forcibly unmap pages in driver?

["Dan Maas" <dmaas@dcine.com>]

I am writing a device driver that, like many others, exposes a shared memory
region to user-space via mmap(). The region is allocated with vmalloc(), the
pages are marked reserved, and the user-space mapping is implemented with
remap_page_range().

In my driver, I may have to free the underlying vmalloc() region while the
user-space program is still running. I need to remove the user-space
mapping -- otherwise the user process would still have access to the
now-freed pages. I need an inverse of remap_page_range().

Is zap_page_range() the function I am looking for? Unfortunately it's not
exported to modules =(. As a quick fix, I was thinking I could just remap
all of the user pages to point to a zeroed page or something...

Another question- in the mm.c sources, I see that many of the memory-mapping
functions are surrounded by calls to flush_cache_range() and
flush_tlb_range(). But I don't see these calls in many drivers. Is it
necessary to make them when my driver maps or unmaps the shared memory
region?

Regards,
Dan