[RFC PATCH v2 2/3] mm/damon/vaddr: do not split regions for min_nr_regions

[SeongJae Park <sj@kernel.org>]

The previous commit made DAMON core split regions at the beginning for
min_nr_regions.  The virtual address space operation set (vaddr) does
similar work on its own, for a case user delegates entire initial
monitoring regions setup to vaddr.  It is unnecessary now, as DAMON core
will do similar work for any case.  Remove the duplicated work in vaddr.

Also, remove a helper function that was being used only for the work,
and the test code of the helper function.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/tests/vaddr-kunit.h | 76 ------------------------------------
 mm/damon/vaddr.c             | 70 +--------------------------------
 2 files changed, 2 insertions(+), 144 deletions(-)

diff --git a/mm/damon/tests/vaddr-kunit.h b/mm/damon/tests/vaddr-kunit.h
index cfae870178bfd..98e734d77d517 100644
--- a/mm/damon/tests/vaddr-kunit.h
+++ b/mm/damon/tests/vaddr-kunit.h
@@ -252,88 +252,12 @@ static void damon_test_apply_three_regions4(struct kunit *test)
 			new_three_regions, expected, ARRAY_SIZE(expected));
 }
 
-static void damon_test_split_evenly_fail(struct kunit *test,
-		unsigned long start, unsigned long end, unsigned int nr_pieces)
-{
-	struct damon_target *t = damon_new_target();
-	struct damon_region *r;
-
-	if (!t)
-		kunit_skip(test, "target alloc fail");
-
-	r = damon_new_region(start, end);
-	if (!r) {
-		damon_free_target(t);
-		kunit_skip(test, "region alloc fail");
-	}
-
-	damon_add_region(r, t);
-	KUNIT_EXPECT_EQ(test,
-			damon_va_evenly_split_region(t, r, nr_pieces), -EINVAL);
-	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1u);
-
-	damon_for_each_region(r, t) {
-		KUNIT_EXPECT_EQ(test, r->ar.start, start);
-		KUNIT_EXPECT_EQ(test, r->ar.end, end);
-	}
-
-	damon_free_target(t);
-}
-
-static void damon_test_split_evenly_succ(struct kunit *test,
-	unsigned long start, unsigned long end, unsigned int nr_pieces)
-{
-	struct damon_target *t = damon_new_target();
-	struct damon_region *r;
-	unsigned long expected_width = (end - start) / nr_pieces;
-	unsigned long i = 0;
-
-	if (!t)
-		kunit_skip(test, "target alloc fail");
-	r = damon_new_region(start, end);
-	if (!r) {
-		damon_free_target(t);
-		kunit_skip(test, "region alloc fail");
-	}
-	damon_add_region(r, t);
-	KUNIT_EXPECT_EQ(test,
-			damon_va_evenly_split_region(t, r, nr_pieces), 0);
-	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), nr_pieces);
-
-	damon_for_each_region(r, t) {
-		if (i == nr_pieces - 1) {
-			KUNIT_EXPECT_EQ(test,
-				r->ar.start, start + i * expected_width);
-			KUNIT_EXPECT_EQ(test, r->ar.end, end);
-			break;
-		}
-		KUNIT_EXPECT_EQ(test,
-				r->ar.start, start + i++ * expected_width);
-		KUNIT_EXPECT_EQ(test, r->ar.end, start + i * expected_width);
-	}
-	damon_free_target(t);
-}
-
-static void damon_test_split_evenly(struct kunit *test)
-{
-	KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(NULL, NULL, 5),
-			-EINVAL);
-
-	damon_test_split_evenly_fail(test, 0, 100, 0);
-	damon_test_split_evenly_succ(test, 0, 100, 10);
-	damon_test_split_evenly_succ(test, 5, 59, 5);
-	damon_test_split_evenly_succ(test, 4, 6, 1);
-	damon_test_split_evenly_succ(test, 0, 3, 2);
-	damon_test_split_evenly_fail(test, 5, 6, 2);
-}
-
 static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_three_regions_in_vmas),
 	KUNIT_CASE(damon_test_apply_three_regions1),
 	KUNIT_CASE(damon_test_apply_three_regions2),
 	KUNIT_CASE(damon_test_apply_three_regions3),
 	KUNIT_CASE(damon_test_apply_three_regions4),
-	KUNIT_CASE(damon_test_split_evenly),
 	{},
 };
 
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 4e3430d4191d1..400247d96eecc 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -53,52 +53,6 @@ static struct mm_struct *damon_get_mm(struct damon_target *t)
 	return mm;
 }
 
-/*
- * Functions for the initial monitoring target regions construction
- */
-
-/*
- * Size-evenly split a region into 'nr_pieces' small regions
- *
- * Returns 0 on success, or negative error code otherwise.
- */
-static int damon_va_evenly_split_region(struct damon_target *t,
-		struct damon_region *r, unsigned int nr_pieces)
-{
-	unsigned long sz_orig, sz_piece, orig_end;
-	struct damon_region *n = NULL, *next;
-	unsigned long start;
-	unsigned int i;
-
-	if (!r || !nr_pieces)
-		return -EINVAL;
-
-	if (nr_pieces == 1)
-		return 0;
-
-	orig_end = r->ar.end;
-	sz_orig = damon_sz_region(r);
-	sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, DAMON_MIN_REGION_SZ);
-
-	if (!sz_piece)
-		return -EINVAL;
-
-	r->ar.end = r->ar.start + sz_piece;
-	next = damon_next_region(r);
-	for (start = r->ar.end, i = 1; i < nr_pieces; start += sz_piece, i++) {
-		n = damon_new_region(start, start + sz_piece);
-		if (!n)
-			return -ENOMEM;
-		damon_insert_region(n, r, next, t);
-		r = n;
-	}
-	/* complement last region for possible rounding error */
-	if (n)
-		n->ar.end = orig_end;
-
-	return 0;
-}
-
 static unsigned long sz_range(struct damon_addr_range *r)
 {
 	return r->end - r->start;
@@ -240,10 +194,8 @@ static void __damon_va_init_regions(struct damon_ctx *ctx,
 				     struct damon_target *t)
 {
 	struct damon_target *ti;
-	struct damon_region *r;
 	struct damon_addr_range regions[3];
-	unsigned long sz = 0, nr_pieces;
-	int i, tidx = 0;
+	int tidx = 0;
 
 	if (damon_va_three_regions(t, regions)) {
 		damon_for_each_target(ti, ctx) {
@@ -255,25 +207,7 @@ static void __damon_va_init_regions(struct damon_ctx *ctx,
 		return;
 	}
 
-	for (i = 0; i < 3; i++)
-		sz += regions[i].end - regions[i].start;
-	if (ctx->attrs.min_nr_regions)
-		sz /= ctx->attrs.min_nr_regions;
-	if (sz < DAMON_MIN_REGION_SZ)
-		sz = DAMON_MIN_REGION_SZ;
-
-	/* Set the initial three regions of the target */
-	for (i = 0; i < 3; i++) {
-		r = damon_new_region(regions[i].start, regions[i].end);
-		if (!r) {
-			pr_err("%d'th init region creation failed\n", i);
-			return;
-		}
-		damon_add_region(r, t);
-
-		nr_pieces = (regions[i].end - regions[i].start) / sz;
-		damon_va_evenly_split_region(t, r, nr_pieces);
-	}
+	damon_set_regions(t, regions, 3, DAMON_MIN_REGION_SZ);
 }
 
 /* Initialize '->regions_list' of every target (task) */
-- 
2.47.3