[PATCH v2 00/10] mm/damon: extend DAMOS filters for inclusion

[PATCH v2 00/10] mm/damon: extend DAMOS filters for inclusion

[SeongJae Park]

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

Revision History
================

Changes from v1
(https://lore.kernel.org/20250107201739.79484-1-sj@kernel.org)
- Correct wrong comments and documents about pass filters without
  successing block filters
- Rename 'pass/block' to 'allow/reject'
  (to avoid confusion with sz_[ops]_filter_pass)

Changes from RFC v2
(https://lore.kernel.org/20241227210819.63776-1-sj@kernel.org)
- Wordsmith messages
- Wordsmith design documentation about monitoring-purpose usage
- Rebase on latest mm-unstable

Changes from RFC v1
(https://lore.kernel.org/20241226221445.78433-1-sj@kernel.org)
- Fix encoding issue on the last patch

SeongJae Park (10):
  mm/damon: fixup damos_filter kernel-doc
  mm/damon/core: add damos_filter->allow field
  mm/damon/core: support damos_filter->allow
  mm/damon/paddr: support damos_filter->allow
  mm/damon: add 'allow' argument to damos_new_filter()
  mm/damon/sysfs-schemes: add a file for setting damos_filter->allow
  Docs/mm/damon/design: document allow/reject DAMOS filter behaviors
  Docs/ABI/damon: document DAMOS filter allow sysfs file
  Docs/admin-guide/mm/damon/usage: omit DAMOS filter details in favor of
    design doc
  Docs/admin-guide/mm/damon/usage: document DAMOS filter 'allow' sysfs
    file

 .../ABI/testing/sysfs-kernel-mm-damon         | 13 +++--
 Documentation/admin-guide/mm/damon/usage.rst  | 54 ++++++++++---------
 Documentation/mm/damon/design.rst             | 33 ++++++++++--
 include/linux/damon.h                         | 15 +++---
 mm/damon/core.c                               | 12 +++--
 mm/damon/paddr.c                              |  9 ++--
 mm/damon/reclaim.c                            |  2 +-
 mm/damon/sysfs-schemes.c                      | 32 ++++++++++-
 mm/damon/tests/core-kunit.h                   | 14 ++---
 9 files changed, 127 insertions(+), 57 deletions(-)

-- 
2.39.5

[PATCH v2 01/10] mm/damon: fixup damos_filter kernel-doc

[SeongJae Park]

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.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 298b1a831e62..72afba74ac6d 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -347,8 +347,8 @@ enum damos_filter_type {
 
 /**
  * struct damos_filter - DAMOS action target memory filter.
- * @type:	Type of the page.
- * @matching:	If the matching page should filtered out or in.
+ * @type:	Type of the target memory.
+ * @matching:	If the @type-matching memory should be filtered out.
  * @memcg_id:	Memcg id of the question if @type is DAMOS_FILTER_MEMCG.
  * @addr_range:	Address range if @type is DAMOS_FILTER_TYPE_ADDR.
  * @target_idx:	Index of the &struct damon_target of
@@ -357,9 +357,10 @@ enum damos_filter_type {
  * @list:	List head for siblings.
  *
  * Before applying the &damos->action to a memory region, DAMOS checks if each
- * page of the region matches to this and avoid applying the action if so.
- * Support of each filter type depends on the running &struct damon_operations
- * and the type.  Refer to &enum damos_filter_type for more detai.
+ * byte of the region matches to this given condition and avoid applying the
+ * action if so.  Support of each filter type depends on the running &struct
+ * damon_operations and the type.  Refer to &enum damos_filter_type for more
+ * details.
  */
 struct damos_filter {
 	enum damos_filter_type type;
-- 
2.39.5

[PATCH v2 02/10] mm/damon/core: add damos_filter->allow field

[SeongJae Park]

DAMOS filters work as only exclusive (reject) filters.  This makes it
easy to be confused, and restrictive at combining multiple filters for
covering various types of memory.

Add a field named 'allow' to damos_filter.  The field will be used to
indicate whether the filter should work for inclusion or exclusion.  To
keep the old behavior, set it as 'false' (work as exclusive filter) by
default, from damos_new_filter().

