FsRtlAllocateExtraCreateParameter function (ntifs.h)

The FsRtlAllocateExtraCreateParameter routine allocates memory for an extra create parameter (ECP) context structure and generates a pointer to that structure.

Syntax

NTSTATUS FsRtlAllocateExtraCreateParameter(
  [in]           LPCGUID                                        EcpType,
  [in]           ULONG                                          SizeOfContext,
  [in]           FSRTL_ALLOCATE_ECP_FLAGS                       Flags,
  [in, optional] PFSRTL_EXTRA_CREATE_PARAMETER_CLEANUP_CALLBACK CleanupCallback,
  [in]           ULONG                                          PoolTag,
  [out]          PVOID                                          *EcpContext
);

Parameters

[in] EcpType

A pointer to a GUID that indicates the type of the ECP context structure. See Using GUIDs in Drivers for more information.

[in] SizeOfContext

The size, in bytes, of the context structure.

[in] Flags

Defines pool allocation options. The following describes how pool will be allocated when one or more of the listed flag values are combined with the Flags parameter by using a bitwise OR operation:

• FSRTL_ALLOCATE_ECP_FLAG_NONPAGED_POOL - Non-paged pool will be allocated. If this flag value is not used, paged pool will be allocated.

• FSRTL_ALLOCATE_ECPLIST_FLAG_CHARGE_QUOTA - All pool allocated by FsRtlAllocateExtraCreateParameter will be charged against the current process' memory quota.

If more than one flag is used, all of the effects associated with the utilized flag values will occur.

[in, optional] CleanupCallback

Optional pointer to a filter-defined cleanup callback routine of type PFSRTL_EXTRA_CREATE_PARAMETER_CLEANUP_CALLBACK. The cleanup callback routine is called when the ECP structure (created by the FsRtlAllocateExtraCreateParameter routine) is deleted. Set this parameter to NULL if a cleanup callback routine is not applicable.

[in] PoolTag

Specifies the pool tag for the allocated memory. For more information, see the Tag parameter of ExAllocatePoolWithTag.

[out] EcpContext

Receives a pointer to the allocated ECP context structure. If the routine failed to allocate sufficient pool, the value pointed to by EcpContext will be NULL and FsRtlAllocateExtraCreateParameter will return status code STATUS_INSUFFICIENT_RESOURCES.

Return value

FltAllocateExtraCreateParameter returns a status code such as one of the following:

Remarks

By default, the FsRtlAllocateExtraCreateParameter routine allocates paged memory pool for a ECP context structure. If the FSRTL_ALLOCATE_ECP_FLAG_NONPAGED_POOL bitmask is used as described in the Flags parameter, a non-paged memory pool is allocated. After this pool has been allocated and the ECP context structure has been initialized, the FltInsertExtraCreateParameter routine is used to insert the ECP context structure (ECP list element) into an ECP list structure (ECP_LIST).

If the caller allocates ECP_LIST and one or more ECPs are used in a call to IoCreateFileEx, the previous description is correct. In this case, the system does not free any of the ECPs, so the caller can make multiple calls to IoCreateFileEx with the same ECP set. However, if a file system or file system filter driver attaches an ECP to an existing or newly-created ECP_LIST while processing an IRP_MJ_CREATE request, this ECP is automatically cleaned up when the IRP completes. As a result, a filter driver does not have to clean up ECPs that are added dynamically. This allows a filter driver's ECP to be properly propagated across the reparse points--a process that can require multiple IRP_MJ_CREATE requests to be generated.

Requirements

See also

ECP_LIST

FltAllocateExtraCreateParameterFromLookasideList

FltAllocateExtraCreateParameterList

FltCreateFileEx2

FltFreeExtraCreateParameter

FltFreeExtraCreateParameterList

FltGetEcpListFromCallbackData

FltInsertExtraCreateParameter

FltRemoveExtraCreateParameter

FltSetEcpListIntoCallbackData

IoCreateFileEx

PFSRTL_EXTRA_CREATE_PARAMETER_CLEANUP_CALLBACK