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Operations That Can Be IRP-Based or Fast I/O

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The following types of operations can be IRP-based or fast I/O operations:

  • IRP_MJ_DEVICE_CONTROL. (Note that IRP_MJ_INTERNAL_DEVICE_CONTROL is always IRP-based.)

  • IRP_MJ_QUERY_INFORMATION. This operation can be fast I/O if the FileInformationClass parameter is FileBasicInformation, FileStandardInformation, or FileNetworkOpenInformation.

  • IRP_MJ_READ. Minifilter drivers can set the FLTFL_OPERATION_REGISTRATION_SKIP_CACHED_IO flag in the FLT_OPERATION_REGISTRATION structure to avoid receiving fast I/O IRP_MJ_READ operations and cached IRP-based reads.

  • IRP_MJ_WRITE. Minifilter drivers can set the FLTFL_OPERATION_REGISTRATION_SKIP_CACHED_IO flag in the FLT_OPERATION_REGISTRATION structure to avoid receiving fast I/O IRP_MJ_WRITE operations and cached IRP-based writes.

When any of these operations is a fast I/O operation, it always uses neither buffered nor direct I/O, even if the equivalent IRP-based operation uses a different buffering method.

When IRP_MJ_DEVICE_CONTROL is a fast I/O operation, it always uses neither buffered nor direct I/O, regardless of the IOCTL's transfer type.

Although IRP_MJ_LOCK_CONTROL can be an IRP-based or fast I/O operation, it has no buffers.