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Clear up some confusion about the IRP_MJ_LOCK_CONTROL #3927

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Sep 22, 2025
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Merged

Clear up some confusion about the IRP_MJ_LOCK_CONTROL #3927

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7d252f2
Clear up some confusion about the IRP_MJ_LOCK_CONTROL
rodwiddowson Mar 8, 2025
111cc92
Revise FLT_PARAMETERS documentation for IRP_MJ_LOCK_CONTROL
lorihollasch Sep 22, 2025
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9 changes: 5 additions & 4 deletions windows-driver-docs-pr/ifs/flt-parameters-for-irp-mj-lock-control.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ api_location:
- fltkernel.h
api_type:
- HeaderDef
ms.date: 03/13/2023
ms.date: 09/22/2025
ms.topic: reference
---

Expand Down Expand Up @@ -45,11 +45,11 @@ typedef union _FLT_PARAMETERS {

- **ByteOffset**: Starting byte offset within the file of the range to be locked.

- **ProcessId**: Opaque pointer to the process object for the process that requested the byte-range lock.
- **ProcessId**: Opaque pointer to the process object for the process that requested the byte-range lock. This member is always populated, but only meaningful for FastIo locking operations. It's distinguished from the value returned by [**FltGetRequestorProcess**](/windows-hardware/drivers/ddi/fltkernel/nf-fltkernel-fltgetrequestorprocess) because **ProcessId** always identifies the original requesting process, while **FltGetRequestorProcess** might return either the result of [**IoGetRequestorProcess**](/windows-hardware/drivers/ddi/ntifs/nf-ntifs-iogetrequestorprocess) (for IRP operations) or [**PsGetCurrentProcess**](/windows-hardware/drivers/ddi/ntddk/nf-ntddk-psgetcurrentprocessid) (for FastI/O operations), which can differ from the original requestor.

- **FailImmediately**: Boolean value specifying whether the lock request should fail if the lock cannot be granted immediately. This member is set to **FALSE** if the requesting thread can be put into a wait state until the request is granted or **TRUE** if it cannot.
- **FailImmediately**: Boolean value specifying whether the lock request should fail if the lock cannot be granted immediately. This member is set to **FALSE** if the requesting thread can be put into a wait state until the request is granted or **TRUE** if it cannot. This member is always populated, but only meaningful for FastIo locking operations.

- **ExclusiveLock**: Boolean value specifying whether an exclusive lock is requested. This member is set to **TRUE** if an exclusive lock is requested or **FALSE** if a shared lock is requested.
- **ExclusiveLock**: Boolean value specifying whether an exclusive lock is requested. This member is set to **TRUE** if an exclusive lock is requested or **FALSE** if a shared lock is requested. This member is always populated, but only meaningful for FastIo locking operations.

## Remarks

Expand Down Expand Up @@ -100,3 +100,4 @@ IRP_MJ_LOCK_CONTROL can be an IRP-based I/O operation or a fast I/O operation.
[**PFLT_COMPLETE_LOCK_CALLBACK_DATA_ROUTINE**](/windows-hardware/drivers/ddi/fltkernel/nc-fltkernel-pflt_complete_lock_callback_data_routine)

[**PUNLOCK_ROUTINE**](/windows-hardware/drivers/ddi/ntifs/nc-ntifs-punlock_routine)