RxChangeBufferingState function (rxprocs.h)

Article
04/01/2021

RxChangeBufferingState is called to process a buffering state change request.

Syntax

NTSTATUS RxChangeBufferingState(
  PSRV_OPEN SrvOpen,
  PVOID     Context,
  BOOLEAN   ComputeNewState
);

Parameters

SrvOpen

A pointer to the SRV_OPEN data structure to be changed.

Context

A pointer to the context parameter for use by the network mini-redirector callback.

ComputeNewState

The value that indicates if the new buffering state is to be computed. When this value is set to TRUE, the new buffering state is determined by calling the network mini-redirector to compute the new buffering state. When this value is FALSE, the new buffering state is determined by the BufferingFlags member of the passed in SrvOpen structure.

Return value

RxChangeBufferingState always returns STATUS_SUCCESS whether this routine was successful or if an error occurs. If an error occurs, the buffering state is changed so that no buffering is enabled.

Remarks

If local buffering is disabled for this FCB (FCB_STATE_DISABLE_LOCAL_BUFFERING is set in the FcbState structure member of the FCB), this will disable local buffering independent of the open mode on the FCB and any default buffering options. When FCB_STATE_DISABLE_LOCAL_BUFFERING is set, the new buffering state set by RxChangeBufferingState will be to disable all buffering.

If ComputeNewState is TRUE, then the MRxComputeNewBufferingState routine exported by the network mini-redirector is called to compute the new buffering state to use.

If the FCB is acquired exclusively and ComputeNewState is FALSE. then RxChangeBufferingState will set the following buffering state options:

FCB_STATE_WRITECACHING_ENABLED
FCB_STATE_FILESIZECACHEING_ENABLED
FCB_STATE_FILETIMECACHEING_ENABLED
FCB_STATE_WRITEBUFFERING_ENABLED
FCB_STATE_LOCK_BUFFERING_ENABLED
FCB_STATE_READBUFFERING_ENABLED
FCB_STATE_READCACHING_ENABLED

To acquire the FCB exclusively requires that the FCB must not be opened with any of the following values:

ShareAccess.SharedRead
ShareAccess.SharedWrite
ShareAccess.SharedDelete

RDBSS does not currently use a number of possible buffering options, so these options are ignored internally by RDBSS when they are set off using RxChangeBufferingState. These ignored buffering options include the following:

FCB_STATE_WRITEBUFFERING_ENABLED
FCB_STATE_READBUFFERING_ENABLED
FCB_STATE_OPENSHARING_ENABLED
FCB_STATE_COLLAPSING_ENABLED
FCB_STATE_FILESIZECACHEING_ENABLED
FCB_STATE_FILETIMECACHEING_ENABLED

If the FCB_STATE_WRITECACHING_ENABLED buffering state is changed to off, any FCB in the system cache is flushed.

On exit from RxChangeBufferingState, there is no change in resource ownership.

Requirements

Requirement	Value
Target Platform	Desktop
Header	rxprocs.h (include Rxprocs.h, Struchdr.h, Fcb.h)
IRQL	<= APC_LEVEL