Following two commits will make the core and operations set layers,
which handles damos_filter objects, respect the field, respectively.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 4 +++-
 mm/damon/core.c       | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 72afba74ac6d..8a2d104df5a3 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -348,7 +348,8 @@ enum damos_filter_type {
 /**
  * struct damos_filter - DAMOS action target memory filter.
  * @type:	Type of the target memory.
- * @matching:	If the @type-matching memory should be filtered out.
+ * @matching:	Whether this is for @type-matching memory.
+ * @allow:	Whether to include or exclude the @matching memory.
  * @memcg_id:	Memcg id of the question if @type is DAMOS_FILTER_MEMCG.
  * @addr_range:	Address range if @type is DAMOS_FILTER_TYPE_ADDR.
  * @target_idx:	Index of the &struct damon_target of
@@ -365,6 +366,7 @@ enum damos_filter_type {
 struct damos_filter {
 	enum damos_filter_type type;
 	bool matching;
+	bool allow;
 	union {
 		unsigned short memcg_id;
 		struct damon_addr_range addr_range;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 52e50f183ffe..bdde532ebbc8 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -275,6 +275,7 @@ struct damos_filter *damos_new_filter(enum damos_filter_type type,
 		return NULL;
 	filter->type = type;
 	filter->matching = matching;
+	filter->allow = false;
 	INIT_LIST_HEAD(&filter->list);
 	return filter;
 }
-- 
2.39.5

[PATCH v2 03/10] mm/damon/core: support damos_filter->allow

[SeongJae Park]

DAMOS filters supports allowing behavior, but the core layer's DAMOS
filters handling logic still assumes only rejecting (filtering-out)
behavior.  Update the logic to aware of and respect the behavioral
decision by reading damos_filter->allow when making the decision to
exclude a region or not.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core.c             |  6 +++---
 mm/damon/tests/core-kunit.h | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index bdde532ebbc8..76707b0635d6 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1374,7 +1374,7 @@ static void damos_update_stat(struct damos *s,
 	s->stat.sz_ops_filter_passed += sz_ops_filter_passed;
 }
 
-static bool __damos_filter_out(struct damon_ctx *ctx, struct damon_target *t,
+static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t,
 		struct damon_region *r, struct damos_filter *filter)
 {
 	bool matched = false;
@@ -1428,8 +1428,8 @@ static bool damos_filter_out(struct damon_ctx *ctx, struct damon_target *t,
 	struct damos_filter *filter;
 
 	damos_for_each_filter(filter, s) {
-		if (__damos_filter_out(ctx, t, r, filter))
-			return true;
+		if (damos_filter_match(ctx, t, r, filter))
+			return !filter->allow;
 	}
 	return false;
 }
diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index cf22e09a3507..8f58d3424c21 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -434,25 +434,25 @@ static void damos_test_filter_out(struct kunit *test)
 	damon_add_region(r, t);
 
 	/* region in the range */
-	KUNIT_EXPECT_TRUE(test, __damos_filter_out(NULL, t, r, f));
+	KUNIT_EXPECT_TRUE(test, damos_filter_match(NULL, t, r, f));
 	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1);
 
 	/* region before the range */
 	r->ar.start = DAMON_MIN_REGION * 1;
 	r->ar.end = DAMON_MIN_REGION * 2;
-	KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f));
+	KUNIT_EXPECT_FALSE(test, damos_filter_match(NULL, t, r, f));
 	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1);
 
 	/* region after the range */
 	r->ar.start = DAMON_MIN_REGION * 6;
 	r->ar.end = DAMON_MIN_REGION * 8;
-	KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f));
+	KUNIT_EXPECT_FALSE(test, damos_filter_match(NULL, t, r, f));
 	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1);
 
