOWIO_OP_WRITE] routine

Article
03/14/2023

The MRxLowIOSubmit[LOWIO_OP_WRITE] routine is called by RDBSS to issue a write request to the network mini-redirector.

Syntax

PMRX_CALLDOWN MRxLowIOSubmit[LOWIO_OP_WRITE];

NTSTATUS MRxLowIOSubmit[LOWIO_OP_WRITE](
  _Inout_ PRX_CONTEXT RxContext
)
{ ... }

Parameters

RxContext [in, out]
A pointer to the RX_CONTEXT structure. This parameter contains the IRP that is requesting the operation.

Return value

MRxLowIOSubmit[LOWIO_OP_WRITE] returns STATUS_SUCCESS on success or an appropriate NTSTATUS value, such as one of the following:

Return code	Description
STATUS_FILE_CLOSED	The FCB structure was acquired, but the associated SRV_OPEN structure has been closed.
STATUS_INSUFFICIENT_RESOURCES	There were insufficient resources to complete the request.
STATUS_INVALID_DEVICE_REQUEST	An invalid device request was specified.
STATUS_INVALID_PARAMETER	An invalid parameter was specified in RxContext.
STATUS_NOT_IMPLEMENTED	This routine is not implemented.
STATUS_NOT_SUPPORTED	The request specified is not supported by the network mini-redirector.

Remarks

RDBSS calls MRxLowIOSubmit[LOWIO_OP_WRITE] in response to receiving an IRP_MJ_WRITE request.

Before calling MRxLowIOSubmit[LOWIO_OP_WRITE], RDBSS modifies the following members in the RX_CONTEXT structure pointed to by the RxContext parameter:

The LowIoContext.Operation member is set to LOWIO_OP_WRITE.

The LowIoContext.ResourceThreadId member is set to the thread of the process that initiated the operation in RDBSS.

The LowIoContext.ParamsFor.ReadWrite.Key member is set to the value of IrpSp->Parameters.Read.Key.

The ParamsFor.ReadWrite.Flags member has the LOWIO_READWRITEFLAG_PAGING_IO bit is set on if Irp->Flags has the IRP_PAGING_IO bit on.

The ParamsFor.ReadWrite.Buffer member is set to the user buffer locked for IoWriteAccess.

The LowIoContext.ParamsFor.ReadWrite.ByteCount member is set to the value of IrpSp->Parameters.Write.Length.

A write request is normally implemented by a network mini-redirector as an asynchronous operation because it can take considerable time. The operation usually consists of sending a network request to the remote server. The response is obtained when the write request is completed on the server. This is an example of an operation for which the network mini-redirector may need to register a context for handling cancellations initiated locally.

While the MRxLowIOSubmit[LOWIO_OP_WRITE] routine is processing, the LowIoContext.ResourceThreadId member of RX_CONTEXT is guaranteed to indicate the thread of the process that initiated the operation in RDBSS. The LowIoContext.ResourceThreadId member can be used to release the FCB structure on behalf of another thread. When an asynchronous routine completes, the FCB structure that was acquired from the initial thread can be released. The FCB structure can be released by calling RxReleaseFcbResourceForThreadInMRx.

Requirements

Target platform	Desktop
Header	Mrx.h (include Mrx.h)