mm/damon: fixup damos_filter kernel-doc

mm/damon: fixup damos_filter kernel-doc

Patch series "mm/damon: extend DAMOS filters for inclusion", v2.

DAMOS fitlers are exclusive filters.  It only excludes memory of given
criterias from the DAMOS action targets.  This has below limitations.

First, the name is not explicitly explaining the behavior.  This actually
resulted in users' confusions[1].  Secondly, combined uses of multiple
filters provide only restriced coverages.  For example, building a DAMOS
scheme that applies the action to memory that belongs to cgroup A "or"
cgroup B is impossible.  A workaround would be using two schemes that
fitlers out memory that not belong to cgroup A and cgroup B, respectively.
It is cumbersome, and difficult to control quota-like per-scheme features
in an orchestration.  Monitoring of filters-passed memory statistic will
also be complicated.

Extend DAMOS filters to support not only exclusion (rejecting), but also
inclusion (allowing) behavior.  For this, add a new damos_filter struct
field called 'allow' for DAMON kernel API users.  The filter works as an
inclusion or exclusion filter when it is set or unset, respectively.  For
DAMON user-space ABI users, add a DAMON sysfs file of same name under
DAMOS filter sysfs directory.  To prevent exposing a behavioral change to
old users, set rejecting as the default behavior.

Note that allow-filters work for only inclusion, not exclusion of memory
that not satisfying the criteria.  And the default behavior of DAMOS for
memory that no filter has involved is that the action can be applied to
those memory.  Also, filters-passed memory statistics are for any memory
that passed through the DAMOS filters check stage.  These implies
installing allow-filters at the endof the filter list is useless.  Refer
to the design doc change of this series for more details.

[1] https://lore.kernel.org/20240320165619.71478-1-sj@kernel.org

This patch (of 10):

The comment is slightly wrong.  DAMOS filters are not only for pages, but
general bytes of memory.  Also the description of 'matching' is bit
confusing, since DAMOS filters do only filtering out.  Update the comments
to be less confusing.

Link: https://lkml.kernel.org/r/20250109175126.57878-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250109175126.57878-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>