 	/* region started before the range */
 	r->ar.start = DAMON_MIN_REGION * 1;
 	r->ar.end = DAMON_MIN_REGION * 4;
-	KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f));
+	KUNIT_EXPECT_FALSE(test, damos_filter_match(NULL, t, r, f));
 	/* filter should have split the region */
 	KUNIT_EXPECT_EQ(test, r->ar.start, DAMON_MIN_REGION * 1);
 	KUNIT_EXPECT_EQ(test, r->ar.end, DAMON_MIN_REGION * 2);
@@ -465,7 +465,7 @@ static void damos_test_filter_out(struct kunit *test)
 	/* region started in the range */
 	r->ar.start = DAMON_MIN_REGION * 2;
 	r->ar.end = DAMON_MIN_REGION * 8;
-	KUNIT_EXPECT_TRUE(test, __damos_filter_out(NULL, t, r, f));
+	KUNIT_EXPECT_TRUE(test, damos_filter_match(NULL, t, r, f));
 	/* filter should have split the region */
 	KUNIT_EXPECT_EQ(test, r->ar.start, DAMON_MIN_REGION * 2);
 	KUNIT_EXPECT_EQ(test, r->ar.end, DAMON_MIN_REGION * 6);
-- 
2.39.5

[PATCH v2 04/10] mm/damon/paddr: support damos_filter->allow

[SeongJae Park]

Respect damos_filter->allow from 'paddr', which is a DAMON operations
set implementation for the physical address space and supports a few
types of region-internal DAMOS filters (anon, memcg and young).  The
change is similar to that of the previous commit for core layer update.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/paddr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index b0c283808ba6..817acfd4f8a2 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -198,7 +198,7 @@ static unsigned int damon_pa_check_accesses(struct damon_ctx *ctx)
 	return max_nr_accesses;
 }
 
-static bool __damos_pa_filter_out(struct damos_filter *filter,
+static bool damos_pa_filter_match(struct damos_filter *filter,
 		struct folio *folio)
 {
 	bool matched = false;
@@ -237,8 +237,8 @@ static bool damos_pa_filter_out(struct damos *scheme, struct folio *folio)
 	struct damos_filter *filter;
 
 	damos_for_each_filter(filter, scheme) {
-		if (__damos_pa_filter_out(filter, folio))
-			return true;
+		if (damos_pa_filter_match(filter, folio))
+			return !filter->allow;
 	}
 	return false;
 }
-- 
2.39.5

[PATCH v2 05/10] mm/damon: add 'allow' argument to damos_new_filter()

[SeongJae Park]

DAMON API users should set damos_filter->allow manually to use a DAMOS
allow-filter, since damos_new_filter() unsets the field always.  It is
cumbersome and easy to mistake.  Add an arugment for setting the field
to damos_new_filter().

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h       | 2 +-
 mm/damon/core.c             | 7 ++++---
 mm/damon/paddr.c            | 3 ++-
 mm/damon/reclaim.c          | 2 +-
 mm/damon/sysfs-schemes.c    | 2 +-
 mm/damon/tests/core-kunit.h | 4 ++--
 6 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 8a2d104df5a3..0834d7ffcb84 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -801,7 +801,7 @@ void damon_update_region_access_rate(struct damon_region *r, bool accessed,
 		struct damon_attrs *attrs);
 
 struct damos_filter *damos_new_filter(enum damos_filter_type type,
-		bool matching);
+		bool matching, bool allow);
 void damos_add_filter(struct damos *s, struct damos_filter *f);
 void damos_destroy_filter(struct damos_filter *f);
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 76707b0635d6..55a435bdd89d 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -266,7 +266,7 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges,
 }
 
 struct damos_filter *damos_new_filter(enum damos_filter_type type,
-		bool matching)
+		bool matching, bool allow)
 {
 	struct damos_filter *filter;
 
@@ -275,7 +275,7 @@ struct damos_filter *damos_new_filter(enum damos_filter_type type,
 		return NULL;
 	filter->type = type;
 	filter->matching = matching;
-	filter->allow = false;
+	filter->allow = allow;
 	INIT_LIST_HEAD(&filter->list);
 	return filter;
 }
@@ -806,7 +806,8 @@ static int damos_commit_filters(struct damos *dst, struct damos *src)
 			continue;
 
