In GPFS, a read event or a write event will be generated (if enabled) at the time the memory mapping of a file is established. No events will be generated during actual mapped access, regardless of the setting of the event list or the managed regions. Access to the file via regular file operations, while the file is memory mapped, will generate events, if such events are enabled.
To protect the integrity of memory mapped access, the DM application is not permitted to punch a hole in a file while the file is memory mapped. If the DM application calls dm_punch_hole while the file is memory mapped, the error code EBUSY will be returned.