mm/damon/lru_sort: support addr_unit for DAMON_LRU_SORT

Patch series "mm/damon: add addr_unit for DAMON_LRU_SORT and
DAMON_RECLAIM".

In DAMON_LRU_SORT and DAMON_RECLAIM, damon_ctx is independent of the core.
Add addr_unit to these modules to support systems like ARM32 with LPAE.


This patch (of 2):

Implement a sysfs file to expose addr_unit for DAMON_LRU_SORT users. 
During parameter application, use the configured addr_unit parameter to
perform the necessary initialization.  Similar to the core layer, prevent
setting addr_unit to zero.

It is worth noting that when monitor_region_start and monitor_region_end
are unset (i.e., 0), their values will later be set to biggest_system_ram.
At that point, addr_unit may not be the default value 1.  Although we
could divide the biggest_system_ram value by addr_unit, changing addr_unit
without setting monitor_region_start/end should be considered a user
misoperation.  And biggest_system_ram is only within the 0~ULONG_MAX
range, system can clearly work correctly with addr_unit=1.  Therefore, if
monitor_region_start/end are unset, always silently reset addr_unit to 1.

Link: https://lkml.kernel.org/r/20250910113221.1065764-1-yanquanmin1@huawei.com
Link: https://lkml.kernel.org/r/20250910113221.1065764-2-yanquanmin1@huawei.com


Signed-off-by: Quanmin Yan <yanquanmin1@huawei.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: ze zuo <zuoze1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>