 		new_filter = damos_new_filter(
-				src_filter->type, src_filter->matching);
+				src_filter->type, src_filter->matching,
+				src_filter->allow);
 		if (!new_filter)
 			return -ENOMEM;
 		damos_commit_filter_arg(new_filter, src_filter);
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 817acfd4f8a2..6b4397de4199 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -259,7 +259,8 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
 		}
 	}
 	if (install_young_filter) {
-		filter = damos_new_filter(DAMOS_FILTER_TYPE_YOUNG, true);
+		filter = damos_new_filter(
+				DAMOS_FILTER_TYPE_YOUNG, true, false);
 		if (!filter)
 			return 0;
 		damos_add_filter(s, filter);
diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 9e0077a9404e..a675150965e0 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -221,7 +221,7 @@ static int damon_reclaim_apply_parameters(void)
 	}
 
 	if (skip_anon) {
-		filter = damos_new_filter(DAMOS_FILTER_TYPE_ANON, true);
+		filter = damos_new_filter(DAMOS_FILTER_TYPE_ANON, true, false);
 		if (!filter)
 			goto out;
 		damos_add_filter(scheme, filter);
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index deeaf23c1fcf..9a883e8aea1c 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1901,7 +1901,7 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
 			sysfs_filters->filters_arr[i];
 		struct damos_filter *filter =
 			damos_new_filter(sysfs_filter->type,
-					sysfs_filter->matching);
+					sysfs_filter->matching, false);
 		int err;
 
 		if (!filter)
diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 8f58d3424c21..532c6a6f21f9 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -411,7 +411,7 @@ static void damos_test_new_filter(struct kunit *test)
 {
 	struct damos_filter *filter;
 
-	filter = damos_new_filter(DAMOS_FILTER_TYPE_ANON, true);
+	filter = damos_new_filter(DAMOS_FILTER_TYPE_ANON, true, false);
 	KUNIT_EXPECT_EQ(test, filter->type, DAMOS_FILTER_TYPE_ANON);
 	KUNIT_EXPECT_EQ(test, filter->matching, true);
 	KUNIT_EXPECT_PTR_EQ(test, filter->list.prev, &filter->list);
@@ -425,7 +425,7 @@ static void damos_test_filter_out(struct kunit *test)
 	struct damon_region *r, *r2;
 	struct damos_filter *f;
 
-	f = damos_new_filter(DAMOS_FILTER_TYPE_ADDR, true);
+	f = damos_new_filter(DAMOS_FILTER_TYPE_ADDR, true, false);
 	f->addr_range = (struct damon_addr_range){
 		.start = DAMON_MIN_REGION * 2, .end = DAMON_MIN_REGION * 6};
 
-- 
2.39.5

[PATCH v2 06/10] mm/damon/sysfs-schemes: add a file for setting damos_filter->allow

[SeongJae Park]

Only kernel-space DAMON API users can use inclusive DAMOS filters.  Add
a sysfs file named 'allow' under DAMOS filter directory of DAMON sysfs
interface, to let the user-space users use inclusive DAMOS filters.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 9a883e8aea1c..98f93ae9f59e 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -313,6 +313,7 @@ struct damon_sysfs_scheme_filter {
 	struct kobject kobj;
 	enum damos_filter_type type;
 	bool matching;
+	bool allow;
 	char *memcg_path;
 	struct damon_addr_range addr_range;
 	int target_idx;
@@ -385,6 +386,30 @@ static ssize_t matching_store(struct kobject *kobj,
 	return count;
 }
 
+static ssize_t allow_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
+			struct damon_sysfs_scheme_filter, kobj);
+
+	return sysfs_emit(buf, "%c\n", filter->allow ? 'Y' : 'N');
+}
+
+static ssize_t allow_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
+			struct damon_sysfs_scheme_filter, kobj);
+	bool allow;
+	int err = kstrtobool(buf, &allow);
+
+	if (err)
+		return err;
+
+	filter->allow = allow;
+	return count;
+}
+
 static ssize_t memcg_path_show(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
@@ -482,6 +507,9 @@ static struct kobj_attribute damon_sysfs_scheme_filter_type_attr =
 static struct kobj_attribute damon_sysfs_scheme_filter_matching_attr =
 		__ATTR_RW_MODE(matching, 0600);
 
