The attached patch implements strict VM overcommit on top of the rmap
VM.

The basis for this is Alan Cox's work in 2.4-ac.  This is a port of the
strict VM overcommit out of 2.4-ac and into the standard kernel with the
following changes:

	- one or two bugfixes (have sent/will send to Alan)
	- some cleanups, mostly for coding style
	- I did not bring over the debugging code
	- new overcommit policy for swapless machines

So what is strict VM overcommit?  We introduce new overcommit policies
that attempt to never succeed an allocation that can not be fulfilled by
the backing store and consequently never OOM.  This is achieved through
strict accounting of the committed address space and a policy to
allow/refuse allocations based on that accounting.

In the strictest of modes, it should be impossible to allocate more
memory than available and impossible to OOM.  All memory failures should
be pushed down to the allocation routines -- malloc, mmap, etc.

The new modes are available via sysctl (same as before).  See
Documentation/vm/overcommit-accounting for more information.

Again, Alan deserves the credit for the design of all this.

The patch is against 2.4.19-pre7-rmap13b but should apply to later
releases with little trouble.

Enjoy,

	Robert Love