The generic storage class driver (classpnp.sys) exposes an I/O control (IOCTL) interface for issuing Persistent Reserve In commands. The behavior of the storage device when a Persistent Reserve In command is received is described in the SCSI Primary Commands - 2 (SPC-2) specification. The IOCTL interface requires the caller to have read access to the physical device for Persistent Reserve In commands. User-mode applications, services, and kernel-mode drivers can use this IOCTL to control persistent reservations. If called from a driver, this IOCTL must be called from a thread running at IRQL < DISPATCH_LEVEL. This IOCTL is defined with FILE_READ_ACCESS, requiring a device handle to have read permissions to issue the Persistent Reserve In command.

Major code


Input buffer

The buffer at Irp->AssociatedIrp.SystemBuffer contains a PERSISTENT_RESERVE_COMMAND structure. You must allocate the buffer from nonpaged pool and must align it correctly for the target device and adapter.

PR_IN.ServiceAction can be one of the following:


PR_IN.Allocation length is the size (in bytes) of the buffer allocated for the returned parameter list.

Input buffer length

The length of input buffer, in bytes.

Output buffer

For PR_IN.ServiceAction = RESERVATION_ACTION_READ_KEYS, the output buffer contains a PRI_REGISTRATION_LIST structure and must be at least sizeof(PRI_REGISTRATION_LIST).

For PR_IN.ServiceAction = RESERVATION_ACTION_READ_RESERVATIONS, the output buffer contains a PRI_RESERVATION_LIST structure and must be at least sizeof(PRI_RESERVATION_LIST).

If the allocated buffer is too small to return all the Persistent Reserve In data, success will be returned and the required size will be returned in the parameter list AdditionalLength field.

Output buffer length

The length of the output buffer, in bytes.

Status block

The Information field is set to the size of the output buffer. For ServiceAction = RESERVATION_ACTION_READ_KEYS, the output buffer is a PRI_REGISTRATION_LIST structure. For ServiceAction = RESERVATION_ACTION_READ_RESERVATIONS, the output buffer is a PRI_REGISTRATION_LIST structure.

The Status field is set to one of the following:

Value Meaning
STATUS_BUFFER_OVERFLOW (ERROR_MORE_DATA) The output buffer is too small to hold the Persistent Reserve In data. The output buffer's AdditionalLength field will contain the size of the data to be returned.
STATUS_DEVICE_BUSY (ERROR_BUSY) The command failed because of a Reservation Conflict (for more information, see the SCSI Primary Commands - 2 (SPC-2)** specification).
STATUS_INFO_LENGTH_MISMATCH The input buffer length for the IOCTL is less than sizeof(PERSISTENT_RESERVE_COMMAND) or the size that is specified in the PERSISTENT_RESERVE_COMMAND data structure is less than sizeof(PERSISTENT_RESERVE_COMMAND).
STATUS_INVALID_PARAMETER (ERROR_INVALID_PARAMETER) The input buffer structure is incorrectly sized or populated.
STATUS_INVALID_USER_BUFFER (ERROR_INVALID_USER_BUFFER) The input or output buffer is not aligned correctly for the device or adapter. This status could only be returned when a driver sends an IOCTL to the storage stack. This status will not be returned when a user-mode application sends the IOCTL through the DeviceIoControl API as the I/O Manager automatically aligns the buffers.
STATUS_IO_DEVICE_ERROR (ERROR_IO_DEVICE) The device does not support the Persistent Reserve In command.
STATUS_SUCCESS The operation was successful.


Requirement Value
Header ntddstor.h (include Ntddstor.h)