mm/damon: remove the target id concept

DAMON asks each monitoring target ('struct damon_target') to have one
'unsigned long' integer called 'id', which should be unique among the
targets of same monitoring context.  Meaning of it is, however, totally up
to the monitoring primitives that registered to the monitoring context.
For example, the virtual address spaces monitoring primitives treats the
id as a 'struct pid' pointer.

This makes the code flexible, but ugly, not well-documented, and
type-unsafe[1].  Also, identification of each target can be done via its
index.  For the reason, this commit removes the concept and uses clear
type definition.  For now, only 'struct pid' pointer is used for the
virtual address spaces monitoring.  If DAMON is extended in future so that
we need to put another identifier field in the struct, we will use a union
for such primitives-dependent fields and document which primitives are
using which type.

[1] https://lore.kernel.org/linux-mm/20211013154535.4aaeaaf9d0182922e405dd1e@linux-foundation.org/

Link: https://lkml.kernel.org/r/20211230100723.2238-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 10 deletions

diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
index 4a6141ddd6fc..b4085deb9fa0 100644
--- a/mm/damon/core-test.h
+++ b/mm/damon/core-test.h
@@ -24,7 +24,7 @@ static void damon_test_regions(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, 2ul, r->ar.end);
 	KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
 
-	t = damon_new_target(42);
+	t = damon_new_target();
 	KUNIT_EXPECT_EQ(test, 0u, damon_nr_regions(t));
 
 	damon_add_region(r, t);
@@ -52,8 +52,7 @@ static void damon_test_target(struct kunit *test)
 	struct damon_ctx *c = damon_new_ctx();
 	struct damon_target *t;
 
-	t = damon_new_target(42);
-	KUNIT_EXPECT_EQ(test, 42ul, t->id);
+	t = damon_new_target();
 	KUNIT_EXPECT_EQ(test, 0u, nr_damon_targets(c));
 
 	damon_add_target(c, t);
@@ -78,7 +77,6 @@ static void damon_test_target(struct kunit *test)
 static void damon_test_aggregate(struct kunit *test)
 {
 	struct damon_ctx *ctx = damon_new_ctx();
-	unsigned long target_ids[] = {1, 2, 3};
 	unsigned long saddr[][3] = {{10, 20, 30}, {5, 42, 49}, {13, 33, 55} };
 	unsigned long eaddr[][3] = {{15, 27, 40}, {31, 45, 55}, {23, 44, 66} };
 	unsigned long accesses[][3] = {{42, 95, 84}, {10, 20, 30}, {0, 1, 2} };
@@ -87,7 +85,7 @@ static void damon_test_aggregate(struct kunit *test)
 	int it, ir;
 
 	for (it = 0; it < 3; it++) {
-		t = damon_new_target(target_ids[it]);
+		t = damon_new_target();
 		damon_add_target(ctx, t);
 	}
 
@@ -125,7 +123,7 @@ static void damon_test_split_at(struct kunit *test)
 	struct damon_target *t;
 	struct damon_region *r;
 
-	t = damon_new_target(42);
+	t = damon_new_target();
 	r = damon_new_region(0, 100);
 	damon_add_region(r, t);
 	damon_split_region_at(c, t, r, 25);
@@ -146,7 +144,7 @@ static void damon_test_merge_two(struct kunit *test)
 	struct damon_region *r, *r2, *r3;
 	int i;
 
-	t = damon_new_target(42);
+	t = damon_new_target();
 	r = damon_new_region(0, 100);
 	r->nr_accesses = 10;
 	damon_add_region(r, t);
@@ -194,7 +192,7 @@ static void damon_test_merge_regions_of(struct kunit *test)
 	unsigned long eaddrs[] = {112, 130, 156, 170, 230};
 	int i;
 
-	t = damon_new_target(42);
+	t = damon_new_target();
 	for (i = 0; i < ARRAY_SIZE(sa); i++) {
 		r = damon_new_region(sa[i], ea[i]);
 		r->nr_accesses = nrs[i];
@@ -218,14 +216,14 @@ static void damon_test_split_regions_of(struct kunit *test)
 	struct damon_target *t;
 	struct damon_region *r;
 
-	t = damon_new_target(42);
+	t = damon_new_target();
 	r = damon_new_region(0, 22);
 	damon_add_region(r, t);
 	damon_split_regions_of(c, t, 2);
 	KUNIT_EXPECT_LE(test, damon_nr_regions(t), 2u);
 	damon_free_target(t);
 
-	t = damon_new_target(42);
+	t = damon_new_target();
 	r = damon_new_region(0, 220);
 	damon_add_region(r, t);
 	damon_split_regions_of(c, t, 4);