+static struct kobj_attribute damon_sysfs_scheme_filter_allow_attr =
+		__ATTR_RW_MODE(allow, 0600);
+
 static struct kobj_attribute damon_sysfs_scheme_filter_memcg_path_attr =
 		__ATTR_RW_MODE(memcg_path, 0600);
 
@@ -497,6 +525,7 @@ static struct kobj_attribute damon_sysfs_scheme_filter_damon_target_idx_attr =
 static struct attribute *damon_sysfs_scheme_filter_attrs[] = {
 	&damon_sysfs_scheme_filter_type_attr.attr,
 	&damon_sysfs_scheme_filter_matching_attr.attr,
+	&damon_sysfs_scheme_filter_allow_attr.attr,
 	&damon_sysfs_scheme_filter_memcg_path_attr.attr,
 	&damon_sysfs_scheme_filter_addr_start_attr.attr,
 	&damon_sysfs_scheme_filter_addr_end_attr.attr,
@@ -1901,7 +1930,8 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
 			sysfs_filters->filters_arr[i];
 		struct damos_filter *filter =
 			damos_new_filter(sysfs_filter->type,
-					sysfs_filter->matching, false);
+					sysfs_filter->matching,
+					sysfs_filter->allow);
 		int err;
 
 		if (!filter)
-- 
2.39.5

[PATCH v2 07/10] Docs/mm/damon/design: document allow/reject DAMOS filter behaviors

[SeongJae Park]

Update DAMOS filters design document to describe the allow/reject
behavior of filters.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 33 +++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 449eb33688c2..667775bab86c 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -504,9 +504,34 @@ have a list of latency-critical processes.
 
 To let users optimize DAMOS schemes with such special knowledge, DAMOS provides
 a feature called DAMOS filters.  The feature allows users to set an arbitrary
-number of filters for each scheme.  Each filter specifies the type of target
-memory, and whether it should exclude the memory of the type (filter-out), or
-all except the memory of the type (filter-in).
+number of filters for each scheme.  Each filter specifies
+
+- a type of memory (``type``),
+- whether it is for the memory of the type or all except the type
+  (``matching``), and
+- whether it is to allow (include) or reject (exclude) applying
+  the scheme's action to the memory (``allow``).
+
+When multiple filters are installed, each filter is evaluated in the installed
+order.  If a part of memory is matched to one of the filter, next filters are
+ignored.  If the memory passes through the filters evaluation stage because it
+is not matched to any of the filters, applying the scheme's action to it is
+allowed, same to the behavior when no filter exists.
+
+For example, let's assume 1) a filter for allowing anonymous pages and 2)
+another filter for rejecting young pages are installed in the order.  If a page
+of a region that eligible to apply the scheme's action is an anonymous page,
+the scheme's action will be applied to the page regardless of whether it is
+young or not, since it matches with the first allow-filter.  If the page is
+not anonymous but young, the scheme's action will not be applied, since the
+second reject-filter blocks it.  If the page is neither anonymous nor young,
+the page will pass through the filters evaluation stage since there is no
+matching filter, and the action will be applied to the page.
+
+Note that the action can equally be applied to memory that either explicitly
+filter-allowed or filters evaluation stage passed.  It means that installing
+allow-filters at the end of the list makes no practical change but only
+filters-checking overhead.
 
 For efficient handling of filters, some types of filters are handled by the
 core layer, while others are handled by operations set.  In the latter case,
@@ -516,7 +541,7 @@ filter are not counted as the scheme has tried to the region.  In contrast, if
 a memory regions is filtered by an operations set layer-handled filter, it is
 counted as the scheme has tried.  This difference affects the statistics.
 
-Below types of filters are currently supported.
+Below ``type`` of filters are currently supported.
 
