Wdk FAQ : [FLTFL_OPERATION_REGISTRATION_SKIP_PAGING_IO] Why is this flag used here? (minifilter)

original url from : http://www.osronline.com/showthread.cfm?link=238116

Q:

Below is the registration structure:CONST FLT_OPERATION_REGISTRATION Callbacks[] = {{ IRP_MJ_CREATE,  0,  SfPreCreateCallback,  SfPostCreateCallback },{ IRP_MJ_SET_INFORMATION,         FLTFL_OPERATION_REGISTRATION_SKIP_PAGING_IO,         SfPreSetInfoCallback,         SfPostSetInfoCallback },     { IRP_MJ_CLEANUP,         0,        SfPreCleanupCallback,         SfPostCleanupCallback },{ IRP_MJ_OPERATION_END }};

Now, my questions are,


-why the filter has been setup to ignore PAGING IO in the  
IRP_MJ_SET_INFORMATION?
-similarly, why has the PAGING IO not been ignored in the IRP_MJ_CREATE  
and IRP_MJ_SET_INFORMATION?

A:

The paging I/O operations in the set information path change the file sizes.  
Those cannot matter for deletion detection.


There are no paging I/O operations for create or cleanup.


The four operations that support paging I/O operations are: read, write, query 
information and set information.