CancelIo function

Cancels all pending input and output (I/O) operations that are issued by the calling thread for the specified file. The function does not cancel I/O operations that other threads issue for a file handle.

To cancel I/O operations from another thread, use the CancelIoEx function.

Syntax

BOOL WINAPI CancelIo(
  _In_ HANDLE hFile
);

Parameters

hFile [in]

A handle to the file.

The function cancels all pending I/O operations for this file handle.

Return value

If the function succeeds, the return value is nonzero. The cancel operation for all pending I/O operations issued by the calling thread for the specified file handle was successfully requested. The thread can use the GetOverlappedResult function to determine when the I/O operations themselves have been completed.

If the function fails, the return value is zero (0). To get extended error information, call the GetLastError function.

Remarks

If there are any pending I/O operations in progress for the specified file handle, and they are issued by the calling thread, the CancelIo function cancels them. CancelIo cancels only outstanding I/O on the handle, it does not change the state of the handle; this means that you cannot rely on the state of the handle because you cannot know whether the operation was completed successfully or canceled.

The I/O operations must be issued as overlapped I/O. If they are not, the I/O operations do not return to allow the thread to call the CancelIo function. Calling the CancelIo function with a file handle that is not opened with FILE_FLAG_OVERLAPPED does nothing.

All I/O operations that are canceled complete with the error ERROR_OPERATION_ABORTED, and all completion notifications for the I/O operations occur normally.

In Windows 8 and Windows Server 2012, this function is supported by the following technologies.

Technology Supported
Server Message Block (SMB) 3.0 protocol
Yes
SMB 3.0 Transparent Failover (TFO)
Yes
SMB 3.0 with Scale-out File Shares (SO)
Yes
Cluster Shared Volume File System (CsvFS)
Yes
Resilient File System (ReFS)
Yes

Requirements

Minimum supported client
Windows XP [desktop apps | UWP apps]
Minimum supported server
Windows Server 2003 [desktop apps | UWP apps]
Header
IoAPI.h (include Windows.h);
WinBase.h on Windows Server 2008 R2, Windows 7, Windows Server 2008, Windows Vista, Windows Server 2003 and Windows XP (include Windows.h)
Library
Kernel32.lib
DLL
Kernel32.dll

See also

CancelIoEx

CancelSynchronousIo

CreateFile

DeviceIoControl

File Management Functions

LockFileEx

ReadDirectoryChangesW

ReadFile

ReadFileEx

Synchronous and Asynchronous I/O

WriteFile

WriteFileEx