/*++
Routine Description:
This routine creates a stream handle context for the target stream
handle. Optionally, if the context already exists, this routine
replaces it with the new context and releases the old context
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
ReplaceIfExists - Supplies if the stream handle context must be
replaced if already present
StreamContext - Returns the stream context
ContextReplaced - Returns if an existing context was replaced
Return Value:
Status
--*/
NTSTATUS
CtxCreateOrReplaceStreamHandleContext (
__in PFLT_CALLBACK_DATA Cbd,
__in BOOLEAN ReplaceIfExists,
__deref_out PCTX_STREAMHANDLE_CONTEXT *StreamHandleContext,
__out_opt PBOOLEAN ContextReplaced
)
{
NTSTATUS status;
PCTX_STREAMHANDLE_CONTEXT streamHandleContext;
PCTX_STREAMHANDLE_CONTEXT oldStreamHandleContext;
PAGED_CODE();
*StreamHandleContext = NULL;
if (ContextReplaced != NULL) *ContextReplaced = FALSE;
//
// Create a stream context
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Creating stream handle context (FileObject = %p, Instance = %p)\n",
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = CtxCreateStreamHandleContext( &streamHandleContext );
if (!NT_SUCCESS( status ))
{
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to create stream context with status 0x%x. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
return status;
}
//
// Set the new context we just allocated on the file object
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Setting stream context %p (FileObject = %p, Instance = %p, ReplaceIfExists = %x)\n",
streamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance,
ReplaceIfExists) );
status = FltSetStreamHandleContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
ReplaceIfExists ? FLT_SET_CONTEXT_REPLACE_IF_EXISTS : FLT_SET_CONTEXT_KEEP_IF_EXISTS,
streamHandleContext,
&oldStreamHandleContext );
if (!NT_SUCCESS( status ))
{
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set stream handle context with status 0x%x. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// We release the context here because FltSetStreamContext failed
//
// If FltSetStreamContext succeeded then the context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Releasing stream handle context %p (FileObject = %p, Instance = %p)\n",
streamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
FltReleaseContext( streamHandleContext );
if (status != STATUS_FLT_CONTEXT_ALREADY_DEFINED)
{
//
// FltSetStreamContext failed for a reason other than the context already
// existing on the stream. So the object now does not have any context set
// on it. So we return failure to the caller.
//
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set stream context with status 0x%x != STATUS_FLT_CONTEXT_ALREADY_DEFINED. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
return status;
}
//
// We will reach here only if we have failed with STATUS_FLT_CONTEXT_ALREADY_DEFINED
// and we can fail with that code only if the context already exists and we have used
// the FLT_SET_CONTEXT_KEEP_IF_EXISTS flag
ASSERT( ReplaceIfExists == FALSE );
//
// Race condition. Someone has set a context after we queried it.
// Use the already set context instead
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Stream context already defined. Retaining old stream context %p (FileObject = %p, Instance = %p)\n",
oldStreamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// Return the existing context. Note that the new context that we allocated has already been
// realeased above.
//
streamHandleContext = oldStreamHandleContext;
status = STATUS_SUCCESS;
}
else
{
//
// FltSetStreamContext has suceeded. The new context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
// However, if we have replaced an existing context then we need to
// release the old context so as to decrement the ref count on it.
//
// Note that the memory allocated to the objects within the context
// will be freed in the context cleanup and must not be done here.
//
if ( ReplaceIfExists && oldStreamHandleContext != NULL)
{
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Releasing old stream handle context %p (FileObject = %p, Instance = %p)\n",
oldStreamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
FltReleaseContext( oldStreamHandleContext );
if (ContextReplaced != NULL) *ContextReplaced = TRUE;
}
}
*StreamHandleContext = streamHandleContext;
return status;
}
NTSTATUS
CtxCreateOrReplaceStreamHandleContext (
__in PFLT_CALLBACK_DATA Cbd,
__in BOOLEAN ReplaceIfExists,
__deref_out PSTREAMHANDLE_CONTEXT *StreamHandleContext,
__out_opt PBOOLEAN ContextReplaced
)
/*++
Routine Description:
This routine creates a stream handle context for the target stream
handle. Optionally, if the context already exists, this routine
replaces it with the new context and releases the old context
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
ReplaceIfExists - Supplies if the stream handle context must be
replaced if already present
StreamContext - Returns the stream context
ContextReplaced - Returns if an existing context was replaced
Return Value:
Status
--*/
{
NTSTATUS status;
PSTREAMHANDLE_CONTEXT streamHandleContext;
PSTREAMHANDLE_CONTEXT oldStreamHandleContext;
PAGED_CODE();
*StreamHandleContext = NULL;
if (ContextReplaced != NULL) *ContextReplaced = FALSE;
//
// Create a stream context
//
status = CtxCreateStreamHandleContext( &streamHandleContext );
if (!NT_SUCCESS( status )) {
return status;
}
//
// Set the new context we just allocated on the file object
//
status = FltSetStreamHandleContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
ReplaceIfExists ? FLT_SET_CONTEXT_REPLACE_IF_EXISTS : FLT_SET_CONTEXT_KEEP_IF_EXISTS,
streamHandleContext,
&oldStreamHandleContext );
if (!NT_SUCCESS( status )) {
//
// We release the context here because FltSetStreamContext failed
//
// If FltSetStreamContext succeeded then the context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
FltReleaseContext( streamHandleContext );
if (status != STATUS_FLT_CONTEXT_ALREADY_DEFINED) {
//
// FltSetStreamContext failed for a reason other than the context already
// existing on the stream. So the object now does not have any context set
// on it. So we return failure to the caller.
//
return status;
}
//
// We will reach here only if we have failed with STATUS_FLT_CONTEXT_ALREADY_DEFINED
// and we can fail with that code only if the context already exists and we have used
// the FLT_SET_CONTEXT_KEEP_IF_EXISTS flag
ASSERT( ReplaceIfExists == FALSE );
//
// Race condition. Someone has set a context after we queried it.
// Use the already set context instead
//
//
// Return the existing context. Note that the new context that we allocated has already been
// realeased above.
//
streamHandleContext = oldStreamHandleContext;
status = STATUS_SUCCESS;
} else {
//
// FltSetStreamContext has suceeded. The new context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
// However, if we have replaced an existing context then we need to
// release the old context so as to decrement the ref count on it.
//
// Note that the memory allocated to the objects within the context
// will be freed in the context cleanup and must not be done here.
//
if ( ReplaceIfExists &&
oldStreamHandleContext != NULL) {
streamHandleContext->TaskState = oldStreamHandleContext->TaskState;
FltReleaseContext( oldStreamHandleContext );
if (ContextReplaced != NULL) *ContextReplaced = TRUE;
}
}
*StreamHandleContext = streamHandleContext;
return status;
}
