[PATCH v3 1/2] mm/damon/core-test: Fix memory leak in damon_new_region()

[Jinjie Ruan <ruanjinjie@xxxxxxxxxx>]

When CONFIG_DAMON_KUNIT_TEST=y and making CONFIG_DEBUG_KMEMLEAK=y
and CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=y, the below memory leak is detected.

The damon_region which is allocated by kmem_cache_alloc() in
damon_new_region() in damon_test_regions() and
damon_test_update_monitoring_result() are not freed.

So for damon_test_regions(), replace damon_del_region() call with
damon_destroy_region() so that it calls both damon_del_region() and
damon_free_region(), the latter will free the damon_region. For
damon_test_update_monitoring_result(), call damon_free_region() to
free it. After applying this patch, the following memory leak is never
detected.

    unreferenced object 0xffff2b49c3edc000 (size 56):
      comm "kunit_try_catch", pid 338, jiffies 4294895280 (age 557.084s)
      hex dump (first 32 bytes):
        01 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00  ................
        00 00 00 00 00 00 00 00 00 00 00 00 49 2b ff ff  ............I+..
      backtrace:
        [<0000000088e71769>] slab_post_alloc_hook+0xb8/0x368
        [<00000000b528f67c>] kmem_cache_alloc+0x168/0x284
        [<000000008603f022>] damon_new_region+0x28/0x54
        [<00000000a3b8c64e>] damon_test_regions+0x38/0x270
        [<00000000559c4801>] kunit_try_run_case+0x50/0xac
        [<000000003932ed49>] kunit_generic_run_threadfn_adapter+0x20/0x2c
        [<000000003c3e9211>] kthread+0x124/0x130
        [<0000000028f85bdd>] ret_from_fork+0x10/0x20
    unreferenced object 0xffff2b49c5b20000 (size 56):
      comm "kunit_try_catch", pid 354, jiffies 4294895304 (age 556.988s)
      hex dump (first 32 bytes):
        03 00 00 00 00 00 00 00 07 00 00 00 00 00 00 00  ................
        00 00 00 00 00 00 00 00 96 00 00 00 49 2b ff ff  ............I+..
      backtrace:
        [<0000000088e71769>] slab_post_alloc_hook+0xb8/0x368
        [<00000000b528f67c>] kmem_cache_alloc+0x168/0x284
        [<000000008603f022>] damon_new_region+0x28/0x54
        [<00000000ca019f80>] damon_test_update_monitoring_result+0x18/0x34
        [<00000000559c4801>] kunit_try_run_case+0x50/0xac
        [<000000003932ed49>] kunit_generic_run_threadfn_adapter+0x20/0x2c
        [<000000003c3e9211>] kthread+0x124/0x130
        [<0000000028f85bdd>] ret_from_fork+0x10/0x20

Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests")
Fixes: f4c978b6594b ("mm/damon/core-test: add a test for damon_update_monitoring_results()")
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>
---
v3:
- Update the commit message to be more accurate.
- Add Reviewed-by.
v2:
- Replace the damon_del_region() with damon_destroy_region() rather than
  calling damon_free_region().
- Update the commit message.
---
 mm/damon/core-test.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
index 6cc8b245586d..28d24e698318 100644
--- a/mm/damon/core-test.h
+++ b/mm/damon/core-test.h
@@ -30,7 +30,7 @@ static void damon_test_regions(struct kunit *test)
 	damon_add_region(r, t);
 	KUNIT_EXPECT_EQ(test, 1u, damon_nr_regions(t));
 
-	damon_del_region(r, t);
+	damon_destroy_region(r, t);
 	KUNIT_EXPECT_EQ(test, 0u, damon_nr_regions(t));
 
 	damon_free_target(t);
@@ -316,6 +316,8 @@ static void damon_test_update_monitoring_result(struct kunit *test)
 	damon_update_monitoring_result(r, &old_attrs, &new_attrs);
 	KUNIT_EXPECT_EQ(test, r->nr_accesses, 150);
 	KUNIT_EXPECT_EQ(test, r->age, 20);
+
+	damon_free_region(r);
 }
 
 static void damon_test_set_attrs(struct kunit *test)
-- 
2.34.1