mm/damon/stat: monitor all System RAM resources

mm/damon/stat: monitor all System RAM resources

DAMON_STAT usage document (Documentation/admin-guide/mm/damon/stat.rst)
says it monitors the system's entire physical memory.  But, it is
monitoring only the biggest System RAM resource of the system.  When there
are multiple System RAM resources, this results in monitoring only an
unexpectedly small fraction of the physical memory.  For example, suppose
the system has a 500 GiB System RAM, 10 MiB non-System RAM, and 500 GiB
System RAM resources in order on the physical address space.  DAMON_STAT
will monitor only the first 500 GiB System RAM.  This situation is
particularly common on NUMA systems.

Select a physical address range that covers all System RAM areas of the
system, to fix this issue and make it work as documented.

[sj@kernel.org: return error if monitoring target region is invalid]
Link: https://lkml.kernel.org/r/20260317053631.87907-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20260316235118.873-1-sj@kernel.org
Fixes: 369c415e6073 ("mm/damon: introduce DAMON_STAT module")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[6.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>