FSRTL_COMMON_FCB_HEADER structure (ntifs.h)
Do not use the FSRTL_COMMON_FCB_HEADER structure outside of the FSRTL_ADVANCED_FCB_HEADER structure. The FSRTL_COMMON_FCB_HEADER structure contains context information that a file system maintains about a file, directory, volume, or alternate data stream.
Syntax
typedef struct _FSRTL_COMMON_FCB_HEADER {
CSHORT NodeTypeCode;
CSHORT NodeByteSize;
UCHAR Flags;
UCHAR IsFastIoPossible;
UCHAR Flags2;
UCHAR Reserved : 4;
UCHAR Version : 4;
PERESOURCE Resource;
PERESOURCE PagingIoResource;
LARGE_INTEGER AllocationSize;
LARGE_INTEGER FileSize;
LARGE_INTEGER ValidDataLength;
} FSRTL_COMMON_FCB_HEADER;
Members
NodeTypeCode
Reserved for system use.
NodeByteSize
Reserved for system use.
Flags
Bitmask of flags that indicate support for various features. This member must be a bitwise OR combination of one or more of the following values:
| Value | Meaning |
|---|---|
| FSRTL_FLAG_FILE_MODIFIED | Reserved for system use. |
| FSRTL_FLAG_FILE_LENGTH_CHANGED | Reserved for system use. |
| FSRTL_FLAG_LIMIT_MODIFIED_PAGES | Reserved for system use. File system drivers (except for filter drivers) that must set or clear a limit of modified data for a file should call CcSetDirtyPageThreshold. |
| FSRTL_FLAG_ACQUIRE_MAIN_RSRC_EX | Reserved for system use. |
| FSRTL_FLAG_ACQUIRE_MAIN_RSRC_SH | Reserved for system use. |
| FSRTL_FLAG_USER_MAPPED_FILE | The Cache Manager sets this flag to indicate that a view is mapped to a file. |
| FSRTL_FLAG_ADVANCED_HEADER | This flag indicates that the file system is using FSRTL_ADVANCED_FCB_HEADER instead of FSRTL_COMMON_FCB_HEADER in its file control block (FCB) structures. This flag is required because use of the FSRTL_COMMON_FCB_HEADER structure outside of the FSRTL_ADVANCED_FCB_HEADER structure is deprecated. |
| FSRTL_FLAG_EOF_ADVANCE_ACTIVE | Reserved for system use. |
IsFastIoPossible
This member must be one of the following values:
| Value | Meaning |
|---|---|
| FastIoIsPossible | Fast I/O is possible. |
| FastIoIsQuestionable | An exclusive byte range lock exists for the file. The caller should call the file system's FastIoCheckIfPossible routine. |
| FastIoIsNotPossible | The FCB for the file is bad, or an opportunistic lock (also called "oplock") exists for the file. |
For more information about these values, see the reference entries for FsRtlAreThereCurrentFileLocks, FsRtlCopyRead, and FsRtlCopyWrite.
Flags2
Bitmask of flags that the file system sets to indicate support for various features. This member must be one or more of the following values:
| Value | Meaning |
|---|---|
| FSRTL_FLAG2_DO_MODIFIED_WRITE | See details following this table. |
| FSRTL_FLAG2_PURGE_WHEN_MAPPED | If this flag is set, the Cache Manager will flush and purge the cache map when a user first maps a file. |
| FSRTL_FLAG2_SUPPORTS_FILTER_CONTEXTS | This flag indicates that the file system is using FSRTL_ADVANCED_FCB_HEADER instead of FSRTL_COMMON_FCB_HEADER in its FCB structures. This flag is required because use of the FSRTL_COMMON_FCB_HEADER structure outside of the FSRTL_ADVANCED_FCB_HEADER structure is deprecated. |
| FSRTL_FLAG2_IS_PAGING_FILE | If set, this FCB header is associated with a page file. |
The FSRTL_FLAG2_DO_MODIFIED_WRITE flag is used together with the FsContext2 member of the file object for the file stream as follows:
If the FsContext2 member of the file object is non-NULL, the file stream represents an open instance of a file or a directory, and the value of this flag is ignored by the operating system.
If the FsContext2 member of the file object is NULL, and this flag is not set, the file object is a stream file object, and the stream is a modified-no-write (MNW) stream.
If the FsContext2 member of the file object is NULL, and this flag is set, the file object is a stream file object, and the stream is writable.
Reserved
Reserved for system use. Drivers must set this bit-field to zero.
Version
Reserved for system use. This bit-field is set by the FsRtlSetupAdvancedHeader or FsRtlSetupAdvancedHeaderEx macro. Starting with Windows Vista, the value of this bit-field is FSRTL_FCB_HEADER_V1 or greater; otherwise, the value is FSRTL_FCB_HEADER_V0. See FSRTL_ADVANCED_FCB_HEADER for more information.
Resource
Pointer to an initialized resource variable, for which the file system supplies the storage that will be used to synchronize I/O access to the FCB. The resource variable must be allocated from nonpaged pool.
Filter drivers should treat this member as opaque.
PagingIoResource
Pointer to an additional resource variable, for which the file system supplies the storage that will be used to synchronize paging I/O access to the FCB. The resource variable must be allocated from nonpaged pool.
Filter drivers should treat this member as opaque.
AllocationSize
Allocation size for the file stream.
For more information about the AllocationSize, FileSize, and ValidDataLength members, see CcInitializeCacheMap.
FileSize
File size of the file stream.
ValidDataLength
Valid data length of the file stream.
Remarks
File systems must set the FsContext member of every file object to point to an FSRTL_ADVANCED_FCB_HEADER structure. This structure can be embedded inside of a file-system-specific stream context object structure (the remainder of this structure is file-system-specific). Usually, the FSRTL_ADVANCED_FCB_HEADER structure is a file control block (FCB). However, on some file systems that support multiple data streams, such as NTFS, it is a stream control block (SCB).
To support filter manager and filter contexts, file systems must use the FSRTL_ADVANCED_FCB_HEADER structure in their stream context objects. All Microsoft file systems use this structure, and all third-party file system developers must do so as well. FCBs and SCBs for all classes of open requests, including volume open requests, must include this structure.
If the file is used as a paging file, the FSRTL_ADVANCED_FCB_HEADER structure must be allocated from nonpaged pool. Otherwise, it can be allocated from paged or nonpaged pool.
Requirements
| Requirement | Value |
|---|---|
| Header | ntifs.h (include Ntifs.h, Fltkernel.h) |