 - anonymous page
     - Applied to pages that containing data that not stored in files.
-- 
2.39.5

[PATCH v2 08/10] Docs/ABI/damon: document DAMOS filter allow sysfs file

[SeongJae Park]

Update DAMON ABI document for added DAMOS filter 'allow' file.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/ABI/testing/sysfs-kernel-mm-damon | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-damon b/Documentation/ABI/testing/sysfs-kernel-mm-damon
index 8c0acb31638b..b057eddefbfc 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-damon
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-damon
@@ -355,10 +355,15 @@ Description:	If 'target' is written to the 'type' file, writing to or
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/filters/<F>/matching
 Date:		Dec 2022
 Contact:	SeongJae Park <sj@kernel.org>
-Description:	Writing 'Y' or 'N' to this file sets whether to filter out
-		pages that do or do not match to the 'type' and 'memcg_path',
-		respectively.  Filter out means the action of the scheme will
-		not be applied to.
+Description:	Writing 'Y' or 'N' to this file sets whether the filter is for
+		the memory of the 'type', or all except the 'type'.
+
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/filters/<F>/allow
+Date:		Jan 2025
+Contact:	SeongJae Park <sj@kernel.org>
+Description:	Writing 'Y' or 'N' to this file sets whether to allow or reject
+		applying the scheme's action to the memory that satisfies the
+		'type' and the 'matching' of the directory.
 
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/stats/nr_tried
 Date:		Mar 2022
-- 
2.39.5

[PATCH v2 09/10] Docs/admin-guide/mm/damon/usage: omit DAMOS filter details in favor of design doc

[SeongJae Park]

DAMON usage document is describing some details about DAMOS filters,
which are also documented on the design doc.  Deduplicate the details in
favor of the design doc.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 29 ++++++++++----------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 71cf29ae8502..8df3357dcfa3 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -411,13 +411,17 @@ Each filter directory contains six files, namely ``type``, ``matcing``,
 file, you can write one of five special keywords: ``anon`` for anonymous pages,
 ``memcg`` for specific memory cgroup, ``young`` for young pages, ``addr`` for
 specific address range (an open-ended interval), or ``target`` for specific
-DAMON monitoring target filtering.  In case of the memory cgroup filtering, you
-can specify the memory cgroup of the interest by writing the path of the memory
-cgroup from the cgroups mount point to ``memcg_path`` file.  In case of the
-address range filtering, you can specify the start and end address of the range
-to ``addr_start`` and ``addr_end`` files, respectively.  For the DAMON
-monitoring target filtering, you can specify the index of the target between
-the list of the DAMON context's monitoring targets list to ``target_idx`` file.
+DAMON monitoring target filtering.  Meaning of the types are same to the
+description on the :ref:`design doc <damon_design_damos_filters>`.
+
+In case of the memory cgroup filtering, you can specify the memory cgroup of
+the interest by writing the path of the memory cgroup from the cgroups mount
+point to ``memcg_path`` file.  In case of the address range filtering, you can
+specify the start and end address of the range to ``addr_start`` and
+``addr_end`` files, respectively.  For the DAMON monitoring target filtering,
+you can specify the index of the target between the list of the DAMON context's
+monitoring targets list to ``target_idx`` file.
+
 You can write ``Y`` or ``N`` to ``matching`` file to filter out pages that does
 or does not match to the type, respectively.  Then, the scheme's action will
 not be applied to the pages that specified to be filtered out.
@@ -434,14 +438,9 @@ pages of all memory cgroups except ``/having_care_already``.::
     echo /having_care_already > 1/memcg_path
     echo Y > 1/matching
 
-Note that ``anon`` and ``memcg`` filters are currently supported only when
-``paddr`` :ref:`implementation <sysfs_context>` is being used.
-
-Also, memory regions that are filtered out by ``addr`` or ``target`` filters
-are not counted as the scheme has tried to those, while regions that filtered
-out by other type filters are counted as the scheme has tried to.  The
-difference is applied to :ref:`stats <damos_stats>` and
-:ref:`tried regions <sysfs_schemes_tried_regions>`.
+Refer to the :ref:`DAMOS filters design documentation
+<damon_design_damos_filters>` for more details including when each of the
+filters are supported and differences on stats.
 
 .. _sysfs_schemes_stats:
 
-- 
2.39.5

[PATCH v2 10/10] Docs/admin-guide/mm/damon/usage: document DAMOS filter 'allow' sysfs file

[SeongJae Park]

Update DAMON usage document for the newly added 'allow' sysfs file for
DAMOS filters.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 33 +++++++++++---------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 8df3357dcfa3..f0d0c20711d6 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -83,7 +83,7 @@ comma (",").
     │ │ │ │ │ │ │ │ │ 0/target_metric,target_value,current_value
     │ │ │ │ │ │ │ :ref:`watermarks <sysfs_watermarks>`/metric,interval_us,high,mid,low
     │ │ │ │ │ │ │ :ref:`filters <sysfs_filters>`/nr_filters
-    │ │ │ │ │ │ │ │ 0/type,matching,memcg_id
+    │ │ │ │ │ │ │ │ 0/type,matching,memcg_id,allow
     │ │ │ │ │ │ │ :ref:`stats <sysfs_schemes_stats>`/nr_tried,sz_tried,nr_applied,sz_applied,sz_ops_filter_passed,qt_exceeds
     │ │ │ │ │ │ │ :ref:`tried_regions <sysfs_schemes_tried_regions>`/total_bytes
     │ │ │ │ │ │ │ │ 0/start,end,nr_accesses,age,sz_filter_passed
@@ -406,13 +406,14 @@ number (``N``) to the file creates the number of child directories named ``0``
 to ``N-1``.  Each directory represents each filter.  The filters are evaluated
 in the numeric order.
 
-Each filter directory contains six files, namely ``type``, ``matcing``,
-``memcg_path``, ``addr_start``, ``addr_end``, and ``target_idx``.  To ``type``
-file, you can write one of five special keywords: ``anon`` for anonymous pages,
-``memcg`` for specific memory cgroup, ``young`` for young pages, ``addr`` for
-specific address range (an open-ended interval), or ``target`` for specific
-DAMON monitoring target filtering.  Meaning of the types are same to the
-description on the :ref:`design doc <damon_design_damos_filters>`.
+Each filter directory contains seven files, namely ``type``, ``matching``,
+``allow``, ``memcg_path``, ``addr_start``, ``addr_end``, and ``target_idx``.
+To ``type`` file, you can write one of five special keywords: ``anon`` for
+anonymous pages, ``memcg`` for specific memory cgroup, ``young`` for young
+pages, ``addr`` for specific address range (an open-ended interval), or
+``target`` for specific DAMON monitoring target filtering.  Meaning of the
+types are same to the description on the :ref:`design doc
+<damon_design_damos_filters>`.
 
 In case of the memory cgroup filtering, you can specify the memory cgroup of
 the interest by writing the path of the memory cgroup from the cgroups mount
@@ -422,25 +423,29 @@ specify the start and end address of the range to ``addr_start`` and
 you can specify the index of the target between the list of the DAMON context's
 monitoring targets list to ``target_idx`` file.
 
-You can write ``Y`` or ``N`` to ``matching`` file to filter out pages that does
-or does not match to the type, respectively.  Then, the scheme's action will
-not be applied to the pages that specified to be filtered out.
+You can write ``Y`` or ``N`` to ``matching`` file to specify whether the filter
+is for memory that matches the ``type``.  You can write ``Y`` or ``N`` to
+``allow`` file to specify if applying the action to the memory that satisfies
+the ``type`` and ``matching`` should be allowed or not.
 
 For example, below restricts a DAMOS action to be applied to only non-anonymous
 pages of all memory cgroups except ``/having_care_already``.::
 
     # echo 2 > nr_filters
-    # # filter out anonymous pages
+    # # disallow anonymous pages
     echo anon > 0/type
     echo Y > 0/matching
+    echo N > 0/allow
     # # further filter out all cgroups except one at '/having_care_already'
     echo memcg > 1/type
     echo /having_care_already > 1/memcg_path
     echo Y > 1/matching
+    echo N > 1/allow
 
 Refer to the :ref:`DAMOS filters design documentation
-<damon_design_damos_filters>` for more details including when each of the
-filters are supported and differences on stats.
+<damon_design_damos_filters>` for more details including how multiple filters
+of different ``allow`` works, when each of the filters are supported, and
+differences on stats.
 
 .. _sysfs_schemes_stats:
 
-- 
2.39.5